Increased UHMWPE Particle-Induced Osteolysis in Fetuin-A-Deficient Mice.

Particle-induced osteolysis is a major cause of aseptic prosthetic loosening. Implant wear particles stimulate tissue macrophages inducing an aseptic inflammatory reaction, which ultimately results in bone loss. Fetuin-A is a key regulator of calcified matrix metabolism and an acute phase protein. We studied the influence of fetuin-A on particle-induced osteolysis in an established mouse model using fetuin-A-deficient mice. Ten fetuin-A-deficient (Ahsg−/−) mice and ten wild-type animals (Ahsg+/+) were assigned to test group receiving ultra-high molecular weight polyethylene (UHMWPE) particle implantation or to control group (sham surgery). After 14 days, bone metabolism parameters RANKL, osteoprotegerin (OPG), osteocalcin (OC), alkaline phosphatase (ALP), calcium, phosphate, and desoxypyridinoline (DPD) were examined. Bone volume was determined by microcomputed tomography (µCT); osteolytic regions and osteoclasts were histomorphometrically analyzed. After particle treatment, bone resorption was significantly increased in Ahsg−/− mice compared with corresponding Ahsg+/+ wild-type mice (p = 0.007). Eroded surface areas in Ahsg−/− mice were significantly increased (p = 0.002) compared with Ahsg+/+ mice, as well as the number of osteoclasts compared with control (p = 0.039). Fetuin-A deficiency revealed increased OPG (p = 0.002), and decreased levels of DPD (p = 0.038), OC (p = 0.036), ALP (p < 0.001), and Ca (p = 0.001) compared with wild-type animals. Under osteolytic conditions in Ahsg−/− mice, OPG was increased (p = 0.013), ALP (p = 0.015) and DPD (p = 0.012) were decreased compared with the Ahsg+/+ group. Osteolytic conditions lead to greater bone loss in fetuin-A-deficient mice compared with wild-type mice. Reduced fetuin-A serum levels may be a risk factor for particle-induced osteolysis while the protective effect of fetuin-A might be a future pathway for prophylaxis and treatment.

No Association of CALCA Polymorphisms and Aseptic Loosening after Primary Total Hip Arthroplasty.

Studies of aseptic loosening showed an influence of calcitonin and α-CGRP, both encoded from the calcitonin/α-CGRP (CALCA) gene by alternative splicing. The aim of this study was to detect a possible association of the CALCA polymorphisms P1(rs1553005), P2(rs35815751), P3(rs5240), and P4(rs2956) with the time to aseptic loosening after THA. 320 patients suffering from aseptic loosening after primary total hip arthroplasty were genotyped for CALCA-P1 polymorphism and 161 patients for CALCA-P2 and CALCA-P3 polymorphisms and 160 patients for CALCA-P4 polymorphism. CALCA genotypes were determined by polymerase chain reaction and restriction-fragment length polymorphism. The genotype distribution of CALCA-P1 was CC 10%, CT 43%, and 46% TT. CALCA-P2 showed a distribution of 90.7%II, 8.7% ID, and 0.6% DD. The CALCA-P3 genotype distribution was 97.5% TT and 2.5% TC. The CALCA-P4 genotype distribution was 48.1% AA, 40% AT, and 11.9% TT. Significant differences between the CALCA genotypes were not found concerning age at implantation and replantation, BMI, gender, and cementation technique. No associations of the time for aseptic loosening were found. In conclusion, we did not find a significant association of CALCA polymorphisms and the time to aseptic loosening after primary THA in a Western European group.

Influence of kitesurf equipment on injury rates.

BACKGROUND: Various injuries in kitesurfing (KS) have been reported so far. The aim of this study was to validate the effect of different kite designs and safety equipment on the injury rate compared to older studies. METHODS: A retrospective epidemiological study based on an anonymous face-to-face survey was conducted amongst active kitesurfers. The questionnaire consisted of 66 questions focusing on the equipment used, injury rates, overuse injuries and gender differences. A stepwise Poisson-Model was used to identify injury-associated factors. RESULTS: A total of 202 kitesurfers with a mean age of 31.8±9.1 years and 698.2±931.5 hours of KS experience were included. 2613 injuries were recorded (18.5/1000 hours KS). Almost 50% were hematomas, bruises or cuts. 3.9% of all injuries (0.71/1000 hours KS) were time-loss injuries of more than one week. Female kitesurfers had a significantly greater injury rate, were less experienced and fewer of them used C-kites. Height, weight, primary kite spot, experience, physical activity, warm-up/stretching, the type of kite and control bar used, and the use of a board leash were independent factors associated to injury rate. The lower extremity, the elbow, thorax and abdomen were at risk for overuse injuries. CONCLUSIONS: An influence of equipment on injuries could be statistically shown. The overall injury rate in KS did not decline in the last decades, but time-loss injuries did.

A single intraperitoneal injection of bovine fetuin-A attenuates bone resorption in a murine calvarial model of particle-induced osteolysis.

Particle-induced osteolysis, which by definition is an aseptic inflammatory reaction to implant-derived wear debris eventually leading to local bone destruction, remains the major reason for long-term failure of orthopedic endoprostheses. Fetuin-A, a 66kDa glycoprotein with diverse functions, is found to be enriched in bone. Besides being an important inhibitor of ectopic calcification, it has been described to influence the production of mediators of inflammation. Furthermore, a regulatory role in bone metabolism has been assigned. In the present study, the influence of a single dose of bovine fetuin-A, intraperitoneally injected in mice subjected to particle-induced osteolysis of the calvaria, was analyzed. Twenty-eight male C57BL/6 mice, twelve weeks of age, were randomly divided into four groups. Groups 2 and 4 were subjected to ultra-high molecular weight polyethylene (UHMWPE) particles placed on their calvariae while groups 1 and 3 were sham-operated. Furthermore, groups 3 and 4 received a single intraperitoneal injection of 20mg bovine fetuin-A while groups 1 and 2 were treated with physiologic saline. After 14days calvarial bone was qualitatively and quantitatively assessed using microcomputed tomography (µCT) and histomorphometrical approaches. Application of fetuin-A led to a reduction of particle-induced osteolysis in terms of visible osteolytic lesions and eroded bone surface. The reduction of bone thickness and bone volume, as elicited by UHMWPE, was alleviated by fetuin-A. In conclusion, fetuin-A was found to exert an anti-resorptive effect on particle-induced osteolysis in-vivo. Thus, fetuin-A could play a potentially osteoprotective role in the treatment of bone metabolic disorders.

Relationship between GNAS1 T393C polymorphism and aseptic loosening after total hip arthroplasty.

BACKGROUND: Aseptic loosening is a main cause for revision surgery after total hip arthroplasty (THA) and there is no reliable marker for the early detection of patients at high risk. This study has been performed to validate association of the T393C polymorphism (rs7121) in the GNAS1 gene, encoding for the alpha-subunit of heterotrimeric G-protein Gs, with risk for and time to aseptic loosening after THA, which has been demonstrated in our previous study. METHODS: 231 patients with primary THA and 234 patients suffering from aseptic loosening were genotyped for dependency on GNAS1 genotypes and analyzed. RESULTS: Genotyping revealed almost similar minor allele frequencies of 0.49 and 0.46, respectively. Consistently, genotype distributions of both groups were not significantly different (p = 0.572). Neither gender nor GNAS1 genotype showed a statistically significant association with time to loosening (p = 0.501 and p = 0.840). Stratification by gender, as performed in our previous study, was not able to show a significant genotype-dependent difference in time (female p = 0.313; male p = 0.584) as well as median time to aseptic loosening (female p = 0.353; male p = 0.868). CONCLUSION: This study was not able to confirm the results of our preliminary study. An association of the GNAS1 T393C polymorphisms with risk for and time to aseptic loosening after THA is unlikely.

Impact of vitamin E-blended UHMWPE wear particles on the osseous microenvironment in polyethylene particle-induced osteolysis.

Aseptic loosening mediated by wear particle-induced osteolysis (PIO) remains the major cause of implant loosening in endoprosthetic surgery. The development of new vitamin E (α-tocopherol)-blended ultra-high molecular weight polyethylene (VE-UHMWPE) with increased oxidation resistance and improved mechanical properties has raised hopes. Furthermore, regenerative approaches may be opened, as vitamin E supplementation has shown neuroprotective characteristics mediated via calcitonin gene-related peptide (CGRP), which is known to affect bone remodeling in PIO. Therefore, the present study aimed to further clarify the impact of VE-UHMWPE wear particles on the osseous microenvironment and to identify the potential modulatory pathways involved. Using an established murine calvaria model, mice were subjected to sham operation (SHAM group), or treated with UHMWPE or VE-UHMWPE particles for different experimental durations (7, 14 and 28 days; n=6/group). Morphometric analysis by micro-computed tomography detected significant (p<0.01) and comparable signs of PIO in all particle-treated groups, whereas markers of inflammation [tumor necrosis factor (TNF)-α/tartrate resistant acid phosphatase (TRAP) staining] and bone remodeling [Dickkopf-related protein 1 (DKK-1)/osteoprotegerin (OPG)] were most affected in the early stages following surgery. Taking the present data into account, VE-UHMWPE appears to have a promising biocompatibility and increased ageing resistance. According to the α-CGRP serum levels and immunohistochemistry, the impact of vitamin E on neuropeptidergic signaling and its chance for regenerative approaches requires further investigation.

The BCL2 -938C>A Promoter Polymorphism Is Associated with Risk for and Time to Aseptic Loosening of Total Hip Arthroplasty.

Aseptic loosening is a major cause of revision surgery of total hip arthroplasty (THA). Only few host factors affecting aseptic loosening have been identified until now, although they are urgently needed to identify and possibly treat those patients at higher risk for aseptic loosening. To determine whether the functional single nucleotide polymorphism (SNP) c.-938C>A (rs2279115), located in the promoter region of the BCL2 gene has an impact on aseptic loosening of THA we genotyped and analyzed 234 patients suffering from aseptic loosening and 231 patients after primary THA. The polymorphism is associated with risk for aseptic loosening with the CC genotype at highest risk for aseptic loosening, Odds Ratio CC vs. AA 1.93, 95%CI 1.15-3.25, p = 0.013. In contrast, low risk AA genotype carriers that still developed aseptic loosening showed a significantly shorter time to aseptic loosening than patients carrying the C allele (p = 0.004). These results indicate that the BCL2 -938C>A polymorphism influences the occurrence and course of aseptic loosening and suggests this polymorphism as an interesting candidate for prospective studies and analyses in THA registers.

Wheel-gymnastic-related injuries and overuse syndromes of amateurs and professionals.

PURPOSE: Wheel gymnastics is a gymnastic discipline with a history of nearly 100 years. So far, there have been no epidemiological studies on injuries in wheel gymnastics. METHODS: The retrospective study of wheel gymnasts surveyed 151 "professionals" competing in the first national league and 352 "amateurs" by questionnaire. RESULTS: 4,898 injuries and 714 overuse syndromes were found in 988,718.9 h of training, leading to a time loss of 16,302 days. An incidence of 9.44 injuries per 1,000 h was found in wheel gymnastics. "Professionals" had a highly significant lower incidence than "amateurs" (5.23 vs. 11.24 injuries per 1,000 h; p < 0.001). The most common injuries in wheel gymnastics were found at the head (28.1 %), spine (13.75 %), ankle/foot (11.88 %), hip/thigh (11.87 %) and knee (11.61 %). 4,502 (91.9 %) injuries were classified as minor. 221 (4.5 %) injuries caused a time loss of between 1 week and 1 month. 175 (3.6 %) major injuries caused a time loss of longer than 1 month. 1.68 overuse syndromes per 1,000 h were described. CONCLUSION: Wheel gymnastics has a high incidence but low severity of injuries compared with other gymnastic sports. Physicians should be aware of the common dangers and overuse syndromes in this highly acrobatic gymnastic discipline. LEVEL OF EVIDENCE: III.

Calcitonin gene-related peptide modulates the production of pro-inflammatory cytokines associated with periprosthetic osteolysis by THP-1 macrophage-like cells.

OBJECTIVE: An anti-resorptive impact of the neuropeptide calcitonin gene-related peptide (CGRP) on periprosthetic osteolysis, the leading cause of early prosthesis loosening, has been shown previously. In this study, the impact of CGRP on pro-inflammatory cytokine production associated with periprosthetic osteolysis was analysed using THP-1 macrophage-like cells. METHODS: Cells were stimulated with ultra-high-molecular-weight polyethylene (UHMWPE) particles (cell-to-particle ratios of 1:100 and 1:500) and lipopolysaccharides (LPS; 1 µg/ml) to establish osteolytic conditions, and simultaneously treated with CGRP (10(-8)M). Receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) and tumour necrosis factor (TNF)-α mRNA expression were measured by quantitative RT-PCR. RANK protein was detected by Western blot. Secreted protein levels of TNF-α as well as interleukin (IL)-1ß and IL-6 were quantified in cell culture supernatants by ELISA and Bio-Plex cytokine assay, respectively. RESULTS: Activation of macrophage-like cells failed to enhance the production of RANK but led to a dose- and time-dependent increase of TNF-α mRNA and secreted protein levels of TNF-α, IL-1ß and IL-6. Application of CGRP time-dependently suppressed TNF-α mRNA expression induced by low-particle concentrations and LPS, while both particle- and LPS-induced secretion of TNF-α was inhibited. A pronounced inhibitory effect of CGRP on LPS-induced cytokine production at 24 h of incubation was also observed with IL-1ß and IL-6. CONCLUSIONS: CGRP shows a time-dependent inhibitory effect on the secretion of osteolysis-associated pro-inflammatory cytokines, indicating an indirect anti-resorptive influence of the neuropeptide on both aseptic prosthesis loosening and bacterially induced bone resorption which might enhance the life time of total joint replacements.

The role of calcitonin receptor signalling in polyethylene particle-induced osteolysis.

The detection of peptides from the calcitonin (CT) family in the periarticular tissue of loosened implants has raised hopes of opening new regenerative therapies in the process of aseptic loosening, which remains the major cause of early implant failure in endoprosthetic surgery. We have previously shown the roles of α-calcitonin gene-related peptide (α-CGRP) and the CALCA gene which encodes α-CGRP/CT in this process. To uncover the role of direct calcitonin receptor (CTR) mediated signalling, we studied particle-induced osteolysis (PIO) in a murine calvaria model with a global deletion of the CTR (CTR-KO) using µCT analysis and histomorphometry. As expected, CTR-KO mice revealed reduced bone volume compared to wild-type (WT) controls (p<0.05). In CTR-KO mice we found significantly higher RANKL (receptor activator of NF-κB ligand) expression in the particle group than in the control group. The increase in osteoclast numbers by the particles was twice as high as the increase of osteoclasts in the WT mice (400 vs. 200%). Changes in the eroded surface and actual osteolysis due to ultrahigh-molecular-weight polyethylene particles were similar in WTs and CTR-KOs. Taken together, our findings strengthen the relevance of the OPG/RANK/RANKL system in the PIO process. CTR seems to have an effect on osteoclast differentiation in this context. As there were no obvious changes of the amount of PIO in CTR deficiency, regenerative strategies in aseptic loosening of endoprosthetic implants based on peptides arising from the CT family should rather focus on the impact of α-CGRP.

RANKL-associated suppression of particle-induced osteolysis in an aged model of Calcitonin and α-CGRP deficiency.

An aging population with higher bone turnover intensifies the need for joint replacement surgery. However, particle-induced osteolysis (PIO) remains a major cause of early implant loosening. Differences in bone remodeling between young and aged Calcitonin (CT)- and α-CGRP (Calcitonin gene-related peptide)-deficient mice (Calca(-/-)) might modify our previous findings regarding CT/α-CGRP in PIO. This may have important implications for PIO in an aging population. Four groups of twelve-month-old wild-type and Calca(-/-) mice underwent either SHAM surgery with and without CT, or polyethylene-particle implantation with related treatment. Morphometric changes were detected using µ-CT, histomorphometric analysis and by counting TRAP(+) cells (osteoclast-staining). Bone remodeling was assessed using serum and urinary markers. There was no osteolysis in aged particle-treated Calca(-/-) animals and the effect of CT on PIO was reduced compared to wild-type mice. However, there were significantly higher numbers of TRAP(+) cells in Calca(-/-) animals, and bone remodeling markers revealed a significant increase in OPG/OCN and a significant reduction in RANKL compared to aged wild-type mice. CT/α-CGRP modulates bone cell activity in PIO in aged mice in a way that is distinct from young animals. This may have implications for the treatment of PIO in the periprosthetic surface of joint replacements in an aging population.

Cementless second-generation hydroxyapatite CaP-coated tibial component: an 8.7-year follow-up.

BACKGROUND: This is the first study that reports on the mid-term results of 81 patients suffering from arthritis of the knee, treated with a cementless second-generation hydroxyapatite calcium phosphate (CaP)-coated tibial component. MATERIALS AND METHODS: Seventy-six knees with osteoarthritis were evaluated according to the Knee Society clinical, functional and radiological score, the Hospital for Special Surgery Rating System and the Patella Score. The clinical and radiological parameters were assessed preoperatively and after a mean follow-up of 8.7 years. RESULTS: All the three score systems revealed excellent clinical outcomes after the follow-up period. The mean preoperative Knee Society clinical Score was 124.41 ± 12.99 and the mean postoperative score was 187.07 ± 14.59 at the time of the final consultation (p = 0.0008). The survival rate was 97.5 %. Radiolucency of <1 mm around the uncemented hydroxyapatite CaP-coated tibial component without accompanying pain symptoms was seen in fewer than 6 % of cases. In two cases, a medial cyst, also without other clinical symptoms, was observed beside the tip of the tibial fixation screw. CONCLUSION: These findings indicate that the uncemented second-generation hydroxyapatite CaP-coated tibial component performed well at mid-term follow-up, and provides sufficiently stable bone ingrowth fixation.

Inhibition of osteoclastogenesis by RNA interference targeting RANK.

BACKGROUND: Osteoclasts and osteoblasts regulate bone resorption and formation to allow bone remodeling and homeostasis. The balance between bone resorption and formation is disturbed by abnormal recruitment of osteoclasts. Osteoclast differentiation is dependent on the receptor activator of nuclear factor NF-kappa B (RANK) ligand (RANKL) as well as the macrophage colony-stimulating factor (M-CSF). The RANKL/RANK system and RANK signaling induce osteoclast formation mediated by various cytokines. The RANK/RANKL pathway has been primarily implicated in metabolic, degenerative and neoplastic bone disorders or osteolysis. The central role of RANK/RANKL interaction in osteoclastogenesis makes RANK an attractive target for potential therapies in treatment of osteolysis. The purpose of this study was to assess the effect of inhibition of RANK expression in mouse bone marrow macrophages on osteoclast differentiation and bone resorption. METHODS: Three pairs of short hairpin RNAs (shRNA) targeting RANK were designed and synthesized. The optimal shRNA was selected among three pairs of shRNAs by RANK expression analyzed by Western blot and Real-time PCR. We investigated suppression of osteoclastogenesis of mouse bone marrow macrophages (BMMs) using the optimal shRNA by targeting RANK. RESULTS: Among the three shRANKs examined, shRANK-3 significantly suppressed [88.3%] the RANK expression (p < 0.01). shRANK-3 also brought about a marked inhibition of osteoclast formation and bone resorption as demonstrated by tartrate-resistant acid phosphatase (TRAP) staining and osteoclast resorption assay. The results of our study show that retrovirus-mediated shRANK-3 suppresses osteoclast differentiation and osteolysis of BMMs. CONCLUSIONS: These findings suggest that retrovirus-mediated shRNA targeting RANK inhibits osteoclast differentiation and osteolysis. It may appear an attractive target for preventing osteolysis in humans with a potential clinical application.

A simple and convenient method guide to determine the magnification of digital X-rays for preoperative planning in total hip arthroplasty.

Scaling of anteroposterior digital pelvic X-rays with variable magnification is the premise for accurate preoperative planning of total hip replacement with digital templating. Conn's method of placing a marker of known diameter beside the thigh at the level of the femur has been reproduced in many studies and confirmed as one of the most accurate methods. But in our experience, it is inconvenient for radiographers and is not well tolerated by some patients. We modified this method by placing a coin on the radiograph plate. One hundred patients who had undergone hip replacement were enrolled in the study and randomly divided into two groups. The actual diameter of the prosthesis head was taken as the gold standard for assessment of the magnification of the coin in Group A. The coin was within a mean of 117.95% (range 114.37-122.02%) of magnification for male, and 111.71% (range 114.37-120.93%) for female patients. The variation was small and limited, and had no correlation with body shape parameters (i.e. height, weight, BMI). Subsequently, the magnification of the coin was used to correct the measuring scale of the X-rays of the other 50 patients (Group B). Bias did not exceed 1.96 mm during measurement of the prosthesis with a diameter of less than 56 mm, and a range of absolute error of measurements of 56-66 mm (standard deviation, SD, 0.04-3.95 mm). Furthermore, in order to confirm the expressiveness of the modified method, CT scans of another 50 patients were randomly selected. The distance between the rotation center of the hip and the table, which is acknowledged to be a factor which influences magnification of the coin, changed little in response to body shape. Variation in magnification was caused by variation in distance between the rotation center of the hip and the table. The minimal change in distance for patients with different body shape led to easier and more convenient examination, and increased the feasibility of our modified coin method, except in cases where implantation of a very large-sized prosthesis is necessary.

Cervical range of motion and strength in 4,293 young male adults with chronic neck pain.

PURPOSE: The correlation of cervical biomechanics and neck pain in young patients has, to date, only been described in terms of small cohorts. This study focuses on the correlation of chronic neck pain and cervical biomechanics. METHODS: Neck pain, cervical range of motion (CROM) and maximal cervical torque were recorded in 746 patients with conservatively treated chronic neck pain and 3,547 participants of physiotherapy training without chronic neck pain aged 16-32 years. RESULTS: The "neck pain" group had a highly significant (s < 0.001) higher neck disability index (44.7 vs. 10.4%), longer history of neck pain (3.47 vs. 0.59 years), higher pain intensity (VAS 5.93 vs. 0.93), higher pain frequency (VAS 6.98 vs. 1.09). No differences of CROM and maximal torque in the sagittal, frontal and transverse plane were found. CONCLUSION: This study describes the largest cohort of biomechanical data of the cervical spine in young adult recorded to date. The findings demonstrate that no correlation was found between neck pain, CROM and maximal torque in the study cohort. On this basis, we conclude that the CROM and maximal cervical torque should not be used as indicators to measure the progress of chronic neck pain in physiotherapy training and sports medicine for the young adult.

Hemipelvectomy- only a salvage therapy?

After the first hemipelvectomy in 1891 significant advances have been made in the fields of preoperative diagnosis, surgical technique and adjuvant treatment in patients with pelvic tumors. The challenging surgical removal of these rare malignant bone or soft tissue tumors accompanied by interdisciplinary therapy is mostly the only chance of cure, but bares the risk of intensive bleeding and infection. The reconstruction after hemipelvectomy is of importance for the later outcome and quality of life for the patient. Here, plastic surgery with microvascular free flaps or local rotational flaps improved the reconstruction and reduced infection rates. Average local recurrence rates of 14% demonstrate good surgical results, but 5 year survival rates of only 50% are described for some tumor entities, showing the importance of a multimodal collaboration. On a basis of a selective literature review the history, indications, treatment options and outcome of hemipelvectomies are presented.

Calcitonin substitution in calcitonin deficiency reduces particle-induced osteolysis.

BACKGROUND: Periprosthetic osteolysis is a major cause of aseptic loosening in joint arthroplasty. This study investigates the impact of CT (calcitonin) deficiency and CT substitution under in-vivo circumstances on particle-induced osteolysis in Calca -/- mice. METHODS: We used the murine calvarial osteolysis model based on ultra-high molecular weight polyethylene (UHMWPE) particles in 10 C57BL/6J wild-type (WT) mice and twenty Calca -/- mice. The mice were divided into six groups: WT without UHMWPE particles (Group 1), WT with UHMWPE particles (Group 2), Calca -/- mice without UHMWPE particles (Group 3), Calca -/- mice with UHMWPE particles (Group 4), Calca -/- mice without UHMWPE particles and calcitonin substitution (Group 5), and Calca -/- mice with UHMWPE particle implantation and calcitonin substitution (Group 6). Analytes were extracted from serum and urine. Bone resorption was measured by bone histomorphometry. The number of osteoclasts was determined by counting the tartrate-resistant acid phosphatase (TRACP) + cells. RESULTS: Bone resorption was significantly increased in Calca -/- mice compared with their corresponding WT. The eroded surface in Calca -/- mice with particle implantation was reduced by 20.6% after CT substitution. Osteoclast numbers were significantly increased in Calca -/- mice after particle implantation. Serum OPG (osteoprotegerin) increased significantly after CT substitution. CONCLUSIONS: As anticipated, Calca -/- mice show extensive osteolysis compared with wild-type mice, and CT substitution reduces particle-induced osteolysis.

Effects of alpha-calcitonin gene-related peptide on osteoprotegerin and receptor activator of nuclear factor-κB ligand expression in MG-63 osteoblast-like cells exposed to polyethylene particles.

BACKGROUND: Recent studies demonstrated an impact of the nervous system on particle-induced osteolysis, the major cause of aseptic loosening of joint replacements. METHODS: In this study of MG-63 osteoblast-like cells we analyzed the influence of ultra-high molecular weight polyethylene (UHMWPE) particles and the neurotransmitter alpha-calcitonin gene-related peptide (CGRP) on the osteoprotegerin/receptor activator of nuclear factor-κB ligand/receptor activator of nuclear factorκB (OPG/RANKL/RANK) system. MG-63 cells were stimulated by different UHMWPE particle concentrations (1:100, 1:500) and different doses of alpha-CGRP (10-7 M, 10-9 M, 10-11 M). RANKL and OPG mRNA expression and protein levels were measured by RT-PCR and Western blot. RESULTS: Increasing particle concentrations caused an up-regulation of RANKL after 72 hours. Alpha-CGRP showed a dose-independent depressive effect on particle-induced expression of RANKL mRNA in both cell-particle ratios. RANKL gene transcripts were significantly (P < 0.05) decreased by alpha-CGRP treatment after 48 and 72 hours. OPG mRNA was significantly down-regulated in a cell-particle ratio of 1:500 after 72 hours. Alpha-CGRP concentrations of 10-7 M lead to an up-regulation of OPG protein. CONCLUSION: In conclusion, a possible osteoprotective influence of the neurotransmitter alpha-CGRP on particle stimulated osteoblast-like cells could be shown. Alpha-CGRP might be important for bone metabolism under conditions of particle-induced osteolysis.

Alpha-calcitonin gene-related peptide can reverse the catabolic influence of UHMWPE particles on RANKL expression in primary human osteoblasts.

BACKGROUND AND PURPOSE: A linkage between the neurotransmitter alpha-calcitonin gene-related peptide (alpha-CGRP) and particle-induced osteolysis has been shown previously. The suggested osteoprotective influence of alpha-CGRP on the catabolic effects of ultra-high molecular weight polyethylene (UHMWPE) particles is analyzed in this study in primary human osteoblasts. METHODS: Primary human osteoblasts were stimulated by UHMWPE particles (cell/particle ratios 1:100 and 1:500) and different doses of alpha-CGRP (10(-7 )M, 10(-9 )M, 10(-11 )M). Receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) mRNA expression and protein levels were measured by RT-PCR and Western blot. RESULTS: Particle stimulation leads to a significant dose-dependent increase of RANKL mRNA in both cell-particle ratios and a significant down-regulation of OPG mRNA in cell-particle concentrations of 1:500. A significant depression of alkaline phosphatase was found due to particle stimulation. Alpha-CGRP in all tested concentrations showed a significant depressive effect on the expression of RANKL mRNA in primary human osteoblasts under particle stimulation. Comparable reactions of RANKL protein levels due to particles and alpha-CGRP were found by Western blot analysis. In cell-particle ratios of 1:100 after 24 hours the osteoprotective influence of alpha-CGRP reversed the catabolic effects of particles on the RANKL expression. INTERPRETATION: The in-vivo use of alpha-CGRP, which leads to down-regulated RANKL in-vitro, might inhibit the catabolic effect of particles in conditions of particle induced osteolysis.