Incidence of aneuploid spermatozoa from subfertile men: selected with motility versus hemizona-bound

Spermatozoa-zona pellucida binding selects for human spermatozoa with progr essive motility, normal morphology and functional competency, We postulated that this gamete interaction would also act to select against spermatozoa with chromosomal numerical aberrations. Spermatozoa from 41 men participati ng in the intracytoplasmic sperm injection (ICSI) programme were evaluated for the incidence of aneuploidy of chromosomes 18, X and Y. The hemizona as say was utilized to determine whether zona-bound spermatozoa from these pat ients have a reduced incidence of aneuploidy compared with those selected b y motility only in a standard swim-up procedure. Using multicolour fluoresc ence ill-sifts hybridization (FISH) with DNA probes specific for chromosome s 18, X and Y, the disomy rates for chromosomes 18, X, Y and XY were found to be 0.31, 0.27, 0.29 and 0.14% respectively in the swim-up motile fractio n, and 0.31, 0.33, 0.32 and 0.19% respectively in the pellet fraction. Anal ysing the zona-bound spermatozoa, the disomy rates for chromosome 18, X, Y and XY were found to be 0.02, 0.15, 0.12 and 0.07% respectively. The zona-b ound spermatozoa had a significantly lower frequency of aneuploidy than the swim-up motile fraction or the pellet fraction (P < 0.0001), The incidence of chromosome 18 aneuploidy, including both chromosome 18 disomy and nulli somy, in the swim-up motile fractions was significantly increased in patien ts with an abnormal or borderline hemizona index compared with those with a normal hemizona index (P < 0.05). We also found that a high incidence of s perm aneuploidy was associated to a certain extent with low fertilization r ate, and with failure to achieve pregnancy through ICSI. This study suggest s that the human zona pellucida has the capacity to select against aneuploi d spermatozoa by an as yet undetermined mechanism.