Expression Patterns And Functions Of Toll-like Receptors In Mouse Sertoli Cells

TLRs(Toll-like receptors) are "pattern-recognition receptors" that recognize conserved,pathogen-code molecular structures.To date,10 distinct TLRs have now been identified in humans and 12 in mice.TLRs play crucial roles in mediating innate and adaptive immunity.Sertoli cells create a microenvironment that protects seminiferous tubules from autoantigens and invading pathogens.Here,we examined the expressions and functions of TLRs in mouse Sertoli cells.RT-PCR,Western bloting and flow cytometry were used to analyze gene expression.Immunofluorescence staining was used to determine activation of NF-κB.The phagocytosis assay was performed by ORO staining for lipid droplets.We demonstrated that TLR2,TLR3,TLR4 and TLR5 are highly expressed,TLR6, TLR7 and TLR13 are expressed at relatively low level,and TLR1,TLR8,TLR9,TLR11, TLR12 are not detected in mouse Sertoli cells.We focused our study on the roles of TLR2-TLR5 in Sertoli cells.Our data indicated that the TLR2-TLR5 can be activated by their ligands in mouse Sertoli cells and subsequently increase expression of the inflammatory cytokines IL-1α,IL-6,IFNαand IFNβ.Activation of TLR2-TLR5 can up-regulate inflammatory cytokines IL-1αand IL-6,and TLR3 and TLR4 induce the expression of typeⅠIFNs(IFNαand IFNβ).Notably,activation of TLR3 by its ligand,poly (I:C),specifically promoted phagocytosis of apoptotic spermatogenic cells by Sertoli cells. The TLR-induced Sertoli cell phagocytosis was found to be associated with the up-regulation of scavenger receptors.The results suggest that TLRs expressed in mouse Sertoli cells may play roles in defense against invasion of allo- and auto-antigens in the seminiferous tubules,and thus maintain testis as an immune privilege site.Secondly,we investigated the relationship of vaginal development and Tyro3 RTKs. Vaginal atresia is a congenital abnormality of the female genitourinary system,and the specific molecular mechanism leading to failure of vaginal development remains to be elucidated.Here,we report that the female mice lacking Tyro3 RTK subfamily(Tyro3, Axl and Mer) exhibit a high incidence of distal vaginal atresia.The ratios of the vaginal atresia in Tyro3 RTKs mutant female mice are as follows:2.5%for Mer^-/- mice,4.0%for Axl^-/-Mer^-/-,3.7%for Tyro3^-/-Mer^-/-,16.06%for Tyro^-/-Axl^-/-Mer^-/- mice.We did not find the vaginal atresia in Axl^-/-,Tyro3^-/-,Axl^-/- Tyro^-/- and wild-type mice.These observations suggest that Tyro3 RTKs play roles collaboratively in vaginal development,and Mer is more critical,Axl and Tyro3 support the function of Mer.Tyro3 RTKs mutant mouse could be a useful model to study the mechanism of vaginal atresia formation.