Effect of bcl–xl overexpression in donor corneas on survival of corneal allografts in mice.

Abstract

Abstract: : Purpose: To overexpress bcl–xl, an anti–apoptotic gene product, in the cornea of mice by using bcl–xl transgenic mice and adenoviral vector mediated gene transfer, and to observe the effect of bcl–xl overexpression by either modality on corneal allograft survival. Methods: Donor corneas from the bcl–xl transgenic and wild–type (both CB57L/6 background) mice were transplanted orthotopically onto BALB/c recipient mice. For adenoviral vector mediated gene transfer, CB57L/6 mouse corneas were infected with replication–deficient adenovirus encoding bcl–xl (ad–bcl–xl) or empty vector ex vivo and then transplanted to BALB/c recipient mice. To suppress immune responses of the hosts to the adenoviral vector, mice receiving ad–bcl–xl– or empty vector–infected corneal allografts were randomized to receive either anti–CD154 (CD40L) antibody or control immunoglobulin by intraperitoneal injection perioperatively and twice weekly after surgery. After orthotopic corneal transplantation, all grafts were evaluated clinically by slit lamp biomicroscopy over eight weeks. Results: Corneal allograft survival improved from 40% in the wild–type mice to 60% in the bcl–xl transgenic mice at week 8 (P<0.05). However, ad–bcl–xl infected corneal allografts exhibited an accelerated course of immune rejection with 0% survival rate at week 4.5 whereas empty vector–infected corneal allografts had a survival rate of 20% by the end of 8 weeks. Immunomodulation with anti–CD154 antibody has been shown to promote universal acceptance of corneal transplants in murine recipients and to prolong adenovirus–mediated gene expression in nonocular systems. However, systemic administration of anti–CD154 showed no beneficial effect on inhibiting immune rejection of ad–bcl–xl–infected corneal allografts. Conclusions: Overexpression of the anti–apoptotic gene product bcl–xl in the donor tissue of bcl–xl transgenic mice promotes corneal graft survival in allogeneic recipients. However, gene transfer using ad–bcl–xl vector failed to promote the survival of corneal allografts with or without immunomodulation.

Keywords: transplantation • apoptosis/cell death • gene transfer/gene therapy