PAGETIC OSTEOCLASTS FORMED IN-VITRO - ABSENCE OF PARACRYSTALLINE INCLUSIONS

In Paget's disease of bone, osteoclasts are increased in number and si ze and contain intracellular paramyxoviral-like inclusions which cross -react with antibody against measles, respiratory syncytial, and canin e distemper viral nucleocapsid antigens. Moreover, measles virus nucle ocapsid transcripts are present in pagetic osteoclasts and their monon uclear precursors formed in vitro. The present study was undertaken to morphologically assess pagetic osteoclasts formed in culture; special attention has been directed towards the ultrastructural identificatio n of nuclear and cytoplasmic inclusions. Pagetic osteoclasts were prod uced in long-term cultures of non-adherent bone marrow mononuclear cel ls derived from involved bone of patients with Pager's disease. These cultured osteoclasts had many of the ultrastructural features of paget ic osteoclasts in vivo. Of interest, no viral-like inclusions were obs erved in either the multinucleated osteoclasts or mononuclear cell pre cursors in these cultures. These data suggest that other factors in th e bone microenvironment are required for viral nucleocapsid formation in pagetic osteoclasts.