The rates of premature chromosome condensation and embryo development after injection of irradiated sperms into hamster oocytes

Irradiation is one of the major causes of induced sperm DNA damage. Various studies suggested a relation between sperm DNA damage and fertilization rate after intra-cytoplasmic sperm injection (ICSI).

In this study, fertilization rate and premature chromosome condensation (PCC) formation after ICSI of hamster oocytes with irradiated sperms from normal and oligosperm individuals was investigated.

Human sperms were classified according to counts to normal and oligosperm. Ten samples were used for each group. Golden hamster oocytes were retrieved after super ovulation by PMSG and HCG injection. From retrieved oocytes, 468 were in metaphase II. Control and 4 Gy gamma irradiated sperms were then injected into oocytes. After pronuclei formation in injected oocytes and formation of 8 cells embryos, slides were prepared using Tarkowskie''s standard air-drying technique. The frequency of embryos and PCC were analyzed using 1000× microscope after staining in 5% Giemsa.

The extent of embryo development in oocytes injected by irradiated sperms was lower than those injected by non-irradiated sperms (p=0.0001). The frequency of PCC in failed fertilized oocytes was significantly higher in oligosperms (46%) compared with normal ones (0%), but there was no significant difference between irradiated and non-irradiated samples in each group (p=0.12).

The results showed that irradiation of sperms might influence the fertilization outcome possibly due to sperm DNA damage. One possible cause of precluding oocytes from fertilization in oligosperm individuals might be the formation of PCC.