Nuclear transfer and cell transplantation: Making more with less

Abstract

Pig cloning can be achieved by transfer of nuclei of differentiated somatic cells into enucleated oocytes. Then, developing embryos are placed into surrogate mothers for further development to full term. Although cloned pigs offer the possibility of unlimited organ supply for compatible xenotransplantation in humans, the yield of a predictable number of offspring is still at an experimental phase. Spermatogonial stem cells from a fertile donor can be transplanted to the testes of infertile recipients and generate sperm. At present, results from xenogeneic spermatogenesis by transplantation indicate that porcine, bovine and equine spermatogonia find the interior of the seminiferous tubular environment not favorable for further differentiation into meiotic prophase spermatocytes. Spermatogenic cell transplantation is a promising experimental alternative for understanding the conditions required by both the donor cells and the recipient testis to coexist and even cooperate towards the full development of fertilizing sperm. (C) 2000 Wiley-Liss, Inc.