[Present research on the male germ cell differentiation in vitro]

Several culture systems such as tissue and organ culture system, seminiferous tubules culture system, co-culture systems of Sertoli cells and germ cells for male germ cell differentiation studies in vitro have been established. The importance of the blood-testis barrier and the polarity of testicular cells have been emphasized recently. And then the bicameral chambers culture system that can mimic the compartmental structure of testes and the calcium algmate culture system that can provide three-dimensional support have been primarily set up. These culture systems are powerful tools for facilitating the understanding to the spermatogenesis. The entire meiotic part of spermatogenesis in some animals has been achieved in vitro by different laboratories, but little is known about the regulation mechanism of the meiotic step of spermatogenesis in detail. This review focuses on the present studies on the differentiation of male germ cells, especially the meiotic step of the differentiation.