Differentiation of Gonad Primordia in Kidney of Adult Rat

Transplantation of mammalian embryonic tissues to an adult environment has been more or less successful in the hands of several workers. Sites within the abdomen of the rat have not proven very successful as reported by Nicholas. 1 Nicholas has, however, obtained differentiation in 80% of grafts of 8 and 9 day rat embryos transplanted to the adult mammary gland. In the rabbit, Waterman 2 has demonstrated that the omentum of an adult animal serves as a suitable site for the differentiation of embryonic primordia.

In the present work various abdominal sites were tried with poor success. The kidney, however, as a site for the transplantation of embryonic primordia offers a number of advantages. Growth is unrestricted, the capsule interfering little with the graft, which is clearly visible and sharply differentiated from the host tissue. Rapid vascularization insures ready incorporation of the transplanted tissue. These advantages are demonstrated by the transplantation, in a subcapsular position, of a series of grafts of posterior halves of 11 day rat embryos, or the mesonephroi and gonad primordia of 12, 13 and 14 day embryos (sex is not morphologically differentiated until the fourteenth day), for periods of 7 to 28 days. In one series of 116 grafts, 80% of the grafts have become established. The number of grafts differentiating in a second series of transplantations of 64 cases has been 100%. Fourteen to 21 days is the period of optimum differentiation.

From posterior halves of 11 day embryos skin, nervous tissue, connective tissue, cartilage, bone, smooth and striated muscle, metanephros, gonad, adrenals and gut differentiate. When the mesonephroi and gonad primordia are transplanted alone there is subsequent development of metanephros and sexually differentiated gonad.