Evidence of beta 1 integrins and fibronectin on spermatogenic cells in human testis

Interactions between human spermatozoa and oocytes are an essential event in the process of fertilization. Cell-cell and cell-matrix interactions in somatic cells are mediated by adhesion molecules such as beta 1 integrins (very late antigens; VLA). Therefore, we investigated the expression of beta 1 integrins and the matrix proteins collagen IV, fibronectin and laminin in human testis by immunohistology. Monoclonal antibodies against the beta chain of beta 1 integrins reacted with the basement membrane of the tubuli seminiferi, spermatocytes, spermatids and testicular spermatozoa. The alpha 3, -5 and -6 chains of beta 1 integrins showed the same pattern, whereas, the alpha 1, -2 and -4 chains could not be detected on spermatogenic cells. These VLA subunits were localized on endothelial cells, leukocytes and basement membranes. Matrix proteins such as laminin, collagen IV and fibronectin were detectable as components of basement membranes in human testis. Germinal cells except spermatogonia expressed fibronectin only. These results demonstrate that beta 1 integrins and matrix proteins in human testis are normally expressed on somatic tissue and that germinal cells, especially spermatocytes, spermatids and spermatozoa show positive reactions with antibodies against the VLA-3, -5 and -6 complexes and fibronectin. These findings suggest a production of beta 1 integrins and fibronectin during the spermatogenesis and a role of these proteins in adhesive mechanisms of spermatozoa similar to somatic cell-cell or cell-matrix interactions.