Stem cell therapy for the prevention and treatment of cardiac dysfunction holds significant promise for patients with ischemic heart disease. Excitingly early clinical studies have demonstrated safety and some clinical feasibility, while at the same time studies in the laboratory have investigated mechanisms of action and strategies to optimize the effects of regenerative cardiac therapies. One of the key pathways that has been demonstrated critical in stem cell-based cardiac repair is (stromal cell-derived factor-1) SDF-1:CXCR4. SDF-1:CXCR4 has been shown to affect stem cell homing, cardiac myocyte survival and ventricular remodeling in animal studies of acute myocardial infarction and chronic heart failure. Recently released clinical data suggest that SDF-1 alone is sufficient to induce cardiac repair. Most importantly, studies like those on the SDF-1:CXCR4 axis have suggested mechanisms critical for cardiac regenerative therapies that if clinical investigators continue to ignore will result in poorly designed studies that will continue to yield negative results. Gene Therapy (2012) 19, 583-587; doi:10.1038/gt.2012.32Keywords: acute myocordial infarction; regenerative medicine; stem cells; chemokines
INTRODUCTIONOver a decade ago we hypothesized that stem cell-based repair of ischemic tissue is a natural response to tissue injury but that it is clinically inefficient because of the short-lived nature of the molecular signals regulating the process, not a lack of stem cells. At that time it was of great interest to us that stem cells in the blood stream homed to the myocardium in animal models of acute myocardial infarction (AMI), but not in models of chronic ischemic cardiomyopathy. These observations led us to investigate potential regulators of stem cell homing. We eventually identified stromal cell-derived factor-1 (SDF-1, aka CXCL12) as the key regulator of stem cell migration to sites of tissue injury. 1 More recently studies have extended the relevance of the SDF-1:CXCR4 axis by demonstrating its critical importance in cardiogenic specification during development. 2 As that initial observation we have demonstrated that transient engineered-cell-based 3 or plasmid-based 4 overexpression of SDF-1 in ischemic cardiomyopathy improved cardiac function. Furthermore, we have demonstrated that delivery of mesenchymal stem cells engineered to overexpress SDF-1 at the time of AMI leads to improvement in cardiac function. 5 Research by our laboratory and others have demonstrated that mechanism of action of SDF-1 overexpression in AMI and chronic heart failure (CHF) are clearly multifactorial including both systemic and direct trophic effects. [4][5][6] The initiation of endogenous stem cell-based repair appears blunted because of the natural short-term expression of SDF-1 at the time of AMI. 1 Furthermore, there appears to be commonalities associated with the mechanisms of action of SDF-1 in AMI and CHF as well as some distinct differences. We were the first to show that SDF-1 leads to the recruitment of cardiac st...