CTGF-D4 Amplifies LRP6 Signaling to Promote Grafts of Adult Epicardial-derived Cells That Improve Cardiac Function After Myocardial Infarction.

Transplantation of stem/progenitor cells holds promise for cardiac regeneration in patients with myocardial infarction (MI). Currently, however, low cell survival and engraftment after transplantation present a major barrier to many forms of cell therapy. One issue is that ligands, receptors, and signaling pathways that promote graft success remain poorly understood. Here, we prospectively isolate uncommitted epicardial cells from the adult heart surface by CD104 (ß-4 integrin) and demonstrate that C-terminal peptide from connective tissue growth factor (CTGF-D4), when combined with insulin, effectively primes epicardial-derived cells (EPDC) for cardiac engraftment after MI. Similar to native epicardial derivatives that arise from epicardial EMT at the heart surface, the grafted cells migrated into injured myocardial tissue in a rat model of MI with reperfusion. By echocardiography, at 1 month after MI, we observed significant improvement in cardiac function for animals that received epicardial cells primed with CTGF-D4/insulin compared with those that received vehicle-primed (control) cells. In the presence of insulin, CTGF-D4 treatment significantly increased the phosphorylation of Wnt co-receptor LRP6 on EPDC. Competitive engraftment assays and neutralizing/blocking studies showed that LRP6 was required for EPDC engraftment after transplantation. Our results identify LRP6 as a key target for increasing EPDC engraftment after MI and suggest amplification of LRP6 signaling with CTGF-D4/insulin, or by other means, may provide an effective approach for achieving successful cellular grafts in regenerative medicine.

Absence of altered autophagy after myocardial ischemia in diabetic compared with nondiabetic mice.

OBJECTIVES: The extent of autophagy in myocardium following persistent ischemia and the effects of insulin resistance and diabetes on cardiac autophagy following myocardial infarction (MI) have not been well elucidated. It is generally thought that autophagy reflects the nutritional status of cells, presumably alterable by diabetes. It has been conjectured that diminution of autophagy early after the onset of MI may preserve jeopardized myocardium thereby improving prognosis. METHODS: Ten-week-old nondiabetic C57BL6 mice, 20-week-old diabetic and nondiabetic C57BL6 mice were subjected to MI for 4 weeks. Hearts from these mice were harvested and assayed for markers of autophagy. RESULT: Hearts of 10-week-old C57BL6 mice subjected to 4 weeks of MI had similar levels of LC3-II, a protein indicator of autophagy, as measured by western blotting compared with hearts from sham operated controls. In 20-week-old C57BL6 mice rendered diabetic by feeding a high-fat diet, the amounts of autophagy were comparable to those in 20-week-old nondiabetic C57BL6 mice on a normal diet. CONCLUSION: The magnitude of autophagy in the heart after infarction is of very modest extent and is not modulated by diabetes. Thus, diminution of autophagy is not likely to reduce infarct size or attenuate late negative remodeling after MI in patients with diabetes.