A New Method to Isolate Large Numbers of Rabbit Osteoclasts and Osteoclast-like Cells: Application to the Characterization of Serum Response Element Binding Proteins During Osteoclast Differentiation

Abstract

We have developed a new method that allows the purification of large numbers of both authentic osteoclasts (OCs) and in vitro differentiated osteoclast‐like cells (OCLs) from rabbits. We characterized the OCLs in terms of the expression of different phenotypic markers of OC differentiation and their ability to resorb bone. The method provides a system for performing biochemical and molecular studies of OC differentiation and function in a single species. We used this system to characterize the effect of 1,25‐dihydroxyvitamin D₃ (1,25(OH)₂D₃) on the expression of proteins that bind to the serum response element (SRE) of the c‐fos promoter. We found that OCLs and OCs displayed similar SRE‐binding activities, including the serum response factor (SRF). This pattern is established in a time‐dependent and cell‐specific manner in response to long‐term treatment of rabbit bone marrow by 1,25(OH)₂D₃. Thus, 1,25(OH)₂D₃ can modulate SRF and/or SRF‐related protein. This finding may contribute to understanding the role of c‐Fos in the regulation of OC differentiation.