Endothelial progenitor cell sprouting in spheroid cultures is resistant to inhibition by osteoblasts: A model for bone replacement grafts

Abstract

Survival of tissue transplants generated in vitro is strongly limited by the slow process of graft vascularization in vivo. A method to enhance graft vascularization is to establish a primitive vascular plexus within the graft prior to transplantation. Endothelial cells (EC) cultured as multicellular spheroids within a collagen matrix form sprouts resembling angiogenesis in vitro. However, osteoblasts integrated into the graft suppress EC sprouting. This inhibition depends on direct cell-cell-interactions and is characteristic of mature ECs isolated from preexisting vessels. In contrast, sprouting of human blood endothelial progenitor cells is not inhibited by osteoblasts, making these cells suitable for tissue engineering of pre-vascularized bone grafts.

Combinatory inhibition of VEGF and FGF2 is superior to solitary VEGF inhibition in an in vitro model of RPE-induced angiogenesis

“…Additionally, HUVECs were used in earlier spheroidal sprouting models [11,13,14,[29][30][31], and thus render readouts from this assay comparable to other in vitro sprouting models. Both HUVECs and HMVECs demonstrated a strong angiogenic response upon stimulation with CNV-RPE.…”

Hypoxia Impedes Vasculogenesis of In Vitro Engineered Bone

“…14,19 Although endothelial cells and EPCs exhibited comparable angiogenic properties in monoculture, 20 EPCs (derived from the CD34 + /CD133 + fraction from umbilical cord blood) were shown to be less hindered by the presence of osteoblasts than HUVECs in a sprouting assay. 21 In addition to this advantage, sufficient endothelial progenitors can be obtained from expanded isolates of adult peripheral blood, and they represent a clinically relevant cell source. 14 The majority of co-culture studies has focused on the formation of prevascular structures rather than on osteogenic differentiation.…”

Human Umbilical Vein Endothelial Cells Migration in Matrigel by the Concentration Gradient of Vascular Endothelial Growth Factor

“…For example, in the case of a monolayer of endothelial cells seeded at 1 × 10 4 cells onto the surface of a 3D collagen gel, only 10 cells were migrated into the collagen gel [47]. This phenomenon of cell migration in the aortic ring outgrowth and the sprouting assays, which are well performed as the 3D angiogenesis assay, show the same behavior [48,49]. It is suggested that the percentage of HUVEC migrated to total cells is quite small.…”