Our strategy is mechanism based. First, CNTFRα is gradually lost during corneoscleral explant preservation.
15 Second, CE cell CNTFRα in the donor corneas likely is under the modulation of the endogenous CNTF in the recipient eye. CNTF was discovered in an extract of ciliary body, iris, and choroid.
28,29 CNTF, a cytokine that does not have a classic secretory signal peptide sequence, is released only after injury through an unknown mechanism.
30 We previously demonstrated that CNTF is released in a complex with the CNTF-binding CNTFRα by CE cells surviving the oxidative stress.
10 We hypothesize that CNTF is released from the recipient's ciliary body and iris in response to transplant injury to modulate the donor CE cell CNTFRα. In addition to the fact that CNTF is present in the aqueous humor of the enucleated (injured) bovine
17 and human (data not shown) eyes, our hypothesis is supported by studies of the role of CNTF in optic nerve injury. For example, CNTF not only promotes the survival of the retinal ganglion cells in intraorbital nerve crush injury
31 but also is the mediator of lens injury-induced beneficial effects on retinal ganglion cell survival and regeneration in optic nerve injury.
32 Thus, VIP treatment, while preserving the level of CNTFRα in CE cells in corneoscleral explant in storage for transplantation (
Fig. 1), increased the CE cell responsiveness to CNTF modulation (
Fig. 2), which might have led to enhanced preservation of the corneal endothelium. Indeed, results in
Figures 3 and
4 and
Tables 3 to
5 demonstrated, at both gross and microscopic levels, that after incubation at 37°C and in the presence of CNTF, the corneal endothelium of the corneoscleral explants treated with VIP was less damaged than that in their paired controls.