Gene transfer to sperm and testis: future prospects of gene therapy for male infertility.

Male infertility has been considered a major contributory factor to infertility. The causes of spermatogenetic failure found in most cases of male infertility remain largely idiopathic. Unfortunately, there is no effective treatment to improve spermatogenesis for idiopathic male infertility patients. Intracytoplasmic sperm injection (ICSI) is the current treatment of choice for severe male infertility and has brought the joy of childbearing to couples for whom it was previously impossible; however, several problems exist with this treatment. In addition, if there are no spermatozoa in the testis of these patients, they do not have paternity potential even if ICSI is conducted. Ultimately, fertilization is better in vivo than in vitro. Recently, on the other hand, gene transfer to sperm and testis has been developed to find more effective and simple methods to obtain transgenic animals. This technique has the potential to be the most useful approach for the future treatment of male infertility. In this review, we will give an overview of the recent advanced technique of gene transfer to sperm and testis, and discuss the future prospects of gene therapy for the treatment of male infertility. In conclusion, although more investigations on the mechanism of spermatogenesis and male infertility and the establishment of techniques for more efficient and safer gene transfer to the sperm and testis will be needed, gene therapy will enable a revolutionary advance for reproductive treatment and provide great benefit for patients with male infertility in the future.