Expression of estrogen receptors alfa and beta mRNA and alkaline phosphatase in the differentiation of osteoblasts from elderly postmenopausal women: comparison with osteoblasts from osteosarcoma cell lines.
OBJECTIVE
To evaluate the expression of estrogen receptors (ER) alpha and beta, and activity of alkaline phosphatase during differentiation of primary osteoblast cells (hOB) from aged postmenopausal women and human osteosarcoma cell lines (HOS, MG63).


METHODS
Osteoblast cultures were prepared from the upper femur of postmenopausal patients (age, 60-74 years) and HOS. At the indicated times (days 5, 10, 15, 20, and 25), alkaline phosphatase activity and expression of ERalpha and ERbeta mRNA were evaluated.


RESULTS
In both cultures of primary hOB and HOS, alkaline phosphatase activity decreased at the osteoblast proliferation stage, whereas it subsequently increased at the matrix maturation stage. ER beta mRNA was strongly expressed in HOS on day 15 and remained at high levels of transcription through to day 25 (matrix maturation phase), whereas ERalpha mRNA was barely detectable during osteoblast differentiation. In hOB, transcription of ERalpha mRNA was much stronger than that of ERbeta mRNA.


CONCLUSIONS
The presence of ERalpha and ERbeta mRNA in osteoblasts supports the involvement of estrogen in human bone formation. The developmental expression of alkaline phosphatase was not correlated to ER mRNA expression during osteoblast differentiation. ER isoforms may have different functions or interact with each other during osteoblast differentiation. Since the expression of ER isoforms is different between postmenopausal women and osteosarcoma cell lines, characteristics of osteosarcoma cell lines may not be suitable as a model for the evaluation of estrogen effects on postmenopausal osteoporosis.
Chen
Fang-Ping
FP
Department of Obstetrics and Gynecology, Keelung Chang Gung Memorial Hospital and Chang Gung University, Keelung, Taiwan. fangping@cgmh.org.tw
Hsu
Todd
T
Hu
Chin-Hwa
CH
Wang
Wen-Der
WD
Wang
Kun-Chuang
KC
Teng
Li-Fen
LF
D000368:Aged; D000469:Alkaline Phosphatase / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology*; D045744:Cell Line, Tumor; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D047629:Estrogen Receptor beta / Q000378:metabolism*; D005260:Female; D005269:Femur / Q000166:cytology; D006801:Humans; D008875:Middle Aged; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D012516:Osteosarcoma / Q000378:metabolism / Q000473:pathology; D017698:Postmenopause / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D012333:RNA, Messenger; D000469:Alkaline Phosphatase