Estrogen Binding, Receptor mRNA, and Biologic Response in Osteoblast-Like Osteosarcoma Cells

TLDR

The study used iodine‑125–labeled estradiol to identify approximately 200 high‑affinity nuclear binding sites in rat and human osteoblast‑like osteosarcoma cells. Only testosterone cross‑reacted with estrogen binding, while 6–6.2 kb receptor transcripts were detected in both cell types, and 1 nM estradiol increased type I procollagen and TGF‑β mRNA, demonstrating that estrogen directly modulates extracellular matrix components through a receptor‑mediated mechanism.

Abstract

High specific activity estradiol labeled with iodine-125 was used to detect approximately 200 saturable, high-affinity (dissociation constant ≅ 1.0 n M ) nuclear binding sites in rat (ROS 17/2.8) and human (HOS TE85) clonal osteoblast-like osteosarcoma cells. Of the steroids tested, only testosterone exhibited significant cross-reactivity with estrogen binding. RNA blot analysis with a complementary DNA probe to the human estrogen receptor revealed putative receptor transcripts of 6 to 6.2 kilobases in both rat and human osteosarcoma cells. Type I procollagen and transforming growth factor-β messenger RNA levels were enhanced in cultured human osteoblast-like cells treated with 1 n M estradiol. Thus, estrogen can act directly on osteoblasts by a receptor-mediated mechanism and thereby modulate the extracellular matrix and other proteins involved in the maintenance of skeletal mineralization and remodeling.