Biomedical Engineering Program, University of South Carolina, Columbia, SC 29208, USA.
Tissue Eng Part A. 2013 Jul;19(13-14):1583-91. doi: 10.1089/ten.TEA.2012.0378. Epub 2013 Apr 4.
Tissue engineering is a promising approach to repair critical-size defects in bone. Damage to vasculature at the defect site can create a lower O2 environment compared with healthy bone. Local O2 levels influence stem cell behavior, as O2 is not only a nutrient, but also a signaling molecule. The hypoxia-inducible factor-1 (HIF-1) is a transcription factor that regulates a wide range of O2-related genes and its contribution in bone repair/formation is an important area that can be exploited. In this study, we examined the effect of low O2 environments (1% and 2% O2) on the osteogenic differentiation of adipose-derived stem cells in both two-dimensional (2-D) and three-dimensional (3-D) culture systems. To determine the role of HIF-1 in the differentiation process, an inhibitor was used to block the HIF-1 activity. The samples were examined for osteogenesis markers as measured by quantification of the alkaline phosphatase (ALP) activity, mineral deposition, and expression of osteonectin (ON) and osteopontin (OPN). Results show a downregulation of the osteogenic markers (ALP activity, mineralization, ON, OPN) in both 1% and 2% O2 when compared to 20% O2 in both 2-D and 3-D culture. Vascular endothelial growth factor secretion over 28 days was significantly higher in low O2 environments and HIF-1 inhibition reduced this effect. The inhibition of the HIF-1 activity did not have a significant impact on the expression of the osteogenic markers, suggesting HIF-1-independent inhibition of osteogenic differentiation in hypoxic conditions.
组织工程是修复骨临界尺寸缺陷的一种很有前途的方法。与健康骨相比，缺损部位的血管损伤会导致更低的 O2 环境。局部 O2 水平影响干细胞行为，因为 O2 不仅是一种营养物质，也是一种信号分子。缺氧诱导因子-1（HIF-1）是一种转录因子，可调节广泛的与 O2 相关的基因，其在骨修复/形成中的作用是一个可以开发的重要领域。在这项研究中，我们研究了低 O2 环境（1%和 2% O2）对脂肪来源干细胞在二维（2-D）和三维（3-D）培养系统中的成骨分化的影响。为了确定 HIF-1 在分化过程中的作用，使用抑制剂阻断 HIF-1 活性。通过定量测定碱性磷酸酶（ALP）活性、矿物质沉积以及骨桥蛋白（ON）和骨黏蛋白（OPN）的表达来检测成骨标志物。结果表明，与 20% O2 相比，1%和 2% O2 下 2-D 和 3-D 培养中的成骨标志物（ALP 活性、矿化、ON、OPN）的表达均下调。28 天内皮细胞生长因子分泌在低 O2 环境中显著增加，HIF-1 抑制降低了这种作用。HIF-1 活性的抑制对成骨标志物的表达没有显著影响，这表明在低氧条件下成骨分化的抑制是 HIF-1 非依赖性的。
