Reproduction Abstracts

Introduction: The aims of this study were to show the existence of individual differences in the spatial distribution patterns of sperm acrosome-associated 1 protein (SPACA1) in human ejaculated sperms and to reveal a correlation between distribution pattern of SPACA1 and outcome of conventional IVF.

Materials and methods: Informed consent was obtained from all the participants for this study. Viable sperms obtained by swim-up method were selected morphologically and incubated to induce capacitation. Then the sperm suspension was introduced into the medium containing eggs. Fertilization was confirmed by the observation of two pronuclei at 19 h after co-incubation with sperms. The surplus sperms were used to detect SPACA1 by indirect immunofluorescence and the distribution patterns were classified. The association between distribution patterns of SPACA1 and fertilization rate or blastocyst development rate in IVF was examined.

Results and discussion: SPACA1 was localized definitely in the equatorial segment, but variedly in the acrosomal principal segment. The distribution patterns of SPACA1 in the acrosomal principal segment could be classified into three categories: i) strong, ii) intermediate or faint, and iii) almost no immunofluorescence. There were large differences in terms of the composition of the classified sperms among patients. Although fertilization rates were not influenced by the differences, the rates of blastocyst formation and high quality blastocyst formation were significantly associated with the rate of class-A sperms. These results suggest that SPACA1 of the acrosomal principal segment may be involved in early embryonic development in vitro.