Effect of methylprednisolone on angiogenesis in syngeneic rat tracheal grafts

Airway anastomotic complications remain a cause of morbidity after clinical lung transplantation. The use of corticosteroid therapy to control pulmonary rejection has raised concern over delayed airway healing. We therefore investigated the hypothesis that the effects of methylprednisolone (MP) impair the revascularization and epithelial regeneration of heterotopic syngeneic tracheal isografts. Lewis rat tracheal segments were wrapped in omentum and implanted in the abdomen of recipient rats. All recipients received cyclosporin A (CsA) (5 mg · kg^-1 · day^-1) and were randomly allocated into three groups of 12 rats each according to the daily MF dose: group II, no MP; group III, 1 mg · kg^-1 · day^-1; and group IV, 2 mg · kg^-1 · day^-1. In each group, 6 animals were sacrificed after 7 and 14 days. Normal, untreated rats served as controls (group I). Epithelial regeneration was assessed histologically by a blinded subjective scoring system and by measurement of epithelial thickness. Tracheal revascularization was quantitated in terms of the number of blood vessels per square millimeter of tracheal wall and the vessel area was quantitated in terms of the percentage of the tracheal wall area. In animals treated with MP and CsA, the trachea exhibited significantly better regeneration after 14 days than it did in animals treated only with CaA. Epithelial regeneration was improved between 7 and 14 days in the groups treated with MP (group III, p = 0.01; group IV, p = 0.04). The epithelial thickness for all three study groups was significantly greater than that in the control group and returned toward normal after 14 days. The epithellum was significantly thinner in groups III and IV after 14 days than it was in group II after 7 days (p < 0.05). There were no significant differences among the groups in terms of revascularization at any time. We conclude that, in the setting of heterotopic rat tracheal isografts treated with CsA, angicgenesis is not inhibited and epithelial regeneration is accelerated by MP treatment.