The expression of αv, α5, β1, and β3 integrin chains on ejaculated human spermatozoa varies with their functional state

Evidence has been presented suggesting the involvement of integrins and their ligands in mammalian fertilization. In this study we asked whether the alpha(5), alpha(v), beta(1) and beta(3) integrin chains, which form receptors for fibronectin and vitronectin, are present on human spermatozoa. Fresh ejaculate spermatozoa and capacitated spermatozoa, before and after a calcium ionophore (A23187)-induced acrosome reaction, were either fixed and their reaction with anti-integrin monoclonal antibodies detected by immunoperoxidase staining or studied without fixation, using cytofluorimetric scanning. Expression of specific integrin chains varied with the functional state of spermatozoa. The alpha(5) chain was not detected on fresh living spermatozoa, but was present on capacitated spermatozoa, whether fixed or living. The pattern of beta(1) expression on living spermatozoa paralleled that of alpha(5). No further increase in the expression of either alpha(5) or beta(1) was observed following an ionophore-promoted acrosome reaction. In contrast, alpha(v) was detected on neither fresh, living ejaculate spermatozoa, nor following capacitation (<10% reactive). The percentage of alpha(v) positive cells increased substantially following ionophore exposure. Expression of beta(3) was similar to alpha(v) and the percentage of cells displaying beta(3) correlated with the proportion of spermatozoa that had undergone an acrosome reaction, following ionophore exposure. These results indicate that the expression of integrins on spermatozoa is dynamic, varying with their functional state and that integrin receptors for fibronectin (alpha(5)beta(1)) become apparent on the spermatozoan surface during capacitation and vitronectin (alpha(v)beta(3)) following the acrosome reaction.