Development and application of multiple internal reference (housekeeper) gene assays for accurate normalisation of canine gene expression studies

Methylation of TNFRSF13B and TNFRSF13C in duodenal mucosa in canine inflammatory bowel disease and its association with decreased mucosal IgA expression

Although decreased intestinal IgA expression has been reported in dogs with inflammatory bowel disease (IBD), the mechanism underlying this decrease is unknown. Transmembrane activator and calcium-modulating cyclophilin-ligand interactor (TACI) and B cell-activating factor of the TNF family (BAFF) receptor (BAFF-R) are key receptors for T cell-independent IgA class switching by the binding of IgA-inducing cytokine a proliferation-inducing ligand (APRIL) and BAFF. Here we show decreased TACI and BAFF-R mRNA expression and hypermethylation of their corresponding genes TNFRSF13B and TNFRSF13C, respectively in the duodenal mucosa of dogs with IBD. To examine whether DNA methylation of the TNFRSF13B and TNFRSF13C influences the mRNA expression of TACI and BAFF-R, respectively, we first analyzed methylation and mRNA expression levels in vitro using 2 canine B lymphoid cell lines, GL-1 and CLBL-1. Methylation profiles in the cells were examined by bisulfite sequencing and methylation-specific PCR (MSP) with primer pairs specific to methylated or unmethylated sequences. These methylation analyses revealed hypermethylation of the CpG islands of both TNFRSF13B and TNFRSF13C in GL-1, but not in CLBL-1 cells. The mRNA expression levels of TACI and BAFF-R were significantly lower in GL-1 than in CLBL-1 cells. Treatment with 5-aza-2'-deoxycytidine significantly increased TACI and BAFF-R mRNA expression in GL-1 cells through demethylation of TNFRSF13B and TNFRSF13C, respectively. These results suggest that the mRNA expression of TACI and BAFF-R is regulated through methylation of their genes in canine B cells. Quantitative real-time MSP showed significant hypermethylation of the CpG islands of TNFRSF13B and TNFRSF13C in the duodenal mucosa of dogs with IBD. Furthermore, duodenal mRNA expression levels of TACI and BAFF-R were significantly lower in dogs with IBD than in healthy controls. The mRNA expression levels of TACI positively correlated with intestinal IgA expression, whereas the methylation level of its gene (TNFRSF13B) negatively correlated with IgA expression. The present results suggest the role of TACI in the regulation of mucosal IgA expression through epigenetic modifications.

Immunohistochemical localization and mRNA quantification of osteopontin and Tamm-Horsfall protein in canine renal tissue after potassium oxalate injection

Background

Urinary macromolecules contribute to promoting or inhibiting crystal retention in renal tissue and stone formation. Osteopontin (OPN) and Tamm-Horsfall protein (THP) are the most important proteins involved in this process. Although these two proteins were discovered a long time ago, their role in setting kidney stone formation has not yet been fully investigated. We conducted a study to explore the role of OPN and THP in canine renal oxalosis. Ten dogs were carefully examined prior to the study. Six dogs were assigned to the treatment group and were injected intravenously with 0.5 M potassium oxalate (KOx). The other four dogs were assigned to a control group and were injected intravenously with 0.9% NaCl three times a day (tid) for 7 consecutive days. Then kidneys were harvested for pathological, immunohistochemical examination and OPN and THP mRNA expression levels were quantified by quantitative real-time PCR.

Results

Calcium oxalate crystals deposition was observed in both renal cortex and medulla. Immunohistochemistry examination revealed increased tissue expression of OPN in the renal tissue while THP was significantly decreased. OPN mRNA expression level significantly increased in treated dogs compared to that in the controls, while THP mRNA level significantly decreased.

Conclusion

Together, these results suggest that THP and OPN are both involved in the pathogenesis and response to oxalate exposure.

Technical note: Selection of suitable reference genes for studying gene expression in milk somatic cell of yak (Bos grunniens) during the lactation cycle

Quantitative real-time PCR is the most sensitive technique for gene expression analysis. Data normalization is essential to correct for potential errors incurred in all steps from RNA isolation to PCR amplification. The commonly accepted approach for normalization is the use of reference gene. Until now, no suitable reference genes have been available for data normalization of gene expression in milk somatic cells of lactating yaks across lactation. In the present study, we evaluated the transcriptional stability of 10 candidate reference genes in milk somatic cells of lactating yak, including ACTB, B2M, GAPDH, GTP, MRPL39, PPP1R11, RPS9, RPS15, UXT, and RN18S1. Four genes, RPS9, PPP1R11, UXT, and MRPL39, were identified as being the most stable genes in milk somatic cells of lactating yak. Using the combination of RPS9, PPP1R11, UXT, and MRPL39 as reference genes, we further assessed the relative expression of 4 genes of interest in milk somatic cells of yak across lactation, including ELF5, ABCG2, SREBF2, and DGAT1. Compared with expression in colostrum, the overall transcription levels of ELF5, ABCG2, and SREBF2 in milk were found to be significantly upregulated in early, peak, and late lactation, and significantly downregulated thereafter, before the dry period. A similar pattern was observed in the relative expression of DGAT1, but no significant difference was revealed in its expression in milk from late lactation compared with colostrum. Based on these results, we suggest that the geometric mean of RPS9, PPP1R11, UXT, and MRPL39 can be used for normalization of real-time PCR data in milk somatic cells of lactating yak, if similar experiments are performed.

CD4⁺ T cell cytokine gene and protein expression in duodenal mucosa of dogs with inflammatory bowel disease

Inflammatory bowel disease (IBD) is a common cause of chronic gastrointestinal signs in dogs. In humans, T helper cells have important roles in the pathogenesis of IBD. In contrast, no specific involvement of a distinct T cell subset has been described in canine IBD. The present study evaluated the gene and protein expression of cytokines of T cell subsets in duodenal mucosa from dogs with IBD. Relative quantification of interleukin (IL)-17A, interferon (IFN)-γ, IL-4 and IL-10 mRNA transcription was performed using duodenal mucosa from 27 IBD dogs and 8 controls. Duodenal mucosal IL-17A, IFN-γ and IL-10 protein levels were determined by ELISA in 15 IBD dogs and 8 controls. There was no significant difference in each cytokines mRNA transcription level between groups. There was no significant difference in IL-17A, IFN-γ and IL-10 protein expression levels between groups. Thus, there is no clear evidence for the involvement of distinct Th cytokine in the pathogenesis of canine IBD.

Inhibition of survivin influences the biological activities of canine histiocytic sarcoma cell lines

Canine histiocytic sarcoma (CHS) is an aggressive malignant neoplasm that originates from histiocytic lineage cells, including dendritic cells and macrophages, and is characterized by progressive local infiltration and a very high metastatic potential. Survivin is as an apoptotic inhibitory factor that has major functions in cell proliferation, including inhibition of apoptosis and regulation of cell division, and is expressed in most types of human and canine malignant neoplasms, including melanoma and osteosarcoma. To investigate whether survivin was expressed at high levels in CHS and whether its expression was correlated with the aggressive biological behavior of CHS, we assessed relation between survivin expression and CHS progression, as well as the effects of survivin inhibition on the biological activities of CHS cells. We comparatively analyzed the expression of 6 selected anti-apoptotic genes, including survivin, in specimens from 30 dogs with histiocytic sarcoma and performed annexin V staining to evaluate apoptosis, methylthiazole tetrazolium assays to assess cell viability and chemosensitivity, and latex bead assays to measure changes in phagocytic activities in 4 CHS cell lines and normal canine fibroblasts transfected with survivin siRNA. Survivin gene expression levels in 30 specimens were significantly higher than those of the other 6 genes. After transfection with survivin siRNA, apoptosis, cell growth inhibition, enhanced chemosensitivity, and weakened phagocytic activities were observed in all CHS cell lines. In contrast, normal canine fibroblasts were not significantly affected by survivin knockdown. These results suggested that survivin expression may mediate the aggressive biological activities of CHS and that survivin may be an effective therapeutic target for the treatment of CHS.

Markedly increased expression of interleukin-8 in the colorectal mucosa of inflammatory colorectal polyps in miniature dachshunds

Inflammatory colorectal polyps (ICRPs) in miniature dachshunds were recently recognized as a major cause of large bowel diarrhea in this dog breed in Japan. ICRPs are characterized by the formation of multiple small polyps and/or space-occupying large polyps in the colorectal area and are thought to be a novel form of inflammatory bowel disease (IBD). To explore key mediators in the pathogenesis of ICRPs, we analyzed several pro-inflammatory cytokine (IL-1β, IL-6, TNF-α, IL-8, IL-12p35, IL-12/23p40, and IL-23p19) mRNA expressions in colorectal polyps in ICRP dogs by quantitative PCR. Among these cytokines, IL-8 mRNA expression was markedly up-regulated in large polyps. To examine IL-8 protein expression, we analyzed IL-8 protein level and its location in colorectal mucosal specimens of ICRP dogs by ELISA and immunofluorescence microscopy. IL-8 protein was significantly increased in large polyps and serum in dogs with ICRPs compared to controls. By immunofluorescence microscopy, IL-8 was only localized in macrophages, but not in mucosal epithelial cells or neutrophils. IL-8-positive macrophages were significantly increased in large polyps compared to controls. These results suggest that IL-8 is produced mainly by macrophages and may induce neutrophil infiltration in the colorectal area of ICRP dogs.

Selection of internal reference genes for normalization of quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis in the canine brain and other organs

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) is a specific and sensitive technique for quantifying gene expression. To analyze qRT-PCR data accurately, suitable reference genes that show consistent expression patterns across different tissues and experimental conditions should be selected. The objective of this study was to obtain the most stable reference genes in dogs, using samples from 13 different brain tissues and 10 other organs. 16 well-known candidate reference genes were analyzed by the geNorm, NormFinder, and BestKeeper programs. Brain tissues were derived from several different anatomical regions, including the forebrain, cerebrum, diencephalon, hindbrain, and metencephalon, and grouped accordingly. Combination of the three different analyses clearly indicated that the ideal reference genes are ribosomal protien S5 (RPS5) in whole brain, RPL8 and RPS5 in whole body tissues, RPS5 and RPS19 in the forebrain and cerebrum, RPL32 and RPS19 in the diencephalon, GAPDH and RPS19 in the hindbrain, and MRPS7 and RPL13A in the metencephalon. These genes were identified as ideal for the normalization of qRT-PCR results in the respective tissues. These findings indicate more suitable and stable reference genes for future studies of canine gene expression.

Analysis of gene expression in canine idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) in dogs is a rare disease of unknown aetiology, seen in terrier breeds, particularly the West Highland white terrier (WHWT). The aim of this study was to determine pulmonary gene expression in canine IPF in order to gain insights into the pathogenesis of the disease and to identify possible biomarkers. Microarray analyses were conducted to determine gene expression profiles in the lungs of dogs with IPF and control dogs of various breeds. More than 700 genes were identified as having greater than two-fold difference in expression between the two groups. The significant biological functions associated with these genes were related to cellular growth and proliferation, developmental processes, cellular movement, cell to cell signalling and interaction, and antigen presentation. Altered levels of expression were confirmed by quantitative reverse transcriptase PCR for genes encoding chemokine (C-C) ligand (CCL) 2 (+4.9 times), CCL7 (+6.8 times), interleukin 8 (+4.32 times), chemokine (C-X-C) ligand 14 (+3.4 times), fibroblast activation protein (+4.7 times) and the palate, lung and nasal associated protein (PLUNC, -25 times). Serum CCL2 concentrations were significantly higher in WHWTs with IPF (mean 628.1 pg/mL, interquartile range 460.3-652.7 pg/mL) than unaffected WHWTs (mean 344.0 pg/mL, interquartile range 254.5-415.5 pg/mL; P=0.001). The results support CCL2 as a candidate biomarker for IPF in dogs.

Expression of CD4+ T cell cytokine genes in the colorectal mucosa of inflammatory colorectal polyps in miniature dachshunds

Inflammatory colorectal polyps (ICRPs) in miniature dachshunds are recently recognized as a major cause of large bowel diarrhea in this dog breed in Japan. ICRPs are characterized by the formation of multiple small polyps and a space-occupying large polyp in the colorectal area, and are thought to be a novel form of inflammatory bowel disease (IBD). In humans, specific cytokine patterns attributed to T helper (Th)1, Th17 and regulatory T cells have important roles in the pathogenesis of IBD. Thus, the aim of the present study was to assess the gene expression of cytokines of T cell subsets in the colorectal mucosa from dogs with ICRPs. Colorectal mucosal specimens from 10 dogs with ICRPs and 14 control dogs were used in this study. Interferon (IFN)-γ, interleukin (IL)-4, IL-17A and IL-10 mRNA expression was assessed using quantitative real-time PCR. IL-17A mRNA expression was significantly increased in large polyps compared to small polyps and controls. IFN-γ and IL-10 mRNA expression in large polyps were significantly higher than in controls. There was no significant difference in IL-4 mRNA expression among the three groups. IL-17A is thought to play important roles in the pathogenesis of ICRPs. IL-10 up-regulation could oppose the proinflammatory function of IL-17A.

Cytokine and transcription factor expression by Aspergillus fumigatus-stimulated peripheral blood mononuclear cells in dogs with sino-nasal aspergillosis

The causal agent of sino-nasal aspergillosis is usually Aspergillus fumigatus, which is a saprophytic and ubiquitous fungus that causes a severe rhinosinusitis in apparent healthy dogs. Affected dogs do not have systemic immuno-suppression. It has been shown previously that dogs affected by this disease have local over-expression of interleukin (IL)-10 and Th1 cytokines in nasal mucosal tissue. The aim of the present study was to assess the response of peripheral blood mononuclear cells (PBMC) from affected and unaffected dogs to antigen-specific stimulation with heat-inactivated Aspergillus spp. conidia, by quantifying gene expression for specific Th1, Th2, Th17 and Treg cytokines and their related transcription factors. Quantification of IL-4 and IFN-γ protein in culture supernatant was performed by enzyme-linked immunosorbent assay (ELISA). PBMC from dogs with SNA produced adequate mRNA encoding IFN-γ and IFN-γ protein. The expression of IL-17A mRNA was significantly greater in PBMC of affected compared with unaffected dogs. The amount of IL-10 mRNA in PBMC from affected dogs decreased after antigen-specific challenge. These results suggest that the incapacity of affected dogs to clear these fungal infections is not related to a defect in Th1 immunity or to an overwhelming regulatory reaction, but rather to an uncontrolled pro-inflammatory reaction driven by Th17 cells.

Potential role of Alternaria and Cladosporium species in canine lymphoplasmacytic rhinitis

OBJECTIVES

To evaluate the possible role of Alternaria and Cladosporium species in the pathogenesis of canine lymphoplasmacytic rhinitis by comparing the amount of specific fungal DNA in nasal mucosal biopsies between dogs without nasal neoplasia and those with lymphoplasmacytic rhinitis or nasal neoplasia.

METHODS

Quantitative real-time polymerase chain reaction (qPCR) assays detecting DNA from Alternaria and Cladosporium fungi were applied to nasal mucosal biopsies collected from dogs with lymphoplasmacytic rhinitis (n = 8), dogs with nasal neoplasia (n = 10) and control animals (n = 10). A copy number for each sample was calculated using a standard curve of known copy number and differences amongst groups were assessed using Kruskal-Wallis tests.

RESULTS

No significant difference was found between the groups. Low levels of Alternaria DNA (10-100 copies/PCR) were detected in one sample; very low levels of DNA (<10 copies/qPCR) were detected in 6 samples, and 21 samples were negative. Low levels of Cladosporium DNA were detected in 2 samples; very low levels of DNA in 18; and 8 were negative.

CLINICAL SIGNIFICANCE

Results of this study reveal that Alternaria and Cladosporium species are part of the canine nasal flora, and that these fungi are probably not involved in the pathogenesis of lymphoplasmacytic rhinitis.

Array-based comparative genomic hybridization-guided identification of reference genes for normalization of real-time quantitative polymerase chain reaction assay data for lymphomas, histiocytic sarcomas, and osteosarcomas of dogs

OBJECTIVE

To identify suitable reference genes for normalization of real-time quantitative PCR (RT-qPCR) assay data for common tumors of dogs.

SAMPLE

Malignant lymph node (n = 8), appendicular osteosarcoma (9), and histiocytic sarcoma (12) samples and control samples of various nonneoplastic canine tissues.

PROCEDURES

Array-based comparative genomic hybridization (aCGH) data were used to guide selection of 9 candidate reference genes. Expression stability of candidate reference genes and 4 commonly used reference genes was determined for tumor samples with RT-qPCR assays and 3 software programs.

RESULTS

LOC611555 was the candidate reference gene with the highest expression stability among the 3 tumor types. Of the commonly used reference genes, expression stability of HPRT was high in histiocytic sarcoma samples, and expression stability of Ubi and RPL32 was high in osteosarcoma samples. Some of the candidate reference genes had higher expression stability than did the commonly used reference genes.

CONCLUSIONS AND CLINICAL RELEVANCE

Data for constitutively expressed genes with high expression stability are required for normalization of RT-qPCR assay results. Without such data, accurate quantification of gene expression in tumor tissue samples is difficult. Results of the present study indicated LOC611555 may be a useful RT-qPCR assay reference gene for multiple tissue types. Some commonly used reference genes may be suitable for normalization of gene expression data for tumors of dogs, such as lymphomas, osteosarcomas, or histiocytic sarcomas.

Decreased immunoglobulin A concentrations in feces, duodenum, and peripheral blood mononuclear cells of dogs with inflammatory bowel disease

BACKGROUND

Although immunoglobulin A (IgA) plays a key role in regulating gut homeostasis, its role in canine inflammatory bowel disease (IBD) is unknown.

HYPOTHESIS

IgA expression may be altered in dogs with IBD, unlike that observed in healthy dogs and dogs with other gastrointestinal diseases.

ANIMALS

Thirty-seven dogs with IBD, 10 dogs with intestinal lymphoma, and 20 healthy dogs.

METHODS

Prospective study. IgA and IgG concentrations in serum, feces, and duodenal samples were measured by ELISA. IgA(+) cells in duodenal lamina propria and IgA(+) CD21(+) peripheral blood mononuclear cells (PBMCs) were examined by immunohistochemistry and flow cytometry, respectively. Duodenal expression of the IgA-inducing cytokine transforming growth factor β (TGF-β), B cell activating factor (BAFF), and a proliferation-inducing ligand (APRIL) was quantified by real-time RT-PCR.

RESULTS

Compared to healthy dogs, dogs with IBD had significantly decreased concentrations of IgA in fecal and duodenal samples. The number of IgA(+) CD21(+) PBMCs and IgA(+) cells in duodenal lamina propria was significantly lower in dogs with IBD than in healthy dogs or dogs with intestinal lymphoma. Duodenal BAFF and APRIL mRNA expression was significantly higher in IBD dogs than in the healthy controls. Duodenal TGF-β mRNA expression was significantly lower in dogs with IBD than in healthy dogs and dogs with intestinal lymphoma.

CONCLUSIONS AND CLINICAL IMPORTANCE

IBD dogs have decreased IgA concentrations in feces and duodenum and fewer IgA(+) PBMCs, which might contribute to development of chronic enteritis in dogs with IBD.

Expression of trefoil factor genes in the duodenum and colon of dogs with inflammatory bowel disease and healthy dogs

Trefoil factors (TFF) are small peptides produced by goblet cells, which are crucial for epithelial restitution. In humans with inflammatory bowel disease (IBD), TFF expression is up-regulated as part of an unspecific repair mechanism. The goal of this study was to assess TFF gene expression in the gastrointestinal tract from dogs with IBD compared to healthy controls. Preliminary assessment by PCR revealed TFF1 and 3 expression in the small and large intestine, whereas TFF2 was amplified only in the stomach. Subsequent RT-qPCR (with relative quantification against 3 reference genes) on endoscopic duodenal (IBD n=22, healthy controls n=18) and colonic (IBD n=12, controls n=11) biopsies revealed that TFF1 expression was significantly up-regulated in the duodenum from IBD dogs (Mann-Whitney p=0.001), whereas TFF3 expression was significantly lower in IBD colon compared to controls (t-test p=0.018). This study demonstrates evidence for dysregulation of TFF gene expression in canine IBD. Up-regulation of TFF1 could signify ectopic expression as a compensatory repair-mechanism, whereas down-regulation of TFF3 could contribute to defective epithelial barrier function, respectively. Whether this is a cause or consequence of IBD could not be established.

Selection of valid reference genes for expression studies of hepatic cell lines under IFN-α treatment

The proper selection of reference genes to normalize the quantitative real-time PCR (RT-qPCR) results under particular experimental conditions is crucial for validation of the gene quantification data. Herein, using SYBR green RT-qPCR, five reference genes (GAPDH, ACTB, HMBS, HPRT-1 and TBP) were evaluated to determine the most stable reference genes in hepatic cell lines (Huh-7 and HepG(2)) under IFN-α treatment conditions. Analyses by geNorm program ranked GAPDH and HPRT-1 in Huh-7 and that of ACTB and HMBS in HepG(2) cells as the most stable reference genes under IFN-α treatment. While, same reference gene pairs were ranked by NormFinder program in Huh-7 cells, GAPDH was assessed as the most stable gene in HepG(2) group by this program, implying the importance of the employed algorithm in comparative interpretation of the data. Finally, cumulative analyses by one-way ANOVA, geNorm and NormFinder programs indicated that use of two reference genes (HMBS and GAPDH) in Huh-7 and three (HMBS, ACTB and GAPDH) in HepG(2) cells would greatly improve the normalization of the RT-qPCR data under IFN-α. Data presented in this paper will aid the selection of the most stable reference genes in RT-qPCR studies on evaluation of hepatic viral proteins and IFN pathway.

Increased expression of fractalkine and its receptor CX3CR1 in canine inflammatory bowel disease and their possible role in recruitment of intraepithelial lymphocytes

The interaction between fractalkine/CX(3)CL1 and its receptor CX(3)CR1 has been reported to play an important role in various human inflammatory diseases, including inflammatory bowel disease (IBD) mediated by lymphocyte chemoattraction. The objective of this study was to investigate the role of fractalkine and CX(3)CR1 in lymphocyte migration in canine IBD. IBD was diagnosed in 34 dogs, and 19 healthy beagles were used as normal controls. We quantified intestinal mRNA and protein expression of fractalkine and CX(3)CR1 by real-time RT-PCR and ELISA, respectively, and examined the localization of fractalkine in canine intestine by immunohistochemistry. The expression of CX(3)CR1 and surface antigens on peripheral blood mononuclear cells (PBMCs) and intraepithelial lymphocytes (IELs) was analyzed by flow cytometry. Intestinal fractalkine and CX(3)CR1 mRNA was significantly up-regulated in IBD dogs compared with the healthy control dogs. In addition, fractalkine expression on intestinal epithelial cells was significantly increased in the intestinal mucosa of IBD dogs compared with the healthy dogs. CX(3)CR1(+) PBMCs were significantly elevated in IBD dogs and positively correlated with the histopathological severity of IELs infiltration. These CX(3)CR1(+) PBMCs predominantly expressed markers for cytotoxic T cells. Almost all IELs expressed CD3, and the majority of cells expressed CD8 rather than CD4, which was analogous to the CX(3)CR1(+) PBMCs. These results suggest that the fractalkine-CX(3)CR1 interaction may contribute to the pathogenesis of canine IBD through migration of IELs.

Toll- and NOD-like receptor mRNA expression in canine sino-nasal aspergillosis and idiopathic lymphoplasmacytic rhinitis

The pathogenesis of canine sino-nasal aspergillosis (SNA) and lymphoplasmacytic rhinitis (LPR) remains poorly understood. The innate immune system is implicated in the etiology of human chronic rhinosinusitis. Therefore, we hypothesized that dysfunction in innate immunity could be implicated in the pathogenesis of SNA and LPR. Expression of messenger RNA (mRNA) encoding Toll-like receptors (TLRs) 1-10 and NOD-like receptors (NODs) 1 and 2 in nasal mucosal biopsies from SNA or LPR dogs was compared with mucosa from healthy controls. Gene expression was quantified using quantitative real-time reverse transcriptase polymerase chain reaction normalized against multiple housekeeper genes. All TLR and NOD genes were quantified in all samples. SNA was associated with significantly increased expression of TLRs 1-4, 6-10; and NOD2, relative to controls. LPR was associated with significantly increased expression of TLRs 1, 2, 6-8, relative to controls. There was significantly more expression of TLRs 1, 4, 6-10 and NOD2 in SNA dogs than in LPR dogs. The significance of these differences in the pathogenesis of these diseases is yet to be determined.

Analysis of gene expression in canine sino-nasal aspergillosis and idiopathic lymphoplasmacytic rhinitis: a transcriptomic analysis

Sino-nasal aspergillosis (SNA) and lymphoplasmacytic rhinitis (LPR) are two common causes of nasal discharge in dog. SNA is typically due to an invasion of Aspergillus fumigatus in the surface of nasal mucosa. The etiology of LPR is poorly understood and a possible implication of fungi is suspected. The purpose of the present study was to explore the immunopathogenesis of these diseases by comparing gene expression in the nasal mucosa from dogs affected by SNA or LPR with healthy dogs, using a canine-specific microarray and quantitative real-time reverse transcriptase polymerase chain reaction for confirmation of the findings of the microarray study. Total RNA was isolated from biopsies of nasal mucosa and gene expression was analyzed via hybridation to the Affymetrix GeneChip(®) Canine Genome 2.0 Array. Selected Affimetrix probes sets identifiers were downloaded into the Database for Annotation, Visualization and Integrated Discovery. Genes of interest were chosen after their fold change and their possible implication in immunopathogenesis of SNA or LPR. The results presented here were in concordance with previous studies on SNA and LPR and highlighted new molecules potentially involved in the pathogenesis of SNA. The over-expression of interleukin (IL)-16, natural killer cell group 7 and chemokine ligand 10 might be related to a potential protective Th1 immunity counterbalanced by other molecules such as DNA-binding protein Ikaros.

Selection of housekeeping genes for normalization of RT-PCR in hypoxic neural stem cells of rat in vitro

Gene expression analysis under various conditions using real-time reverse transcription polymerase chain reaction (RT-PCR) needs reliable control genes. Housekeeping genes are commonly used as the control. However, no validated housekeeping gene is available for study of hypoxic neural stem cell culture. To choose appropriate internal control genes, the expression of eight commonly used housekeeping genes was examined in rat neural stem cell model to find one or more stably expressed genes under hypoxic/ischemic conditions. Two genes, HPRT and RPL13A were identified as the most confidential housekeeping genes in this research by geNorm and NormFinder softwares. As a groundwork, the most stable housekeeping genes for neural stem cells under hypoxic/ischemic conditions are initially investigated and validated in this experiment, which might provide a better understanding for the gene expression study in ischemic and necrotic neural stem cell cultures or in ischemic diseases of the central nervous system (CNS).

Dynamic distribution and tissue tropism of classical swine fever virus in experimentally infected pigs

BACKGROUND

Classical swine fever (CSF), caused by the Classical swine fever virus (CSFV), is an Office International des Epizooties (OIE) notifiable disease. However, we are far from fully understand the distribution, tissue tropism, pathogenesis, replication and excretion of CSFV in pigs. In this report, we investigated the dynamic distribution and tissue tropism of the virus in internal organs of the experimentally infected pigs using real-time RT-PCR and immunohistochemistry (IHC).

RESULTS

A relative quantification real-time PCR was established and used to detect the virus load in internal organs of the experimentally infected pigs. The study revealed that the virus was detected in all 21 of the internal organs and blood collected from pigs at day 1 to day 8 post infections, and had an increasing virus load from day 1 to day 8 post infections. However, there was irregular distribution virus load in most internal organs over the first 2 days post infection. Blood, lymphoid tissue, pancreas and ileum usually contain the highest viral loads, while heart, duodenum and brain show relatively low viral loads.

CONCLUSIONS

All the data suggest that CSFV had an increasing virus load from day 1 to day 8 post infections in experimentally infected pigs detected by real-time RT-PCR, which was in consistent with the result of the IHC staining. The data also show that CSFV was likely to reproduce in blood, lymphoid tissue, pancreas and the ileum, while unlikely to replicate in the heart, duodenum and brain. The results provide a foundation for further clarification of the pathogenic mechanism of CSFV in internal organs, and indicate that blood, lymphoid tissue, pancreas and ileum may be preferred sites of acute infection.

The immunopathology of canine vector-borne diseases

The canine vector-borne infectious diseases (CVBDs) are an emerging problem in veterinary medicine and the zoonotic potential of many of these agents is a significant consideration for human health. The successful diagnosis, treatment and prevention of these infections is dependent upon firm understanding of the underlying immunopathology of the diseases in which there are unique tripartite interactions between the microorganism, the vector and the host immune system. Although significant advances have been made in the areas of molecular speciation and the epidemiology of these infections and their vectors, basic knowledge of the pathology and immunology of the diseases has lagged behind. This review summarizes recent studies of the pathology and host immune response in the major CVBDs (leishmaniosis, babesiosis, ehrlichiosis, hepatozoonosis, anaplasmosis, bartonellosis and borreliosis). The ultimate application of such immunological investigation is the development of effective vaccines. The current commercially available vaccines for canine leishmaniosis, babesiosis and borreliosis are reviewed.

Evaluation of internal control genes for qRT-PCR normalization in tissues and cell culture for antiviral studies of grass carp (Ctenopharyngodon idella)

Real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) has become one of the most commonly used techniques for RNA expression. To obtain more reliable results with biological significance, it requires data normalization using an appropriate internal control gene. Here, we cloned partial sequence of elongation factor 1α (EF1α) gene from grass carp (Ctenopharyngodon idella). The stabilities of four commonly used internal control genes encoding 18S rRNA, β-actin, EF1α, and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were integratedly assessed using the geNorm, NormFinder and BestKeeper programs. Integrative analyses of qRT-PCR data indicated that the stability ranking of the examined genes was 18S rRNA > EF1α > GAPDH > β-actin in gill, head kidney, heart, intestine, liver, muscle, skin, spleen, and trunk kidney tissues in untreated grass carp. When the same calculations were done in spleen tissue at different time points post grass carp reovirus (GCRV) infection, the gene ranking was 18S rRNA > β-actin > GAPDH > EF1α. The rank ordering of expression stability was EF1α > β-actin>18S rRNA > GAPDH in C. idella kidney (CIK) cell culture stimulated by poly(I:C). The recommended ranking was EF1α > GAPDH > β-actin>18S rRNA in CIK cells infected by GCRV. The results indicated that 18S rRNA was the best invariant internal control gene in individual level in grass carp, EF1α was the most suitable in CIK cell culture stimulated by poly(I:C) or infected by GCRV. As an assay, EF1α was employed to examine the changes of Toll-like receptor 3 (TLR3) and melanoma differentiation associated gene 5 (MDA5) after virus infection in CIK cells. These data laid the foundation for more precise results in qRT-PCR studies of gene expression in grass carp.

Leukocyte count affects expression of reference genes in canine whole blood samples

Background

The dog is frequently used as a model for hematologic human diseases. In this study the suitability of nine potential reference genes for quantitative RT-PCR studies in canine whole blood was investigated.

Findings

The expression of these genes was measured in whole blood samples of 263 individual dogs, representing 73 different breeds and a group of 40 mixed breed dogs, categorized into healthy dogs and dogs with internal and hematological diseases, and dogs that underwent a surgical procedure. GeNorm analysis revealed that a combination of 5 to 6 of the most stably expressed genes constituted a stable normalizing factor. Evaluation of the expression revealed different ranking of reference genes in Normfinder and GeNorm. The disease category and the white blood cell count significantly affected reference gene expression.

Conclusions

The discrepancy between the ranking of reference genes in this study by Normfinder and Genorm can be explained by differences between the experimental groups such as "disease category" and "WBC count". This stresses the importance of assessing the expression stability of potential reference genes for gene experiments in canine whole blood anew for each specific experimental condition.

Evaluation of the prognostic significance of BCL6 gene expression in canine high-grade B-cell lymphoma

The clinical usefulness of BCL6 gene expression was evaluated as a prognostic indicator in dogs with high-grade B-cell lymphoma. Forty-four dogs were diagnosed with centroblastic or B-cell immunoblastic type lymphoma according to the updated Kiel classification. BCL6 mRNA expression was measured by real-time PCR and its relationship with prognosis was analyzed. Progression-free and overall survival was not significantly different between the high BCL6 expression group (higher than the median) and the low BCL6 expression group (lower than the median) (P=0.99 and P=0.61, respectively). No correlation between BCL6 and prognosis was observed in this study, which is inconsistent with findings reported for human diffuse large B-cell lymphoma. BCL6 protein expression was not detected in the 11 dogs evaluated by immunohistochemistry. Furthermore, BCL6 protein expression was assessed in 13 archived paraffin-embedded high-grade canine lymphoma tissues and all were also negative. The results suggest that most canine high-grade B-cell lymphomas correspond to human diffuse large B-cell lymphoma with no immunohistochemical expression of BCL6.

Gene expression profile of vascular endothelial growth factor (VEGF) and its receptors in various cell types of the canine lymph node using laser capture microdissection (LCM)

The role of VEGF and its receptors has extensively been studied in tumours. In contrast, the presence and function of VEGF in normal tissues like the lymph node has not been given much attention until now. To study the expression of VEGF, VEGFR-1, VEGFR-2 and VEGFR-3 in the heterogenous cell population of the canine lymph node, laser capture microdissection was used to isolate pure cell fractions of macrophages, lymphocytes, endothelial cells, and capsule cells of the canine lymph node. To clarify if macrophages take up VEGF from the environment or express VEGF, VEGFR-1, VEGFR-2 or VEGFR-3 themselves, the mRNA expression was studied by real-time RT-PCR. After RNA isolation and subsequent analysis with the Agilent 2100 Bioanalyzer only RNA samples with appropriate RNA integrity were used for real-time PCR. For the accurate relative quantification of mRNA expression levels several reference genes were evaluated. It was shown that the reference genes HPRT1 and B2M serve as reliable reference genes for gene expression studies in the canine lymph node. Expression data analysis revealed no significant difference in VEGF expression levels between endothelial cells and the other investigated cells. VEGFR-1 expression was significantly lower in lymphocytes. Also macrophages showed a highly significant lower expression of VEGFR-1 compared to endothelial cells. In addition, the VEGFR-2 expression in lymphocytes and macrophages was significantly lower in comparison to endothelial cells. We were not able to detect VEGFR-3 mRNA in the lymphocyte cell population, in macrophages and cells of the lymph node capsule VEGFR-3 was expressed at very low levels. It was shown that laser capture microdissection in combination with quantitative real-time PCR is a valuable tool for studying the expression patterns of specific cells in their microenvironment. Our results support the hypothesis that VEGF and its receptors have other biological roles besides stimulating angiogenesis in the normal lymph node. These biological functions need to be clarified in further studies.

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.

Evaluation of mucosal bacteria and histopathology, clinical disease activity and expression of Toll-like receptors in German shepherd dogs with chronic enteropathies

The pathogenesis of chronic enteropathies in dogs likely involves an interaction between the intestinal immune system and luminal intestinal bacteria. German shepherd dogs (GSD) are particularly predisposed to chronic enteropathies. The present study sought to evaluate expression patterns of certain pattern recognition receptors of the innate immunity (Toll-like receptors, TLR), clinical disease activity and histopathological severity in GSD with chronic enteropathies. Mucosal biopsies were collected from the duodenum, colon and ileum of 13 affected GSD and 10 healthy greyhounds as controls. Dogs were objectively assessed using published scoring systems for clinical and histological severity of disease. Diversity of the duodenal microbiota was assessed by construction of 16S rRNA gene libraries. Expression of TLR2, TLR4, TLR5 and TLR9 in biopsies of the duodenum, ileum and colon was assessed by quantitative real-time PCR. TLR4 expression was increased in all intestinal segments in GSD, however, TLR5 expression was very low compared to the healthy dogs. The microbiota in the duodenum of GSDs was significantly different to that of the greyhounds, with an over-representation of 16S rRNA gene sequences belonging to the classes of Bacilli, and Erysipelotrichi, and to the orders of Lactobacillales, Actinomycetales and Erysipelotrichales. These findings could point to a distinct pathogenesis of chronic enteropathies in GSD, with differentially high and low expression of TLR4 and TLR5, respectively, and increased proportions of specific members of the Lactobacillales potentially playing a role.

Quantitative analysis of mRNA for 10 different drug resistance factors in dogs with lymphoma

Expression levels of ABCB1, ABCC1, Lung resistance-associated protein (LRP), ABCG2, p53, p21(waf1), Bcl-2, CD40L, glutathione S-transferase alpha (GSTα), and O⁶-methylguanine-DNA-methyltransferase (MGMT) genes, and mutation of p53 gene were examined in 23 dogs with multicentric high-grade lymphoma to explore their association with drug resistance of the tumor cells. Dogs were divided into chemotherapy-sensitive (n=13) and -resistant (n=10) groups according to the response to a 6-month modified version of the University of Wisconsin (UW)-Madison chemotherapy protocol (UW-25), and expression levels of these factors and frequency of p53 gene mutation were compared between groups. No significant differences were observed in expression levels of each factor between groups. However, 4 dogs in the chemotherapy-resistant group showed high expression of ABCB1. No significant difference was observed in the frequency of p53 mutation between groups. A possible association of ABCB1 with resistance to UW-25 was shown, but no uniform mechanism associated with drug resistance could be identified in dogs with lymphoma.

Endothelin-1 production by the canine macrophage cell line DH82: enhanced production in response to microbial challenge

Endothelin-1 (ET-1) is a potent vasoconstrictive peptide which plays an important role in regulating mammalian cardiovascular development and homeostasis. Originally identified as a factor released by vascular endothelial cells, ET-1 is now recognized as a product of numerous cells and tissues with demonstrated involvement in an array of physiological and pathological processes. An area of great interest is the production of ET-1 by mononuclear cells (monocytes and macrophages) and its role in inflammation. We report that the canine macrophage cell line, DH82, constitutively secretes both ET-1 and its biologically inactive precursor big ET-1. The production of both peptides was increased following stimulation with lipopolysaccharide (endotoxin) from gram-negative bacteria. ET-1 production was also increased in response to stimulation with intact and viable gram-positive and gram-negative bacteria. In addition to producing ET-1, DH82 cells express transcripts encoding two receptors for the ET-1 peptide (ET(A) and ET(B) receptors) and an enzyme involved in the conversion of big ET-1 to ET-1. The constitutive secretion of ET-1 and the expression of ET(A) and ET(B) receptors may be related to the malignant origin of this cell line. Our results are the first report of ET-1 production by a canine cell line and provide the basis for further investigation into the role of ET-1 during infection and inflammation.

Suitable reference gene selection for different strains and developmental stages of the carmine spider mite, Tetranychus cinnabarinus, using quantitative real-time PCR

Reference genes are used as internal controls in gene expression studies, but their expression levels vary according to tissue types and experimental treatments. Quantitative real-time PCR (qPCR) is the most sensitive technique for transcript quantification provided that gene transcription patterns are normalized to an evaluated reference gene. In this study, the suitability of eight commonly used genes (β-actin, 5.8SrRNA, α-TUB, GAPDH, RPL13a, RPS18, TBP, SDHA) were cloned and investigated to find the most stable candidates for normalizing real-time PCR data generated from the four different strains (abamectin-resistant, fenpropathrin-resistant, omethoate-resistant, and susceptible strains) and different developmental stages (eggs, protonymphs, nymphs, and adults) of carmine spider mite, Tetranychus cinnabarinus (Boisduval) (Acarina: Tetranychidae). The stability of gene expression was assessed using two different analysis programs, geNorm and NormFinder. Using these analyses, RPS18 and 5.8SrRNA had the most stable expression regardless of the four different strains, whereas RPS18 and α-TUB were expressed most stably in different developmental stages.

Quantitative TaqMan real-time PCR assays for gene expression normalisation in feline tissues

Background

Gene expression analysis is an important tool in contemporary research, with real-time PCR as the method of choice for quantifying transcription levels. Co-analysis of suitable reference genes is crucial for accurate expression normalisation. Reference gene expression may vary, e.g., among species or tissues; thus, candidate genes must be tested prior to use in expression studies. The domestic cat is an important study subject in both medical research and veterinary medicine. The aim of the present study was to develop TaqMan^® real-time PCR assays for eight potential reference genes and to test their applicability for feline samples, including blood, lymphoid, endocrine, and gastrointestinal tissues from healthy cats, and neoplastic tissues from FeLV-infected cats.

Results

RNA extraction from tissues was optimised for minimal genomic DNA (gDNA) contamination without use of a DNase treatment. Real-time PCR assays were established and optimised for v-abl Abelson murine leukaemia viral oncogene homolog (ABL), β-actin (ACTB), β-2-microglobulin (B2M), β-glucuronidase (GUSB), hydroxymethyl-bilane synthase (HMBS), hypoxanthine phosphoribosyltransferase (HPRT), ribosomal protein S7 (RPS7), and tryptophan 5-monooxygenase activation protein, zeta polypeptide (YWHAZ). The presence of pseudogenes was confirmed for four of the eight investigated genes (ACTB, HPRT, RPS7, and YWHAZ). The assays were tested together with previously developed TaqMan^® assays for feline glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the universal 18S rRNA gene. Significant differences were found among the expression levels of the ten candidate reference genes, with a ~10⁶-fold expression difference between the most abundant (18S rRNA) and the least abundant genes (ABL, GUSB, and HMBS). The expression stability determined by the geNorm and NormFinder programs differed significantly. Using the ANOVA-based NormFinder program, RPS7 was the most stable gene in the tissues studied, followed by ACTB and ABL; B2M, HPRT, and the 18S rRNA genes were the least stable ones.

Conclusion

The reference gene expression stability varied considerably among the feline tissues investigated. No tested gene was optimal for normalisation in all tissues. For the majority of the tissues, two to three reference genes were necessary for accurate normalisation. The present study yields essential information on the correct choice of feline reference genes depending on the tissues analysed.

Expression of Toll-like receptor 2 in duodenal biopsies from dogs with inflammatory bowel disease is associated with severity of disease

There is growing evidence that aberrant innate immune responses towards the bacterial flora of the gut play a role in the pathogenesis of canine inflammatory bowel disease (IBD). Toll-like receptors (TLR) play an important role as primary sensors of invading pathogens and have gained significant attention in human IBD as differential expression and polymorphisms of certain TLR have been shown to occur in ulcerative colitis (UC) and Crohn's disease (CD). The aim of the current study was to evaluate the expression of two TLR important for recognition of commensals in the gut. TLR2 and TLR4 mRNA expression in duodenal biopsies from dogs with IBD was measured and correlated with clinical and histological disease severity. Endoscopic duodenal biopsies from 20 clinical cases and 7 healthy control dogs were used to extract mRNA. TLR2 and TLR4 mRNA expression was assessed using quantitative real-time PCR. TLR2 mRNA expression was significantly increased in the IBD dogs compared to controls, whereas TLR4 mRNA expression was similar in IBD and control cases. In addition, TLR2 mRNA expression was mildly correlated with clinical severity of disease, however, there was no correlation between TLR2 expression and histological severity of disease.

Validation of suitable house keeping genes for hypoxia-cultured human chondrocytes

Background

Hypoxic culturing of chondrocytes is gaining increasing interest in cartilage research. Culturing of chondrocytes under low oxygen tension has shown several advantages, among them increased synthesis of extracellular matrix and increased redifferentiation of dedifferentiated chondrocytes. Quantitative gene expression analyses such as quantitative real-time PCR (qRT-PCR) are powerful tools in the investigation of underlying mechanisms of cell behavior and are used routinely for differentiation and phenotype assays. However, the genes used for normalization in normoxic cell-cultures might not be suitable in the hypoxic environment. The objective of this study was to determine hypoxia-stable housekeeping genes (HKG) for quantitative real-time PCR (qRT-PCR) in human chondrocytes cultured in 21%, 5% and 1% oxygen by geNorm and NormFinder analyses.

Results

The chondrocytic response to the hypoxic challange was validated by a significant increase in expression of the hypoxia-inducible gene ankyrin repeat 37 as well as SOX9 in hypoxia. When cultured on the 3-dimentional (3D) scaffold TATA-binding protein (TBP) exhibited the highest expression stability with NormFinder while Ribosomal protein L13a (RPL13A) and beta2-microglobulin (B2M) were the most stable using geNorm analysis. In monolayer RPL13A were the most stable gene using NormFinder, while geNorm assessed RPL13A and human RNA polymerase II (RPII) as most stable. When examining the combination of (3D) culturing and monolayer RPL13A and B2M showed the highest expression stability from geNorm analysis while RPL13A also showed the highest expression stability using NormFinder. Often used HKG such as beta actin (ACTB) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were the most unstable genes investigated in all comparisons. The pairwise variations for the two most stable HKG in each group were all below the cut-off value of 0.15, suggesting that the two most stable HKG from geNorm analysis would be sufficient for qRT-PCR.

Conclusion

All data combined we recommend RPL13A, B2M and RPII as the best choice for qRT-PCR analyses when comparing normoxic and hypoxic cultured human chondrocytes although other genes might also be suitable. However, the matching of HKG to target genes by means of a thorough investigation of the stability in each study would always be preferable.

Seasonal upregulation of fatty acid transporters in flight muscles of migratory white-throated sparrows (Zonotrichia albicollis)

Endurance flights of birds, some known to last several days, can only be sustained by high rates of fatty acid uptake by flight muscles. Previous research in migratory shorebirds indicates that this is made possible in part by very high concentrations of cytosolic heart-type fatty acid binding protein(H-FABP), which is substantially upregulated during migratory seasons. We investigated if H-FABP and other components of muscle fatty acid transport also increase during these seasons in a passerine species, the white-throated sparrow (Zonotrichia albicollis). Fatty acid translocase (FAT/CD36)and plasma-membrane fatty acid binding protein (FABPpm) are well characterized mammalian proteins that facilitate transport of fatty acid through the muscle membrane, and in this study they were identified for the first time in birds. We used quantitative PCR to measure mRNA of FAT/CD36, FABPpm and H-FABP and immunoblotting to measure protein expression of FABPpm and H-FABP in the pectoralis muscles of sparrows captured in migratory (spring, fall) and non-migratory (winter) seasons. During migratory seasons, mRNA expression of these genes increased 70–1000% above wintering levels, while protein expression of H-FABP and FABPpm increased 43% and 110% above wintering levels. Activities of key metabolic enzymes, 3-hydroxyacyl-CoA-dehydrogenase (HOAD),carnitine palmitoyl transferase II (CPT II), and citrate synthase (CS) also increased (90–110%) in pectoralis muscles of migrant birds. These results support the hypothesis that enhanced protein-mediated transport of fatty acids from the circulation into muscle is a key component of the changes in muscle biochemistry required for migration in birds.

Molecular cloning of the canine fragile histidine triad (FHIT) gene and Fhit protein expression in canine peripheral blood mononuclear cells

A fragile histidine triad (FHIT) gene has been studied as a tumor-associated gene in humans. The aberrant FHIT gene and its protein expression have been reported in many types of human cancers. The present study explored the canine FHIT gene structure and its protein expression in the peripheral blood mononuclear cells of healthy dogs by RT-PCR, RACE and immunoblot analysis. The obtained canine FHIT gene contained nine small exons and was located on canine chromosome 20. Furthermore, we identified an alternative splicing form of the FHIT transcript. The deduced amino acid sequence was well conserved between species, and anti-human Fhit antibody could be used to detect the canine Fhit protein. These findings will be useful for future research.

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.