Background-Tyrosine kinase inhibitors (TKIs) have advanced cancer treatment. Sunitinib, a recently-approved, multi-targeted TKI, prolongs survival for patients with metastatic renal cell carcinoma (RCC) and gastrointestinal stromal tumor (GIST), but concerns about cardiac safety have arisen with this agent.

Tumor growth is angiogenesis dependent. We hypothesized that nonneoplastic tissue growth also depends on neovascularization. We chose adipose tissue as an experimental system because of its remodeling capacity. Mice from different obesity models received anti-angiogenic agents. Treatment resulted in dose-dependent, reversible weight reduction and adipose tissue loss. Marked vascular remodeling was evident in adipose tissue sections, which revealed decreased endothelial proliferation and increased apoptosis in treated mice compared with controls. Continuous treatment maintained mice near normal body weights for age without adverse effects. Metabolic adaptations in food intake, metabolic rate, and energy substrate utilization were associated with antiangiogenic weight loss. We conclude that adipose tissue mass is sensitive to angiogenesis inhibitors and can be regulated by its vasculature. Substantial evidence has established that tumor growth is angiogenesis-dependent (1). Neovascularization promotes tumor growth (2), whereas angiogenesis inhibition prevents it, and can regress the lesions (3). This raises the question of whether the endothelium functions similarly in nonneoplastic tissue growth (4).The challenges in addressing this question are that most adult tissues normally do not grow, their mass is stable, and the supporting vasculature is quiescent (5). Exceptionally, adipose tissue can grow and regress throughout adulthood. It is highly vascularized and has angiogenic properties (6, 7). An extensive capillary network surrounds each adipocyte, and there are few other resident cell types (8). Therefore, adipose tissue is uniquely suited to study the role of angiogenesis in nonneoplastic adult tissue growth.The potential for adipose tissue to grow and regress is substantial. One would expect the vasculature to have a commensurate capacity for remodeling. We hypothesized that adipose tissue growth is angiogenesis dependent and, therefore, may be inhibited by anti-angiogenesis agents. This would suggest that adipose tissue mass may be regulated via the vascular endothelium.We primarily used ob͞ob mice because they rapidly accumulate adipose tissue (9). This strain develops spontaneous obesity because of a lack of functional leptin, a protein secreted by adipocytes that acts on the hypothalamus to regulate appetite and metabolism (9-11). Without leptin, animals eat excessively, expend less energy, and become morbidly obese. Leptin replacement induces weight loss in ob͞ob mice by specifically reducing adipose tissue (9), unlike diet restriction or appetite suppression (fenfluramine), which decreases both lean and fat mass (12, 13).We treated ob͞ob mice with various angiogenesis inhibitors. We primarily used TNP-470 (14) because of availability. TNP-470 inhibits endothelial cell proliferation in vitro (15) and angiogenesis in vivo (16). At significantly higher concentrations, TNP-470 can also suppress nonendothelial cell proliferation (14,17). Angiostatin (kringle 1-4 domains of plasminogen) (18) and endostatin (...

Abstract-We report that human embryonic stem cells contain a population of vascular progenitor cells that have the ability to differentiate into endothelial-like and smooth muscle (SM)-like cells. Vascular progenitor cells were isolated from EBs grown in suspension for 10 days and were characterized by expression of the endothelial/hematopoietic marker CD34 (CD34 ϩ cells). When these cells are subsequently cultured in EGM-2 (endothelial growth medium) supplemented with vascular endothelial growth factor-165 (50 ng/mL), they give rise to endothelial-like cells characterized by a cobblestone cell morphology, expression of endothelial markers (platelet endothelial cell-adhesion molecule-1, CD34, KDR/Flk-1, vascular endothelial cadherin, von Willebrand factor), incorporation of acetylated low-density lipoprotein, and formation of capillary-like structures when placed in Matrigel. In contrast, when CD34 ϩ cells are cultured in EGM-2 supplemented with platelet-derived growth factor-BB (50 ng/mL), they give rise to SM-like cells characterized by spindle-shape morphology, expression of SM cell markers (␣-SM actin, SM myosin heavy chain, calponin, caldesmon, SM ␣-22), and the ability to contract and relax in response to common pharmacological agents such as carbachol and atropine but rarely form capillary-like structures when placed in Matrigel. Implantation studies in nude mice show that both cell types contribute to the formation of human microvasculature. Some microvessels contained mouse blood cells, which indicates functional integration with host vasculature. Therefore, the vascular progenitors isolated from human embryonic stem cells using methods established in the present study could provide a means to examine the mechanisms of endothelial and SM cell development, and they could also provide a potential source of cells for vascular tissue engineering. [3][4][5] Isolating a population of human progenitor cells with potential for cell number expansion and differentiation into both ECs and SMCs with high efficiency could benefit the area of tissue engineering. 2,5,6 Embryonic stem cells (ESCs) are a potential cell source for induction of tissue vascularization. 7 Prior studies have derived ECs and SMCs cells from a common progenitor (Flk-1 ϩ cells) from mouse 6 and monkey ESCs, 8 but not from human ESCs (hESCs). We previously reported that hESCs can spontaneously generate ECs with definitive properties. 9 These cells were isolated based on the expression of platelet EC-adhesion molecule-1 (PECAM1) from embryoid bodies (EBs) grown in suspension for 13 to 15 days. Using the same endothelial 10 or other (eg, CD34 11,12 ) markers, others have isolated endothelial progenitor cells with the ability to differentiate into mature endothelium. In addition, it has been reported that hESCs can differentiate into mesodermal cells that can give rise to ECs and SMCs 13 ; however, it is not clear that these cells were derived from the same progenitor.Here we report that cells isolated from EBs at day 10 and expressing the hematop...

Abstract-Cardiac myocyte loss, regardless of insult, can trigger compensatory myocardial remodeling leading to heart failure. Identifying mediators of cardiac myocyte survival may advance clinical efforts toward myocardial preservation. Angiopoietin-1 limits ischemia-induced cardiac injury. This benefit is ascribed to angiogenesis because the receptor, tie2, is largely endothelial-specific. We propose that direct, non-tie2 interactions of angiopoietin-1 on cardiac myocytes contribute to this cardioprotection. We found that mouse C2C12 skeletal myocytes lack tie2, yet dose-dependently adhered to angiopoietin-1 and angiopoietin-2 similarly to laminin, fibronectin, vitronectin, and more than to collagen-I, -III, and -IV. Adhesion was divalent cation-mediated (Mn 2ϩ , Ca 2ϩ , not Mg 2ϩ ), blocked with EDTA/EGTA, RGD-based peptides, and select integrin subunit antibodies. Similar findings were obtained with human skeletal myocytes (HSMs) and freshly isolated rat neonatal cardiac myocytes (NCMs). Furthermore, angiopoietin-1 conferred significant survival advantage exceeding that of most cell matrices, which was not fully explained by differences in cell adhesion. Angiopoietin-1 promoted survival of serum-starved C2C12, HSM, and NCM (MTT, trypan blue) and prevented taxol-induced apoptosis (caspase-3). Immobilized and soluble angiopoietin-1 phosphorylated Akt S473 and MAPK p42/44 , (not FAK Y397 ) in C2C12 more than in endothelial cells and more than did angiopoietin-2 or cell matrices. EDTA, RGD-based peptides, and some integrin antibodies blocked these responses. Angiopoietin-1 activated HSM and NCM Akt S473 and MAPK p42/44 survival pathways. We propose that this novel function contributes to developmental and cardioprotective actions of angiopoietin-1 presently attributed to vascular effects alone. Angiopoietin-1 may prove therapeutically valuable in cardiac remodeling by supporting myocyte viability and preserving pump function. The full text of this article is available online at http://circres.ahajournals.org. (Circ Res. 2005;96:e8-e24.)Key Words: angiopoietin-1 Ⅲ angiopoietin-2 Ⅲ cardiac myocytes Ⅲ adhesion molecules Ⅲ myocyte apoptosis Ⅲ skeletal myocytes T here is growing consensus that cardiomyocyte (CM) apoptosis contributes to many cardiac diseases (eg, ischemia, 1 infarction, 2 hypertension, 3 myocarditis, 4 transplant rejection, 5 and heart failure 6,7 ). Research efforts are directed at defining the incidence of CM death, the contributions to cardiac dysfunction, and the consequences of inhibiting apoptosis. Incentive is based on the rationale that CM loss reduces contractile mass of the heart and may be a preventable catalyst of heart failure. In support of this concept, low levels of CM apoptosis (23 CM/10 5 nuclei) cause lethal cardiomyopathy in mice. 8 CM apoptosis rates are higher in cardiomyopathy patients (80 to 250 CM/10 5 nuclei) compared with healthy hearts (1 to 10 CM/10 5 nuclei). 9,10 Further, ischemic preconditioning upregulates bcl-2, a cytoprotective protein, and is linked to reduced apop...