Overcoming disease-induced growth factor resistance in therapeutic angiogenesis using recombinant co-receptors delivered by a liposomal system

Abstract

Current treatment options for ischemia include percutaneous interventions, surgical bypass or pharmacological interventions aimed at slowing the progression of vascular disease. Unfortunately, while each of these treatment modalities provides some benefit for patients in the short-term, many patients have resistant or recurrent disease that is poorly managed by these therapies. A highly appealing strategy for treating ischemic disease is to stimulate the revascularization of the tissue to restore blood flow. While many techniques have been explored in this regard, clinically effective angiogenic therapies remain elusive. Here, we hypothesized that the presence of co-morbid disease states inherently alters the ability of the body to respond to angiogenic therapies. Using a mouse model of diabetes and obesity, we examined alterations in the major components for the signaling pathways for FGF-2, VEGF-A and PDGF under normal and high fat dietary conditions. In skeletal muscle, a high fat diet increased levels of growth factor receptors and co-receptors including syndecan-1, syndecan-4 and PDGFR-□in wild-type mice. These increases did not occur in Ob/Ob mice on a high fat diet and there was a significant decrease in protein levels for neuropilin-1 and heparanase in these mice. With the aim of increasing growth factor effectiveness in the context of disease, we examined whether local treatment with alginate gel-delivered FGF-2 and syndecan-4 proteoliposomes could overcome the growth factor resistance in these mice. This treatment enhanced the formation of new blood vessels in Ob/Ob mice by 6 fold in comparison to FGF-2 delivered alone. Our studies support that disease states cause a profound shift in growth factor signaling pathways and that co-receptor-based therapies have potential to overcome growth factor resistance in the context of disease states.

Loss of Syndecan-1 Induces a Pro-inflammatory Phenotype in Endothelial Cells with a Dysregulated Response to Atheroprotective Flow

“…Thus, our findings imply that disease-induced increases in proteolytic activity leading to shedding of sdc-1 from the surface may alter endothelial inflammatory phenotype and shear sensitivity to atheroprotective flow. We have recently found that Ob/Ob mice given a high fat diet have lower levels of sdc-1 protein in their heart and skeletal muscle (51). In addition, sdc-1 is a target for heparanase activity and leads to shedding from the cell surface (52).…”

“…Our work supports that loss of sdc-1 from the endothelial surface leads to the adoption of a pro-inflammatory phenotype that is dysregulated in response to the atheroprotective effects of flow. Many disease states increase the expression of enzymes that could induce the shedding and degradation of sdc-1 causing its loss from the endothelial surface (51,59,60). Thus, therapies that preserve or enhance sdc-1 on the endothelial surface, either through increased expression or inhibition of shedding, may have potential in preventing the early stages of atherogenesis and enhancing the atheroprotective effects of shear stress.…”

Syndecan‐4 Enhances Therapeutic Angiogenesis after Hind Limb Ischemia in Mice with Type 2 Diabetes

“…We have recently explored the concept of “growth factor resistance” in therapeutic angiogenesis and found that many co-receptors for growth factor signaling are altered in the diabetic disease state. [9] Among these co-receptors, syndecan-4 is a cell surface, transmembrane protein that is glycosylated with heparan sulfate glycosaminoglycans. Syndecan-4 acts a co-receptor for fibroblast growth factor-2 (FGF-2) and other growth factors, as well as regulating myriad cellular functions including migration, proliferation and homeostasis.…”

“…[9] Syndecan-4 plays an important role in the FGF-2 signaling pathway. [10] Our strategy to circumvent the reduction in syndecan-4 levels was to deliver the missing syndecan-4 co-receptors embedded in a liposomal membrane to enhance the activity of FGF-2 therapy (Figure.…”

“…We have previously demonstrated that this mouse model is resistant to growth factor therapy and has reduced expression of syndecan-4. [9] Here, we examined whether delivery of exogenous syndecan-4 could improve therapeutic angiogenesis in the diabetic disease state. We demonstrate that the syndecan-4 proteoliposomes increase the recovery of perfusion and vessel density following femoral ligation in diabetic, ob/ob mice.…”