Abstract
Purpose :
Human genetics studies have identified risk loci and genetic variants associated with age-related macular degeneration (AMD), including several extracellular matrix related genes such as MMP9, TIMP3 and COL8A1. Collagen type VIII alpha 1 (COL8A1) and alpha 2 (COL8A2) are short-chain collagens expressed in many organs. While the COL8A1 gene has been genetically linked to AMD, the mechanism by which COL8A1 is potentially involved in the disease remains unknown. Here we examined the COL8A1 expression in human eyes, and investigated its function in AMD animal models.
Methods :
COL8A1 and COL8A2 expression in control and AMD human eyes was examined by in situ hybridization. Col8a1 knockout (KO) and Col8a2 KO mice were generated using CRISPR technology. Littermates of wild-type (WT) and KO mice were subjected to the AMD preclinical models of laser induced choroidal neovascularization (CNV) with or without anti-VEGF treatment, and/or sodium iodate (NaIO3) induced retinal degeneration. CNV lesion sizes were quantified at day 7. NaIO3 lesions were longintudinally imaged by OCT and finally assessed by histology at day 21.
Results :
COL8A1 and COL8A2 are predominantly expressed in human retinal pigment epithelium (RPE) and COL8A1 expression is markedly increased in AMD lesions. In the CNV model, Col8a1 KO mice show significantly enlarged lesions compared to WT (p<0.0001). Col8a2 KO mice do not show change in lesion size (p = 0.587), while Col8a1/Col8a2 double KO mice have enlarged CNV lesions comparable to the Col8a1 single KO (p <0.0001 vs WT, p = 0.997 vs Col8a1 KO). Anti-VEGF antibody treatment effectively resolved CNV lesions in Col8a1 WT mice (76.5% of the lesions resolved), but provided only a partial therapeutic effect in the Col8a1 KO mice (19% of the lesions resolved). In the NaIO3 model, Col8a1 KO retinas show exacerbation of the subretinal lesions with increased retinal invagination occurrences (p<0.0001) and increased severity score (p = 0.002).
Conclusions :
COL8A1 is highly expressed in human RPE cells, especially in AMD lesions. Col8a1 loss in mice exacerbates AMD phenotypes such as choroidal neovascularization and subretinal lesions following RPE damage. Col8a1 KO mice also show incomplete response to anti-VEGF therapy and provide a new preclinical model to test new anti-neovascular therapeutic approaches.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.