Immunohistochemical analysis of molecular events in tubulo-interstitial fibrosis in a mouse model of diffuse mesangial sclerosis (ICGN strain)

Comparison of renal lesions in cats and dogs using pathomorphological and ımmunohistochemical methods

We investigated the pathogenesis of chronic renal fibrosis in cats and dogs using immunohistochemistry. We used the avidin-biotin complex peroxidase (ABC-P) method with antibodies against transforming growth factor-β1, cytokeratin, E-cadherin, S100A4, alpha-smooth muscle actin, vimentin and nestin to determine whether tubule epithelial cells had undergone epithelial-mesenchymal transformation (EMT) that resulted in loss of epithelial cells and an increased number of mesenchymal cells. Although nephrosis was more common in dogs, nephritis was more common in cats; these pathologies developed in both kidneys. We found that EMT participated in the pathogenesis of renal fibrosis in both dogs and cats.

Genetic background strongly influences the severity of glomerulosclerosis in mice

The ICGN mouse strain is a glomerulosclerosis (GS) model that shows characteristic proteinuria, podocyte morphological abnormalities and increased extracellular matrix accumulation in the glomeruli, which are the final common pathology associated with a variety of kidney diseases leading to end-stage renal failure. Previously, we performed a quantitative trait locus (QTL) analysis to identify the causative genes for GS in ICGN mice and found the deletion mutation of the tensin2 (Tns2) gene that creates both a premature stop codon and dramatically decreases mRNA expression levels within the region of the major QTL (this mutation was designated Tns2(nep)). The severity of GS varies considerably in humans and other animals, indicating the influence of several genes controlling the disease phenotype. In this study, to identify the modifier/resistant gene(s) for GS, we produced congenic strains carrying the Tns2(nep) mutation on the C57BL/6J (B6) genetic background and analyzed GS severity. Interestingly, the B6 congenic mice exhibited milder phenotypes than the ICGN strain mice. The results suggest that B6 mice have a modifier(s) of GS resistance. Therefore, identification of the modifier loci in B6 mice will provide important new information regarding gene interactions controlling GS.

Proteinuria-induced chronic kidney disease in the ICGN/Oa mice with a mutation of Tensin2 gene

ICGN/Oa mice are used to study the pathophysiological mechanisms underlying proteinuria-induced chronic kidney disease (CKD). Recently, a mutation of tensin2 gene (Tns2) was suggested to be responsible for proteinuria in the inbred ICGN mice. We identified the wild-type (+/+), heterozygous (+/nep), and homozygous (nep/nep) ICGN/Oa mice by PCR assay. The homozygotes developed proteinuria, resulting in nephrotic syndrome (NS) as early as 5 weeks and CKD by 15 weeks. However, the heterozygotes did not show the symptoms of these renal failures. These results indicate that the homozygous tensin2 mutation is necessary for the ICGN/Oa mice to develop proteinuria-induced CKD. Furthermore, we examined the time course of tubulointerstitial fibrosis and the kinetics of tubular epithelial cells (TECs) in the ICGN/Oa mice using immunohistochemical and TUNEL assays. In the renal parenchyma of the five-week-old homozygotes, the expression of alpha-SMA and type I collagen were higher than those in the age-matched wild-type. Additionally, increased TEC proliferation was found at 5 weeks, and increased TEC apoptosis was by 15 weeks in the homozygotes. Tubulointerstitial fibrosis precedes TEC apoptosis in the proteinuria-induced CKD model mice, and that tubulointerstitial fibrosis may be the triggering event of the disease.