Development of Two Steps Tissue Allograft with Sequential Growth Factor Delivery to Promote Revascularization in Denudated Pneumonectomy Bronchial Stump

Devascularization due to large lymph node dissection is one of the causative factors of bronchial stump fistula (BF). In this work we have developed and analyzed the utility of a tissue allograft composed of alginate polymer (AP), autologous fibrin (AF), tissue-engineered fibroblasts (TEF), vascular endotelial growth factor (VEGF) and encapsulated fibroblast growth factor (FGF) to prevent BF and promote revascularization of the bronchial stump in a pig pneumonectomy model. To validate the system a left pneumonectomy was performed in 15 pigs, leaving a long and exhaustively devascularized bronchial stump. The animals were allocated in groups of five to receive no bronchial stump coverage (group A), coverage with AP + AF only (group B) or coverage with AP + AF + TEF + VEGF + FGF (group C). After being euthanized on postoperative days 3,7, 14 , 21 and 30, bronchial stumps for each group were tested for BF occurrence and subsequently sectioned for histology and stained with hematoxylin-eosin, CD-31 and α-smooth muscle actin antibodies to evaluate blood vessels formation and maturation, capillary density and TEF proliferation by means of a semiquantitative method.

From the analysis done it can be concluded that: No BF could be detected for any group, probably due to a high spontaneous healing capacity of pig tissues. In group A, fibroblastic proliferation and revascularization were scarce; group B showed some immature neovessels besides a moderate TEF proliferation while in group C, in addition to an intense TEF proliferation, a large number of vascular yolks could be detected on postoperative day 7, continuing to complete vascular structures on postoperative day 14 within a highly dense capillary network. Therefore, the avascular scaffold highly promotes revascularization of the denudated bronchial stump. Further studies are being done to clarify the clinical application of these findings.