Studies on Regeneration of Heterotopic

Fragments of spleen autotransplanted to subcutaneous tissue of the abdomen In the rat undergo almost complete necrosis and then regenerate into splenic tissue with a microscopic structure Indistinguishable from the structure of the original organ. The regenerative process reminiscent of the spleen’s embryogenesis, originates from a shell of surviving splenic tissue at the surface of the implant. The regenerative zone first consists of almost monotonous connective tissue cells interspersed with red blood cells; It develops Into splenic red pulp consisting of sinuses and intersinal cords. As capillaries develop, the structure of small arteries and penarterial lymphatic sheaths appear, and soon the structure of splenic white pulp becomes evident. Some 5 wk after autotransplantation, the splenic reconstruction is complete. The weight of the recovered tissue is a linear function of the weight of the implanted tissue; yet the linearity is lost when the weight of the implanted tissue exceeds 100 mg.