Biophysical mechanism-mediated time-dependent effect on sperm of human and monkey vas implanted polyelectrolyte...

To determine the short and long-term morphological effects on sperm as induced by intra-vas alteration of pH and electrical charge.

Desired biophysical influences were obtained by injection of reversible inhibition of sperm under guidance (RISUG) into the lumen of the vas deferens of human subjects and the monkey. RISUG is a polyelectrolyte hydrogel complex of styrene maleic anhydride (SMA) and dimethyl sulfoxide (DMSO) which generates an electrostatic charge and also lowers in a near space of pH domain. The morphology of sperm was examined by light microscopy, scanning and transmission electron microscopy. Human study enabled semen collection by masturbation as early as 3 h after injection and studies extended up to 6 months. In the monkey, on vas excision after RISUG implantation, sperm characteristics were examined in serial sections.

Semenology in clinical studies and histological data of the monkey showed a time-sequenced sperm plasma membrane, tail mitochondria and nuclear decondensation alterations in sperm structural components, which beared marked similarity to changes in the sperm head and tail during capacitation and entry into the ovum.

The findings provide a means of causing such changes in the sperm that inhibit the fertilizing ability before the nucleus is affected. Therefore achieving non-obstructive vas-based contraception, without genotoxic or teratogenic effects caused by infertile sperm passing into the semen, is feasible.