Improved myocardial performance in infarcted rat heart by injection of disulfide-cross-linked chitosan hydrogels loaded with basic fibroblast growth factor

Myocardial infarction (MI) has been considered as the leading cause of cardiovascular-related deaths worldwide. Basic fibroblast growth factor (bFGF) is a member of the fibroblast growth factor family that promotes angiogenesis after MI; however, it has poor clinical efficacy due to proteolytic degradation, low drug accumulation, and severe drug-induced side effects. In this study, an injectable disulfide-cross-linked chitosan hydrogel loaded with bFGF was prepared via a thiol-disulfide exchange reaction for MI treatment. The thiol-disulfide exchange reaction between pyridyl disulfide-modified carboxymethyl chitosan (CMCS-S-S-Py) and reduced BSA (rBSA) was carried out under physiological conditions (37 degrees C and pH 7.4). The mechanical properties of the disulfide-cross-linked chitosan hydrogel were evaluated based on the molar ratio of the pyridyl disulfide groups of CMCS-S-S-Py and the thiol groups of rBSA. The disulfide-cross-linked chitosan hydrogel showed good swelling performance, rapid glutathione-triggered degradation behavior and well-defined cell proliferation towards NIH 3T3 fibroblast cells. In the process of establishing a rat MI model, the squeezing heart method was used to make the operation more accurate and the mortality of rats was decreased by using a ventilator. The disulfide-cross-linked chitosan hydrogel loaded with bFGF (bFGF-hydrogel) was injected into a peri-infarcted area of cardiac tissue immediately following MI. Echocardiography demonstrated that the left ventricular functions were improved by the bFGF-hydrogel after 28 days of treatment. Histological results revealed that the hydrogel significantly reduced the fibrotic area of MI, and this was further improved by the bFGF-hydrogel treatment. TUNEL and immunohistochemical staining results showed that the bFGF-hydrogel had a more synergistic effect on antiapoptosis and proangiogenesis than using either bFGF or the hydrogel alone.