Amnion-based scaffold with enhanced strength and biocompatibility for in vivo vascular repair.

Current vascular replacement grafts used in congenital heart defect corrective surgery have poor longevity and growth potential. Recipient patients often require multiple reoperations. Tissue engineering has the promise to produce a graft with the potential to grow, remodel and repair. Here we aimed at developing an amnion-based scaffold suitable for cardiovascular tissue engineering applications and in vivo usage. The developed human amnion-based scaffold was made by an enzymatic decellularization process followed by freeze-drying as a single or multi-layered structure. These structures were compared to native amnion for seeded cell viability and biomechanical properties then tested for in vivo biocompatibility. Our results demonstrated that while native amnion tissue supported little cell growth, the decellularized-amnion allowed cell engraftment and survival. Additionally, preservation of the scaffold by freeze-drying as a single layer, allowed cell engraftment and growth. Multi-layering the freeze-dried amnion-scaffolds resulted in a similar cell growth potential of the single layered construct but superior mechanical strength. The multi-layered construct showed in vitro biocompatibility with endothelial cells, smooth muscle cells, cardiac myocytes, and thymus and cord-blood-derived MSCs. When implanted in a piglet model of left pulmonary artery grafting, the multi-layered construct showed its in vivo suitability and biocompatibility for vascular repair as demonstrated by the development of newly formed endothelium in the intima, a smooth muscle cell-rich medial layer and an adventitia containing new vasa vasorum. In conclusion, our developed amnion-derived scaffold represents an off-the-shelf biocompatible structure that can be seeded with the patient's own MSCs to produce an autologous vascular graft.