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J. T. Davis, D. C. Otteson, P. A. Janmey, W. J. Foster; The Influence of Substrate Elastic Modulus on Müller Cell Proliferation. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2417.
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Gliotic changes in the retina are important in the retinal response to injury and the integration of retinal prosthetics. We hypothesized that Müller cells have an increased rate of proliferation on firmer substrates, such as synthetic materials and scar tissue. To test this, we measured the proliferation of Müller cells on polymeric substrates of varying elastic moduli.
A previously characterized, conditionally immortalized mouse Müller cell line was grown on Laminin-coated polyacrylamide substrates of elastic moduli of 500, 1000, and 5000 Pascals (Pa) as well as on Laminin-coated glass. The elastic modulus for a given stoichiometry of acrylamide/bisacrylamide was confirmed with a torsional rheometer in cone-plate geometry. Cultures were photographed using Hoffman illumination on an inverted Olympus microscope every 24 hours for 6 days. Parallel cultures were stained by rhodamine-phalloidin and GFAP immunohistochemistry and imaged using epifluorescence microscopy.
Over 6 days, Müller cells increased in number more rapidly on firmer substrates. In addition, Müller cells grown on softer substrates appeared smaller, with smoother contours. There was a transition point between 1000 Pa and 5000 Pa, such that cells on firmer substrates were larger, produced stress fibers, and proliferated more rapidly. Cells grown on 1000 Pa substrates were approximately half the size of those grown on 5000 Pa substrates and proliferated at less than half the rate over 6 days.
Müller cell morphology is altered when grown on substrates that are significantly firmer than typical neural tissues (1000 Pa). The increased proliferation of Müller cells on firmer substrate that we observed in vitro may contribute to the reactive gliosis that is typically observed surrounding retinal implants, in the retinal changes seen near laser-induced choroidal damage, and in the development of proliferative vitreoretinopathy near previously treated retinal tears. Ongoing studies to further characterize changes in Müller and other retinal cells on substrates of varying elastic moduli may add to the understanding of the fundamental changes in the retina induced by vitreoretinal surgical interventions.
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