Aghaloo Tara L, Amantea Christopher M, Cowan Catherine M, Richardson Jennifer A, Wu Ben M, Parhami Farhad, Tetradis Sotirios
Division of Diagnostic and Surgical Sciences, University of California at Los Angeles School of Dentistry, Room 53-068 CHS, 10833 Le Conte Avenue, Los Angeles, California 90095, USA.
J Orthop Res. 2007 Nov;25(11):1488-97. doi: 10.1002/jor.20437.
Oxysterols, naturally occurring cholesterol oxidation products, can induce osteoblast differentiation. Here, we investigated short-term 22(S)-hydroxycholesterol + 20(S)-hydroxycholesterol (SS) exposure on osteoblastic differentiation of marrow stromal cells. We further explored oxysterol ability to promote bone healing in vivo. Osteogenic differentiation was assessed by alkaline phosphatase (ALP) activity, osteocalcin (OCN) mRNA expression, mineralization, and Runx2 DNA binding activity. To explore the effects of osteogenic oxysterols in vivo, we utilized the critical-sized rat calvarial defect model. Poly(lactic-co-glycolic acid) (PLGA) scaffolds alone or coated with 140 ng (low dose) or 1400 ng (high dose) oxysterol cocktail were implanted into the defects. Rats were sacrificed at 6 weeks and examined by three-dimensional (3D) microcomputed tomography (microCT). Bone volume (BV), total volume (TV), and BV/TV ratio were measured. Culture exposure to SS for 10 min significantly increased ALP activity after 4 days, while 2 h exposure significantly increased mineralization after 14 days. Four-hour SS treatment increased OCN mRNA measured after 8 days and nuclear protein binding to an OSE2 site measured after 4 days. The calvarial defects showed slight bone healing in the control group. However, scaffolds adsorbed with low or high-dose oxysterol cocktail significantly enhanced bone formation. Histologic examination confirmed bone formation in the defect sites grafted with oxysterol-adsorbed scaffolds, compared to mostly fibrous tissue in control sites. Our results suggest that brief exposure to osteogenic oxysterols triggered events leading to osteoblastic cell differentiation and function in vitro and bone formation in vivo. These results identify oxysterols as potential agents in local and systemic enhancement of bone formation.
氧化甾醇是天然存在的胆固醇氧化产物，能够诱导成骨细胞分化。在此，我们研究了短期暴露于22(S)-羟基胆固醇 + 20(S)-羟基胆固醇（SS）对骨髓基质细胞成骨分化的影响。我们还进一步探究了氧化甾醇在体内促进骨愈合的能力。通过碱性磷酸酶（ALP）活性、骨钙素（OCN）mRNA表达、矿化作用以及Runx2 DNA结合活性来评估成骨分化。为了探究成骨氧化甾醇在体内的作用，我们采用了临界大小的大鼠颅骨缺损模型。将单独的聚乳酸-乙醇酸共聚物（PLGA）支架或涂有140 ng（低剂量）或1400 ng（高剂量）氧化甾醇混合物的支架植入缺损处。在6周时处死大鼠，并通过三维（3D）微型计算机断层扫描（microCT）进行检查。测量骨体积（BV）、总体积（TV）以及BV/TV比值。培养物暴露于SS 10分钟后，4天显著增加了ALP活性，而暴露2小时后，14天显著增加了矿化作用。4小时的SS处理增加了8天后测得的OCN mRNA以及4天后测得的与OSE2位点结合的核蛋白。对照组的颅骨缺损显示出轻微的骨愈合。然而，吸附有低剂量或高剂量氧化甾醇混合物的支架显著增强了骨形成。组织学检查证实，与对照部位主要为纤维组织相比，植入氧化甾醇吸附支架的缺损部位有骨形成。我们的结果表明，短暂暴露于成骨氧化甾醇会引发一系列事件，导致体外成骨细胞分化和功能以及体内骨形成。这些结果表明氧化甾醇是局部和全身增强骨形成的潜在药物。
