title: Aberrant CpG islands' hypermethylation of ABCB1 in mesenchymal stem cells of patients with steroid-associated osteonecrosis.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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).
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  These data suggest that aberrant CpG islands' hypermethylation of ABCB1 gene may be responsible for individual differences in the development of GC-associated ONFH.
authors.affiliation: From the Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
authors.forename: Zhibo
authors.initials: Z
authors.lastname: Sun
authors.forename: Shuhua
authors.initials: S
authors.lastname: Yang
authors.forename: Shunan
authors.initials: S
authors.lastname: Ye
authors.forename: Yukun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Weihua
authors.initials: W
authors.lastname: Xu
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.forename: Xianzhe
authors.initials: X
authors.lastname: Liu
authors.forename: Fengbo
authors.initials: F
authors.lastname: Mo
authors.forename: Wenbin
authors.initials: W
authors.lastname: Hua
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D000328:Adult; D000368:Aged; D002470:Cell Survival; D018899:CpG Islands / Q000235:genetics*; D019175:DNA Methylation; D005260:Female; D005271:Femur Head Necrosis / Q000139:chemically induced / Q000235:genetics* / Q000378:metabolism; D005938:Glucocorticoids / Q000009:adverse effects*; D006801:Humans; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D008875:Middle Aged; D018384:Oxidative Stress / Q000502:physiology; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: C513055:ABCB1 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D005938:Glucocorticoids; D017382:Reactive Oxygen Species
keywords: ABCB1; HYPERMETHYLATION; MESENCHYMAL STEM CELLS; STEROID-ASSOCIATED OSTEONECROSIS