Ovarian expression of MerTK and its ligand Pros1 in non-pregnant estrus and pregnant mice

AimThe interaction of MerTK, which negatively regulates immune responses, with its ligand Pros1 contributes to the resolution of apoptosis and inflammation, participating in the healing process of tissues. The levels of MerTK and Pros1, intensely expressed in macrophages (M phi s), are affected by sex hormones. The expression levels of these proteins in M phi s, which have a role in corpus luteum (CL) development or regression and folliculogenesis, were investigated in this study since their expressions have not been evaluated in pregnant mouse ovaries.MethodWe analyzed mouse ovaries from non-pregnant mice at estrus and gestation days 5, 8, and 15 (each n:10). We used qPCR to evaluate Mertk and Pros1 mRNA levels and assessed their protein expression and localization using immunohistochemistry and double immunofluorescence staining for co-localization.ResultsMertk and Pros1 mRNA and protein levels significantly increased in GD15. MerTK and Pros1 protein levels in mouse CL on GD15 were significantly higher than all other groups. MerTK and Pros1 positive M phi s were observed in CL of GD15 by double immunofluorescence. MerTK protein levels were increased in granulosa cells GD15 of primary and growing follicles.ConclusionOur study revealed for the first time that the expression of MerTK and Pros1 was significantly increased in CL at GD15 in mice. These results suggest that increased levels of MerTK andPros1 may enhance their interaction as receptor-ligand binding partners in CL potentially contributing to the balance of apoptosis and inflammation.

center dot Demonstrating differential expressions of MerTK and Pros1 in granulosa cells, which may contribute to MerTK and Pros1-mediated phagocytosis of apoptotic oocytes.center dot Identifying Pros1-MerTK interaction in corpus luteal macrophages may suppress inflammation, thereby maintaining corpus luteum function in pregnancy.center dot Mechanical studies are required to support our findings functionally.