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Functional estrogen receptors in a human preosteoclastic cell line
G Fiorelli1, F Gori, M Petilli
1Department of Clinical Physiopathology, University of Florence, Italy.
Summary
Estrogen (17 beta E2) may directly impact osteoclast function by binding to estrogen receptors (ERs) on preosteoclastic cells. This suggests a potential direct role for estrogen in regulating bone resorption and osteoclastogenesis.
Area of Science:
- Endocrinology
- Bone Biology
- Cell Biology
Background:
- The effect of estrogen (17 beta E2) on bone is primarily to reduce bone resorption.
- It remains unclear whether estrogen directly influences osteoclast function or acts indirectly through osteoblasts.
Purpose of the Study:
- To investigate the presence and function of estrogen receptors (ERs) in human preosteoclastic cells (FLG 29.1).
- To determine if estrogen directly affects osteoclastogenesis.
Main Methods:
- Reverse transcription-PCR and Southern blotting to detect ER mRNA.
- Radioligand binding assays to quantify nuclear ERs.
- SDS-PAGE and Western blotting to characterize ERs.
- Assays for progesterone receptor induction, cell proliferation, and reporter gene activity (chloramphenicol acetyltransferase) following estrogen treatment.
Main Results:
- FLG 29.1 cells express functional estrogen receptors (ERs), with approximately 400 high-affinity binding sites per nucleus.
- Estrogen treatment induced progesterone receptor expression and reduced cell proliferation in a dose- and time-dependent manner.
- Estrogen significantly increased reporter gene expression, indicating transcriptional activity mediated by ERs.
Conclusions:
- Human preosteoclastic cells possess functional estrogen receptors.
- Estrogen can directly influence osteoclast-like cells, suggesting a potential role in regulating osteoclastogenesis and bone resorption.