Long-term changes to in vitro preserved bioengineered human trachea and their implications for decellularized tissues

Bioengineered tissues created for transplant will be expected to survive and contribute to function over the lifetime of the individual. To evaluate potential intrinsic changes and degradation of the extracellular matrix of decellularized human tissue scaffolds, human decellularized tracheas were evaluated over a one year period in vitro. Human tracheas were decellularized and stored for one year in phosphate-buffered saline at 4 °C in the presence of antibiotics and anti-mycotics, and their structural, mechanical, and angiogenic properties compared to baseline values. Results showed that stored human decellularized tracheas were increasingly degraded resulting in a loss of extracellular matrix architecture - in particular of collagenous and elastic fiber structure -and decreased mechanical and angiogenic properties. The mechanical alterations of the extracellular matrix but not the deterioration and microstructure were not improved by using a natural cross-linking agent. These findings demonstrate that human decellularized tracheas, stored for one year in phosphate-buffered saline solution at 4 °C, would not meet the demands for a tissue engineering matrix and likely would not yield a suitable graft for lifelong implantation. The degradation phenomenon observed in vitro may be further enhanced in vivo, having clinical relevance for tissues that will be transplanted long-term and this should be carefully evaluated in pre-clinical settings.