Transplantation in Corneal Scars – Can We Judge Rejection Rate at the Time of Surgery Based on IL–1 Production?

Abstract

Abstract: : Purpose: Corneal graft success rate decreases significantly in case of vascularized corneal scars. Studies in animal eyes have shown that proinflammatory cytokine IL–1α stimulates corneal neo–vascularization and increases graft rejection rate. In this study we have investigated: a) the amount of IL–1α secreted from human corneas with different grade of vascularization and b) does clinical judgement of graft rejection risk based on degree of vascularization correlates well with IL–1α secretion at the time of surgery. Methods: Study included 28 patients undergoing corneal grafting due to corneal scar. Graft recipients were divided into groups according to the number of vascularized corneal quadrants: none (0/IV, n=12), one quadrant (I/IV, n=5), two quadrants (II/IV, n=4) and four quadrants (IV/IV, n=6). Recipient corneas were collected during surgery and IL–1α cytokine secretion was measured by immunoassay (R&D Systems, USA). Controls were donor corneas unsuitable for transplantation due to low endothelial cell count. Statistical analysis was made by Student t–test. Graft rejection rate was calculated for each investigated group up to 1 year postoperatively. Results: Mean concentration of IL–1α in vascularized corneal scars at the time of surgery was 6,0 ± 3.93 pg/mm³; significantly higher as compared to controls (1,25 ± 2,03 pg/mm³). Mean IL–1α production correlated well with the amount of blood vessels in the cornea in all groups except highly vascularized scars: 5,17 ± 3,65 pg/mm³ for 0/IV; 8,02 ± 2,51 pg/mm³ for I/IV; 8,27 ± 3,62 pg/mm³ for II/IV and 4,47 ± 5,03 pg/mm³ for IV/IV corneal scars. Corneal graft rejection rate correlated well with the amount of IL–1α production at the time of surgery. Conclusions: Graft rejection risk in patients with corneal scars seams to be connected with the amount of IL–1α secreted by the recipient cornea. However, IL–1α clearly isn’t the only promotor of graft rejection in human eyes, since it’s level was low in highly vascularized scars although these patients have high rejection rate. Further research is underway to explore which cytokine(–s) mediate allograft rejection in highly vascularized corneal scars.

Keywords: cornea: basic science • cornea: clinical science • immunomodulation/immunoregulation