Glomerular expression of type III and type IV collagens in benign nephrosclerosis: immunohistochemical and in situ hybridization study.

The development of glomerular sclerosis in benign nephrosclerosis (BNS) was studied. We investigated the intraglomerular expression of type III and IV collagens and their mRNAs by immunohistochemistry and by the in situ hybridization method. Formalin-fixed paraffin sections from 28 patients with BNS and 10 control cases were stained by the avidin-biotin complex (ABC) method using monoclonal antibodies for human type III and IV collagens. In the course of the sclerotic process of the glomerulus in BNS, the glomerular staining intensity of type IV collagen increased. The strongest staining was observed in the glomerulus at the early sclerotic stage, and intensity decreased slightly at the later stages. Although type III collagen was absent in normal and nonsclerotic glomeruli, peripheral regions of the sclerotic glomeruli were positive at the early sclerotic stage. Later, type III collagen was diffusely observed in the completely hyalinized glomeruli. The expression of type III and type IV collagen mRNAs was detected in the glomeruli of BNS by the non-radioactive in situ hybridization method using thymine-thymine (T-T) dimerized synthetic oligonucleotides. The number of mRNA positive cells for type III and type IV collagens increased at the presclerotic and early sclerotic stages. But these cells gradually decreased in number as glomerular sclerosis developed. We concluded that type III collagen was presumably synthesized by the intraglomerular cells and may contribute to the development of glomerular sclerosis in BNS along with type IV collagen.