An overview is presented of the retinal pigment epithelium (RPE) cell in repair and regeneration. Changes in the RPE associated with repair activities have been described as metaplasia. However, evidence is presented to show that RPE cells do not become either fibroblasts or macrophages but merely adopt the appearance of these cell types in pathological conditions. The phenotypic alterations seem to be substrate-related. The fibroblast form predominates on two-dimensional substrates rich in fibronectin and in three-dimensional collagen matrices. The macrophage form seems to be associated with insubstantial or inadequate substrates such as the vitreous, photoreceptor debris and some cell surfaces. In altered circumstances the dedifferentiated RPE can rapidly revert to an epithelioid form. However, the regeneration of an effective RPE mosaic is more difficult and dependent on many factors including the size of the initial lesion, the condition of the basement area, the status of the neuroretina and the existing pathology in the eye. The importance for the regeneration of a normal functioning RPE of the cells being out of the cell cycle, establishing effective junctioning, reorganising their cytoskeleton and having the required adhesive balance with the basement membrane is emphasised.

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The purpose of this investigation was to develop a decellularised human dermis suitable for allografting. Samples of human skin were obtained from deceased donors and taken through a series of steps to remove all cellular material. The steps were: chemical removal of the epidermis, disinfection, lysing of cells in hypotonic buffer, a detergent treatment and a nuclease buffer to remove residual nuclear material. Histological preparations of the decellularised dermis produced were then investigated. In addition residual DNA content, structural strength, collagen denaturation, cytotoxicity and in vivo tissue reactivity following implantation in a murine model were examined. For all donors tested there was no change in morphology as viewed by light microscopy. Mean DNA removal was evaluated at 92.1%. There were no significant changes in structural strength or evidence of collagen degradation. The tissue did not appear to be cytotoxic or elicit an immune response when implanted in the mouse model. A decellularised tissue has been developed that would appear to be suitable for a range of surgical procedures.

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