Abstract
Purpose: :
Hematopoietic stem cells (HSCs) have a natural ability to home to areas of injury for regeneration. The integrity of retinal pigment epithelium (RPE) is important for the maintenance of a healthy retina. This study investigated the recruitment and distribution of HSCs in the retina in a laser-induced RPE injury model with the specific aim of delivering a sub-lethal injury to the RPE and avoiding rupture of Bruch’s membrane.
Methods: :
Chimeric mice were generated by injection of sca-1+, c-kit+ HSCs from green fluorescent protein (gfp) transgenic mice into lethally irradiated wild-type C57BL/6J recipients. The gfp chimeric mice were subjected to a low-intensity laser injury (532-nm diode, 100 milliwatts for 0.1 second) targeted on the RPE layer and then sacrificed at 1, 4, 12, 24 and 48 hours post laser. Their eyes were enucleated, fixed in 4% paraformaldehyde and embedded in paraffin wax for immunohistochemical analysis of gfp expression to determine if there was any recruitment of HSCs to the retina following the sub-lethal RPE injury.
Results: :
Intense staining of gfp was seen in the retinal ganglion cell layer as early as 1 hour after injury. gfp fluorescence was detected in parts of the inner nuclear layer and outer plexiform layer throughout different time points. However, higher intensity of gfp was found in the RPE and choroid of mice sacrificed at later time points (24 and 48 hours) post laser injury.
Conclusions: :
This study provides evidence of the potential of bone marrow-derived HSCs to rescue a compromised RPE layer in a time-dependent manner. Immunohistochemical studies of the immune and inflammatory responses are currently underway.
Keywords: wound healing • retina • laser