Cytogenetic analysis of in vivo and in vitro matured oocytes derived from naturally cycling and stimulated mice

The objective of the study was to analyze the potential role of follicle stimulating hormone (FSH) in cytogenetic changes of in vivo and in vitro matured mouse oocytes and to determine whether the lower developmental potential of immature oocytes is due to a higher incidence of abnormalities in meiotic spindle organization and chromosome alignment as well as aneuploidy. In vivo matured oocytes were collected from naturally ovulated and superovulated (5.0 I U of recombinant follicle-stimulating hormone [rec-FSH] + recombinant human chorionic gonadotropin [rec-HCG]) mice. Immature oocytes were retrieved from naturally cycling mice and from mice primed with rec-FSH for 48 h. The immature oocytes were cultured 18 h for in vitro maturation (IVM). In vivo and in vitro matured oocytes were assessed for the meiotic spindle organization and chromosome alignment as well as aneuploidy. There was no significant difference of meiotic spindle organization, chromosomal alignment and aneuploidy between in vivo and in vitro matured oocytes derived from naturally cycling and stimulated mice. Therefore, the lower developmental potential of immature oocytes does not appear to be directly related to the incidence of abnormal meiotic spindle organization and chromosome alignment or to aneuploidy.