Jason E. Bovenkerk

Secretion of Angiogenic and Antiapoptotic Factors by Human Adipose Stromal Cells

Background—The delivery of autologous cells to increase angiogenesis is emerging as a treatment option for patients with cardiovascular disease but may be limited by the accessibility of sufficient cell numbers. The beneficial effects of delivered cells appear to be related to their pluripotency and ability to secrete growth factors. We examined nonadipocyte stromal cells from human subcutaneous fat as a novel source of therapeutic cells. Methods and Results—Adipose stromal cells (ASCs) were isolated from human subcutaneous adipose tissue and characterized by flow cytometry. ASCs secreted 1203±254 pg of vascular endothelial growth factor (VEGF) per 106 cells, 12 280±2944 pg of hepatocyte growth factor per 106 cells, and 1247±346 pg of transforming growth factor-&bgr; per 106 cells. When ASCs were cultured in hypoxic conditions, VEGF secretion increased 5-fold to 5980±1066 pg/106 cells (P =0.0016). The secretion of VEGF could also be augmented 200-fold by transfection of ASCs with a plasmid encoding VEGF (P <0.05). Conditioned media obtained from hypoxic ASCs significantly increased endothelial cell growth (P <0.001) and reduced endothelial cell apoptosis (P <0.05). Nude mice with ischemic hindlimbs demonstrated marked perfusion improvement when treated with human ASCs (P <0.05). Conclusions—Our experiments delineate the angiogenic and antiapoptotic potential of easily accessible subcutaneous adipose stromal cells by demonstrating the secretion of multiple potentially synergistic proangiogenic growth factors. These findings suggest that autologous delivery of either native or transduced subcutaneous ASCs, which are regulated by hypoxia, may be a novel therapeutic option to enhance angiogenesis or achieve cardiovascular protection.

Obesity is associated with increased levels of circulating hepatocyte growth factor

OBJECTIVES This study evaluated whether obesity in humans was associated with an increase in circulating hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) levels. BACKGROUND Obesity acts as a cardiovascular risk factor by mechanisms that are not fully understood. Adipose tissue is able to secrete multiple cytokines and growth factors ex vivo. We hypothesized that the increased presence of adipose tissue in obese subjects results in systemic elevations of the mitogenic factors HGF and VEGF. METHODS Blood samples were obtained from lean (n = 21) and obese (n = 44) volunteers. Serum HGF and VEGF levels were assessed by enzyme-linked immunoadsorbent assay. Insulin and fasting glucose levels were measured to evaluate insulin sensitivity. Conditioned medium of adipose cells was assayed for HGF secretion. RESULTS Serum HGF levels in obese subjects were more than three-fold higher than those of lean subjects (2,462 +/- 184 pg/ml vs. 765 +/- 48 pg/ml, p < 0.0001). The VEGF levels were not significantly elevated in obese subjects (135 +/- 31 pg/ml vs. 128 +/- 37 pg/ml). The HGF concentrations, but not VEGF concentrations, were significantly correlated with body mass index (BMI) (p < 0.0001, r = 0.74). The observed increases in HGF concentrations of obese subjects were not secondary to insulin resistance or hypertension. Freshly isolated human adipose cells secreted HGF. CONCLUSIONS Our results indicate that obesity is associated with a marked increase in circulating HGF levels, which correlate linearly with BMI. Because vascular growth factors have been associated with the pathogenesis of atherosclerosis, the possible role of such humoral factors as a link between obesity and cardiovascular disease is very intriguing.