Osteopontin Regulates AQP4 Expression by TRPV4 Activation in Müller Cells: Implications for Retinal Homeostasis.

During the intense neuronal activity in the retina, Müller cells are exposed to a hypotonic environment and activate a regulatory volume decrease (RVD) response, which depends on Aquaporin-4 (AQP4) and the calcium channel Transient Receptor Potential Vanilloid 4 (TRPV4). It was reported that Osteopontin (OPN), a cytokine and component of the extracellular matrix (ECM), may modulate the RVD of Müller cells. In other cell types, OPN participates in cell survival and migration, which Müller cells undergo to maintain retinal homeostasis.