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Polycystic kidney disease in Sprague-Dawley rats Ahmed Shoieb, Norimitsu Shirai ∗ Drug Safety Research and Development, Pfizer Worldwide Research & Development, Groton, Connecticut, USA
a r t i c l e
i n f o
Article history: Received 8 October 2014 Accepted 12 February 2015 Keywords: Sprague-Dawley rat Polycystic kidney disease Kidney Liver Histopathology
a b s t r a c t Polycystic kidney disease (PKD) is a cystic genetic disorder of the kidneys which is typically associated with cystic bile duct dilatation in the liver in humans, and domestic and laboratory animals. In humans, there are two types of PKD, autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). ADPKD is caused by mutations in PKD1 or PKD2 gene while ARPKD is caused by mutation or loss of the PKHD1 (polycystic kidney and hepatic disease 1) gene. Here we report a morphologically confirmed case of spontaneous PKD in a Sprague-Dawley rat in which anatomic pathology examination revealed numerous cystic changes in the kidney and liver. Lesions consisted of marked cystic dilatations of renal tubules, and moderate cystic dilatations of intrahepatic bile ducts with portal fibrosis. We present detailed histologic features of the spontaneous PKD and compare them with disease model rats carrying an autosomal recessive PKHD 1 gene mutation. © 2015 Published by Elsevier GmbH.
1. Introduction Polycystic kidney disease (PKD) is a cystic genetic disorder of the kidneys which has been associated with cystic bile ducts, bile duct proliferation, and/or cystic pancreatic ducts. In humans, there are two types of PKD: autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). ADPKD is caused by mutations in one of two genes, PKD1 or PKD2, while ARPKD is caused by mutation or loss of the PKHD1 gene (Ward et al., 2002; Torres et al., 2007). In the more common form, ADPKD, the renal parenchyma is extensively replaced by cysts that originate from all segments of the nephron, collecting tubules, and ducts. In humans with ADPKD, there is an association with cysts in other organs, most often the liver. Other abnormalities that can be coupled with ADPKD include cardiac valvular anomalies, intracranial aneurysms, and colonic diverticula. In ARPKD, cysts arise from only dilated collecting tubules and ducts and in most cases there is also intrahepatic biliary cysts and hepatic fibrosis (Flaherty et al., 1995; Martinez and Grantham, 1995). In animals, familial/hereditary PKD has been recognized in many species including dogs, goat, mouse, and rats (Katsuyama et al., 2000; Krotec et al., 1996; O’Leary et al., 1999; Takahashi et al., 1986). The potential utility of an animal model of human
∗ Correspondence to: Drug Safety Research and Development, Pfizer Worldwide Research & Development, 445 Eastern Point Road, MS 8274-1221, Building 274, Office 1703G, Groton, CT 06340, USA. Tel.: +1 860 686 4183; fax: +1 860 686 0557. E-mail address: norimitsu.shirai@pfizer.com (N. Shirai).
diseases depends on how well it mimics the disease as well as genetic uniformity, reproduction rate, cost, etc. A rat model of ARPKD derived from Sprague-Dawley strain has shown PKD with an autosomal-recessive inheritance pattern and hepatic involvement in the disease, which resembles human condition (Katsuyama et al., 2000; Kai et al., 2001; Sanzen et al., 2001). The rat ARPKD model originally stems from a spontaneous mutation in a strain of Sprague-Dawley rat (Katsuyama et al., 2000). This report characterizes the morphologic features of a spontaneous PKD in a Sprague-Dawley rat and compares its morphology with Sprague-Dawley rat model of ARPKD carrying an autosomal recessive PKHD1 gene mutation. 2. Materials and methods 2.1. Animals The animal with spontaneous PKD was a 14 weeks old, male, Sprague-Dawley rat (Crl:CD® [SD]) allocated to a control group administered a vehicle (0.02% polysorbate 80, 0.66 mL/kg) via the tail vein once every other week for a 7-week non-clinical toxicity study. During the study, clinical signs were observed daily. Standard hematology (red blood cell mass parameters, reticulocytes, white blood cells, white cell differential, and platelets) and serum chemistry (blood urea nitrogen, creatinine, sodium, chloride, phosphorus, potassium, calcium, total protein, albumin, globulin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyl transferase, total bilirubin, glucose, and cholesterol) examinations were conducted. For
http://dx.doi.org/10.1016/j.etp.2015.02.002 0940-2993/© 2015 Published by Elsevier GmbH.
Please cite this article in press as: Shoieb A, Shirai N. Polycystic kidney disease in Sprague-Dawley rats. Exp Toxicol Pathol (2015), http://dx.doi.org/10.1016/j.etp.2015.02.002
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Table 1 Incidence and severity of cystic changes in the kidney and liver. ARPKD model Organ Finding Severity
Total No. examined
+ ++ +++ ++++
Spontaneous PKD
Kidney Cystic tubules
Liver Cystic bile ducts
Kidney Cystic tubules
Liver Cystic bile ducts
1 (3.3%) 14 (46.7%) 15 (50.0%) – 30 30
– 24 (80%) 6 (20%) – 30 30
– – – 1 1 1
– – 1 – 1 1
comparison of morphologic tissue abnormalities, 30 male ARPKD model rats homozygous for mutation at the PKHD1 locus (PCK/CrljCrl-Pkhd1pck/CRL) were used. The ARPKD model rats ranged in age from 23 to 26 weeks old. All procedures performed on animals were in accordance with regulations and established guidelines, and were reviewed and approved by the Pfizer Institutional Animal Care and Use Committee. 2.2. Tissue preparation Tissue samples from kidney and liver were collected in 10% neutral buffered formalin. Tissues were trimmed, embedded in paraffin, sectioned at approximately 5 m, and stained with hematoxylin and eosin (H&E).
cysts in the outer medulla (Fig. 1). The liver was slightly enlarged and had an irregular surface (Fig. 2) which corresponded with spaces, similar to those seen in the kidneys, when sectioned. There were no gross abnormalities in other organs or tissues. Histologically, both the renal cortex and medulla contained numerous dilated tubules (cysts) lined by a variably squamous to cuboidal to columnar epithelium, with more predominant cystic tubular dilatation in the outer medulla (Fig. 3). Renal lesion was graded as marked, i.e., the dilated (cystic) tubules occupied approximately 90% area of the outer medulla and widely extended to the cortex. The cortex, however, was less severely (50–60% of the cortex) affected than medulla. Many of these cysts were distended by pale amphophilic fluid admixed with necrotic cellular debris, scant macrophages, and/or degenerate neutrophils. Between the cysts, some areas of the interstium were expanded by loose connective
2.3. Grading system for lesions in the kidney and liver Cystic lesions in the kidney and liver were graded by microscopic examination to obtain a comprehensive assessment of the severity based on the following semi-quantitative grading scheme, which was modified from Kai and others (Kai et al., 2001). Kidney - Marked (++++) = Presence of numerous large cystic (dilated) tubules, which occupy greater than 75% area of the outer medulla and widely extend over the cortex. - Moderate (+++) = Presence of several large cystic (dilated) tubules, which occupy 51–75% area of the outer medulla and often extend to the inner cortex. - Mild (++) = Same as moderate, but 26–50% of the outer medulla was occupied by the cystic tubules. - Minimal (+) = Presence of a few smaller cystic tubules occupying up to 25% area of the outer medulla. Liver
Fig. 1. Spontaneous PKD rat. Kidneys. Multiple cysts involving most of the renal parenchyma with predominant large cysts in the outer medulla.
- Moderate (+++) = Presence of cystic structures which were divided into variable-sized compartments, and several cystic structures were dilated up to the size of several liver lobules. - Mild (++) = Presence of variable-sized cystic structures which were up to the size of one liver lobule. 3. Results A summary of microscopic observations is presented in Table 1. 3.1. A spontaneous PKD The rat was clinically normal. There were no abnormalities in hematology or serum chemistry parameters. At necropsy, both kidneys were moderately enlarged and when sectioned contained multiple, variably-sized (up to 3.0 mm diameter), fluid-filled spaces involving most of the renal parenchyma with predominant larger
Fig. 2. Spontaneous PKD rat. Liver with granulated surface.
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Fig. 3. Spontaneous PKD rat. Kidney. Large cysts arising from collecting ducts in the outer medulla, and to a lesser extent in cortex. H&E. Original magnification: 6×.
tissue which often contained a few residual tubules of relatively normal caliber and/or a mixed inflammatory cell infiltrate. Occasional glomeruli had a slightly thickened basement membrane and the urothelium was slightly thickened. In the liver, there were multiple individual to coalescing spaces (cystic dilatations of bile ducts) that were lined by variably attenuated cuboidal epithelial cells and surrounded by a band of collagenous tissue (Fig. 4). Cysts were often distended up to the size of several liver lobules (moderate). In the adjacent hepatic parenchyma, there was slight atrophy of hepatic cords, and minimal mixed inflammatory cell infiltrate in periportal regions as well as proliferation of portal bile ducts. 3.2. ARPKD model rats (PCK/CrljCrl-Pkhd1pck/CRL) Renal lesion of this rat model was characterized primarily by the presence of expansively dilated collecting tubules (cystic tubules) in the outer medulla (Fig. 5), ranging in severity from minimal to moderate. This change was often accompanied by dilatation of the cortical tubules. The degree of these cortical changes was generally correlated with the extent of the medullary lesion. Hepatic lesions were characterized by variable-sized cysts consisting of dilated intrahepatic bile ducts, with varying degrees of fibrosis. The cysts were primarily lined by a single layer of flattened or low cuboidal cells. The hepatic lesions were graded as mild or moderate. In the
Fig. 4. Spontaneous PKD rats. Liver. Multiloculated cysts arising from bile ducts, with varying degrees of fibrosis. Cysts are often distended up to the size of several liver lobules. H&E. Original magnification: 20×.
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Fig. 5. ARPKD rat model. Kidney. Large cysts arising from collecting ducts in the outer medulla with a local cortical involvement showing a radial distribution pattern. Approximately a 70% area of the outer medulla is affected. H&E. Original magnification: 6×.
moderate lesions, cystic structures were divided into small to large compartments (multiloculated biliary cysts), and several cysts were distended up to the size of several liver lobules (Fig. 6). Also cysts were often accompanied by fibrosis, proliferation of bile ducts and chronic active inflammation in portal regions. 4. Discussion Remarkable cystic dilatation of collecting tubules in the outer medulla of the kidney was a characteristic feature of ARPKD model rats (PCK/CrljCrl-Pkhd1pck/CRL) carrying an autosomal recessive PKHD1 gene mutation, suggesting that cysts arise from collecting ducts in this model as in humans with ARPKD (Martinez and Grantham, 1995). Also, as in human ARPKD, biliary cystic dilatation was consistently noted in the ARPKD model rats concurrently with the kidney lesion. Taken together, such pathologic condition indicates the advantage of this ARPKD model to mimic the human disease. Cortical tubular dilatation seen in the ARPKD model appeared to progress with cyst growth in the outer medulla since the involvement of cortical tubules was generally correlated with the extent of the medullary lesion. Microscopic observations in the current study were consistent with those previously reported in a
Fig. 6. ARPKD rat model. Liver. Multiloculated cysts arising from bile ducts, with varying degrees of fibrosis. Similar to Fig. 4. H&E. Original magnification: 20×.
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rat model of ARPKD which is a mutant derived from a colony of crj:CD rats (Katsuyama et al., 2000; Kai et al., 2001). To the best of author’s knowledge, there are two other welldocumented rat models of PKD: Lewis polycystic kidney (LPK) rat, and Hannover Sprague-Dawley (Han:SPRD) rat. The LPK rat is a spontaneous rat model of ARPKD, in which renal cysts arose predominantly from collecting ducts and to a lesser extent from cortical tubules. The LPK rat, however, lacks hepatic involvement (Phillips et al., 2007). PKD in the Han:SPRD rat has been shown to be inherited in an autosomal dominant fashion as in human ADPKD. Extrarenal manifestation seen in the Han:SPRD rat, however, did not match the human condition as well (Cowley et al., 1993). Interestingly, in the spontaneous PKD rat, cystic tubules in the outer medulla (collecting tubules) were more prevalent, and furthermore, dilated tubules were also more widely distributed over the cortex when compared to the rat model of ARPKD despite the spontaneous PKD rat was approximately 10 weeks younger than the disease model. Renal cysts have been shown to develop with age in PKD models in rats (Cowley et al., 1993; Sanzen et al., 2001) and mice (Flaherty et al., 1995). It was uncertain whether cortical tubular dilatations were primary as in ADPKD or secondary lesions. A potential mechanism of the latter case could be concomitant dilatations secondary to persistent urinary flow impairment as primary disturbances in the lower tubular system have been shown to result in passive dilatations of the upper tubules (Oliver et al., 1957). Caroli’s disease is an autosomal recessive, inherited liver disorder characterized by dilatation of the intrahepatic bile ducts, and is often associated with ARPKD (Taylor and Palmer, 1998; Torres et al., 2007). The above-mentioned mutant colony of crj:CD rats was found to also have polycystic lesions in the liver. Because this may represent an animal model of Caroli’s disease the liver lesions have been well characterized and studied. Hepatic lesions observed in ARPKD model rats as well as a rat with spontaneous PKD in the current study were histologically consistent with those reported in the mutant colony of crj:CD rats (Sanzen et al., 2001). Administration of glucocorticoid hormone at birth has shown to cause PKD in rabbits and hamsters (Perey et al., 1967; Filmer et al., 1973). In these disease models, cystic changes were restricted to the kidney, and the cystic changes primarily involved cortical tubules. In contrast, cysts predominated in the outer medulla and hepatic involvement was remarkable in the current spontaneous PKD. The involvement of multiple organs strongly suggested that the lesions resulted from a genetic process although supportive genetic analysis was not performed. Furthermore, spontaneously rare occurrence of this disorder in Sprague-Dawley rats likely implies inheritance as an autosomal recessive trait.
In conclusion, histologic features of a spontaneous PKD in a rat were characterized primarily by prominent cystic changes in the kidney and hepatic involvement. The pattern and nature of the lesions were similar to those in a rat model of ARPKD, although renal cysts were more prominent than the disease model. It is hoped that this report will help to facilitate the differentiation of spontaneous from induced changes in toxicology studies in Sprague-Dawley rats by providing an example of an unusual spontaneous lesion. References Cowley BD, Gudapaty S, Kraybill AL, Barash BD, Harding MA, Calvet JP, et al. Autosomal-dominant polycystic kidney disease in the rat. Kidney Int 1993;43:522–34. Filmer RB, Carone FA, Rowland RG, Babcock JR. Adrenal corticosteroid-induced renal cystic disease in the newborn hamster. Am J Pathol 1973;72: 461–72. Flaherty L, Bryda EC, Collins D, Rudofsky U, Montgomery JC. New mouse model for polycystic kidney disease with both recessive and dominant gene effects. Kidney Int 1995;47:552–8. Kai K, Sato N, Watanabe A, Shiraiwa K, Ogawa S, Kobayashi Y. Polycystic disease of the kidney and liver in Crj:CD(SD) rats. J Toxicol Pathol 2001;14:51–5. Katsuyama M, Masuyama T, Komura I, Hibino T, Takahashi H. Characterization of a novel polycystic kidney rat model with accompanying polycystic liver. Exp Anim 2000;49:51–5. Krotec K, Meyer BS, Freeman W, Hamir AN. Congenital cystic disease of the liver, pancreas, and kidney in a Nubian goat (Capra hircus). Vet Pathol 1996;33: 708–10. Martinez JR, Grantham JJ. Polycystic kidney disease: etiology, pathogenesis, and treatment. Dis Mon 1995;41:693–765. O’Leary CA, Mackay BM, Malik R, Edmondston JE, Robinson WF, Huxtable CR. Polycystic kidney disease in bull terriers: an autosomal dominant inherited disorder. Aust Vet J 1999;77:361–6. Oliver J, Macdowell M, Welt LG, Holliday MA, Hollander W, Winters RW, et al. The renal lesions of electrolyte imbalance. The structural alterations in potassiumdepleted rats. J Exp Med 1957;106:563–73. Perey DYE, Herdman RC, Good RA. Polycystic renal disease: A new experimental model. Science 1967;158:494–6. Phillips JK, Hopwood D, Loxley R, Ghatora K, Coombes JD, Tan YS, et al. Temporal relationship between renal cyst development, hypertension and cardiac hypertrophy in a new rat model of autosomal recessive polycystic kidney disease. Kidney Blood Press Res 2007;30:129–44. Sanzen T, Harada K, Yasoshima M, Kawamura Y, Ishibashi M, Nakanuma Y. Polycystic kidney rat is a novel animal model of Caroli’s disease associated with congenital hepatic fibrosis. Am J Pathol 2001;158:1605–12. Takahashi H, Ueyama Y, Hibino T, Kuwahara Y, Suzuki S, Hioki K, Tamaoki N. A new mouse model of genetically transmitted polycystic kidney disease. J Urol 1986;135:1280–3. Taylor AC, Palmer KR. Caroli’s disease. Eur J Gastroenterol Hepatol 1998;10:105–8. Torres VE, Harris PC, Pirson Y. Autosomal dominant polycystic kidney disease. Lancet 2007;369:1287–301. Ward CJ, Hogan MC, Rossetti S, Walker D, Sneddon T, Wang W, et al. The gene mutated in autosomal recessive polycystic kidney disease encodes a large, receptor-like protein. Nat Genet 2002;30:259–69.
Please cite this article in press as: Shoieb A, Shirai N. Polycystic kidney disease in Sprague-Dawley rats. Exp Toxicol Pathol (2015), http://dx.doi.org/10.1016/j.etp.2015.02.002
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Experimental and Toxicologic Pathology xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Experimental and Toxicologic Pathology journal homepage: www.elsevier.de/etp
Short Communication
Polycystic kidney disease in Sprague-Dawley rats Ahmed Shoieb, Norimitsu Shirai ∗ Drug Safety Research and Development, Pfizer Worldwide Research & Development, Groton, Connecticut, USA
a r t i c l e
i n f o
Article history: Received 8 October 2014 Accepted 12 February 2015 Keywords: Sprague-Dawley rat Polycystic kidney disease Kidney Liver Histopathology
a b s t r a c t Polycystic kidney disease (PKD) is a cystic genetic disorder of the kidneys which is typically associated with cystic bile duct dilatation in the liver in humans, and domestic and laboratory animals. In humans, there are two types of PKD, autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). ADPKD is caused by mutations in PKD1 or PKD2 gene while ARPKD is caused by mutation or loss of the PKHD1 (polycystic kidney and hepatic disease 1) gene. Here we report a morphologically confirmed case of spontaneous PKD in a Sprague-Dawley rat in which anatomic pathology examination revealed numerous cystic changes in the kidney and liver. Lesions consisted of marked cystic dilatations of renal tubules, and moderate cystic dilatations of intrahepatic bile ducts with portal fibrosis. We present detailed histologic features of the spontaneous PKD and compare them with disease model rats carrying an autosomal recessive PKHD 1 gene mutation. © 2015 Published by Elsevier GmbH.
1. Introduction Polycystic kidney disease (PKD) is a cystic genetic disorder of the kidneys which has been associated with cystic bile ducts, bile duct proliferation, and/or cystic pancreatic ducts. In humans, there are two types of PKD: autosomal dominant polycystic kidney disease (ADPKD) and autosomal recessive polycystic kidney disease (ARPKD). ADPKD is caused by mutations in one of two genes, PKD1 or PKD2, while ARPKD is caused by mutation or loss of the PKHD1 gene (Ward et al., 2002; Torres et al., 2007). In the more common form, ADPKD, the renal parenchyma is extensively replaced by cysts that originate from all segments of the nephron, collecting tubules, and ducts. In humans with ADPKD, there is an association with cysts in other organs, most often the liver. Other abnormalities that can be coupled with ADPKD include cardiac valvular anomalies, intracranial aneurysms, and colonic diverticula. In ARPKD, cysts arise from only dilated collecting tubules and ducts and in most cases there is also intrahepatic biliary cysts and hepatic fibrosis (Flaherty et al., 1995; Martinez and Grantham, 1995). In animals, familial/hereditary PKD has been recognized in many species including dogs, goat, mouse, and rats (Katsuyama et al., 2000; Krotec et al., 1996; O’Leary et al., 1999; Takahashi et al., 1986). The potential utility of an animal model of human
∗ Correspondence to: Drug Safety Research and Development, Pfizer Worldwide Research & Development, 445 Eastern Point Road, MS 8274-1221, Building 274, Office 1703G, Groton, CT 06340, USA. Tel.: +1 860 686 4183; fax: +1 860 686 0557. E-mail address: norimitsu.shirai@pfizer.com (N. Shirai).
diseases depends on how well it mimics the disease as well as genetic uniformity, reproduction rate, cost, etc. A rat model of ARPKD derived from Sprague-Dawley strain has shown PKD with an autosomal-recessive inheritance pattern and hepatic involvement in the disease, which resembles human condition (Katsuyama et al., 2000; Kai et al., 2001; Sanzen et al., 2001). The rat ARPKD model originally stems from a spontaneous mutation in a strain of Sprague-Dawley rat (Katsuyama et al., 2000). This report characterizes the morphologic features of a spontaneous PKD in a Sprague-Dawley rat and compares its morphology with Sprague-Dawley rat model of ARPKD carrying an autosomal recessive PKHD1 gene mutation. 2. Materials and methods 2.1. Animals The animal with spontaneous PKD was a 14 weeks old, male, Sprague-Dawley rat (Crl:CD® [SD]) allocated to a control group administered a vehicle (0.02% polysorbate 80, 0.66 mL/kg) via the tail vein once every other week for a 7-week non-clinical toxicity study. During the study, clinical signs were observed daily. Standard hematology (red blood cell mass parameters, reticulocytes, white blood cells, white cell differential, and platelets) and serum chemistry (blood urea nitrogen, creatinine, sodium, chloride, phosphorus, potassium, calcium, total protein, albumin, globulin, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma-glutamyl transferase, total bilirubin, glucose, and cholesterol) examinations were conducted. For
http://dx.doi.org/10.1016/j.etp.2015.02.002 0940-2993/© 2015 Published by Elsevier GmbH.
Please cite this article in press as: Shoieb A, Shirai N. Polycystic kidney disease in Sprague-Dawley rats. Exp Toxicol Pathol (2015), http://dx.doi.org/10.1016/j.etp.2015.02.002
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Table 1 Incidence and severity of cystic changes in the kidney and liver. ARPKD model Organ Finding Severity
Total No. examined
+ ++ +++ ++++
Spontaneous PKD
Kidney Cystic tubules
Liver Cystic bile ducts
Kidney Cystic tubules
Liver Cystic bile ducts
1 (3.3%) 14 (46.7%) 15 (50.0%) – 30 30
– 24 (80%) 6 (20%) – 30 30
– – – 1 1 1
– – 1 – 1 1
comparison of morphologic tissue abnormalities, 30 male ARPKD model rats homozygous for mutation at the PKHD1 locus (PCK/CrljCrl-Pkhd1pck/CRL) were used. The ARPKD model rats ranged in age from 23 to 26 weeks old. All procedures performed on animals were in accordance with regulations and established guidelines, and were reviewed and approved by the Pfizer Institutional Animal Care and Use Committee. 2.2. Tissue preparation Tissue samples from kidney and liver were collected in 10% neutral buffered formalin. Tissues were trimmed, embedded in paraffin, sectioned at approximately 5 m, and stained with hematoxylin and eosin (H&E).
cysts in the outer medulla (Fig. 1). The liver was slightly enlarged and had an irregular surface (Fig. 2) which corresponded with spaces, similar to those seen in the kidneys, when sectioned. There were no gross abnormalities in other organs or tissues. Histologically, both the renal cortex and medulla contained numerous dilated tubules (cysts) lined by a variably squamous to cuboidal to columnar epithelium, with more predominant cystic tubular dilatation in the outer medulla (Fig. 3). Renal lesion was graded as marked, i.e., the dilated (cystic) tubules occupied approximately 90% area of the outer medulla and widely extended to the cortex. The cortex, however, was less severely (50–60% of the cortex) affected than medulla. Many of these cysts were distended by pale amphophilic fluid admixed with necrotic cellular debris, scant macrophages, and/or degenerate neutrophils. Between the cysts, some areas of the interstium were expanded by loose connective
2.3. Grading system for lesions in the kidney and liver Cystic lesions in the kidney and liver were graded by microscopic examination to obtain a comprehensive assessment of the severity based on the following semi-quantitative grading scheme, which was modified from Kai and others (Kai et al., 2001). Kidney - Marked (++++) = Presence of numerous large cystic (dilated) tubules, which occupy greater than 75% area of the outer medulla and widely extend over the cortex. - Moderate (+++) = Presence of several large cystic (dilated) tubules, which occupy 51–75% area of the outer medulla and often extend to the inner cortex. - Mild (++) = Same as moderate, but 26–50% of the outer medulla was occupied by the cystic tubules. - Minimal (+) = Presence of a few smaller cystic tubules occupying up to 25% area of the outer medulla. Liver
Fig. 1. Spontaneous PKD rat. Kidneys. Multiple cysts involving most of the renal parenchyma with predominant large cysts in the outer medulla.
- Moderate (+++) = Presence of cystic structures which were divided into variable-sized compartments, and several cystic structures were dilated up to the size of several liver lobules. - Mild (++) = Presence of variable-sized cystic structures which were up to the size of one liver lobule. 3. Results A summary of microscopic observations is presented in Table 1. 3.1. A spontaneous PKD The rat was clinically normal. There were no abnormalities in hematology or serum chemistry parameters. At necropsy, both kidneys were moderately enlarged and when sectioned contained multiple, variably-sized (up to 3.0 mm diameter), fluid-filled spaces involving most of the renal parenchyma with predominant larger
Fig. 2. Spontaneous PKD rat. Liver with granulated surface.
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Fig. 3. Spontaneous PKD rat. Kidney. Large cysts arising from collecting ducts in the outer medulla, and to a lesser extent in cortex. H&E. Original magnification: 6×.
tissue which often contained a few residual tubules of relatively normal caliber and/or a mixed inflammatory cell infiltrate. Occasional glomeruli had a slightly thickened basement membrane and the urothelium was slightly thickened. In the liver, there were multiple individual to coalescing spaces (cystic dilatations of bile ducts) that were lined by variably attenuated cuboidal epithelial cells and surrounded by a band of collagenous tissue (Fig. 4). Cysts were often distended up to the size of several liver lobules (moderate). In the adjacent hepatic parenchyma, there was slight atrophy of hepatic cords, and minimal mixed inflammatory cell infiltrate in periportal regions as well as proliferation of portal bile ducts. 3.2. ARPKD model rats (PCK/CrljCrl-Pkhd1pck/CRL) Renal lesion of this rat model was characterized primarily by the presence of expansively dilated collecting tubules (cystic tubules) in the outer medulla (Fig. 5), ranging in severity from minimal to moderate. This change was often accompanied by dilatation of the cortical tubules. The degree of these cortical changes was generally correlated with the extent of the medullary lesion. Hepatic lesions were characterized by variable-sized cysts consisting of dilated intrahepatic bile ducts, with varying degrees of fibrosis. The cysts were primarily lined by a single layer of flattened or low cuboidal cells. The hepatic lesions were graded as mild or moderate. In the
Fig. 4. Spontaneous PKD rats. Liver. Multiloculated cysts arising from bile ducts, with varying degrees of fibrosis. Cysts are often distended up to the size of several liver lobules. H&E. Original magnification: 20×.
3
Fig. 5. ARPKD rat model. Kidney. Large cysts arising from collecting ducts in the outer medulla with a local cortical involvement showing a radial distribution pattern. Approximately a 70% area of the outer medulla is affected. H&E. Original magnification: 6×.
moderate lesions, cystic structures were divided into small to large compartments (multiloculated biliary cysts), and several cysts were distended up to the size of several liver lobules (Fig. 6). Also cysts were often accompanied by fibrosis, proliferation of bile ducts and chronic active inflammation in portal regions. 4. Discussion Remarkable cystic dilatation of collecting tubules in the outer medulla of the kidney was a characteristic feature of ARPKD model rats (PCK/CrljCrl-Pkhd1pck/CRL) carrying an autosomal recessive PKHD1 gene mutation, suggesting that cysts arise from collecting ducts in this model as in humans with ARPKD (Martinez and Grantham, 1995). Also, as in human ARPKD, biliary cystic dilatation was consistently noted in the ARPKD model rats concurrently with the kidney lesion. Taken together, such pathologic condition indicates the advantage of this ARPKD model to mimic the human disease. Cortical tubular dilatation seen in the ARPKD model appeared to progress with cyst growth in the outer medulla since the involvement of cortical tubules was generally correlated with the extent of the medullary lesion. Microscopic observations in the current study were consistent with those previously reported in a
Fig. 6. ARPKD rat model. Liver. Multiloculated cysts arising from bile ducts, with varying degrees of fibrosis. Similar to Fig. 4. H&E. Original magnification: 20×.
Please cite this article in press as: Shoieb A, Shirai N. Polycystic kidney disease in Sprague-Dawley rats. Exp Toxicol Pathol (2015), http://dx.doi.org/10.1016/j.etp.2015.02.002
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ARTICLE IN PRESS A. Shoieb, N. Shirai / Experimental and Toxicologic Pathology xxx (2015) xxx–xxx
rat model of ARPKD which is a mutant derived from a colony of crj:CD rats (Katsuyama et al., 2000; Kai et al., 2001). To the best of author’s knowledge, there are two other welldocumented rat models of PKD: Lewis polycystic kidney (LPK) rat, and Hannover Sprague-Dawley (Han:SPRD) rat. The LPK rat is a spontaneous rat model of ARPKD, in which renal cysts arose predominantly from collecting ducts and to a lesser extent from cortical tubules. The LPK rat, however, lacks hepatic involvement (Phillips et al., 2007). PKD in the Han:SPRD rat has been shown to be inherited in an autosomal dominant fashion as in human ADPKD. Extrarenal manifestation seen in the Han:SPRD rat, however, did not match the human condition as well (Cowley et al., 1993). Interestingly, in the spontaneous PKD rat, cystic tubules in the outer medulla (collecting tubules) were more prevalent, and furthermore, dilated tubules were also more widely distributed over the cortex when compared to the rat model of ARPKD despite the spontaneous PKD rat was approximately 10 weeks younger than the disease model. Renal cysts have been shown to develop with age in PKD models in rats (Cowley et al., 1993; Sanzen et al., 2001) and mice (Flaherty et al., 1995). It was uncertain whether cortical tubular dilatations were primary as in ADPKD or secondary lesions. A potential mechanism of the latter case could be concomitant dilatations secondary to persistent urinary flow impairment as primary disturbances in the lower tubular system have been shown to result in passive dilatations of the upper tubules (Oliver et al., 1957). Caroli’s disease is an autosomal recessive, inherited liver disorder characterized by dilatation of the intrahepatic bile ducts, and is often associated with ARPKD (Taylor and Palmer, 1998; Torres et al., 2007). The above-mentioned mutant colony of crj:CD rats was found to also have polycystic lesions in the liver. Because this may represent an animal model of Caroli’s disease the liver lesions have been well characterized and studied. Hepatic lesions observed in ARPKD model rats as well as a rat with spontaneous PKD in the current study were histologically consistent with those reported in the mutant colony of crj:CD rats (Sanzen et al., 2001). Administration of glucocorticoid hormone at birth has shown to cause PKD in rabbits and hamsters (Perey et al., 1967; Filmer et al., 1973). In these disease models, cystic changes were restricted to the kidney, and the cystic changes primarily involved cortical tubules. In contrast, cysts predominated in the outer medulla and hepatic involvement was remarkable in the current spontaneous PKD. The involvement of multiple organs strongly suggested that the lesions resulted from a genetic process although supportive genetic analysis was not performed. Furthermore, spontaneously rare occurrence of this disorder in Sprague-Dawley rats likely implies inheritance as an autosomal recessive trait.
In conclusion, histologic features of a spontaneous PKD in a rat were characterized primarily by prominent cystic changes in the kidney and hepatic involvement. The pattern and nature of the lesions were similar to those in a rat model of ARPKD, although renal cysts were more prominent than the disease model. It is hoped that this report will help to facilitate the differentiation of spontaneous from induced changes in toxicology studies in Sprague-Dawley rats by providing an example of an unusual spontaneous lesion. References Cowley BD, Gudapaty S, Kraybill AL, Barash BD, Harding MA, Calvet JP, et al. Autosomal-dominant polycystic kidney disease in the rat. Kidney Int 1993;43:522–34. Filmer RB, Carone FA, Rowland RG, Babcock JR. Adrenal corticosteroid-induced renal cystic disease in the newborn hamster. Am J Pathol 1973;72: 461–72. Flaherty L, Bryda EC, Collins D, Rudofsky U, Montgomery JC. New mouse model for polycystic kidney disease with both recessive and dominant gene effects. Kidney Int 1995;47:552–8. Kai K, Sato N, Watanabe A, Shiraiwa K, Ogawa S, Kobayashi Y. Polycystic disease of the kidney and liver in Crj:CD(SD) rats. J Toxicol Pathol 2001;14:51–5. Katsuyama M, Masuyama T, Komura I, Hibino T, Takahashi H. Characterization of a novel polycystic kidney rat model with accompanying polycystic liver. Exp Anim 2000;49:51–5. Krotec K, Meyer BS, Freeman W, Hamir AN. Congenital cystic disease of the liver, pancreas, and kidney in a Nubian goat (Capra hircus). Vet Pathol 1996;33: 708–10. Martinez JR, Grantham JJ. Polycystic kidney disease: etiology, pathogenesis, and treatment. Dis Mon 1995;41:693–765. O’Leary CA, Mackay BM, Malik R, Edmondston JE, Robinson WF, Huxtable CR. Polycystic kidney disease in bull terriers: an autosomal dominant inherited disorder. Aust Vet J 1999;77:361–6. Oliver J, Macdowell M, Welt LG, Holliday MA, Hollander W, Winters RW, et al. The renal lesions of electrolyte imbalance. The structural alterations in potassiumdepleted rats. J Exp Med 1957;106:563–73. Perey DYE, Herdman RC, Good RA. Polycystic renal disease: A new experimental model. Science 1967;158:494–6. Phillips JK, Hopwood D, Loxley R, Ghatora K, Coombes JD, Tan YS, et al. Temporal relationship between renal cyst development, hypertension and cardiac hypertrophy in a new rat model of autosomal recessive polycystic kidney disease. Kidney Blood Press Res 2007;30:129–44. Sanzen T, Harada K, Yasoshima M, Kawamura Y, Ishibashi M, Nakanuma Y. Polycystic kidney rat is a novel animal model of Caroli’s disease associated with congenital hepatic fibrosis. Am J Pathol 2001;158:1605–12. Takahashi H, Ueyama Y, Hibino T, Kuwahara Y, Suzuki S, Hioki K, Tamaoki N. A new mouse model of genetically transmitted polycystic kidney disease. J Urol 1986;135:1280–3. Taylor AC, Palmer KR. Caroli’s disease. Eur J Gastroenterol Hepatol 1998;10:105–8. Torres VE, Harris PC, Pirson Y. Autosomal dominant polycystic kidney disease. Lancet 2007;369:1287–301. Ward CJ, Hogan MC, Rossetti S, Walker D, Sneddon T, Wang W, et al. The gene mutated in autosomal recessive polycystic kidney disease encodes a large, receptor-like protein. Nat Genet 2002;30:259–69.
Please cite this article in press as: Shoieb A, Shirai N. Polycystic kidney disease in Sprague-Dawley rats. Exp Toxicol Pathol (2015), http://dx.doi.org/10.1016/j.etp.2015.02.002
