Microglia guide stepwise retinal vascular sprouting and remodeling in postnatal CX3CR1-GFP mice: a spatiotemporal observation from P1 to P30

Introduction Retinal vessel formation is a complex process that may be affected by multiple etiological factors. This study aimed to investigate the formation of retinal vessels in CX3CR1 gfp/gfp mice after birth. Methods CX3CR1 gfp/gfp transgenic mice were subjected to retinal vascular examination at eight different time points during development. The differentiation of arteries and veins, branching of vessels, and vessel length were thoroughly examined. The potential correlation between developmental vessels and microglia were examined during the developmental process. Results We found that retinal vessels developed from the center of the optic papilla and radiated to the peripheral retina. Vascular remodeling began at P7. Subsequently, at P14, the vascular network consolidated with a honeycomb-like architecture. The length of the large vessels increased gradually from P14 until a complete vascular network was formed at P17. The number of primary branches increased from P17 and then decreased until P30. The density of microglia in the central retina was higher than at the edge retina between P1 and P30. We found that microglia appeared at the edge of the retina and preferred vessel formation at P1. Retinal microglia are involved in retinal vessel formation and development. Discussion These findings may serve as a reference database for therapeutic trials on retinal vascular diseases.