Abstract
Purpose :
Subretinal fibrosis causes irreversible vision loss in patients with neovascular age-related macular degeneration (nAMD). Ophthalmic imaging techniques allow detection of fibrosis with limited efficiency and there is a clinical need for novel tools to monitor fibrosis-related changes. We report in vivo imaging of active fibrosis using collagen-hybridizing peptides (CHPs), small molecules that bind to single α-chain collagen structures, allowing identification of collagen remodeling (a hallmark of active fibrosis) in the subretinal space.
Methods :
Using 2 independent mouse models (laser-induced choroidal neovascularization [CNV]; JR5558 spontaneous CNV), we investigated the effectiveness of sCy7.5-labeled CHPs to image active fibrotic lesions in vivo. Validation studies assessed correlation between CHP and epithelial mesenchymal transition (EMT) markers, laser intensity and CHP binding in vivo, and between in vivo and ex vivo CHP quantification of active collagen. The antifibrotic effects of a bispecific angiopoietin-2/vascular endothelial growth factor-A antibody (VA2) were examined in vivo by assessing CHP binding in 42-day-old JR5558 mice after 3 weekly VA2 injections versus IgG control (10 mg/kg body weight; days 21, 28, 35; sCy7.5-CHP injected on day 37).
Results :
Integration of retinal pigment epithelium (RPE)/choroid flatmount images of JR5558 eyes showed coexpression of CHPs with fibrosis and EMT-related markers, correspondence between sCy7.5-labeled and sCy3-labeled CHP binding, and increased CHP binding in RPE/choroid with age. After laser-induced scarring, sCy7.5-CHP binding in vivo correlated to the intensity of laser and ex vivo CHP (r = 0.76; P = 0.03) and fibronectin (r = 0.69; P = 0.058) binding. In laser-induced CNV, there was decreased CHP binding in vivo and ex vivo at 8 weeks (stabilized scars) versus 1 week after injury. In JR5558 mice treated with VA2, CHP integration detected significantly decreased collagen remodeling (CHP binding in vivo and ex-vivo; p < 0.01) versus IgG control.
Conclusions :
CHPs bound specifically to active fibrosis and detected increased collagen remodeling in JR5558 mouse eyes in vivo as they aged, in contrast to reduced binding over time in laser-induced scarring. The antifibrotic effects of dual Ang-2/VEGF-A inhibition were clearly demonstrated using this method, which has potential to support clinical development of nAMD treatments.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.