Testis tissue explantation cures spermatogenic failure in c-Kit ligand mutant mice

Abstract

Male infertility is most commonly caused by spermatogenic defects or insufficiencies, the majority of which are as yet cureless. Recently, we succeeded in cultivating mouse testicular tissues for producing fertile sperm from spermatogonial stem cells. Here, we show that one of the most severe types of spermatogenic defect mutant can be treated by the culture method without any genetic manipulations. The Sl/Sl d mouse is used as a model of such male infertility. The testis of the Sl/Sl d mouse has only primitive spermatogonia as germ cells, lacking any sign of spermatogenesis owing to mutations of the c-kit ligand (KITL) gene that cause the loss of membrane-bound-type KITL from the surface of Sertoli cells. To compensate for the deficit, we cultured testis tissues of Sl/Sl d mice with a medium containing recombinant KITL and found that it induced the differentiation of spermatogonia up to the end of meiosis. We further discovered that colony stimulating factor-1 (CSF-1) enhances the effect of KITL and promotes spermatogenesis up to the production of sperm. Microinsemination of haploid cells resulted in delivery of healthy offspring. This study demonstrated that spermatogenic impairments can be treated in vitro with the supplementation of certain factors or substances that are insufficient in the original testes.

Making male gametes in culture

“…The kit ligand (KITL), a cytokine type of growth factor, is produced by Sertoli cells in the testis and must interact with the kit receptor found on differentiating spermatogonia and spermatocytes for spermatogenesis to be completed (7,8). These authors report that the addition of recombinant KITL and colony stimulating factor-1 (CSF-1) to the medium of organ cultures of testis tissue derived from mice deficient in the production of KITL induced spermatogenesis to proceed through meiosis (6). The efficiency of male gamete production in these organ cultures, and in all the earlier studies described here, is very low.…”

“…This technique was further extended when it was demonstrated that spermatogonia grown in culture in the absence of somatic cells could be transplanted into recipient testes and proceed through meiosis to form reproductively functional haploid gametes (5). Sato et al now expand their observations again by showing that their system can be used to correct spermatogenic defects in vitro (6). The kit ligand (KITL), a cytokine type of growth factor, is produced by Sertoli cells in the testis and must interact with the kit receptor found on differentiating spermatogonia and spermatocytes for spermatogenesis to be completed (7,8).…”

“…The major usefulness of this approach lies in the ability to dissect out which components of the system are necessary for gamete production and to determine what external factors can improve the efficiency of completion of meiosis. For example, although genetics has previously shown the requirement for KITL during spermatogenesis, Sato et al (6) are able to effectively ameliorate the lesion by using soluble KITL. In addition, the results with the use of CSF-1 provide new information on the potential synergistic actions of these two cytokines.…”

“…Human spermatogenic stem cells in culture could be a source of gametes from individuals with a number of infertility issues. As described by Sato et al (6), defects in endocrine or paracrine factors could be corrected, and the potential exists for transgenesis to correct any known genetic defect. Spermatogenic stem cell cultures could be used to replace stem cells destroyed by toxic agents or anticancer drugs.…”

Stem cells, in vitro gametogenesis and male fertility

“…In the case of genetic disorders, one possible treatment strategy has been proposed based on experimental evidence. Namely, Sato and coworkers succeeded in restoring spermatogenesis in Sl/Sl d mutant testes bearing mutations in genes encoding SCF by culturing with recombinant SCF (Sato et al 2012). This strategy would be particularly effective in cases in which the mutation is in a gene encoding a somatic factor and/or soluble factor, because such defects can be compensated by simply adding the recombinant protein to the medium (Fig.…”