The development in vitro of the mammalian gonad. Ovary and ovogenesis

Abstract

Several investigators have tried to cultivate in vitro the mammalian and avian gonad, usually with the object of obtaining the growth and differentiation of the germ cells under in vitro conditions. The results so far obtained, however, have been disappointing. Champy (1920) is the only author, so far as we know, who has definitely claimed to observe some differentiation of the germ cells in vitro . He states that in testicular explants from the mature rabbit he observed the transformation of spermatogonia into spermatocytes, but the process did not advance beyond the leptotene phase of meiosis. Champy’s findings, however, have not been confirmed by other investigators, probably owing to the difficulty of cultivating mature testicular tissue. In birds, progressive differentiation of the germ cells in vitro has not been recorded. Cultures of ovarian and testicular tissue of the embryonic fowl have been studied by Fano and Garofolini (1927 and 1928). The explants formed an epithelial outgrowth which was soon replaced by what appeared to be fibroblasts. Dantchakoff (1932) cultivated the undifferentiated gonad of 3½-day fowl embryos and described three types of cells in her cultures: ( a ) large amoeboid cells—Waldeyer’s “Ureier” or “Urkeimzellen”—which in vitro developed pseudopodia and showed active amoeboid movement, ( b ) connective tissue strands, ( c ) epithelium ­ like tissue. Wermel (1933) made cultures of the undifferentiated gonad and of embryonic and adult testes and observed growth of both the somatic and germinal tissue. Muratori (1935 and 1937) cultivated gonad tissue from embryonic and newly hatched fowls, but although he describes the nuclear pattern of the germ cells emigrating from the explants, he makes no mention of any differentiation occurring in the explanted gonocytes. Several workers have grown mammalian gonad tissue in vitro .