BONE-CELLS REQUIRED FOR OSTEOCLASTIC RESORPTION BUT NOT FOR OSTEOCLASTIC DIFFERENTIATION

It is generally considered that osteoblastic cells are essential for o steoclast formation. We tested the ability of hemopoietic tissue to di fferentiate osteoclastic characteristics in the absence of osteoblasti c cells. We found that large numbers of calcitonin-receptor positive ( CTRP) cells can be induced by prostaglandin E(2) and 1,25(OH)(2)vitami n D-3, in cultures of hemopoietic mouse spleen. Moreover, spleen strom al cells were equivalent to bone marrow stromal cells in CTRP-cell ind uction. The spleen CTRP cells did not resorb bone, but were rapidly in duced to full resorptive activity upon osteoblast addition. Thus, bone cells may not be essential for osteoclast formation, but rather are r equired to activate and regulate the resorptive function of mature ost eoclasts. (C) 1996 Academic Press, Inc.