iPSC-Derived LCHADD Retinal Pigment Epithelial Cells Are Susceptible to Lipid Peroxidation and Rescued by Transfection of a Wildtype AAV-HADHA Vector.

PURPOSE: Progressive choroid and retinal pigment epithelial (RPE) degeneration causing vision loss is a unique characteristic of long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (LCHADD), a fatty acid oxidation disorder caused by a common c.1528G>C pathogenic variant in HADHA, the α subunit of the mitochondrial trifunctional protein (TFP). We established and characterized an induced pluripotent stem cell (iPSC)-derived RPE cell model from cultured skin fibroblasts of patients with LCHADD and tested whether addition of wildtype (WT) HAHDA could rescue the phenotypes identified in LCHADD-RPE.

METHODS: We constructed an rAAV expression vector containing 3' 3xFLAG-tagged human HADHA cDNA under the transcriptional control of the cytomegalovirus (CMV) enhancer-chicken beta actin (CAG) promoter (CAG-HADHA-3XFLAG). LCHADD-RPE were cultured, matured, and transduced with either AAV-GFP (control) or AAV-HADHA-3XFLAG.

RESULTS: LCHADD-RPE express TFP subunits and accumulate 3-hydroxy-acylcarnitines, cannot oxidize palmitate, and release fewer ketones than WT-RPE. When LCHADD-RPE are exposed to docosahexaenoic acid (DHA), they have increased oxidative stress, lipid peroxidation, decreased viability, and are rescued by antioxidant agents potentially explaining the pathologic mechanism of RPE loss in LCHADD. Transduced LCHADD-RPE expressing a WT copy of TFPα incorporated TFPα-FLAG into the TFP complex in the mitochondria and accumulated significantly less 3-hydroxy-acylcarnitines, released more ketones in response to palmitate, and were more resistant to oxidative stress following DHA exposure than control.

CONCLUSIONS: iPSC-derived LCHADD-RPE are susceptible to lipid peroxidation mediated cell death and are rescued by exogenous HADHA delivered with rAAV. These results are promising for AAV-HADHA gene addition therapy as a possible treatment for chorioretinopathy in patients with LCHADD.