Abstract
Purpose :
We have previously shown that in the Nuc1 (a spontaneous mutation in the Cryba1 gene that encodes for βA3/A1-crystallin) rat retina there is a significant increase in the number of macrophages. By 18 months of age the Nuc1 retina is detached with clear evidence of subretinal fluid, epiretinal fibrosis and preretinal vasculature, not observed in the retina of wild type (WT) rats. This study was undertaken to identify factors and pathways contributing to the survival of the increased number of macrophages in Nuc1 retina.
Methods :
Extracts prepared from retinas of WT and Nuc1 rats at 8 days, 21 days, 9 weeks and 9 months of age were used for microarray analysis. Quantitative real time-PCR was used to confirm target gene expression. Infiltrating macrophage and macrophage-like cells were identified by immunohistochemistry using antibodies to ED1, ED2 and CD11b/18 (OX-42). To determine the signaling pathway involved in the increased survival of macrophages, western blotting was performed with antibodies to IGF-II (cloneS1F2), p44/42 MAPK (Erk1/2) and phospho-p44/42 MAPK (Erk1/2) (Thr202/Tyr204).
Results :
Microarray analysis showed an age-dependent increase in the expression of properdin, secreted Phosphoprotein 1 and CSF-1R in retinas from Nuc1 rats relative to WT. QPCR results indicated that while expression of properdin increased most significantly at 9 months, the level of CSF-1R increased significantly as early as 21 days and increased exponentially with age. The spike in expression of CSF-1R was associated with increased macrophage population in the Nuc1 retina. Moreover, our western data suggested that the survival of the macrophages is regulated by the pro-IGF-II/MAPK/ERK1/2 pathway.
Conclusions :
CSF-1 is the most pleiotropic macrophage growth factor and binding to the receptor triggers key signaling pathways, such as MAPK pathway. The MAP kinases ERK1/2 are key elements for signal integration downstream of CSF-1R, and their sustained activation leads to macrophage differentiation and survival. Therefore, inhibitors of CSF-1R may offer an attractive strategy for reducing macrophage numbers in inflammatory diseases of the retina.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.