Increased expression of type III and type IV collagen in diabetic nephropathy

Inflammation, neovascularization and intra-plaque hemorrhage are associated with increased reparative collagen content: implication for plaque progression in diabetic atherosclerosis

Sustained inflammation may stimulate a reparative process increasing early reparative type III collagen synthesis, promoting atherosclerotic plaque progression. We evaluated inflammation, neovascularization, intra-plaque hemorrhage (IPH), and collagen deposition in human aortic atherosclerotic plaques from patients with and without diabetes mellitus (DM). Plaques were procured at autopsy from lower thoracic and abdominal aorta from DM (n = 20) and non-DM (n = 22) patients. Inflammation and neovascularization were quantified by double-label immunochemistry and the IPH grade was scored using H&E-stained sections. Type I and type III collagens were quantified using Picro-Sirius red stain with polarization microscopy and computerized planimetry. In non-DM plaques, 27%, 40%, and 33% had mild, moderate and severe inflammation in the fibrous cap and shoulder compared with 2%, 30% and 68% in DM plaques (p < 0.001). The geometric mean neovessel count was increased in DM versus non-DM plaques (140 [95% CI: 119-165] versus 59 [95% CI: 51-70]; p < 0.001). The IPH grade was increased in DM verses non-DM plaques (0.82 ± 0.11 versus 0.29 ± 0.11; p < 0.001) (percentage grade). The density of type III was increased in DM plaques (0.16 ± 0.01 versus 0.06 ± 0.01; p < 0.001) with a non-significant reduction in type I density in DM when compared with non-DM (0.28 ± 0.03 versus 0.33 ± 0.03; p = 0.303) (content per mm²). The increase in type III collagen content correlated with total neovessel content (r = 0.58; p < 0.001) in DM plaques. In conclusion, our study suggests that enhanced type III collagen deposition was associated with inflammation, neovascularization and IPH, and may be a contributing factor in DM plaque progression.

Significance of increased accumulation of type VI collagen and transforming growth factor beta 1 in tubulointerstitial damage in hypertensive nephrosclerosis: an immunohistochemical study

The distribution of type VI collagen and transforming growth factor beta 1 (TGF beta 1) was studied by immunohistochemistry in 12 renal biopsy specimens of hypertensive nephrosclerosis and five control cases. In control kidneys, the immunostaining of type VI collagen was found in the mesangium, glomerular basement membrane and tubular basement membrane. For TGF beta 1, mesangium, glomerular basement membrane, tubular basement membrane and tubular epithelial cells stained positively in the control kidneys. In contrast to the control cases, markedly increased immunostaining for both type VI collagen and TGF beta 1 was consistently observed in tubulointerstitial damage in hypertensive nephrosclerosis. These immunohistochemical findings provide the evidence for a parallel increase of both type VI collagen and TGF beta 1 during the process of tubulointerstitial injury in hypertensive nephrosclerosis. From the results of the present study, it is speculated that TGF beta 1 may contribute to the tubulointerstitial injury by stimulating increased synthesis of various extracellular matrix including type VI collagen.

Immunohistochemical analysis of type III and IV collagens in tubulointerstitial damage in human benign nephrosclerosis

Prolonged hypertension causes structural changes including glomerulosclerosis and tubulointerstitial damage of the kidney, termed benign nephrosclerosis. It is generally accepted that, in benign nephrosclerosis, increased accumulation of extracellular matrix in the glomeruli results in glomerulosclerosis. Little is known, however, about the possible role of the extracellular matrix in the tubulointerstitial damage in benign nephrosclerosis. In this study, the possible roles of type IV basement-membrane collagen and type III interstitial collagen in tubulointerstitial damage caused by hypertension were explored. Immunohistochemical techniques were used to investigate the distribution of type III and type IV collagens in the kidney sections of 15 patients with benign nephrosclerosis with tubulointerstitial damage and in 10 controls. In the control renal sections strong immunostaining for type III collagen was found in the interstitium and immunostaining for type IV collagen was present in the tubular basement membrane and weakly in the interstitium. In the patients with tubulointerstitial damage there was increased immunostaining for both type III and type IV collagens in the expanded interstitium and damaged tubules than was found in the control kidney sections. These findings indicate that increased accumulation of both type III and type IV collagens might play a significant role in the tubulointerstitial damage in benign nephrosclerosis.

Suppression of mesangial-cell proliferation by trapidil in glomerulonephritis induced by anti-thymocyte serum in rats

Trapadil (Mochida Pharmaceuticals, Japan), an antiplatelet drug, suppresses the growth of several cell types and is thought to antagonize platelet-derived growth factor. The effects of trapidil on mesangial-cell proliferation in glomerulonephritis induced by anti-thymocyte serum in Wistar rats were investigated. Control rats were treated with phosphate-buffered saline (group I); group II rats were injected with a single dose of anti-thymocyte serum (8 ml/kg body weight), and group III rats were treated with both a single dose of anti-thymocyte serum (8 ml/kg body weight) and with trapidil (5 mg/kg body weight/day). Three rats in each group were killed on day 3, and the other three on day 10. Control rats showed no significant histological changes on day 3 or day 10. In group II, on day 3, there was a marked decrease in glomerular cell numbers, with mesangiolysis. Histologically severe mesangial-cell proliferation with expansion of mesangial areas was noted on day 10. None of the rats in group III showed mesangial alterations, histologically, indicating that mesangial-cell proliferation was suppressed by trapidil. This suppression may result from antagonism of the binding of platelet-derived growth factor to the specific surface receptors in the mesangial cells. Trapidil may have clinical value in the treatment of mesangial-cell proliferative glomerular diseases.

Synthesis of type III collagen and type IV collagen by tubular epithelial cells in diabetic nephropathy

Overproduction of extracellular matrix (ECM) is considered to be primarily responsible for both glomerular and tubulointerstitial (TI) changes in diabetic nephropathy (DN). To clarify the possible role of the collagens in TI damage in DN, type III interstitial collagen and type IV basement membrane collagen were studied in 10 cases of DN and 10 control cases by immunohistochemistry and in situ hybridization techniques. In control cases, no immunostaining for type III collagen was found in the renal tubules, while strongly positive in the adjacent interstitium. On the other hand, type IV collagen was found weakly in the tubular basement membrane (TBM) in control cases. In DN, increased immunostaining for both type III and type IV collagens were found in the damaged tubulointenstitium (TI). To determine the sources of these collagens in TI damage, non-radioactive in situ hybridization was performed utilizing thymine-thymine (T-T) dimerized synthetic oligonucleotides complementary to either human pro alpha 1 (III) chain or pro alpha 1 (IV) chain mRNA as probe. In normal tubules, tubular epithelial cells were not uniformly but persistently positive for pro alpha 1 (IV) mRNA. Meanwhile, no specifically detectable positive hybridization signals for pro alpha 1 (III) mRNA was found in the normal tubular epithelial cells. Accelerated synthesis of both type III and type IV collagens by tubular epithelial cells was noted in TI damage in DN. From the results we concluded that excessive synthesis of both type III and type IV collagens by tubular epithelial cells might significantly contribute to the TI damage found in DN.