Abstract
Purpose :
To determine how the biosynthetic pathway of elovanoid synthesis is altered by the mutation (S163R) in CTRP5 found in Late-Onset Retinal Degeneration.
Methods :
We generated induced pluripotent stem cells (iPSCs) from L-ORD patients and unaffected siblings (controls) and differentiated them into retinal pigment epithelium (RPE). iPSC-RPE in serum free media were fed approximately 5 photoreceptors (POS)/cell for 4 hours to recapitulate shedding and disc phagocytosis or incubated with 1µM 32:6 and 34:6 free fatty acids (VLC-PUFAs) for 24 hours in 0.5% serum containing media. Media and cell lysate were collected for LC-MS/MS-based metabolipidomic analysis.
Results :
Metabolipidomic analysis revealed iPSC-RPE fed POS or VLC-PUFAs secrete stable elovanoid biosynthetic intermediates (27s-hydroxy 32:6 n-3 and 29s-hydroxy 34:6 n-3) in a polarized manner, predominantly apical. Control iPSC-RPE secrete significantly more elovanoids, ELV-N32 and ELV-N34, compared to patients. In the absence of POS or VLC-PUFAs 27s-hydroxy 32:6 n-3 was still detected in controls, but not patient iPSC-RPE. There were no differences observed in the apical or basal media composition of secreted DHA, arachidonic acid (AA) , or eicosapentaenoic acid or in the amounts of mono-hydroxy DHA and AA metabolites in cell lysates in patients compared to controls. However, DHA-derived lipid mediator, neuroprotectin D1 (NPD1) was found to be secreted significantly higher in controls (p<0.05).
Conclusions :
Our data suggests that CTRP5 is important for omega-3 fatty acid metabolism in POS shedding and phagocytosis in RPE and that elovanoids play a role in neuroprotection and in sustaining photoreceptor cell integrity in retinal degenerations.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.