Laura Vollmer

Defense Date

7-6-2007

Graduation Date

Summer 2007

Availability

Immediate Access

Submission Type

thesis

Degree Name

MS

Department

Biological Sciences

Committee Chair

Kyle W. Selcer

Committee Member

Jana Patton-Vogt

Committee Member

Michael Jensen-Seaman

Keywords

androgens, glucocorticoids, sex steroids

Abstract

The importance of estrogen in bone regulation is exemplified by the rapid loss of bone density at the onset of menopause. Post-menopausal women have low levels of estrogens, but high levels of inactive sulfated steroids. These can be converted to active steroids by steroid sulfatase. While it is known that estrogens can stimulate the growth and maintenance of bone cells, it is not known if sulfated steroids can induce a similar response. The purpose of this study was to determine if sulfated steroids can induce proliferation of a human osteoblast-like cell line MG-63, and if steroid sulfatase inhibitors were capable of blocking that response. A growth assay was developed to assess proliferation of MG-63 cells in the presence of various steroids. The results of an initial experiment with a number of steroids indicated differences in growth, with estradiol, estrone sulfate, and dehydroepiandrosterone sulfate showing increased proliferation. A follow up experiment with estradiol, estrone sulfate, and dehydroepiandrosterone sulfate showed that proliferation was increased in the presence of estradiol and estrone sulfate. A dose-response testing proliferation of MG-63 cells to estradiol and estrone sulfate, resulted in estradiol stimulating growth above baseline at 10μM and 1μM, and estrone sulfate increasing growth only at 10μM. A steroid sulfatase inhibitor, DU-14, was able to block estrone sulfate-stimulated growth at 10μM, but not at 1μM. Another steroid sulfatase inhibitor, EMATE, actually stimulated growth at 1μM; however, this inhibitor is known to be estrogenic. The estrogen receptor antagonist ICI 182,780 inhibited estrone sulfate- and estradiol-stimulated growth at 100nM. Steroid sulfatase activity was assessed in MG-63 microsomes and whole cells in the presence of DU-14 and EMATE. It was found that steroid sulfatase activity in the presence of the inhibitors was virtually eliminated. These data demonstrate that growth in the human MG-63 osteoblast-like cells is stimulated by estrogens and by sulfated estrogens. This supports the concept that sulfated steroids are important in maintaining bone density.

Format

PDF

Language

English

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