The most common reason for revision surgery of total hip replacements is aseptic loosening of implants secondary to osteolysis, which is caused by immune-mediated reactions to implant debris. These debris can cause pseudotumour formation. As revision surgery is associated with higher mortality and infection, it is important to understand the pro-inflammatory process to improve implant survival. Toll-like receptor 4 (TLR4) has been shown to mediate immune responses to cobalt ions. Statin use in epidemiological studies has been associated with reduced risk of revision surgery. In-vitro studies have demonstrated the potential for statins to reduce orthopaedic debris-induced immune responses and there is evidence that statins can modulate TLR4 activity. This study investigates simvastatin's effect on orthopaedic biomaterial-mediated changes in protein expression of key inflammatory markers and soluble-ICAM-1 (sICAM-1), an angiogenic factor implicated in pseudotumour formation. Human macrophage THP-1 cells were pre-incubated with 50µM simvastatin for 2-hours or a vehicle control (VC), before being exposed to 0.75mM cobalt chloride, 50μm3 per cell zirconium oxide or LPS as a positive control, in addition to a further 24-hour co-incubation with 50µM simvastatin or VC. Interleukin −8 (IL-8), sICAM-1, chemokine ligand 2 (CCL2), CCL3 and CCL4 protein secretion was measured by enzyme-linked immunosorbent assay (ELISA). GraphPad Prism 10 was used for statistical analysis including a one-way ANOVA. Pre-treatment with simvastatin significantly reduced LPS and cobalt-mediated IL-8 secretion (n=3) and sICAM-1 protein secretion (n=2) in THP-1 cells. Pre-treatment with simvastatin significantly reduced LPS-mediated but not cobalt ion-mediated CCL2 (n=3) and CCL3 protein (n=3) secretion in THP-1 cells. Simvastatin significantly reduced zirconium oxide-mediated CCL4 secretion (n=3). Simvastatin significantly reduced cobalt-ion mediated IL-8 and sICAM-1 protein secretion in THP-1 cells. This in-vitro finding demonstrates the potential for simvastatin to reduce recruitment of leukocytes which mediate the deleterious inflammatory processes driving implant failure

Introduction and Objective. Total joint replacement is indicated for osteoarthritis where conservative treatment has failed, and in the UK the number of patients requiring hip and knee replacements is set to increase with an ageing population. Survival of total hip replacements is around 85% at 20 years with the most common reason for revision being aseptic loosening of the implant secondary to osteolysis, which is caused by immune-mediated reactions to implant debris. These debris can also cause pseudotumour formation. As revision surgery is associated with higher morbidity, mortality, infection rates, venous thromboembolism, resource demand and poorer subsequent function it is important to understand the mechanisms underlying the pro-inflammatory process to improve implant survival. Toll-like receptor 4 (TLR4), an innate immune receptor, has been demonstrated to mediate deleterious immune responses by the Tyson-Capper research group, including inflammatory cytokine interleukin-8 (IL-8) secretion. Statin use in epidemiological studies has been associated with reduced overall risk of revision surgery after hip replacement. In-vitro studies have demonstrated the potential for statins to reduce orthopaedic debris-induced immune responses which can lead to osteolysis and pseudotumour formation. As literature from cardiological investigations demonstrate that statins can reduce the expression and responsiveness of TLR4, this could be an exciting mechanism to exploit to reduce the host immune response to orthopaedic wear debris, thereby improving implant survival by reducing immune mediated osteolysis. This ongoing study investigates simvastatin's effect on cobalt ion-mediated changes in gene and protein expression of interleukin-8 and soluble-ICAM-1 (sICAM-1) which is an angiogenic factor implicated in pseudotumour formation. Materials and Methods. TLR4-expressing human monocyte/macrophage THP-1 cells were pre-incubated with 50μM simvastatin for 2-hours or a vehicle control, before being exposed to exposed to 0.75mM cobalt chloride, in addition to a further 24-hour co-incubation with 50μM simvastatin or vehicle control. IL-8 protein and sICAM-1 secretion was measured by enzyme-linked immunosorbent assay (ELISA). Gene expression changes were quantified by TaqMan-based real time polymerase chain reaction. Results. Pre-treatment with simvastatin significantly reduced cobalt-mediated IL-8 protein secretion (n=3) and sICAM-1 protein secretion (n=2) in THP-1 cells (p-value<0.0001). Work will be undertaken to determine changes in gene expression, the role of TLR4 in these responses and the effect of simvastatin on additional inflammatory markers. Conclusions. Simvastatin significantly reduces cobalt-ion mediated IL-8 and sICAM-1 protein secretion in THP-1 cells. This in-vitro finding demonstrates the potential for simvastatin to reduce recruitment of leukocytes which mediate the deleterious inflammatory processes driving aseptic loosening and pseudotumour formation

Several observational and experimental studies have investigated the potential anabolic effects of statins on undisturbed bone but only a few recent studies have examined the effect of statins on skeletal repair. The goal of the study is to investigate any potential early anabolic effect of the systemic administration of simvastatin in low doses (based on earlier safety and efficacy studies on undisturbed bone) on fracture healing. Fifty-four skeletally mature male New Zealand White rabbits were used for the study. The rabbits were assigned to one of three experimental groups: a control group, and two groups that were orally administrated a diet with 10 and 30 mg/kg/day of simvastatin, respectively. A complete biochemical blood count was performed to exclude drug-induced complications. Half of the animals of each group were sacrificed at 15 days and the other half at 30 days after surgery at which time intervals healing quality was assessed. The bones were subjected to biomechanical testing, histomorphometric analysis and peripheral Quantitative Computed Tomography. In animals received simvastatin of 30 mg/kg/day a significant reduction of BMD, stiffness, and energy absorbed to failure were observed. At 15 days, the amount of cartilaginous callus formation was reduced, and the void space was significantly increased, in the animals of both groups that received simvastatin when compared to the control group (p< .05). Our results suggest that simvastatin doses of 30mg/ kg/day may have a negative anabolic effect on callus formation in rabbits, whereas doses of 10 mg/kg/day seem not to produce a significant positive or a negative effect, especially at the early stages of fracture remodeling

Introduction: Approximately 15% of fractures account for delayed or impaired healing. The popularity of new. Methods: that enhance fracture healing along with conventional ones is growing. The purpose of this study was to determine the effects, the safety and the efficacy of systemic simvastatin administration to bone healing. Materials and Methods: Unilateral mid-ulnar osteotomies (approximately 2.0 mm wide) were performed to 56 skeletally mature male rabbits. The limbs were assigned to one of three groups: those treated with 30 mg/kg/day of simvastatin per os, those administered with 10 mg/kg/day of simvastatin orally and the control group. The rabbits were killed at two or four weeks postoperatively after taking blood samples for biochemical analysis to detect drug-induced side effects. After the rabbits were killed, the limbs were scanned with peripheral quantitative computed tomography to assess the area and mineral content of the mineralized callus. The bones were subjected to mechanical bending testing and histomorphometry. Results: At 2 weeks the total density for the mineralized callus was on average 531.7±32.7 for the control group, 466.05±10.6 for the first group (p< .01) and at 4 weeks the total density was 617.5±12.42 for the control group, 551.26±27.61 for the first group, and 553.72±20.66 for the second group respectively (p< .001). Biomechanical properties were similar to all groups at 2 and 4 weeks. The% cartilage portion area was 17.28±2.61 for the control group, 11.89±1.84 for the first group (p< .001) and 14.06±2.17 for the second group (p< .05). Discussion: The data show that daily systemic administration of simvastatin in 30 mg/kg/day or 10 mg/kg/day do not seem to produce a clear anabolic effect in fracture healing through the remodeling phase. Conclusion: The use of simvastatin to promote fracture healing is still under study. The limitations from its use are the side effects from its systematic administration over 30 mg/kg/day. Most likely, alternative ways of administration should be considered for future studies

Simvastatin is a 3-Hydroxy-3-methylglutaryl Co-enzyme inhibitor, widely used to reduce lipid levels. Recent studies have demonstrated pleiotropic beneficial effects the skeleton. We aim to demonstrate the effect of Simvastatin on the osteogenic differentiation and proliferation of murine embryonic stem cells. Tg2a cells were cultured in maintenance medium until confluence and passaged twice into tissue culture flasks. They were then seeded into 6 well and 24 well plates at a density of 10.000 cells/cm2 and cultured for 3 days in maintenance medium mixed at 1:1 with HepG2 conditioned medium. The culture then continued using osteogenic medium with different concentrations of simvastatin for another 16 days. Measurements included Alizarin Red quantification for calcified matrix, ALP assay, RT-PCR for genes expressed during osteogenic differentiation (osteocalcin, Runx2, osterix, Col1a1). Simvastatin has dose dependent effect on mineralized matrix formation. Alizarin Red quantification assays demonstrated that simvastatin (all dose groups) induced a statistically significant increase in calcified matrix formation on day 11 (P< 0.05) and 16 (P< 0.01) compared to the control group. ALP activity was significantly higher on day 8 in the groups that had a simvastatin concentration of 1nM, 10nM and 100nM (P< 0.05). RT-PCR has demonstrated that simvastatin caused increased expression of all genes measured on differentiation. Statins can induce bone formation when combined with embryonic stem cells

Introduction: It has been suggested that statins may influence bone turnover via an effect on bone morphogenic protein 2 (BMP-2). While the effect on statins in the prevention of osteoporosis remains controversial there is some evidence that they may exert a significant effect on fracture healing. Using a newly developed fracture model of the proximal tibia of the rat, the effect of simvastatin on osteoporotic and non-osteoporotic fracture healing was investigated. The fracture model was used as it provided a useful model of metaphyseal fracture healing which is particularly relevant to osteoporotic fracture. Methods: Four groups of 20 3-month-old female Wistar rats were used. Half underwent ovariectomy (ovx) while the remainder had a sham procedure. 8 weeks later a fracture was created in the proximal tibia of each animal by three point bending. The fractures were supported by a narrow intramedullary k-wire. 20 sham and 20 ovx animals were then fed 20mg/kg simvastatin by gavage for 14 days while the rest received placebo. 10 animals from each group were sacrificed at 2 weeks post surgery while the rest were sacrificed at 4 weeks. X-rays of the healing fractures were taken. Both the intact and fractures tibiae were then taken for mechanical testing by four point bending. Results: Six animals (7.5%) were excluded because of fracture comminution (5) or loss of stabilisation (1). There was a similar radiological appearance in all 4 groups at each time point. At two weeks: there was no difference in the mechanical properties of the healing bone between the groups. At 4 weeks the fractured and intact tibiae from the sham animals had an equal ultimate load at failure to their intact tibiae. However, the fractured tibiae from the ovx animals remained weaker (ovx & placebo 68%, ovx & statin 60.5% of ultimate load at failure compared with intact tibia). The difference between the fractures ultimate load in ovx and sham animals was statistically significant (p=0.0105). No difference was seen between the statin and placebo group. Discussion: This work provides evidence that a metaphyseal fracture in the osteoporotic rat model is able to withstand significantly less load at 4 weeks than a fracture from a sham ovx animal suggesting fracture healing is slower in osteoporotic individuals. Simvastatin at 20mg/kg had no effect on the mechanical properties of normal or osteoporotic fracture healing in this study

Aims. To evaluate the effect of ultrasound-targeted simvastatin-loaded microbubble destruction (UTMDSV) for alleviation of the progression of osteoarthritis (OA) in rabbits through modulation of the peroxisome proliferator-activated receptor (PPARγ). Methods. In vitro, OA chondrocytes were treated with ultrasound (US), US-targeted microbubble destruction (UTMD), simvastatin (SV), and UTMDSV on alternate days for four weeks. Chondrocytes were also treated with PPARγ inhibitor, PPARγ inhibitor+ UTMDSV, and UTMDSV. The cholesterol efflux rate and triglyceride levels were measured using an assay kit and oil red O staining, respectively. In vivo, the OA rabbits were treated with a single intra-articular injection of UTMD, SV, and UTMDSV every seven days for four weeks. Cartilage histopathology was assessed by safranin-O staining and the Mankin score. Total cholesterol (TC) and high-density lipoprotein-cholesterol (HDL-C) in rabbit knee synovial fluid were detected by enzyme-marker assay. Aggrecan, collagen II, and PPARγ expression levels were analyzed by Western blotting (WB). Results. In vitro, UTMDSV significantly increased the cholesterol efflux rate and aggrecan, collagen II, and PPARγ levels in OA chondrocytes; these effects were blocked by the PPARγ inhibitor. In vivo, UTMD. SV. significantly increased aggrecan, collagen II, PPARγ, and HDL-C levels, while TC levels and Mankin scores were decreased compared with the UTMD, SV, OA, and control groups. Conclusion. UTMDSV promotes cartilage extracellular matrix synthesis by modulating the PPARγ-mediated cholesterol efflux pathway in OA rabbits. Cite this article: Bone Joint Res 2021;10(10):693–703

Introduction. Problematic bone defects are encountered regularly in orthopaedic practice particularly in fracture non-union, revision hip and knee arthroplasty, following bone tumour excision and in spinal fusion surgery. At present the optimal source of graft to ‘fill’ these defects is autologous bone but this has significant drawbacks including harvest site morbidity and limited quantities. Bone marrow has been proposed as the main source of osteogenic stem cells for the tissue-engineered cell therapy approach to bone defect management. Such cells constitute a minute proportion of the total marrow cell population and their isolation and expansion is a time consuming and expensive strategy. In this study we investigated human bone marrow stem cells as a potential treatment of bone defect by looking at variability in patient osteogenic cell populations as a function of patient differences. We produced a model to predict which patients would be more suited to cell based therapies and propose possible methods for improving the quality of grafts. Methods. Bone marrow was harvested from 30 patients undergoing elective total hip replacement surgery in Musgrave Park Hospital, Belfast (12 males, 18 females, age range 52-82 years). The osteogenic stem cell fraction was cultured and subsequently analysed using colony forming efficiency assays, flow cytometry, fluorescence activated cell sorting and proteomics. Results. The number and proliferative capacity of osteogenic stem cells varied markedly between patients. Statistical analysis revealed significantly better osteogenic capacity in:. male patients. samples in which the growth hormone Fibroblastic Growth Factor-2 was added to culture medium. patients who used the cholesterol lowering agent simvastatin. Patient use of inhaled steroids and NSAIDs were found to have detrimental effects. A statistical model to predict marrow profiles based on these variables was produced. Conclusions. Stem cell based tissue engineering represents the future of the treatment of bone defect. This study provides evidence that inter-patient variability in marrow cell colony forming and proliferation ability can in some way be explained by patient associated factors. Using this knowledge, we can identify which patients would be best suited to this method of treatment and propose techniques for enhancement of their graft profiles

Aims

The success of anterior cruciate ligament reconstruction (ACLR) depends on osseointegration at the graft-tunnel interface and intra-articular ligamentization. Our aim was to conduct a systematic review of clinical and preclinical studies that evaluated biological augmentation of graft healing in ACLR.

Aims

Cigarette smoking has a negative impact on the skeletal system, causes a decrease in bone mass in both young and old patients, and is considered a risk factor for the development of osteoporosis. In addition, it disturbs the bone healing process and prolongs the healing time after fractures. The mechanisms by which cigarette smoking impairs fracture healing are not fully understood. There are few studies reporting the effects of cigarette smoking on new blood vessel formation during the early stage of fracture healing. We tested the hypothesis that cigarette smoke inhalation may suppress angiogenesis and delay fracture healing.

Objectives

The primary purpose of this meta-analysis was to determine whether statin usage could reduce the risk of glucocorticoid-related osteonecrosis in animal models.