97th DOG Annual Meeting 1999



S. Grisanti, P. J. Esser, K.-U. Bartz-Schmidt, N. Kociok, T. T. Luther, K. Heimann

Introduction: RCS (Royal College of Surgeons) rats are characterized by a progressive retinal degeneration. The orthotopic transplantation of RPE can delay the disease. The aim of this study was to evaluate the effect induced by xenografts in non-immunosuppressed individuals.

Methods: Freshly isolated, adult porcine RPE cells were used as xenografts and implanted when recipients were 17 to 21 days old. Control subjects received sham injections. The extent of photoreceptor rescue by subretinal transplants was determined by counting the maximum layers of surviving photoreceptor nuclei in histologic sections. Cellular immune response was evaluated by immunohistochemistry.

Results: Subretinal xenografts were able to induce a dramatic rescue effect compared to non- or sham-injected eyes. Both xenografts in the anterior chamber and subcutaneous tissue led to an inflammatory cellular infiltration with a peak at 3-4 weeks after surgery. Despite the quiescent morphologic appearance and absence of a similar cellular infiltration in the subretinal space, retinal degeneration is delayed only for a limited time.

Conclusion: RPE xenografts in the subcutaneous space and in the anterior chamber are rejected by a delayed but vigorous inflammatory cell infiltration. Subretinal RPE xenografts are protected from a strong cellular rejection, but undergo a slow functional deterioration, reflected by a decline in their ability to rescue adjacent photoreceptors.

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