PDGF-BB regulates splitting angiogenesis in skeletal muscle by limiting VEGF-induced endothelial proliferation

Abstract

VEGF induces normal or aberrant angiogenesis depending on its dose in the microenvironment around each producing cell in vivo. This transition depends on the balance between VEGF-induced endothelial stimulation and PDGF-BB-mediated pericyte recruitment, and co-expression of PDGF-BB normalizes aberrant angiogenesis despite high VEGF doses. We recently found that VEGF over-expression induces angiogenesis in skeletal muscle through an initial circumferential vascular enlargement followed by longitudinal splitting, rather than sprouting. Here we investigated the cellular mechanism by which PDGF-BB co-expression normalizes VEGF-induced aberrant angiogenesis. Monoclonal populations of transduced myoblasts, expressing similarly high levels of VEGF alone or with PDGF-BB, were implanted in mouse skeletal muscles. PDGF-BB co-expression did not promote sprouting and angiogenesis that occurred through vascular enlargement and splitting. However, enlargements were significantly smaller in diameter, due to a significant reduction in endothelial proliferation, and retained pericytes, which were otherwise lost with high VEGF alone. A time-course of histological analyses and repetitive intravital imaging showed that PDGF-BB co-expression anticipated the initiation of vascular enlargement and markedly accelerated the splitting process. Interestingly, quantification during in vivo imaging suggested that a global reduction in shear stress favored the initiation of transluminal pillar formation during VEGF-induced splitting angiogenesis. Quantification of target gene expression showed that VEGF-R2 signaling output was significantly reduced by PDGF-BB co-expression compared to VEGF alone. In conclusion, PDGF-BB co-expression prevents VEGF-induced aberrant angiogenesis by modulating VEGF-R2 signaling and endothelial proliferation, thereby limiting the degree of circumferential enlargement and enabling efficient completion of vascular splitting into normal capillary networks despite high VEGF doses.

Metabolic regulation of exercise-induced angiogenesis

“…Skeletal muscle VEGF mRNA (33) and protein (34) levels transiently increase after acute exercise bouts and VEGF is essential for exercise-induced angiogenesis (35,36), though it is not clear whether this is by promoting splitting or sprouting angiogenesis. Even though VEGF is a powerful stimulator of sprouting angiogenesis (17), its overexpression by myoblasts implanted into skeletal muscle increases capillarity essentially via intussusception (29,37). The VEGF levels in such model, however, are much higher than those observed upon exercise (29).…”

Therapeutic vascularization in regenerative medicine

“…Studies in skeletal muscle showed that the transition between normal and aberrant angiogenesis is not determined exclusively by VEGF dose, but rather by the balance between endothelial activation by VEGF and pericyte recruitment by PDGF‐BB . Codelivery of VEGF 164 and PDGF‐BB at a fixed relative ratio, achieved through coexpression from a single bicistronic vector, ensured the generation and long‐term stability of exclusively normal and functional microvascular networks regardless of absolute VEGF dose, by limiting endothelial proliferation . Although PDGF‐BB alone does not induce vascular growth either in normal or ischemic skeletal muscle, the beneficial effects of the VEGF/PDGF‐BB combination have been described in a variety of preclinical settings, including gene delivery with adenoviral or adeno‐associated viral vectors, sustained release of the recombinant factors from polymeric biomaterials or treatment with modified proteins engineered for super‐affinity to the ECM …”

“…84 Codelivery of VEGF 164 and PDGF-BB at a fixed relative ratio, achieved through coexpression from a single bicistronic vector, ensured the generation and long-term stability of exclusively normal and functional microvascular networks regardless of absolute VEGF dose, 84,85 by limiting endothelial proliferation. 33 Although PDGF-BB alone does not induce vascular growth either in normal or ischemic skeletal muscle, 84,86 the beneficial effects of the VEGF/ PDGF-BB combination have been described in a variety of preclinical settings, including gene delivery with adenoviral 86 or adenoassociated viral vectors, 87 sustained release of the recombinant factors from polymeric biomaterials 88 or treatment with modified proteins engineered for super-affinity to the ECM. 77 As described above, pericytes exchange a complex molecular crosstalk with endothelium and these signaling pathways can offer more specific targets to regulate VEGF effects.…”

The Angiogenic Paracrine Potential of Mesenchymal Stem Cells

“…Has a role of a pro-angiogenic agent [43] PD-ECGF +/− Stimulates angiogenesis [44] PDGF-AA +/+ Has positive effects on MSC proliferation and stimulates angiogenesis [45] PDGF-AB/ PDGF-BB +/− Induces neovascularization and arteriogenesis [27] Persefin +/− Induces angiogenesis [3] PlGF +/+ Has a role of a pro-angiogenic factor [46] Prolactin +/− Has a role of a pro-angiogenic factor in intact form [47] Sphingosine kinase 1 +/+ Promotes angiogenesis [48] SDF-1α -/+ An important chemotactic factor for progenitor cells. Stimulates stem cell migration, adhesion, and homing [3] TGF-β1 +/− Promotes angiogenesis at least in part via the secretion of the survival factors TGF-α and VEGF [3] uPA +/+ Promotes endothelial cell proliferation and migration and has positive effects in vascular network formation [49] VEGF +/+ Promotes angiogenesis [50] VEGF-C +/− Promotes lymphangiogenesis [50] At present, the combination of cell and tissue engineering techniques increased the restoration potential of a distinct cell type after transplantation [77].…”