Expression of the vitamin D receptor, of estrogen and thyroid hormone receptor alpha- and beta-isoforms, and of the androgen receptor in cultures of native mouse bone marrow and of stromal/osteoblastic cells

Marrow stromal cells mediate the effect of 1 alpha,25-dihydroxyvitamin D-3 on formation of osteoclast-like cells from undifferentiated hematopoetic pr ecursors in bone marrow. Induction by the vitamin D hormone of multinucleat ed, calcitonin receptor- and tartrate-resistant acid phosphatase-positive c ells in primary mouse bone marrow culture can be modulated by other members of the steroid/thyroid hormone family, such as triiodothyronine, which has a positive effect, as well as 17 beta-estradiol and 5 alpha-dihydrotestost erone, which both act as inhibitors of osteoclastogenesis, In an attempt to relate these effects of the steroid/thyroid hormones to the presence of th eir respective nuclear receptors, we studied expression of the vitamin D re ceptor (VDR), estrogen receptor (ER)-alpha and -beta, thyroid hormone recep tor (TR)-alpha and -beta, and androgen receptor (AR) in total bone marrow a s well as primary marrow stromal cell cultures. By using reverse-transcript ase-polymerase chain reaction, in both cases amplification products were ob tained, which were identified by multiple restriction fragment length analy sis as transcripts from mRNA specific for the ligand-binding domains of the VDR, ER-alpha, ER-beta, TR-alpha, TR-beta, and AR. Specific immunostaining by indirect peroxidase labeling revealed that among the various cell types present in bone marrow, the steroid! thyroid hormone receptors are abundan t particularly in marrow stromal cells. In another series of experiments, w e extended our survey on receptor expression also to stromal/osteoblastic c ell lines. At the mRNA level, the complete repertoire of steroid/thyroid ho rmone receptors was present in preadipocytic ST2 cells as well as in osteob lastic MC3T3-E1 cells. By immunocytochemical staining of the latter, it bec ame apparent that single cells exhibit wide variations in intensity of spec ific signals for all the receptors investigated, so that, notably in contra st to primary stromal cells and ST2 cells, MC3T3-E1 display a mosaic patter n of receptor protein expression. (C) 1999 by Elsevier Science Inc. All rig hts reserved.