Differentiation of human round spermatids into motile spermatozoa through in vitro coculture with Vero cells

Purpose This study was undertaken to examine whether human early round spermatids will differentiate in an in vitro coculture with Vero cells. Methods A total of 1450 and 400 isolated early round spermatids mechanically collected from two non‐obstructive and three obstructive azoospermic men with a normal karyotype were cocultured on Vero cell monolayers in minimum essential medium plus 10% fetal bovine serum, with or without 50 or 100 IU/L FSH and 1 or 10 μmol/L testosterone, at 32.5°C, in an environment of 5% CO 2 in air. Morphological changes of the spermatids were observed microscopically. Results After 7 days of coculture, almost half (40–50%) of the round spermatids from both non‐obstructive and obstructive azoospermic men resumed spermiogenesis in vitro. Only cells from the latter patients gave rise to spermatozoa, a few of which had a motile flagellum. Low concentrations of FSH and testosterone increased the percentage of in vitro spermiogenesis. Conclusions Isolated round spermatids can resume spermiogenesis in vitro when cocultured on a Vero cell monolayer.