The Efects Of Recombinant Human Osteoprotegerin On The Osteoclasts Indueced By The Polyethylene Particles

With the prosthetic replacement of joint generally becoming an important treatment for many kinds of orthopaedic diseases, some long-term harmful effects of it have been increasingly noticed. Sterility cinch is one of it complications. The mechanic and biology factors are considered to be the two formation mechanism of sterility cinch. Polythene particles caused by abrasion of the arthrosis prothesis enhance the resorption ability of osteoclast, which is a important reason to cause serility cinch in biology factor. The artificial joint materials could produce many finely particles after long time friction and relative activity. These particles can activate inflammatory cells, precipitate the cells to release many cytokine related to bone resorption and make the properly fixed prothesis loose.RANKL/RANK/OPG system is very important for osteoclast differention. RANKL is belong to the necrosin family which is a essential agent for the mature of precursor osteoclast. Because RANKL can not enter into internal of the cell, it has to regulate osteoclast differention through RANK. RANK is type I transmembrane receptor protein which is situated at surface of osteoclast and its precursor cell. In the mature process of osteoclast, marrow strome cell and osteoblast firstly excrete macrophage colony-stimulating factor which can combine with the receptor in the surface of osteoclast precursor. Then, RANKL bind with RANKL in the surface of osteoclast precursor and mediate the mature of osteoclast through JNK, NF-κB, Akt routes. Osteoprotegerin which was discovered by Simonet in 1997 is a decoy receptor of RANKL regulating bone metabolism. Osteoprotegerin can bind to RANKL competing with RANK and block the binding of RANK and RANKL, which result in dysmaturity of osteoclast.It is investigated that co-contact between Polythene particles and macrophage may cause macrophage to excrete phlogistic cytokines such as TNF-α, IL-6, which can activate transcription factor NF-κB in and its precursor cell and lead to osteoclast mature. This demonstrates that the particle itself is a signal which can initiate signal transduction and cause biology effect. Co-cultured with titanium, cobalt-chromium alloy or stainless steel particles and peripheral blood monouclear cells can stimulate cells to highly express RANKL/RANK, which further conformst that the increase of RANKL/RANK is induced by the particles. It is discovered that the proportion of RANKL/OPG is serious imbalance after detecting the coax synovial fluid of patients who failed in the hip replacement because of cinch. This imbalance is bound to result in imbanlance of bone metabolism and osteolysis. Therefore, particles stimulate cells through RANKL/RANK/OPG.Now that the stimulation effect to osteoclast differentiation and bone resorption by particles must depend on RANKL, we assume that OPG is used to block the combination between RANKL and RANK to see whether it can block the particles stimulation to OC differentiation. In our experiment, osteoclast cells in vitro culture were interfered by polyethylene particles to cause osteoclast differention. We add rhOPG in culture fluidin under the same conditions to oberserve the influence on osteoclast differention and investigate the possibility of rhOPG inhibiting rhOPG on the aseptic loosening of prosthesis. The osteoclasts were isolated from the long bones of neonatal New Zealand S rabbits, and cocultured in the glass cover slips(10 mm x 10 mm) and bone slices (10 mm x 10 mm). Osteoclasts were identified as multi-nucleated TRAP-positive cells. Osteoclast function was quantified with the number of bone resorption tips and TRAP activity in culture supernatants.The plates of cocultres were divided into three groups: control group (CG), the group cultured with polyethylene particles of 109/ml (PG),and the group with both polyethylene particles of 109/ml and rhOPG of 100ng/ml (PO). The glass cover slips and bone slices were obtained for HE, toluidine blue and tartrate-resistant acid phosphatase (TRAP) staining at 1, 3, 5 and 7 days, and TRAP positive multinucleated cells and bone resorption tips were counted, scanning electron microscopy was used to observe the pits of bone resorption. The appearance of isolated rabbit osteoclast were typical. The number of the TRAP-positive multinucleated cells of the three groups was not different at day 1 and day 3, but the number of the TRAP-positive multinucleated cells was significantly increased at day 5 in the group PG (p < 0.05), the osteoclast differentiation was inhibit buy rhOPG in the PO group (p < 0.05), the number of the TRAP-positive multinucleated cells in the group OC and group PO has no significantly different. The number of bone resorption pits on bone slices was significantly increased in PG group, this increation can be inhibited by rhOPG. Furthurmore, The number of bone resorption pits on bone slices in PO group was significantly decreased from the first to the seventh day.Our findings suggest that: (1) Cocultured with polyethylene particles, the bone resorption activity of OC was enhanced; (2) The number of OC were significantly decreased in the PO group than those in the PG group. rhOPG could inhibit the bone resorption of OC which stimulated by polyethylene particles, and might be used to prevent the aseptic loosening of prosthesis.