Sperm phagocytosis by corona cells in a human in vitro fertilization system.

Clumps of corona cells were separated from oocytes at the moment of fertilization control and were subsequently processed and cut into 1-mu sections to study their general morphologic patterns. This study revealed an extensive phagocytosis of spermatozoa by corona cells. Clumps of mural granulosa cells of comparable size, recovered from follicular aspirates and incubated with spermatozoa, did not show the same extent of phagocytotic activity. The different nature of extracellular material could prevent penetration of the granulosa cell masses and thus a close contact between spermatozoa and granulosa cells. In our limited number of studied cases there was no indication of an aberrant phagocytosis pattern in coronas from polyspermic eggs or from oocytes that did not become fertilized. On the other hand, sperm penetration, as revealed by the sperm/corona ratio, was significantly higher in coronas derived from polyspermic eggs compared with those from unfertilized oocytes.