Aromatase expression of human osteoblast-like cells

Area of Science:

• Endocrinology
• Bone Biology
• Cell Biology

Background:

• Estrogen is crucial for bone mineral homeostasis in both sexes.
• Extraglandular aromatization of androgens is a primary estrogen source in post-menopausal individuals and men.
• The role of bone cells as a local estrogen source requires further investigation.

Purpose of the Study:

• To investigate the capacity of osteoblast-like cells (OLCs) to produce estrogen.
• To characterize aromatase activity and expression in OLCs.
• To determine the specific aromatase gene promoters utilized by OLCs.

Main Methods:

• Osteoblast-like cells (OLCs) were isolated from human fetal bone.
• Aromatase activity was measured by estrone formation and tritium release assays.
• Thin layer chromatography (TLC) and 5' rapid amplification of cDNA ends (RACE) were used to confirm aromatase expression and promoter usage.

Main Results:

• OLCs demonstrated significant aromatase activity, confirmed by estrone formation and tritium release.
• Aromatase activity was higher in non-passaged OLCs and influenced by stimulants like dexamethasone (DEX) and IL-1beta.
• Promoter I.4 was identified as the major aromatase gene promoter in OLCs and fetal tibia, differing from other estrogen-producing tissues.

Conclusions:

• Human bone cells possess local estrogen-producing capacity via aromatase.
• Bone acts as an extraglandular source of estrogen, influencing bone mineral metabolism through autocrine and paracrine mechanisms.
• The specific promoter usage in OLCs highlights a unique regulatory mechanism compared to other tissues.