Therapeutic angiogenesis due to balanced single‐vector delivery of VEGF and PDGF‐BB

Abstract

Therapeutic angiogenesis by delivery of vascular growth factors is an attractive strategy for treating debilitating occlusive vascular diseases, yet clinical trials have thus far failed to show efficacy. As a result, limb amputation remains a common outcome for muscle ischemia due to severe atherosclerotic disease, with an overall incidence of 100 per million people in the United States per year. A challenge has been that the angiogenic master regulator vascular endothelial growth factor (VEGF) induces dysfunctional vessels, if expressed outside of a narrow dosage window. We tested the hypothesis that codelivery of platelet-derived growth factor-BB (PDGF-BB), which recruits pericytes, could induce normal angiogenesis in skeletal muscle irrespective of VEGF levels. Coexpression of VEGF and PDGF-BB encoded by separate vectors in different cells or in the same cells only partially corrected aberrant angiogenesis. In marked contrast, coexpression of both factors in every cell at a fixed relative level via a single bicistronic vector led to robust, uniformly normal angiogenesis, even when VEGF expression was high and heterogeneous. Notably, in an ischemic hindlimb model, single-vector expression led to efficient growth of collateral arteries, revascularization, increased blood flow, and reduced tissue damage. Furthermore, these results were confirmed in a clinically applicable gene therapy approach by adenoviral-mediated delivery of the bicistronic vector. We conclude that coordinated expression of VEGF and PDGF-BB via a single vector constitutes a novel strategy for harnessing the potency of VEGF to induce safe and efficacious angiogenesis.

Mesenchymal stem cells contribute to vascular growth in skeletal muscle in response to eccentric exercise

“…Pericytes provide structural support for vessels and are hypothesized to prevent damage in the presence of increased blood flow and/or mechanical strain (1,33). The ability for pericytes to wrap and extend themselves around vessels suggests that these cells may be particularly sensitive to changes in mechanical strain that may occur during lengthening contractions.…”

Constitutive and inducible co-expression systems for non-viral osteoinductive gene therapy

“…If both transgenes are encoded on the same molecule, then the correlated expression of both factors obtained from co-expression plasmid transfer should theoretically be higher compared to co-transfection of 2 individual plasmids. This correlated co-expression from one single molecule can be advantageous for the production of heterodimeric growth factor variants (Kawai et al, 2009) or for balanced co-expression of 2 individual synergetic factors (Banfi et al, 2012).…”

“…Such, particular regulated expression kinetics could provide enhanced safety (on/off inductor dependence) and allow mimicking of physiological gene expression patterns for increased therapeutic efficacy. Systems such as the dual-component (activator and response plasmid) tetracycline (Tet) inducible or repressed (TetON, TetOFF) regulated gene expression systems (Gossen and Bujard, 1992;Goverdhana et al, 2005) can be applied for this purpose, even for co-expression of 2 therapeutic genes (Baron, 1995).…”

“…Furthermore, bi-directional inducible systems (Baron et al, 1995) can deliver 2 transgenes simultaneously under the control of an inducible bidirectional promoter. These systems, however, require the co-transfection of an activator plasmid, expressing the doxycycline responsive transactivator protein required for expression from the response plasmid.…”

Helen Blau

“…She has shown that active DNA demethylation is critical to reprograming cell fate, 5 characterized muscle stem cells and their regulation in bioengineered stem cell niches, 6,7 and studied their role in Duchenne muscular dystrophy, 8 as well working on gene therapy strategies for promoting angiogenesis. 9 Blau has achieved great success in her career and counts among her many honors election to of the American Academy of Arts and Sciences and the Institute of Medicine of the National Academy of Sciences, as well as fellowship in the American Association for the Advancement of Science.…”