Human macular Muller cells rely more on serine biosynthesis to combat oxidative stress than those from the periphery

The human macula is more susceptible than the peripheral retina to developing blinding conditions such as age-related macular degeneration, diabetic retinopathy. A key difference between them may be the nature of their Muller cells. We found primary cultured Muller cells from macula and peripheral retina display significant morphological and transcriptomic differences. Macular Muller cells expressed more phosphoglycerate dehydrogenase (PHGDH, a rate-limiting enzyme in serine synthesis) than peripheral Muller cells. The serine synthesis, glycolytic and mitochondrial function were more activated in macular than peripheral Muller cells. Serine biosynthesis is critical in defending against oxidative stress. Intracellular reactive oxygen species and glutathione levels were increased in primary cultured macular Muller cells which were more susceptible to oxidative stress after inhibition of PHGDH. Our findings indicate serine biosynthesis is a critical part of the macular defence against oxidative stress and suggest dysregulation of this pathway as a potential cause of macular pathology.