Minimal dose of cyclosporin A for tracheal allografts

Background. Minimizing immunosuppression after allotransplantation is desirable. Methods. We assessed the minimal dose of cyclosporin A for viable tracheal allografts in 50 dogs. Each tracheal transplant, consisting of a six-ring segment of cervical trachea, was harvested and heterotopically implanted into the omentum. In group I (n = 10), transplantation into each dogʹs own omentum was performed as a control. The remaining 40 tracheal segments were randomly assigned to four recipient groups receiving either no treatment (group II, n = 10), 10 mg · kg−1 · day−1 of cyclosporin A (group III, n = 10), 15 mg · kg−1 · day−1 of cyclosporin A (group IV, n = 10), or 20 mg · kg−1 · day−1 of cyclosporin A (group V, n = 10). After 10 or 28 days, the tracheal segments were evaluated histologically. Results. Epithelial regeneration in group IV was significantly better than that in groups I, II, or III on posttransplantation day 10. Only group IV showed no difference in epithelial viability from group I on posttransplantation day 28. In terms of vascularity, groups IV and V exhibited no differences from group I as evidenced by vascular endothelial morphology. Conclusions. We conclude that an appropriate dose of 15 mg · kg−1 · day−1 of cyclosporin A may be used to maintain tracheal allograft viability.