Resident autofluorescent perivascular macrophages have a scavenger function and may contribute to the maintenance of the blood‐retinal barrier

Abstract

Abstract Purpose The retina contains two distinct populations of monocyte‐derived cells: perivascular macrophages and microglia. In this work we describe the presence in mouse and human healthy retinas of a new subtype of perivascular resident macrophages, present in the perivascular space and different from microglia. Methods CD1 mice and human retinas were used. Perivascular macrophages were characterized by means of confocal microscopy, electron microscopy, and flow cytometry analyses. Two murine models of blood‐retinal barrier breakdown and photoreceptor degeneration were also used. Results These perivascular cells emitted specific autofluorescence and constitutively expressed the scavenger receptor class A. They were seen to move in an oscillatory manner along blood vessels, providing an additional coating to thinner areas of the vascular wall. These macrophages also accumulated blood‐borne horseradish peroxidase and acetylated low‐density lipoprotein without blood‐retinal barrier pathological disruption. Furthermore, they were early detected at lesions during photoreceptor degeneration. Conclusion Taken together these findings suggest that these perivascular cells fulfil a major role in the scavenging of blood‐borne molecules contributing to blood‐retinal barrier function, and may have a possible role in the onset and development of retinopathy. All these features are consistent with those described for brain Mato cells. Thus, this study reveals the presence of autofluorescent perivascular Mato cells in the retina.