Abstract: BACKGROUND: As one of the effective angiogenic factors, basic fibroblast growth factor can not only increase the blood perfusion of ischemic tissues and accelerate the regeneration of tissue microvessels, but also improve the formation of blood vessels in muscle tissues and increase the blood perfusion of muscles. 
OBJECTIVE: Basic fibroblast growth factor was incorporated into poly(lactic acid)/collagen scaffold to repair rabbit urethral defects and to improve the ability of tissue engineered scaffolds to induce urethral regeneration. 
METHODS: The electrospun poly(lactic acid)/collagen urethral scaffold and the electrospun poly(lactic acid)/collagen scaffold loaded with basic fibroblast growth factor were prepared and named as control scaffold and experimental scaffold, respectively. The in vitro release properties of the scaffolds were tested. The third passage of rabbit adipose derived mesenchymal stem cells was seeded on the two scaffolds for 7 days. CCK-8 assay, cell adhesion test, and cell live-dead staining were performed respectively. Twenty-four adult male New Zealand white rabbits were used to establish a 5 cm long urethral defect model and randomly divided into two groups (n=12). The control scaffold + adipose derived mesenchymal stem cell complex and the experimental scaffold + adipose derived mesenchymal stem cell complex were implanted, respectively. At 12 and 24 weeks after operation, retrograde urethrography and histology were performed.
RESULTS AND CONCLUSION: (1) In vitro sustained release experiment: Basic fibroblast growth factor was released at an average rate of 2.5 ng/d in the first 6 days, 1.52 ng/d from the seventh to fourteenth days, and 1.12 ng/d thereafter. The release rate gradually decreased after 21 days. (2) In vitro cell experiments showed that the cell proliferation rate on the experimental scaffold was faster than that on the control scaffold (P < 0.05). Adipose-derived mesenchymal stem cells could adhere to the surfaces of the two scaffolds, grow well and protrude pseudopodia, among which the cells on the experimental scaffold proliferated rapidly. The survival rate of the cells on the experimental scaffolds was higher than that of the control scaffold (P < 0.05). (3) In vivo experimental results: At 24 weeks postoperatively, urethral angiography exhibited that there was no urethral stricture in the experimental scaffold group, and mild urethral stricture was seen in the control scaffold group. Histological observation demonstrated that at 24 weeks after operation, there was a thick and complete epithelial layer in the experimental scaffold group, with a large number of muscle fiber bundles and blood vessels. In the control scaffold group, there was a thin epithelial layer, with a small number of muscle fiber bundles and blood vessels. (4) The results confirm that electrospun poly(lactic acid)/collagen scaffold loaded with basic fibroblast growth factor for repairing rabbit urethral defects could promote local angiogenesis, improve local urethral microenvironment and promote urethral regeneration.basic fibroblast growth factor; poly(lactic acid); collagen; scaffold; urethral defect; urethral regeneration; tissue engineering

Key words: basic fibroblast growth factor, poly(lactic acid), collagen, scaffold, urethral defect, urethral regeneration, tissue engineering