Oxygen tension regulating hydrogels for vascularization and osteogenesis via sequential activation of HIF-1α and ERK1/2 signaling pathways in bone regeneration
Xianzhen Yin, Yihao Wei, Haotian Qin, Jin Zhao, Yixiao Chen, Yixiao Chen, Sen Yao, Nan Li, Ao Xiong, Deli Wang, Peng Zhang, Peng Liu, Hui Zeng, Yingqi Chen, Yingqi Chen
Abstract
Angiogenesis plays a crucial role in bone regeneration . Hypoxia is a driving force of angiogenesis at the initial stage of tissue repair. The hypoxic microenvironment could activate the hypoxia-inducible factor (HIF)-1α signaling pathway in cells, thereby enhancing the proliferation, migration and pro-angiogenic functions of stem cells. However, long-term chronic hypoxia could inhibit osteogenic differentiation and even lead to apoptosis. Therefore, shutdown of the HIF-1α signaling pathway and providing oxygen at later stage probably facilitate osteogenic differentiation and bone regeneration. Herein, an oxygen tension regulating hydrogel that sequentially activate and deactivate the HIF-1α signaling pathway were prepared in this study. Its effect and mechanism on stem cell differentiation were investigated both in vitro and in vivo . We proposed a gelatin-based hydrogel capable of sequentially delivering a hypoxic inducer (copper ions) and oxygen generator (calcium peroxide). The copper ions released from the hydrogels significantly enhanced cell viability and VEGF secretion of BMSCs via upregulating HIF-1α expression and facilitating its translocation into the nucleus. Additionally, calcium peroxide promoted alkaline phosphatase activity, osteopontin secretion, and calcium deposition through the activation of ERK1/2. Both Cu 2+ and calcium peroxide demonstrated osteogenic promotion individually, while their synergistic effect within the hydrogels led to a superior osteogenic effect by potentially activating the HIF-1α and ERK1/2 signaling pathways.