Implant wear induces inflammation, but not osteoclastic bone resorption, in RANK(-/-) mice.

Signaling of RANK (receptor activator of nuclear factor kappa B) through its ligand RANKL appears critical in osteolysis associated with aseptic loosening (AL). The purpose of this study was to investigate the role of RANK in a murine osteolysis model developed in RANK knockout (RANK(-/-)) mice. Ultra high molecular weight polyethylene (UHMWPE) debris was introduced into established air pouches on RANK(-/-) mice, followed by implantation of calvaria bone from syngeneic littermates. Wild type C57BL/6 (RANK(+/+)) mice injected with either UHMWPE or saline alone were included in this study. Pouch tissues were collected 14 days after UHMWPE inoculation for molecular and histology analysis. Results showed that UHMWPE stimulation induced strong pouch tissue inflammation in RANK(-/-) mice, as manifested by inflammatory cellular infiltration, pouch tissue proliferation, and increased gene expression of IL-1beta, TNFalpha, and RANKL. However, the UHMWPE-induced inflammation in RANK(-/-) mice was not associated with the osteoclastic bone resorption observed in RANK(+/+) mice. In RANK(+/+) mice subjected to UHMWPE stimulation, a large number of TRAP(+) cells were found on the implanted bone surface, where active osteoclastic bone resorption was observed. No TRAP(+) cells were found in UHMWPE-containing pouch tissues of RANK(-/-) mice. Consistent with the lack of osteoclastic activity shown by TRAP staining, no significant UHMWPE particle-induced bone resorption was found in RANK(-/-) mice. A well preserved bone collagen content (Van Gieson staining) and normal plateau surface contour [microcomputed tomography (microCT)] of implanted bone was observed in RANK(-/-) mice subjected to UHMWPE stimulation. In conclusion, this study provides the evidence that UHMWPE particles induce strong inflammatory responses, but not associated with osteoclastic bone resorption in RANK(-/-) mice. This indicates that RANK signaling is essential for UHMWPE particle-induced osteoclastic bone resorption, but does not participate in UHMWPE particle-induced inflammatory response.     

rhIGF-1对成骨细胞增殖、分化及骨保护素、骨保护素配体基因mRNA表达的影响

目的 观察不同剂量rhIGF-1对成骨细胞增殖，分化及骨保护素，骨保护素配体mRNA基因表达的影响，为明确骨保护素，骨保护素配体在骨质疏松症发病的作用机理及rhIGF-1在临床中应用提供实验依据。方法 取2代培养的大鼠成骨细胞，在rhIGF-1为0ng/ml,10ng/ml,20ng/ml,50ng/ml的浓度中培养。观察细胞的生长及钙结节的形成，MTT法，碱性磷酸酶（ALP），骨钙素（OCN）测定细胞增殖和分化，RT－PCR测定rhIGF-1对成骨细胞骨保护素，骨保护素配体基因mRNA表达的影响。结果 成骨细胞在7d可铺满瓶壁，30d可形成钙结节，rhIGF-1可促进成骨细胞的增殖，ALP和OGN的分泌，促进骨保护素，骨保护素配体基因的表达，以促进骨保护素表达明显，在rhIGF-1为10ng/ml时作用明显。结论 rhIGF-1可促进大鼠成骨细胞的增殖，分化，及骨保护素，骨保护素配体基因mRNA的表达，骨保护素mRNA表达显。rhIGF-1可能通过影响骨保护素，骨保护素配体而调节成骨细胞破骨细胞的平衡，使骨重建，从而防治骨质疏松症。     

Substance P stimulates release of RANKL via COX-2 expression in human dental pulp cells

Objective: Our previous study found that substance P (SP), a sensory neuropeptide, was expressed in the dental pulp of rats during experimental tooth movement. We examined the effects of SP on the production of prostaglandin (PG) E₂ and the receptor activator of nuclear factor- B ligand (RANKL) by human dental pulp fi broblast-like (HDPF) cells. Materials and methods: SP was added to cultured HDPF cells at concentrations ranging from of 10⁻⁴ to 10⁻¹² mol/L. PGE₂ and soluble RANKL (sRANKL) levels were determined using enzyme-linked immunosorbent assay kits. Gene expression was confi rmed by RT-PCR analysis. Pit formation assays using dentin slices were carried out to examine the effect of SP on osteoclastogenesis. Results: The levels of PGE₂ and sRANKL increased in the presence of SP, though the increases were greater in the experimental groups in both a time- and concentration-dependent manner, and the increase of RANKL was partially mediated by PGE₂ . The gene expression of cyclooxygenase (COX)-2 and RANKL was up-regulated, and conditioned medium samples obtained from HDPF cells treated with SP induced bone resorption. Conclusions: SP stimulated the production of PGE₂ and RANKL, and promoted bone resorption. Therefore, SP may be involved in pulpal inflammation and root resorption during orthodontic tooth movement. Received 11 April 2005; returned for revision 27 July 2005; returned for final revision 20 September 2005; accepted by M. Katori 2 November 2005     

虾青素对去卵巢糖尿病大鼠骨质流失的防治作用

目的探讨虾青素能否防治去卵巢糖尿病大鼠的骨质流失以及可能的机制。方法 3月龄雌性SD大鼠分为3组(每组6只):对照组CON(假手术),模型组OVX/T1DM(去卵巢糖尿病大鼠),药物组OVX/T1DM-ASX(去卵巢糖尿病大鼠,给予虾青素100 mg/(kg·d)。结果连续治疗60 d后,与OVX/T1DM组相比,OVX/T1DM-ASX组骨密度(BMD)明显升高(P0.01),血清I型胶原蛋白(CTX-1)、骨钙素、I型前胶原蛋白n端前肽(PINP)、抗酒石酸磷酸酶5b(TRACP 5b)水平均显著升高(P0.01)。虾青素治疗能抑制去卵巢糖尿病大鼠骨组织形态学的改变,减少骨髓脂肪细胞增加,提高OPG/RANKL的比值。结论虾青素对绝经后糖尿病骨质流失有保护作用,这种作用与调控OPG/RANKL轴有关。     

RANKL inhibition for the management of patients with benign metabolic bone disorders

The receptor activator of NF-κB ligand (RANKL) is a member of the TNF receptor superfamily, essential for osteoclastogenesis. It binds to its receptor activator of NF-κB on the surface of osteoclast precursors and enhances their differentiation, survival and fusion, while it activates mature osteoclasts and inhibits their apoptosis. The effects of RANKL are counteracted by osteoprotegerin (OPG), a neutralizing decoy receptor. Derangement of the balance in RANKL/OPG action is implicated in the pathophysiology of metabolic bone diseases, including osteoporosis. Current therapies used to prevent or treat metabolic bone diseases are thought to act, at least in part, through modification of the RANKL/OPG dipole. The idea of using a molecule that could specifically bind and neutralize RANKL to decrease bone resorption and subsequent bone loss is appealing. Recombinant OPG was initially tested. Denosumab, a fully human monoclonal antibody against RANKL, is a promising antiresorptive agent under investigation. It rapidly decreases bone turnover markers resulting in a significant increase in bone mineral density and reduction in fracture risk. However, because receptor activator of NF-κB activation by RANKL is also essential for T-cell growth and dendritic-cell function, inhibition of its action could simultaneously affect the immune system, leading to susceptibility in infections or malignancies.     

Th1/Th17/Th22 immune response and their association with joint pain,imagenological bone loss,RANKL expression and osteoclast activity in temporomandibular joint osteoarthritis: A preliminary report

It is well accepted that the presence of cytokines belonging to the Th1/Th17/Th22 axis of immuno‐inflammatory response in the joint environment, such as IL‐1β, IL‐17 and IL‐22, respectively, are associated with pathogenesis of several synovial joint degenerative disorders. During temporomandibular joint osteoarthritis (TMJ‐OA), IL‐1β and IL‐17 have been implicated in the inflammation and resorption of sub‐chondral bone; however, the role of Th22 response in the TMJ‐OA pathophysiology has not been established. This study aimed to compare the expression of Th1/Th17/Th22‐type cytokines, chemokines and chemokine receptors in synovial fluid samples obtained from TMJ‐OA or disk displacement with reduction (DDWR) patients. In addition, it aimed to associate these levels with joint pain, imagenological signs of bone degeneration, RANKL production, osteoclastogenesis and osteoclast‐induced bone resorption. Higher levels of IL‐1β, IL‐17 and IL‐22 were expressed in TMJ‐OA compared with DDWR subjects, and these increased levels significantly correlated with RANKL expression, joint pain and articular bone degeneration. Higher levels of CCR5, CCR6 and CCR7, as well as their respective ligands CCL5 and CCL20, responsible for recruitment of IL‐1β, IL‐17 and IL‐22‐producing cells, were over‐expressed in TMJ‐OA compared with DDWR subjects. Osteoclastogenesis and osteoclast‐induced bone resorption were significantly greater in presence of synovial fluid from TMJ‐OA compared with DDWR subjects. These data demonstrate that cytokines, CCLs and CCRs associated with the Th1/Th17/Th22 axis of immuno‐inflammatory response are involved in TMJ‐OA pathogenesis. These findings suggest that IL‐22 is involved in the RANKL expression in TMJ‐OA, which in turn induces differentiation of osteoclasts and subsequent resorption of sub‐chondral bone.