Activin A improves retinal pigment epithelial cell survival on stiff but not soft substrates

Abstract

In several retinal degenerative disease pathologies, such as dry age-related macular degeneration (AMD), the retinal pigment epithelium (RPE) cell monolayer becomes dysfunctional. Promising tissue engineering treatment approaches implant RPE cells on scaffolds into the subretinal space. However, these approaches are not without challenges. Two major challenges that must be addressed are RPE dedifferentiation and the inflammatory response to cell/scaffold implantation. Design and optimization of scaffold cues for the purpose of RPE transplantation remain relatively unexplored, specifically the mechanical properties of the scaffolds. Prior work from our group indicated that by varying substrate moduli significant differences could be induced in cell cytoskeleton structure, cellular activity, and expression of inflammatory markers. We hypothesized that Activin A would provide rescue effects for cells demonstrating dedifferentiated characteristics. Results demonstrated that for cells on low modulus scaffolds, the mechanical environment was the dominating factor and Activin A was unable to rescue these cells. However, Activin A did demonstrate rescue effects for cells on high modulus scaffolds. This finding indicates that when cultured on scaffolds with an appropriate modulus, exogenous factors, such as Activin A, can improve RPE cell expression, morphology, and activity, while an inappropriate scaffold modulus can have devastating effects on RPE survival regardless of chemical stimulation. These findings have broad implications for the design and optimization of scaffolds for long-term successful RPE transplantation.

Hydrogel-Supported, Engineered Model of Vocal Fold Epithelium

“…When cultured on relatively soft substrates, these cells dedifferentiate into fibroblast-like cells, the mechanical environment was the dominating factor, and Activin A was unable to rescue these cells. 62 In our case, all HA10-based substrates, as well as HA24 with AG73, do not promote the establishment of epithelial cell colonies with cell−cell contacts. These substrates failed to establish strong cellar adhesion through integrins.…”

“…Retinal pigment epithelium cells are also known to dedifferentiate in culture. When cultured on relatively soft substrates, these cells dedifferentiate into fibroblast-like cells, the mechanical environment was the dominating factor, and Activin A was unable to rescue these cells …”

TGF-β Superfamily Signaling in the Eye: Implications for Ocular Pathologies

“…It has been shown that BMP9 can regulate angiogenesis by blocking VEGF and basic fibroblast growth factor-induced neovascularization [ 184 ], and delivery of exogenous BMP9 has been shown to reduce CNV in mice [ 181 ]. A comprehensive analysis of in vitro experiments also showed that BMP2 stimulates VEGF release from Müller cells [ 185 ] and that Activin A is released from the mesenchyme to induce RPE development [ 186 , 187 ]. Similarly, Follistatin, a regulator of activin signaling, is predominantly expressed in ocular angiogenesis and was also identified as a binding partner of angiogenin, an angiogenic protein synthesized in human choroid/retina and present at high levels in AMD eyes [ 188 ].…”

Coculture techniques for modeling retinal development and disease, and enabling regenerative medicine

“…125,131 Few studies have specifically examined the effect of scaffold stiffness on RPE culture and more work is required to identify the optimal tethering and stiffness properties which will facilitate cocultures models of the outer retina. 117,[131][132][133] Poly lactic-co-glycolic acid is a popular biomaterial for drug delivery and tissue engineering, and is currently being investigated as a vehicle for the subretinal delivery of iPSC-derived RPE to treat AMD. 36,124 Its advantages include the availability of fabrication methods, biocompatibility, biodegradability, and tunable mechanical properties.…”