Early endothelial progenitor cells as a source of myeloid cells to improve the pre-vascularisation of bone constructs

Abstract

According to present knowledge, blood derived endothelial progenitor cells (EPC) might act as proangiogenic myeloid cells, which play a fundamental role in the regulation of angiogenesis and blood vessel reorganisation. In this context, we have evaluated the contribution of endogenous myeloid cells in co-cultures of blood derived outgrowth endothelial cells (OEC) and osteogenic cells. In addition, we investigated the role of EPC as a potential source of myeloid cells in the formation of vascular structures in an in vitro model consisting of mesenchymal stem cells (MSC) and OEC. For this purpose, we added EPCs to cocultures of MSC and OECs. Vascular structures and the co-localisation of myeloid cells were analysed by confocal laser microscopy (CLSM) for endothelial and myeloid markers and quantitative image analysis. The molecular effects of myeloid cells were evaluated by quantitative real time PCR, ELISA and protein arrays from cell culture supernatants and lysates. Endogenous myeloid cells were significantly co-localised with angiogenic structures in co-cultures of OEC and osteogenic cells. The active addition of EPC to co-cultures of OEC and MSC resulted in a statistically approved increase in the formation of prevascular structures at early stages of the co-culture process. In addition, we observed an increase of endothelial markers, indicating beneficial effects of EPC or myeloid cells on endothelial cell growth. Furthermore, real time PCR indicated high expression levels of CD68, CD11b and CD163 in co-cultures of EPC and MSC indicating that EPC act at least partly as macrophage like-cells.

Self‐Healing Silk Fibroin‐Based Hydrogel for Bone Regeneration: Dynamic Metal‐Ligand Self‐Assembly Approach

“…Initial results indicated expression of alkaline phosphatase (ALP), collagen type I (Col I), osteocalcin (OC), Runt-related transcription factor 2 (RUNX2), and vascular endothelial growth factor (VEGF) in both DC Am-HA-BP·CaP@mSF and Am-HA-BP+mSF hydrogels at different levels (Figure 6c). [61][62][63][64] The present in vitro results show no restrictions in terms of the biocompatibility or biofunctionality of DC Am-HA-BP·CaP@mSF hydrogel and show a favored arrangement and affinity of MSC toward mineralized fibers as indicated in Figure 6a. In this context Col I can be considered as an early marker for osteogenic differentiation whereas OC is related to the later stages of osteogenic differentiation and the calcification.…”

Ischemia‐induced Netrin‐4 promotes neovascularization through endothelial progenitor cell activation via Unc‐5 Netrin receptor B

“…Student's t test was applied. [45][46][47][48][49][50][51] Moreover, we discovered that EPC-secreted paracrine factors activated their respective receptors and downstream signaling molecules in ECs. 26,42,43 There are four families of axon guidance molecules (slit, semaphorin, NTN, and ephrin) and their receptors (the UNC5, neogenin, plexin, roundabout, and Eph).…”

Tissue engineering strategies for promoting vascularized bone regeneration

“…Angiogenesis is crucial in bone repair 97,98 and the formation of new blood vessels depends on the ordered interaction of endothelial cells with different types of cells including, macrophages, pericytes, endothelial progenitor cells (EPCs), and MSCs 99–101 . It is clear that multiple stem cell types, immunogenic cues, and cytokines participate in, and are necessary, to initiate angiogenesis and osteogenesis.…”

“…In vivo , EPCs have been shown to be highly effective in mobilizing to areas of ischemic damage and promoting neovascularization 147,148 . The pro-angiogenic effect exerted by EPCs appears dependent on their ability to stimulate endothelial cells growth 101 and interact with mature endothelial cells to support vascular anastomosis 149 . Nevertheless, the mechanisms by which the EPCs exert beneficial effects on endothelial cell growth is likely multifactorial and might include the transdifferentiation of subpopulations of EPCs into mature endothelial cells 150 .…”

“…166–168 It has been suggested that MSCs are the major producer of VEGF during vascular bone regeneration. 101,167,169 These MSC secreted pro-angiogenic factors stimulate EPC proliferation and differentiation, which in turn causes EPCs to secrete osteogenic growth factors that stimulate MSC differentiation. 170,171 While data suggests that BM-MSCs and ADSC secrete comparable levels of angiogenic factors 172 , one study found that co-culture of these cells together promoted enhanced angiogenesis by increasing VEGF production and improving osteogenesis.…”