PDGF Receptor Alpha is key for Müller cell homeostasis functions

Abstract

Purpose : Müller cells, the major retinal macroglia, contribute to maintain vascular integrity as well as retinal fluid and ion homeostasis. Although PDGF receptor expression in Müller glia has been reported earlier, their actual role for Müller cell function and intimate interaction with cells of the retinal neurovascular unit remains unclear.

Methods : Müller cell-specific PDGF receptor alpha (PDGFRα) knockout (KO) were generated by crossbreeding a tamoxifen-inducible Glast-CreER^T2 driver line with PDGFRα^fl/fl mice. We isolated Müller cells (4 weeks post-tamoxifen injection) by MAC sorting and analyzed the efficiency of Müller cell-specific deletion of PDGFRα at mRNA and protein level by qPCR and immunofluorescence. To analyze the functional role of PDGF in Müller cell physiology, we performed volume regulation experiments in vital retinal slices. We also evaluated the retinal functional integrity by electroretinogram recordings (ERG). To investigate the role of PDGF signaling in Müller glia in retinal diseases, we subjected Müller cell-specific PDGFRα KO mice to a model of choroidal neovascularization (CNV) and analyze the retinal vasopermeability.

Results : We demonstrated the usability of double transgenic Glast-CreER^T2;PDGFRα^fl/fl (PDGFRα KO) mice to induce Müller cell-specific PDGFRα knockout. The vast majority of isolated Müller cells from those mice were lacking immunoreaction for PDGFRα and the mRNA levels of Pdgfrα were also significantly downregulated in comparison to wild type controls . PDGFRα-deficient Müller cells could not counterbalance hypoosmotic stress as efficiently as their wildtype counterparts. In wildtypes, the PDGFRα ligand PDGF-BB prevented Müller cell swelling induced by administration of barium ions. This effect could be blocked by the PDGFR family inhibitor AC710. PDGF-BB could not restore the capability of an efficient volume regulation in PDGFRα KO Müller cells. Additionally, PDGFRα KO mice displayed reduced ERG response. Remarkably, Müller cell-specific PDGFRα KO resulted in less vascular leakage and smaller lesion area in the CNV model.

Conclusions : In sum, our data support the hypothesis that PDGF signaling is central for retinal functions under physiological conditions. These data imply that targeting PDGF to treat retinal neovascular diseases may have short term beneficial effects, but may elicit unwarranted side effects given the putative negative effects on Müller cell homeostatic functions.

This is a 2021 ARVO Annual Meeting abstract.