De-Epithelialized Heterotopic Tracheal Allografts without Immunosuppressants in Dogs: Long-Term Results for Cartilage Viability and Structural Integrity

Objectives: Reconstruction of long segmental tracheal defects is difficult because no ideal tracheal substitutes are currently available. Tracheal allotransplantation maintains cartilage and epithelium viability but requires immunosuppression because of epithelial immunogenicity. We aimed to obtain an epithelium-decellularized allograft that maintains cartilage viability and to evaluate long-term outcomes of such allografts implanted on dog backs without immunosuppressants. Methods: Twenty-five tracheas harvested from mongrel dogs were used to explore the period of epithelium decellularization by combined use of 1% sodium dodecyl sulfate and an organ preservation solution and to assess the chondrocyte viability and immunogenicity of the tracheas after decellularization. Sixteen epithelium-decellularized tracheal allografts and 10 fresh tracheal segments (6 cm long) were implanted in 26 beagles for durations of 10 days and 1, 3, 6, and 12 months. Macroscopic and microscopic examinations were used to evaluate the morphology, viability, and immune rejection of the allografts. Safranin-O staining was used to detect glycosaminoglycans. Results: The epithelium disappeared after 24 hours of decellularization. At 72 hours, almost no nuclei remained in the mucosa, while the mean survival rate of chondrocytes was 88.1%. Histological analysis demonstrated that the allograft retained intact tracheal rings and viable cartilage after heterotopic implantation for 1 year, with no immunological rejection. There were no significant differences in the glycosaminoglycan contents among the implanted epithelium-decellularized allografts. Conclusions: Epithelium-decellularized tracheal allografts with chondrocyte viability can be achieved by combined use of a detergent and organ preservation solution, which showed satisfactory cartilage viability and structural integrity after long-term heterotopic transplantation. Further studies on orthotopic transplantation are needed to assess the feasibility of allografts in reconstructing long segmental tracheal defects.

Improved metabolism and redox state with a novel preservation solution: implications for donor lungs after cardiac death (DCD)

Lungs donated after cardiac death (DCD) are an underutilized resource for a dwindling donor lung transplant pool. Our study investigates the potential of a novel preservation solution, Somah, to better preserve statically stored DCD lungs, for an extended time period, when compared to low-potassium dextran solution (LPD). We hypothesize that Somah is a metabolically superior organ preservation solution for hypothermic statically stored porcine DCD lungs, possibly improving lung transplant outcomes. Porcine DCD lungs (n = 3 per group) were flushed with and submerged in cold preservation solution. The lungs were stored up to 12 h, and samples were taken from lung tissue and the preservation medium throughout. Metabolomic and redox potential were analyzed using high performance liquid chromatography, mass spectrometry, and RedoxSYS®, comparing substrate and pathway utilization in both preservation solutions. Glutathione reduction was seen in Somah but not in LPD during preservation. Carnitine, carnosine, and n-acetylcarnosine levels were elevated in the Somah medium compared with LPD throughout. Biopsies of Somah exposed lungs demonstrated similar trends after 2 h, up to 12 h. Adenosine gradually decreased in Somah medium over 12 h, but not in LPD. An inversely proportional increase in inosine was found in Somah. Higher oxidative stress levels were measured in LPD. Our study suggests suboptimal metabolic preservation in lungs stored in LPD. LPD had poor antioxidant potential, cytoprotection, and an insufficient redox potential. These findings may have immediate clinical implications for human organs; however, further investigation is needed to evaluate DCD lung preservation in Somah as a viable option for transplant.