Androgen-induced mineralization by MC3T3-E1 osteoblastic cells reveals a critical window of hormone responsiveness.
Despite their clinical importance for skeletal growth and homeostasis, the actions of androgens on osteoblastic cells are not well understood. MC3T3-E1 cells, a nontransformed murine preosteoblastic cell line, that traverse the stages of osteoblastic differentiation within 30 days in vitro, were exposed to mibolerone (an androgen receptor (AR) agonist) or 5alpha-dihydroxytestosterone (DHT) from days 3 to 30 post-plating. Cells exposed to this hormonal regimen exhibited a significant increase in mineralization (calcium deposition) compared to vehicle-treated cells. Delaying treatment for 4-11 days (treatment still completed on day 30 post-plating) enhanced mineralization further. Within 2 days post-plating, AR protein increased 7.2-fold in androgen-treated cells and 2.5-fold in vehicle-treated cells. MC3T3-E1 cells transfected with an androgen- and glucocorticoid-responsive reporter construct on day 1 post-plating followed by a 2 day exposure to DHT, mibolerone, or dexamethasone (dex; a glucocorticoid receptor agonist) exhibited reporter gene activation only with dex treatment. In contrast, delaying transfection and treatment for at least 1 day resulted in comparable androgen- and dex-mediated reporter gene transactivation. Therefore, the ability of MC3T3-E1 cells to respond to androgens is dependent on the timing of androgen administration.
Balkan
Wayne
W
Geriatric Research, Education, and Clinical Center and Research Service, Veterans Affairs Medical Center, Miami, FL, USA. wbalkan@miami.edu
Burnstein
Kerry L
KL
Schiller
Paul C
PC
Perez-Stable
Carlos
C
D'Ippolito
Gianluca
G
Howard
Guy A
GA
Roos
Bernard A
BA
D016475:3T3 Cells; D000222:Adaptation, Physiological / Q000187:drug effects / Q000502:physiology; D059002:Androgen Receptor Antagonists; D000728:Androgens / Q000494:pharmacology*; D000818:Animals; D002113:Calcification, Physiologic / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D051379:Mice; D009277:Nandrolone / Q000031:analogs & derivatives* / Q000494:pharmacology; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D011944:Receptors, Androgen / Q000378:metabolism*; D013739:Testosterone / Q000494:pharmacology*
D059002:Androgen Receptor Antagonists; D000728:Androgens; D011944:Receptors, Androgen; D013739:Testosterone; D009277:Nandrolone; C100075:mibolerone