The effects of local and systemic alendronate delivery on wear debris-induced osteolysis in vivo

Melittin Treats Periprosthetic Osteolysis in a Rat Model by Inhibiting the NF-kB Pathway and Regulating the Ratio of Receptor Activator of Nuclear Factor Kappa B Ligand/Osteoprotegerin

BACKGROUND

Aseptic loosening around the prosthesis is a common cause of failure in total joint arthroplasty. Polyethylene wear particles trigger the release of inflammatory factors by macrophages. Key mediators involved in osteoclastogenesis include interleukin-6, tumor necrosis factor-α, receptor activator of nuclear factor kappa B (RANK), RANK ligand (RANKL), and bone protection hormone (Osteoprotegerin [OPG]). The purpose of our experiment was to see whether melittin can slow down the release of inflammatory mediators through the NF-kB pathway, regulate the RANKL/OPG ratio, reduce osteoclast formation, and delay the onset of arthritis in rats.

METHODS

A total of 20 male Sprague-Dawley rats (10 months, Specific Pathogen Free, 350 g ± 20 g) were randomly divided into 5 groups: sham group, model group, melittin concentration 1 group (0.2 mg/kg), concentration 2 group (0.4 mg/kg), and concentration 3 group (0.6 mg/kg). All rats were implanted with TA2 high-purity titanium rods. A drill was used to create a bone canal along the long axis of the femur in the intercondylar notch. The model group and experimental groups were exposed to polyethylene particles, while the sham group did not receive any particles.

RESULTS

The melittin group exhibited significantly increased serum levels of serum P, calcium-phosphorus product, OPG, PINP, PINP/CTX-I, and OPG/RANKKL (P < .05). In the experimental group, micro computed tomography scanning results revealed a decrease in the amount of bone defect around the prosthesis. Immunofluorescence analysis demonstrated a decrease in the expression of IKKα and P65, while the expression of OPG showed an upward trend. Both Hematoxylin-Eosin and Tartrate-Resistant Acid Phosphatase staining revealed less osteoclast and inflammatory cell infiltration in bone resorption pits.

CONCLUSIONS

Our study demonstrates that melittin has the ability to inhibit the NF-kB pathway in a rat model, and reduce the impact of RANKL/OPG, thereby delaying osteoclast activity and alleviating periprosthetic osteolysis.

18F-FDG and 68 Ga-FAPI PET/CT for the evaluation of periprosthetic joint infection and aseptic loosening in rabbit models

Purpose

We built a joint replacement loosening model based on the original rabbit model of infection and evaluated the performance characteristics of ¹⁸F-FDG and ⁶⁸ Ga-FAPI in evaluating infection and loosening.

Methods

After surgery, the rabbits were divided into four groups, with six individuals in the control group and 10 each in the aseptic loosening, S. aureus and S. epidermidis groups. PET/CT and serological examination were performed three times at two-week intervals. After the rabbits were euthanized, micro-CT, tissue pathology, pullout tests and scanning electron microscopy (SEM) were performed.

Results

The pullout test and SEM showed the feasibility of the aseptic loosening model. ¹⁸F-FDG showed similar performance in the control and loosening groups. The SUVmax of the S. aureus group was consistently higher than that of the S. epidermidis group. As for ⁶⁸ Ga-FAPI, the SUVmax of the control group was lowest in the second week and gradually increased over subsequent weeks. The SUVmax of the loosening group began to exceed that of the control group after the second week. The SUVmax of the S. aureus group in the second week was the lowest among the four groups and increased as the number of weeks increased. The pathology results showed concordance with the performance of PET/CT. Linear regressions between SUVmax and serology showed that ¹⁸F-FDG was positively correlated with CRP and IL-6, while ⁶⁸ Ga-FAPI revealed negative correlations with CRP and IL-6 in the second week and positive correlations in the sixth week. In addition, the SUVmax and MT(target)V of both ¹⁸F-FDG and ⁶⁸ Ga-FAPI were negatively correlated with bone volume/trabecular volume (TV) and bone surface area/TV.

Conclusion

In this longitudinal observation, ⁶⁸ Ga-FAPI showed greater sensitivity than ¹⁸F-FDG in detecting diseases, and ⁶⁸ Ga-FAPI had no intestinal or muscular uptake. The MT(target)V of ⁶⁸ Ga-FAPI was larger than that of ¹⁸F-FDG, which meant that ⁶⁸ Ga-FAPI had the potential to define the scope of lesions more accurately. Finally, the SUVmax of ⁶⁸ Ga-FAPI could not differentiate between loosening and infection; further study of the diagnostic criteria is warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05537-w.

Magnesium lithospermate B inhibits titanium particles-induced osteoclast formation by c-fos and inhibiting NFATc1 expression

Purpose: Titanium particle-induced osteolysis is one of the important causes of aseptic loosening of artificial joints. Previous studies have shown the potential of natural compounds in preventing Ti particle-induced bone resorption. In this study, we observed the effects of magnesium lithospermate B (MLB) on titanium particle-induced osteoclast activity in vitro. Materials and Methods: RAW264.7 cells were treated with titanium particles (0.1 mg/mL) in the presence or absence of MLB (200 nmol/L). We evaluated the osteoclast formation, bone pits formation and tartrate-resistant acid phosphatase 5b (Tracp5b) levels. Reverse transcription polymerase chain reaction (RT-PCR) and Western blot were used to evaluate osteoclast differentiation-related genes (TRAF6, NFATc1, and c-fos) and protein expression. Results: The number of osteoclasts, pit formation and Tracp5b levels were all the group treated with titanium particles compared to the control group (all p < 0.05). Titanium particles also promoted the expression of the TRAF6, NFATc1 and c-fos genes and protein expression. MLB significantly abolished the titanium particle-enhanced osteoclast and pits formation, and Traf6, NFATc1, and c-fos expression. Conclusions: Our data demonstrated that MLB can suppress titanium-induced osteoclast activity via inhibiting c-fos and NFATc1 expression.

Effects of sequential treatment with intermittent parathyroid hormone and zoledronic acid on particle-induced implant loosening: Evidence from a rat model

Particle-induced implant loosening is a major challenge to long-term survival of joint prostheses. Administration of intermittent parathyroid hormone (PTH) has shown potential in the treatment of cases of early-stage periprosthetic osteolysis, while sequential administration of intermittent PTH (iPTH) and bisphosphonates (Bps) has achieved significant effects on treatment of postmenopausal osteoporosis. The objective of this study was to determine whether sequential treatment could preserve bone mass and implant fixation during a pathological course of peri-implant osteolysis in a rat model. Ninety male Sprague Dawley rats were randomly divided into nine groups, four of which were used for confirmation of establishment of the peri-implant osteolysis model at two time points, while the other five were used to determine the efficiency of the sequential treatment on peri-implant osteolysis. Implant fixation and peri-implant bone mass were evaluated using biomechanical testing, micro-CT analysis, and histology at 6 and 12 weeks postoperative. The biomechanical test demonstrated that the maximum loading force during a push-out test was significantly elevated in the sequential treatment group compared to the osteolysis group and iPTH withdrawal group at 12 weeks. Peri-implant bone morphology also indicated a robust increase in bone volume in the sequential treatment group. Sequential administration of iPTH and Bps was effective in preventing experimental peri-implant osteolysis, resulting in improved implant fixation and increased peri-implant bone volume. Clinical significance: The innovative application of sequential treatment in peri-implant osteolysis could be used clinically to improve the prognosis of patients with early-stage periprosthetic osteolysis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1489-1497, 2019.

Metal Nanoparticles Released from Dental Implant Surfaces: Potential Contribution to Chronic Inflammation and Peri-Implant Bone Loss

Peri-implantitis is an inflammatory disease affecting tissues surrounding dental implants. Although it represents a common complication of dental implant treatments, the underlying mechanisms have not yet been fully described. The aim of this study is to identify the role of titanium nanoparticles released form the implants on the chronic inflammation and bone lysis in the surrounding tissue. We analyzed the in vitro effect of titanium (Ti) particle exposure on mesenchymal stem cells (MSCs) and fibroblasts (FU), evaluating cell proliferation by MTT test and the generation of reactive oxygen species (ROS). Subsequently, in vivo analysis of peri-implant Ti particle distribution, histological, and molecular analyses were performed. Ti particles led to a time-dependent decrease in cell viability and increase in ROS production in both MSCs and FU. Tissue analyses revealed presence of oxidative stress, high extracellular and intracellular Ti levels and imbalanced bone turnover. High expression of ZFP467 and the presence of adipose-like tissue suggested dysregulation of the MSC population; alterations in vessel morphology were identified. The results suggest that Ti particles may induce the production of high ROS levels, recruiting abnormal quantity of neutrophils able to produce high level of metalloproteinase. This induces the degradation of collagen fibers. These events may influence MSC commitment, with an imbalance of bone regeneration.

Alendronate Release from UHMWPE-Based Biomaterials in Relation to Particle Size of the GUR Powder for Manufacturing

Ultra-high molecular weight polyethylene (UHMWPE) is widely used in endoprosthetics and has been the subject of countless studies. This project investigates the dependence of alendronate (AL) release on the molecular weight of the UHMWPE used (GUR1020 and GUR1050). A 0.5 wt% AL was added to the UHMWPE during the production of the moldings. In addition to the 14-day release tests, biocompatibility tests such as live dead assay, cell proliferation assay (WST) and Lactate dehydrogenase test (LDH) with MG-63 cells as well as a tensile test according to DIN EN ISO 527 were carried out. The released AL concentration was determined by HPLC. A continuous release of the AL was observed over the entire period of 2 weeks. In addition, a correlation between molar mass and AL release was demonstrated. The GUR1020 showed a release four times higher than the GUR1050. Both materials have no negative influence on the proliferation of MG-63 cells. This was also confirmed in the live/dead assay by the increase in cell count. No cytotoxicity was detected in the LDH test. The addition of 0.5 wt% AL increased the elongation at break for GUR1020 by 23% and for GUR1050 by 49%. It was demonstrated that the choice of UHMWPE has an influence on the release of AL. The particle size in particular has a strong influence on the release behavior.

Mechanical Properties and Porosity of Acrylic Cement Bone Loaded with Alendronate Powder

Aseptic loosening is the most common complication of joint replacement. Previous studies showed that acrylic bone cement loaded with a commercially-available alendronate powder (APAC) had good promise against wear debris-mediated osteolysis for prevention of aseptic loosening. The purpose of the present study was to investigate the effect of adding alendronate powder to an acrylic bone cement on quasi-static mechanical properties (namely, compressive strength, compressive modulus, tensile strength, and flexural strength), fatigue life, porosity, and microstructure of the cement. The results showed that adding up to 1 wt./wt.% alendronate powder exerted no detrimental effect on any of the quasi-static mechanical properties. However, the fatigue life of APAC decreased by between ~17% and ~27 % and its porosity increased by between ~ 5-7 times compared with corresponding values for the control cement (no alendronate powder added). Fatigue life was negatively and significantly correlated with porosity. Considering that fatigue life of the cement plays a significant role in joint replacement survival, clinical use of APAC cannot be recommended.

Arthrotomy-based preclinical models of particle-induced osteolysis: A systematic review

We completed a systematic literature review of in vivo animal models that use arthrotomy-based methods to study particle-induced peri-implant osteolysis. The purpose of the review was to characterize the models developed to date, to determine the questions addressed, to assess scientific rigor and transparency, and to identify gaps in knowledge. We probed three literature databases (Medline, Embase, and Scopus) and found 77 manuscripts that fit the search parameters. In the most recent 10 years, researchers mainly used rat and mouse models, whereas in the previous 20 years, large animal, canine, and rabbit models were more common. The studies have demonstrated several pathophysiology pathways, including macrophage migration, particle phagocytosis, increased local production of cytokines and lysosomal enzymes, elevated bone resorption, and suppressed bone formation. The effect of variation in particle characteristics and concentration received limited attention with somewhat mixed findings. Particle contamination by endotoxin was shown to exacerbate peri-implant osteolysis. The possibility of early diagnosis was demonstrated through imaging and biomarker approaches. Several studies showed that both local and systemic delivery of bisphosphonates inhibits the development of particle-induced osteolysis. Other methods of inhibiting osteolysis include the use of anabolic agents and altering the implant design. Few studies examined non-surgical rescue of loosened implants, with conflicting results with alendronate. We found that the manuscripts often lacked the methodological detail now advocated by the ARRIVE guidelines, suggesting that improvement in reporting would be useful to maximize rigor and transparency. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2595-2605, 2017.

Local influence of high molecular polyethylene particles on heterotopic ossification

We studied the effect of molecular polyethylene particles on local heterotopic ossification. A total of 36 healthy Sprague-Dawley rats were randomly divided into the control group (n=18) and the observation group (n=18). High molecular polyethylene particles were injected to rupture Achilles tendon position in the observation group, and normal saline was injected in the control group. X-ray examinations were conducted on Achilles tendon in the 4th, 8th and 12th week after operation. The incidence rate of heterotopic ossification was evaluated, and bone trabecula morphological structure was studied under optical microscope after hematoxylin and eosin staining. Bone morphogenetic protein 2 (BMP-2), transforming growth factor-β (TGF-β), interleukin-1 (IL-1), tumor necrosis factor-α (TNF-α), runt-related transcription factor 2 (Runx2) and matrix metalloproteinase-9 (MMP-9) expression levels were also measured. Our results showed that heterotopic ossification incidence in the observation group was significantly lower than that in the control group. Achilles tendon structure in the control group increased in volume, and its texture was harder and cartilage-like. In the observation group, trabecular bone volume, thickness and quantity were more than those observed in the control group. BMP-2, TGF-β, IL-1, TNF-α, Runx2 and MMP-9 levels in the observation group were significantly lower than those in the control group. We concluded that, high molecular polyethylene particles had a significant inhibiting effect on local heterotopic ossification.

Apoptotic pathways of macrophages within osteolytic interface membrane in periprosthestic osteolysis after total hip replacement

Macrophage apoptosis in interface membrane, which occurs through either death receptor, mitochondrion, or endoplasmic reticulum (ER) stress pathways, has been suggested to play an important role in promoting osteolysis. However, how and why macrophage apoptosis originates and the correlation among these apoptotic pathways is not yet clear. The objective of this study was to identify the apoptotic mechanism of macrophages, and to explore the relationship between the apoptotic pathways and progression of osteolysis. Transmission electron microscopy (TEM) was utilized to analyze the tissue ultrastructure of wear particles, and in situ apoptotic macrophage identification was performed by TUNEL staining. We analyzed the expression of the key biomarkers of apoptotic pathways via immunohistochemistry and Western blotting. Our results demonstrated that the majority of wear particles within osteolytic interface membrane was in the 30-60 nm range, and that macrophage apoptotic ratio increased along with osteolysis progression. Normal hip dysplasia and mechanical loosening of tissues showed low expression levels of biomarkers for ER stress (Ca²⁺ , JNK, cleaved Caspase-4, IRE1-α, Grp78/Bip, and CHOP), mitochondrion (Bcl-2, Bax, and Cytochrome c), and death receptor (Fas and cleaved Caspase-8) pathways, while osteolytic interface membrane tissues expressed high levels of these biomarkers. In addition, we found that the ER stress intensity was in complete conformity with mitochondrial dysfunction and was consistent with the results of death receptor activation. Thus, our findings suggested that wear particles generated at implant interface can accelerate macrophage apoptosis through changes in apoptotic pathways and ultimately aggravate the symptom of osteolysis. These data represent a preferential apoptotic signaling pathway of macrophages as specific target points for the prevention and therapeutic modulation of periprosthetic osteolysis.

Effect of low-dose X-ray irradiation and Ti particles on the osseointegration of prosthetic

Low-dose irradiation (LDI) exhibits a positive effect on osteoblasts and inhibitory effect of inflammation. Here, we test the hypothesis that LDI can promote osseointegration and inhibit the inflammatory membrane formation in the presence of titanium (Ti) particles. Endotoxin-free titanium particles were injected into rabbit, prior to the insertion of a Ti6-Al-4-V sticks pre-coated with hydroxyapatite. Two days after operation, both distal femurs of the animal were exposed to 0.5 Gy X-ray irradiation. All ani-mals were euthanized 8 weeks after the operation. The PINP concentration was determined at day 0, 2, 4, and 8 weeks after operation. Trabecular morphology around the implants 8 weeks after operation was assessed using micro-CT, then the maximum push out force of simples was assessed using biomechanics test. Five samples in each group were chosen for bone histomorphology study without decalcification 8 weeks after operation. The results confirmed that the LDI can significantly improve ingrowth of bone into the prosthetic interface and stability of the prosthesis when there was no wear particles. Although promotion effects for bone formation induced by LDI can be counteracted by wear particles, LDI can significantly inhibit the interface membrane formation around the implant induced by wear particles. Based on these results, we conclude that LDI may be useful for enhancing the stability of prosthesis when there are no wear particles and for inhibiting the interface membrane formation during the early stage of aseptic loosening in the presence of wear particles. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1688-1696, 2016.

Role of a nitrogenous bisphosphonate (local delivery) incorporated vitreous coating (with/without polymer) on surgical grade SS316L implant material to improve fixation at the damaged tissue site

This study demonstrates the material and biological properties of a unique osteogenic drug eluting (local) coating on load bearing SS316L implant material with a tunable release profile.

Intermittent Administration of Parathyroid Hormone [1-34] Prevents Particle-Induced Periprosthetic Osteolysis in a Rat Model

We examined whether intermittent administration of parathyroid hormone [1-34] (PTH[1-34]; 60 μg/kg/day) can prevent the negative effects of titanium (Ti) particles on implant fixation and periprosthetic osteolysis in a rat model. Eighteen adult male rats (12 weeks old, bones still growing) received intramedullary Ti implants in their bilateral femurs; 6 rats from the blank group received vehicle injections, and 12 rats from the control group and PTH treatment group received Ti particle injections at the time of operation and intra-articular injections 2 and 4 weeks postoperatively. Six of the rats that received Ti particles from the PTH group also received PTH[1-34] treatment. Six weeks postoperatively, all specimens were collected for assessment by X-ray, micro-CT, biomechanical, scanning electron microscopy (SEM), and dynamic histomorphometry. A lower BMD, BV/TV, Tb.N, maximal fixation strength, and mineral apposition rate were observed in the control group compared to the blank group, demonstrating that a periprosthetic osteolysis model had been successfully established. Administration of PTH[1-34] significantly increased the bone mineral density of the distal femur, BV/TV, Tb.N, Tb.Th, Tb.Sp, Con.D, SMI, and maximal fixation strength in the PTH group compared to that in the control group. SEM revealed higher bone-implant contact, thicker lamellar bone, and larger trabecular bone area in the PTH group than in the control group. A higher mineral apposition rate was observed in the PTH group compared to both the blank and control groups. These findings imply that intermittent administration of PTH[1-34] prevents periprosthetic osteolysis by promoting bone formation. The effects of PTH[1-34] were evaluated at a suprapharmacological dosage to the human equivalent in rats; therefore, additional studies are required to demonstrate its therapeutic potential in periprosthetic osteolysis.

The potential role of strontium ranelate in treating particle-induced osteolysis

Ultra high molecular weight polyethylene (UHMWPE) wear-particle-induced osteolysis is one of the major issues affecting the long-term survival of total joint prostheses. Currently, there are no effective therapeutic options to prevent osteolysis from occurring. The aim of this study was to evaluate the role of strontium ranelate (SR) in reducing the risk of particle-induced osteolysis. Forty-eight C57BL/6J ultra-high molecular weight polyethylene (UHMWPE) particle-induced murine calvarial osteolysis models were used. The mice were randomized into four groups as: sham (Group 1), UHMWPE particles (Group 2), and SR with UHMWPE particles (Group 3 and Group 4). Groups 1 to 3 were sacrificed at two weeks and group 4 was sacrificed at the fourth week. The skulls were then analyzed with a high-resolution micro-CT. Histological evaluation was then conducted and osteoclast numbers were analyzed for comparison. Based on the micro-CT, percentage bone volume and trabecular thickness were found to be significantly higher in Group 4 than in Group 2 (p<0.001). Osteoclast numbers in SR treated groups (Group 3 and Group 4) were reduced when compared to groups that did not receive SR treatment (Group 2). These results indicated that SR treatment helps to increase bone volume percentage and trabecular thickness and also suppresses osteoclast proliferation. It is suggested that oral SR treatment could serve as an alternative therapy for preventing particle-induced osteolysis.

Microbubble injection enhances inhibition of low-intensity pulsed ultrasound on debris-induced periprosthetic osteolysis in rabbit model

We determined whether the addition of microbubbles enhances the effect of low-intensity pulsed ultrasound (LIPUS) on bone-implant integration in an early-stage osteolysis model. The bone canals were injected with titanium particles before implantation to establish the periprosthetic osteolysis model. Before ultrasonic therapy, the microbubble-enhanced LIPUS group (GTi-Us-Mb) received an intra-articular injection of microbubbles. Biomechanical testing revealed that GTi-Us-Mb had significantly greater fixation strength than the LIPUS group (GTi-Us). Distal periprosthetic bone mineral density was also higher in GTi-Us than in the Ti group (GTi), but no significant increase was detected after administration of microbubbles. Histomorphometric analyses revealed that bone formation around the implant in GTi-Us was enhanced by the addition of microbubbles in GTi-Us-Mb. Taken together, our data indicate that microbubble injection enhances the inhibitory effect of LIPUS on debris-induced osteolysis and further strengthens the mechanical fixation of implants in an early-stage osteolysis model in vivo.

Are biologic treatments a potential approach to wear- and corrosion-related problems?

WHERE ARE WE NOW?: Biological treatments, defined as any nonsurgical intervention whose primary mechanism of action is reducing the host response to wear and/or corrosion products, have long been postulated as solutions for osteolysis and aseptic loosening of total joint arthroplasties. Despite extensive research on drugs that target the inflammatory, osteoclastic, and osteogenic responses to wear debris, no biological treatment has emerged as an approved therapy. We review the extensive preclinical research and modest clinical research to date, which has led to the central conclusion that the osteoclast is the primary target. We also allude to the significant changes in health care, unabated safety concerns about chronic immunosuppressive/antiinflammatory therapies, industry's complete lack of interest in developing an intervention for this condition, and the practical issues that have narrowly focused the possibilities for a biologic treatment for wear debris-induced osteolysis. WHERE DO WE NEED TO GO?: Based on the conclusions from research, and the economic, regulatory, and practical issues that limit the future directions toward the development of a biologic treatment, there are a few rational approaches that warrant investigation. These largely focus on FDA-approved osteoporosis therapies that target the osteoclast (bisphosphonates and anti-RANK ligand) and recombinant parathyroid hormone (teriparatide) prophylactic treatment to increase osseous integration of the prosthesis to overcome high-risk susceptibility to aseptic loosening. The other roadblock that must be overcome if there is to be an approved biologic therapy to prevent the progression of periprosthetic osteolysis and aseptic loosening is the development of radiological measures that can quantify a significant drug effect in a randomized, placebo-controlled clinical trial. We review the progress of volumetric quantification of osteolysis in animal studies and clinical pilots. HOW DO WE GET THERE?: Accepting the aforementioned rigid boundaries, we describe the emergence of repurposing FDA-approved drugs for new indications and public (National Institutes of Health, FDA, Centers for Disease Control and Prevention) and private (universities and drug and device manufactures) partnerships as the future roadmap for clinical translation. In the case of biologic treatments for wear debris-induced osteolysis, this will involve combined federal and industry funding of multicenter clinical trials that will be run by thought leaders at large medical centers.

The prevention of titanium-particle-induced osteolysis by OA-14 through the suppression of the p38 signaling pathway and inhibition of osteoclastogenesis

Wear-particle-induced osteolysis leads to prosthesis loosening, which is one of the most common causes of joint-implant failure, a problem that must be fixed using revision surgery. Thus, a potential treatment for prosthetic loosening is focused on inhibiting osteoclastic bone resorption, which prevents wear-particle-induced osteolysis. In this study, we synthesized a compound named OA-14 (N-(3- (dodecylcarbamoyl)phenyl)-1H-indole-2-carboxamide) and examined how OA-14 affects titanium (Ti)-particle-induced osteolysis and osteoclastogenesis. We report that OA-14 treatment protected against Ti-particle-induced osteolysis in a mouse calvarial model. Interestingly, the number of tartrate-resistant acid phosphatase-positive osteoclasts decreased after treatment with OA-14 in vivo, which suggested that OA-14 inhibits osteoclast formation. To test this hypothesis, we conducted in vitro studies, and our results revealed that OA-14 markedly diminished osteoclast differentiation and osteoclast-specific gene expression in a dose- and time-dependent manner. Moreover, OA-14 suppressed osteoclastic bone resorption and F-actin ring formation. Furthermore, we determined that OA-14 inhibited osteoclastogenesis by specifically blocking the p38-Mitf-c-fos-NFATc1 signaling cascade induced by RANKL (ligand of receptor activator of nuclear factor κB). Collectively, our results suggest that the compound OA-14 can be safely used for treating particle-induced peri-implant osteolysis and other diseases caused by excessive osteoclast formation and function.

Implant placement increases bone remodeling transiently in a rat model

To examine bone remodeling following implant placement, 88 female Sprague-Dawley rats underwent either sham ovariectomy (sham-ovx) or ovariectomy (ovx) at 4.5 months. At 11 months, 17 baseline control animals were euthanized, while 71 rats received bilateral intramedullary femoral implants. Implanted rats were randomized to 4-, 8-, or 12-week follow-up times. Microcomputed tomography was used to assess cortical area and trabecular architecture in all rats. Dynamic and static histomorphometry were performed in a subset to examine the trabecular and endocortical bone in the distal femoral metaphysis adjacent to the implant and the periosteal surface at the midshaft superior to the implant (n = 59). Implantation did not affect bone volume in either sham-ovx or ovx rats compared to baseline controls. Implant placement significantly increased mineralizing surface, mineral apposition rate, and bone formation rate in both sham-ovx and ovx rats at the trabecular and endocortical surfaces at four and sometimes 8 weeks, with a return to baseline values by 12 weeks. At the periosteal surface, implant placement increased bone formation at 4 weeks with a return to baseline levels by 8 weeks. Thus, implant placement increases bone remodeling transiently without affecting bone volume in sham-ovx and ovx rats.

Inhibitory effects of luteolin on titanium particle-induced osteolysis in a mouse model

Wear particles liberated from the surfaces of an implanted prosthesis are associated with peri-implant osteolysis and subsequent aseptic loosening. In the latter wear particle-induced inflammation and osteoclastogenesis have been identified as critical factors, and their inhibition as important steps in the treatment of affected patients, such as those undergoing total hip replacement. In this study the ability of luteolin to inhibit both titanium (Ti) particle-induced osteoclastogenesis in vitro and osteolysis in a murine calvaria Ti particle-induced model of osteolysis was examined. The results showed that luteolin, a highly potent and efficient inhibitor of tumor necrosis factor α (TNF-α) and interleukin-6 expression, inhibited Ti particle-induced inflammatory cytokine release, osteoclastogenesis, and bone resorption in bone marrow macrophages. Microcomputed tomography and histological analyses showed that the Ti particles caused significant bone resorption and increased TRAP(+) multinuclear osteoclasts in the murine calvarial model of osteolysis, whereas this was not the case in the luteolin treatment group, in which osteolytic suppression was accompanied by a decrease in both TNF-α production and serum levels of the osteoclast marker the C-terminal telopeptide fragment of type I collagen. These results support the use of luteolin as a natural compound in the prevention and treatment of aseptic loosening after total replacement arthroplasty.

Low-intensity pulsed ultrasound (LIPUS) may prevent polyethylene induced periprosthetic osteolysis in vivo

We investigated the effect of local low-intensity pulsed ultrasound (LIPUS) on polyethylene debris induced periprosthetic osteolysis. The periprosthetic osteolysis model was made by injecting endotoxin-free pure polyethylene particles into the distal part of the femur canal and inserting a stainless steel plug into this femur. The effects of polyethylene and LIPUS were assessed histologically and by the shear strength test and periprosthetic bone mineral density (BMD) test. Sixteen rabbits received a stainless steel plug on one side and both polyethylene and a stainless steel plug on the other side. Three months later, the side that received polyethylene showed periprosthetic osteolysis. Subsequently, another 16 rabbits received polyethylene plus local LIPUS (200 mW/cm(2) for 20 min daily) on one side and polyethylene alone on the other side. Three months later, LIPUS effectively prevented the periprosthetic osteolysis caused by polyethylene in this rabbit model.