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Laura Bredow, Katrin Wacker, Thomas Reinhard, Johannes Schwartzkopff; Survival Of Different Corneal Cell Layers Following Experimental Limbo-keratoplasty. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3518.
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© ARVO (1962-2015); The Authors (2016-present)
In patients with limbal stem cell deficiency transfer of a corneal graft together with parts of the adjacent limbus (limbo-keratoplasty, LKP) is one approach to restore corneal clarity. For this method, the corneal transplant is trephined eccentrically to include parts of the limbus. As few experimental data are available for limbocorneal grafts, LKP was established experimentally in rats and compared to penetrating keratoplasty (PKP).
In all experiments, one conventional and one limbo-graft were prepared from the same donor and used for LKP or for PKP, respectively. Allogeneic LKP or PKP was performed between Wistar donor and Lewis recipient rats. Corneas were analyzed clinically for signs of opacity and vascularization. Rejection time points were determined and infiltrating leukocytes were stained histologically. Additionally, syngeneic LKP or PKP was performed between GFP-transgenic Lewis donor rats and GFP-negative litter mates as recipients to determine the origin of different corneal cell types. The vascularization pattern was documented clinically. Six weeks later, corneal flatmounts were analyzed by confocal microscopy for GFP-expressing cells.
Limbo-grafts showed an earlier and stronger opacification compared to conventional transplants. More CD45+ leukocytes, CD4+ T cells and CD163+ macrophages were stained in limbo-grafts. Vascularisation was increased in the transplanted limbal area. Limbus derived, GFP-positive vascular structures grew out into the host cornea. Six weeks after syngeneic LKP or PKP, no GFP-expressing epithelial cells were found on the grafts. Endothelial and stromal cells remained GFP-positive.
A stronger immune reaction occurs in experimental LKP compared to conventional PKP. This may be a result of more antigen presenting cells in the limbus together with an increased vascularization of the graft. Grafted limbal areas regained access to the host blood-vessel system. In human LKP, this is thought to be required for survival of the grafted limbus. However, in our rat model, despite vascularisation of the transplanted limbus the host replaced all epithelial cells. We therefore hypothesize that access of blood vessels between host and grafted limbus rather promotes rejection than maintains functionality of the limbal graft in the rat.
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