title: Effects of mechanical strain on oxygen free radical system in bone marrow mesenchymal stem cells from children.
abstract: BACKGROUND
  Physiological loading is widely believed to be beneficial in maintaining skeletal integrity by stimulating new bone formation through increases in osteoblastic activity and concomitant decreases in osteoclastic activity. However, excessive or nonphysiological loading is associated with bone injuries, including stress fractures and osteoporotic fractures, thereby leading to a decreased functional capacity of bone. It is known that the excessive generation of reactive oxygen species (ROS) is a significant factor underlying tissue injury observed in many disease states. The aim of this study was to study the effects of mechanical strain on oxygen free radical system [ROS, superoxide dismutase (SOD) and malondialdehyde (MDA)] in bone marrow mesenchymal stem cells (MSCs) from children.
  
  
  METHODS
  To determine whether extreme levels of mechanical strain enhance ROS synthesis, we loaded cyclic tensile stretch of varying magnitude on MSCs. After MSCs were stimulated by mechanical strain, ROS labelled with 2,7-dichlorodihydrofluorescein (DCFH) fluorescent probe in cells were detected by flow cytometry (FCM) whilst SOD activity and MDA level were detected by xanthine oxidase method and thiobarbituric acid method, respectively.
  
  
  RESULTS
  Extreme levels (>12%) of mechanical strain applied to children's MSCs enhanced ROS synthesis, decreased the activity of SOD and increased the level of MDA, in a time- and magnitude-dependent fashion.
  
  
  CONCLUSIONS
  These data suggest that excessive magnitude of cyclic tensile strain (>12%) could induce oxygen free radical disequilibrium, resulting in cytotoxicity. The findings may have clinical implications for orthopaedic practice.
authors.affiliation: Department of Orthopaedics and Traumatology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China.
authors.forename: Runguang
authors.initials: R
authors.lastname: Li
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.forename: Gang
authors.initials: G
authors.lastname: Wang
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.forename: Gaohong
authors.initials: G
authors.lastname: Ren
authors.forename: Guoxin
authors.initials: G
authors.lastname: Ni
mesh_terms: D001842:Bone and Bones / Q000293:injuries / Q000378:metabolism; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism*; D045164:Mesenchymal Stem Cell Transplantation / Q000379:methods; D059630:Mesenchymal Stem Cells / Q000378:metabolism*; D010027:Osteotomy; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013314:Stress, Mechanical; D013482:Superoxide Dismutase / Q000096:biosynthesis*; D016474:Weight-Bearing / Q000502:physiology; D014945:Wound Healing / Q000502:physiology*
chemical_list: D017382:Reactive Oxygen Species; D008315:Malondialdehyde; D013482:Superoxide Dismutase