title: Effects of 17-α ethynyl estradiol on proliferation, differentiation & mineralization of osteoprecursor cells.
abstract: OBJECTIVE
  The steroidal estrogen 17α-ethynyl estradiol (EE) is an orally bio-active estrogen used in almost all modern formulations of estrogen-progestin combination preparations of oral contraceptives. Contrasting effects of treatment with combined oral contraceptives on bone mineral density of pre-, peri-, and post-menopausal women have been reported, and it has been suggested that the estrogen dose and the type of progestogen may be the main contributing factors for these contrasting results. The objective of this study was to evaluate the effects of EE on osteoprecursor cells.
  
  
  METHODS
  The effects of single component of oral contraceptive, EE, were tested to see the relationship between EE and osteoblast proliferation, differentiation and mineralization. Tests used included a cell viability test, alkaline phosphatase (ALP) test, alizarin red-S staining, and a Western blot analysis. The effect on cell viability was determined by MTT assay. Differentiation and mineralization were examined using an ALP test and alizarin red-S staining. Protein expressions related to bone formation, such as estrogen receptor-alpha (ER-α), estrogen receptor-beta (ER-β), bone morphogenetic protein-2 (BMP-2), osteocalcin (OCN), and osteopontin (OPN) were evaluated by using a Western blot analysis.
  
  
  RESULTS
  Cultures growing in the absence of EE presented the lowest value for the MTT value. However, there were no significant changes in viability/proliferation when EE was added in the medium. Cultures growing in the absence of EE presented the highest value for the ALP activity, and the additional presence of EE resulted in dose-dependent decrease concerning ALP activity.
  
  
  CONCLUSIONS
  Our finding showed that EE in tested dosage within MC3T3-E1 cells seem to affect the proliferation and differentiation; however, significant differences are achieved in ALP activity in early differentiation phase and further studies are needed to elucidate the mechanisms of EE on bone.
authors.affiliation: Department of Periodontics, Seoul St Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea. jbassoonis@yahoo.co.kr
authors.forename: Jun-Beom
authors.initials: JB
authors.lastname: Park
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002113:Calcification, Physiologic / Q000187:drug effects*; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004997:Ethinyl Estradiol / Q000494:pharmacology*; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects*; D053495:Osteopontin / Q000502:physiology
chemical_list: D053495:Osteopontin; D004997:Ethinyl Estradiol; D000469:Alkaline Phosphatase