The correlation between chromosome aberrations and head morphology or motility of human spermatozoa : Analysis by using intracytoplasmic sperm injection into mouse oocytes

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(1) A highly successful method for human sperm chromosome analysis was established by using intracytoplasmic sperm injection (ICSI) into mouse oocytes. Namely, 7O.7% of sperm-injected oocytes were able to reach the first cleavage metaphase, and 94.6% of metaphasic ova were successfully karyotyped.(2) In vitro aging of mouse oocytes and human spermatozoa, which takes place when they are waited for ICSI in the culture medium, may be associated with the incidence of sperm chromosome aberrations. However, no change was found in the aberration frequency even when both gametes were aged in vitro for about 3 hours.(3) In motile human spermatozoa with normal morphology, the incidences of aneuploidy and structural chromosome aberrations were 1.7% and 8.8% respectively. These incidences were not statistically different between fresh and frozen-thawed spermatozoa, indicating that cryopreservation of spermatozoa in liquid nitrogen has no deleterious effect on sperm chromosomes.(4) No increase of the chromosome aberrations was found in the spermatozoa with a large head, a small head, and a pointed head, as compared with the aberration frequency in morphologically normal spermatozoa. In contrast, the frequency was significantly higher in the spermatozoa with an elongated head.(5) The incidence of structural chromosome aberrations in immotile spermatozoa with normal morphology was similar to that in motile spermatozoa when immotile spermatozoa were kept in seminal fluid until ICSI.On the contrary, aberration frequency increased significantly when immotile spermatozoa were stored in the culture media (BWW, HTF) for 2 hours or more. An increasing tendency was found in PBS-stored spermatozoa. Aberration frequency was also heightened by centrifugation of spermatozoa.