Activated platelets retain their potential to induce osteoclast-like cell formation in murine bone marrow cultures

Supernatants immediately obtained after platelet activation can induce osteoclast-like cell formation in murine bone marrow cultures. Here we report that activated platelets retain their potential to induce osteoclast-like cell formation over a 3-day period with repeated washing, when co-cultured with murine bone marrow cells. Supernatants obtained from washed platelets 3 days following their activation with thrombin, caused the differentiation of haematopoietic progenitors into osteoclast-like cells. The platelet-derived soluble factor(s) responsible for the induction of osteoclastogenesis can be retained in an ultrafilter with a nominal molecular weight limit of 10 kDa, and loose their activity when incubated at 99 degrees C. Indomethacin, which inhibits cyclooxygenase activity, and osteoprotegerin, a decoy receptor for receptor activator of nuclear factor-kappaB ligand (RANKL), suppressed the formation of osteoclast-like cells in this model. The in vitro findings presented here suggest that activated platelets can induce osteoclast-like cell formation via a prostaglandin and RANKL-dependent mechanism over a time period corresponding to the existence of a blood clot.