Tissue Engineered Trachea: morfologic features of biocompatibility and neoangiogenesis in an animal model

We evaluated a new designed bioresorbable polymer (Degrapol®) tracheal prosthesis in an in‐vivo angiogenesis‐inducing animal model focusing on the specific tissue reaction, the neo‐angiogenesis throughout the prosthesis wall and also the eventual Cathepsin B role during the polymer degradation. Our prosthesis was made by a tube‐shaped electrospun porous scaffold (6/25 μm Ø fibers, 30/80 μm inter‐fibre space). Fifteen rabbits were divided in three groups (2, 6, 8 weeks). The prosthesis was implanted using the common carotid artery and the internal jugular vein as vascular pedicle. Optical and electron microscopy, immunohistochemestry and immunocitochemestry were performed at the end of each period. The microscopical observations showed cells and fibrils strongly increased with time. After 8 weeks the external surface was completely concealed and blood vessel neoformation was visible. As cells migrated centripetally filling pores of the scaffold, small muscle fibers and endothelial cells defining capillary structure were visible. The expression of CD31 was localized at the endothelial cells forming the blood vessel walls. Over time many of them differentiate in muscle fibres as validate by the expression of α‐smooth muscle actin. Few inflammatory cells expressing CD14 were visible while most cells with a clear spreading phenotype showed a strong positivity for Cathepsin B. Our results demonstrate that this bioresorbable polymer provided a good substrate for fibrous tissue deposition with an excellent degree of neo‐angiogenesis. Also Cathepsin B seems to contribute to the polymer degradation and particularly to neovascularization by stimulating capillary‐like tubular structures and cell proliferation.