283. Regulated expression of the c-fms receptor characterises distinct ovarian macrophage populations

Abstract

Macrophages represent a major immune cell type in reproductive tissues and are thought to regulate multiple aspects of reproduction, including ovarian function. We have previously shown a distinctive phenotype of ovarian thecal macrophages present around the preovulatory follicle, such that secreted cytokines are uniquely regulated within these cells across the oestrus cycle. C-fms is a macrophage-specific gene that encodes the receptor for colony-stimulating factor-1 (CSF-1), and that regulates macrophage proliferation, differentiation and migration, as well as pro-inflammatory responses.1,2 We acquired transgenic mice (from DA Hume, Institute for Molecular Bioscience, University of Queensland) that express green fluorescent protein (GFP) exclusively in macrophages under direction of the c-fms gene promoter.3 In ovaries from these animals we have previously reported that macrophages constitutively positive for macrophage markers, F4/80 and MHCII, exhibited spatially regulated expression of GFP (c-fms); being GFP+ within the stroma surrounding small follicles, particularly atretic follicles, but GFP– in theca surrounding preovulatory follicles and healthy corpora lutea (CL), further reinforcing the concept that these macrophages are not classically activated but have a unique resident phenotype. Further examination of the GFP+ ovarian macrophage population has revealed that the highest levels of GFP expression were in macrophages associated with TUNEL+ regressing CL and, even though CSF-1 typically induces proliferation, the GFP+ macrophages within the regressing CL did not incorporate BrdU label nor express cyclin D1. This indicates that in the murine ovary c-fms expression may not regulate ovarian macrophage proliferation or migration but more likely represents a subset of classically activated ovarian macrophages that are actively differentiating or phagocytically active. (1)Fixe P and Praloran V (1998) Cytokine 10, 32–37.(2)Pixley FJ and Stanley ER (2004) Trends in Cell Biology 14, 628–38.(3)Sasmono RT et al. (2003) Blood 101, 1155–63.