Kevin Kennelly, Cliona OÕFarrelly, David Keegan
Purpose: The success of subretinal transplantationhas been limited by considerable early graft loss despitepharmacological suppression of the adaptive immunesystem. We postulated that the early innate immune response is the predominant factor in determininggraft survival and chose a mouse model of retinalpigment epithelial (RPE) cell transplantation to inves-tigate this.
Method: Cytokine expression was assessed in SV40T+DH01 RPE cells under baseline conditions and follow-ing graft preparation. Subretinal allografts were per-formed in healthy C57BL/6 mice (n = 16). Shamtransplants (n = 16) and unoperated eyes (n = 4) werealso examined. Eyes were harvested on post-operativedays (POD) 1, 3, 7 and 28 (n = 4/group/time-point).Cryosections were immunolabelled for graft (SV40T),macrophage (CD11b & F4/80), neutrophil (Gr-1Ly-6G), and T-lymphocyte (CD3-?) markers.Apoptosis/necrosis was assessed by TUNEL-labelling.Images captured with a confocal microscope were ana-lysed using Imaris software.
Results: Graft preparation significantly increasedinflammatory cytokine and chemokine expression,particularly of KC/GRO/CINC (CXCL1) (p < 0.05). Theproportion of the subretinal bolus comprising graftcells (SV40T+) reduced significantly (p < 0.001)between POD3 (89.94% ± 3.87%) and POD7(19.75% ± 7.24%). Infiltrating CD11b+, F480+andGr-1 Ly-6G+cells increased significantly (p < 0.05) andpredominated over SV40T+cells by POD7. Graftengulfment by neutrophils and macrophages occurredat POD7. Expression of CD3-? remained low across alltime-points. No graft cells survived to POD28. Conclusion: These novel studies reveal a critical rolefor innate immunity in early subretinal graft rejection.Successful subretinal transplantation will requiregreater emphasis on limiting innate immune-mediatedgraft loss, rather than merely suppressing the adaptiveimmune response.