Expression And Function Of Toll-like Receptor3in Mouse Spermatogenic Cells

Background and objectives:Although the testis is a remarkable immunoprivileged tissue, invading microbial pathogens can be effectively eliminated. Attentions have been paid to the defense function of testicular cell-mediated innate immunity. The mechanisms underlying testicular innate immune responses remain to be clarified. A growing body of evidence shows that Toll-like receptors (TLRs) initiate innate immune responses in testicular somatic cells. However, expression and function of TLRs in male germ cells have not been investigated. In this thesis, we studied the expression and function of TLR3in spermatogenic cells.Materials and Methods:Spermatogenic cells were isolated from5-week-old C57BL/6J mice. Cell purity was assessed by analysis of of marker gene expression (Kit for spermatogonia, Scp2for spermatocytes, and Prm2for spermatids). TLR3mRNA and protein levels were detected in the germ cells by real-time RT-PCR, immunohistochemistry and Western blotting. Cytokine production was determined using ELISA. Apoptosis of spermatogenic cells was analyzed by AO/EB incorporation, TUNEL staining and flow cytometry.Results:Spermatogonia and spermatocytes constitutively express TLR3. TLR3activation in the spermatogenic cells triggers antiviral responses. Poly(I:C) induces expression of various inflammatory cytokines including IL-1β, IL-6and TNF-a through NF-κB activation, as well as type1interferons (IFN-a and IFN-β) via IRF3activation. Moreover, TLR3activation induces apotosis of the spermatogenic cells through upregulating TNF-α. Experiment in vitro demonstrate low concentration TNF-a can inhibit apoptosis of the germ cell, high concentration TNF-a can promote apoptosis of the germ cell. Conclusions:We demonstrate that TLR3activation in spermatogenic cells triggers innate immune responses against viruses, and induces apoptosis of the germ cells. The results provide novel insights into the mechanisms underlying spermatogenic cell-mediated testicular innate immunity, and virus-induced impairment of spermatogenesis.