Design and Validation of a Bioreactor for Scleral Tissue

Statement of Purpose: The design of a bioreactor for study of the ocular sclera is described. The sclera, which is the outer connective tissue layer of the eye, is altered in myopia (near-sightedness), exhibiting thinning due to decreased collagen synthesis and increased levels of active matrix metalloproteinase 2 (MMP-2). We have previously reported the development of enzymaticallydegradable semi-interpenetrating polymer networks (edsIPNs) for promotion of new scleral growth as a means of reinforcing the weakened walls of myopic eyes. For in vitro testing of edsIPNs, it is important to simulate as closely as possible the natural environment of the sclera, which is under tension from intraocular pressure (IOP). This is likely to influence collagen synthesis and MMP levels, both of which are of interest in physiologically relevant evaluation of edsIPNs and tissue response to pharmacological therapies. Methods: Our scleral bioreactor has two chambers, allowing independent treatment of the two surfaces of cultured sclera, which is secured and sealed by ringshaped grips around its circumference. The grips can accommodate tissue punches from 8to 14-mm in diameter, allowing samples from eyes of different animals to be studied. Media is supplied to each chamber from independent glass reservoirs that are loosely capped and adjustable in height to allow establishment of a pressure differential between the chambers, thereby simulating IOP.