Short‐term hypoxia promotes vascularization in co‐culture system consisting of primary human osteoblasts and outgrowth endothelial cells

Abstract

Prevascularization of tissue constructs before implantation has been developed as a novel and promising concept for successful implantation. Since hypoxia might induce angiogenesis, we have investigated the effects of hypoxic treatment on vascularization by using co-cultures of primary human osteoblasts (POBs) and outgrowth endothelial cells. Our results show that: (a) repeated short-term hypoxia (2% O 2 for 8 hr), not longterm hypoxia (2% O 2 for 24 hr), over 1 or 2 weeks, significantly enhances microvessel formation in co-cultures; (b) sustained hypoxia, not short-term or long-term hypoxia, causes cytotoxicity in mono-and co-cultures; (c) the expression of some angiogenic and inflammatory factors such as vascular endothelial growth factor, platelet-derived growth factor subunit B, insulin-like growth factor 1, interleukin-8, and early growth response protein 1 increases significantly in hypoxia-treated POB monoculture and cocultures after single or multiple 8-or 24-hr hypoxic treatments; (d) long-term (24 hr) hypoxic treatment induces more angiogenic inhibitors compared with short-term hypoxic treatment. Our findings suggest that hypoxia-induced vascularization/angiogenesis is regulated by a complex balance of angiogenic/antiangiogenic factors, and that repeated short-term hypoxia, but not repeated long-term hypoxia, promotes the vascularization and tissue regeneration of bone tissue constructs. K E Y W O R D S bone engineering, hypoxia, outgrowth endothelial cell, primary osteoblast, vascularization/ angiogenesis

Use of in vitro bone models to screen for altered bone metabolism, osteopathies, and fracture healing: challenges of complex models

“…However, it is not yet known how changes in bone metabolism affect vascularization or vice versa how an altered vasculature affects bone metabolism. So far, most co-culture models focused on the influence of osteogenic cells and endothelial cells in direct and indirect co-cultures (Fuchs et al 2007 ; Ghanaati et al 2011 ; Hofmann et al 2008 ; Li et al 2014 ; Ma et al 2020 ; Shi et al 2016 ; Sun et al 2016 ), not considering, that the interplay of the presence of osteoclastic cells may alter the function of the osteogenic cells or vice versa (Zachos et al 2014 ). Even more complex is the situation, when investigating fracture healing.…”

Strategies for Peripheral Nerve Repair

“…Injury results in the damage of blood vessels, leading to hypoxia around the peripheral nerve injury bridge. Short-term hypoxia may induce some advantageous changesit has been found to enhance c-Myc transcription in cell lines [71], and to promote vascularisation [72][73][74], but long-term hypoxia will lead to cell death [75]. VEGF, expressed by macrophages in the nerve bridge [70], is essential to promote blood vessel growth [76].…”

Vascularization of 3D Engineered Tissues

“…In a hypoxia-treated coculture study, short-term hypoxia (2%, 8 h) treated co-culture of primary human osteoblasts in vitro, and ECs significantly enhanced microvessel formation. In addition, an increase in the expression of proangiogenic factors, such a VEGF, PDGF-BB, and IGF-I, was observed as compared to long-term (2%, 24 h) hypoxia co-culture group (Ma et al 2020). In a rat critical-sized calvaria defect model, implantation of a gelatin sponge scaffold containing HIF-1α mediated bone mesenchymal stem cells (BMSCs) significantly improved the key angiogenic factors, including VEGF, SDF-1, bFGF, PLGF, ANG-1, and stem cell factor, as well as enhanced vessel formation and bone regeneration (Zou et al 2012).…”