Muller Cell Expression of Genes Implicated in Proliferative Vitreoretinopathy Is Influenced by Substrate Elastic Modulus

PURPOSE. Matrix stiffness is recognized increasingly as a significant factor in cell and tissue function. To understand better the mechanosensitivity of Muller cells and its association with vitreoretinal disorders, we examined morphology, propagation, and expression of genes in Muller cells that were cultured on substrates of varying elastic moduli. METHODS. A conditionally immortalized mouse Muller cell line was cultured on laminin-coated polyacrylamide substrates with calibrated Young's moduli. Glass was used as a control. Phase contrast, fluorescence, and atomic force microscopy were used to study cell morphology and propagation. Expression of extracellular matrix (ECM) genes was analyzed using quantitative reverse-transcription PCR. RESULTS. The adherent area, stiffness, and propagation of Muller cells all are affected by matrix stiffness, but to different extents and with different ranges of sensitivity. Of 85 ECM genes tested 11 showed a continuous > 4-fold increase or decrease in mRNA expression as a function of the substrate elastic modulus. The changes were statistically significant in four genes: connective tissue growth factor (Ctgf, P = 0.04), tenascin C (Tnc, P = 0.035), Collagen I alpha 1 (Col1a1, P = 0.0001), and Collagen IV alpha 3 (Col4a3, P = 0.05), with all showing increased expression on softer substrates. CONCLUSIONS. There are significant changes in morphology, cytoskeletal integrity, and gene regulation in Muller cells as a function of the stiffness of the substrate. Changes in local tissue elastic modulus may have a role in vitreoretinal disorders. These findings also may have implications for strategies for improved integration of retinal prosthetics, and for stem cell therapies, particularly targeting the transcriptional regulators YAP and TAZ. (Invest Ophthalmol Vis Sci. 2012;53:3014-3019) DOI:10.1167/iovs.11-8450