Supplementation of ex vivo mouse testes explants with PUFA-RICH lipids stimulates spermatogenesis

Abstract

Using a gas-liquid interphase culture system from neonatal mouse testes, we previously observed in ex vivo explants a relationship between the progression of spermatogenesis at both cytological and histological levels and the gene expression of some of the enzymes involved in lipid metabolism. Here, we examined by RT-qPCR the expression of two PUFA elongases (Elovl2 and Elovl4), Δ6-desaturase (Fads2), fatty acid 2- hydroxylase (Fa2h), two fatty-acid-binding proteins (Fabp3 and Fabp9) and a diacylglycerol acyltransferase (Dgat2). Testis explants from 6 days old mice cultured for 22 days evidenced progress in spermatogenesis beyond the meiotic phase in some of the tubules. Although delayed in vitro in comparison with the in vivo development, in both cases the appearance of haploid germ cells occurred concomitantly with an increase in the expression of Fabp9, Dgat2, and Fa2h. Interestingly, the genes involved in PUFA synthesis (Elovl2, Elovl4, Fads2) and transport (Fabp3) were up-regulated in the testicular explants in comparison with the in vivo situation. This suggested, as a possible cause, partial insufficiency in the culture system of the C20-C22 PUFA required as substrates by these biosynthetic enzymes. This proved to be the case, as this medium contained low proportions (less than 4%) of these fatty acids. Supplementation of ex vivo explants with a PUFA-rich total lipid extract (TL) from adult mouse testis allowed progression into meiosis at the times in culture examined. Moreover, after 22 days in culture, the TL-supplemented explants contained more tubules with spermatogenic cells that had succeeded to reach the spermatid stage. Thus, in addition to growth factors and hormones, influences that promote the biosynthesis of PUFA-containing lipids are among the factors required to optimize spermatogenesis in ex vivo tissue explants