Abstract
Purpose :
Acute injury to the retina or choroid can mobilize hematopoietic cells to the sites of injury and vascular repair can be performed by a BM population termed myeloid angiogenic cells (MACs). Hematopoietic cells are derived from the bone marrow (BM) present in both long and flat bones such as the tibia and calvarium, respectively. However, whether this injury-induced mobilization of hematopoietic cells to the damaged eye occurs specifically from one BM source or the other is not known. In this study, we investigated the differential contribution of tibial (long bone) and calvarial (flat bone) BM cells to the areas of injury using the mouse model of choroidal neovascularization (CNV).
Methods :
BM-derived hematopoietic cells were isolated from the calvarium of adult Rosa-mTmG mice and from the tibia of adult C57BL/6-EGFP mice to obtain td tomato-fluorescent (td+) calvarial cells and green-fluorescent (gfp+) tibial cells, respectively. The BM cells were enriched for hematopoietic stem and progenitor cells using EasySep Mouse Hematopoietic Progenitor Cell Isolation Kit (Stemcell Technologies). Adoptive transfer of cells (1x105) was performed in C57BL/6J wild type. Recipient mice were then subjected to laser photocoagulation in one eye to induce CNV. Uninjured eyes were used as control. Mice were euthanized 24 hours post-injury and their rpe/choroids were harvested for flow cytometry.
Results :
CNV resulted in a significant increase in total CD45+ hematopoietic cells in the choroid compared to untreated eyes (0.7% vs. 0.43%, p=0.0143). We observed that the injured choroid recruited more gfp+ (tibial) monocytes compared to td+ (calvarial) monocytes (0.36% vs. 0.039%, p=0.0022). However, there were more td+ neutrophils (0.867% vs 0.1179%, p=0.029) compared to gfp+ neutrophils in the injured choroid. The injured choroid recruited more td+ MACs compared to gfp+ MACs (0.80% vs. 0.01310%, p=0.0022). There was no significant difference in the contribution of tibial or calvarial cells to macrophages 24 hours after CNV injury.
Conclusions :
Our study supports dynamic recruitment of hematopoietic cells into the rpe/choroid during acute injury. Our data suggests that mobilization of cells from the hematopoietic system into the injured rpe/choroid is not homogenous. Calvarial marrow cells may provide the optimal source of cells for generating vascular reparative cells in vivo.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.