Recently, the spermatogenic cell has been focused in male sterility. There are some reports on fertilization and embryonic developmental ability of spermatid. Deficiency of fertilization or developmental arrest frequently appears due to the ability. Functional immaturity is also observed in spite of abnormality of karyotype in spermatids. However, a functional difference between spermatids and spermatozoa is not clarified. In this study, fertilization and developmental ability of the spermatid were examined by the microinjection using immature spermatid including the round spermatid, elongating spermatid, elongated spermatid and intratesticular spermatozoa derived from three different mice strains; ddY, ICR and B6D2F1. Mature female mice were superovulated with PMSG and hCG. Cumulus-oosytes complex were obtained from their oviducts, and cumulus cells were removed from MII oocytes by hyaluronidase and pippeting. Spermatids were collected from mature male testis, and were injected into MII oocytes using a micromanipulator. Manipulated embryos were cultured in CZB medium, and their ability for development was examined. Epididymal spermatozoa from the three strains were used as control group. The fertilization rate was correlated with the spermatogenic stage. In embryonic developmental rate, on the other hand, there were no significant difference between the control and experimental embryos. The data however showed that elongating, elongated and round spermatid slightly deteriorated the embryonic development. These results suggest that the ability of the embryonic activation depend on the spermatid metamorphose.
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