Mesenchymal Tissue Response to Heterotopically Placed Demineralized Bone Power Particles in the Rat

摘要

It has been shown that demineralized bone fragments would stimulate osteogenesis even when implanted in heterotopic tissues. Demineralized bone powder (DBP) induces osteogenesis by promoting transformation of fibroblasts to chondroblasts with subsequent endochondral ossification. An important early event in heterotopic bone induction is the binding of fibronectin to DBP. Since fibronectin is chemotactic for fibroblasts and acts as a substrate for their migration it is possible that its presence at the time of DPB implantation might enhance the production of bone. To assess the effect of recipient age on the tissue response to the DBP and to determine the effect of 'wetted' versus 'dry' implantation of the DBP particles, 4 three week old Long Evans rats each had four implants of DBP placed in subcutaneous thoracic pouches. Two of the four implants consisted of DBP 'wetted' with PBS 24 hours prior to implantation and two implants were placed as dry particles. All if the implants which were implanted after incubation either in PBS alone or PBS with fibronectin, failed to induce bone formation regardless of the age of the recipient rat. In contrast, DBP that was implanted as dry particles in the 3 week old rats formed cartilage and bone. These data indicate that exogenous serum fibronectin in PBS present at the time of implantation does not promote the formation of heterotopic bone and that prewetting with PBS alters the mesenchymal response to DBP. This may be due to a change in the required spacial relationship and proximity of the DBP particles or to the extraction of one or more inductive factors. Theses