Extracellular matrix ligands modulate the endothelial progenitor cell secretome for enhanced angiogenesis

Wound healing is a complex physiological process fundamentally dependent on angiogenesis for effective tissue repair. Endothelial progenitor cells (EPCs) have shown significant potential in promoting angiogenesis, primarily through their secretome, rich in proteins and extracellular vesicles (EVs) essential for cell signaling and tissue regeneration. This study investigates the effect of a collagen-bound proteoglycan mimetic (LXW7-DS-SILY or LDS), that binds to the alpha v(33 integrin receptor, on the EPC secretome, with a dual focus on the proteomic content and the functional properties of EVs. Utilizing high-resolution two-dimensional liquid chromatography-tandem mass spectrometry (LC-MS/MS) alongside bioinformatic analysis, we identified significant alterations in protein expression profiles, particularly in angiogenesis and wound healing pathways. The functional impact of these changes was validated through biological assays, where the whole secretome and the EV fraction from EPCs seeded on collagen-bound LDS markedly enhanced vascular network formation, driven by the increase of growth factors and angiogenic regulators such as FGFR1, NRP1, and ANGPT2 within the EV fraction. Gene Ontology (GO) enrichment analysis further highlighted the enrichment of proteins within the EVs driving biological processes, including 'response to wounding' and 'positive regulation of cell motility'. These results underscore that LDS modulates the EPC secretome and significantly enhances its angiogenic potential, offering a promising therapeutic strategy for non-healing and ischemic wounds and suggesting that biomaterials can be modified to control the EV secretome to enhance tissue repair. Functional assays validating the omics data highlight the robustness of LDS as a targeted therapeutic for enhancing angiogenesis and tissue repair in clinical settings. Moreover, the pivotal role of EVs in mediating pro-angiogenic effects offers insights into developing biomaterial therapies that exploit key regulators within the EPC secretome for wound healing. Statement of significance: This manuscript explores how a proteoglycan mimetic that binds to both collagen and the alpha v(33 integrin receptor affects the proteome component of the secretome from endothelial progenitor cells (EPCs). It presents functional biological data, analytical data, and proteomic analysis of the soluble and extra- cellular vesical (EV) components of the secratome. The proteomic data maps to the observed enhanced angiogenic potential of the EVs. These results suggest that by controlling the cellular environment and judicially engineering how cells interact with a biomaterial can influence the proteomic composition of EVs to enhance tissue regeneration. This is the foundation of future work aimed at engineering biomaterial cell systems to influence the proteomic component of EVs for therapeutic use.