Abstract
Purpose :
We hypothesize that EndMT contributes to fibrosis during CNV pathogenesis. The goal of this study was to determine the therapeutic potential of a small molecule inhibitor of EndMT and fibrosis for CNV in an established mouse model of spontaneous CNV (sCNV).
Methods :
The JR5558 sCNV mouse, male and female, and age-matched wild-type mouse (C57BL/6J) were used in this study. To assess the therapeutic efficacy of a small molecule inhibitor of EndMT and fibrosis, 5 nmoles of SB203580 (SB) a P38MAPK inhibitor or DMSO control was intravitreally injected into 24-day-old JR5558 mice alone or in combination with an anti-VEGFR2 neutralizing antibody (5 μg) or DMSO. After seven days the number, size of the CNV lesions and levels of EndMT-fibrosis were quantified by IHC using FITC-conjugated isolectin B4 together with anti-vimentin staining, respectively. For in vitro cell assay experiments, primary human retinal endothelial cells (hREC) were treated for 6 days with a mixture of cytokines to induce an EndMT phenotype, which was confirmed by gene expression and ICC of both endothelial and EndMT markers (CD31, VE-cadherin, VEGFR2, a-SMA, FSP1 and vimentin).
Results :
Intravitreal injection of SB reduced CNV growth (70.3 % ± 10.4 SEM; n=10; p<0.05) compared to DMSO (100 % ± 10.2 SEM; n=13). However, the number of CNV lesions per eye did not change in treated (26.2 ± 3.3 SEM) versus DMSO (27.2 ± 2.2 SEM). The SB treatment decreased the vimentin levels in the sCNV lesions (76.5 % ± 7.5 SEM; n=9; p<0.05) versus DMSO (100 % ± 8.1 SEM; n=12). Contrary, intravitreal injection of an anti-VEGFR2 antibody increased the vimentin levels (196.9 % ± 5.1 SEM; n=6; p<0.007) compared to DMSO, while the combination of SB and anti-VEGFR2 was able to abolish this increase (90.21 % ± 8.4 SEM; n=6; p<0.05). In vitro experiments demonstrate that EndMT cells responded less to VEGF stimulation assessed by gene expression (VCAM-1 0.61 ± 0.04; E-selectin 1.6 ± 0.07; Tissue factor (TF) 2.62 ± 2.1; p<0.01 n=3) compared to hREC (VCAM-1 20.34 ± 1.0 SEM; E-selectin 9.27 ± 0.6 SEM; TF 19.04 ± 2.5 SEM n=3), while a p38MAPK inhibitor restored the VEGF responsiveness by EndMT cells (VCAM-1 2.12 ± 0.3 SEM; E-selectin 9.45 ± 0.8 SEM; TF 23.5 ± 4.1 SEM; p<0.05 n=3).
Conclusions :
Our results suggest that EndMT-mediated fibrosis could be an effective therapeutic target to reduce CNV in AMD.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.