DEMONSTRATION OF ESTROGEN AND VITAMIN-D RECEPTORS IN BONE-MARROW-DERIVED STROMAL CELLS - UP-REGULATION OF THE ESTROGEN-RECEPTOR BY 1,25-DIHYDROXYVITAMIN-D(3)

We have shown earlier that 17beta-estradiol inhibits cytokine-induced interleukin-6 (IL-6) production by bone marrow-derived stromal cells a s well as osteoblasts, two types of cells with a critical influence on osteoclast development, and that ovariectomy causes an IL-6-mediated up-regulation of osteoclastogenesis in mice. Prompted by this, we have searched here for the presence of estrogen receptors (ERs) in two mur ine bone marrow-derived stromal cell lines, +/+ LDA11 and MBA 13.2, an d the osteoblast-like cell line MC3T3-E1. All three cell lines exhibit ed high affinity saturable binding for [I-125]17beta-estradiol with a dissociation constant of approximately 10(-10) m and concentration of binding sites of 260 +/- 30, 170 +/- 10, and 90 +/- 10 sites per cell, respectively. In addition, we amplified complementary DNA from the st romal cell lines by polymerase chain reaction using oligonucleotide pr imers flanking the DNA binding domain of the murine uterine ER. The am plified product showed an identical nucleotide sequence to the DNA bin ding domain of the murine uterine receptor. Consistent with the functi onality of the ER in stromal cells, and specifically its role in the r egulation of IL-6 by 17beta-estradiol, we found that the pure estrogen antagonist ICI 164,384 completely prevented the effect of 17beta-estr adiol on IL-6. All three cell lines also expressed receptors for 1,25- dihydroxy-vitamin-D3 [1,25(OH)2D3] (dissociation constant, approximate ly 10(-10) M), with a concentration of binding sites of 490 +/- 20, 92 0 +/- 20, and 1110 +/- 70 sites per cell, respectively. 1,25(OH)2D3 tr eatment of the stromal cells caused a 2-fold increase in the concentra tion of ERs and a decrease in cell proliferation. These data establish that bone marrow-derived stromal cells express functional estrogen as well as vitamin D receptors, which serve to mediate actions of their respective ligands on the biosynthetic activity of these cells and pre sumably the effects of these two steroid hormones on osteoclastogenesi s.