Influence of sperm maturation and fertilizing capacity by secretions of male and female reproductive tract epithelia

Sperm maturation or fertilizing ability is not intrinsic to sperm themselves but acquired during their transit through the male and female reproductive tracts. The sperm maturation process is dependent on the luminal microenvironments regulated by the secretory and absorptive activities of the epithelial cells lining along those tracts. The present study aimed to investigate the influences of secretions by reproductive tract epithelial cells (epididymal epithelium and endometrium) on sperm functions using epithelium-sperm co-culture system in conjunct with the techniques of electrophysiology, molecular biology, immunohistochemistry, etc..;The results demonstrated that the caput epididymal epithelium could induce motility of the co-cultured immature spermatozoa while cauda epididymal epithelium appeared to suppress the vigor movement of the co-cultured mature spermatozoa. On the other hand, sperm exerted effect on the co-cultured epithelia, affecting their secretory activity, as demonstrated by decreased short circuit current response to a physiological regulator, extracellular ATP. This effect was more prominently observed in the cauda than the caput epididymal epithelial cells. These observations are consistent with functions of caput and cauda epididymis which have been proved to be mainly responsible for sperm maturation and storage, respectively.;The present study also investigated the influence of uterine CFTR-mediated HCO3- secretion on sperm fertilizing capacity using co-culture system. Sperm motility, fertilizing capacity were examined by computer-aided sperm analysis (CASA), chlortetracycline (CTC) and in vitro fertilization (IVF) assays. The results showed that co-culture with endometrium was critical to the fertilizing capacity of sperm. The percentage of motility, capacitation and successful fertilization of sperm were significantly attenuated after co-culture with CFTR-defective cells, including CFTR antisense treated endometrial epithelial cells or defective HCO3- -secreting CF cells. The present finding confirmed that CFTR-mediated uterine HCO3--secretion plays critical role in sperm fertilizing capacity and also suggested that impaired HCO3 --secretion may result in the reduced female fertility as seen in cystic fibrosis.;Taken together, the present study has demonstrated that the secretions of the epithelial cells lining along male and female reproductive tracts, particularly the epididymis and uterus, play critical roles in sperm maturation and fertilizing capacity. The information obtained in this study may provide grounds for development of treatment methods for infertility and new strategies for contraception. (Abstract shortened by UMI.).