Impaired Mitochondrial Function in iPSC-Retinal Pigment Epithelium with the Complement Factor H Polymorphism for Age-Related Macular Degeneration

Abstract

Age-related macular degeneration (AMD), the leading cause of vision loss in the elderly, is characterized by loss of the retinal pigment epithelium (RPE). While the disease mechanism remains unclear, prior studies have linked AMD with RPE mitochondrial defects and genetic polymorphisms in the complement pathway. This study used RPE generated from induced pluripotent stem cells (iPSC-RPE), which were derived from human donors with or without AMD and genotyped for the complement factor H (CFH) AMD high-risk allele (rs1061170, Y402H) to investigate whether donor disease state or genotype had a detrimental effect on mitochondrial function and inflammation. Results show that cells derived from donors with AMD display decreased mitochondrial function under conditions of stress and elevated expression of inflammatory markers compared to iPSC-RPE from individuals without AMD. A more pronounced reduction in mitochondrial function and increased inflammatory markers was observed in CFH high-risk cells, irrespective of disease state. These results provide evidence for a previously unrecognized link between CFH and mitochondrial function that could contribute to RPE loss in AMD patients harboring the CFH high-risk genotype.

FH loss in RPE cells causes retinal degeneration in a human RPE-porcine retinal explant co-culture model

“…However, recently an additional intracellular role for FH, independent from complement regulation, has been shown in different cell types including RPE cells [17,18]. In our previous studies [17,21], we show that loss of intracellular FH in hTERT-RPE1 cells, via CFH silencing, affects several AMD-relevant features and pathways in RPE cells in a similar way as the CFH 402H variant has been described to affect iPS-RPE cells [19,20]. FH loss in RPE cells, besides altering complement and inflammatory regulation, had a great impact on RPE cells homeostasis.…”

“…Recently, a novel function for intracellular FH has been described in several cell types and place intracellular FH as an important regulator of cell homeostasis [17, 18]. iPSC-RPE cells, carrying 402H high-risk variant of FH, show enlarged mitochondria[19] and reduced mitochondria activity [20], but whether the effects depends on intracellular FH or extra-cellular FH was not investigated. Our previous studies show that the loss of endogenous/intracellular FH in RPE cells leads to a phenotype very similar to iPSC-RPE cells carrying 402H high-risk variant of FH.…”

CFH Loss in Human RPE Cells Leads to Inflammation and Complement System Dysregulation via the NF-κB Pathway

“…For example, cfh −/− mice face a spontaneous appearance of hepatocellular carcinomas with a clear transcriptomic signature for cytokine and chemokine signaling pathways [41]. Similarly, the phenotype of mature iPSC-RPE cells carrying the CFH Y402H AMD high-risk variant is characterized by the upregulation of several inflammatory cytokines, as IL6 [42,43] and C3b deposition [44].…”

“…However, the signaling pathways involved in regulating inflammation in RPE cells are not fully characterized, and most importantly, the signaling pathways modulated by FH, not only in RPE cells, are not well known. Recently, based on the phenotype of iPS-RPE cells carrying the CFH Y402H polymorphism, it has been speculated that the complement system and the NF-κB pathway may be part of complex crosstalk of signaling pathways with the scope of regulating RPE cell homeostasis [43]. Interestingly, most cytokines differentially regulated in FH-deprived conditions are, indeed, targets of the NF-κB pathway.…”

Mutated CCDC51 Coding for a Mitochondrial Protein, MITOK Is a Candidate Gene Defect for Autosomal Recessive Rod-Cone Dystrophy

“…However, often a relatively mild phenotype in RCD patients is not reproduced in mouse models [48][49][50][51]. Studies on fibroblasts or retinal cells from patient's derived induced pluripotent stem cells [52] would be informative to evaluate putative effects of the CCDC51 variant on mitochondrial function in the retina. Patient derived cells and organoids may display ultrastructural changes as previously reported in fibroblasts [53] or reveal mitochondrial dysfunction as altered oxygen consumption rates of live cells which could be measured with a kit (Agilent Seahorse Analytics, Courtaboeuf, Les Ulis, France).…”