A new model of retinal pigment epithelium transplantation with microspheres

Objectives: To develop a 3-dimensional carrier system for subretinal transp lantation of human fetal retinal pigment epithelial (HFRPE) cells and to as sess their growth pattern in the rabbit subretinal space. Methods: After a standard 3-port vitrectomy, HFRPE cells grown as microsphe res on cross-linked fibrinogen were introduced into the subretinal space of rabbits. The eyes were studied at 7, 14, and 30 days after surgery by opht halmoscopy and light microscopy. Results: Ophthalmoscopically, at day 7, 11 (61%) of the 18 eyes showed radi ating hyperpigmentation around the transplanted HFRPE microspheres. The res ults of a histological examination revealed a monolayer outgrowth of HFRPE cells, overlying host retinal pigment epithelium. The control eyes revealed a patch of chorioretinal atrophy with lymphocytic infiltration around the microspheres. Conclusions: Human fetal retinal pigment epithelial cells grown as microsph eres on cross-linked fibrinogen can be successfully transplanted into the s ubretinal space. Cells can survive for at least 1 month and form a monolaye r over the host retinal pigment epithelium cells, with a mild local inflamm atory response. The difference in inflammatory responses between the eyes t hat underwent transplantation and the control eyes may suggest a modulating effect of the HFRPE cells on inflammation, immunity, or both. This new xen ogenic model may have importance in the study of subretinal transplant cell biology and the associated immune response. Clinical Relevance: The results of this study may be important for better u nderstanding of the mechanisms of retinal pigment epithelium cell behavior after transplantation. The proposed model may be applicable for future clin ical and experimental investigations in the area of retinal pigment epithel ium transplantation.