Pattern Recognition Receptor-initiated Ovarian Innate Antiviral Responses And Their Effects On Ovarian Functions

Background and objectives:The ovary can be infected by a wide range of viruses, which may result in ovarian dysfunction and infertility. The infection of oocytes by some viruses may lead to maternal-fetal transmission. However, the ovarian responses to viral infections remain largely unknown. This thesis focuses on pattern recognition receptor (PRR)-initiated innate antiviral responses in the ovarian cells and their effects on ovarian functions.Materials and Methods:TLR3-/- and TNF-α-/- mice and siRNA approaches were used to investigate gene function. Immunohistochemistry and Western blot were used for the determination of protein distribution and quantification. Gene expression at mRNA level was examined using real-time RT-PCR. The cytokine and estradiol levels were measured using ELISA. Poly(I:C) treatment was used to mimick viral infection.Results:PRRs that recognize viral RNA, including toll-like receptor 3 (TLR3), retinoic acid-inducible gene I (RIG-1), and melanoma differentiation-associated gene 5 (MDA5), are expressed in ovarian granulosa and stromal cells. Poly(I:C) induced innate antiviral responses in the ovarian cells, which are characterized by the upregulation of immunoregulatory cytokines, such as TNF-α, IL-6, IFN-a, and IFN-β,as well as antiviral proteins, including IFN-stimulated gene 15 (ISG15),2’-5’-oligoadenylate synthetase (OAS1), and myxovirus resistence protein 1 (MX1). Activation of NF-kB and IRF3 is required for poly(I:C)-induced ovarian innate antiviral responses. Poly(I:C) significantly reduced the estradiol level and antral follicle number and induced granulosa cell apoptosis in antral follicles. However, the ovarian functions were not affected by poly(I:C) in TLR3-/- and TNF-α-/- mice, suggesting that TLR3-mediated TNF-a production is responsible for the poly(I:C)-induced ovarian dysfunction.Conclusions:Ovarian granulosa and stromal cells are well equipped with innate antiviral machinery. The ovarian innate antiviral responses significantly reduced the estradiol levels and follicle maturation, and induced granulosa cell apoptosis, which were attributable to TLR3-mediated TNF-a production. The results provide novel insights into the mechanisms underlying the ovarian antiviral responses and their effects on ovarian...