J Biomed Mater Res A. 2019 Aug 20.
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 (OECs). Our results show that: (a) repeated short-term hypoxia (2% O2 for 8 h), not long-term hypoxia (2% O2 for 24 h), 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 (VEGF), platelet-derived growth factor subunit B (PDGF-b), insulin-like growth factor 1 (IGF-1), interleukin-8 (IL-8), and early growth response protein 1 (EGR-1) increases significantly in hypoxia-treated POB monoculture and co-cultures after single or multiple 8-h or 24-h hypoxic treatments; (d) long-term (24 h) 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/anti-angiogenic factors, and that repeated short-term hypoxia, but not repeated long-term hypoxia, promotes the vascularization and tissue regeneration of bone tissue constructs. This article is protected by copyright. All rights reserved.
Keywords: Hypoxia; bone engineering; outgrowth endothelial cell; primary osteoblast; vascularization/angiogenesis