The role of bFGF in down-regulating α-SMA expression of chondrogenically induced BMSCs and preventing the shrinkage of BMSC engineered cartilage

Bone marrow stromal cells (BMSCs) have proved to be an ideal cell source for cartilage regeneration. Our previous studies demonstrated that a three-dimensional (3D) cartilage could be constructed successfully in vitro using BMSCs and biodegradable scaffolds. However, an obvious shrinkage and deformation was observed during in vitro chondrogenic induction. According to the literatures, it can be speculated that the up-regulation of smooth muscle actin-alpha (α-SMA) caused by transforming growth factor beta (TGFβ) is one of the leading reasons and that basic fibroblast growth factor (bFGF) could antagonize the role of TGFβ to down-regulate α-SMA expression and prevent the shrinkage of BMSC engineered cartilage. This study testified these speculations by adding bFGF to chondrogenic media. According to the current results, chondrogenic induction significantly up-regulated α-SMA expression of BMSCs at both cell and tissue levels, and the engineered tissue only retained 12.4% of original size after 6 weeks of chondrogenic induction. However, the supplement of bFGF in chondrogenic media efficiently down-regulated α-SMA expression and the engineered tissue still retained over 60% of original size after 6 weeks of culture. Moreover, bFGF showed a beneficial influence on 3D cartilage formation of BMSCs in terms of gene expression and deposition of cartilage specific matrices. All these results suggested that bFGF could repress α-SMA expression caused by chondrogenic induction, efficiently prevent shrinkage of BMSC engineered tissue, and have a positive influence on cartilage formation, which provides a clue for both shape control and quality improvement of BMSC engineered 3D cartilage.