EXPRESSION OF THE SMALL PROTEOGLYCANS BIGLYCAN AND DECORIN IN THE ADULT HUMAN TESTIS

The genes coding for the core proteins of the small chondroitin sulfat e/dermatan sulfate proteoglycans (PGs) biglycan and decorin are both e xpressed in the adult human testis. Northern hybridization of human te sticular mRNA indicated the presence of one specific transcript for bi glycan at 2.6 kb and two specific transcripts for decorin at 1.6 kb an d 1.9 kb. In situ hybridization localized the mRNA for biglycan to the peritubular tissue as well as to the tunica muscularis and adventitia of arteries. Leydig cells and cells of the seminiferous epithelium bo th proved to be negative. For decorin mRNA, strong signals were found over single, dispersed interstitial cells (possibly fibroblasts), the adventitious layer of large arteries, and the perivascular tissue cell s of small arteries, arterioles, and capillaries. In the peritubular f ell layers, decorin gene expression was comparably lower and was restr icted to the outer fibroblast layers. Germ cells and Sertoli cells wer e devoid of any positive signal. Immunoblot analysis using specific an tisera directed against the core proteins of biglycan and decorin conf irmed their presence in chondroitin ABC lyase-treated proteinaceous ex tracts of the human testis. Immunohistochemistry for biglycan showed a good spatial correlation with the in situ hybridization data and reve aled in addition a nonuniform distribution of the antigenic material, which was located predominantly over peritubular myoid cells and the a dventitious layer of arteries. Together these results indicate that th e expression of both genes in the human testis is differentially regul ated, despite the overall similarity of their protein products, and su ggest distinct roles for these PGs in testicular function