Wan Lin, Zhang Fengjie, He Qiling, Tsang Wing Pui, Lu Li, Li Qingnan, Wu Zhihong, Qiu Guixing, Zhou Guangqian, Wan Chao
Ministry of Education Key Laboratory for Regenerative Medicine, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China.
Ministry of Education Key Laboratory for Regenerative Medicine, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong SAR, China; School of Biomedical Sciences Core Laboratory, Shenzhen Research Institute, The Chinese University of Hong Kong, Shenzhen, China.
PLoS One. 2014 Jul 8;9(7):e102010. doi: 10.1371/journal.pone.0102010. eCollection 2014.
Erythropoietin (EPO)/erythropoietin receptor (EPOR) signaling is involved in the development and regeneration of several non-hematopoietic tissues including the skeleton. EPO is identified as a downstream target of the hypoxia inducible factor-α (HIF-α) pathway. It is shown that EPO exerts a positive role in bone repair, however, the underlying cellular and molecular mechanisms remain unclear. In the present study we show that EPO and EPOR are expressed in the proliferating, pre-hypertrophic and hypertrophic zone of the developing mouse growth plates as well as in the cartilaginous callus of the healing bone. The proliferation rate of chondrocytes is increased under EPO treatment, while this effect is decreased following siRNA mediated knockdown of EPOR in chondrocytes. EPO treatment increases biosynthesis of proteoglycan, accompanied by up-regulation of chondrogenic marker genes including SOX9, SOX5, SOX6, collagen type 2, and aggrecan. The effects are inhibited by knockdown of EPOR. Blockage of the endogenous EPO in chondrocytes also impaired the chondrogenic differentiation. In addition, EPO promotes metatarsal endothelial sprouting in vitro. This coincides with the in vivo data that local delivery of EPO increases vascularity at the mid-stage of bone healing (day 14). In a mouse femoral fracture model, EPO promotes cartilaginous callus formation at days 7 and 14, and enhances bone healing at day 28 indexed by improved X-ray score and micro-CT analysis of microstructure of new bone regenerates, which results in improved biomechanical properties. Our results indicate that EPO enhances chondrogenic and angiogenic responses during bone repair. EPO's function on chondrocyte proliferation and differentiation is at least partially mediated by its receptor EPOR. EPO may serve as a therapeutic agent to facilitate skeletal regeneration.
促红细胞生成素（EPO）/促红细胞生成素受体（EPOR）信号通路参与包括骨骼在内的多种非造血组织的发育和再生。EPO被确定为缺氧诱导因子-α（HIF-α）通路的下游靶点。研究表明，EPO在骨修复中发挥积极作用，但其潜在的细胞和分子机制仍不清楚。在本研究中，我们发现EPO和EPOR在发育中小鼠生长板的增殖区、前肥大区和肥大区以及愈合骨的软骨痂中均有表达。EPO处理可提高软骨细胞的增殖率，而在软骨细胞中通过小干扰RNA（siRNA）介导敲低EPOR后，这种作用减弱。EPO处理可增加蛋白聚糖的生物合成，并伴随着软骨生成标记基因（包括SOX9、SOX5、SOX6、Ⅱ型胶原蛋白和聚集蛋白聚糖）的上调。这些作用可被EPOR敲低所抑制。阻断软骨细胞内源性EPO也会损害软骨生成分化。此外，EPO可促进体外跖骨内皮细胞发芽。这与体内数据一致，即局部递送EPO可增加骨愈合中期（第14天）的血管生成。在小鼠股骨骨折模型中，EPO在第7天和第14天促进软骨痂形成，并在第28天通过改善X线评分和对新生骨再生微观结构的显微计算机断层扫描（micro-CT）分析来增强骨愈合，从而改善生物力学性能。我们的结果表明，EPO在骨修复过程中增强软骨生成和血管生成反应。EPO对软骨细胞增殖和分化的作用至少部分是由其受体EPOR介导的。EPO可能作为一种治疗剂来促进骨骼再生。
