RESUMO
Particles released from implants cause inflammatory bone loss, which is a key factor in aseptic loosening, the most common reason for joint replacement failure. With the anticipated increased incidence of total joint replacement in the next decade, implant failure will continue to burden patients. The gut microbiome is increasingly recognized as an important factor in bone physiology, however, its role in implant loosening is currently unknown. We tested the hypothesis that implant loosening is associated with changes in the gut microbiota in a preclinical model. When the particle challenge caused local joint inflammation, decreased peri-implant bone volume, and decreased implant fixation, the gut microbiota was affected. When the particle challenge did not cause this triad of local effects, the gut microbiota was not affected. Our results suggest that cross-talk between these compartments is a previously unrecognized mechanism of failure following total joint replacement.
Assuntos
Microbioma Gastrointestinal , Inflamação/patologia , Osteólise/patologia , Próteses e Implantes/efeitos adversos , Infecções Relacionadas à Prótese/patologia , Animais , Inflamação/etiologia , Masculino , Osteólise/etiologia , Infecções Relacionadas à Prótese/etiologia , RatosRESUMO
OBJECTIVE: To assess the ability of sclerostin antibody therapy to blunt the negative effects of polyethylene particles on implant fixation and peri-implant bone structure in a rat implant fixation model. METHODS: Thirty-six adult male rats received intramedullary titanium implants; 12 rats received vehicle injections only (control), and 24 rats received intraarticular injections of lipopolysaccharide-doped polyethylene particles. Twelve of the rats that received particles also received sclerostin antibody treatment. The 3 groups of rats were maintained for 12 weeks in a pathogen-free environment, at which time mechanical, micro-computed tomography, and dynamic and static histomorphometry end points were assessed. RESULTS: Sclerostin antibody treatment completely blocked the negative effect of the lipopolysaccharide-doped polyethylene particles on implant fixation and peri-implant bone volume by increasing the bone formation rate and depressing bone resorption. CONCLUSION: Anabolic agents targeting the Wnt signaling pathway are a promising new alternative for the prevention of periprosthetic osteolysis and aseptic loosening.
Assuntos
Anticorpos/farmacologia , Proteínas Morfogenéticas Ósseas/imunologia , Reabsorção Óssea/prevenção & controle , Marcadores Genéticos/imunologia , Osteogênese/efeitos dos fármacos , Polietileno/efeitos adversos , Próteses e Implantes , Falha de Prótese/etiologia , Animais , Anticorpos/imunologia , Anticorpos/uso terapêutico , Reabsorção Óssea/fisiopatologia , Fêmur/diagnóstico por imagem , Fêmur/fisiologia , Fêmur/cirurgia , Masculino , Modelos Animais , Osteogênese/fisiologia , Ratos , Ratos Sprague-Dawley , Transdução de Sinais/fisiologia , Titânio , Tomografia Computadorizada por Raios X , Proteínas Wnt/fisiologiaRESUMO
BACKGROUND: Stem cell mobilization, which is defined as the forced egress of stem cells from the bone marrow to the peripheral blood (PB) using chemokine receptor agonists, is an emerging concept for enhancing tissue regeneration. However, the effect of stem cell mobilization by a single injection of the C-X-C chemokine receptor type 4 (CXCR4) antagonist AMD3100 on intramembranous bone regeneration is unclear. QUESTIONS/PURPOSES: We therefore asked: Does AMD3100 mobilize adult stem cells in C57BL/6 mice? Are stem cells mobilized to the PB after marrow ablation? And does AMD3100 enhance bone regeneration? METHODS: Female C57BL/6 mice underwent femoral marrow ablation surgery alone (n = 25), systemic injection of AMD3100 alone (n = 15), or surgery plus AMD3100 (n = 57). We used colony-forming unit assays, flow cytometry, and micro-CT to investigate mobilization of mesenchymal stem cells, endothelial progenitor cells, and hematopoietic stem cells to the PB and bone regeneration. RESULTS: AMD3100 induced mobilization of stem cells to the PB, resulting in a 40-fold increase in mesenchymal stem cells. The marrow ablation injury mobilized all three cell types to the PB over time. Administration of AMD3100 led to a 60% increase in bone regeneration at Day 21. CONCLUSIONS: A single injection of a CXCR4 antagonist lead to stem cell mobilization and enhanced bone volume in the mouse marrow ablation model of intramembranous bone regeneration.
Assuntos
Células-Tronco Adultas/efeitos dos fármacos , Regeneração Óssea/efeitos dos fármacos , Movimento Celular/efeitos dos fármacos , Fêmur/efeitos dos fármacos , Mobilização de Células-Tronco Hematopoéticas/métodos , Compostos Heterocíclicos/farmacologia , Células-Tronco Adultas/imunologia , Animais , Benzilaminas , Medula Óssea/efeitos dos fármacos , Medula Óssea/cirurgia , Proliferação de Células/efeitos dos fármacos , Ensaio de Unidades Formadoras de Colônias , Ciclamos , Células Endoteliais/efeitos dos fármacos , Feminino , Fêmur/diagnóstico por imagem , Fêmur/imunologia , Fêmur/cirurgia , Citometria de Fluxo , Células-Tronco Hematopoéticas/efeitos dos fármacos , Células-Tronco Mesenquimais/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Modelos Animais , Projetos Piloto , Receptores CXCR4/antagonistas & inibidores , Receptores CXCR4/metabolismo , Regeneração/efeitos dos fármacos , Fatores de Tempo , Microtomografia por Raio-XRESUMO
Bone microarchitectural parameters significantly contribute to implant fixation strength but the role of bone matrix composition is not well understood. To determine the relative contribution of microarchitecture and bone matrix composition to implant fixation strength, we placed titanium implants in 12-week-old intact Sprague-Dawley rats, ovariectomized-Sprague-Dawley rats, and Zucker diabetic fatty rats. We assessed bone microarchitecture by microcomputed tomography, bone matrix composition by Raman spectroscopy, and implant fixation strength at 2, 6, and 10 weeks postimplantation. A stepwise linear regression model accounted for 83.3% of the variance in implant fixation strength with osteointegration volume/total volume (50.4%), peri-implant trabecular bone volume fraction (14.2%), cortical thickness (9.3%), peri-implant trabecular crystallinity (6.7%), and cortical area (2.8%) as the independent variables. Group comparisons indicated that osseointegration volume/total volume was significantly reduced in the ovariectomy group at Week 2 (~28%) and Week 10 (~21%) as well as in the diabetic group at Week 10 (~34%) as compared with the age matched Sprague-Dawley group. The crystallinity of the trabecular bone was significantly elevated in the ovariectomy group at Week 2 (~4%) but decreased in the diabetic group at Week 10 (~3%) with respect to the Sprague-Dawley group. Our study is the first to show that bone microarchitecture explains most of the variance in implant fixation strength, but that matrix composition is also a contributing factor. Therefore, treatment strategies aimed at improving bone-implant contact and peri-implant bone volume without compromising matrix quality should be prioritized.
Assuntos
Implantes Experimentais , Osseointegração , Animais , Feminino , Humanos , Ovariectomia , Ratos , Ratos Sprague-Dawley , Ratos Zucker , Titânio , Microtomografia por Raio-X/métodosRESUMO
In 2021, the American Association for Anatomy (AAA) Board of Directors appointed a Task Force on Structural Racism to understand how the laws, rules, and practices in which the Association formed, developed and continues to exist affect membership and participation. This commentary is the first public report from the Task Force. We focus on African Americans with some comments on Jews and women, noting that all marginalized groups deserve study. Through much of its 130 year history, some members were an essential part of perpetuating racist ideas, the Association largely ignored racism and had some practices that prevented participation. The Task Force concluded that individual and structural racism within the AAA, combined with the broader social context in which the Association developed, contributed to the current underrepresentation of African Americans who constitute 4.1% of the membership even though 13.4% of the U.S. population is Black. Intentional efforts within the AAA to reckon with racism and other forms of bias have only begun in the last 10-20 years. These actions have led to more diverse leadership within the Association, and it is hoped that these changes will positively affect the recruitment and retention of marginalized people to science in general and anatomy in particular. The Task Force recommends that the AAA Board issue a statement of responsibility to acknowledge its history. Furthermore, the Task Force advocates that the Board commit to (a) sustaining ongoing projects to improve diversity, equity, and inclusion and (b) dedicating additional resources to facilitate novel initiatives.
Assuntos
Racismo , Negro ou Afro-Americano , Feminino , Humanos , Racismo Sistêmico , Estados UnidosRESUMO
OBJECTIVE: To verify the biologic links between progressive cellular and structural alterations within knee joint components and development of symptomatic chronic pain that are characteristic of osteoarthritis (OA), and to investigate the molecular basis of alterations in nociceptive pathways caused by OA-induced pain. METHODS: An animal model of knee joint OA pain was generated by intraarticular injection of mono-iodoacetate (MIA) in Sprague-Dawley rats, and symptomatic pain behavior tests were performed. Relationships between development of OA with accompanying pain responses and gradual alterations in cellular and structural knee joint components (i.e., cartilage, synovium, meniscus, subchondral bone) were examined by histologic and immunohistologic analysis, microscopic examination, and microfocal computed tomography. Progressive changes in the dynamic interrelationships between peripheral knee joint tissue and central components of nociceptive pathways caused by OA-induced pain were examined by investigating cytokine production and expression in sensory neurons of the dorsal root ganglion and spinal cord. RESULTS: We observed that structural changes in components of the peripheral knee joint correlate with alterations in the central compartments (dorsal root ganglia and the spinal cord) and symptomatic pain assessed by behavioral hyperalgesia. Our comparative gene expression studies revealed that the pain pathways in MIA-induced knee OA may overlap, at least in part, with neuropathic pain mechanisms. Similar results were also observed upon destabilization of the knee joint in the anterior cruciate ligament transection and destabilization of the medial meniscus models of OA. CONCLUSION: Our results indicate that MIA-induced joint degeneration in rats generates an animal model that is suitable for mechanistic and pharmacologic studies on nociceptive pain pathways caused by OA, and provide key in vivo evidence that OA pain is caused by central sensitization through communication between peripheral OA nociceptors and the central sensory system. Furthermore, our data suggest a mechanistic overlap between OA-induced pain and neuropathic pain.
Assuntos
Artralgia/fisiopatologia , Gânglios Espinais/fisiopatologia , Articulação do Joelho/inervação , Nociceptores/fisiologia , Osteoartrite do Joelho/fisiopatologia , Medula Espinal/fisiopatologia , Animais , Artrite Experimental , Condrócitos/metabolismo , Condrócitos/patologia , Osteoartrite do Joelho/patologia , Ratos , Ratos Sprague-DawleyRESUMO
Biomarkers are of interest to identify patients at risk for peri-implant osteolysis and aseptic loosening. We used a rat model of particle-induced peri-implant osteolysis to investigate if early changes in biomarkers were associated with subsequent implant fixation strength. Implants were placed in rat femora, which were then challenged with intra-articular knee injections of either clean polyethylene, lipopolysaccharide-doped polyethylene, or cobalt-chromium alloy particles, with particle-free vehicle serving as control (n ≥ 8 per group). Rats were weighed weekly, blood was collected at weeks 0, 3, 5, and 6, and locomotor behavior was assessed 4 days before study conclusion. Rats were euthanized 6 weeks post surgery. Week 6 serum was analyzed for five bone remodeling markers, while longitudinal serum was assessed for osteocalcin. Bone-implant contact, peri-implant trabecular architecture, and implant fixation strength were measured. Rats challenged with cobalt-chromium particles had a significant reduction in implant fixation strength compared with the vehicle-control group (P = .034). This group also had elevated serum osteocalcin (P = .005), depressed weight gain (P = .001) and less frequent rearing behavior (P = .029). Regardless of group, change in serum osteocalcin at week 3 (r = -.368; P = .046), change in weight at week 2 (r = .586; P < .001), as well as weight change at all other time intervals were associated with fixation strength. The finding that early alterations in serum osteocalcin and body weight were predictive of subsequent implant fixation strength supports continued investigation of biomarkers for early detection of peri-implant osteolysis and implant loosening. Further, change in biomarker levels was found to be more indicative of implant fixation status than any single measurement.
Assuntos
Peso Corporal , Implantes Experimentais/efeitos adversos , Osteocalcina/sangue , Animais , Biomarcadores/sangue , Remodelação Óssea , Lipopolissacarídeos/farmacologia , Masculino , Atividade Motora , Osteólise , Polietileno/farmacologia , Ratos , Ratos Sprague-DawleyRESUMO
Mechanical fixation of the implant to host bone is an important contributor to orthopedic implant survivorship. The relative importance of bone-implant contact, trabecular bone architecture, and cortical bone geometry to implant fixation strength has never been directly tested, especially in the settings of differential implant surface properties. Thus, using a rat model where titanium rods were placed into the intramedullary canal of the distal femur, we determined the relative contribution of bone-implant contact and peri-implant bone architecture to the fixation strength in implants with different surface roughness: highly polished and smooth (as-received) and dual acid-etched (DAE) implants. Using a training set that maximized variance in implant fixation strength, we initially examined correlation between implant fixation strength and outcome parameters from microcomputed tomography and found that osseointegration volume per total volume (OV/TV), trabecular bone volume per total volume (BV/TV), and cortical thickness (Ct.Th) were the single best compartment-specific predictors of fixation strength. We defined separate regression models to predict implant fixation strength for as-received and DAE implants. When the training set models were applied to independent validation sets, we found strong correlations between predicted and experimentally measured implant fixation strength, with r2 = .843 in as received and r2 = .825 in DAE implants. Interestingly, for as-received implants, OV/TV explained more of the total variance in implant fixation strength than the other variables, whereas in DAE implants, Ct.Th had the most explanatory power, suggesting that surface topography of implants affects which bone compartment is most important in providing implant fixation strength.
Assuntos
Implantes Experimentais , Animais , Fenômenos Biomecânicos , Calcificação Fisiológica , Osseointegração , Ratos , Ratos Sprague-Dawley , Propriedades de SuperfícieRESUMO
To test how osteoporosis drugs affect bone matrix maturation during cortical bone remodeling, 72 pregnant rats were switched from a 0.4% to a 0.01% calcium diet at parturition for a 23-day lactation period. At weaning, eight dams were sacrificed to establish baseline values, while the remaining dams were returned to 0.4% calcium and treated with vehicle (saline), sodium fluoride (NaF), zoledronic acid (ZA), or sclerostin antibody (Scl-Ab) for either 7 or 28 days (eight animals per group per time point). Femora were examined by µCT, dynamic histomorphometry, Fourier transform infrared imaging, and three-point bending of notched specimens. Cortical porosity decreased in all groups from baseline to day 28. Intracortical mineralizing surface (MS/BS) and mineral apposition rate (MAR), as well as the mineral-to-matrix ratio were unaffected by treatment, but intracortical crystallinity was increased in the ZA group at day 10 compared with vehicle. Cortical area increased in all groups over 28 days mainly because of an addition of bone at the endocortical surface. Endocortical MS/BS did not vary among the groups, but endocortical MAR was suppressed in the NaF group at day 2 and elevated in the Scl-Ab group at day 4 compared with vehicle. Endocortical mineral-to-matrix ratio was increased at days 5 and 10 following NaF treatment and endocortical crystallinity was increased at day 5 following ZA treatment compared with vehicle. Fracture toughness did not differ among the groups. Thus, the treatments affected matrix maturation more strongly at the endocortical then intracortical envelope. In this model of induced remodeling, the bone formation phase is synchronized at multiple sites, facilitating study of the effects of drugs or other bone-targeting agents on matrix maturation independent of their effects on the initiation of remodeling. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
RESUMO
Histology and backscatter scanning electron microscopy (bSEM) are the current gold standard methods for quantifying bone-implant contact (BIC), but are inherently destructive. Microcomputed tomography (µCT) is a non-destructive alternative, but attempts to validate µCT-based assessment of BIC in animal models have produced conflicting results. We previously showed in a rat model using a 1.5 mm diameter titanium implant that the extent of the metal-induced artefact precluded accurate measurement of bone sufficiently close to the interface to assess BIC. Recently introduced commercial laboratory µCT scanners have smaller voxels and improved imaging capabilities, possibly overcoming this limitation. The goals of the present study were to establish an approach for optimizing µCT imaging parameters and to validate µCT-based assessment of BIC. In an empirical parametric study using a 1.5 mm diameter titanium implant, we determined 90 kVp, 88 µA, 1.5 µm isotropic voxel size, 1600 projections/180°, and 750 ms integration time to be optimal. Using specimens from an in vivo rat experiment, we found significant correlations between bSEM and µCT for BIC with the manufacturer's automated analysis routine (r = 0.716, p = 0.003) or a line-intercept method (r = 0.797, p = 0.010). Thus, this newer generation scanner's improved imaging capability reduced the extent of the metal-induced artefact zone enough to permit assessment of BIC. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:979-986, 2018.
Assuntos
Osso e Ossos/diagnóstico por imagem , Próteses e Implantes , Microtomografia por Raio-X/métodos , Animais , TitânioRESUMO
Peri-implant osteolysis is commonly diagnosed after substantial bone loss has occurred, making revision surgery more challenging. The goal of the current study was to identify urinary biomarkers that differentiate total hip replacement patients who eventually develop osteolysis from patients who do not. We used a repository of 24-h urine samples collected prior to surgery and annually thereafter in 26 patients, 16 who developed osteolysis, and 10 who did not. We examined the markers at radiographic diagnosis, annually for 6 years preceding diagnosis, at the first post-operative sampling point, and pre-operatively. Patients in the osteolysis and non-osteolysis groups were matched according to time post-surgery and did not differ in the male:female ratio or age at surgery. Seven candidate biomarkers were measured, including free deoxypyridinoline (DPD), cross-linked N-telopeptides (NTX), interleukin-6 (IL-6), interleukin-8 (IL-8), osteoprotegerin (OPG), α-crosslaps (α-CTX), and ß-crosslaps (ß-CTX). As an individual biomarker, DPD demonstrated the highest ability to predict osteolysis, with an area under the curve (AUC) in Receiver Operating Characteristic (ROC) analyses of 0.844 at 6 years prior to diagnosis. A panel of α-CTX and IL-6 was able to identify at-risk patients with an AUC of 0.941 or greater at all post-operative time points and an AUC of 1.000 pre-operatively. The results demonstrate the potential of using non-invasive biomarkers to identify patients at risk for peri-implant osteolysis long before the emergence of radiographic signs. Further, the high accuracy of the pre-operative biomarker levels demonstrates the potential importance of pre-existing, patient-specific factors driving subsequent osteolysis. Study Design © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2754-2761, 2018.
Assuntos
Artroplastia de Quadril/efeitos adversos , Biomarcadores/urina , Osteólise/urina , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Osteólise/diagnóstico por imagem , Osteólise/etiologia , RadiografiaRESUMO
Angiogenesis is essential for bone formation and several bone morphogenetic proteins (BMPs) have been shown to induce angiogenesis through osteoblast-derived vascular endothelial growth factor (VEGF)-A. Growth differentiation factor-5 (GDF-5) is a member of the BMP family expressed in bone and known to induce angiogenesis in vivo. In this study, the effects of GDF-5 on osteogenic differentiation and expression of VEGF-related genes were determined using rat bone marrow stromal cells. GDF-5 stimulated osteogenic differentiation. It also upregulated the expression of VEGF-A after 3 hr, accompanied by a trend of decrease in its receptor VEGFR-2 at 6 and 24 hr. VEGF-D and its receptor VEGFR-3 showed peak expression at later time points. This regulation may be further controlled by neuropilin 2 that exhibited a parallel profile to VEGF-D. These observations indicate that GDF-5 stimulates osteogenic differentiation and has a potential to induce angiogenesis through osteoblast-derived VEGF-A in bone.
Assuntos
Células da Medula Óssea/metabolismo , Proteínas Morfogenéticas Ósseas/farmacologia , Células Estromais/metabolismo , Fator A de Crescimento do Endotélio Vascular/biossíntese , Animais , Diferenciação Celular/efeitos dos fármacos , Células Cultivadas , Cicloeximida/farmacologia , Dactinomicina/farmacologia , Fator 5 de Diferenciação de Crescimento , Masculino , Osteogênese/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Regulação para Cima , Receptor 2 de Fatores de Crescimento do Endotélio Vascular/biossínteseRESUMO
Interpenetrating polymer networks (IPNs) of poly (acrylamide-co-ethylene glycol/acrylic acid) functionalized with an -Arg-Gly-Asp- (RGD) containing 15 amino acid peptides, derived from rat bone sialoprotein (bsp-RGD(15), were grafted to titanium implants in an effort to modulate bone formation in the peri-implant region in the rat femoral ablation model. Bone-implant contact (BIC) and bone formation within the medullary canal were determined using microcomputed tomography at 2 and 4 weeks postimplantation. BIC for bsp-RGD(15)-IPN implants was enhanced relative to hydroxyapatite tricalcium phosphate (HA-TCP) coated implants, but was similar to all other groups. Aggregate bone formation neither indicated a dose-dependent effect of bsp-RGD(15) nor a meaningful trend. Mechanical testing of implant fixation revealed that only the HA-TCP coated implants supported significant (>1 MPa) interfacial shear strength, despite exhibiting lower overall BIC, an indication that bone ingrowth into the rougher coating was the primary mode of implant fixation. While no evidence was found to support the hypothesis that bsp-RGD(15)-modified IPN coated implants significantly impacted bone-implant bonding, these results point to the lack of correlation between in vitro studies employing primary osteoblasts and in vivo wound healing in the peri-implant region.
Assuntos
Resinas Acrílicas , Materiais Revestidos Biocompatíveis/química , Implantes Experimentais , Osteogênese , Acrilatos , Animais , Fenômenos Biomecânicos , Etilenoglicol , Fêmur , Masculino , Modelos Animais , Oligopeptídeos , Ratos , Ratos Sprague-Dawley , Sialoglicoproteínas , TitânioRESUMO
Short-term osseointegration of orthopedic implants is critical for the long-term stability of the implant-bone interface. To improve initial implant stability, one strategy under consideration involves the presentation of adhesion ligands on the implant surface to stimulate bone regeneration in the peri-implant region. To assess the relative effects of implant surface chemistry and topography on osseointegration within the rat femoral ablation implant model, a nonfouling, enzymatically degradable interpenetrating polymer network (edIPN) of poly(AAm-co-EG/AAc) amenable to presenting the cell signaling domain Arg-Gly-Asp (RGD), was developed. Moderate enhancement of peri-implant bone formation was found after 28 days using the edIPN without peptide modification (p = 0.032). However, no data supported a benefit of peptide modification, as bone-implant contact, normalized bone volume and normalized fixation strength was equivalent or poorer than dual acid-etched (DAE) treated implants after 28 days. Surface topography was determined to be the dominant factor in modulating osseointegration, as DAE implants produced equivalent roughness-normalized fixation strength versus previously reported data on plasma-sprayed hydroxyapatite/tricalcium phosphate-coated implants (Barber et al., J Biomed Mater Res A, forthcoming). An ideal osseointegrated implant will require optimization of all three aforementioned parameters, and may take the form of biomolecule delivery from thin degradable polymer networks.
Assuntos
Implantes Experimentais , Metaloproteinase 13 da Matriz/metabolismo , Osteogênese/fisiologia , Polímeros/metabolismo , Análise de Variância , Animais , Fenômenos Biomecânicos , Masculino , Microscopia Eletrônica de Varredura , Ratos , Ratos Sprague-Dawley , Propriedades de Superfície , Fatores de TempoRESUMO
Articular cartilage lines the load-bearing surfaces of long bones and undergoes compositional and structural degeneration during osteoarthritis progression. Contrast enhanced microcomputed tomography (µCT) is being applied to a variety of preclinical models, including the mouse, to map structural and compositional properties in 3-D. The thinness (â¼30-50 µm) and high cellularity of mouse articular cartilage presents a significant imaging challenge. Our group previously showed that mouse articular cartilage and proteoglycan (PG) content can be assessed by µCT with the ioxagalate-based contrast agent Hexabrix, but the voxel size used (6 µm) was deemed to be barely adequate. The objective of the present study is to assess the utility of a novel contrast agent, CA4+, to quantify mouse articular cartilage morphology and composition with high resolution µCT imaging (3 µm voxels) and to compare the sensitivity of CA4+ and Hexabrix to detect between-group differences. While both contrast agents are iodine-based, Hexabrix is anionic and CA4+ is cationic so they interact differently with negatively charged PGs. With CA4+, a strong correlation was found between non-calcified articular cartilage thickness measurements made with histology and µCT (R2 = 0.72, p < 0.001). Cartilage degeneration-as assessed by loss in volume, thickness, and PG content-was observed in 34-week-old mice when compared to both 7- and 12-week-old mice. High measurement precision was observed with CA4+, with the coefficient of variation after repositioning and re-imaging samples equaling 2.8%, 4.5%, 7.4% and 5.9% for attenuation, thickness, volume, and PG content, respectively. Use of CA4+ allowed increased sensitivity for assessing PG content compared to Hexabrix, but had no advantage for measurement of cartilage thickness or volume. This improvement in imaging should prove useful in preclinical studies of cartilage degeneration and regeneration. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2740-2748, 2017.
Assuntos
Cartilagem Articular/diagnóstico por imagem , Meios de Contraste , Animais , Avaliação Pré-Clínica de Medicamentos , Feminino , Ácido Ioxáglico , Camundongos Endogâmicos C57BL , Tripsina , Microtomografia por Raio-XRESUMO
We demonstrate that a biomimetic polymer network is capable of affecting bone regeneration in vivo. Starting with a foundation consisting of an environmentally responsive poly(N-isopropylacrylamide-co-acrylic acid) hydrogel, we incorporated matrix metalloproteinase-13 (MMP-13) degradable crosslinkers and peptides containing integrin-binding domains (i.e., Arg-Gly-Asp) to create a biomimetic matrix designed to encourage osteoblast migration and proliferation. We independently tuned matrix stiffness and peptide concentration to generate a response surface model of osteoblast proliferation on different types of matrices. Osteoblast proliferation was significantly influenced by matrix stiffness (i.e., its complex modulus) and peptide concentration. When implanted in a rat femoral ablation model, these matrices induced bone regeneration only when protease degradable crosslinks were used to create the network. For the matrices with MMP-13 degradable crosslinkers, the bone formed had a trabecular-like structure and was distributed throughout the marrow space. Based on the correlated effects of matrix stiffness and ligand concentration, the response surface model will facilitate improvements in the regenerative capacity of these artificial extracellular matrices.
Assuntos
Materiais Biomiméticos/química , Regeneração Óssea , Matriz Extracelular/química , Fraturas do Fêmur/terapia , Regeneração Tecidual Guiada , Osteoblastos/metabolismo , Animais , Biomimética/métodos , Células Cultivadas , Regeneração Tecidual Guiada/métodos , Masculino , Teste de Materiais/métodos , Metaloproteinase 13 da Matriz/química , Modelos Animais , Oligopeptídeos/química , Osteoblastos/citologia , Ratos , Ratos Sprague-Dawley , Engenharia Tecidual/métodosRESUMO
Various anabolic agents, including transforming growth factor-beta (TGF-beta), have been shown to enhance intramembranous bone regeneration and strengthen the mechanical connection between implant and host skeleton, a prerequisite for clinical success with orthopedic and dental implants. Mechanisms underlying these observations at the level of the gene have received little attention. A rat model was used to examine levels of gene transcription for 21 "osteogenic" genes by real-time polymerase chain reaction at days 1, 3, 5, 7, 10, 14, and 28 in a control group and a group in which the implant was treated with 1 microg recombinant human TGF-beta2 (n = 42, equally divided among the 2 groups and 7 time points). Genes were chosen to represent three functional categories: (1) growth factors, their receptors and antagonists; (2) bone differentiation markers; and (3) inflammation markers. Examination of the transcription profiles showed that nine genes had up-regulated or down-regulated expression levels without a change in timing and 12 genes had accelerated or delayed expression profiles with or without a concomitant change in maximal or minimal expression. The earliest changes (days 1-3) involved accelerated expression profiles for IGF-1R and VEGF and up-regulation of TGF-beta2, TbetaRI, BMP-2, BMP-7, and Cbfa1. Furthermore, principal components analyses showed that some subsets of genes were co-expressed in both groups, although the temporal relationship of these subsets was altered following growth factor treatment. Thus, in addition to changes in individual transcription profiles, the regulatory connections between sets of co-expressed genes may also be affected by exogenously delivered anabolic agents during bone regeneration.
Assuntos
Regulação da Expressão Gênica/efeitos dos fármacos , Fator de Crescimento Transformador beta/administração & dosagem , Animais , Sequência de Bases , Primers do DNA , Perfilação da Expressão Gênica , Humanos , Masculino , Reação em Cadeia da Polimerase , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/administração & dosagem , Fator de Crescimento Transformador beta2RESUMO
Orthopedic and dental implant fixation depends upon bone regeneration. Growth factors such as transforming growth factor-beta (TGF-beta) have been shown to enhance bone repair and strengthen the mechanical connection between implant and host skeleton in canine models. To provide a platform for studying molecular mechanisms of growth factor stimulated bone regeneration and implant fixation, the present study examined peri-implant bone volume as a response to TGF-beta treatment in a rodent model. The rat femoral ablation model in which an implant is placed in the medullary cavity of the femur was used to examine the dose response to TGF-beta2 applied to the implant (0, 0.1, 1.0, or 10 microg). The study included a total of 40 rats (10 per dose) examined at 28 days. Peri-implant bone volume and bone-implant contact were assessed through microcomputed tomography and implant fixation strength was determined by a mechanical pullout test. Treatment of the implant with 10 microg TGF-beta2 led to a 2-fold increase in bone volume (P<0.001) and a 1.5-fold increase in bone-implant contact (P<0.01) with a trend of increasing fixation strength (non-significant increase of 1.4-fold). TGF-beta2 treatment with 10 microg led to uniform peri-implant bone volume and bone-implant contact along the length of the implant, whereas the other groups had less bone at the mid-point compared to the proximal and distal aspects of the implant. About 50% of the variance in implant fixation strength was explained by a regression model involving both bone-implant contact and peri-implant bone volume.
Assuntos
Regeneração Óssea/efeitos dos fármacos , Implantes Experimentais , Fator de Crescimento Transformador beta/farmacologia , Animais , Osso e Ossos/anatomia & histologia , Osso e Ossos/química , Fosfatos de Cálcio/química , Preparações de Ação Retardada/farmacocinética , Fêmur/cirurgia , Substâncias de Crescimento/farmacologia , Hidroxiapatitas/química , Masculino , Modelos Animais , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/farmacologia , Resistência ao Cisalhamento , Titânio/química , Tomografia Computadorizada por Raios X , Fator de Crescimento Transformador beta2RESUMO
The aim of the current research was to quantify the changes in gene expression in rat bone marrow derived stromal cells (BMSC) to low intensity pulsed ultrasound (LIPUS) during early time points after the ultrasound application. LIPUS at 1.5 MHz, 30 mW/cm(2) was applied to BMSC for a single 20 min treatment. Real-time PCR was carried out to quantify the expression of early response genes and bone differentiation marker genes 0.5, 1, 3, 6 and 12 h after the end of the LIPUS treatment. Compared with the controls, LIPUS treatment resulted in elevated transient expression of early response genes (c-jun, c-myc, COX-2, Egr-1, TSC-22) as well as the bone differentiation marker genes, osteonectin and osteopontin, at 3 h. This induction of early response genes as well as extracellular matrix genes associated with cell proliferation and differentiation may represent the effect of LIPUS to cells of osteoblastic lineage.
Assuntos
Expressão Gênica/genética , Osteoblastos/fisiologia , Ultrassom , Animais , Células da Medula Óssea , Células Cultivadas , Ciclo-Oxigenase 2 , Proteínas de Ligação a DNA/genética , Proteína 1 de Resposta de Crescimento Precoce , Genes jun/genética , Genes myc/genética , Proteínas Imediatamente Precoces/genética , Osteonectina/genética , Osteopontina , Prostaglandina-Endoperóxido Sintases/genética , Ratos , Ratos Sprague-Dawley , Proteínas Repressoras/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Sialoglicoproteínas/genética , Fatores de Transcrição/genéticaRESUMO
BACKGROUND: The mechanical fixation of orthopaedic and dental implants is compromised by diminished bone volume, such as with osteoporosis. Systemic administration of sclerostin antibody (Scl-Ab) has been shown to enhance implant fixation in normal animals. In the present study, we tested whether Scl-Ab can improve implant fixation in established osteoporosis in a rat model. METHODS: We used an ovariectomized (ovx) rat model, in which we found a 78% decrease in trabecular bone volume at the time of implant surgery; sham-ovx, age-matched rats were used as controls. After placement of a titanium implant in the medullary cavity of the distal aspect of the femur, the rats were maintained for four, eight, or twelve weeks and treated biweekly with Scl-Ab or with the delivery vehicle alone. Outcomes were measured with use of microcomputed tomography, mechanical testing, and static and dynamic histomorphometry. RESULTS: Scl-Ab treatment doubled implant fixation strength in both the sham-ovx and ovx groups, although the enhancement was delayed in the ovx group. Scl-Ab treatment also enhanced bone-implant contact; increased peri-implant trabecular thickness and volume; and increased cortical thickness. These structural changes were associated with an approximately five to sevenfold increase in the bone-formation rate and a >50% depression in the eroded surface following Scl-Ab treatment. Trabecular bone thickness and bone-implant contact accounted for two-thirds of the variance in fixation strength. CONCLUSIONS: In this model of severe osteoporosis, Scl-Ab treatment enhanced implant fixation by stimulating bone formation and suppressing bone resorption, leading to enhanced bone-implant contact and improved trabecular bone volume and architecture. CLINICAL RELEVANCE: Systemic administration of anti-sclerostin antibodies might be a useful strategy in total joint replacement when bone mass is deficient.