The anti-apoptotic effect of IGF-1 on tissue resident stem cells is mediated via PI3-kinase dependent secreted frizzled related protein 2 (Sfrp2) release.

Previous studies suggest that IGF-1 may be used as an adjuvant to stem cell transfer in order to improve cell engraftment in ischemic tissue. In the current study, we investigated the effect of IGF-1 on serum deprivation and hypoxia induced stem cell apoptosis and the possible mechanisms involved. Exposure of adipose tissue derived stem cells (ASCs) to serum deprivation and hypoxia resulted in significant apoptosis in ASC which is partially prevented by IGF-1. IGF-1's anti-apoptotic effect was abolished in ASCs transfected with Sfrp2 siRNA but not by the control siRNA. Using Western blot analysis, we demonstrated that serum deprivation and hypoxia reduced the expression of nuclear beta-catenin, which is reversed by IGF-1. IGF-1's effect on beta-catenin expression was abolished by the presence of PI3-kinase inhibitor LY294002 or in ASCs transfected with Sfrp2 siRNA. These results suggest that IGF-1, through the release of the Sfrp2, contributes to cell survival by stabilizing beta-catenin.

Intracoronary administration of autologous adipose tissue-derived stem cells improves left ventricular function, perfusion, and remodelling after acute myocardial infarction.

AIMS: This study was designed to assess whether intracoronary application of adipose tissue-derived stem cells (ADSCs) compared with bone marrow-derived stem cells (BMSCs) and control could improve cardiac function after 30 days in a porcine acute myocardial infarction/reperfusion model. METHODS AND RESULTS: An acute transmural porcine myocardial infarction was induced by inflating an angioplasty balloon for 180 min in the mid-left anterior descending artery. Two million cultured autologous stem cells were intracoronary injected through the central lumen of the inflated balloon catheter. Analysis of scintigraphic data obtained after 28 +/- 3 days showed that both absolute and relative perfusion defect decreased significantly after intracoronary administration of ADSCs or BMSCs (relative 30 or 31%, respectively), compared with carrier administration alone (12%, P = 0.048). Left ventricular ejection fraction after 4 weeks increased significantly more after ADSC and BMSC administration than after carrier administration: 11.39 +/- 4.62 and 9.59 +/- 7.95%, respectively vs. 1.95 +/- 4.7%, P = 0.02). The relative thickness of the ventricular wall in the infarction area after cell administration was significantly greater than that after carrier administration. The vascular density of the border zone also improved. The grafted cells co-localized with von Willebrand factor and alpha-smooth muscle actin and incorporated into newly formed vessels. CONCLUSION: This is the first study to show that not only bone marrow-derived cells but also ADSCs engrafted in the infarct region 4 weeks after intracoronary cell transplantation and improved cardiac function and perfusion via angiogenesis.

The cardioprotective effect of mesenchymal stem cells is mediated by IGF-I and VEGF.

Emerging evidence suggests that adipose tissue-derived stem cells (ASCs) can be used for the treatment of ischemic heart diseases. However, the mechanisms underlying their therapeutic effects have not been clearly defined. In this study cytokines released by ASCs were detected by ELISA and pro-angiogenic effects were assessed by tube formation assay. To define the anti-apoptotic effect of ASCs, neonatal rat cardiomyocytes were subjected to hypoxia condition in a co-culture system. Our data show that ASCs secrete significant amounts of VEGF (810.65+/-56.92 pg/microg DNA) and IGF-I (328.33+/-22.7 pg/microg DNA). Cardiomyocytes apoptosis was significantly prevented by ASCs and 62.5% of the anti-apoptotic effect was mediated by IGF-I and 34.2% by VEGF. ASCs promoted endothelial cell tube formation by secreting VEGF. In conclusion we demonstrated that ASCs have a marked impact on anti-apoptosis and angiogenesis and helps to explain data of stem cells benefit without transdifferentiation.

VEGF receptor Flk-1 plays an important role in c-kit expression in adipose tissue derived stem cells.

It is known that c-kit(+) cells are increased in heart after infarction. The exact origins of the cardiac c-kit(+) cells remain to be determined. We asked whether adipose tissue could be a potential source of c-kit(+) cells. Our data show that the number of c-kit(+) cells increased in adipose tissue derived stem cells when cultured with conditioned medium from neonatal cardiomyocytes grown under serum deprivation and hypoxia condition. We also found that VEGF receptor Flk-1 is involved in c-kit up regulation via ERK-mediated pathway.

VEGF is critical for spontaneous differentiation of stem cells into cardiomyocytes.

Cardiomyocyte regeneration is limited in adult life and is not sufficient to compensate for cell loss with myocardial infarction. Hence, the identification of a useful source of cardiomyocyte progenitors is of great interest for possible use in regenerative therapy. In this study, we isolated stem cells derived from human subcutaneous adipose tissue. The expression of Nkx2.5 and GATA-4 can be observed by PCR directly after extraction and during cultivation in some of these cells. Cardiac Troponin T and myosin light chain-2v become positive after 12 days of cultivation. To define respective factors responsible for spontaneous differentiation, we measured VEGF level in ADSC conditioned medium. Our data showed that ADSC secrete significant amount of VEGF (283.5pg per microgram DNA) and that anti-VEGF receptor antibodies blocked the cardiac differentiation. In conclusion, we demonstrated the spontaneous differentiation of human subcutaneous adipose-derived stem cells into a cardiomyocyte phenotype under standard culturing conditions.