The effects of IGF-1 on mouse spermatogenesis using an organ culture method

Currently available organ culture methods can induce the differentiation of spermatogonial stem cells (SSCs) to spermatids in vitro, but the percentages of haploid cells and elongated spermatids are extremely low. The goal of this study was to test strategies to increase the differentiation rate of SSCs into elongated spermatids in vitro. RNA-seq was performed from forty round spermatids isolated by laser capture microdissection from cultured mouse testicular fragments (MTFs) or 27 days post-partum testes. Gene Ontology (GO) and KEGG analysis of the transcriptome revealed that many cell cycle and apoptosis-associated genes were among the differently expressed genes. Quantitative real-time PCR confirmed that the expression of Ccnd3 decreased and the expression of Trp53, Casp8 and Cyct increased in round spermatids from cultured MTFs. As insulin-like growth factor (IGF-1) can regulate cell cycle and apoptosis of many kinds of cells, the expression of Igf-1 decreased in cultured MTFs and IGF-1 receptor expressed strongly in germ cells, IGF-1 was added to the basal medium. IGF-1 increased the percentages of round and elongated spermatids by decreasing the apoptosis of germ cells and increasing the density of germ cells in cultured MTFs. These results indicate that IGF-1 plays a critical role in spermatogenesis from SSCs.