title: Clearance of apoptotic cells is not impaired in mouse embryos deficient in class A scavenger receptor types I and II (CD204).
abstract: Elimination of apoptotic cells is an important mechanism to maintain proper embryonal morphogenesis. The class A scavenger receptor type I, II (CD204), one of the major receptors expressed on macrophages, is a receptor actively involved in recognition and ingestion of apoptotic cells. To clarify the role of CD204 in embryonic morphogenesis, we performed immunohistochemical and immunoelectron microscopic studies using CD204-deficient mouse embryos. In control mice, almost all macrophages expressed CD204 from embryonic day 9.5 (E9.5). Phagocytes engulfing dead cells in the E13.5 interdigit region showed strong expression of CD204, indicating that CD204 was actively involved in apoptotic cell clearance. However, CD204 is not essential for the embryonic clearance of apoptotic cells, because CD204-deficient embryos developed normally without any retardation in footplate remodeling. Up-regulation of CD36 in CD204-deficient fetal macrophages suggested that CD36 substitutes for CD204 function. We also found that mesenchymal cells frequently engulfed apoptotic cells especially in early embryonal stages. These data suggest that CD204 is partially but not essentially involved in apoptotic cell clearance in embryogenesis. During early embryonal development, mesenchymal cells, rather than macrophages, play a major role in apoptotic cell clearance.
authors.affiliation: Department of Cell Pathology, Graduate School of Medical Science, Kumamoto University, Kumamoto, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Komohara
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Terasaki
authors.forename: Koichi
authors.initials: K
authors.lastname: Kaikita
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Tatsuhiko
authors.initials: T
authors.lastname: Kodama
authors.forename: Motohiro
authors.initials: M
authors.lastname: Takeya
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D017209:Apoptosis; D018955:CD36 Antigens / Q000096:biosynthesis / Q000502:physiology; D002454:Cell Differentiation; D047108:Embryonic Development; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008813:Mice, Inbred ICR; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D016253:Microscopy, Immunoelectron; D010587:Phagocytosis; D011971:Receptors, Immunologic / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D051117:Scavenger Receptors, Class A; D013997:Time Factors; D015854:Up-Regulation
chemical_list: D015703:Antigens, CD; D018955:CD36 Antigens; C495140:Msr1 protein, mouse; D011971:Receptors, Immunologic; D051117:Scavenger Receptors, Class A