Regucalcin stimulates osteoclast‐like cell formation in mouse marrow cultures

AbstractThe effect of regucalcin, a regulatory protein in intracellular signaling, on osteoclastic cell formation in mouse bone marrow culture is investigated. The bone marrow cells were cultured for 7 days in an α‐minimal essential medium containing either vehicle or regucalcin (10−10–10−8M). Osteoclast‐like cell formation was estimated by staining for tartrate‐resistant acid phosphatase (TRACP), a marker enzyme of osteoclasts. The presence of regucalcin (10−10–10−8M) caused a remarkable increase in osteoclast‐like multinucleated cells (MNCs). The effect of regucalcin in stimulating osteoclast‐like cell formation was significantly inhibited in the presence of calcitonin (CT; 10−9M), 17β‐estradiol (10−9M), β‐cryptoxanthin (CX; 10−6M), or zinc sulfate (10−4M), which is an anti‐bone resorbing factor. The effect of regucalcin on osteoclast‐like cell formation was not significantly blocked in the presence of cycloheximide, an inhibitor of protein synthesis, or 5,6‐dichloro‐1‐β‐D‐ribofuranosylbenzimidazole (DRB), an inhibitor of transcriptional activity. The effect of parathyroid hormone (10−7M), 1,25‐dihydroxyvitamin D3 (10−7M), prostaglandin E2 (10−5M), or tumor necrosis factor‐α (10