Human bone-derived cells support formation of human osteoclasts from arthroplasty-derived cells in vitro

Mononuclear osteoclast precursors are present in the wear-particle-associat ed macrophage infiltrate found in the membrane surrounding loose implants. These cells are capable of differentiating into osteoclastic bone-resorbing cells when co-cultured with the rat osteoblast-like cell line, URIR 106, i n the presence of 1,25(OH)(2) vitamin D-3. In order to develop an in vitro model of osteoclast differentiation which more closely parallels the cellul ar microenvironment at the bone-implant interface in situ, we determined wh ether osteoblast-like human bone-derived cells were capable of supporting t he differentiation of osteoclasts from arthroplasty-derived cells and analy sed the humoral conditions required for this to occur. Long-term co-culture of arthroplasty-derived cells and human trabecular-bon e-derived cells (HBDCs) resulted in the formation of numerous tartrate-resi stant-acid-phosphatase (TRAP) and vitronectin-receptor (VNR)-positive multi nucleated cells capable of extensive resorption of lacunar bone. The additi on of 1,25(OH)(2) vitamin D-3 was not required for the formation of osteocl asts and bone resorption, During the formation there was release of substan tial levels of M-CSF and PGE(2), Exogenous PGE(2) (10(-8) to 10(-6)M) was f ound to stimulate strongly the resorption of osteoclastic bone. Our study h as shown that HBDCs are capable of supporting the formation of osteoclasts from mononuclear phagocyte precursors present in the periprosthetic tissues surrounding a loose implant, The release of M-CSF and PGE, by activated ce lls at the bone-implant interface may be important for the formation of ost eoclasts at sites of pathological bone resorption associated with aseptic l oosening.