Horm Metab Res 2012; 44(01): 47-53
DOI: 10.1055/s-0031-1291358
Original Basic
© Georg Thieme Verlag KG Stuttgart · New York

Estrogen Plus Estrogen Receptor Antagonists Alter Mineral Production by Osteoblasts In Vitro

O. Brennan
1   Department of Anatomy, Royal College of Surgeons in Ireland, Dublin, Ireland
2   Trinity Centre for Bioengineering, Trinity College Dublin, Dublin, Ireland
,
F. J. O’Brien
1   Department of Anatomy, Royal College of Surgeons in Ireland, Dublin, Ireland
2   Trinity Centre for Bioengineering, Trinity College Dublin, Dublin, Ireland
,
L. M. McNamara
3   Department of Mechanical and Biomedical Engineering, National University of Ireland, Galway, Ireland
› Author Affiliations
Further Information

Publication History

received 09 May 2011

accepted 11 October 2011

Publication Date:
28 November 2011 (online)

Abstract

In early postmenopausal women, estrogen withdrawal is associated with increased bone turnover leading to bone loss and increased risk of fracture. Recent studies have suggested that the remaining bone tissue is significantly stronger, stiffer and has an increased tissue-level mineral content. Such changes may occur to compensate for bone loss or as a direct result of estrogen deficiency. To date many details of the physiology of osteoblastic cells during estrogen deficiency are vague. In this study we test the hypothesis that osteoblastic matrix mineralisation is altered at the onset of estrogen deficiency. In vitro cell culture experiments were carried out up to 28 days to compare the mineral production of MC3T3-E1 osteoblastic cells subject to estrogen deficiency (fulvestrant), enhanced estrogen supplementation (17-β-estradiol) or a combination of both. Mineralisation was detected using von Kossa staining and was quantified with alizarin red absorbance readings. The expression of osteocalcin and osteopontin proteins, markers of osteoblast differentiation and mineralisation, was monitored using immunohistochemistry. Our results demonstrate that estrogen enhancement improves matrix mineralisation by MC3T3 cells in vitro. Furthermore this study found a significant reduction in the level of mineralisation when cells were treated with a combination of estrogen and fulvestrant. In an estrogen deficient environment mineralisation by osteoblastic cells was not altered. These findings suggest that altered tissue mineralisation following estrogen deficiency is not a direct result of estrogen deficiency on osteoblasts. Rather, we propose that altered tissue mineralisation may be a compensatory mechanism by bone to counter bone loss and reduced strength.

 
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