Transforming growth factor beta-1 signalling in canine hepatic diseases: new models for human fibrotic liver pathologies

Therapeutic Potential of Autologous Adipose-Derived Stem Cells for the Treatment of Liver Disease

Currently, the most effective therapy for liver diseases is liver transplantation, but its use is limited by organ donor shortage, economic reasons, and the requirement for lifelong immunosuppression. Mesenchymal stem cell (MSC) transplantation represents a promising alternative for treating liver pathologies in both human and veterinary medicine. Interestingly, these pathologies appear with a common clinical and pathological profile in the human and canine species; as a consequence, dogs may be a spontaneous model for clinical investigations in humans. The aim of this work was to characterize canine adipose-derived MSCs (cADSCs) and compare them to their human counterpart (hADSCs) in order to support the application of the canine model in cell-based therapy of liver diseases. Both cADSCs and hADSCs were successfully isolated from adipose tissue samples. The two cell populations shared a common fibroblast-like morphology, expression of stemness surface markers, and proliferation rate. When examining multilineage differentiation abilities, cADSCs showed lower adipogenic potential and higher osteogenic differentiation than human cells. Both cell populations retained high viability when kept in PBS at controlled temperature and up to 72 h, indicating the possibility of short-term storage and transportation. In addition, we evaluated the efficacy of autologous ADSCs transplantation in dogs with liver diseases. All animals exhibited significantly improved liver function, as evidenced by lower liver biomarkers levels measured after cells transplantation and evaluation of cytological specimens. These beneficial effects seem to be related to the immunomodulatory properties of stem cells. We therefore believe that such an approach could be a starting point for translating the results to the human clinical practice in future.

Hepatic Fibrosis in Dogs

Hepatic fibrosis is commonly diagnosed in dogs, often as a sequela to chronic hepatitis (CH). The development of fibrosis is a crucial event in the progression of hepatic disease that is of prognostic value. The pathophysiology of hepatic fibrosis in human patients and rodent models has been studied extensively. Although less is known about this process in dogs, evidence suggests that fibrogenic mechanisms are similar between species and that activation of hepatic stellate cells is a key step. Diagnosis and staging of hepatic fibrosis in dogs requires histopathological examination of a liver biopsy specimen. However, performing a liver biopsy is invasive and assessment of fibrotic stage is complicated by the absence of a universally accepted staging scheme in veterinary medicine. Serum biomarkers that can discriminate among different fibrosis stages are used in human patients, but such markers must be more completely evaluated in dogs before clinical use. When successful treatment of its underlying cause is feasible, reversal of hepatic fibrosis has been shown to be possible in rodent models and human patients. Reversal of fibrosis has not been well documented in dogs, but successful treatment of CH is possible. In human medicine, better understanding of the pathomechanisms of hepatic fibrosis is leading to the development of novel treatment strategies. In time, these may be applied to dogs. This article comparatively reviews the pathogenesis of hepatic fibrosis, its diagnosis, and its treatment in dogs.

The expressions in oxytocin and sex steroid receptors in the reproductive tissues of normal and unilateral cryptorchid dogs

In males, oxytocin is involved with various physiological functions, such as reproductive tract contractility and testicular steroidogenesis. Due to the relationship between sex steroid hormones, oxytocin receptor (OTR) expression and cryptorchidism pathogenesis, this study aimed to investigate the mRNA expression and the localization of OTR in relation to sex steroid receptors in the male reproductive tract of both normal and unilateral abdominal cryptorchid dogs using quantitative PCR and immunohistochemistry. Male dogs were divided into two groups of normal and cryptorchid dogs. Samples from each cryptorchid dog were separated into two subgroups: scrotal and abdominal subgroups. The results showed that a lower percentage of positive OTR immunostaining in the testis and epididymis was observed in the cryptorchid group compared to the normal group. Within the cryptorchid group, the mRNA expression and the localization of OTR in the testis and epididymis of the abdominal subgroup was less than that of the scrotal subgroup. Moreover, the localization of OTR and estrogen receptor beta (ERβ) in reproductive tissues was positively correlated only in the normal group and not in the cryptorchid group. In conclusion, this study proposed that OTR expression, as well as the correlation between the OTR and ERβ in reproductive tissues of male dogs, can be disturbed by cryptorchidism. Furthermore, the OTR, ERβ and their correlation may be involved with the pathogenesis of cryptorchidism. Therefore, the study of gene knockout models to confirm the effect of OTR and sex steroid receptors on canine cryptorchidism should be of interest for further investigation.

Increased caveolin-1 in intervertebral disc degeneration facilitates repair

Background

Preceding intervertebral disc (IVD) degeneration, the cell phenotype in the nucleus pulposus (NP) shifts from notochordal cells (NCs) to chondrocyte-like cells (CLCs). Microarray analysis showed a correlation between caveolin-1 expression and the phenotypic transition of NCs to CLCs. With a clinical directive in mind, the aim of this study was to determine the role of caveolin-1 in IVD degeneration. As a scaffolding protein, caveolin-1 influences several signaling pathways, and transforming growth factor (TGF)-β receptors have been demonstrated to colocalize with caveolin-1. Therefore, the hypothesis of this study was that caveolin-1 facilitates repair by enhancing TGF-β signaling in the IVD.

Methods

Protein expression (caveolin-1, apoptosis, progenitor cell markers, extracellular matrix, and phosphorylated Smad2 [pSmad2]) was determined in IVDs of wild-type (WT) and caveolin-1-null mice and canine IVDs of different degeneration grades (immunofluorescence, immunohistochemistry, and TUNEL assay). Canine/human CLC microaggregates were treated with chondrogenic medium alone or in combination with caveolin-1 scaffolding domain (CSD) peptide and/or caveolin-1 silencing RNA. After 28 days, gene and protein expression profiles were determined.

Results

The NP of WT mice was rich in viable NCs, whereas the NP of caveolin-1-null mice contained more collagen-rich extracellular matrix and fewer cells, together with increased progenitor cell marker expression, pSmad2 TGF-β signaling, and high apoptotic activity. During canine IVD degeneration, caveolin-1 expression and apoptotic activity increased. In vitro caveolin-1 silencing decreased the CLC microaggregate glycosaminoglycan (GAG) content, which could be rescued by CSD treatment. Furthermore, CSD increased TGF-β/pSmad2 signaling at gene and protein expression levels and enhanced the anabolic effects of TGF-β₁, reflected in increased extracellular matrix deposition by the CLCs.

Conclusions

Caveolin-1 plays a role in preservation of the NC phenotype. Additionally, it may be related to CLC apoptosis, given its increased expression in degenerated IVDs. Nevertheless, CSD enhanced CLC GAG deposition in vitro, and hence the increased caveolin-1 expression during IVD degeneration may also facilitate an ultimate attempt at repair. Further studies are needed to investigate how caveolin-1 modifies other signaling pathways and facilitates IVD repair.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-016-0960-y) contains supplementary material, which is available to authorized users.

Hepatic fibrogenesis and transforming growth factor/Smad signaling activation in rats chronically exposed to low doses of lead

Lead is an important heavy metal pollutant in the environment. The nervous system, kidney and liver are the most susceptible organs to lead deposition, showing that this pollutant has no single target system. To examine the cellular and molecular mechanisms involved in their pathobiology of chronic lead at low-dose exposure in the liver, male Wistar rats were exposed to 0.06% lead acetate in drinking water every day for 4 months. At the end of the study, hepatic metal accumulation, morphology and function were examined. Immunochemical staining and Western blot analysis were performed to detect extracellular matrix proteins, α-smooth muscle actin and transforming growth factor (TGF)β1/Smad pathway expression. Results showed increased laminin, collagen IV and fibronectin, located at the perisinusoidal space. Phenotypic transformation of hepatic stellate cells into myofibroblast-like cells was evidenced at the ultrastructural level and a significant expression of α-smooth muscle actin in Disse’s space was observed. These findings were associated with a marked increase in TGFβ1/Smad2/3 signaling. Our data suggest that, chronically, exposure to low levels of lead could trigger the onset of a hepatic fibrogenic process through upregulated TGFβ1/Smad signaling.

Hepatic progenitor cells in canine and feline medicine: potential for regenerative strategies

New curative therapies for severe liver disease are urgently needed in both the human and veterinary clinic. It is important to find new treatment modalities which aim to compensate for the loss of parenchymal tissue and to repopulate the liver with healthy hepatocytes. A prime focus in regenerative medicine of the liver is the use of adult liver stem cells, or hepatic progenitor cells (HPCs), for functional recovery of liver disease. This review describes recent developments in HPC research in dog and cat and compares these findings to experimental rodent studies and human pathology. Specifically, the role of HPCs in liver regeneration, key components of the HPC niche, and HPC activation in specific types of canine and feline liver disease will be reviewed. Finally, the potential applications of HPCs in regenerative medicine of the liver are discussed and a potential role is suggested for dogs as first target species for HPC-based trials.

The canine hepatic progenitor cell niche: molecular characterisation in health and disease

Hepatic progenitor cells (HPCs) are an adult stem cell compartment in the liver that contributes to liver regeneration when replication of mature hepatocytes is insufficient. In this study, laser microdissection was used to isolate HPC niches from the livers of healthy dogs and dogs with lobular dissecting hepatitis (LDH), in which HPCs are massively activated. Gene expression of HPC, hepatocyte and biliary markers was determined by quantitative reverse transcriptase PCR. Expression and localisation of selected markers were further studied at the protein level by immunohistochemistry and immunofluorescent double staining in samples of normal liver and liver from dogs with LDH, acute and chronic hepatitis, and extrahepatic cholestasis. Activated HPC niches had higher gene expression of the hepatic progenitor markers OPN, FN14, CD29, CD44, CD133, LIF, LIFR and BMI1 compared to HPCs from normal liver. There was lower expression of albumin, but activated HPC niches were positive for the biliary markers SOX9, HNF1β and keratin 19 by immunohistochemistry and immunofluorescence. Laminin, activated stellate cells and macrophages are abundant extracellular matrix and cellular components of the canine HPC niche. This study demonstrates that the molecular and cellular characteristics of canine HPCs are similar to rodent and human HPCs, and that canine HPCs are distinctively activated in different types of liver disease.

Potential of regenerative medicine techniques in canine hepatology

Liver cell turnover is very slow, especially compared to intestines and stomach epithelium and hair cells. Since the liver is the main detoxifying organ in the body, it does not come as a surprise that the liver has an unmatched regenerative capacity. After 70% partial hepatectomy, the liver size returns to normal in about two weeks due to replication of differentiated hepatocytes and cholangiocytes. Despite this, liver diseases are regularly encountered in the veterinary clinic. Dogs primarily present with parenchymal pathologies such as hepatitis. The estimated frequency of canine hepatitis depends on the investigated population and accounts for 1%-2% of our university clinic referral population, and up to 12% in a general population. In chronic and severe acute liver disease, the regenerative and replicative capacity of the hepatocytes and/or cholangiocytes falls short and the liver is not restored. In this situation, proliferation of hepatic stem cells or hepatic progenitor cells (HPCs), on histology called the ductular reaction, comes into play to replace the damaged hepatocytes or cholangiocytes. For unknown reasons the ductular reaction is often too little and too late, or differentiation into fully differentiated hepatocytes or cholangiocytes is hampered. In this way, HPCs fail to fully regenerate the liver. The presence and potential of HPCs does, however, provide great prospectives for their use in regenerative strategies. This review highlights the regulation of, and the interaction between, HPCs and other liver cell types and discusses potential regenerative medicine-oriented strategies in canine hepatitis, making use of (liver) stem cells.

Isolation of canine mesenchymal stem cells from amniotic fluid and differentiation into hepatocyte-like cells

Recent findings have demonstrated that amniotic fluid cells are an interesting and potential source of mesenchymal stem cells (MSCs). In this study, we isolated MSCs from canine amniotic fluid and then characterized their multilineage differentiation ability. Canine amniotic fluid stem (cAFS) cells at passage 5 had a fibroblast-like morphology instead of forming colonies and were positive for pluripotent stem cell markers such as OCT4, NANOG, and SOX2. Flow cytometry analysis showed the expression of MSC surface markers CD44, CD29, and CD90 on the cAFS cells. In addition, these cells were cultured under conditions favorable for adipogenic, chondrogenic, and osteogenic induction. The results of this experiment confirmed the mesenchymal nature of cAFS cells and their multipotent potential. Interestingly, although the cells exhibited a fibroblast-like morphology after hepatogenic induction, reverse transcription-polymerase chain reaction revealed that the expression of several hepatic genes, such as albumin, tyrosine aminotransferase, and alpha-1 antiproteinase, increased following maturation and differentiation. These findings indicated that cAFS cells have functional properties similar to those of hepatocytes. Taken together, the results of our study demonstrated that cAFS cells with mesenchymal characteristics can be successfully isolated from canine amniotic fluid and possess functional properties characteristic of hepatocytes. The findings of our work suggest that cAFS cells have the potential to be a resource for cell-based therapies in a canine model of hepatic disease.

COMMD1-deficient dogs accumulate copper in hepatocytes and provide a good model for chronic hepatitis and fibrosis

New therapeutic concepts developed in rodent models should ideally be evaluated in large animal models prior to human clinical application. COMMD1-deficiency in dogs leads to hepatic copper accumulation and chronic hepatitis representing a Wilson’s disease like phenotype. Detailed understanding of the pathogenesis and time course of this animal model is required to test its feasibility as a large animal model for chronic hepatitis. In addition to mouse models, true longitudinal studies are possible due to the size of these dogs permitting detailed analysis of the sequence of events from initial insult to final cirrhosis. Therefore, liver biopsies were taken each half year from five new born COMMD1-deficient dogs over a period of 42 months. Biopsies were used for H&E, reticulin, and rubeanic acid (copper) staining. Immunohistochemistry was performed on hepatic stellate cell (HSC) activation marker (alpha-smooth muscle actin, α-SMA), proliferation (Ki67), apoptosis (caspase-3), and bile duct and liver progenitor cell (LPC) markers keratin (K) 19 and 7. Quantitative RT-PCR and Western Blots were performed on gene products involved in the regenerative and fibrotic pathways. Maximum copper accumulation was reached at 12 months of age, which coincided with the first signs of hepatitis. HSCs were activated (α-SMA) from 18 months onwards, with increasing reticulin deposition and hepatocytic proliferation in later stages. Hepatitis and caspase-3 activity (first noticed at 18 months) increased over time. Both HGF and TGF-β1 gene expression peaked at 24 months, and thereafter decreased gradually. Both STAT3 and c-MET showed an increased time-dependent activation. Smad2/3 phosphorylation, indicative for fibrogenesis, was present at all time-points. COMMD1-deficient dogs develop chronic liver disease and cirrhosis comparable to human chronic hepatitis, although at much higher pace. Therefore they represent a genetically-defined large animal model to test clinical applicability of new therapeutics developed in rodent models.

Copper-induced hepatitis: the COMMD1 deficient dog as a translational animal model for human chronic hepatitis

Chronic inflammatory liver disease regardless of aetiology leads to failing regeneration and fibrosis, ending in cirrhosis. Both in man and in animals this worldwide health problem has no definitive cure. Chronic liver injury causes hepatic stellate cells to proliferate and differentiate into matrix-producing cells. New therapeutic options will be developed upon detailed understanding of the molecular mechanisms driving liver fibrosis. This may lead to new anti-fibrotic therapies which need to be tested in suitable models before application in the veterinary and human clinic. On the other side, to restore the failing regenerative capacity of the diseased liver cells, adult progenitor cells are of interest, as an alternative to whole organ transplantation. In order to find the most suitable large animal model it is important to recognise that the typical histopathological reaction pattern of the liver can differ between mammalian species. It is therefore imperative that specialists in veterinary internal medicine and pathology, being familiar with the diseases and pathologies of the liver in different animal species, are teaming-up in finding the best models for veterinary and human liver diseases. Several large animal models have been mentioned, like pigs, sheep, and dogs. Based on the observations that man and dog share the same hepatopathies and have identical clinical, pathological and pathogenetic reaction patterns during the development of liver disease, the dog seems to be a properly suited species to test new therapeutic strategies for pets and their best friends.

Inherited liver shunts in dogs elucidate pathways regulating embryonic development and clinical disorders of the portal vein

Congenital disorders of the hepatic portal vasculature are rare in man but occur frequently in certain dog breeds. In dogs, there are two main subtypes: intrahepatic portosystemic shunts, which are considered to stem from defective closure of the embryonic ductus venosus, and extrahepatic shunts, which connect the splanchnic vascular system with the vena cava or vena azygos. Both subtypes result in nearly complete bypass of the liver by the portal blood flow. In both subtypes the development of the smaller branches of the portal vein tree in the liver is impaired and terminal branches delivering portal blood to the liver lobules are often lacking. The clinical signs are due to poor liver growth, development, and function. Patency of the ductus venosus seems to be a digenic trait in Irish wolfhounds, whereas Cairn terriers with extrahepatic portosystemic shunts display a more complex inheritance. The genes involved in these disorders cannot be identified with the sporadic human cases, but in dogs, the genome-wide study of the extrahepatic form is at an advanced stage. The canine disease may lead to the identification of novel genes and pathways cooperating in growth and development of the hepatic portal vein tree. The same pathways likely regulate the development of the vascular system of regenerating livers during liver diseases such as hepatitis and cirrhosis. Therefore, the identification of these molecular pathways may provide a basis for future proregenerative intervention.

Expression of fibrosis-related genes in canine chronic hepatitis

Molecular regulation of fibrosis in chronic canine hepatitis is poorly understood. The authors employed quantitative polymerase chain reaction (PCR) to determine the expression levels of genes reported to be related to fibrosis in other species (human, mouse, and rat) and to elucidate the relationship of these genes with the degree of fibrosis and the presence or absence of ascites and/or jaundice in dogs with hepatitis. Nine fibrosis-related genes were assayed: PDGFB, PDGFD, MMP2, TIMP1, THBS1, COL1A1, COL3A1, TGFB1, and TGFB2. Liver samples of 15 dogs with chronic hepatitis and 4 healthy control dogs were obtained via laparoscopic biopsy and subjected to histologic and quantitative PCR analyses. The expression of all 9 genes showed significant positive correlation (P<.01, r>.70) with the degree of fibrosis. Furthermore, the expression levels of all genes except TGFB1 were significantly higher (P<.05) in dogs with hepatic failure-related symptoms (ascites/jaundice). Results suggest that these 9 genes are integral to the development of fibrosis in canine chronic hepatitis.

Cross-species immunohistochemical investigation of the activation of the liver progenitor cell niche in different types of liver disease

BACKGROUND

When hepatocyte replication during liver disease is insufficient for regeneration, liver progenitor cells (LPCs) are activated. The cells and stroma in the immediate environment of LPCs, together termed the LPC niche, are thought to play an important role in this activation. Among these cells are the hepatic stellate cells (HSCs)/myofibroblasts (MFs).

AIMS/METHODS

We assessed the activation of HSC/MFs and LPCs in relation to the histological location and extent of liver disease in immunohistochemically (double) stained serial sections. Markers of HSC/MFs [alpha-smooth muscle actin, glial fibrillary acidic protein (GFAP), neurotrophin 3 and neural-cell adhesion molecule], markers of LPCs (keratin 7 and keratin 19) and a proliferation marker (Ki67) were used. A very relevant spontaneous model to evaluate LPC niche activation in a translational approach seems to be the dog. Therefore, both human and canine liver diseases with different degree of fibrosis and disease activity were included.

RESULTS

In human and canine liver disease, type and extent of LPC niche activation depended on type and severity of disease (P<0.05) and corresponded to the main location of disease. Activated HSCs surrounded the activated LPCs. In chronic hepatitis and non-alcoholic steatohepatitis lobular-type HSCs were activated, while during biliary disease portal/septal MFs were mainly activated. In canine liver, GFAP further presented as an early marker of HSC activation. Activation of the LPCs correlated with disease location and severity (P<0.01), and was inversely related to hepatocyte proliferation, as was previously shown in man.

CONCLUSION

A shared involvement of HSC/MFs, LPCs and disease severity during hepatic disease processes is shown, which is highly similar in man and dog.

Comparison of different methods to obtain and store liver biopsies for molecular and histological research

Background

To minimize the necessary number of biopsies for molecular and histological research we evaluated different sampling techniques, fixation methods, and storage procedures for canine liver tissue. For addressing the aim, three biopsy techniques (wedge biopsy, Menghini, True-cut), four storage methods for retrieval of RNA (snap freezing, RNAlater, Boonfix, RLT-buffer), two RNA isolation procedures (Trizol and RNAeasy), and three different fixation protocols for histological studies (10% buffered formalin, RNAlater, Boonfix) were compared. Histological evaluation was based on hematoxylin-eosin (HE) and reticulin (fibrogenesis) staining, and rubeanic acid and rhodanine stains for copper. Immunohistochemical evaluation was performed for cytokeratin-7 (K-7), multidrug resistance binding protein-2 (MRP-2) and Hepar-1.

Results

RNA quality was best guaranteed by the combination of a Menghini biopsy with NaCl, followed by RNAlater preservation and RNAeasy mini kit extraction. These results were confirmed by quantitative RT-PCR testing. Reliable histological assessment for copper proved only possible in formalin fixed liver tissue. Short formalin fixation (1–4 hrs) improved immunohistochemical reactivity and preservation of good morphology in small liver biopsies.

Conclusion

At least two biopsies (RNAlater and formalin) are needed. Since human and canine liver diseases are highly comparable, it is conceivable that the protocols described here can be easily translated into the human biomedical field.

Characterisation of the hepatic progenitor cell compartment in normal liver and in hepatitis: an immunohistochemical comparison between dog and man

The liver progenitor cell compartment in the normal canine liver and in spontaneous canine acute (AH) and chronic hepatitis (CH) was morphologically characterised and compared to its human equivalents. Immunohistochemistry was performed for cytokeratin-7 (CK7), human hepatocyte marker (Hep Par 1), multidrug resistance-associated protein-2 (MRP2), and breast cancer resistance protein (BCRP) on paraffin and frozen sections from canine and human tissues. Normal liver showed similar morphology and immunohistochemical reaction of the progenitor cell compartment/canal of Hering in man and dog. In addition, a ductular reaction, comparable in terms of severity, location and immunohistochemical characteristics, was observed in canine and human AH and CH. CK7 was a good marker for canine progenitor cells, including intermediate cells, which were positively identified in cases of AH and CH. In both species, BCRP was expressed in both hepatocytes and bile ducts of the normal liver, and in ductular reaction in AH and CH. MRP2 detected bile canalicular membranes in man and dog. These findings underline the similarities between canine and human liver reaction patterns and may offer mutual advantage for comparative research in human and canine spontaneous liver diseases.

The dog liver contains a "side population" of cells with hepatic progenitor-like characteristics

The aim of this study was to isolate and characterize potential progenitor cells from healthy dog livers. Stem/progenitor cells can be prospectively isolated from a diversity of tissues using their ability to efficiently pump out the dye Hoechst33342, thereby portraying a side population (SP) in dual-wavelength flow cytometry. We here describe the detection of a SP in dog liver, constituting approximately 3 % of the nonparenchymal-enriched cell fractions. A subpopulation of the SP (approximately 30 %) was immunonegative for the panhematopoietic marker CD45, and consisted predominantly of small, mononuclear, keratin 7-immunoreactive cells; characteristics suggestive of a liver progenitor cell phenotype. Both the CD45- and CD45+ SP showed upregulated expression of progenitor/cholangiocyte marker genes, but also low-level expression of hepatocyte markers, suggesting the presence of progenitor cells committed to the hepatic lineage in both SP fractions. Our findings demonstrate that healthy canine liver contains a small population of cells with progenitor-like characteristics that can be isolated on the basis of efficient Hoechst33342 expulsion.

In vitro differentiation of liver progenitor cells derived from healthy dog livers

Naturally occurring liver disease in dogs resemble human liver disease in great detail; including the activation of liver progenitor cells (LPC) in acute and chronic liver disease. The aim of the present study was to isolate, culture, and characterize progenitor cells derived from healthy mature dog livers. A nonparenchymal cell fraction enriched with small hepatocytes was isolated and cultured in Hepatozyme-serum-free media (SFM) to stimulate the growth of colony-forming small epithelial cells. After 2 weeks of culturing, clonal expansion of keratin 7 (K7) immunopositive small cells with a large nucleus/cytoplasm ratio emerged in the hepatocyte monolayer. These colonies expressed genes of several hepatocyte (CYP1A1, ALB, and KRT18), cholangiocyte/LPC (KRT7 and KRT19), and progenitor cell markers (alpha-fetoprotein, CD44, prominin1, KIT, THY1, and neural cell adhesion molecule 1), indicating their immature and bipotential nature. Gene-expression profiles indicated a more pronounced hepatic differentiation in Hepatozyme-SFM compared to William's Medium E (WME). Furthermore, colony-forming cells differentiated toward intermediate hepatocyte-like cells with a more pronounced membranous K7 immunostaining. In conclusion, colony-forming small epithelial cells in long-term canine liver cell cultures express LPC markers and have differentiating capacities. These cells may therefore be considered as progenitor cells of the liver.

Intradermal injection of Hsp60 induces cytokine responses in canine atopic and healthy skin

The purpose of this study was to investigate the immunoregulatory potential of Hsp60 in the skin of dogs with atopic dermatitis. Three dogs with chronic atopic dermatitis and four healthy dogs were injected intradermally with Hsp60 and phosphate-buffered saline. Biopsies were taken before testing from non-injected control skin, lesional and non-lesional atopic skin, and 48 and 72 h after injection. Analysis of cytokine messenger RNA was performed using quantitative real-time polymerase chain reaction. Forty-eight hours after Hsp60 injection, a rise in interleukin (IL)-10 was found (P = 0.034) with the highest expression levels in non-lesional atopic and control skin. A rise of transforming growth factor beta (P = 0.015) and IL-12p40 (P = 0.017) was noticed 72 h after Hsp60 injection in control skin. No significant differences were observed for the expression of IL-4, IL-12p35, and interferon gamma. The results indicate that Hsp60 is able to induce cytokines of a regulatory and Th1 phenotype in the skin. Furthermore, this study seems to provide a first indication of deficient Hsp60 response in atopic dermatitis affected skin.

Spontaneous adenocarcinoma immunoreactive to cyclooxygenase-2 and transforming growth factor-beta1 in the buccal salivary gland of a Richardson's ground squirrel (Spermophilus richardsonii)

The ground squirrel is used as an experimental animal because of its unique biological nature. A 3-year-old female Richardson's ground squirrel developed a mass, 1.5 cm in diameter, in the buccal mucosa. The mass consisted of neoplastic epithelial cells showing acinar, ductular, intraductal papillary, solid, and lobular growth patterns; the cells were immunoreactive to cytokeratin, cyclooxygenase-2 (a marker of malignancy) and TGF-beta1. After resection, the tumor recurred with increased area having a solid or lobular pattern with little differentiation. This tumor was diagnosed as an adenocarcinoma arising from the buccal gland, the first case reported in the ground squirrel. A prominent desmoplastic reaction was present. The interstitial cells reacted to alpha-smooth muscle actin and vimentin, indicating a myofibroblastic nature, presumably induced by epithelial TGF-beta1.

Major HGF-mediated regenerative pathways are similarly affected in human and canine cirrhosis

Background

The availability of non-rodent animal models for human cirrhosis is limited. We investigated whether privately-owned dogs (Canis familiaris) are potential model animals for liver disease focusing on regenerative pathways. Several forms of canine hepatitis were examined: Acute Hepatitis (AH), Chronic Hepatitis (CH), Lobular Dissecting Hepatitis (LDH, a specific form of micronodulair cirrhosis), and Cirrhosis (CIRR). Canine cirrhotic samples were compared to human liver samples from cirrhotic stages of alcoholic liver disease (hALC) and chronic hepatitis C infection (hHC).

Results

Canine specific mRNA expression of the regenerative hepatocyte growth factor (HGF) signaling pathway and relevant down-stream pathways were measured by semi-quantitative PCR and Western blot (STAT3, PKB, ERK1/2, and p38-MAPK). In all canine groups, levels of c-MET mRNA (proto-oncogenic receptor for HGF) were significantly decreased (p < 0.05). Surprisingly, ERK1/2 and p38-MAPK were increased in CH and LDH. In the human liver samples Western blotting indicated a high homology of down-stream pathways between different etiologies (hALC and hHC). Similarly activated pathways were found in CIRR, hALC, and hHC.

Conclusion

In canine hepatitis and cirrhosis the major regenerative downstream pathways were activated. Signaling pathways are similarly activated in human cirrhotic liver samples, irrespective of the differences in etiology in the human samples (alcohol abuse and HCV-infection). Therefore, canine hepatitis and cirrhosis could be an important clinical model to evaluate novel interventions prior to human clinical trials.