gms | German Medical Science

Background: Several CFH variants were previously correlated to age-related macular degeneration (AMD). However, previous in-vitro work has mostly focussed on the common p.His402Tyr variant. In this project, we characterise an induced pluripotent stem cell derived retinal pigment epithelium (iPSC-RPE) model with CFH variants that are highly penetrant for AMD and treat them with A2E and blue light. We expect a decreased response in AMD lines compared to controls.

Methods: Three iPSC lines were derived from 3 AMD patients with a rare CFH variant (p.Lys204Thrfs*26, p.Ile184Leufs*33 or p.Arg175Gln) and 3 controls without AMD (2 wt CFH and 1 with p.His402Tyr), their characterisation was previously described. These lines were differentiated to RPE cells and exposed to A2E for 3 days, followed by blue light exposure. Afterwards, RNA-seq was performed.

Results: In both families of the donors for the lines with truncating variants, all family members with the variant had AMD (n=6 for p.Ile184Leufs*33 and n=4 for p.Lys204Thrfs*26), those without the variants did not have AMD (n=4 for the p.Ile184Leufs*33 family and n=4 for the p.Lys204Thrfs*26 family). In the p.Arg175Gln family, all genotyped AMD patients had the variant (n=6), but healthy. The cell lines displayed RPE morphology and increased expression of RPE differentiation markers RPE65, BEST, MITF, PEDF and VEGF. Treated cells displayed a decreased expression of the complement inhibitors CFH, CFI, CD59 and VTN, as well as CFHR1/2/3/5. However, this effect was reduced in the patient cell lines compared to control.

Conclusion: A paradoxically reduced decrease in CFH, CFI, CD59, VTN, and CFHR1/2/3/5 expression was observed in patient versus control lines after exposure to A2E and blue light. Our data contradict previous observations by Hallam et al. (2017), showing increased CFI and CFH expression in p.His402Tyr lines. These opposing results underline the complexity of complement regulation in AMD.