[Study on the distribution of collagen fibers in the bifurcating area of cerebral arterioles of Wistar rats].

It was previously reported that Mato cells (Mato's fluorescent granular perithelial cells) were frequently localized in the bifurcating areas of cerebral arterioles and occasionally, collagen fibers appeared close to Mato cells of aged rats. It has also been established that Mato cells were scavenger cells in the cerebral tissue and provided with MHC-class II antigen. The present paper deals with the relationship between the distribution of collagen fibers and Mato cells in the bifurcating area of cerebral arterioles. 6 Wistar rats (3 rats aged 4 months and 3 rats aged 16 months) were employed for this electron microscopical study. They were perfused with the mixture of paraform-glutaraldehyde solution, and cerebral cortices were excised and fixed with 1% osmic solution and embedded in Epon 812. In order to observe the bifurcating area of cerebral arterioles, serial semithin sections cutting with the diamond knife were stained with toluidine blue, and checked under the light microscope. After obtaining available regions, serial thin sections were stained with uranyl acetate and lead nitrate, and observed with Hitach H7600 electron microscope. In order to survey the distribution of collagen fibers, 2 groups of the specimens of 4 months old (2 rats) and 5 groups of specimens of 16 months old rats (2 rats) were prepared. Each group consisted of serial 10 thin sections. Other rats of young and aged were used for complementary use. From the observation, it is confirmed that in the cerebral arteriole, collagen fibers are localized only in the interstices around Mato cells, and the fibers appear in a small quantity in the rats aged 4 months, while a certain amounts of the fibers are arranged sporadically in the rats aged 16 months. However, no collagen fibers can be detected in the subendothelial space and in the interstices among smooth muscle cells of cerebral arteriole. If Mato cells lack in some regions of cerebral arterioles, collagen fibers cannot be recognized. The following is also to be stressed that no fibroblastoid cells do appear in any serial sections of cerebral arterioles. From these findings, it seems possible that Mato cells play a principal role in the formation of collagen fibers in the cerebral arterioles, and associate with the sclerosis of cerebral arterioles.