The Institute of Advanced Medical Technology, 3154, Yakushiji, Minami-Kawachi, Kawachi, Tochigi, 329-0431, Japan
Dear Sir,
Recently, we were amazed to find an article (Ding et al., 1999) which stated that zona-free blastocysts could be saved with intracytoplasmic sperm injection (ICSI). Just a week previous to reading their paper we performed a similar procedure with the same results. Most interesting is the similarity in our pictures (Figures 1 and 2
).
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On day 3, the embryo underwent a compaction process and formed a compact morula (Figure 1). By day 5, it had developed almost to something resembling a hatching blastocyst (Figure 2
).
We believe that zona-free human oocytes can be successfully fertilized by ICSI and that fertilized zona-free human oocytes can undergo normal cleavage, compaction, blastocyst formation and a process similar to hatching in vitro. In conclusion, we feel that in cases where it is difficult to obtain quality oocytes, ICSI can be used even if the zona is not intact.
Notes
1 To whom correspondence should be addressed
References
Ding, J., Rana, N. and Dmowski W.P. (1999) Intracytoplasmic sperm injection into zona-free human oocytes results in normal fertilization and blastocyst development. Hum. Reprod., 14, 476478.