Regenerative medicine in urology.

Review

227

Regenerative Medicine in Urology Massimo Garriboli1

Anna Radford2

Jennifer Southgate2

1 Department of Paediatric Urology, Evelina Children’s Hospital, Guy’s

and St. Thomas NHS Foundation Trust, London, United Kingdom 2 Department of Biology, Jack Birch Unit of Molecular Carcinogenesis, University of York, York, United Kingdom

Address for correspondence Massimo Garriboli, MD, FEBPS, Department of Paediatric Urology, Evelina Children’s Hospital, Guy’s and St. Thomas NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, United Kingdom (e-mail: [email protected]).

Abstract

Keywords

► regenerative medicine ► tissue engineering ► stem cells ► urology

Regenerative medicine is an emerging field that is focused on the repair, replacement or regeneration of tissues and organs. It involves multiple disciplines dedicated to delivering different aspects of the regeneration process, including cell biology, material sciences and bioengineering. The development of tissue engineering strategies incorporating the use of autologous stem cells holds particular promise for overcoming insufficiencies from using cells from the patient’s own diseased tissues and providing solutions for treatment of many disorders of the genitourinary tract. Many experimental projects have successfully utilized stem cells and several pilot studies in humans indicate the potential of stem cell therapy. However, the discipline is still young and further knowledge of both materials and stem cell biology is required before this promise can be realized through clinical application. This review examines the principles related to regenerative medicine and bioengineering focusing on the stem cell isolation expansion and clinical application. Analysis of current achievements will be reviewed alongside the challenges that remain to be addressed in considering the present and future perspectives of regenerative medicine applied to urology.

Introduction The term “regenerative medicine” was used for the first time in 1999 by William Haseltine, Scientific Founder and the Chief Executive Officer of the Human Genome Science, to describe a new branch of medical science that applied the principles of engineering and life sciences toward the development of biological substitutes. The fundamental difference of regenerative medicine, over more traditional therapeutic strategies is that the aim is not just to halt an ongoing pathological process, but to restore or augment tissue or organ function.1 Such radical technologies include the use of biomaterials, cells, or both combined in tissue engineered constructs and may be applied to treat both congenital and acquired disease conditions. While the concept of culturing and engineering cells ex vivo to produce complex structures has been pursued for many years, the field has most recently benefited from advances in

received May 4, 2014 accepted May 5, 2014 published online June 11, 2014

the ability to isolate or generate and to expand progenitor cells in vitro. These progenitor or stem cells are important for regenerative medicine as, by definition, they carry the dual properties of self-renewal and differentiation capacity required for the formation of mature, functional tissues.2,3 Human embryonic stem cells (hESC) were first described in 19983 and the characterization of these pioneered the field. More recently, identification of cells with proliferative and differentiation potential from placenta and amniotic fluid has provided a promising nonembryonic source of multipotent cells.4 Stem cells have been used in the generation of tissue and organs such as the skin,5 the trachea,6 and vascular vessels.7 Many experimental projects have successfully utilized nonembryonic stem cells and several pilot studies in humans indicate the potential of stem cell therapy.8–10 However, there is yet no objective evidence that tissue-engineered approaches can achieve equal or superior outcomes compared with traditional therapies.

© 2014 Georg Thieme Verlag KG Stuttgart · New York

DOI http://dx.doi.org/ 10.1055/s-0034-1382259. ISSN 0939-7248.

This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.

Eur J Pediatr Surg 2014;24:227–236.

Regenerative Medicine in Urology

Garriboli et al.

Several feasibility studies have been performed to determine if the creation of a whole or part organ from either somatic or multipotent stem cells is possible. In urology, strategies aimed at replacing the absent, lost or damaged urethra, bladder, genital tissues or phallus have all been considered. Recent articles have postulated that by starting from decellularized renal acellular matrices, it is theoretically possible to construct structures resembling renal tubuli and glomerular-like structures and therefore potentially a whole kidney.11,12 However, any complex structural and functional organ such as bladder, bowel, and kidney still remains a major challenge and the translation from basic laboratory research into clinical practice awaits further significant collaborative investment.

Stem Cells The two main properties that characterize stem cells and make them an attractive source for tissue engineering are the ability to proliferate in an undifferentiated state (self-renewal) and the capacity to differentiate along one or more specialized cell lineages. The difference between somatic and stem cells is related to their plasticity; that is, the faculty to generate one or more differentiated cell types.13,14 Stem cells are classified according to their potency (the ability to generate committed cells). Cells that possess the potential to differentiate into all cell types are called “totipotent”; these are, for instance, cells derived from zygote that are able to differentiate not only into each of the three germ layers (endoderm, ectoderm, and mesoderm), but also into cells of the gonadal ridge and extraembryonic tissues. “Pluripotent” cells are reflective of the blastocyst (4—6 day embryo) and can differentiate into all three germ lines, but excluding extraembryonic cells. “Multipotent” cells are considered capable of differentiating only into cells belonging to the same germ layer. However, publications have called this property into question by suggesting the possibility that adipose-derived mesenchymal stem cells, human umbilical cord-derived mesenchymal stromal cells, and bone marrowderived mesenchymal stem cells can differentiate into cells with mesodermal,15 ectodermal (neural),16,17 and endodermal phenotypes.18,19 Finally, “unipotent” are cells with limited capacity for self-renewal that can differentiate into only one cell type. The human stem cells with the highest differentiation potential are hESCs. These may be sourced from the inner cell mass of the embryo during the blastocyst stage and can be expanded in vitro with or without feeder layers.20,21 The use of hESCs has been controversial because of ethical issues surrounding procurement. Since, 1998 when the generation of the first hESC was reported, various national committees have been formed with the aim of addressing the societal moral and ethical concerns related to the use of human embryos for research purposes. The United Kingdom (UK) has created one of the most clearly defined and structured stem cell policies in the world, with the origins of UK stem cell policy dating back to 1978 after the first in vitro fertilization (IVF) and the subsequent Warnock Report (1984). In 1990, the European Journal of Pediatric Surgery

Vol. 24

No. 3/2014

Human Fertilisation and Embryology (HFE) act created the Human Fertilisation and Embryology Authority (HFEA), with the responsibility to confer licenses for IVF and human embryonic research. The HFE act was updated in 2001 and 2008 to include hESC research and human–animal hybrid embryo research. As defined in the latest version of the HFE act, to be justified: “research is required to be necessary, or desirable and impossible by any other means.”22–24 In an effort to overcome potential ethical problems associated with hESCs and the possibility that donor cells could evoke an allergenic immune response, other potentially autologous cell sources (amniotic fluid, placenta, umbilical cord, and adult organs) have been investigated, along with other forms of stem cell production, including technologies such as parthenogenesis, cloning, somatic cell nuclear transfer, and somatic reprogramming. A major discovery in the stem cell field was achieved in 2006, when Takahashi and Yamanaka showed that induced pluripotent stem cells (iPS) could be obtained by transducing mouse embryonic and adult fibroblasts with a limited set of defined transcription factors.25 By this concept, iPS cells are produced by transforming adult somatic cells into an embryonic stem cell-like condition. Since this breakthrough, many research groups with similar or modified protocols have reported generating pluripotent stem cells from human tissues.26–29 Reprogrammed iPS cells are similar to hESCs in many of their characteristics, including morphology, proliferation potential, surface antigen profile, gene expression, and the ability to differentiate into cell types of all three germ layers both in vitro (embryoid bodies) and in vivo (teratomas). This most exciting differentiation potential is also one of the greatest hurdles to clinical use, with the need to harness differentiation to produce a useful product and to suppress tumorigenic potential.

Amniotic Fluid and Placental Stem Cells Alternative natural sources of stem cells are found in amniotic fluid and placenta. Early studies noted an interesting cellular composition of the amniotic fluid consisting of a heterogeneous cell population expressing markers from all three germ layers30–33; these are most probably derived from urine and pulmonary secretion of the fetus.34 The presence in amniotic fluid of cells with multipotential differentiation capacity was first described in 20074 and since then, the knowledge and characterization of amniotic fluid stem cells (AFSCs) has been expanded.35 Several properties make AFSCs an ideal source for isolating progenitor cells as they do not carry the problem of persistent pluripotency. AFSCs are easily obtained by amniocentesis or chorionic villous sampling procedures that are performed widely in prenatal diagnoses or from the placenta at the time of birth, thus overcoming most ethical concerns. AFSCs expand extensively in vitro, with a population doubling time of 36 hours.4 Lines can double more than 200 times, maintaining long telomeres, a normal karyotype, as well as expression of embryonic markers such as Oct-4A, SSEA-4, CD90, CD105, and CD117.4,36 The lack of need for


228

feeder cell layers avoids some of the risk connected with exposure to xenobiotic viruses, although most culture media still rely on bovine serum. A major advantage of AFSC is that unlike hESC they do not form tumors in vivo, although this does raise questions about their true potency. Amniotic fluid-derived mesenchymal stem cells (MSCs) have found potential application in allograft transplantation. Immunophenotypic analyses have demonstrated that MSCs express HLA-ABC (class I major complex MHC-I), but that they do not show constitutive expression of HLA-DR, -DP, -DQ (MHC-II molecules). Mononucleated cells recovered from placentas by density gradient fractionation could suppress the proliferation of umbilical cord blood (UCB) lymphocytes induced by cellular or nonspecific mitogenic stimuli. As it is possible to obtain placenta and UCB from the same donor, these analyses have been used to suggest that placental MSCs cotransplanted in conjunction with UCB-derived hematopoietic stem cells could potentially reduce the risk of graftversus-host disease in recipients.33 However, it should be noted that this does not necessarily mean that such cells will be immunopriviledged.37,38 In’t Anker and colleagues first indicated that both amniotic fluid and placenta were potentially abundant sources of maternal and fetal MSCs, with both exhibiting a phenotype and multilineage differentiation potential similar or higher to that of adult bone marrow-derived MSCs.39–42 Several studies describing protocols for isolating MSCs from the amniotic fluid have been published.43–45 These cells have been shown to possess true multipotency, being able to proliferate in vitro, to be engineered into three-dimensional structures, and to be used in vivo to repair tissue defects: limiting damage and promoting tissue regeneration in acute and chronic disease models.43,46,47

Engineering of Complex Tissues Tissue engineering combines cell transplantation with biomaterials and bioengineering principles with the aim of developing a transplantable biological replacement that can substitute for normal tissue and function. Lack of autologous tissue available for reconstructive surgery is one of the most important reasons to have prompted scientists to look for new sources of tissue.

Scaffolds and Matrices Scaffolds and matrices require particular characteristics pertaining to biocompatibility, biodegradability, and minimal or absent immunogenicity to avoid provoking an unwanted inflammatory or rejection response, which might otherwise interfere with tissue integration. Thus, the degradation rate and the concentration of degradation products must be controlled in a manner that obviates the risk of toxicity. An ideal scaffold should also provide a suitable environment to promote such cell interactions as required for normal tissue regenerative and repair processes to occur in vivo. Different types of biomaterial scaffold have been described for clinical applications, which can be divided into two

Garriboli et al.

groups: synthetic and natural-derived extracellular matrix (ECM). The first group includes silicone, polyurethane, and biodegradable polymers such as poly(glycolic acid) (PGA), polylactide, poly(glycolide-co-lactide), poly(caprolactone), poly(glycolide-co-ε-caprolactone), while the latter includes ECM scaffolds derived from collagen, alginate, and laminin or those that are obtained following decellularization of tissues, including small intestine, bladder, pericardium, and dermis. These tissues are decellularized using physical, enzymatic or chemical methods to just leave the ECM.48 Both synthetic and natural matrices have advantages and disadvantages: the first group has the advantage of being available “off the shelf” and to be highly reproducible. The second group maintains the characteristics of the original tissue or organ, including a 3D structure that represents the ideal environment for organ-specific cell-matrix interaction and cellular repopulation, albeit with intrinsic variation.49 Naturally derived scaffolds may sequester bioactive factors to regulate cell activity and mimic the microenvironment provided by the ECM.50 The failure of some initial experiments using acellular scaffolds51,52 has led to a focus on generating natural or synthetic scaffolds incorporating in vitro–seeded cells. Autologous donor cells represent the preferred choice because of the negated risk of rejection and associated complications of immunosuppression related to the use of cells from other sources.53–55 Cells, expanded in vitro, can be implanted via direct injection or by sowing or combining them with a matrix or scaffold to provide a delivery vehicle that may be used to achieve cell provision with high loading and efficiency to specific sites in the body.56 The approach consists of combining cultured cells (for bladder reconstruction, typically of urothelial and smooth muscle derivation) and scaffold. To survive on the scaffold, cells need an adequate metabolic and nutrient environment that promotes tissue development. “Natural” in vivo bioreactors, such as the omentum, were initially utilized,57 but other bioreactors have been created and used in more recent reports.58

Regenerative Medicine Applied to Urology Stem cells have been utilized for the treatment of various renal and urological diseases such as urinary incontinence,59 vesicoureteric reflux,9 acute and chronic renal injury.60

Urinary Incontinence Periurethral or transurethral injection of bulking agents is a minimally invasive surgical procedure that represents one option for stress urinary incontinence. A recent Cochrane review, however, failed to find sufficient evidence to support this practice.61 The use of autologous stem cells instead of inert bulky molecules has been explored as an alternative. In 2005 Jack et al injected labeled hMSCs obtained from lipoaspirate cells into the urethra and bladder wall of eight athymic rats and demonstrated that these cells integrate into the tissue acquiring morphological and biochemical characteristics of smooth muscle.62 European Journal of Pediatric Surgery

Vol. 24

No. 3/2014

229




Garriboli et al.

Since this, various groups have reported, both in animal models and in man, significant results in the treatment of stress urinary incontinence, through intraurethral submucosal injection of MSCs (fibroblasts and myoblasts).63–65 Sè be et al published a series of 12 women with previous failed surgical management of stress incontinence and reported autologous myoblast injection to be a safe and promising second-line therapy.66 A further study has recently been published of 33 patients treated with injection of autologous muscle-derived cells in different doses. At 12 months followup, eight of nine (88.9%) patients treated with the high-dose injection experienced a 50% or greater reduction in incontinence pad weight and had 0 to 1 leaks during 3 days while seven of nine (77.8%) had a 50% or greater reduction reported, with no major treatment-related adverse events reported.67 Most recent advances include the use of autologous injection into the extrinsic urethral sphincter to treat stress urinary incontinence.68 This publication reported the results of a series of 38 women (median age 50 years) in whom an upper arm biopsy was taken to obtain myoblasts, which were then injected using transurethral ultrasound guidance into the extrinsic urethral sphincter. After 6 months an improvement in terms of symptoms and quality of life seem to appear. However, the limited follow-up period for assessment of potential complications and efficacy, coupled with a lack of supportive evidence for the integration of these cells into the sphincteric complex being responsible for any amelioration, leaves some unanswered questions. Such apparently promising results suggest that the approach of cellular-based therapy for stress urinary incontinence may be considered for clinical application; however, an evidence-based assessment of the long-term efficiency and safety of the treatment is required through properly designed randomized controlled trials. In particular, it needs to be determined whether apparent success is really due to a development of a functional tissue rather than a simply bulky effect secondary to an encapsulation (rejection) response.

Urethral Reconstruction Bioengineering of the urethra has been attempted experimentally utilizing synthetic polymers69 and acellular matrices.70–72 Partial or total penile urethra replacement was performed in dog and rabbit models using biomaterials alone or seeded with autologous cells.73–76 The use of an unseeded scaffold was shown to be unsuccessful for large defects due to contraction or stenosis of the matrix, with epithelial ingrowth into a decellularized tubularized matrix observed in rabbit only where the length of the graft did not exceed 0.5 cm.77 Different groups have utilized scaffolds and cells from different sources such as bone marrow MSC,78 foreskin,72 oral mucosa,79 lingual keratinocytes80 and mesothelial cells from omentum.81 Fu et al used epithelial cells harvested from the foreskin of rabbits seeded onto a bladder submucosa scaffold. Follow-up examination at 6 months postprocedure showed persistence of epithelium of epidermal origin and improved regeneration in animals with seeded grafts versus unseeded grafts.72 A further study from the same institution European Journal of Pediatric Surgery

Vol. 24

No. 3/2014

reported similar results with the use of keratinocytes harvested from oral mucosa.82 Mikami et al79 created and transplanted in dogs a two-layer tissue engineered urethra using cells from oral punch biopsy and combining them with a collagen mesh matrix seeded with skeletal muscle-derived cells. Feng et al80 used porcine acellular corpus spongiosum matrices with autologous corporal smooth muscle cells (SMCs) and lingual keratinocytes. In all of the above studies the results are reported as excellent with the group of animals that have received the reconstruction with seeded grafts maintaining a patent urethra compared with the controls, but the results are limited to short term periods only (12 weeks and 6 months). One of the causes of failure in urethral surgery is the formation of a urethral scar that results in stricture. To obviate this problem Li et al83 used transforming growth factor beta 1 (TGF-β1) small interfering RNA (siRNA) transfected fibroblasts seeded together with oral keratinocytes onto a bladder submucosa acellular matrix. Their hypothesis was that TGFβ1 siRNA could reduce the secretion of type I collagen and the scar formation through the inhibition of the expression of TGF-β1. The results obtained in their rabbit model demonstrated that at 6 months the reconstructed urethras had minimal presence of inflammatory cells; moreover, they noticed formation of capillaries below the lower epithelial layer. This latter finding was not demonstrable in either control groups; unseeded bladder acellular matrix graft (BAMG) or with BAMG with oral keratinocytes that were not transfected. The “self-assembly technique,” as first described by Auger et al,84 is an alternative approach that aims to create a totally autologous graft. The principle of the technique is to generate an autologous ECM produced by dermal fibroblast cultures supplemented in ascorbic acid and to superimpose several sheets of that matrix to obtain a construct with sufficient mechanical properties to be manipulated. Generating an autologous ECM aims to overcome the immunological response that can be associated with the use of heterologous scaffolds and, consequently, reducing inflammatory and fibrotic reactions. This method was utilized by Auger and coworkers to reproduce the skin for the treatment of severe burn patients,84 successively modified to create blood vessels,85 and finally adapted for the reconstruction of the urethra. The idea is interesting but the technique is elaborate and the data very preliminary.86,87 Reports of clinical translation of tissue engineering strategies in the urethra only exist in a small number of pilot studies and they have been associated with major complications. Three out of six patients aged 14 to 44 months treated by Fossum et al using tissue-engineered urothelium for the surgical correction of severe hypospadias developed complications such as urethrocutaneous fistula and stricture.88 A poor outcome was also reported by Bhargava et al.89 They corrected lichen sclerosis-related urethral strictures in five patients with one-stage (n ¼ 2) and two-stages (n ¼ 3) autologous tissue-engineered buccal skin urethroplasty. By 37 months, two patients required partial or total excision of the grafted urethra due to fibrosis and the remaining three


230

patients underwent further treatment of the reconstructed urethra. In 2011 Raya-Rivera et al combined autologous cells in an engineered scaffold and implanted them into five boys with urethral defects. They took a bladder biopsy for culturing smooth muscle and urothelial cells and after in vitro expansion for 3 to 6 weeks, the urothelial cells were seeded onto the luminal surface and muscle cells onto the outer surface of a tubular scaffold. The tubularized engineered urethral constructs were then implanted surgically with absorbable sutures. The patients were followed up with urine analyses, cystourethroscopy, cystourethrography, and flow measurements up to 71 months (four patients) with one patient at 36 months. The authors reported all patients continent with reconstructed urethras that maintained a wide calibre without evidence of strictures. One patient developed a narrowing at the proximal superior graft anastomotic site that needed a transurethral incision 4 weeks after surgery and another one required a pubovesical sling after the surgery to correct daytime stress incontinence secondary to postoperative sphincteric incompetence.90 This latest study seems to be the most promising, but additional studies are required before considering tissue-engineered urethras as a valid approach for reconstruction. Despite encouraging results obtained experimentally, the application of tissue engineering for urethral reconstruction still appears to have a marginal role in future urological practice. Contributing to this discordance is the relatively small number of cases encountered in which current conventional treatment is inadequate. Examples include very severe pelvic trauma with extensive urethral damage, or patients with history of multiple urethral surgeries with failure of skin and/or buccal mucosa graft.

Phallus Reconstruction Reconstruction or substitution of the corpora cavernosa to restore a cosmetically acceptable phallus that would allow normal reproductive, sexual, and urinary function represents a very challenging task. Indications for penile reconstruction are rare including penile malignancy, traumas, gender reassignment surgery and congenital anomalies. Tissue engineering of penile structures is difficult because of the unique characteristics required for adequate erectile function.91,92 At present, penile reconstructive surgery is performed using autologous tissue in the form of microsurgical and free tissue transfer techniques, for example, radial forearm or fibula flaps. To facilitate erection of the neophallus either the use of semirigid or inflatable alloplastic penile implants or of autologous bone as an osteocutaneous flap93,94 may be considered. Only a few experimental studies have been published to date. Initial investigation into the possible culture of human corporal SMCs combined with a polymer to generate a bioengineered corpus cavernosum has been reported.95,96 Following these initial experiments, the same group used naturally derived acellular corporal tissue matrices in a rabbit model. This concept utilized expanded human corpus cavernosum muscular and endothelial cells seeded onto acellular

Garriboli et al.

matrices derived from donor rabbit corpora. The authors replaced an entire cross-sectional segment of the rabbit corporal bodies with cell-seeded matrices and reported that the engineered corpora cavernosa achieved adequate structural and functional parameters.97–100 A further group seeded acellular corporal collagen matrices with SMCs derived from human umbilical arteries and implanted the cellularized implants into athymic mice. These authors reported that the scaffolds became cellularized to develop tissue with anatomical and functional properties similar to corporus cavernosum smooth muscle.101 Another interesting approach has been described by Zhang and his group: they first created a tissue-engineered corpus cavernosum seeded with muscle-derived stem cells, then described an experiment in which they transduced, via a lentivirus, the muscle-derived stem cells with vascular endothelial growth factor (VEGF) and demonstrated that after the in vivo implant, the obtained construct showed increased content of endothelial cells, SMCs, and capillaries.102,103 Although the approach needs to be validated in terms of efficacy and safety considerations, the potential to enhance the secretion of growth factors, in particular VEGF to boost angiogenic responses, could lead the way to long-term, successful organ engineering by improving the initial integration and viability of implanted tissue-engineered constructs.

Testicular Function Replacement Patients with testicular dysfunction requiring androgen replacement have provided another potential application of bioengineering within the field of urology. Classically, treatment is exogenous administration of chemically modified testosterone. However, in the long term, this treatment is associated with complications such as excessive erythropoiesis and bone density changes. An initial attempt to overcome the problem was investigated by injecting doses of Leydig cells, the principal source of testosterone, microencapsulated in alginate-poly-L-lysine into castrated animals. Serial testosterone assays demonstrated that the animals were able to maintain testosterone levels long term.100 Other work in athymic mice with bilateral anorchia produced promising results by implanting testicular prostheses created in bioreactors with chondrocytes and loaded with testosterone. The long-term results again showed maintenance of testosterone within a physiological range.104

Bladder Reconstruction The bladder has always been a challenging organ to replicate because of the need for compliance to maintain a urinestoring, low pressure vessel during the filling-voiding cycle. The peculiar capacity of the bladder to expand during the filling phase and to contract during voiding is secondary to the compliant muscular wall. In addition, the highly specialized vesicular lining, the urothelium provides a watertight, but electrolyte-modifying barrier.105 These two layers of tissue are connected and intimately joined by the ECM of the lamina propria. European Journal of Pediatric Surgery

Vol. 24

No. 3/2014

231




Garriboli et al.

In end-stage disease, the bladder becomes small, fibrotic, and contracted with a markedly reduced capacity, incontinence and leading to poor quality of life. To ameliorate these issues and to decrease pressure on the upper urinary tract, the bladder may be augmented surgically. One of the most frequently performed procedures is “enterocystoplasty” during which a segment of bowel, complete with vascular pedicle, is reconfigured to increase bladder size. Enterocystoplasty can be associated with complications, including metabolic acidosis, electrolyte imbalance, infection, stone formation, and a long-term risk of cancer.106 The complications are primarily due to the fact that bowel mucosa is structurally and physiologically incompatible with the longterm exposure to urine. An ideal tissue engineered urinary bladder should reproduce the function of the urinary barrier and the compliance of the smooth muscle. In the past, both synthetic and organic materials have been used with the aim to build a vesicular scaffold, starting with the attempt to use a free tissue graft (fascia) to augment bladders in dogs reported by Neuhof in 1917.107 Many other materials have since been used both experimentally and clinically, including small intestinal submucosa, pericardium, dura, and placenta. Use of cell-free collagen matrices and synthetic materials has been explored but most have failed because of mechanical, structural, functional, or biocompatibility reasons. Good results were obtained in experimental substitution of small part of the bladder wall with SIS51,108 however; those results were not confirmed in successive works109 including a clinical series.110 One of the reported problems reported was graft contraction, which is associated with an extensive fibrotic “scarring” reaction and incomplete tissue layer formation.111 An innovation introduced by bioengineering was the use of a scaffold seeded with urothelial (and muscle) cells previously expanded in vitro. Bladder cells can be derived from biopsies54 or reportedly from urine112 or stem cells.113 To be maintained on a scaffold, cells require an appropriate metabolic and nutritional environment, which may be facilitated by the use of a bioreactor.114 Interestingly, to stimulate the development and maintenance of capacity and compliance of the construct, some authors advocate the importance of postoperative early exposure of site-appropriate mechanical loading (i.e., bladder filling).115 After a satisfactory preliminary experimental study in dogs, in which the authors reported an average bladder capacity of 95% of the original precystectomy volume52 the technique was applied into a clinical setting.116 In 2006, Atala et al reported a pilot study on seven of nine patients treated with bladder reconstruction using a scaffold seeded with autologous cells obtained from a bladder biopsy. Although the authors commented that the urodynamic results “were similar to those that would be expected with the use of gastrointestinal tissue” the results of the study showed only modest increase in bladder capacity and it is questionable whether the results were truly satisfactory. Difficulties in interpreting the results are also encountered due to the protocol being changed during the study as the procedure was evolved. The final three patients had an augmentation European Journal of Pediatric Surgery

Vol. 24

No. 3/2014

performed that utilized a combined PGA-collagen scaffold seeded with cells and an omentum wrap. The omentum was introduced to improve angiogenesis and the development of vascularity within the graft. In fact, those patients showed the best functional outcome in terms of decreased end-filling pressures, increased capacities, and compliance.116 Further patients have been treated in a phase II study and these results have been recently published. The prospective study has been performed in children with neurogenic bladder due to spina bifida, but again the reported results were not positive.117 Urothelial and SMCs obtained from bladder biopsy were grown ex vivo and seeded onto a biodegradable scaffold to form a regenerative augment as the foundation for bladder tissue regeneration. The patients were followed up at 12 to 36 months, with the results showing that bladder compliance and capacity did not improve. Moreover, the authors reported adverse events in all patients (in some cases serious events such as bowel obstruction and/or bladder rupture) that made them to conclude that they had surpassed an acceptable safety standard. A possible reason for the failure of the latter study, not considering the adverse events reported, could be related to the poor quality of urothelial cells derived from neurogenic bladders, as demonstrated by Subramaniam et al.118 A different approach called “composite cystoplasty” has been proposed by Thomas et al.119 This approach has the advantage over a fully tissue-engineered approach in that the in vitro component of the procedure is confined to propagation of a single, regenerative cell type. In this case, a host vascularized, innervated and functional surrogate smooth muscle tissue, such as intestine, is incorporated into the neobladder and the surrogate epithelium is replaced with an in vitro-generated autologous bladder urothelium, which is better suited to function as a urinary barrier then the original intestinal epithelium.120,121 In support of this approach, urothelial cells isolated from surgical specimens have been shown to be highly proliferative and acquire unipotential “stem-like” properties in vitro.122 However, as shown by Subramaniam et al118 and discussed above, urothelial cells isolated from patients’ bladders requiring reconstruction may be compromised by the disease or the disease environment and hence an alternative source of cells may be required. To overcome this problem, various authors have tried to differentiate embryonic and adult stem cell toward a tissuespecific urothelial cell outcome using a variety of methods, including in vitro coculture and conditioned medium (CM) from urothelial cell cultures. It is however worth pointing out that there is no biological evidence that postnatal urothelial cells can produce specific lineage-determining factors, leaving any scientific justification in support of this approach as weak. Oottamasathien et al113 and Tian et al123 reported that both embryonic stem cells and bone marrow mesenchymal stem cells could be differentiated toward urothelium using CM or an indirect Transwell (R) system (Corning Incorporated, Life Sciences, Acton, Massachusetts, United States). With the same coculture approach, cultures of urothelial phenotype were reported from human adipose-derived stromal cells by


232


Conclusions Tissue engineering represents a promising and attractive option for reconstruction of damaged or lost tissues and organs in the urogenital tract. This is a research area of intense activity and many preclinical and animal studies are showing promising results. However, only relatively few clinical studies have been performed and contrasting results highlight that this discipline is still young and requires further fundamental knowledge that can be translated into practical, clinical solutions. The potential for using autologous stem cells is enticing as it could overcome insufficiencies from using cells from a patient’s own diseased tissues. However, even though sources of natural or induced pluripotent or multipotent stem cells that can be used autologously have been identified, there remain significant challenges. If their potential can be harnessed, stem cells promise an important role for reconstruction in patients affected by diseases that compromise the intrinsic quality of cells in tissues and organs, including ageacquired diseases such as cancer. However, the challenge remains to direct stem cell differentiation to the formation of functional tissues and to restrain all further potentiality once there.

5 Marino D, Luginbühl J, Scola S, Meuli M, Reichmann E. Bioengi-

6

7 8

9

10

11 12

13

14

15

16

17

18 19

20

21

22 23

References 1 Hasetine W. A brave new medicine. A conversation with William

Haseltine. Interview by Joe Flower. Health Forum J 1999;42(4): 28–30, 61–65 2 Martin GR. Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells. Proc Natl Acad Sci U S A 1981;78(12):7634–7638 3 Thomson JA, Itskovitz-Eldor J, Shapiro SS, et al. Embryonic stem cell lines derived from human blastocysts. Science 1998; 282(5391):1145–1147 4 De Coppi P, Bartsch G Jr, Siddiqui MM, et al. Isolation of amniotic stem cell lines with potential for therapy. Nat Biotechnol 2007; 25(1):100–106

233

24

25

26

27

neering dermo-epidermal skin grafts with blood and lymphatic capillaries. Sci Transl Med 2014;6(221):21ra14 Baiguera S, Jungebluth P, Burns A, et al. Tissue engineered human tracheas for in vivo implantation. Biomaterials 2010;31(34): 8931–8938 Niu G, Sapoznik E, Soker S. Bioengineered blood vessels. Expert Opin Biol Ther 2014;14(4):403–410 Thaker H, Sharma AK. Regenerative medicine based applications to combat stress urinary incontinence. World J Stem Cells 2013; 5(4):112–123 Atala A, Cima LG, Kim W, et al. Injectable alginate seeded with chondrocytes as a potential treatment for vesicoureteral reflux. J Urol 1993;150(2 Pt 2):745–747 Elliott MJ, De Coppi P, Speggiorin S, et al. Stem-cell-based, tissue engineered tracheal replacement in a child: a 2-year follow-up study. Lancet 2012;380(9846):994–1000 Wezel F, Southgate J, Thomas DF. Regenerative medicine in urology. BJU Int 2011;108(7):1046–1065 Atala A. Tissue engineering for the replacement of organ function in the genitourinary system. Am J Transplant 2004;4 (Suppl 6):58–73 Reubinoff BE, Pera MF, Fong CY, Trounson A, Bongso A. Embryonic stem cell lines from human blastocysts: somatic differentiation in vitro. Nat Biotechnol 2000;18(4):399–404 Reubinoff BE, Itsykson P, Turetsky T, et al. Neural progenitors from human embryonic stem cells. Nat Biotechnol 2001;19(12): 1134–1140 Muraki K, Hirose M, Kotobuki N, et al. Assessment of viability and osteogenic ability of human mesenchymal stem cells after being stored in suspension for clinical transplantation. Tissue Eng 2006; 12(6):1711–1719 Matsuse D, Kitada M, Kohama M, et al. Human umbilical cordderived mesenchymal stromal cells differentiate into functional Schwann cells that sustain peripheral nerve regeneration. J Neuropathol Exp Neurol 2010;69(9):973–985 Hou SY, Zhang HY, Quan DP, Liu XL, Zhu JK. Tissue-engineered peripheral nerve grafting by differentiated bone marrow stromal cells. Neuroscience 2006;140(1):101–110 Anderson DJ, Gage FH, Weissman IL. Can stem cells cross lineage boundaries? Nat Med 2001;7(4):393–395 Forbes SJ, Vig P, Poulsom R, Wright NA, Alison MR. Adult stem cell plasticity: new pathways of tissue regeneration become visible. Clin Sci (Lond) 2002;103(4):355–369 Richards M, Fong CY, Chan WK, Wong PC, Bongso A. Human feeders support prolonged undifferentiated growth of human inner cell masses and embryonic stem cells. Nat Biotechnol 2002; 20(9):933–936 Amit M, Shariki C, Margulets V, Itskovitz-Eldor J. Feeder layer- and serum-free culture of human embryonic stem cells. Biol Reprod 2004;70(3):837–845 Alghrani A. The Human Fertilisation and Embryology Act 2008: a missed opportunity? J Med Ethics 2009;35(12):718–719 Matthews KR, Rowland ML. Stem cell policy in the Obama age: UK and US perspectives. Regen Med 2011;6(1):125–132 Bahadur G, Iqbal M, Malik S, Sanyal A, Wafa R, Noble R. Admixed human embryos and stem cells: legislative, ethical and scientific advances. Reprod Biomed Online 2008;17(Suppl 1):25–32 Takahashi K, Yamanaka S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell 2006;126(4):663–676 Takahashi K, Tanabe K, Ohnuki M, et al. Induction of pluripotent stem cells from adult human fibroblasts by defined factors. Cell 2007;131(5):861–872 Meissner A, Wernig M, Jaenisch R. Direct reprogramming of genetically unmodified fibroblasts into pluripotent stem cells. Nat Biotechnol 2007;25(10):1177–1181

European Journal of Pediatric Surgery

Vol. 24

No. 3/2014


various authors.124–126 Hair follicle stem cells have also been investigated as a possible new cell source in bladder regeneration.127 The use of human endometrial stem cells, seeded onto an electrospun matrix, has also been reported.128 Unfortunately, most studies have been limited to demonstrating expression of urothelium-specific markers only at the transcript level and without specificity controls to ensure the absence of other cell types, leaving a degree of uncertainty as to the specific phenotype of the differentiated cultures. As yet, none of these approaches has met proof of concept by demonstrating development of a transplantable fully differentiated and functional urothelium.129 Multipotent stem cells are potentially good candidates for becoming the source of cells for in vitro urinary bladder construction, but the exact culture conditions required to direct autologous multipotent stem cells into urothelial or other bladder-derived tissues are yet to be established, and pose a significant challenge to researchers.

Garriboli et al.


Garriboli et al.

28 Park IH, Zhao R, West JA, et al. Reprogramming of human somatic

29

30 31

32

33

34 35

36

37

38

39

40

41

42

43

44

45

46

47

48 49

cells to pluripotency with defined factors. Nature 2008; 451(7175):141–146 Scheper W, Copray S. The molecular mechanism of induced pluripotency: a two-stage switch. Stem Cell Rev 2009;5(3): 204–223 Sarkar S, Chang HC, Porreco RP, Jones OW. Neural origin of cells in amniotic fluid. Am J Obstet Gynecol 1980;136(1):67–72 Cousineau J, Potier M, Dallaire L, Melançon SB. Separation of amniotic fluid cell types in primary culture by Percoll density gradient centrifugation. Prenat Diagn 1982;2(4):241–249 Medina-Gómez P, Johnston TH. Cell morphology in long-term cultures of normal and abnormal amniotic fluids. Hum Genet 1982;60(4):310–313 von Koskull H, Aula P, Trejdosiewicz LK, Virtanen I. Identification of cells from fetal bladder epithelium in human amniotic fluid. Hum Genet 1984;65(3):262–267 Underwood MA, Gilbert WM, Sherman MP. Amniotic fluid: not just fetal urine anymore. J Perinatol 2005;25(5):341–348 Miki T, Marongiu F, Dorko K, Ellis EC, Strom SC. Isolation of amniotic epithelial stem cells. Curr Protoc Stem Cell Biol 2010; 12:1E.3.1–1E.3.10 Cananzi M, De Coppi P. CD117(þ) amniotic fluid stem cells: state of the art and future perspectives. Organogenesis 2012;8(3): 77–88 Mukonoweshuro B, Brown CJ, Fisher J, Ingham E. Immunogenicity of undifferentiated and differentiated allogeneic mouse mesenchymal stem cells. J Tissue Eng 2014;5:2041731414534255 Tee JY, Vaghjiani V, Liu YH, Murthi P, Chan J, Manuelpillai U. Immunogenicity and immunomodulatory properties of hepatocyte-like cells derived from human amniotic epithelial cells. Curr Stem Cell Res Ther 2013;8(1):91–99 In ’t Anker PS, Scherjon SA, Kleijburg-van der Keur C, et al. Amniotic fluid as a novel source of mesenchymal stem cells for therapeutic transplantation. Blood 2003;102(4):1548–1549 Yan ZJ, Hu YQ, Zhang HT, et al. Comparison of the neural differentiation potential of human mesenchymal stem cells from amniotic fluid and adult bone marrow. Cell Mol Neurobiol 2013;33(4):465–475 De Coppi P, Callegari A, Chiavegato A, et al. Amniotic fluid and bone marrow derived mesenchymal stem cells can be converted to smooth muscle cells in the cryo-injured rat bladder and prevent compensatory hypertrophy of surviving smooth muscle cells. J Urol 2007;177(1):369–376 Ghionzoli M, Repele A, Sartiani L, et al. Human amniotic fluid stem cell differentiation along smooth muscle lineage. FASEB J 2013;27(12):4853–4865 Kaviani A, Perry TE, Dzakovic A, Jennings RW, Ziegler MM, Fauza DO. The amniotic fluid as a source of cells for fetal tissue engineering. J Pediatr Surg 2001;36(11):1662–1665 Kaviani A, Guleserian K, Perry TE, Jennings RW, Ziegler MM, Fauza DO. Fetal tissue engineering from amniotic fluid. J Am Coll Surg 2003;196(4):592–597 Pozzobon M, Piccoli M, De Coppi P. Stem cells from fetal membranes and amniotic fluid: markers for cell isolation and therapy. Cell Tissue Bank 2014 Perin L, Sedrakyan S, Giuliani S, et al. Protective effect of human amniotic fluid stem cells in an immunodeficient mouse model of acute tubular necrosis. PLoS ONE 2010;5(2):e9357 Zani A, Cananzi M, Fascetti-Leon F, et al. Amniotic fluid stem cells improve survival and enhance repair of damaged intestine in necrotising enterocolitis via a COX-2 dependent mechanism. Gut 2014;63(2):300–309 Atala A. Engineering organs. Curr Opin Biotechnol 2009;20(5): 575–592 Korossis S, Bolland F, Southgate J, Ingham E, Fisher J. Regional biomechanical and histological characterisation of the passive


Vol. 24

No. 3/2014

50

51

52

53

54

55 56

57

58

59

60

61

62

63

64

65

66

67

68

porcine urinary bladder: Implications for augmentation and tissue engineering strategies. Biomaterials 2009;30(2):266–275 Bullers S, Baker S, Ingham E, Southgate J. The human tissue: biomaterial interface: a role for PPARγ-dependent glucocorticoid receptor activation in regulating the CD163þ M2 macrophage phenotype. Tissue Eng Part A 2014 Zhang Y, Frimberger D, Cheng EY, Lin HK, Kropp BP. Challenges in a larger bladder replacement with cell-seeded and unseeded small intestinal submucosa grafts in a subtotal cystectomy model. BJU Int 2006;98(5):1100–1105 Oberpenning F, Meng J, Yoo JJ, Atala A. De novo reconstitution of a functional mammalian urinary bladder by tissue engineering. Nat Biotechnol 1999;17(2):149–155 Turner AM, Subramaniam R, Thomas DF, Southgate J. Generation of a functional, differentiated porcine urothelial tissue in vitro. Eur Urol 2008;54(6):1423–1432 Cilento BG, Freeman MR, Schneck FX, Retik AB, Atala A. Phenotypic and cytogenetic characterization of human bladder urothelia expanded in vitro. J Urol 1994;152(2 Pt 2):665–670 Puthenveettil JA, Burger MS, Reznikoff CA. Replicative senescence in human uroepithelial cells. Adv Exp Med Biol 1999;462:83–91 Sharma AK, Hota PV, Matoka DJ, et al. Urinary bladder smooth muscle regeneration utilizing bone marrow derived mesenchymal stem cell seeded elastomeric poly(1,8-octanediol-co-citrate) based thin films. Biomaterials 2010;31(24):6207–6217 Baumert H, Simon P, Hekmati M, et al. Development of a seeded scaffold in the great omentum: feasibility of an in vivo bioreactor for bladder tissue engineering. Eur Urol 2007;52(3):884–890 Davis NF, Mooney R, Piterina AV, et al. Construction and evaluation of urinary bladder bioreactor for urologic tissue-engineering purposes. Urology 2011;78(4):954–960 Mitterberger M, Pinggera GM, Marksteiner R, et al. Adult stem cell therapy of female stress urinary incontinence. Eur Urol 2008; 53(1):169–175 Murray P, Camussi G, Davies JA, et al. The KIDSTEM European Research Training Network: Developing a Stem Cell Based Therapy to Replace Nephrons Lost through Reflux Nephropathy. Organogenesis 2007;3(1):2–5 Kirchin V, Page T, Keegan PE, Atiemo K, Cody JD, McClinton S. Urethral injection therapy for urinary incontinence in women. Cochrane Database Syst Rev 2012;2:CD003881 Jack GS, Almeida FG, Zhang R, Alfonso ZC, Zuk PA, Rodríguez LV. Processed lipoaspirate cells for tissue engineering of the lower urinary tract: implications for the treatment of stress urinary incontinence and bladder reconstruction. J Urol 2005;174(5): 2041–2045 Strasser H, Marksteiner R, Margreiter E, et al. Transurethral ultrasonography-guided injection of adult autologous stem cells versus transurethral endoscopic injection of collagen in treatment of urinary incontinence. World J Urol 2007;25(4):385–392 Kim SO, Na HS, Kwon D, Joo SY, Kim HS, Ahn Y. Bone-marrowderived mesenchymal stem cell transplantation enhances closing pressure and leak point pressure in a female urinary incontinence rat model. Urol Int 2011;86(1):110–116 Shi LB, Cai HX, Chen LK, et al. Tissue engineered bulking agent with adipose-derived stem cells and silk fibroin microspheres for the treatment of intrinsic urethral sphincter deficiency. Biomaterials 2014;35(5):1519–1530 Sèbe P, Doucet C, Cornu JN, et al. Intrasphincteric injections of autologous muscular cells in women with refractory stress urinary incontinence: a prospective study. Int Urogynecol J 2011;22(2):183–189 Carr LK, Robert M, Kultgen PL, et al. Autologous muscle derived cell therapy for stress urinary incontinence: a prospective, dose ranging study. J Urol 2013;189(2):595–601 Blaganje M, Lukanović A. Ultrasound-guided autologous myoblast injections into the extrinsic urethral sphincter: tissue


234


70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

235

89 Bhargava S, Patterson JM, Inman RD, MacNeil S, Chapple CR.

90

91 92

93 94 95

96

97

98

99

100 101

102

103

104

105 106

107 108

109

110

111

Tissue-engineered buccal mucosa urethroplasty-clinical outcomes. Eur Urol 2008;53(6):1263–1269 Raya-Rivera A, Esquiliano DR, Yoo JJ, Lopez-Bayghen E, Soker S, Atala A. Tissue-engineered autologous urethras for patients who need reconstruction: an observational study. Lancet 2011; 377(9772):1175–1182 Melman A, Gingell JC. The epidemiology and pathophysiology of erectile dysfunction. J Urol 1999;161(1):5–11 Schultheiss D. Regenerative medicine in andrology: Tissue engineering and gene therapy as potential treatment options for penile deformations and erectile dysfunction. Eur Urol 2004; 46(2):162–169 Ninković M, Dabernig W. Flap technology for reconstructions of urogenital organs. Curr Opin Urol 2003;13(6):483–488 Sievert KD. Vaginal and penile reconstruction. Curr Opin Urol 2003;13(6):489–494 Kershen RT, Yoo JJ, Moreland RB, Krane RJ, Atala A. Reconstitution of human corpus cavernosum smooth muscle in vitro and in vivo. Tissue Eng 2002;8(3):515–524 Pilatz A, Schultheiss D, Gabouev AI, et al. Isolation of primary endothelial and stromal cell cultures of the corpus cavernosum penis for basic research and tissue engineering. Eur Urol 2005; 47(5):710–718, discussion 718–719 Kwon TG, Yoo JJ, Atala A. Autologous penile corpora cavernosa replacement using tissue engineering techniques. J Urol 2002; 168(4 Pt 2):1754–1758 Chen KL, Eberli D, Yoo JJ, Atala A. Bioengineered corporal tissue for structural and functional restoration of the penis. Proc Natl Acad Sci U S A 2010;107(8):3346–3350 Eberli D, Susaeta R, Yoo JJ, Atala A. A method to improve cellular content for corporal tissue engineering. Tissue Eng Part A 2008; 14(10):1581–1589 Atala A. Tissue engineering of reproductive tissues and organs. Fertil Steril 2012;98(1):21–29 Song LJ, Xu YM, Li C, Fu Q, Cui L, Hu XY. Construction of cavernosum smooth muscle using umbilical artery smooth muscle cells seeded on acellular corporal collagen matrices. Int J Androl 2009;32(5):514–523 Ji C, Min F, Liang W, et al. Construction of tissue-engineered corpus cavernosum with muscle-derived stem cells and transplantation in vivo. BJU Int 2011;107(10):1638–1646 An G, Ji C, Wei Z, Chen H, Zhang J. Engineering of corpus cavernosum using vascular endothelial growth factor-expressing muscle-derived stem cells seeded on acellular corporal collagen matrices. Urology 2013;81(2):424–431 Raya-Rivera AM, Baez C, Atala A, Yoo JJ. Tissue engineered testicular prostheses with prolonged testosterone release. World J Urol 2008;26(4):351–358 Rubenwolf P, Southgate J. Permeability of differentiated human urothelium in vitro. Methods Mol Biol 2011;763:207–222 Welk B, Herschorn S, Law C, Nam R. Population based assessment of enterocystoplasty complications in adults. J Urol 2012;188(2): 464–469 Neuhof H. Fascial transplantation into visceral defects: an experimental and clinical study. Surg Gynecol Obstet 1917;25:383–387 Zhang Y, Kropp BP, Lin HK, Cowan R, Cheng EY. Bladder regeneration with cell-seeded small intestinal submucosa. Tissue Eng 2004;10(1-2):181–187 Schaefer M, Kaiser A, Stehr M, Beyer HJ. Bladder augmentation with small intestinal submucosa leads to unsatisfactory longterm results. J Pediatr Urol 2013;9( 6 Pt A):878–883 Caione P, Boldrini R, Salerno A, Nappo SG. Bladder augmentation using acellular collagen biomatrix: a pilot experience in exstrophic patients. Pediatr Surg Int 2012;28(4):421–428 Jack GS, Zhang R, Lee M, Xu Y, Wu BM, Rodríguez LV. Urinary bladder smooth muscle engineered from adipose stem cells and a


Vol. 24

No. 3/2014


69

engineering for the treatment of stress urinary incontinence. Int Urogynecol J 2013;24(4):533–535 Chen F, Yoo JJ, Atala A. Acellular collagen matrix as a possible “off the shelf” biomaterial for urethral repair. Urology 1999;54(3): 407–410 Xie M, Song L, Wang J, Fan S, Zhang Y, Xu Y. Evaluation of stretched electrospun silk fibroin matrices seeded with urothelial cells for urethra reconstruction. J Surg Res 2013;184(2):774–781 Hu YF, Yang SX, Wang LL, Jin HM. Curative effect and histocompatibility evaluation of reconstruction of traumatic defect of rabbit urethra using extracellular matrix. Chin J Traumatol 2008;11(5):274–278 Fu Q, Deng CL, Liu W, Cao YL. Urethral replacement using epidermal cell-seeded tubular acellular bladder collagen matrix. BJU Int 2007;99(5):1162–1165 Micol LA, Arenas da Silva LF, Geutjes PJ, et al. In-vivo performance of high-density collagen gel tubes for urethral regeneration in a rabbit model. Biomaterials 2012;33(30):7447–7455 Orabi H, AbouShwareb T, Zhang Y, Yoo JJ, Atala A. Cell-seeded tubularized scaffolds for reconstruction of long urethral defects: a preclinical study. Eur Urol 2013;63(3):531–538 Olsen L, Bowald S, Busch C, Carlsten J, Eriksson I. Urethral reconstruction with a new synthetic absorbable device. An experimental study. Scand J Urol Nephrol 1992;26(4):323–326 Chung YG, Tu D, Franck D, et al. Acellular bi-layer silk fibroin scaffolds support tissue regeneration in a rabbit model of onlay urethroplasty. PLoS ONE 2014;9(3):e91592 Dorin RP, Pohl HG, De Filippo RE, Yoo JJ, Atala A. Tubularized urethral replacement with unseeded matrices: what is the maximum distance for normal tissue regeneration? World J Urol 2008;26(4):323–326 Li CL, Liao WB, Yang SX, et al. Urethral reconstruction using bone marrow mesenchymal stem cell- and smooth muscle cell-seeded bladder acellular matrix. Transplant Proc 2013;45(9):3402–3407 Mikami H, Kuwahara G, Nakamura N, Yamato M, Tanaka M, Kodama S. Two-layer tissue engineered urethra using oral epithelial and muscle derived cells. J Urol 2012;187(5):1882–1889 Feng C, Xu YM, Fu Q, Zhu WD, Cui L. Reconstruction of threedimensional neourethra using lingual keratinocytes and corporal smooth muscle cells seeded acellular corporal spongiosum. Tissue Eng Part A 2011;17(23-24):3011–3019 Gu GL, Xia SJ, Zhang J, et al. Tubularized urethral replacement using tissue-engineered peritoneum-like tissue in a rabbit model. Urol Int 2012;89(3):358–364 Li C, Xu YM, Song LJ, Fu Q, Cui L, Yin S. Urethral reconstruction using oral keratinocyte seeded bladder acellular matrix grafts. J Urol 2008;180(4):1538–1542 Li C, Xu YM, Liu ZS, Li HB. Urethral reconstruction with tissue engineering and RNA interference techniques in rabbits. Urology 2013;81(5):1075–1080 Auger FA, Rémy-Zolghadri M, Grenier G, Germain L. A truly new approach for tissue engineering: the LOEX self-assembly technique. Ernst Schering Res Found Workshop 2002;(35):73–88 L’Heureux N, Stoclet JC, Auger FA, Lagaud GJ, Germain L, Andriantsitohaina R. A human tissue-engineered vascular media: a new model for pharmacological studies of contractile responses. FASEB J 2001;15(2):515–524 Orabi H, Bouhout S, Morissette A, Rousseau A, Chabaud S, Bolduc S. Tissue engineering of urinary bladder and urethra: advances from bench to patients. ScientificWorldJournal 2013;2013(13): 154564 Imbeault A, Bernard G, Rousseau A, et al. An endothelialized urothelial cell-seeded tubular graft for urethral replacement. Can Urol Assoc J 2013;7(1-2):E4–E9 Fossum M, Svensson J, Kratz G, Nordenskjöld A. Autologous in vitro cultured urothelium in hypospadias repair. J Pediatr Urol 2007;3(1):10–18

Garriboli et al.


112

113

114

115

116

117

118

119

120

Garriboli et al.

three dimensional synthetic composite. Biomaterials 2009; 30(19):3259–3270 Bharadwaj S, Liu G, Shi Y, et al. Multipotential differentiation of human urine-derived stem cells: potential for therapeutic applications in urology. Stem Cells 2013;31(9):1840–1856 Oottamasathien S, Wang Y, Williams K, et al. Directed differentiation of embryonic stem cells into bladder tissue. Dev Biol 2007; 304(2):556–566 Cimetta E, Flaibani M, Mella M, et al. Enhancement of viability of muscle precursor cells on 3D scaffold in a perfusion bioreactor. Int J Artif Organs 2007;30(5):415–428 Boruch AV, Nieponice A, Qureshi IR, Gilbert TW, Badylak SF. Constructive remodeling of biologic scaffolds is dependent on early exposure to physiologic bladder filling in a canine partial cystectomy model. J Surg Res 2010;161(2):217–225 Atala A, Bauer SB, Soker S, Yoo JJ, Retik AB. Tissue-engineered autologous bladders for patients needing cystoplasty. Lancet 2006;367(9518):1241–1246 Joseph DB, Borer JG, De Filippo RE, Hodges SJ, McLorie GA. Autologous Cell Seeded Biodegradable Scaffold for Augmentation Cystoplasty: Phase II Study in Children and Adolescents with Spina Bifida. J Urol 2014;191(5):1389–1395 Subramaniam R, Hinley J, Stahlschmidt J, Southgate J. Tissue engineering potential of urothelial cells from diseased bladders. J Urol 2011;186(5):2014–2020 Turner A, Subramanian R, Thomas DF, et al. Transplantation of autologous differentiated urothelium in an experimental model of composite cystoplasty. Eur Urol 2011;59(3): 447–454 Fraser M, Thomas DF, Pitt E, Harnden P, Trejdosiewicz LK, Southgate J. A surgical model of composite cystoplasty with cultured urothelial cells: a controlled study of gross outcome and urothelial phenotype. BJU Int 2004;93(4):609–616


Vol. 24

No. 3/2014

121 Subramaniam R, Turner AM, Abbas SK, Thomas DF, Southgate J.

122

123

124

125

126

127

128

129

Seromuscular grafts for bladder reconstruction: extra-luminal demucosalisation of the bowel. Urology 2012;80(5):1147–1150 Wezel F, Pearson J, Southgate J. Plasticity of in vitro-generated urothelial cells for functional tissue formation. Tissue Eng Part A 2014;20(9-10):1358–1368 Tian H, Bharadwaj S, Liu Y, Ma PX, Atala A, Zhang Y. Differentiation of human bone marrow mesenchymal stem cells into bladder cells: potential for urological tissue engineering. Tissue Eng Part A 2010;16(5):1769–1779 Liu J, Huang J, Lin T, Zhang C, Yin X. Cell-to-cell contact induces human adipose tissue-derived stromal cells to differentiate into urothelium-like cells in vitro. Biochem Biophys Res Commun 2009;390(3):931–936 Shi JG, Fu WJ, Wang XX, et al. Transdifferentiation of human adipose-derived stem cells into urothelial cells: potential for urinary tract tissue engineering. Cell Tissue Res 2012 Zhang M, Xu MX, Zhou Z, et al. The Differentiation of Human Adipose-Derived Stem Cells towards a Urothelium-Like Phenotype In Vitro and the Dynamic Temporal Changes of Related Cytokines by Both Paracrine and Autocrine Signal Regulation. PLoS ONE 2014;9(4):e95583 Drewa T, Joachimiak R, Bajek A, et al. Hair follicle stem cells can be driven into a urothelial-like phenotype: an experimental study. Int J Urol 2013;20(5):537–542 Shoae-Hassani A, Mortazavi-Tabatabaei SA, Sharif S, et al. Differentiation of human endometrial stem cells into urothelial cells on a three-dimensional nanofibrous silk-collagen scaffold: an autologous cell resource for reconstruction of the urinary bladder wall. J Tissue Eng Regen Med 2013 Wezel F, Southgate J. Reprogramming stromal cells from the urinary tract and prostate: a trip to pluripotency and back? Eur Urol 2013;64(5):762–764, discussion 764–765


236

Copyright of European Journal of Pediatric Surgery is the property of Georg Thieme Verlag Stuttgart and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use.

Regenerative pharmacology in urology.

Tissue engineering and regenerative medicine: bench to bedside in urology. Preface.

Regenerative medicine.

Regenerative medicine.

Telocytes in regenerative medicine.

[Stem cell therapy and tissue engineering in regenerative urology].

Decellularized scaffolds in regenerative medicine.

Manufacturing challenges in regenerative medicine.

Regenerative medicine: transdifferentiation in vivo.

Regenerative medicine in Alzheimer's disease.

Regenerative medicine blueprint.

Advancing regenerative medicine.

Stem cell research and regenerative medicine in 2014: first year of regenerative medicine in Japan.

Centre for Commercialization of Regenerative Medicine: moving forward with regenerative medicine commercialization in Canada.

MicroRNA delivery for regenerative medicine.

World Conference on Regenerative Medicine.

CMD kinetics and regenerative medicine.

Healthy ageing and regenerative medicine.

Functional imaging for regenerative medicine.

Putting regeneration into regenerative medicine.

Regenerative medicine: Rebuilding the backbone.

Regenerative medicine. 'Rejuvenating' protein doubted.

Regenerative medicine for Parkinson's disease.

Regenerative medicine for the cornea.