Omaida C. Velazquez

Diabetic impairments in NO-mediated endothelial progenitor cell mobilization and homing are reversed by hyperoxia and SDF-1α

Endothelial progenitor cells (EPCs) are essential in vasculogenesis and wound healing, but their circulating and wound level numbers are decreased in diabetes. This study aimed to determine mechanisms responsible for the diabetic defect in circulating and wound EPCs. Since mobilization of BM EPCs occurs via eNOS activation, we hypothesized that eNOS activation is impaired in diabetes, which results in reduced EPC mobilization. Since hyperoxia activates NOS in other tissues, we investigated whether hyperoxia restores EPC mobilization in diabetic mice through BM NOS activation. Additionally, we studied the hypothesis that impaired EPC homing in diabetes is due to decreased wound level stromal cell-derived factor-1alpha (SDF-1alpha), a chemokine that mediates EPC recruitment in ischemia. Diabetic mice showed impaired phosphorylation of BM eNOS, decreased circulating EPCs, and diminished SDF-1alpha expression in cutaneous wounds. Hyperoxia increased BM NO and circulating EPCs, effects inhibited by the NOS inhibitor N-nitro-L-arginine-methyl ester. Administration of SDF-1alpha into wounds reversed the EPC homing impairment and, with hyperoxia, synergistically enhanced EPC mobilization, homing, and wound healing. Thus, hyperoxia reversed the diabetic defect in EPC mobilization, and SDF-1alpha reversed the diabetic defect in EPC homing. The targets identified, which we believe to be novel, can significantly advance the field of diabetic wound healing.

Regulation of Notch1 and Dll4 by Vascular Endothelial Growth Factor in Arterial Endothelial Cells: Implications for Modulating Arteriogenesis and Angiogenesis

ABSTRACT Notch and its ligands play critical roles in cell fate determination. Expression of Notch and ligand in vascular endothelium and defects in vascular phenotypes of targeted mutants in the Notch pathway have suggested a critical role for Notch signaling in vasculogenesis and angiogenesis. However, the angiogenic signaling that controls Notch and ligand gene expression is unknown. We show here that vascular endothelial growth factor (VEGF) but not basic fibroblast growth factor can induce gene expression of Notch1 and its ligand, Delta-like 4 (Dll4), in human arterial endothelial cells. The VEGF-induced specific signaling is mediated through VEGF receptors 1 and 2 and is transmitted via the phosphatidylinositol 3-kinase/Akt pathway but is independent of mitogen-activated protein kinase and Src tyrosine kinase. Constitutive activation of Notch signaling stabilizes network formation of endothelial cells on Matrigel and enhances formation of vessel-like structures in a three-dimensional angiogenesis model, whereas blocking Notch signaling can partially inhibit network formation. This study provides the first evidence for regulation of Notch/Delta gene expression by an angiogenic growth factor and insight into the critical role of Notch signaling in arteriogenesis and angiogenesis.

Trafficking and differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a heterogeneous population of stem/progenitor cells with pluripotent capacity to differentiate into mesodermal and non‐mesodermal cell lineages, including osteocytes, adipocytes, chondrocytes, myocytes, cardiomyocytes, fibroblasts, myofibroblasts, epithelial cells, and neurons. MSCs reside primarily in the bone marrow, but also exist in other sites such as adipose tissue, peripheral blood, cord blood, liver, and fetal tissues. When stimulated by specific signals, these cells can be released from their niche in the bone marrow into circulation and recruited to the target tissues where they undergo in situ differentiation and contribute to tissue regeneration and homeostasis. Several characteristics of MSCs, such as the potential to differentiate into multiple lineages and the ability to be expanded ex vivo while retaining their original lineage differentiation commitment, make these cells very interesting targets for potential therapeutic use in regenerative medicine and tissue engineering. The feasibility for transplantation of primary or engineered MSCs as cell‐based therapy has been demonstrated. In this review, we summarize the current knowledge on the signals that control trafficking and differentiation of MSCs. J. Cell. Biochem. 106: 984–991, 2009.

Vascular Complications After Transcatheter Aortic Valve Replacement Insights From the PARTNER (Placement of AoRTic TraNscathetER Valve) Trial

OBJECTIVES This study sought to identify incidence, predictors, and impact of vascular complications (VC) after transfemoral (TF) transcatheter aortic valve replacement (TAVR). BACKGROUND VC after TF-TAVR are frequent and may be associated with unfavorable prognosis. METHODS From the randomized controlled PARTNER (Placement of AoRTic TraNscathetER Valve) trial, a total of 419 patients (177 from cohort B [inoperable] and 242 from cohort A [operable high-risk]) were randomly assigned to TF-TAVR and actually received the designated treatment. First-generation Edwards-Sapien valves and delivery systems were used, via a 22- or 24-F sheath. The 30-day rates of major and minor VC (modified Valve Academic Research Consortium definitions), predictors, and effect on 1-year mortality were assessed. RESULTS Sixty-four patients (15.3%) had major VC and 50 patients (11.9%) had minor VC within 30 days of the procedure. Among patients with major VC, vascular dissection (62.8%), perforation (31.3%), and access-site hematoma (22.9%) were the most frequent modes of presentation. Major VC, but not minor VC, were associated with significantly higher 30-day rates of major bleeding, transfusions, and renal failure requiring dialysis, and with a significantly higher rate of 30-day and 1-year mortality. The only identifiable independent predictor of major VC was female gender (hazard ratio [HR]: 2.31 [95% confidence interval (CI): 1.08 to 4.98], p = 0.03). Major VC (HR: 2.31 [95% CI: 1.20 to 4.43], p = 0.012), and renal disease at baseline (HR: 2.26 [95% CI: 1.34 to 3.81], p = 0.002) were identified as independent predictors of 1-year mortality. CONCLUSIONS Major VC were frequent after TF-TAVR in the PARTNER trial using first-generation devices and were associated with high mortality. However, the incidence and impact of major VC on 1-year mortality decreased with lower-risk populations.

Clinical ResearchInterventional CardiologyVascular Complications After Transcatheter Aortic Valve Replacement: Insights From the PARTNER (Placement of AoRTic TraNscathetER Valve) Trial

OBJECTIVES This study sought to identify incidence, predictors, and impact of vascular complications (VC) after transfemoral (TF) transcatheter aortic valve replacement (TAVR). BACKGROUND VC after TF-TAVR are frequent and may be associated with unfavorable prognosis. METHODS From the randomized controlled PARTNER (Placement of AoRTic TraNscathetER Valve) trial, a total of 419 patients (177 from cohort B [inoperable] and 242 from cohort A [operable high-risk]) were randomly assigned to TF-TAVR and actually received the designated treatment. First-generation Edwards-Sapien valves and delivery systems were used, via a 22- or 24-F sheath. The 30-day rates of major and minor VC (modified Valve Academic Research Consortium definitions), predictors, and effect on 1-year mortality were assessed. RESULTS Sixty-four patients (15.3%) had major VC and 50 patients (11.9%) had minor VC within 30 days of the procedure. Among patients with major VC, vascular dissection (62.8%), perforation (31.3%), and access-site hematoma (22.9%) were the most frequent modes of presentation. Major VC, but not minor VC, were associated with significantly higher 30-day rates of major bleeding, transfusions, and renal failure requiring dialysis, and with a significantly higher rate of 30-day and 1-year mortality. The only identifiable independent predictor of major VC was female gender (hazard ratio [HR]: 2.31 [95% confidence interval (CI): 1.08 to 4.98], p = 0.03). Major VC (HR: 2.31 [95% CI: 1.20 to 4.43], p = 0.012), and renal disease at baseline (HR: 2.26 [95% CI: 1.34 to 3.81], p = 0.002) were identified as independent predictors of 1-year mortality. CONCLUSIONS Major VC were frequent after TF-TAVR in the PARTNER trial using first-generation devices and were associated with high mortality. However, the incidence and impact of major VC on 1-year mortality decreased with lower-risk populations.

Angiogenesis, Vasculogenesis, and Induction of Healing in Chronic Wounds

A key central stage of wound healing requires neovascularization of the wound base granulation tissue. In the adult, neovascularization is now known to occur by both angiogenesis and vasculogenesis. Understanding the biology of these 2 processes offers promising new therapeutic options for patients who suffer from chronic, nonhealing ischemic wounds. The authors review the current literature on the processes of angiogenesis and vasculogenesis and how it relates to wound healing.

Butyrate and the colonocyte : Implications for neoplasia

Butyrate is produced in the colon of mammals as a result of microbial fermentation of dietary fiber, undigested starch, and proteins. Butyrate may be an important protective agent in colonic carcinogenesis. Trophic effects on normal colonocytesin vitro andin vivo are induced by butyrate. In contrast, butyrate arrests the growth of neoplastic colonocytes and inhibits the preneoplastic hyperproliferation induced by some tumor promotersin vitro. We speculate that selective effects on G-protein activation may explain this paradox of butyrates effects in normal versus neoplastic colonocytes. Butyrate induces differentiation of colon cancer cell lines. It also regulates the expression of molecules involved in colonocyte growth and adhesion and inhibits the expression of several protooncogenes relevant to colorectal carcinogenesis. Additional studies are needed to evaluate butyrates antineoplastic effectsin vivo and to understand its mechanism(s) of action.

Butyrate and the colonocyte

Butyrate is one of the three principal short chain fatty acids (SCFA) in humans generated by colonic microbial fermentation of dietary substrates. SCFA are the C2-5 organic fatty acids, also called the volatile fatty acids (VFA), which include acetate, propionate and butyrate. Colonic intraluminal levels of butyrate may play a role in the pathogenesis of a variety of diseases of the large intestine. This chapter reviews the production, absorption, metabolism, and therapeutic implications of butyrate.

Notch signaling: Emerging molecular targets for cancer therapy

The Notch signaling pathway is a highly conserved developmental pathway, which plays a critical role in cell-fate decision, tissue patterning and morphogenesis. There is increasing evidence that this pathway is dysregulated in a variety of malignancies, and can behave as either an oncogene or a tumor suppressor depending upon cell context. This review highlights the current evidence for aberration of the Notch signaling pathway in a wide range of tumors from hematological cancers, such as leukemia and lymphoma through to skin, breast, lung, pancreas, colon and brain tumors. It proposes that the Notch signaling pathway may represent novel therapeutic targets and will be a welcome asset to the cancer therapeutic arena.

Fibroblast-dependent differentiation of human microvascular endothelial cells into capillary-like 3-dimensional networks

An in vitro model has been developed to study migration, survival, proliferation, and capillary‐like differentiation of human microvascular endothelial cells (HMVECs) in an environment that avoids tumor promoters and complex matrices. HMVEC monolayers were plated, then induced to form three‐dimensional, capillary‐like networks by overlaying with human type I collagen followed by a second overlay of collagen with embedded fibroblasts. Detachment and migration of endothelial cells into the matrix was triggered within hours by the overlaying collagen, and the fibroblasts stimulated survival and formation of cords, vacuoles, tubes, and, after 4 to 5 days, capillary networks. The differentiation into branching capillary‐like structures was dependent on direct fibroblast‐endothelial cell contact and was not achieved when fibroblasts were replaced by seven types of melanoma cells, which included radial and vertical growth phase primary and metastatic stages. Vascular endothelial growth factor (VEGF), when overexpressed in fibroblasts, stimulated endothelial cell proliferation and migration, whereas angiopoietin‐1 (Ang1) had only motogenic effects. Neutralizing antibodies against VEGF and blocking antibodies for VEGF‐receptor 2 (VEGFR2) significantly inhibited but not completely obliterated capillary network formation, suggesting that the VEGF signaling pathway is important but not exclusive and that other fibroblast‐derived soluble factors and fibroblast‐endothelial cell contact are essential for endothelial cell survival and differentiation.