Microglia and macrophages are increased in response toischemia-induced retinopathy in the mouse retina

[摘要] Purpose: The ability of microgilal cells (MG) and macrophages (MAC)to release cytokines, induce apoptosis, as well as perform phagocyticfunctions suggests a possible role in wound healing followingoxygen-induced injury. This study was performed to determine thetemporal and spatial expression of F4/80 (F4/80+) positivemicroglia/macrophages (MG/MAC) in areas of retinal damage in the mousemodel of oxygen-induced retinopathy.Methods: C57BL/6 postnatal day 7 (P7) mice were exposed to 75%O2 for 5 days (P12) then allowed to recover in room air.Hyperoxia-exposed (O2) mice (O2 refers to hyperoxia exposurefrom P7 to P12 only) were sacrificed on P12, P14, P17, and P21 and theireyes were examined. Localization of F4/80+ cells inFITC-dextran-perfused retinas allowed coordinate visualization ofretinal vessels and MG/MAC via fluorescence microscopy. BrdU, a cellularproliferation marker, was injected intraperitoneally 1 h prior tosacrifice. Immunostaining was performed for a microglia andmacrophage-specific antigen (F4/80) and BrdU. CCL2 (monocytechemoattractant protein-1; MCP-1) expression was examined byquantitative real time reverse transcriptase polymerase chain reaction(RT-PCR).Results: There was a marked increase (>500%) in MG/MAC inhyperoxia-exposed retinas on P17O2 and P21O2 compared tocontrol retinas. At P17O2, MG/MAC were localized in areas ofneovascularization (NV), revealing an intimate relationship betweenMG/MAC and neovascular tufts. However, P21O2 retinas demonstratedMG/MAC associated with avascular regions in the outer layers of theretina. Immunostaining for F4/80 and BrdU revealed rare co-localizationin hyperoxia-exposed retinas. Real time RT-PCR results demonstratedincreased expression of CCL2 in P14O2- and P17O2- exposedretinas.Conclusions: Our results suggest that resident retinal microgliaproliferation occurs at a low frequency in response to injury in thismodel. The substantial increase in total F4/80+ cells inhyperoxia-exposed retinas in conjunction with the upregulation of CCL2is consistent with recruitment of hematogenous macrophages into theretina. The temporal and spatial localization of MG/MAC adjacent toneovascular tufts suggests these cells are modulating the retinalresponse to ischemia-induced retinopathy.

[学科分类] 生物化学/生物物理