Influence of Mesenchymal Stem Cells on Cryopreserved Tracheal Allografts in Rabbits

BACKGROUND: Ischemic injury and the rejection process are the main reasons for graft failure in tracheal transplantation models. To enhance the acceptance, we investigated the influence of mesenchymal stem cells (MSCs) on tracheal allografts. METHODS: Extracted tracheal grafts from New Zealand white rabbits were cryopreserved for 4 weeks and orthotopically transplanted (control group A, n=8). In group B (n=8), cyclosporin A (CsA, 10 mg/kg) was injected daily into the peritoneal cavity. In group C (n=8), MSCs (1.0×10(7) cells/kg) from the same donor of the tracheal allograft, which had been pre-cultured for 4 weeks, were infused intravenously after transplantation. In group D (n=8), MSCs were infused and CsA was injected daily. Four weeks after transplantation, gross and histomorphological assessments were conducted for graft necrosis, measuring the cross-sectional area of the allograft, determining the degree of epithelization, lymphocytic infiltration, and vascular regeneration. RESULTS: The morphologic integrity of the trachea was retained completely in all cases. The cross-sectional areas were decreased significantly in group A (p=0.018) and B (p=0.045). The degree of epithelization was enhanced (p=0.012) and the lymphocytic infiltration was decreased (p=0.048) significantly in group D compared to group A. The degree of vascular regeneration did not differ significantly in any of the groups. There were no significant correlations among epithelization, lymphocytic infiltration, and vascular regeneration. CONCLUSION: The administration of MSCs with concurrent injections of CsA enhanced and promoted epithelization and prevented lymphocytic infiltration in tracheal allografts, allowing for better acceptance of the allograft.