An injectable and thermosensitive hydrogel capable of delivering basic fibroblast growth factor to control cardiac fibrosis

摘要

Introduction: Myocardial infarction (MI) affects millions of people in the Western countries. Cardiac fibrosis naturally occurs after MI and progresses with time. The increase of cardiac fibrosis leads to gradual decrease of cardiac function. Myofibroblasts, differentiated from cardiac fibroblasts mainly through TGFp signaling pathway, are responsible for cardiac fibrosis. Therefore, to inhibit cardiac fibrosis, It is essential to prevent TGFβ pathway-induced myofibroblast formation. However, ideal therapeutic approaches to achieve this goal remain to be established. We hypothesized that controlled release of anti-fibrotic agent basic fibroblast growth factor (bFGF) will efficiently inhibit myofibroblast formation. bFGF has been shown to prevent myofibroblast activation in various tissues. It counteracts the profibrotic activity of TGFβ. In this study, we tested whether controlled release of bFGF from a thermosentivie hydrogel can efficiently inhibit cardiac fibroblasts from differentiating into myofibroblasts. Materials and Methods: The injectable and thermosensitive hydrogel was synthesized to serve as bFGF carrier. The hydrogel was based on N-isopropylacrylamide, acrylate-polylactide, and 2-hydroxyethyl methacrylate, and synthesized through free radical polymerization. Hydrogel sol-gel transition temperature was measured using DSC. The injectability of the hydrogel solution was tested by injecting a 20% hydrogel solution through a 26 gauge needle at 4°C. bFGF was encapsulated in the 4% hydrogel solution. The release study was conducted at 37°C using PBS as release medium for 28 days. To test the effect of bFGF release on cardiac fibroblast differentiation into myofibroblast, the bFGF encapsulated hydrogel was injected into 3D collagen gel seeded with rat cardiac fibroblasts (RCF) and cultured in the presence of TGFp. Cell phenotype was characterized at the protein level by immunohistochemistry (IHC), and at the gene level by real-time RT-PCR. Results and Discussion: The thermosentive hydrogel had a sol-gel transition temperature -26°C. The hydrogel solution (20%, w/v) can be readily injected through a 26 gauge needle at 4°C. The bFGF was able to continuously release from the hydrogel during a 23-day period. The released bFGF remained bioactive as it promoted RCF proliferation. The release kinetics was dependent on bFGF loading. A higher bFGF loading released greater amount of bFGF. The released bFGF remarkably attenuated myofibroblast differentiation. At the mRNA level, the group injected with hydrogel and bFGF had significant lower expression of myofibroblast markers aSMA and CTGF. At the protein level, the density of aSMA positive myofibroblasts was significantly decreased compared to the control group that injected with hydrogel only. Conclusions: An injectable hydrogel-based bFGF release system was developed to inhibit cardiac fibroblasts from differentiation into myofibroblasts. The results demonstrated that this system has potential to control cardiac fibrosis after MI.