Composition of Somatic and Germ Cells of Human Gonads in Prenatal and Postnatal Periods

Аннотация

For comparative analysis of the chronology and dynamics of development and differentiation of germ cells in human gonads in antenatal and postnatal periods, we analyzed the composition of somatic cells as well as the amount, morphology, and characteristics of the state of nuclear chromatin on the basis of the ratio of mitotic stages and prophase I of meiosis in oocytes and spermatocytes. Until week 6 of antenatal development, human gonads are classified into the indifferent type; the proportion of germ cells (GCs) in the sum of somatic and germ cells in them ranged from 9.21 to 33.29%. In the analysis of histological preparations, gonads of female fetuses on week 8–9 of antenatal development were significantly differentiated as ovaries. The formation of the pool of female germ cells is ensured by the proliferation of oogonia (1.96–10.34% of mitoses) in embryogenesis and by degeneration of their nuclei. In developing testes, among the nuclei of male germ cells of antenatal and neonatal gonads, nuclei at the leptotene stage of prophase I of meiosis and at subsequent stages were not detected. In the gonads of male fetuses on weeks 6–11 of antenatal development, mitotic and degenerating germ cells and germ cells at the preleptotene stage of chromosome condensation were detected, whereas no mitotic germ cells were identified in the histological preparations of testes of male newborns and infants. An important distinction between the chronology of differentiation of gametes and chromatin transformation dynamics in the nuclei of male and female germ cells is the lack of the chromatin decondensation phase (prochromosomes) at the preleptotene stage in prophase I of meiosis in the male germ cells.