Balanced single-vector co-delivery of VEGF/PDGF-BB improves functional collateralization in chronic cerebral ischemia

The myoblast-mediated delivery of angiogenic genes represents a cell-based approach for targeted induction of therapeutic collateralization. Here, we tested the superiority of myoblast-mediated co-delivery of vascular endothelial growth factor-A (VEGF) together with platelet-derived growth factor-BB (PDGF-BB) on transpial collateralization of an indirect encephalomyosynangiosis (EMS) in a model of chronic cerebral ischemia. Mouse myoblasts expressing a reporter gene alone (empty vector), VEGF, PDGF-BB or VEGF and PDGF-BB through a single bi-cistronic vector (VIP) were implanted into the temporalis muscle of an EMS following permanent ipsilateral internal carotid artery occlusion in adult, male C57BL/6N mice. Over 84 days, myoblast engraftment and gene product expression, hemodynamic impairment, transpial collateralization, angiogenesis, pericyte recruitment and post-ischemic neuroprotection were assessed. By day 42, animals that received PDGF-BB in combination with VEGF (VIP) showed superior hemodynamic recovery, EMS collateralization and ischemic protection with improved pericyte recruitment around the parenchymal vessels and EMS collaterals. Also, supplementation of PDGF-BB resulted in a striking astrocytic activation with intrinsic VEGF mobilization in the cortex below the EMS. Our findings suggest that EMS surgery together with myoblast-mediated co-delivery of VEGF/PDGF-BB may have the potential to serve as a novel treatment strategy for augmentation of collateral flow in the chronically hypoperfused brain

Reevaluation of the role of VEGF-B suggests a restricted role in the revascularization of the ischemic myocardium .

peer reviewedOBJECTIVE: The endogenous role of the VEGF family member vascular endothelial growth factor-B (VEGF-B) in pathological angiogenesis remains unclear. METHODS AND RESULTS: We studied the role of VEGF-B in various models of pathological angiogenesis using mice lacking VEGF-B (VEGF-B(-/-)) or overexpressing VEGF-B(167). After occlusion of the left coronary artery, VEGF-B deficiency impaired vessel growth in the ischemic myocardium whereas, in wild-type mice, VEGF-B(167) overexpression enhanced revascularization of the infarct and ischemic border zone. By contrast, VEGF-B deficiency did not affect vessel growth in the wounded skin, hypoxic lung, ischemic retina, or ischemic limb. Moreover, VEGF-B(167) overexpression failed to enhance vascular growth in the skin or ischemic limb. CONCLUSIONS: VEGF-B appears to have a relatively restricted angiogenic activity in the ischemic heart. These insights might offer novel therapeutic opportunitie

Efficient in vivo vascularization of tissue-engineering scaffolds

The success of tissue engineering depends on the rapid and efficient formation of a functional blood vasculature. Adult blood vessels comprise endothelial cells and perivascular mural cells that assemble into patent tubules ensheathed by a basement membrane during angiogenesis. Using individual vessel components, we characterized intra-scaffold microvessel self-assembly efficiency in a physiological in vivo tissue engineering implant context. Primary human microvascular endothelial and vascular smooth muscle cells were seeded at different ratios in poly- L -lactic acid (PLLA) scaffolds enriched with basement membrane proteins (Matrigel) and implanted subcutaneously into immunocompromised mice. Temporal intra-scaffold microvessel formation, anastomosis and perfusion were monitored by immunohistochemical, flow cytometric and in vivo multiphoton fluorescence microscopy analysis. Vascularization in the tissue-engineering context was strongly enhanced in implants seeded with a complete complement of blood vessel components: human microvascular endothelial and vascular smooth muscle cells in vivo assembled a patent microvasculature within Matrigel-enriched PLLA scaffolds that anastomosed with the host circulation during the first week of implantation. Multiphoton fluorescence angiographic analysis of the intra-scaffold microcirculation showed a uniform, branched microvascular network. 3D image reconstruction analysis of human pulmonary artery smooth muscle cell (hPASMC) distribution within vascularized implants was non-random and displayed a preferential perivascular localization. Hence, efficient microvessel self-assembly, anastomosis and establishment of a functional microvasculture in the native hypoxic in vivo tissue engineering context is promoted by providing a complete set of vascular components. Copyright © 2010 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/83466/1/336_ftp.pd

Muscle cell derived angiopoietin-1 contributes to both myogenesis and angiogenesis in the ischemic environment

Recent strategies to treat peripheral arterial disease (PAD) have focused on stem cell based therapies, which are believed to result in local secretion of vascular growth factors. Little is known, however, about the role of ischemic endogenous cells in this context. We hypothesized that ischemic muscle cells (MC) are capable of secreting growth factors that act as potent effectors of the local cellular regenerative environment. Both muscle and endothelial cells (ECs) were subjected to experimental ischemia, and conditioned medium (CM) from each was collected and analyzed to assess myogenic and/or angiogenic potential. In muscle progenitors, mRNA expression of VEGF and its cognate receptors (Nrp1, Flt, Flk) was present and decreased during myotube formation in vitro, and EC CM or VEGF increased myoblast proliferation. Angiopoietin-1 (Ang-1), Tie1, and Tie2 mRNA increased during MC differentiation in vitro. Exogenous Ang-1 enhanced myogenic (MyoD and Myogenin) mRNA in differentiating myoblasts and increased myosin heavy chain protein. Myotube formation was enhanced by MC CM and inhibited by EC CM. Ang-1 protein was present in CM from MCs isolated from both the genetically ischemia-susceptible BALB/c and ischemia-resistant C57BL/6 mouse strains, and chimeric Tie2 receptor trapping in situ ablated Ang-1's myogenic effects in vitro. Ang-1 or MC CM enhanced myotube formation in a mixed isolate of muscle progenitors as well as a myoblast co-culture with pluripotent mesenchymal cells (10T1/2) and this effect was abrogated by viral expression of the extracellular domain of Tie2 (AdsTie2). Furthermore, mesh/tube formation by HUVECs was enhanced by Ang-1 or MC CM and abrogated by Tie2 chimeric receptor trapping. Our results demonstrate the ability of muscle and endothelial cell-derived vascular growth factors, particularly Ang-1, to serve as multi-functional stimuli regulating crosstalk between blood vessels and muscle cells during regeneration from ischemic myopathy

Cell Therapy for Cardiovascular Disease: A Comparison of Methods of Delivery

The field of myocardial regeneration utilizing novel cell-based therapies, gene transfer, and growth factors may prove to play an important role in the future management of ischemic heart disease and cardiomyopathy. Phases I and II clinical trials have been published for a variety of biologics utilizing four methods of delivery: systemic infusion, intracoronary infusion, transvenous coronary sinus, and intramyocardial. This review discusses the advantages and disadvantages of the delivery approaches above

Consensus guidelines for the use and interpretation of angiogenesis assays

The formation of new blood vessels, or angiogenesis, is a complex process that plays important roles in growth and development, tissue and organ regeneration, as well as numerous pathological conditions. Angiogenesis undergoes multiple discrete steps that can be individually evaluated and quantified by a large number of bioassays. These independent assessments hold advantages but also have limitations. This article describes in vivo, ex vivo, and in vitro bioassays that are available for the evaluation of angiogenesis and highlights critical aspects that are relevant for their execution and proper interpretation. As such, this collaborative work is the first edition of consensus guidelines on angiogenesis bioassays to serve for current and future reference

Thrombin Has Biphasic Effects on the Nitric Oxide-cGMP Pathway in Endothelial Cells and Contributes to Experimental Pulmonary Hypertension

<div><p>Background</p><p>A potential role for coagulation factors in pulmonary arterial hypertension has been recently described, but the mechanism of action is currently not known. Here, we investigated the interactions between thrombin and the nitric oxide-cGMP pathway in pulmonary endothelial cells and experimental pulmonary hypertension.</p><p>Principal Findings</p><p>Chronic treatment with the selective thrombin inhibitor melagatran (0.9 mg/kg daily via implanted minipumps) reduced right ventricular hypertrophy in the rat monocrotaline model of experimental pulmonary hypertension. <i>In vitro</i>, thrombin was found to have biphasic effects on key regulators of the nitric oxide-cGMP pathway in endothelial cells (HUVECs). Acute thrombin stimulation led to increased expression of the cGMP-elevating factors endothelial nitric oxide synthase (eNOS) and soluble guanylate cyclase (sGC) subunits, leading to increased cGMP levels. By contrast, prolonged exposition of pulmonary endothelial cells to thrombin revealed a characteristic pattern of differential expression of the key regulators of the nitric oxide-cGMP pathway, in which specifically the factors contributing to cGMP elevation (eNOS and sGC) were reduced and the cGMP-hydrolyzing PDE5 was elevated (qPCR and Western blot). In line with the differential expression of key regulators of the nitric oxide-cGMP pathway, a reduction of cGMP by prolonged thrombin stimulation was found. The effects of prolonged thrombin exposure were confirmed in endothelial cells of pulmonary origin (HPAECs and HPMECs). Similar effects could be induced by activation of protease-activated receptor-1 (PAR-1).</p><p>Conclusion</p><p>These findings suggest a link between thrombin generation and cGMP depletion in lung endothelial cells through negative regulation of the nitric oxide-cGMP pathway, possibly mediated via PAR-1, which could be of relevance in pulmonary arterial hypertension.</p></div

Thrombin-induced nitric oxide-cGMP pathway dysfunction is mediated via activation of protease-activated receptor-1.

<p>Exposure of HUVECs to different concentration of the PAR-1 activating peptide TRAP-1 (1 to 100 µg/ml) over 6 hours leads to reduced expression of (A) eNOS, (B) sGC alpha 1 and (C) sGC beta 1, whereas (D) PDE5 protein expression is increased. (E) Prolonged TRAP-10 exposition over 14 hours leads to cGMP depletion in HUVECs in presence of DETA NONOate (100 µM). Data shown as mean ± SEM (A, B, C, D: n = 6/group; E: n = 9/group). *<i>p</i><0.05, **<i>p</i><0.01, ***<i>p</i><0.001 vs cells not exposed to TRAP-10.</p