Expression of functional RANK on mature rat and human osteoclasts

Although the important roles of RANK/RANKL in osteoclastogenesis have been established, their roles in the regulation of mature osteoclasts remain unc ertain. Microisolation has been used to obtain pure populations of rat and human osteoclasts for RT-PCR analysis, RANK and calcitonin receptor mRNA wa s detected in all the samples whereas OPG and ALP mRNA was not present in a ny. RANKL mRNA,vas detected in two of eight rat and one of four human sampl es. Treatment of osteoclasts with soluble RANKL resulted in translocation o f NF-kappa B to the nucleus and elevation of cytosolic and nuclear calcium levels. We have shown that RANK is highly expressed in mature osteoclasts a nd that its stimulation by RANKL results in activation of NF-kappa B and ca lcium signalling. (C) 1999 Federation of European Biochemical Societies.