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Origin of macrophage in photocoagulated rabbit retina
Abstract:
To identify the hematogenous origin of macrophages in the photocoagulated retina, a technique of labeling blood monocytes with colloidal carbon prior to the coagulation was used. Colloidal carbon was given intravenously to adult pigmented rabbits twice daily for 5 days, and 3 days after the last injection xenon flash photocoagulation was performed on the retina. The circulating blood cells and the coagulated portions of the retina and choroid were then examined using electron microscopy. At the time of photocoagulation, circulating blood monocytes contained several clusters of carbon granules in the cytoplasm. Two days after coagulation, monocytes with carbon granules were observed to penetrate the Bruch's membrane. In the coagulated retina, macrophages with carbon granules were observed, while retinal pigment epithelial cells contained no carbon granules. Two months after coagulation, macrophages with carbon granules remained in the retina, and a few proliferated pigment epithelial cells contained carbon granules in the cytoplasm. These carbon granules were considered to be derived from degenerated macrophages. These results indicate that hematogenous monocytes invade the retina from the choroid through the Bruch's membrane and are transformed into macrophages, some of which degenerate in the retina and are phagocytized by pigment epithelial cells.
Insights
Hematogenous monocytes invade the retina after photocoagulation, becoming macrophages. These macrophages, identified by carbon labeling, migrate through Bruch
Area of Science:
- Ophthalmology
- Immunology
- Cell Biology
Background:
- The origin of retinal macrophages in injury models is debated.
- Understanding macrophage origins is crucial for retinal disease research.
Purpose of the Study:
- To determine if circulating monocytes are the source of retinal macrophages following photocoagulation.
- To trace the migration pathway of these cells.
Main Methods:
- Adult pigmented rabbits received intravenous colloidal carbon injections to label monocytes.
- Xenon flash photocoagulation was performed on the retina.
- Electron microscopy was used to examine blood cells, retina, and choroid.
Main Results:
- Carbon-labeled monocytes were observed migrating through Bruch's membrane into the retina.
- Macrophages containing carbon granules were present in the retina post-photocoagulation.
- Pigment epithelial cells later contained carbon granules, suggesting phagocytosis of degenerated macrophages.
Conclusions:
- Hematogenous monocytes infiltrate the retina from the choroid via Bruch's membrane.
- These monocytes differentiate into macrophages within the retina.
- Macrophage degeneration and subsequent phagocytosis by retinal pigment epithelial cells occur.