Recent advances in application of male germ cell transplantation in farm animals

Abstract

Transplantation of isolated germ cells from a fertile donor male into the seminiferous tubules of infertile recipients can result in donor-derived sperm production. Therefore, this system represents a major development in the study of spermatogenesis and a unique functional assay to determine the developmental potential and relative abundance of spermatogonial stem cells in a given population of testis cells. The application of this method in farm animals has been the subject of an increasing number of studies, mostly because of its potential as an alternative strategy in producing transgenic livestock with higher efficiency and less time and capital requirement than the current methods. This paper highlights the salient recent research on germ cell transplantation in farm animals. The emphasis is placed on the current status of the technique and examination of ways to increase its efficiency through improved preparation of the recipient animals as well as isolation, purification, preservation, and transgenesis of the donor germ cells.

Figure 1

A schematic representation of procedures involved in germ cell transplantation in farm animals. A single-cell suspension of germ cells is prepared after enzymatic digestion of the donor testis for transplantation into recipient testes. Alternatively, the number of spermatogonial stem cells (SSCs) can be enriched in the donor cells and the resultant cells can be used fresh or preserved (for short term through hypothermic preservation or long-term by cryopreservation) and/or transfected with genes of interest before transplantation. The recipient animal can be treated with busulfan or undergo local irradiation of the testes to reduce the number of endogenous SSCs, in preparation for germ cell transplantation. Transplanted SSCs can form colonies of donor-derived spermatogenesis and produce sperm to allow the recipient to sire progeny carrying the donor haplotype.