低氧诱导因子-1α在骨形成过程中对成骨细胞功能的调控

目的探讨低氧诱导因子（HIF）-1α对成骨细胞功能的调控及其在骨形成过程中的作用。方法应用Cre-Loxp重组酶技术,在体内外条件性敲除成骨细胞中的HIF-1α基因及其上游调控VHL基因,在体外将成骨细胞在2％氧浓度培养48h后检测血管内皮生长因子（VEGF）、核结合因子a1（RunX2）、碱性磷酸酶（ALP）和骨钙素（OC）的表达,在体内取3个月龄小鼠股骨远端骨组织,应用组织切片和Micro-CT方法检测骨组织形态计量学指标和骨矿密度（BMD）。结果体外条件性敲除成骨细胞中的HIF-1α基因后,由于HIF-1α的表达下降导致VEGF、RunX2、ALP、OC的表达水平降低,而敲除VHL基因后由于HIF-1α的表达上调导致上述基因的表达升高。体内条件性敲除HIF-1α基因小鼠骨组织形态计量学指标和BMD均劣于野生型小鼠,而体内条件性敲除VHL基因小鼠以上指标均优于野生型小鼠。结论在生理和病理条件下,由于低氧环境的存在,HIF-1α能够通过促进成骨细胞的功能而调控骨形成过程。

Regulation of hypoxia inducible factor-1alpha on osteoblast function in osteogenesis

OBJECTIVE: To explore the regulation of hypoxia inducible factor-1alpha (HIF-1alpha) on osteoblast function in osteogenesis. METHODS: Skull-cap bone of HIF-1alpha Loxp/Loxp and VHL Loxp/Loxp C57/BL6 mice were taken out and cultured so as to obtain osteoblasts which were infected with the recombinant adenovirus Ad-Cre so as to conditionally knock out the HIF-1alpha gene and its up-stream gene for von Hippel-Lindau disease (VHL) using Cre-Loxp recombinase technique. Then the osteoblasts were cultured under 2% O2 for 48 hours. Real-time PCR and Western-blotting were used to detect the mRNA and protein expression of vascular endothelial growth factor (VEGF), core binding factor al (RunX2), alkaline phosphatase (ALP) and osteocalcin (OC). Transgenic FVB mice mated with C57/BL6 mice with both HIF-1alpha and VHL alleles to obtain the mice with the osteoblasts with the HIF-1alpha and VHL genes conditionally knocked-out. At the age of 3 months the distal femurs of HIF-1alpha/VHL conditionally knocked-out mice and wild type mice were obtained to undergo hematoxylin-eosin staining and micro-CT to evaluate the bone histomorphometry and bone mineral density (BMD). RESULTS: The mRNA and protein expressions of VEGF, RunX2, ALP, and OC of the HIF-1alpha conditionally knocked-out osteoblasts were all decreased and the mRNA and protein expressions of VEGF, RunX2, ALP, and OC of the VHL conditionally knocked-out osteoblasts were all increased. The values of bone histomorphometry and bone mineral density (BMD) of the HIF-1alpha conditionally knocked-out mice were both significantly lower than those of the wild-type mice, whereas the values of bone histomorphometry and BMD of the VHL conditionally knocked-out mice were both significantly higher than those of the wild-type mice (all P < 0.01). CONCLUSION: Under both the physiological and pathological hypoxia environment in bone tissues HIF-1alpha can promote the bone formation ability of osteoblast.