Preservation of chromosomal integrity in murine spermatozoa derived from gonocytes and spermatogonial stem cells surviving prenatal and postnatal exposure to γ‐rays in mice

Abstract

Prenatal and postnatal male mice were acutely (659−690 mGy/min) and continuously (0.303 mGy/min) exposed to 2 Gy γ-rays to evaluate spermatogenetic potential and chromosome damage in germ cells at adulthood. Acute irradiation on days 15.5, 16.5, and 17.5 post-coitus (pc) affected testicular development as the result of massive quiescent gonocyte loss. In these testes, the majority of the seminiferous tubules were devoid of germ cells. Acute irradiation on days 18.5 and 19.5 pc had less effect on testicular development and spermatogenesis, even though germ cells on these days were quiescent gonocytes. Adverse effects on testicular development and spermatogenesis were observed following continuous irradiation between 14.5 and 19.5 days pc. Upon exposure to acute and continuous postnatal irradiation after the differentiation of spermatogonial stem cells and spermatogonia, nearly all of the seminiferous tubules were engaged in spermatogenesis. Neither acute nor continuous irradiation directed at quiescent gonocytes was responsible for the increased number of multivalent chromosomes in descendent primary spermatocytes. In contrast, a significant increase in cells with multivalent chromosomes was observed following acute irradiation on days 4 and 11 post-partum (pp). However, there were no significant increases in unstable structural chromosomal aberrations and aneuploidy in spermatozoa, regardless of cell stage at irradiation or the radiation dose-rate. Thus, germ cells surviving prenatal and postnatal irradiation can restore spermatogenesis and produce viable spermatozoa without chromosome damage. These findings may provide a better understanding of reproductive potential following accidental, environmental, or therapeutic irradiation during the prenatal and postnatal periods in humans.