A new study in The American Journal of Pathology reports for the first time that the injection of neuropeptide vasoactive intestinal peptide (VIP) directly into the eye of mice enhanced corneal graft survival. VIP produced other benefits, including acceleration of endothelial wound closure, protection of corneal endothelial cells (CEnCs), and improved corneal graft clarity. If proven successful in clinical studies, this novel approach may help alleviate visual loss in many patients with corneal disease.

In this study, researchers evaluated the effect of VIP, a 28 amino acid neuropeptide, on corneal tissue in cell culture and living animals who received corneal transplants. Recognised as an immunoregulatory and protective factor in various organ systems, VIP is found in the aqueous humour of the eye and may be secreted by CEnCs. Although it is known that VIP can help preserve the integrity of CEnCs and may be used by eye banks to improve the survival of donor corneas, until now it has been unclear whether administration of VIP in vivo after corneal transplantation could improve graft survival.

The researchers said when corneal endothelial cells were exposed to the substances known to induce apoptosis (cell death), such as interferon-γ or tumor necrosis factor-α, VIP showed a dose-dependent protective effect.

In live mice who underwent corneal transplantation, grafts were more transparent in VIP-treated mice compared to controls four to eight weeks after transplantation. Eight weeks after transplantation, 85% of VIP-treated grafts survived compared to 0% of control grafts, and corneal endothelial cell density was higher in VIP-treated corneas compared to controls.

“Millions of patients around the world are blind due to corneal opacity, and they are in dire need of corneal transplantation. Unfortunately, there is a significant shortage of donor corneas across the world. On the other hand, many donated corneas cannot be used for transplantation due to inadequate endothelial cells. Moreover, corneal transplants can deteriorate over time due to continuous loss of CEnCs,” noted Harvard ophthalmology professor Reza Dana. “If confirmed in further clinical studies, we believe that the use of VIP will increase the number of donated corneas suitable for transplantation and improve the outcomes of corneal transplantation.”