Sex Chromosome Ratios and Aneuploidy Rates in the Zona Pellucida Selected Spermatozoa From Normal and Subfertile Men
The human hemizona has been demonstrated to select spermatozoa with good motility, normal morphology, and the capacity to undergo the zona-induced acrosomal reaction. The studies conducted here are directed at using the human hemizona to investigate two key questions: (1) whether human X-chromosome bearing spermatozoa (X-sperm) and Y-chromosome bearing spermatozoa (Y-sperm) differ in their functional survival time (assessed by their capacity to bind to the human zona pellucida) after prolonged in vitro incubation, and (2) whether hemizona-bound spermatozoa have a reduced aneuploidy rate compared to unbound (and therefore, unselected) spermatozoa? In the functional survival study, donor spermatozoa were held in vitro for up to 72 hours using two systems: at 4°C refrigeration and at 37° incubation. At each 24 hour storage interval, spermatozoa were coincubated with human hemizona, and the total numbers of zona-bound X-sperm and Y-sperm were determined using fluorescence in situ hybridization. The analysis revealed that although equal proportions of X-sperm and Y-sperm survived functionally throughout the 72 hours at 4°C refrigeration, the proportions differed after 48 hours incubation when the storage took place at 37°C, with significantly more Y-sperm surviving functionally than X-sperm. Spermatozoa from subfertile patients were used in the aneuploidy study. This study demonstrated that zona-bound spermatozoa had a significantly lower chromosomal aneuploidy rate compared to unbound spermatozoa. This indicates that hemizona has the potential to be used clinically to improve the genetic quality of zygotes fertilized using intracytoplasmic sperm injection.
Sex chromosome ratios, Aneuploidy rates, Zona pellucida, Spermatozoa, Genetics, Molecular Biology
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