title: The beneficial effect of icaritin on osteoporotic bone is dependent on the treatment initiation timing in adult ovariectomized rats.
abstract: BACKGROUND
  Epimedium-derived flavonoids (EFs) have a potential to treat established osteoporosis in postmenopausal women. However, one of the main disadvantages of the compound is the high volume and dosage during long-term administration period. Meanwhile, the beneficial effect of EFs on osteoporotic bone depends greatly on the intervention timing. Whether icaritin (ICT), an active molecular compound from EFs, can exert beneficial effect on osteoporotic bone and whether the beneficial effect is also dependent on the intervention timing remain unknown.
  
  
  OBJECTIVE
  The objective of this study was to evaluate the effect of the early and late ICT treatment on bone turnover markers, trabecular architecture, bone remodeling, biomechanics, colony formation of bone marrow stromal cells and osteoblast, adipocyte and osteoclast-related gene expression in adult ovariectomized rats.
  
  
  METHODS
  Eighty 9-month-old female rats (n=8/group) were sham-operated (Sham) or ovariectomized (OVX). The OVX rats were subjected to ICT treatment initiation at 1 month (early treatment) and 3 months (late treatment) post-operation, respectively. The vehicle-treated Sham and OVX rats starting at month 1 and month 3 post-operation served as the corresponding controls (Sham and OVX controls) for early and late ICT treatment, respectively. Those Sham and OVX rats sacrificed immediately before early and late ICT treatment served as the pretreatment baseline controls. Both ICT and vehicle treatments lasted for 2 months. The bone turnover markers, trabecular architecture, bone remodeling and bone biomechanical properties were analyzed with biochemistry, microCT, histomorphometry and mechanical testing, respectively. The population of bone marrow stromal cells (BMSCs) and osteoblasts were evaluated with colony formation assays, respectively. The expression levels of osteoblast, adipocyte and osteoclast-related genes in bone marrow were assessed by real-time polymerase chain reaction (PCR), respectively.
  
  
  RESULTS
  At the tissue level, early ICT treatment remarkably restored the trabecular bone mass, trabecular architecture and bone biomechanical properties towards pretreatment Sham levels, and significantly increased bone formation from pretreatment OVX level and markedly inhibited bone resorption towards pretreatment Sham level, whereas late ICT treatment failed to have any effect. At the cellular and molecular level, early ICT treatment significantly increased the number of osteoblastic colonies and the level of osteoblast-related gene expression compared to pretreatment OVX levels and remarkably decreased adipocyte and osteoclast-related gene expression towards pretreatment Sham levels. Late ICT treatment failed to have beneficial effect on any of these parameters.
  
  
  CONCLUSIONS
  ICT can exert anabolic and anti-resorptive effect on osteoporotic bone. The beneficial effect of ICT treatment is dependent on the intervention timing in established osteoporosis induced by estrogen depletion.
authors.affiliation: Department of Spine Surgery, Shenzhen People's Hospital, Jinan University Second College of Medicine, Shenzhen, China.
authors.forename: Songlin
authors.initials: S
authors.lastname: Peng
authors.forename: Ge
authors.initials: G
authors.lastname: Zhang
authors.forename: Bao-Ting
authors.initials: BT
authors.lastname: Zhang
authors.forename: Baosheng
authors.initials: B
authors.lastname: Guo
authors.forename: Yixin
authors.initials: Y
authors.lastname: He
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Bakker
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Pan
authors.forename: Wanxin
authors.initials: W
authors.lastname: Zhen
authors.forename: Leungkim
authors.initials: L
authors.lastname: Hung
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
authors.forename: Wing-Nang
authors.initials: WN
authors.lastname: Leung
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D000375:Aging / Q000473:pathology*; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001696:Biomechanical Phenomena / Q000187:drug effects; D001862:Bone Resorption / Q000188:drug therapy / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D001842:Bone and Bones / Q000187:drug effects / Q000473:pathology* / Q000503:physiopathology; D002454:Cell Differentiation / Q000187:drug effects; D005260:Female; D005419:Flavonoids / Q000494:pharmacology / Q000627:therapeutic use*; D005786:Gene Expression Regulation / Q000187:drug effects; D059630:Mesenchymal Stem Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010010:Osteoclasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010012:Osteogenesis / Q000187:drug effects / Q000235:genetics; D010024:Osteoporosis / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D015415:Biomarkers; D005419:Flavonoids; C499403:icaritin