Abstract
Purpose: :
One hallmark of age-related macular degeneration (AMD) is reduced attachment of the retinal pigment epithelium (RPE) to Bruch’s membrane. This is caused by age-related changes on Bruch’s membrane which lead to a decline in integrin ligands and an upregulation of anti-adhesive molecules such as tenascin-C. We investigated whether modification of RPE cell integrins can overcome the inhibitory environment of the pathological Bruch’s membrane and therefore potentially improve the adhesion of transplanted RPE cells.
Methods: :
Integrins on rat RPE cells were activated in vitro by addition of manganese. The adhesion of the cells was assessed on extracellular matrix (ECM) components of Bruch’s membrane and on Bruch’s membrane explants. The inhibitory effect of tenascin-C on the adhesion was evaluated. In parallel, tenascin C upregulation was assessed in a laser-induced rat model of AMD to determine if this model could be useful to test strategies to overcome tenascin-C-mediated inhibition of adhesion in vivo.
Results: :
Bruch's membrane ECM molecules promoted the adhesion of RPE cells in the order fibronectin > collagen type IV > laminin > collagen type I > control. The addition of manganese further increased the adhesion to collagen type IV by 49±12% (p=0.023, n=3), and to Bruch’s membrane explants by 29±7% (p=0.017, n=3). Tenascin-C inhibited the adhesion of the RPE cells significantly by 70±14% (p=3.9x10-6, n=3) but the addition of manganese overcame this effect almost completely (value came back to 74±16%, p=1.5x10-3, n=3). In the animal model, tenascin-C was strongly upregulated in the rat eyes around the lesion site.
Conclusions: :
The results demonstrate that the activation of rat RPE cell integrins can increase adhesion to ECM components of Bruch’s membrane as well as to tenascin-C. Since manganese is toxic, other ways of integrin activating agents have to be used for in vivo application. This can be achieved through the overexpression of intracellular binding partners such as talins and kindlins. The rat laser model exhibited strong upregulation of tenascin C at the lesion sites, as occurs in human AMD. Thus, integrin modulation is a potentially promising strategy to improve RPE transplantation for AMD and the rat laser model may be useful to test the effect of RPE integrin modulation in vivo as a first step to clinical translation.
Keywords: age-related macular degeneration • retinal pigment epithelium • Bruch's membrane