Following myocardial infarction (MI), the degradation of cardiac extracellular matrix (ECM) mainly by upregulated matrix metalloproteinase-2/9 (MMP-2/9), and the progression of cardiac fibrosis after myofibroblast formation, progressively deteriorate cardiac function. As such, impeding MMP-2/9 bioactivity, and inhibiting myofibroblast formation will improve cardiac function. However, the ideal therapeutic strategies to simultaneously achieve both goals remain to be established. Currently, systemic delivery of broad spectrum MMP inhibitors did not show consistent outcomes in clinical trials. MMP-2/9 expression is spatiotemporal in infarcted hearts over the course of post-MI. Yet current systemic delivery approach cannot spatiotemporally deliver MMP inhibitors to the infarcted area. To attenuate cardiac fibrosis, systemic delivery of TGF? inhibitors or anti-TGF? antibodies represents a major approach. However, it only decreases the content of active TGF?. It cannot inhibit TGF? signaling pathway to prevent myofibroblast formation. Furthermore, the small organic MMP and TGF? inhibitors have toxicity concerns. The objective of this project is to create drug delivery systems that can be specifically delivered into infarcted hearts to concurrently preserve cardiac ECM, and prevent cardiac fibrosis. Localized delivery will eliminate dose-limiting side effects. The systems will spatiotemporally release MMP-2/9 specific and non-toxic inhibitor, peptide CTTHWGFTLC (CTT), to specifically modulate local MMP-2/9 bioactivity. The systems will also gradually release a multifunctional growth factor bFGF that have anti-fibrotic and proangiogenesis functions. The preserved ECM will thus be vascularized. Vascularization is critical for cardiac ECM as otherwise its structure and composition change over time. In our preliminary work, we have created a fast gelation and degradable hydrogel-based release system capable of efficiently retaining drugs in beating hearts. The system can release CTT for 4 weeks. After being injected into infarcted hearts, the released CTT preserved collagen, increased tissue thickness, and improved cardiac function. Better than many other small organic MMP inhibitors, CTT did not induce cardiac fibrosis. Besides, CTT promoted endothelial cell migration in the presence of TGF? that is upregulated after MI. These results demonstrate that CTT is potentially a better MMP inhibitor for cardiac therapy than those small organic inhibitors. We have further created a release system that continuously releases both CTT and bFGF. bFGF is known for its angiogenic effect. We found that bFGF is capable of inhibiting TGF?-induced cardiac fibroblast differentiation into myofibroblast through TGF?/Erk1/2 pathway. After 4 weeks of implantation, the CTT/bFGF release systems not only increased tissue thickness and preserved collagen composition, but also promoted the formation of a high density of capillaries and remarkably reduced cardiac fibrosis, leading to the increase of cardiac function. Based on our preliminary studies, we hypothesize that localized and spatiotemporal delivery of CTT and bFGF into infarcted hearts, will concurrently attenuate cardiac ECM degradation, vascularize the preserved ECM, and prevent cardiac fibrosis, leading to a significant increase in cardiac function.
AIM 1 will test the hypothesis that optimal CTT release profiles will efficiently attenuate MMP-2 bioactivity to prevent MMP-2 mediated ECM degradation.
AIM 2 will test the hypothesis that optimal bFGF release profiles will simultaneously promote endothelial cell morphogenesis and prevent cardiac fibroblasts from differentiating into myofibroblasts.
AIM 3 will test the hypothesis that delivery of CTT and bFGF release systems after MI will concurrently preserve and vascularize cardiac ECM, and prevent cardiac fibrosis. This project is innovative because it creates translational drug delivery systems to establish: 1) role and efficacy of an efficient MMP-2/MMP-9 inhibitor CTT in cardiac therapy; 2) mechanism and efficacy of bFGF in inhibiting cardiac fibrosis while promoting angiogenesis; and 3) how sustained release of CTT and bFGF simultaneously achieves these three goals. The system is relatively simple and multifunctional. Therefore, it is translational.
Adverse cardiac remodeling after myocardial infarction leads to a progressive decrease in cardiac function. Yet the ideal therapeutic strategies remain to be established. Accomplishment of the proposed research will create novel drug delivery systems to attenuate adverse cardiac remodeling by preserving and vascularizing cardiac extracellular matrix and inhibiting cardiac fibrosis.
