Composite implantation of mesenchymal stem cells with endothelial progenitor cells enhances tissue‐engineered bone formation

Abstract

For successful tissue engineering, neovascularization of the implanted tissue is critical. Factors generated by endothelial cells are also considered crucial for the process of osteogenesis. The direct effects of supplementing tissue engineered constructs with cultured endothelial progenitor cells (EPCs) for enhancing bone regeneration have not been reported. In this study, we investigated the potential of EPCs to facilitate neovascularization in implants and evaluated their influence on bone regeneration. The influence of EPC soluble factors on osteogenic differentiation of mesenchymal stem cells (MSCs) was tested by adding EPC culture supernatant to MSC culture medium. To evaluate the influence of EPCs on MSC osteogenesis, canine MSCs-derived osteogenic cells and EPCs were seeded independently onto collagen fiber mesh scaffolds and co-transplanted to nude mice subcutaneously. Results from coimplant experiments were compared to implanted cells absent of EPCs 12 weeks after implantation. Factors from the culture supernatant of EPCs did not influence MSC differentiation. Coimplanted EPCs increased neovascularization and the capillary score was 1.6-fold higher as compared to the MSC only group (p < 0.05). Bone area was also greater in the MSC + EPC group (p < 0.05) and the bone thickness was 1.3-fold greater in the MSC + EPC group than the MSC only group (p < 0.05). These results suggest that soluble factors generated by EPCs may not facilitate the osteogenic differentiation of MSCs; however, newly formed vasculature may enhance regeneration of tissue-engineered bone.

Vasculogenic and Osteogenesis-Enhancing Potential of Human Umbilical Cord Blood Endothelial Colony-Forming Cells

“…Such increase in vascularization could make a direct contribution to bone formation, as evident in the increased ectopic bone formed in the EPC/MSC constructs, suggesting an interdependent relationship between vascularization and bone formation. Usami et al found a 1.6-fold higher capillary score formation on both the surface and central regions of canine-EPC/MSC scaffolds, accompanied by a 1.3-fold increase in bone area regenerated in subcutaneous implants [14], while Seebach et al demonstrated increased early vascularization in the first 4 weeks with improved bone regeneration and healing in a rat critical-sized femoral defect model after EPC/MSC implantation compared to MSC alone [13].…”

“…Several groups have cocultured putative EPC with MSC or osteoblast-like cell types on the premise that this strategy will generate prevascular networks within bone tissue-engineered grafts to aid bone repair [13][14][15][16][17][18]. However, the majority of studies used ECs [19][20][21][22][23] rather than ECFC.…”

Enhanced Osteogenesis in Cocultures with Human Mesenchymal Stem Cells and Endothelial Cells on Polymeric Microfiber Scaffolds

“…A variety of scaffold materials have been investigated for EC and MSC cocultures, including poly(e-caprolactone) (PCL), starch-based scaffolds with a fiber size of more than 200 mm, 16,17 hydroxyapatite (HA) and b-TCP (Ca 3 (PO4) 2 ) porous discs, 28 hydrophilic and hydrophobic titanium surfaces, 27 collagen mesh scaffolds, 29 and PCL-HA composite membranes. 30 Recently, porous microfiber mesh scaffolds made of biodegradable PCL have been developed using electrospinning.…”

Hypoxia Impedes Vasculogenesis of In Vitro Engineered Bone

“…9 Organized functional networks have been obtained in vivo by combining an endothelial cell source, for example, cord blood and peripheral blood-derived endothelial progenitor cells (EPCs) or human umbilical vein endothelial cells (HUVECs), with a mural cell source, for example, multipotent stromal cells (MSCs) or smooth muscle cells, in matrigel plugs. 6,[10][11][12] Previous studies focusing on prevascularized bone tissue engineering [13][14][15][16][17] have included several osteogenic cell sources, among which the primary osteoblasts 15,16 and the more proliferative MSCs 11,18 were most commonly used.…”