title: The influence of substrate elastic modulus on retinal pigment epithelial cell phagocytosis.
abstract: To better understand if a complex process such as phagocytosis is influenced by substrate stiffness, we investigated the influence of substrate elastic modulus on phagocytosis in the retinal pigment epithelial (RPE) cell line ARPE-19. RPE cells lie on Bruch's membrane, directly under the retina, and phagocytose the shed photoreceptor outer segments. Bruch's membrane is known to increase in stiffness by an order of magnitude with age and thus, this study has potential relevance in explaining retinal changes in age-related macular degeneration. ARPE-19 cells were plated on laminin-coated polyacrylamide substrates of varying elastic modulus. After 14 days in culture, a solution of latex fluorescent beads suspended in PBS was placed in each well. After an incubation time of 4h, flow cytometry was performed to determine the number of cells that phagocytosed a bead. The number of ARPE-19 cells that phagocytosed a bead decreased continuously as a function of increasing substrate elastic modulus (p=0.0135), and this was found to be a linear relationship (slope=-0.03305 ± 0.01104, R2=0.4726 per 10,000 cells). Our results suggest that RPE cells display decreased phagocytosis when grown on firmer substrates, and thus, RPE cells in older eyes, in which Bruch's membrane is stiffer, may demonstrate decreased phagocytosis. Impaired phagocytosis by RPE cells may contribute to impaired metabolism of photoreceptor outer segments and to development of macular degeneration. Material stiffness may be a critical parameter in the development of neural therapies, including retinal prosthetics and stem cell therapies.
authors.affiliation: The Department of Biology & Biochemistry, The University of Houston, Houston, TX, USA.
authors.forename: Kieran S
authors.initials: KS
authors.lastname: Boochoon
authors.affiliation: The College of Optometry, The University of Houston, Houston, TX, USA.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Manarang
authors.affiliation: The Department of Physics, The University of Houston, Houston, TX, USA.
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Davis
authors.affiliation: The Department of Biology & Biochemistry, The University of Houston, Houston, TX, USA; The College of Optometry, The University of Houston, Houston, TX, USA.
authors.forename: Alison M
authors.initials: AM
authors.lastname: McDermott
authors.affiliation: The Department of Physics, The University of Houston, Houston, TX, USA; Weill-Cornell Medical College at The Methodist Hospital, Houston, TX, USA; The Departments of Ophthalmology & Bioengineering, Temple University, 3401 N. Broad Street, Philadelphia, PA 19140, USA. Electronic address: William.Foster@Temple.edu.
authors.forename: William J
authors.initials: WJ
authors.lastname: Foster
mesh_terms: D000180:Acrylic Resins; D018929:Cell Culture Techniques; D002460:Cell Line; D055119:Elastic Modulus; D006801:Humans; D007797:Laminin; D008863:Microspheres; D010587:Phagocytosis; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000502:physiology*; D000099166:Polyacrylamides
chemical_list: D000180:Acrylic Resins; D007797:Laminin; D000099166:Polyacrylamides
keywords: Flow cytometry; Mechanotransduction; Phagocytosis; Retinal pigment epithelium