In vitro development of foetal male germ cells in rats, mice and humans

摘要

The key role of the foetal germ cell line in the reproductive capacity of the adult has been known for a long time. More recently, the observed increase in male reproductive disorders such as the decline of sperm count and quality and the increased incidence of testicular cancer has been postulated to be due to alterations of foetal and neonatal testicular development in response to increasing environmental pollution. However, few tools are available to study foetal and neonatal germ cell line development and the effects of physiological or toxic substances on this process. The authors have developed an organ culture system in which foetal or neonatal testis is grown on a filter floating on a synthetic medium free of serum, hormones or biological factors. This study, using rats and mice, first compared the long-term morphological and functional development of Sertoli and germ cells in this in vivo system. In rats, these cells developed normally over a period of two weeks in vitro. Fewer cells were produced than in vivo, but a similar level of differentiated function was observed. Germ cells, which are difficult to maintain in vitro, resumed mitosis after a quiescent period, at the same time as in vivo. Similar results were obtained with mouse fetuses, but this model was less efficient. This culture model can be used to study post-natal development of the germ cell lineage in testes derived from foetuses on the last day of foetal life and invalidated for P63, that do not survive after birth. This gene was found to be involved in the regulation of germ apoptosis which resumes after birth in the mouse. Lastly, this model applied to the human species (from 6 to 12 weeks of gestation) showed that testicular architecture and germ cells can be maintained for 4 days with better efficiency at younger stages than at older stages. In conclusion, testicular architecture and intercellular communications are sufficiently preserved to sustain gametogenesis in vitro with no added factors. This method is potentially useful to study the effects of various factors, particularly xenobiotics.