MYELOBLASTIC CELL-LINE EXPRESSES OSTEOCLASTIC PROPERTIES FOLLOWING COCULTURE WITH MARROW STROMAL ADIPOCYTES

Osteoclasts are derived from hemopoietic precursors in the marrow. The ir differentiation pathway is still undefined, but an important role w as observed for the marrow microenvironment in the regulation of osteo clasto-genesis. Various marrow stromal cell subtypes were used to stud y their possible role in the formation of osteoclasts from myeloblast (M1) cells. Interactions between M1 cells and the 14F1.1 endothelial-a dipocyte stromal cell line were demonstrated in a coculture model. M1 cells attached to the adherent layer of 14F1.1 cells and formed distin ct foci reminiscente of ''cobblestone areas.'' Following these interac tions, M1 cells developed specific enzymatic activities and became mul tinucleated. Both mononuclear and multinuclear M1 cells became positiv e to tartrate-resistant acid phosphatase (TRaP) and ATPase, a feature characteristic of osteoclasts, and were also responsive to calcitonin. Furthermore, they attached to mineralized bone particles and their me mbrane changed into a ruffled border at the zone of interaction with t he bone matrix. We thus demonstrated that marrow endothelial-adipocyte s may play a role in regulating the differentiation of myeloblasts int o osteoclasts. (C) 1994 Wiley-Liss, Inc.