From the Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
J Rheumatol. 2013 Nov;40(11):1913-20. doi: 10.3899/jrheum.130191. Epub 2013 Sep 15.
Patients carrying an ABCB1 polymorphism have a higher risk of developing osteonecrosis of the femoral head (ONFH). We investigated whether aberrant dinucleotide CpG islands' hypermethylation of ABCB1 gene existed in mesenchymal stem cells (MSC) of patients with ONFH, which results in cell dysfunction.
Bone marrow was collected from the proximal femur of patients with glucocorticoid (GC)-associated ONFH (n = 22) and patients with new femoral neck fractures (n = 25). MSC were isolated by density gradient centrifugation. We investigated cell viability, intracellular reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP), the amount of P-glycoprotein (P-gp) and ABCB1 transcripts, and methylation at CpG islands of ABCB1 promoter from both the femoral neck fractures group and the GC-associated ONFH group treated with or without the DNA methyltransferase inhibitor, 5'-Aza-2-deoxycytidine (5'-Aza-dC).
We observed that MSC from GC-associated ONFH groups showed reduced proliferation ability, elevated ROS levels, and depressed MMP when compared with the other 2 groups. Low levels of P-gp and ABCB1 transcript, as well as ABCB1 gene hypermethylation, in patients with GC-associated ONFH were also noted. Treatment with 5'-Aza-dC rapidly restored ABCB1 expression. Analysis of general expression revealed that aberrant CpG islands' hypermethylation of ABCB1 caused sensitivity to GC and induced changes in the proliferation and oxidative stress of MSC under GC administration.
These data suggest that aberrant CpG islands' hypermethylation of ABCB1 gene may be responsible for individual differences in the development of GC-associated ONFH.
携带 ABCB1 多态性的患者发生股骨头坏死（ONFH）的风险较高。我们研究了骨髓间充质干细胞（MSC）中 ABCB1 基因异常二核苷酸 CpG 岛超甲基化是否存在，这导致细胞功能障碍。
从糖皮质激素（GC）相关 ONFH（n = 22）和新股骨颈骨折患者（n = 25）的近端股骨中采集骨髓。通过密度梯度离心分离 MSC。我们研究了细胞活力、细胞内活性氧（ROS）水平、线粒体膜电位（MMP）、P-糖蛋白（P-gp）和 ABCB1 转录物的含量，以及来自股骨颈骨折组和 GC 相关 ONFH 组的 MSC 的 ABCB1 启动子 CpG 岛的甲基化，这些组分别用或不用 DNA 甲基转移酶抑制剂 5'-Aza-2-脱氧胞苷（5'-Aza-dC）处理。
与其他 2 组相比，我们观察到来自 GC 相关 ONFH 组的 MSC 增殖能力降低、ROS 水平升高、MMP 降低。GC 相关 ONFH 患者的 P-gp 和 ABCB1 转录本水平较低，ABCB1 基因也发生了超甲基化。用 5'-Aza-dC 处理可迅速恢复 ABCB1 表达。一般表达分析表明，ABCB1 基因异常 CpG 岛超甲基化导致对 GC 的敏感性，并在 GC 给药下诱导 MSC 的增殖和氧化应激变化。
这些数据表明，ABCB1 基因异常 CpG 岛超甲基化可能是导致 GC 相关 ONFH 发展个体差异的原因。
