Impact of Endothelial Progenitor Cells in the Vascularization of Osteogenic Scaffolds

Abstract

The microvascular endothelial network plays an important role in osteogenesis, bone regeneration and bone tissue engineering. Endothelial progenitor cells (EPCs) display a high angiogenic and vasculogenic potential. The endothelialization of scaffolds with endothelial progenitor cells supports vascularization and tissue formation. In addition, EPCs enhance the osteogenic differentiation and bone formation of mesenchymal stem cells (MSCs). This study aimed to investigate the impact of EPCs on vascularization and bone formation of a hydroxyapatite (HA) and beta-tricalcium phosphate (ß-TCP)–fibrin scaffold. Three groups were designed: a scaffold-only group (A), a scaffold and EPC group (B), and a scaffold and EPC/MSC group (C). The HA/ß–TCP–fibrin scaffolds were placed in a porous titanium chamber permitting extrinsic vascularization from the surrounding tissue. Additionally, intrinsic vascularization was achieved by means of an arteriovenous loop (AV loop). After 12 weeks, the specimens were explanted and investigated by histology and CT. We were able to prove a strong scaffold vascularization in all groups. No differences regarding the vessel number and density were detected between the groups. Moreover, we were able to prove bone formation in the coimplantation group. Taken together, the AV loop is a powerful tool for vascularization which is independent from scaffold cellularization with endothelial progenitor cells’ prior implantation.

Additive Manufacturing Approaches to Design Pore Structures for Development of Bioactive Scaffolds for Orthopedic Applications: A Critical Review

“…Colonization of EPC matrices enhances their vascularization and formation of new bone tissue. Additionally, EPCs enhance osteogenic differentiation and osteogenesis of MSCs [191]. However, co-implantation of MSCs and EPCs did not enhance matrix vascularization, presumably because MSCs themselves can stimulate angiogenesis [192,193].…”

Development of Bioactive Scaffolds for Orthopedic Applications by Designing Additively Manufactured Titanium Porous Structures: A Critical Review

“…Colonization of EPC matrices enhances their vascularization and formation of new bone tissue. Additionally, EPCs enhance osteogenic differentiation and osteogenesis of MSCs [181]. However, co-implantation of MSCs and EPCs did not enhance matrix vascularization, presumably because MSCs themselves can stimulate angiogenesis [182,183].…”

Biofunctionalisation strategies of material surface and the inspired biological effects for bone repair

“…Several scaffold functionalisation strategies have been applied to promote vascularised tissue-engineered bone regeneration, including the addition of growth factors such as VEGF [174,191,192] and fibroblast growth factor [193,194]. Selection of suitable seed cells [195,196] and design of functional bionic scaffolds [197,198]. Therefore, in our previous work [160], PLGA obtrusive microspheres loaded with OGP and BMP-2 were prepared, and then PLGA microspheres were loaded on the surface of porous HA scaffolds similar in structure to natural spongy bone to construct biomimetic microspherehydroxyapatite composite scaffolds (Figure 13b) The results show that the multi-stage controlled release biomimetic scaffold system can regulate many events such as angiogenesis and bone tissue reconstruction during tissue regeneration.…”