Role of epididymal anti sticking factor in sperm capacitation

Sperm capacitation depends on several features like hormones, ions, intracellular signaling, sperm associated molecules, etc. Anti sticking factor (ASF) is a novel sperm surface associated glycoprotein isolated from epididymal plasma. Function of ASF in vivo has not been revealed yet. The current study is an attempt to highlight the surface localization of ASF and corresponding biochemical changes that occurs in sperm cells during in vitro capacitation. In the presence of 1 nM ASF, percentage of bicarbonate and BSA induced capacitated cells in modified Tyrode medium (7.2) decreased from 72.45% to 16.25% as per Merocyanine 540 (M540)/DAPI stained flowcytometric analysis. Indirect immunocytostaining and western blot analysis shows that the amount of sperm surface bound residual ASF decline during in vitro capacitation. ASF at its effective concentrations notably reduced the bicarbonate and BSA induced cholesterol efflux. These data help in concluding ASF as a majorly responsible molecule that maintains caprine sperm membrane integrity by inhibiting cholesterol efflux. As the capacitation process, progress at in vitro condition, ASF is found to be released from the sperm surface and cell moved from non-capacitated to the capacitated state.