LEUKEMIA INHIBITORY FACTOR (LIF): A GROWTH FACTOR WITH PLEIOTROPIC EFFECTS ON BONE BIOLOGY Peter Van Vlasselaer Vlaamse Instelling voor Technologisch Onderzoek V.I.T.0 Department of Environment Biology Steenweg op Retie 2440 Geel, Belgium

Historically, growth factors are denominated based on a spectifc biological activity. In muny cases, these,factors display a much broader spectrum ofactivities, especially when their eject is tested on various cellor tissue types. Consequently, names qfcertain,factor.s are quite deceptive. A textbook example is leukemia inhibitory factor ( LIF). LIF was initiallv described based on its ability to induce dtferentiation in the murine myeloid leukemia cell line MI. Later, LIF turned out to be a synonym for at least nine different .factors defined on the basis of their effects on a variety of cell ty*pesincluding lymphomas, liver cells, embryonic stem cells andcarcinoma cells, neurons, melanomas andosteoclasts. Apart,from its d@rential e@ct on unrelated cell types and tissues, LIF induces biphasic effects on cells of’ the same “lineage” as well. Needless to say, LIF activity in these circumstances largely depends on the developmental stage of the target cells. An example is LIF activity on bone cells. Osteoclast as well as osteoblast activity is .stimulated or suppressed by LIF depending on the developmental stage of the respective cells. This concept is of utmost importance in the evaluation of the seemingly opposing or contradictory~ eflects qf LIF in vitro as well as in vivo. Keywords: Growth factor, leukemia target cells, osteoclast, osteoblast.

inhibitory

factor,

LIF,

developmental

stage,

INTRODUCTION Bone is a dynamic tissuecomposed of a mineralized extracellular matrix and “boneforming” and “bone-resorbing” cells, denominated osteoblasts and osteoclasts. Maintenance of the functional properties and volume of bone is the result of a balance between its continuous formation and destruction. This process requires complex sequencesof cellular events which are modulated by site- and cell-specific signals capable of initializing and promoting recruitment and proliferation of osteoblastsand/ or osteoclasts at the right time in the right place. Disruption of this delicate balance results in pathological disorders. 337

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In recent years, cytokines and growth factors have been shown to influence bone remodeling [l] and to play a role in certain bone pathologies, such asosteopetrosis [2, 31,post-menopausal osteoporosis [4,5] and rheumatoid arthritis [6,7]. One of the most novel cytokines to receive attention with regard to bone biology was the Leukemia Inhibitory Factor (LIF). LIF is a 20-60 kilodalton (kDa) glycoprotein that was purified and cloned basedon its ability to induce differentiation of the murine myeloid leukemia cell line M 1 [S-12]. However, the common designation “leukemia inhibitory factor” may be misleading since: (1) LIF can not only stimulate but also inhibit proliferation and differentiation depending on the leukemic cell line examined [12-l 51,and (2) LIF exerts a pleiade of biological effects which are not restricted to myeloid leukemias [ 16, 171. Consequently, LIF was found to be identical to several factors that were independently purified and cloned based on activities on a variety of seemingly unrelated cell types and tissues.Human interleukin for DA cells (HILDA) which was found to be identical to LIF was cloned based on its potential to sustain the proliferation of the MO-MuLV transformed lymphoma cell line DA-la [7, 181. Cultured keratinocytes and squamouscarcinoma cell linesproduce a factor identical to LIF, which stimulates the synthesis of acute phase plasma proteins in the liver and is termed accordingly hepatocyte stimulating factor III (HSFIII) [19, 201. Differentiation-inhibitory activity (DIA), derived from buffalo rat liver cells, inhibits the spontaneous differentiation of embryonic stem cells into endo-, ecto- and mesoderm and allows their long-term renewal [21-251. DIA, initially designated differentiationretarding factor (DRF) [26], is known to be identical to LIF. Rat heart cell conditioned medium contains a factor which is termed cholinergic neuronal differentiation factor (CNDF) because it controls the phenotype of neurons without affecting their proliferation [27]. It is now documented that CNDF and LIF represent the same protein [27]. Injection of LIF in mice results in a state of cachexia which is accompanied by severeweight lossand hypertriglyceridema [28,29]. These phenomena are identical to the effect of a factor, recently purified from a melanoma cell line associated with cancer cachexia, which blocks the key enzyme of triglyceride metabolism, lipoprotein lipase, and was named melanoma-derived lipoprotein lipase inhibitor I (MLPL-I) [30]. Also MLPL-I showed to be identical to LIF. In the 1970s. the term “osteoclastactivating factor” (OAF) was applied to describe the bone-resorbing activity present in supernatants from lectin activated lymphocytes [31]. In the meantime it is known that OAF is a generic term for a number of bone-resorbing cytokines including IL- 1, IL-6. TNF-cw and TNF-/I [32]. With the identification of the differentiation inducing fdctor (DIF or D- Factor) as a bone resorbing agent, derived from activated mousesplenocytes, L929 fibroblasts and the osteoblastic cell line MC3T3-El, a new member could be added to the existing list of OAFS [33335]. Purification of human and murine DIF revealedthat LIF and DIF representthe samemolecule [36]. From the above, it is clear that LIF has many namesand can be considered asone of the molecules with the widest number of different biological activities described up to the present day [37, 381.The aim of this article is to review and discussthe literature which associatesLIF with bone biology. In addition, somerecent information about LIF activity on the osteogenic potential of undifferentiated mesenchymalcells from the mouse bone marrow is included.

Lrukerniu

Inhibitory

Factor

ACTIONS

OF LIF ON BONE IN VZTRO EfSect on Osteoclasts

A large body of evidence showsthat growth factors and cytokines play an important role in bone resorption [l, 391.The term “osteoclast-activating factor” (OAF), which originally referred to the bone resorbing activity secretedby activated leukocytes [3 I, 34, 40, 411, represents in fact a generic activity rather than a single factor and is composed of IL-l, IL- 6, TNF-d and TNF-13. The osteolytic activity of each of these factors has well been documented [42]. LIF was biochemically purified from protein fractions displaying OAF activity by Abe et al. [34] suggesting its involvement in osteoclastic bone resorption. Indeed, according to Reid et al. [43], LIF stimulated 45Ca releasefrom pre-labeled neonatal mouse calvaria in a dose-dependent manner. This phenomenon coincided with an increasein the absolute number of osteoclastsper mm’ bone and was blocked by indomethacin. In parallel [‘HI-thymidine and [‘HIphenylanaline incorporation was increased in the presence of LIF but could not be blocked by indomethacin. Consequently, resorption mechanisms induced by LIP involve prostaglandin (PG) production, whereas distinct mechanismsare responsible for the stimulation of DNA and protein synthesis. However, DNA synthesisappeared to be important for LIF’s osteolytic activity since “‘Ca release from pre-labeled neonatal mousecalvaria was at least partially inhibited in the presenceof hydroxyurea [44]. Apparently, LIF affects the development of osteoclastsrather than their activity which is obviously regulated by secondary signals such as PGs. In this context, LIF activity closely resembledthat ofTGF-P, IL- I and TNF-crwhich likewise induced bone resorption in mousecalvaria involving PG synthesis[45,46]. Interestingly, PGs induce cAMP synthesis in osteoblasts which subsequently get activated and as a result synthesize and secrete PGs themselves [47-511. Via this pathway, osteoblasts cannot only regulate their own function but also that of osteoclasts within their sphere of action. This idea agrees with the hypothesis of Rodan and Martin [52] about osteoclast/osteoblast interaction and is further supported by the observation that osteoclast deficiency in the osteopetrotic op/op mouse is due to a defect in the local environment provided by osteoblastic cells 1.531. Although it is an appealing idea that LIF regulates osteolytic events via a prostaglandin-mediated pathway, additional observations show that things are not as simple as that. For instance, according to lshimi et al. [54] LIF displayed no osteolytic activity by itself and induced “Ca release from neonatal mousecalvaria exclusively in the presenceof other cytokines such as IL1 and I L-6. Since this study was performed in the sameculture system and comparable concentrations of LIF were used as by Reid et al. [43, 441, the reasons for the discrepancy in results are not clear. Things get even more complicated when the osteolytic activity of LIF was studied on rat long bones. In this culture system, Lorenzo P[ al. [55] demonstrated that LIF inhibited bone resorption via mechanismswhich are independent from prostaglandin synthesis and cell proliferation. Although DNA synthesiswas not affected. this study does not necessarilyoppose the findings of Reid rt al. [43. 441 since LIF caused a biphasic response in which it stimulated early DNA synthesis but became inhibitory after 72 h of exposure in the calvaria system. Differences between the resorptive responses in both culture systems have been reported for other cytokines including TGF-/3[46, 561,TGF-a[46, 57, 581,and TNF- r [59, 601 as well. As for LIF, their bone resorptive activity in the calvaria model

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dependson PG synthesis whereastheir osteolytic effect on long boneswas not reduced by PG inhibitors. Apparently. the degree of osteolytic activity of a given growth factor is determined by the anatomical localization of the target tissue. It is conceivable that different responsivenesscan be attributed to the stage of osteoclast development in the particular bone explant. Differences in stagesof osteoclast development are found in mousemetacarpals of different ages[61]. In addition, functional studiesby Van Beek et al. [62, 631 showed that LIF added to 17-day-old fetal mouse metacarpal organ cultures, which contain only osteoclast progenitors and precursors, significantly inhibited bone resorption. Histological examination of the explants showed that osteoclast progenitors and precursors remained in the periosteum and did not invade the mineralized matrix. In contrast, when LIF was added to metacarpals of older fetuses (18- and 19-day-old), in which the mineralized cartilage has been invaded by mature osteoclasts, the inhibition of resorption was significantly less.These findings clearly illustrate that the efficacy of LIF to suppressbone resorption depends on the stage of osteoclast development and that with increasing maturation of the bone explants the antiresorptive potency of LIF decreases.This may reflect changesin LIF receptor expression on osteoclastsof different developmental stages.For example, no receptors for LIF could be demonstrated on adult osteoclasts [64]. However the presence of LIF receptors on osteoclast precursors cannot be ruled out at present, especially since they were demonstrated on precursors of the macrophage lineage [65]. In addition, Van Beek et al. [62,63] and Shinar et al. [66] demonstrated that LIF affects the post-mitotic steps of osteoclast development becausethe inhibitory effect of LIF could be overcome or reversed by both PTH and 1,25-(OH), D,. Previous studies demonstrated that the latter agents stimulated osteoclastic resorption by increasing osteoclast formation from late precursors. characteristic post-mitotic steps in osteoclast development [67-701. The differential responsivenessof immature and mature osteoclaststo growth factors was furthermore illustrated by the Van Beek et al. for IL-6 [71] and TNF-cw [67]. .Efect on Osteohlasts

Bone formation is characterized by the temporal sequence of expression of markers encoding the osteoblastic phenotype and is defined by three distinct periods: proliferation, maturation of the extracellular matrix and mineralization [72,73]. Lowe et al. [74] demonstrated that LIF produced an early stimulation of DNA synthesis in growth-arrested and actively growing rat calvaria osteoblasts which does not require the presenceof prostaglandins. This observation is consistent with the data of Reid et al. [43, 441 indicating that increased [3H]-thymidine incorporation in LIF-treated calvaria reflects mainly osteoblast proliferation. Moreover, this suggests that the osteolytic activity of LIF in this culture system involves the presence of activated osteoblasts. Enzymatically digested calvaria contain a variety of cell types and can hardly be considered as a purified source of osteoblasts [75]. Consequently. in spite of the fact that osteoblasts express LIF receptors [54, 64, 761, it is impossible to discriminate direct from indirect effects of LIF on osteoblastsin thesecell preparations. Noda et al. [77] addressedthis issue,using the clonal murine osteoblast-like cell line MC3T3-El [78], and revealed that in contrast to the effect on e.y viva prepared osteoblasts, LIF significantly inhibited DNA synthesis in MC3T3-El cells. Comparable results were obtained by Ishimi et al. [54] using the samecell line. This inhibitory

DNA synthesis IJH]-Thymidine cpm x 1000

ALP activity p-nitrophenol nmolhin

il Control

LIF

Control

Collagen [WI-Proline opm x 1000

Osteocalcin rig/well

Calcium pg/well 5

4

3

2

1

LIF

C ontrol

LIF

Control

LIF

0 II Control

LIF

FIGURE 1. Bone marrow cultures were set up from 5- fluorouracil treated mice. LIF (Iti U ml ‘) was added from the onset and 13Hj-thymidine incorporation, ALP activity, collagen synthesis, osteocalcin synthesis and mineralization were determined on days 12,18,21,24 and 27, respectively.

activity is not characteristic for the MC3T3-El cells since LIF suppressed DNA synthesis in the rat osteosarcoma cell line UMR-106 as well [74]. Similar to LIF, the effect of TGF-j?on cell proliferation also varies among different bone cell populations. Whereas TGF-/3 stimulated DNA synthesis in fetal rat calvaria and isolated rat bone cells [79. 801, it inhibited the growth of clonal murine osteoblast-like cells and osteosarcoma cells [81-831. However, it is most likely that both factors have distinct mechanisms of action since LIF could further suppress DNA synthesis below the level produced by saturating concentrations of TGF-p [77]. As indicated above for osteoclasts, the tilscrepancy between the effects of LIF and TGF-I) on bone cells of different origin may be related to the developmental stage of the osteoblastic cells. For example, osteoblasts from fetal bone were more responsive to the mitogenic activity of TGF-B than similar cells from newborns [84]. lt is therefore conceivable that the stimulation of DNA synthesis by LIF in a calvaria-derived cell mixture reflects the response of a cell population of less differentiated osteoblastic cells. Although the developmental stage may explain LIF suppressive activity on the proliferation of MC3TSEI and UMR- IO6 cells as well, one cannot rule out that differences in response to LIF are due to the abnormal regulation ofcell growth in these cells in the first place. In addition to effects on cell proliferation, LIF modulates the expression of osteoblast differentiation markers as well. Noda rt al. [77] demonstrated reduced alkaline phosphatase (ALP) activity and type I procollagen mRNA levels in LIF treated MC3T3-El cells. On the other hand, the synthesis of osteopontin was increased. indicating that LIF does not merely inhibit general protein synthesis in osteoblastic cells. This is of particular interest in the understanding of osteoclast-osteoblast interaction since osteopontin appears to anchor osteoclasts in bone via vitronectin receptors on their cell membrane [SS, 861. The inhibitory effect of LIF on constitutive ALP activity contrasts with its stimulatory effect of retinoic acid-induced ALP activity in the preosteoblast-like rat RCT-I cell line [76], MC3T3-El cells [54] and the rat osteoblast-like cell line UMR-201 [64]. Apart from the possibility that retinoic acid stimulates differentiation events which change osteoblast responsiveness to LIF, there

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DNA synthesis [3H1-Thymidine cpm x 1000

ALP activity p-nitrophenol

Collagen [‘HI-Proline cpm x 1000

Calcium pg/well

rig/well 50

+ II C3ontrol

0 LIF

Control

LIF

Control

LIF

Control

LIF

Control

LIF

FIGURE 2. Bone marrow cultures were set up from S-fluorouracil treated mice. LIF (10’ U ml ‘) was added at the time of full mineralization, e.g. day 24 of culture. Three days later, (‘HI-thymidine incorporation, ALP activity, collagen synthesis, osteocalcin synthesis and mineralization were determined.

is no other plausible explanation. In general. little is known about the molecular mechanism of LIF activity. Preliminary chloramphenicol acetyltransferase assaysat least indicate that LIF inhibits the promoter region of mouse type I procollagen gene, suggesting its activity through transcriptional events [77]. The above illustrates that LIF exerts a number of direct effects on cloned osteoblast-like cell lines. An additional specific action of LIF was reported by Allen et al. [64] on the plasminogen activator (PA)/plasmin system in osteoblasts. Treatment of calvarial osteoblasts or UMR-106 cells with LIF resulted in a dose-dependent inhibition of PA activity. Apparently, this responseresulted from an increased synthesisof plasminogen activator inhibitor (PAI) induced by LIF. Similar effects on the PA/plasmin system in the UMR-106 cells were induced by TGF-/?. It seems,however, unlikely that TGF-Pmediates the action of LIF sinceantiserum against TGF-phad no effect on LIF inhibition of PA activity. One can image that via this pathway, LIF contributes positively to bone formation by blocking PA activity via PA1 induction, resulting in a net reduction of neutral protease activity. Osteoblasts are not solely target cells for LIF in bone, they also produce LIF as demonstrated in a variety of osteoblast-like cells, including preosteoblastic UMR- 201 and UMR-106 cells [64], clonal mouse MC3T3-El cells [87], osteoblast-like cells from human trabecular bone [88] and human osteosarcoma cell lines [89]. Moreover, LIF synthesisappears to be regulated by other agents. Indeed, bone resorbing factors such as IL-l, TNF-a: TGF-P, lipopolysaccharide. retinoic acid and phorbol esters were illustrated to stimulate LIF synthesis in rat, mouse and human osteoblastic cells [54. 87-891. Consequently, LIF is considered to function as an autocrine regulator of osteoblast activity. An issuewhich awaits further elucidation is whether LIF has the potential to induce the expression of other growth factors in osteoblastic cells. At the very least, LIF appears not to induce the expression of its own mRNA [54], which makes it unlikely that osteoblast activation is modulated via the induction of additional LIF synthesis. Whereas the majority of work on LIF activity on bone was performed on cells displaying different degrees of osteogenic “commitment”. little is known about the

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effects of LIF on ‘naive” or osteogenic “uncommitted” cells. Therefore, the author believed that it was of interest to include some recent data from his laboratory on the effects of LIF on the osteogenic activity of mouse bone marrow [93]. Bone marrow is composed of hemopoietic cells and stroma which forms a complex network of fibroblasts, adipocytes, endothelial cells and macrophages and is believed to harbor undifferentiated mesenchymal cells which form mineralized bony structures irz vitro and bone ossicles when transplanted ectopically in vivo [73, 90-921. Bone marrow cultures were set up in the presence of vitamin C and /I-glycerophosphate and LIF was added to the cultures either from the start or at the moment of full mineralization [73]. Consecutively, [‘HI thymidine incorporation, ALP activity, synthesis of collagen and osteocalcin and mineralization were determined at the moment of their maximum expression. at days 12, 18,21,24 and 27 of culture, respectively. When added from the start of the culture, LIF significantly inhibited DNA synthesis, ALP activity, synthesis of collagen and osteocalcin and final mineralization (Fig. 1). In contrast, LIF did not affect any of these markers when added to fully mineralized bone marrow cultures (Fig. 2). Most simply this could be explained by a biphasic effect of LIF determined by the differentiation degree of the mesenchymal cells. Whereas LIF inhibits cell proliferation and bone protein synthesis by mesenchymal cells during their progression through osteoblastic differentiation, it do.es not affect cell proliferation or bone protein synthesis of adult osteoblasts. Cell proliferation plays an important role in the onset of osteoblastic differentiation [72, 731. It is therefore conceivable that by virtue of its inhibitory activity on DNA synthesis, LIF prevents the transition of uncommitted mesenchymal cells towards the bone lineage. Consequently, this would result in reduced levels of bone protein synthesis and mineralization. This observation corresponds to recent findings by Van Beek et ul. [63] who showed an osteoclastindependent inhibition of cell growth, ALP activity and mineralization in LIF treated fetal mouse meta< .:rpals. Since LIF does not block ALP activity in preosteoblastic rat calvaria cells (TRCT-I) and ROS 17/2.8 cells [76], but significantly blocks cell proliferation and ALP activity in MC3T3-El cells [54,74. 771, this may imply that the latter cells are less differentiated osteoblasts than the former two. ACTIONS Administrution

OF LIF ON BONE

IN VZVO

and Tissue Distribution

of’LIF

It is obvious that the relevance of in vitro activity of growth factors is measured by the correlation with their effects Di rho. The information from the group of Metcalf et uf. [95-98. 1021 about the effects of LIF in viva is therefore of great value. These investigators established two protocols to administer LIF in viva. In a first approach, mice were engrafted with the hematopoietic cell line FDCP- 1 (FD cells) [94], which was infected with a retroviral construct containing LIF encoding cDNA (FD/LIF cells) [95. 1021. On the other hand, they administered purified LIF by repetitive intravenous or intraperitoneal injections [96,97]. It is evident that the biological activity of any agent in rive is largely determined by its distribution in the body. Attention is given to the accessibility of LIF to different tissues depending on the route of administration. Screening of a wide variety of organs from engrafted animals showed accumulation of FD/LIF cells in the bone marrow, spleen, femur and mesenteric lymph nodes [95].

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Accordingly, LIF mRNA levels were dramatically increased in these tissues. Other tissues such as the kidneys, salivary glands, skeletal muscle, pancreas or heart showed no increase in LIF mRNA levels, suggesting that the FD/LIF cells did not randomly distribute in the body but specifically migrated to defined target organs. This phenomenon is determined by the features of the FD cells and is not affected by the introduction of LIF cDNA since uninfected cells showed identical tissue distribution [98]. Tissue-specific “homing” in viva was demonstrated for hematopoietic cells and appears to be regulated by the interaction of their membrane proteins with specific ligands in the target organ [99]. Recipients of FD/LIF cells showed elevated LIF serum levels. Therefore it could be expected that locally synthesized LIF can reach and accumulate in distant organs via the circulation, independent from cellular “homing” forces, but based on binding characteristics of the respective tissues. Radiographic analysis showed that intravenously injected radioiodinated LIF (“‘I-LIF) was rapidly cleared from the serum and accumulated in the kidneys, liver, lungs, spleen and thyroid gland due to non-specific and specific binding [96]. For example, organs involved in the clearance of proteins and iodine metabolism such as kidney, pancreas, salivary glands. placenta and the thyroid gland bound lZ51-LIF in a non- specific manner. On the other hand, specific labeling due to the presence of LIF receptors was demonstrated on hepatic parenchyme, red pulp and lymphoid follicles of the spleen, lung, megakaryocytes. placental trophoblast and osteoblasts in the bone cavities. The appearance of large amounts of non-precipitable “51-LIF in the urine suggested that the kidneys were the major route of LIF clearance from the body. Information about experimental elevation of LIF in viro using different administration protocols may be useful for future clinical trials as, for example, suggested by Metcalf et al. [29] for the treatment of thrombocytopenia. General Pathological

l?fects qfLIF

Administration of LIF in vivo by injection or by engrafting FD/LIF cells has a variety ofpatho-physiological consequences [95598.102], some ofwhich parallel effects in vitro. Within approximately IO days after injection of either FD/LIF cells or purified LIF, the animals displayed a number of general characteristics such as a ruffled fur, hyperactive and irritable behavior and dramatic weight loss, the latter mainly due to a reduction of subcutaneous and abdominal fatty tissue. These symptoms may reflect the ability of LIF to (1) switch autonomic nerve signaling from the adrenergic to the cholinergic mode [27] and (2) inhibit the activity of lipoprotein lipase, a key enzyme in fat metabolism [30]. Within days of exhibiting these signs the animals developed a state of fatal cachexia and showed classic signs of an acute-phase response such as increased erythrocyte sedimentation rates and a drop in the serum albumin level. The ability of LIF to induce acute-phase proteins by the liver [19, 201 is likely to be responsible for the latter phenomena. The cachectic activity of LIF in vivo was of particular interest since only TNF-awas known to induce cachexia [ 1001. It remains to be emcidated whether LIF induces cachexia via direct mechanisms or whether it merely stimulates the synthesis of TNF-a. Although Black et al. [lOI] recently added IL-6 to the list of cachectic agents, it is unlikely that LIF acts via this cytokine, since IL-6 levels appeared to be identical in control and LIF injected animals [29]. Moribund FD/LIF recipients showed a number of macroscopic abnormalities such as reduced pancreas, thymus atrophy, spleen enlargement, reduced reddish adrenals

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Factor

TABLE I. Microscopic characteristics of tissue lesions in FD/LIF recipients Tissue

Lesion

Bone marrow and bone

Increased osteoblast numbers Excess bone formation and resorption Excess deposition of collagen and reticulin in the marrow Reduced erythroid and lymphoid cells Increased immature and mature granulocytes Increased megakaryocytes Aplasia of lymphoid follicles Enlarged hemopoietic areas in the red pulp Increased numbers of erythroid, granulocytic

Spleen

Liver

Peripheral

shaft

and megakaryocytic

cells

Focal areas of hemopoietic cells Necrotic areas Fibrosis around portal vessels Plaques of calcification on the surface blood

Neutrophil Moderate

leukocytosis elevation of monocytes

and lymphoid

cells

Heart and skeletal muscle

Focal areas of calcification

Thymus

Atrophic

Pancreas

Dispersion of individual acini due to edema Patchy necrosis of acinar cells Occasional infiltration of mononuclear and granulocytic

with complete

loss of cortical

cells in the inner cortex,

lymphocytes

“brown

cells

Adrenals

Lipid-containing

degeneration”

Ovaries

Surrounded by a capsule of mainly lymphocytes Deficit in the number of corpora lutea and luteal cells of small volume

and occasionally calcified plaques on the liver surface [95-98, 1021. In addition, numerous tissue lesionswere observed during histological examination and are listed in Table 1. The changes in spleen, lymph nodes, bone marrow and bone could be associated with local production of LIF by “homed” FD/LIF cells. However, no obvious FD/LIF cells or elevated LIF mRNA levels were observed in the pancreas, muscle,adrenals and ovaries. Most simply, one could conclude that the lesionsin these organs were induced by a direct effect of LIF which reached these tissues via the circulation. However, this may be a premature conclusion since thesedisorders could not be induced by intraperitoneal injections of LIF [29]. LIF production restricted to a localized sphereof influence within a microenvironment due to FD/LIF cell “homing” as opposed to a systemic increase of LIF by injection could explain the difference between the effects of both administration protocols. The findings of Rathjen et (11. [ 1031.that LIF exists asboth a diffusible molecule and asa molecule incorporated in the extracellular matrix, are of special interest in relation to this issue. In addition, recent findings by Layton ef al. [ 1041raised the possibility that at least part of the diffusible LIF which enters the circulation may lose its biological activity. Indeed, these investigators purified a soluble truncated form of the crchain of the LIF receptor which can block the biological activity of LIF itz vitro at the concentration found in the serum. No information is available about the type of LIF secreted by the FD/LIF cells.

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However, the distinction between the roles of diffusible and immobilized LIF could be crucial to the multiplicity of the activity of the FD/LIF cells in 00. Although it is irrefutable that LIF induces pathological effects in vivo via direct mechanisms, it cannot be overlooked that certain disorders such as reduced organ parenchymal volume, thymus cortex atrophy, loss of adrenal lipid and the formation of defective corpora lutea may simply result from the genera1 state of cachexia of the animals as well. Specific Efects of LIF on Bone The most prominent abnormality in recipients receiving FD/LIF cells was the accumulation of osteoblasts and an excess of new bone formation which resembled a state of osteosclerosis or myelofibrosis [95, 1021. This phenomenon was most prominent at the ends of the long bones and resulted in the formation of bone trabeculae which invaded the marrow cavity and occupied the space which was previously available for hemopoietic cells. Consequently, a decrease in hemopoietic cell numbers in the marrow, splenomegaly with excess hemopoiesis in the liver and neutrophil leukocytosis occurred. Studies in the field of bone marrow regeneration after local injury revealed that merely the fact of marrow ablation by itself induced a systemic osteogenic response and trabecular bone growth which occluded the marrow cavity [lo551 111 and consequently evoked the relocation of hemopoietic activity to other organs [112]. It is conceivable that locally synthesized LIF may play an important role during these regeneration processes, especially since bone marrow stroma was recently shown to constitutively synthesize LIF [113]. On the other hand, increased bone formation in FD/LIF engrafted animals [95, 1021 could hypothetically result from the bone marrow ablation itself and not from LIF’s activity. This possibility is unlikely since intraperitoneal or intravenous LTF injections resulted in comparable reductions of marrow cell numbers without altering osteoblast proliferation. Apparently, excess bone growth in FD/LIF recipients resulted from LIF activity and not from until now unknown osteo-stimulatory effects induced by marrow ablation. Abnormal bone formation not only results from stimulated osteoblast growth, but also from reduced bone resorption due to deficient osteoclast activity [113-1201. The presence of prominent osteoclasts, irregularities in cortex width and widening of the foramina of the long bones demonstrated increased osteoresorptive activity in the FD/ LIF recipients [95, 1021. In the context of the overall excess of trabecular bone formation in these animals, this may sound contradictory. However, since osteoclasts of various developmental stages respond differently to LIF [62-661, it can theoretically not be excluded that LIF stimulates osteoclasts from the bone cortex but inhibits those from the trabecular areas in the marrow cavity. Because of the activation of cortical osteoclasts the possibility was considered that FD/LIF engraftment may have induced the production of colony-stimulating factors. However, in no case were abnormal levels of GM-CSF or multi-CSF observed in the FD/LIF animals as compared to recipients of FD cells [lO2]. Over the past decade, technology has been developed which allows the disruption or “knock-out” of genes ilz rive based on homologous recombination events of coding genes in embryonic stem cells [121]. Although the techniques of overexpression or disruption of genes provide experimental means to study the effect of gene product in viva, one has to be careful in interpreting the physiological relevance of this information since “knock-out” mice develop severe pathologies, depending on the importance of the respective gene in embryo-

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logical development. Recently, Stewart et al. [I221 generated LIF-deficient mice and illustrated the necessity of LIF expression in the endometrial glands during the implantation of the blastocyst. This is of particular interest in the context of the previous observations that LIF transcripts could be detected as early as the preimplantation stage of the mouse blastocyst [123, 1241. Since viable homozygotes. deficient for LIF expression, have been derived, this suggests that at least for the first months of postnatal existence there is no vita1 requirement for LIF in riro. Unfortunately, no detailed examination of the skeleton was performed in this study. Consequently, no information about the effect of the LIF deficient bone biology of these animals has been available until now. LIF und Bone Disorders

in Humans

Rheumatoid arthritis is a chronic systemic disease primarily of the joints, usually polyarticular. marked by inflammatory changes in the synovial membranes and articular structures by atrophy and rarefaction of the bones. Lotz et al. [125] showed that LIF is produced by joint tissue and is overexpressed during arthritis. LIF secretion in these cases appears to be stimulated by local factors present during joint inflammation such as TGF-b. platelet-derived growth factor, basic fibroblast growth factor. insulin-like growth factor, TNF-eland IL- lp. This implies that LIF is inducible in joint tissue by a comparable set of cytokines known to be enhanced during rheumatoid arthritis such as IL-6 [126. 1271, IL-8 [128, 1291 and MCP-1 [130]. Moreover. LIF has the potential to induce its own mRNA in chondrocytes and synoviocytes which may represent a mechanism to amplify the initial stimulus of LlF induction. In addition, LIF enhances the expression of IL-6, MCP- I and IL-8 which enables it to indirectly stimulate connective tissue cells. Together with the observation that LIF can stimulate the production of metalloproteinases, stromelysin and collagenase, LIF may very well exert catabolic effects on joint tissue comparable to IL- I and TNF-a [13 l- 1371. This is supported by the observation that LIF, in combination with IL-I and IL-6, at concentrations found in the synovial fluids of rheumatoid arthritis patients, greatly enhanced bone resorption in fetal calvaria [52]. Giant cell arteritis or Horton’s arteritis is a vasculitis syndrome affecting blood vessels whose walls contain significant amounts of connective tissue and has a predilection to affect the superficial temporal, ophthalmic and posterior ciliary arteries. Considerably elevated levels of circulating LIF were demonstrated in patients suffering from this syndrome. This is of particular interest since Horton’s disease is clinically associated with the polymyalgia rheumatica syndrome which affects predominantly the joints 11381. SUMMARY It appears that the degree of LIF activity on bone biology in vitro as well as in riro largely depends on the developmental stage of the osteoclasts and osteoblasts. It is clear that the delineation of differentiation steps is crucial to determine restriction points in osteoclast and osteoblast development and to define the target populations for LIF, or any other factor for that matter. In other words, the answer to questions of whether (I ) osteoclast activity is osteoblast-dependent, (2) LIF plays a key role in osteoblast,

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P. Van

Vlasselaer

osteoclast interaction, (3) osteoclast and osteoblast precursors and progenitors express LIF receptors, (4) LIF regulates the synthesis of bone forming or bone resorbing factors by osteoclasts and osteoblasts, and (5) LIF interacts with other factors to affect osteoclast and/or osteoclast activity, etc., awaits the development of culture systems using purified osteoblasts and osteoclasts or their progenitor cells. REFERENCES I. Gowen M. Cytokines and bone metabolism. Boca Raton. Ann Arbor, London: CRC Press; 1992. 2. Yoshida H, Hayashi S. Kunisada T, Ogawa M. Nishikawa S, Okamura H, Sudo T, Shutlz LD, Nishikawa S. The murine mutation osteopetrosis is in the encoding region of the macrophage stimulating factor gene. Narure 1990; 345: 442. 3. Wiktor-Jedrzejczak W, Bartocci A, Ferrante AW, Ahmed-Ansari A, Sell KW, Pollard JW. Stanley ER. Total absence ofcolony stimulating factor I in the macrophage deficient osteopetrotic (or/ op) mouse. Proc Nat1 Acad Sri USA. 1990; 87: 4828. 4. Pacifici R, Rifas L, Teitelbaum S. Slatopolsky E, McCracken R, Bergfeld M, Lee W, Avioli LV. Peck WA. Spontaneous release of interleukin I from human blood monocytes reflects bone formation in idiopathic osteoporosis. Proc Nut/ Acad Sci USA. 1987; 84: 4616. 5. Jilka RL, Hangcoc G, Girasole G, Passeri G, Williams DC. Abrams HS, Bayer B, Broxmeyer H, Manolagas SC. Increased osteoclast development after estrogen loss: Mediation by IL-6. ScLnce 1992; 257: 88. 6. Houssiau FA, Devogelaer JP, Van Damme 3, Nagant de Deuxchaines C, Van Snick .I. Interleukin 6 in synovial fluid and serum of patients with rheumatoid arthritis and other inflammatory arthritis. Arthritis Rheum. 1988; 3 1: 784. 7. Firestein GS, Xu WD, Townsend K. Broide D, Alvaro-Gracia J, Glasebrook A. Zwaifler NK. Cytokines in chronic inflammatory arthritis. I. Failure to detect T cell lymphokines (IL-2 and IL-3) and presence of macrophage colony stimulating factors and a novel mast cell growth factor in rheumatoid synovitis. J Exp Med. 1988; 168: 1573. 8. Tomida M. Yamamoto-Yamaguchi Y, Hozumi M. Purification of a factor inducing differentiation of mouse myeloid leukemic MI cells from conditioned medium of mouse fibroblast L929 cells. J Biol Chem. I984; 259: 10978. 9. Hilton DJ. Nicola NA. Gough NM, Metcalf D. Resolution and purification of three distinct factors produced by Krebs ascites cells which have differentiation inducing activity on murine myeloid leukemia cell lines. J Biol Gem. 1988; 263: 9238. IO. Hilton DJ. Nicola NA. Metcalf D. Purification of a murine leukemia inhibitory factor from Krebs ascites cells. Anal Biochem. 1988; 173: 359. I I. Gearing DP, Nicola NA, Metcalf D, Foote S, Wilson TA, Gough NM, Williams RL. Production of leukemia inhibitory factor in Exherichiu coli by a novel procedure and its use in maintaining embryonic stem cells in culture. Biotechnolog! 1989: 7: I 157. I2 Gearing DP, Gough NM, King JA, Hilton D.I. Nicola NA, Simpson RJ, Nice EC, Kelso A, Metcalf D. Molecular cloning and expression of cDNA encoding a murine myeloid leukemia inhibitory factor (LIF). EMBO J. 1987: 6: 3995. 13. Moreau JF, Donaldson DD, Bennett F, Witek-Giannotti JA. Clark SC, Wong GG. Leukemia inhibitory factor is identical to the myeloid growth factor human interleukin for DAcells. Nature 1988: 336: 690. 14. Maekawa T, Metcalf D. Clonal suppression of HL60 and U937 cells by recombinant human leukemia inhibitory factor (LIF) in combination with GM-CSF and G-CSF. Leukemia 1989; 3: 270. 15. Maekawa T. Metcalf D. Gearing DP. Enhanced suppression of human myeloid leukemia cell lines by combinations of IL-6, LIF. GM-CSF or G-CSF. Int J Cancer 1990; 45: 353. 16. Kurzrock R, Estrov 2, Wetzler M, Gutterman JU. Talpaz M. LIF: not just a leukemia inhibitory factor. Endocr Rev. 1991: 12: 208. 17. Hilton DJ, Cough NM. Leukemia inhibitory factor: a biological perspective. J CeN Biochem. 1991; 46: 21. 18. Gascan H, Godard C. Ferenz C. Naulet J. Preloran V. Peyrat MA. Hewick R. Jacques Y. Moreau JF. Soulillou JP. Characterization and NH,-terminal amino acid sequence of natural human interleukin

L~cwken~io

19. 70.

7 I. 22.

23.

Inhibitory

Fuctor

34

for DA cells/leukemia inhibitory factor/differentiation inhibitory activity secreted by a T lymphoma cell line. J Biol Chew. 1989; 264: 21509. Baumann H, Wong GG. Hepatocyte-stimulating factor-III shares structural and functional identity with leukemia inhibitory factor. J Immunol. 1989; 143: 1163. Baumann H. Jahreis GP, Sauder DN. Koj A. Human keratinocytes and monocytes release factors which regulate the synthesis of major acute phase plasma proteins in hepatic cells from man. rat and mouse. J Biol Chm. 1984: 259: 7331. Robertson EJ. In: Robertson EJ ed. Teru~ocurcinotnas und emhrwnic, .stcw~ c,ells--11 prucrkal uppro~~cl~. Oxford. Washington DC: IRL Press; 1987: 71. Smith AG. Heath JK. Donaldson DD. Wong GG. Moreau J. Stahl M. Rogers D. Inhibition of pluripotent stem cell differentiation by purified polypeptides. Nurtrre 1988; 326. 19’. Smith GA. Hooper ML. Buffalo rat liver cells produce a diffusible activity which inhibits the differentiation of murine embryonal carcinoma and embryonic stem cells. &II Biol. 1987: 121.

24. Heath JK. Smith AG, Hsu LW. Rathjen PD. Growth and differentiation factors ofpluripotential stem cells. J Ccl/ Sci Suppl. 1990; 13: 75. 25. Rathjen PD. Nichols J, Toth S. Edward DR. Heath JK. Smith AG. Developmentally programmed induction ofdifferentiation inhibiting activity and the control ofstem cell populations. Genes Der. 1990: 4: 2308. 26. Koopman P. Cotton RGH. A factor produced by feeder cells which inhibits embryonal carcinoma cell dilferentiation: characterization and partial purification. E.up Cell Re.s. 1984; 154: I I I, 27. Yamamori T, Fukada K. Aebersold R, Korsching S, Fann M-J, Patterson PH. The cholinrrgic neuronal differentiation factor from heart cells is identical to leukemia inhibitory factor. .%iencc 19X9: 246: 1412. 2X. Metcalf D. Gearing DP. Fatal syndrome in mice engrafted with cells producing high levels of leukemia inhibitory factor. Proc Nat1 Acud Sci USA. 1989; 86: 5948. 29. Metcalf D. Nicola NA. Gearing DP. Effects of injected leukemia inhibitory factor on hematopoietic and other tissues in mice. Blood 1990; 76: 50. 30. Mori M. Yamaguchi K. Abe K. Purification of a lipoprotein lipase-inhibiting protein produced by a melanoma cell line associated with cancer cachexia. Biochent Biophy Res Conmun. 1989; 160: 1085. 31. Horton JE. Raisz LG. Simmons HA, Oppenheim JJ. Meyerhager SE. Bone resorbing activity in supernatant fluid from cultured human peripheral blood leukocytes. S&rice 1972; 177: 793. 32. Martin TJ. Ng KW, Nicholson GC. Cell biology of bone. C/in Endow Mrfah. 1988; 2: I. 33. Tomida M. Yamamoto-Yamaguchi Y. Hozumi M. Purification of a factor inducing differentiation of mouse myeloid leukemia Ml cells from conditioned medium of mouse tibrohlast L929 cells. J Biol C/wrrr. 198X: 259: 10978. 34. Abe E. Tanaka H, Ishimi Y. Miyaura C. Hayashi T. Nagasawa H. Tomida M. Yamaguchi Y. Hozumi M, Suda T. Differentiation-inducing factor purified from conditioned medium of mitogen treated spleen cell cultures stimulates bone resorption. Proc Narl.4cud Sci LiSA. 1986; 83: 595X. 35. Abe E. Ishimi Y. Takahashi N, AkatsuT. Ozawa H, Yamana H, Yoshiki S. Suda T. A differentiatmninducing factor produced by the osteoblastic cell line MC3T3-El stimulates bone resorption by promoting osteoclast formation. J Bone Min Rw. 1988: 3: 635. 36. Lowe DG. Nunes W. Bombara M, McCabe S, Ranges GE. Henzel W, Tomida M. YamamotoYamaguchi Y, Hozumi M. Goeddel DV. Genomics of cloning and heterologous expression of human differentiation stimulating factor (leukemic inhibitory factor. human interleukin DA). DN,4 1989; X: 351. 37. Ciearmg DP. Leukemia inhibitory factor: does the cap fit? Ann NY Ac,crd Sci. 1990; 628: 9. 3X. Metcalf D. The leukemia inhibitory factor (LIF). Int J Cell ClorlinR 1991; 9: 95. 39. I orenzo JA. The role of cytokines in the regulation of local bone resorption. Crit Rev Inrn~uno/. 1991. I I: 195. 40. L uben RA. Munday GR. Trummel CL, Raisz LG. J C/in Invesr. 1974: 53: 1473. 41. Iiorowitz M, Vignery A, Gershon RK, Baron R. Proc Nor/ Acad Sri USA 1984; 81: 2181. 42. ,tokine 1990: 2: 266. 56. Pfeilschilfter J. Seyedin SM. Munday CR. Transforming growth factor beta inhibits bone resorption in fetal long bone cultures. /C/in Invest. 1988: 76: 2016. 57. Ibbotson KJ, Harrod J, Gowen M. D’Souza S, Smith DD, Winkler ME. Derynck R. Mundy CR. Human recombinant transforming growth factor alpha stimulates bone resorption and inhibits formation in vitro. Proc NutI Amd Sci USA. 1986; 83: 2228. 58. Stern PH, Kriefger NS, Nissenson RA. Williams RD. Winkler ME, Derynck R. Strewler GJ. Human transforming growth factor alpha stimulates bone resorption in vitro. J C/in Invest. 1985; 76: 20 16. 59. Tashjian AH, Voelkel EF, Lazzaro M. Goad D. Bosma T. Levine L. Tumor necrosis factor alpha (cachectin) stimulates bone resorption in mouse calvaria via prostaglandin mediated mechanism. Endocrinology 1987; 120: 2029. 60. Stashenko P, Dewhirst FE, Peros WJ, Kent RL. Ago JM. Synergistic interactions between interleukin 1, tumor’necrosis factor and lymphotoxin in bone resorption. J Inmunol. 1987; 138: 1464. 61. Scheven BAA, Kawilarang-de Haas WM. Wassenaar A. Nijweide PJ. Differentiation kinetics of osteoclasts in the periosteum of embryonic bones in rive and in vitro. Anut Rec. 1986: 214: 418. 62. Van Beek E, Van der Ruit M. Papapoulos SE, Nicola N. Lowik C. Leukemia inhibitory factor (mLIF) inhibits bone resorption by blocking osteoclast formation and inhibits mineralization in bone culture. J Bow Miner Res. 1991: 6 (Suppl. I): S264 (abstract 719). 63. Van Beek E. Van der Wee-Pals L, Van de Ruit M, Nijweide P. Papapoulos S, Lowik C. Leukemia inhibitory factor inhibits osteoclastic resorption. growth, mineralization and alkaline phosphatase activity in mouse metacarpal bones, J Bone Mitter Rev. 1993: 8: 193. 64. Allen EH. Hilton DJ, Brown MA, Evely RS, Yumita S. Metcalf D. Cough NM, Ng KW. Nicola NA. Martin TJ. Osteoblasts display receptors for responses to leukemia inhibitory factor. J Cell Physiol. 1990; 145: 110. 65. Hilton DJ. Nicola NA. Metcalf D. Specific binding ofmurine leukemia inhibitory factor to normal and leukemic monocytic cells. Proc Nat/ Arud &i USA. 1988; 85: 597 I. 66. Shinar DM. Sato M, Rodan GA. The effect of hemopoietic growth factors on the generation of osteoclast-like cells in mouse bone marrow. Endocrinology 1990; 126: 1728. 67. Van der Pluijm G. Most W. Van der Wee-Pals L. de Groot H, Papapoulos S. Lowik C. Two distinct effects of recombinant human tumor necrosis factor-a on osteoclast development and subsequent resorption of mineralized matrix. Endocrinolog~~ 1992: 129: 1596.

6X. Lorenzo JA, Raise LG. Hock JM. DNA synthesis is not necessary for osteoclastic responses to parathyroid hormone in fetal rat long bones. J C/in Inrest. 1983; 72: 1924. 69. Holtrop ME. Raise LG. Comparison of the effects of 1,25-dihydroxycholecalciferol. prostdglandin E and osteoclast activating factor with parathyroid hormone on the ultrastructure of osteoclasts in cultured long bones of fetal rats. Calclf 7’i.w~ In!. 1979; 29: 201. 70. Roodman GD, Ibbotson KL. MacDonald BR, Kuehl TJ, Mundy CR. I .25-hydroxyvitamin D, causes formation of multinucleated cells with several osteoclast characteristics in cultures of primate marrow. Prt~c Nat/ Acud %I USA. 1985: 82: 8213. 71. Lowik CWGM. Van der Pluijm G. Bloys H, Hoekman K, Bijvoet OLM, Aarden LA, Papapoulos SE. Pat-athyroid hormone (PTH) and PTH-like protein (PLP) stimulate interleukin-6 production by osteogenic cells: A possible role of interleukin-6 in osteoclastogenesis. Biochrm Bi&r.r Rrs Commun. 19X9: 72.

73. 74. 75. 76.

77.

78. 79. X0.

162:

1546.

Owen TA, Aronow M, Shalhoub V, Barone LM, Wilming L, Tassinari MS, Kennedy MB. Pockwinse S. Lian JB, Stein GS. Progressive development of the rat osteoblast phenotype iw vitro’ reciprocal relationship in expression of genes associated with osteobtast proliferation anti ditferentiation during formation of the bone extracellular matrix. J Ccl/ Physioi. 1990; 143: 420. Falla N. Van Vlasselaer P, Bierkens J. Borremans B. Schoeters G. Van Gorp U. Characterization of a S-lluorouracil enriched osteoprogenitor population of the murine bone marrow; submitted. Lowe C. Cornish J, Callon K. Martin TJ. Reid IR. Regulation of osteoblast proliferation by leukemia inhibitory factor. J Bane Miner Rex. 1991; 6: 1277. Bellows CG. Aubin JE. Determination of numbers of osteoprogenitors present in isolated fetal rat caivaria cells ;,I rirro. Dcv Biol. 1989; 133: 8. Rodan SB, Wesolowski G. Hilton DJ. Nicola NA, Rodan GA. Leukemia Inhibitory factor binds with high affinity to preosteoblastic RCT-I cells and potentiates the retinoic acid induction of alkaline phosphatase. E~rdocrinology 1990; 127: 1602. Noda M. Vogel RL, Hasson DM. Rodan GA. Leukemia inhibitory factor suppresses proliferation. alhaline phosphatase activity, and type I collagen messenger ribonucleic acid level and enhances ostcopontin mRNA level in murine osteoblast-like (MC3T3EI) cells. Endacrinolo~~ 1990; 127: 185. Sudo 1-I. Kodama H. Amagai Y. Yamamoto S. Kasai S. In vifro differentiation and calcification of a nsw clona) osteogenic cell line derived from newborn mouse calvaria. J Cell Biol. 1983: 96: 191. Centrella M, Massdgue J, Canalis E. Human platelet-derived transforming growth factor-/3stimulates parameters of bone growth in fetal rat calvariae. Endocrinology 19X6; I 19: 2306. Centrella M. McCarthy TL. Canalis E. Transforming growth factor p is a bifunctional regulator of replication and collagen synthesis in osteoblast-enriched cell cultures from fetal rat bone. J Biol Chcv~. 1%7;

262:

2869.

XI. Noda M. Rodan GA. Type-0 transforming growth Factor inhibits the expression of alkaline phosphatase in murine osteoblast-like cells. Biochem Biaphy.\ Re.s Commun. 1986: 140: 56. X2. Koda M, Rodan GA. Type-p transforming growth factor regulation of alkaline phosphatase expresston and other phenotype-related mRNAs in osteoblast rat osteosarcoma cells, J CPII Phr.vro/. 1987: 133: 426. X3. Pfeilschifter J. Munday GR. Modulation of type /I transforming growth factor activity in boric cultures. Proc Nat/ Acad Sci USA. 1987; 84: 2024. X4. Crntrella M. McCarthy TL. Canalis E. Skeletal tissue and transforming growth factor fl. FASEB. 19Xx: 2, 3066. 85.

86.

87.

XX.

89.

Reinholt FP. Hultenby K. Oldberg A. Heinegard D. Osteopontin -a possible anchor of osteoclasts to bone. Proc NutI .4cud Sci USA. 1990; 87: 4473. Van der Pluijm G, Mouthaan H. de Groot H, Papapoulos S, Lowik C. The effects of synthetic RGDpeptides on osteoclastic resorption in three resorption assays characterized by different stages of o\teoc)ast development. Submitted. Ishimi S. Abe E. Tanaka H. Suda T. Synthesis of colony stimulating factors (CSF) and differentiationinducrng factor (D-factor) by osteoblastic cells, clone MC3T3-El. Biochem Biophys Commun. 1986: 134: 400. Evans DB. Smith AG, Williams MM. Rathjen PD. Heath JK. Gowen M. Production of leukemia inhibitory factor (LIF) by human bone cells irz vitro and its regulation by cytokines. Ca[clfTi,s.vue hr(. 1990: 46 (Suppl. 2): A34. Marusic A. Kalinowski JF. Lorenzo JA. Regulated production of leukemia inhibitory factor mRNA and bmactivity by hone cells. J Bone Miner Res. 1990; 5 (Suppl. I): Sl52.

352

P. Van

Vlasseher

90. Owen ME. Lineage of osteogenic cells and their relationship to the stromal system, Bone Miner Res. 1980; 3: 1. 91. Friedenstein AJ. Precursor cells of mechanocytes. Int Rev Cytol. 1976; 47: 327. 92. Ashton BA, Allen TD, Howlett CR, Eaglesom CC, Hattori A. Owen ME. Formation of bone and cartilage by marrow stromal cells in diffusion chambers in vivo. Clin Orrhop. 1980; 151: 294. 93. Van Vlasselaer P. Van den Heuvel R. Borremans B. Leukemia inhibitory factor (LIF) inhibits osteogenic commitment mouse bone marrow stroma. In preparation. 94. Dexter TM, Garland J, Scott D. Scolnick E, Metcalf D. J Exp Med. 1980; 152: 1036. 95. Metcalf D. Gearing DP. Fatal syndrome in mice engrafted with cells producing high levels of the leukemia inhibiting factor. Proc Nat/ Acad Sci USA. 1989; 86: 5948. 96. Hilton DJ, Nicola NA, Waring PM. Metcalf D. Clearance and fate of leukemia inhibitory factor after injection into mice. J CeN Physiol. 1991; 148: 430. 97. Metcalf D, Nicola NA, Gearing DP. Effects of injected leukemia inhibitory factor on hematopoietic and other tissues in mice. Blood 1990; 76: 50. 98. Duhrsen U, Metcalf D. Leukemia 1988; 2: 329. 99. Gallatin WM, Weissman IL, Butcher EC. A cell surface molecule involved in organ specific homing of lymphocytes. Nature 1983; 304: 30. 100. Oliff A. Defea-Jones D, Boyer M. Martinez D, Kiefer D. Vuocolo G, Wolfe A, Socher SH. Tumors secreting human TNFjcachectin induce cachexia in mice. CeN 1987: 50: 555. 101. Black K, Garrett R, Munday GR. Chinese hamster ovarian cells transfected with the murine IL-6 gene cause hypercalcemia as well as cachexia, leukocytosis and thrombocytosis in tumor bearing nude mice. Endocrinology 199 1; 128: 2657. 102. Metcalf D, Gearing DP. A myelosclerotic syndrome in mice engrafted with cells producing high levels of leukemia inhibitory factor. Leukemia 1989; 3: 847. 103. Rathjen PD, Toth S. Willis A, Heath JK, Smith AG. Differentiation inhibiting activity is produced in matrix-associated and diffusible forms that are generated by alternate promoter usage. Ceil 1990: 62: 1105. 104. Layton MJ, Cross BA, Metcalf D. Ward LD. Simpson RJ. Nicola NA. A major binding protein for leukemia inhibitory factor in normal mouse serum: Identification as a soluble form of the cellular receptor. Proc Nat/ Arad Sci USA. 1992: 89: 8616. 105. Foldes J, Naparstek E, Statter M, Menczel J. Bab I. Osteogenic response to marrow aspiration: increased serum osteocalcin and alkaline phosphatase in human bone marrow donors. J Bone Miner Res. 1989; 4: 643. 106. Rohlich K. On the relationship between the bone substance and hemopoiesis in the bone marrow. Z Mikrosk-Anat Forsch. 1941; 49: 425. 107. Steinberg B, Hufford V. Development of bone marrow in adult animals, Arch Pa/h. 1947; 43: 117. 108. Branemark PI. Breine U, Johansson B, Roylance PJ. Rockert H. Yoffey JM. Regeneration of bone marrow: A clinical and experimental study following removal of bone marrow by curretage. Acta Anat. I B~r.~l/ 1964; 59: 1. 109. Amsel S, Maniatis A. Tavassoli M, Crosby WH. The significance of intramedullary cancellous bone formation in the repair of bone marrow tissue. Anat Rec. 1969: 164: 101. 110. Patt HM, Maloney MA. Reconstitution of bone marrow in a depleted medullary cavity. In: Stohlman F Jr, rd. Hemopoietic cellularprol~/tiration, New York: Grune and Stratton; 1970: 56. 1 Il. Patt HM, Maloney MA. Bone marrow regeneration after local injury. f??.~p Hemut. 1975; 3: 135. 112. Klassen LW, Birks J, Allen E, Gurney CW. Experimental medullary aplasia. J Luh Clin Med. 1972; 80: 8. 113. Wetzler M, Talpaz M. Lowe DG, Baiocchi G, Gutterman JU. Kurzrock R. Constitutive expression of leukemia inhibitory factor RNA by human bone marrow stromal cells and modulation by IL- I, TNF-a and TGF-/X Esp Hemat. 1991; 19: 347. 114. Marks SC, Lane PW. Osteopetrosis. a new recessive skeletal mutation on chromosome 12 of the mouse. J Hered. 1976: 67: 11. 115. Marks SC. Morphological evidence for reduced bone resorption in osteopetrotic (op) mice. Am J.4nut. 1982; 163: 157. 116. Wiktor-Jedrzejczak W. Ahmed A, Szczylik C. Skelly RR. Hematological characterization of congenital osteopetrosis in op/op mice. J E.xp Med. 1982; 156: 15 16. 117. Wiktor-Jedrzejczak W. Skelly RR, Ahmed A. In: Gerschwin ER. Merchant B, eds Immunological def~~t.v in iahorator!* animals. New York. Plenum; 198 1: 5 I.

I IX. Yoshida H. Hayashi S. Kunisada T. Ogawa M. Nishikawa S, Okamura H. Sudo T. Shultz LD. Nishikawa S. The murine mutation osteopetrosis is in the encoding region of the macrophagc stimulating factor gene. Naruue 1990: 345: 442. I I9 Wlktor-Jedrzejczak W, Bartocci A. Ferrante AW. Ahmed-Ansari A. Sell KW. Pollard JW. Stanley ER. Total absence of colony stimulating factor I in the macrophage deficient osteopetrotic (opojp) mouse. Prrv .Ntrt/ .4~d Sci L:SA. 1990: 87: 4828. 170. Felix R. Cccchini MC. Fleisch H. Macrophage colony stimulating factor restores in riro bone resorption in the q’op osteopetrolic mouse. Endocrir~olog~ 1990; 127: 2592. I2 I, Thomas KR. Capecci MR. Site directed mutagenesis by gene targeting in mouse embryo-derived stem cells. C’rll 19x7: 51: 503. 172. Stewart CL, Kaspar P. Brunnet LJ, Bhatt H. Gadi I. Kontgen F. Abbondanzo SJ. Blastocqst implantation depends on maternal expression of leukemia inhibitory factor. Nnrurr 1992; 359: 76. 123. Ctmquet F. Brulet P. Developmental expression of myeloid leukemia inhibitory factor gene in prrimplantation blastocysts and in extraembryonic tissue of mouse embryo. hfo/ Cc// Biol. 1990: IO: 3x0 I. 1’4. Murray R. Let F. Chiu CP. The genes for leukemia inhibitory factor and IL-6 are expressed m mouse hiastocysts prior to the onset of hemopoiesis. Mel Cell Biol. 1990; IO: 4953. 12.5. Lotz M. Moats T, Williger PM. Leukemia inhibitory factor is expressed in cartilage and synovium and can contribute to the pathogenesis of arthritis. J C/in In~jest. 1992; 90: 888. 126. Guerne PA. Zuraw BL. Vaughan JH. Carson DA. Lotz M. Synovium as a source of interleukin 6 1,~ UO’O: contribution to local and systemic manifestations of arthritis. J C/in Inwrr. 1989: 83: 585. 127. Hirano T. Matsuda T, Turner M, Miyasaka N. Buchan C, Tang B. Sato K. Shimizu M. Maini R. Feldman M, Kishimoto T. Excessive production of interleukin 6 B cell stnnulatory factor-2 In rheumatoid arthritis. E~rr ./ h,~n~urzo/. 1988: 18: 1797. 12X. Scit7 M. Dcwald 9. Gerber N. Baggiolini M. Enhanced production of neutrophil-activating peptide- I interleukin X in rheumatoid arthritis. J C/Cl fnt~est. 1991; 87: 463. 129. Lotr M. Tcrkeltaub R. Villiger P. Cartilage and joint inflammation: expression of IL-8 in response to pcptide regulatory factors and proinflammatory agents. J li~~nn~~o/. 1992: 148: 466. 130. Villiger P. Terkeltaub R. Lotz M. Monocyte chemoattrdctant protein- I (MCP- I ) expression in human articular cartilage: induction by peptide regulatory factors and differential effects of dexamethasonc and rctinoic acid. J C’lir~ I~~~c,.ct. 1992: 90: 488. 131. Mizel SB. Daycr JM. Krane SM. Mergenhagen SE. Stimulation of rheumatoid synovlal cell collagcnase and prostaglandin production by partially purified lymphocyte activating factor (Intcrleukin-I ). Proc, Nurl AudSci USA. 1981: 78: 2474. 132. Smith JB. Bocchieri MH, Sherbin-Allen L. Borofsky M, Abruzzo J. Occurrence of intcrleukin-I 111 human synovial Ruid: detection by RIA, bioassay and presence of bioassay inhibiting f;lctor\. Hlicwrlcr/o/ //I/. 19x9; 9: 53. 133. FastgatcJA. Symonds JA. Wood NC, Grinlinton FM. Di Giovine FS. Duff GW. Correlation ofplasma intrrleukin I levels with disease activity in rheumatoid arthritis. Lance/ 1988; ii: 706. 134. I)aycr JM. Beutler 9. Cerami A. Cachcctin:tumor necrosis factor stimulates collagenase and prostaglandin E production by human synovial cells and dermal tibroblasts. J Erp Mcll. 1985: 167: 2163. 135. I)iGiovine FS. Nuki G. Duff GW. Tumor necrosis factor in synovial exudates. .3rlrz Rlrcwn~ Di.\. 19xX: 17: 76X. 136. Saklatvala J. Tumor necrosis factor alpha stimulates resorption and Inhibits synthesis of proteoglycan ln culture. ~‘v’crture 1986: 322: 547. 137. Lc J. Vilcek J. Tumor necrosis factor and interleukin I. Lah Inwsr. 19x7: 56: 234. 138. I.ccron LC, Robvlot P. Chevalier S. Morel F, Alderman E, Gombert J. Gascan H. High circulating Icvels of leukemia inhibitory factor in patients with giant cell arteritis: independent regulation of LlF :Ind IL-6 under corticosteroid therapy. C/in E\-p I!nn~ur~o/. 1993; accepted.

Leukemia inhibitory factor (LIF): a growth factor with pleiotropic effects on bone biology.

Historically, growth factors are denominated based on a specific biological activity. In many cases, these factors display a much broader spectrum of ...
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