RESUMEN

The standard therapy for malignant primary bone tumors such as osteosarcoma involves major surgeries. For tumors located in difficult regions such as the pelvis, surgical intervention could lead to serious side effects for example loss of a limb and/or function, loss of bowel, bladder and sexual function as well as problems with wound healing and surgical complications. Therefore, exploring other approaches that can improve or complement current surgical techniques is important. Hence, sensitizing primary bone tumors to radiation could offer an additional strategy that could complement surgery and significantly improve survival and quality of life. Gold nanoparticles (AuNPs) have been shown to enhance radiosensitivity by increasing the local dose of radiation inside tumors. Therefore, the referred procedure of preparation and functionalization of gold nanoparticles may be used for investigation whether DNA repair inhibition in the presence of AuNPs leads to an effective radiosensitizing strategy for primary bone tumor cells and explore the mechanism of how this may be happening. In our work, we prepared gold nanoparticles and verified the relation between the size of the AuNPs and their uptake in tumor 143B cells and also investigated whether the optimal size of the AuNPs should not be smaller than the size of nuclear envelope pores (20-50 nm). Hence, two different AuNPs systems were prepared: the first one with AuNPs core size of about 5 nm (BS) and the second one with AuNPs core size of about 50 nm (ZA). For cellular AuNPs uptake enhancement, we functionalized the AuNPs with signaling peptides. For this purpose we prepared PEG-coated AuNPs functionalized with signal peptides for targeted transport into the cytoplasm (CPP) and into the cell nucleus (CPP + NLS). The toxicity of the AuNPs systems was assessed by MTS assay. We prepared stable functionalized AuNPs systems of both sizes. With the functionalizing of the AuNPs using signal peptides (CPP, NLS), the AuNPs penetrated into the cell nucleus. The referred procedure of preparation and functionalization of gold nanoparticles may be used for investigating inhibition of DNA repair in the presence of AuNPs and it could lead to new understanding in overcoming radioresistance in primary bone tumor cells.

Asunto(s)

Portadores de Fármacos , Péptidos y Proteínas de Señalización Intracelular , Nanopartículas del Metal , Osteosarcoma , Fármacos Sensibilizantes a Radiaciones/farmacología , Línea Celular Tumoral , Núcleo Celular , Oro , Humanos , Transporte de Proteínas , Calidad de Vida , Células Tumorales Cultivadas

RESUMEN

The American Orthopaedic Association initiated the Own the Bone (OTB) quality improvement program in 2009. Herein we show that the data collected through this program is similar to that collected in other large studies. Thus, the OTB registry functions as an externally valid cohort for studying fragility fracture patients. INTRODUCTION: The American Orthopedic Association initiated the Own the Bone (OTB) quality improvement program in 2009 to improve secondary prevention of fragility fractures. In this study, we present a summary of the data collected by the OTB program and compare it to data from other large fragility fracture registries with an aim to externally validate the OTB registry. METHODS: The OTB registry contained 35,038 unique cases of fragility fracture as of September, 2016. We report the demographics, presenting fracture characteristics, past fracture history, and bone mineral density (BMD) data and compare these to data from large fragility fracture studies across the world. RESULTS: Seventy-three percent of the patients in the OTB registry were female, Caucasian, and post-menopausal. In 54.4% of cases, patients had a hip fracture; spine fractures were the second most common fracture type occurring in 11.1% of patients. Thirty-four percent of the patients had a past history of fragility fracture, and the most common sites were the spine and hip. The average femoral neck T-score was - 2.06. When compared to other studies, the OTB database showed similar findings with regard to patient age, gender, race, BMI, BMD profile, prior fracture history, and family history of fragility fractures. CONCLUSION: OTB is the first and largest multi-center voluntary fragility fracture registry in the USA. The data collected through the OTB program is comparable to that collected in international studies. Thus, the OTB registry functions as an externally valid cohort for further studies assessing the clinical characteristics, interventions, and outcomes achieved in patients who present with a fragility fracture in the USA.

Asunto(s)

Fracturas Osteoporóticas/epidemiología , Mejoramiento de la Calidad , Sistema de Registros , Prevención Secundaria/normas , Distribución por Edad , Anciano , Anciano de 80 o más Años , Densidad Ósea/fisiología , Conservadores de la Densidad Ósea/uso terapéutico , Bases de Datos Factuales , Utilización de Medicamentos/estadística & datos numéricos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Osteoporosis/tratamiento farmacológico , Fracturas Osteoporóticas/fisiopatología , Fracturas Osteoporóticas/prevención & control , Distribución por Sexo , Estados Unidos/epidemiología

RESUMEN

STUDY DESIGN: Vertebral fracture load and stiffness from a metastatic vertebral defect model were predicted using nonlinear finite element models (FEM) and validated experimentally. OBJECTIVE: The study objective was to develop and validate an FEM-based tool for predicting polymer-augmented lytic vertebral fracture load and stiffness and the influence of metastatic filling materials. SUMMARY OF BACKGROUND DATA: Percutaneous vertebroplasty has the potential to reduce vertebral fracture risk affected with lytic metastases by providing mechanical stabilization. However, it has been shown that the mismatch in mechanical properties between poly(methyl-methacrylate) (PMMA) and bone induces secondary fractures and intervertebral disc degeneration. A biodegradable copolymer, poly(propylene fumarate-co-caprolactone) (P(PF-co-CL)), has been shown to possess the appropriate mechanical properties for bone defect repair. METHODS: Simulated metastatic lytic defects were created in 40 cadaveric vertebral bodies, which were randomized into 4 groups: intact vertebral body (intact), simulated defect without treatment (negative), defect treated with P(PF-co-CL) (copolymer), and defect treated with PMMA (PMMA). Spines were imaged with quantitative computed tomography (QCT), and QCT/FEM-subject-specific, nonlinear models were created. Predicted fracture loads and stiffness were identified and compared with experimentally measured values using Pearson correlation analysis and paired t test. RESULTS: There was no significant difference between the measured and predicted fracture loads and stiffness for each group. Predicted fracture loads were larger for PMMA augmentation (3960 N [1371 N]) than that for the copolymer, negative and intact groups (3484 N [1497 N], 3237 N [1744 N], and 1747 N [702 N]). A similar trend was observed in the predicted stiffness. Moreover, predicted and experimental fracture loads were strongly correlated (R=0.78), whereas stiffness showed moderate correlation (R=0.39). CONCLUSION: QCT/FEM was successful for predicting fracture loads of metastatic, polymer-augmented vertebral bodies. Overall, we have demonstrated that QCT/FEM may be a useful tool for predicting in situ vertebral fracture load resulting from vertebroplasty. LEVEL OF EVIDENCE: N/A.

Asunto(s)

Cementos para Huesos/uso terapéutico , Poliésteres/uso terapéutico , Fracturas de la Columna Vertebral/etiología , Neoplasias de la Columna Vertebral/cirugía , Columna Vertebral/diagnóstico por imagen , Vertebroplastia/efectos adversos , Vertebroplastia/métodos , Implantes Absorbibles , Anciano , Anciano de 80 o más Años , Materiales Biocompatibles/uso terapéutico , Fenómenos Biomecánicos , Cadáver , Módulo de Elasticidad , Análisis de Elementos Finitos , Predicción , Humanos , Persona de Mediana Edad , Modelos Teóricos , Dinámicas no Lineales , Polimetil Metacrilato/uso terapéutico , Factores de Riesgo , Fracturas de la Columna Vertebral/diagnóstico por imagen , Fracturas de la Columna Vertebral/prevención & control , Neoplasias de la Columna Vertebral/secundario , Columna Vertebral/cirugía , Tomografía Computarizada por Rayos X/métodos

RESUMEN

Polypropylene fumarate (PPF) scaffolds fabricated by rapid prototyping were surface modified by solution deposition of electrically conductive polypyrrole coatings with or without hydroxyapatite. Scaffolds were electrically conductive with resistivity as low as 2Ω. Scaffold characterization by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and thermo gravimetric analysis shows both polypyrrole and hydroxyapatite are present. Cell viability, attachment, proliferation, and differentiation were analyzed using human fetal osteoblast cells. These studies show that surface modification using hydroxyapatite improved cell attachment and proliferation of osteoblasts onto the PPF scaffolds. Alkaline phosphatase activity as a marker for osteogenic differentiation of cell to mature osteoblasts was analyzed. Our data reveal that osteoblasts maintained their phenotype on PPF scaffolds with and without coatings. Thus, these scaffolds could be appropriate candidates for our future in vivo studies.

Asunto(s)

Materiales Biocompatibles Revestidos/química , Ensayo de Materiales , Osteoblastos/citología , Osteogénesis , Polipropilenos/química , Andamios del Tejido/química , Fosfatasa Alcalina/biosíntesis , Antígenos de Diferenciación/biosíntesis , Diferenciación Celular , Línea Celular , Durapatita/química , Técnicas Electroquímicas , Humanos , Osteoblastos/metabolismo , Polímeros/química , Pirroles/química

RESUMEN

Oligo(polyethylene glycol) fumarate (OPF) hydrogel has been employed in musculoskeletal tissue engineering for photoencapsulation of chondrocytes and as a matrix for marrow stromal cells differentiation. In this study, we have studied the application of OPF hydrogel for coencapsulation of DNA and bone cells and examined whether coencapsulation can enhance gene transfer by maintaining the DNA within the cellular microenvironment. Our results showed that plasmid DNA encoding green fluorescence protein (GFP), coencapsulated with bone tumor cells, was capable of transfecting the cells, and the transfected tumor cells continuously expressed GFP protein over the time course of study (21 days). Furthermore, we have examined the coencapsulation of estrogen receptor (ER) encoding plasmid DNA and human fetal osteoblast cells (hFOB) that lack endogenous ER. Our results show that the transfected cells responded to estrogen as alkaline phosphatase (ALP), and estrogen response element (ERE)-directed luciferase enzyme activities increased with estrogen treatment. Taken together, these studies show that OPF hydrogel could be further explored for targeted gene delivery in bone and other tissues encapsulated within the hydrogels.

Asunto(s)

ADN/metabolismo , Estrógenos/farmacología , Técnicas de Transferencia de Gen , Hidrogel de Polietilenoglicol-Dimetacrilato/química , Osteoblastos/efectos de los fármacos , Fosfatasa Alcalina/metabolismo , Línea Celular , Supervivencia Celular/efectos de los fármacos , Proteínas Fluorescentes Verdes/metabolismo , Humanos , Luciferasas/metabolismo , Osteoblastos/citología , Osteoblastos/enzimología , Receptores de Estrógenos/metabolismo , Espectroscopía Infrarroja por Transformada de Fourier , Transfección

RESUMEN

Tibolone is a synthetic steroid which undergoes tissue selective metabolism into several metabolites having estrogenic, progestogenic or androgenic activities. The effects of 3 alpha-hydroxy tibolone (Org 4094), 3 beta-hydroxy tibolone (Org 30126) and their sulfated metabolites were investigated on human fetal osteoblasts (hFOB). Tibolone had no effect on selected osteoblast marker proteins in estrogen-receptor negative hFOB cells. In contrast, 3 alpha-hydroxy and 3beta-hydroxy tibolone resulted in dose-dependent increases in alkaline phosphatase activity in estrogen receptor (ER) alpha-positive hFOB cells. The maximum increase for both metabolites was comparable to the effects of an optimal dose of 17beta-estradiol, and occurred at 10 muM. At 20 muM, both metabolites increased mRNA levels for alkaline phosphatase and type 1 collagen and protein levels for osteocalcin. Sulfated metabolites of tibolone also increased alkaline phosphatase activity. The estrogen receptor antagonist ICI 182, 780 inhibited stimulation of alkaline phosphatase activity by sulfated and non-sulfated tibolone metabolites, but was more potent on the former. Taken together, these results suggest that stable transfection of ER alpha into hFOB cells confers regulation by 3 alpha-hydroxy and 3beta-hydroxy tibolone metabolites of osteoblast metabolism.

Asunto(s)

Receptor alfa de Estrógeno/metabolismo , Feto/citología , Regulación de la Expresión Génica/efectos de los fármacos , Norpregnenos/farmacología , Osteoblastos/efectos de los fármacos , Osteoblastos/metabolismo , Fosfatasa Alcalina/metabolismo , Animales , Médula Ósea/efectos de los fármacos , Médula Ósea/metabolismo , Matriz Ósea/metabolismo , Células Cultivadas , Receptor alfa de Estrógeno/antagonistas & inhibidores , Receptor alfa de Estrógeno/genética , Humanos , Ratas , Células del Estroma/efectos de los fármacos , Células del Estroma/metabolismo , Sulfatasas/metabolismo , Sulfatos/metabolismo , Transfección

RESUMEN

2-Methoxyestradiol (2-ME), a naturally occurring metabolite of 17beta-estradiol, is highly cytotoxic to a wide range of tumor cells but is harmless to most normal cells. However, 2-ME prevented bone loss in ovariectomized rats, suggesting it inhibits bone resorption. These studies were performed to determine the direct effects of 2-ME on cultured osteoclasts. 2-ME (2 microM) reduced osteoclast number by more than 95% and induced apoptosis in three cultured osteoclast model systems (RAW 264.7 cells cultured with RANKL, marrow cells co-cultured with stromal support cells, and spleen cells cultured without support cells in media supplemented with RANKL and macrophage colony stimulating factor (M-CSF)). The 2-ME-mediated effect was ligand specific; 2-hydroxyestradiol (2-OHE), the immediate precursor to 2-ME, exhibited less cytotoxicity; and 2-methoxyestrone (2-MEOE1) the estrone analog of 2-ME, was not cytotoxic. Co-treatment with ICI 182,780 did not antagonize 2-ME, suggesting that the cytotoxicity was not estrogen receptor-dependent. 2-ME-induced cell death in RAW 264.7 cells coincided with an increase in gene expression of cytokines implicated in inhibition of differentiation and induction of apoptosis. In addition, the 2-ME-mediated decrease in cell survival was partially inhibited by anti-lymphotoxin(LT)beta antibodies, suggesting that 2-ME-dependent effects involve LTbeta. These results suggest that 2-ME could be useful for treating skeletal diseases in which bone resorption is increased, such as postmenopausal osteoporosis and cancer metastasis to bone.

Asunto(s)

Estradiol/análogos & derivados , Osteoclastos/citología , Osteoclastos/efectos de los fármacos , 2-Metoxiestradiol , Animales , Apoptosis/efectos de los fármacos , Resorción Ósea/prevención & control , Diferenciación Celular/efectos de los fármacos , Línea Celular , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Citocinas/genética , Estradiol/farmacología , Moduladores de los Receptores de Estrógeno/farmacología , Femenino , Fulvestrant , Linfotoxina-alfa/antagonistas & inhibidores , Linfotoxina beta , Proteínas de la Membrana/antagonistas & inhibidores , Ratones , Osteoclastos/metabolismo , ARN Mensajero/genética , ARN Mensajero/metabolismo , Ratas

RESUMEN

Tissue engineering approaches to spinal cord injury (SCI) treatment are attractive because they allow for manipulation of native regeneration processes involved in restoration of the integrity and function of damaged tissue. A clinically relevant spinal cord regeneration animal model requires that the model mimics specific pathologic processes that occur in human SCI. This manuscript discusses issues related to preclinical testing of tissue engineering spinal cord regeneration strategies from a number of perspectives. This discussion includes diverse causes, pathology and functional consequences of human SCI, general and species related considerations, technical and animal care considerations, and data analysis methods.

Asunto(s)

Técnicas de Cultivo de Célula/métodos , Modelos Animales de Enfermedad , Regeneración Nerviosa/fisiología , Prótesis e Implantes , Traumatismos de la Médula Espinal/fisiopatología , Traumatismos de la Médula Espinal/cirugía , Ingeniería de Tejidos/métodos , Animales , Técnicas de Cultivo de Célula/instrumentación , Humanos , Puntaje de Gravedad del Traumatismo , Especificidad de la Especie , Ingeniería de Tejidos/instrumentación , Trasplantes , Resultado del Tratamiento

RESUMEN

Animal models are widely used to develop and evaluate tissue-engineering techniques for the reconstruction of damaged human articular cartilage. For the purpose of this review, these model systems will include in vitro culture of animal cells and explants, heterotopic models of chondrogenesis, and articular cartilage defect models. The objectives for these preclinical studies are to engineer articular cartilage for the functional restoration of a joint surface that appears anatomically, histologically, biologically, biochemically, and mechanically to resemble the original joint surface. While no animal model permits direct application to humans, each is capable of yielding principles on which decisions can be made that might eventually translate into a human application. Clearly, the use of animal models has and will continue to play a significant role in the advancement of this field. Each animal model has specific advantages and disadvantages. The key issue in the selection of an appropriate animal model is to match the model to the question being investigated and the hypothesis to be tested. The purpose of this review is to discuss issues regarding animal model selection, the benefits and limitations of these model systems, scaffold selection with emphasis on polymers, and evaluation of the tissue-engineered articular cartilage.

Asunto(s)

Enfermedades de los Cartílagos/cirugía , Cartílago Articular/crecimiento & desarrollo , Técnicas de Cultivo de Célula/métodos , Condrogénesis , Modelos Animales de Enfermedad , Procedimientos de Cirugía Plástica/métodos , Ingeniería de Tejidos/métodos , Animales , Enfermedades de los Cartílagos/clasificación , Enfermedades de los Cartílagos/patología , Enfermedades de los Cartílagos/fisiopatología , Cartílago Articular/lesiones , Cartílago Articular/patología , Cartílago Articular/cirugía , Técnicas de Cultivo de Célula/instrumentación , Humanos , Polímeros , Prótesis e Implantes , Procedimientos de Cirugía Plástica/instrumentación , Ingeniería de Tejidos/instrumentación , Resultado del Tratamiento

RESUMEN

Retinal pigment epithelium (RPE) plays a key role in the maintenance of the normal functions of the retina, especially photoreceptors. Alteration in RPE structure and function is implicated in a variety of ocular disorders. Tissue engineering strategies using synthetic biodegradable polymers as temporary substrates for RPE cell culture and subsequent transplantation may provide a promising new therapy. In this review article, the manufacture of thin biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) films and their degradation behavior in vitro are discussed. RPE cell proliferation and differentiation on these PLGA films are reviewed. The fabrication of model substrates with desired chemical micropatterns in the micrometer scale is discussed and the effects of surface patterning on RPE morphology and function are assessed. Finally. the preparation of biodegradable micropatterns with adhesive PLGA and non-adhesive poly(ethylene glycol)/PLA domains to modulate RPE cell adhesion is presented.

Asunto(s)

Materiales Biocompatibles , Epitelio Pigmentado Ocular/citología , Epitelio Pigmentado Ocular/trasplante , Ingeniería de Tejidos/métodos , Animales , Adhesión Celular , Técnicas de Cultivo de Célula/métodos , División Celular , Humanos , Ácido Láctico , Ensayo de Materiales , Ácido Poliglicólico , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Polímeros , Enfermedades de la Retina/cirugía , Propiedades de Superficie

RESUMEN

Cartilage defects are common, painful conditions and none of the currently available treatment options are satisfactory. Tissue engineering techniques involving scaffolds made from biodegradable synthetic polymers hold great promise for the future. These materials can be manufactured in an injectable form for minimally invasive procedures or in a preformed state to treat large irreparable lesions including arthritis. The mechanical and biologic properties of synthetic polymers can be tailored to different clinical applications and engineering strategies. The scaffold serves as a mechanical substrate for cells and bioactive factors and can help direct and organize the process of regeneration. The ultimate goal of tissue engineering is to recapitulate normal organogenesis to create histologically and functionally normal tissue. A review of the characteristics and potential of synthetic polymers shows that these substances will play a major role in treating cartilage disorders.

Asunto(s)

Implantes Absorbibles , Cartílago , Polímeros , Ingeniería de Tejidos/métodos , Células Cultivadas , Predicción , Humanos , Ingeniería de Tejidos/tendencias

RESUMEN

OBJECTIVE: To determine the structural stiffness and reducibility of various external fixators placed in malalignment and malrotation. DESIGN: Uniform testing of all external fixator configurations. SETTING: Orthopaedic biomechanical laboratory. METHODS: Thirteen external fixators from different manufacturers, in a total of fifteen configurations, were studied. All external fixators were applied to a malreduction jig initially, and a subsequent anatomic reduction was then attempted. If an anatomic reduction was possible, the structural stiffness of those fixators was determined. If anatomic reduction was not possible, the external fixator was removed and reapplied to an anatomically reduced model, and then structural stiffness was determined. RESULTS: Six of the thirteen external fixator configurations allowed an anatomic reduction after placement on a malreduction model. The other nine external fixator configurations would not allow for an anatomic reduction. All the external fixator configurations were biomechanically tested in anteroposterior bending, lateral bending, axial load, and torsion. Each fixator had its own structural stiffness and is reported. CONCLUSIONS: Some external fixators will not allow for an anatomic reduction once placed in malalignment and malrotation without repositioning of the fixator pins. External fixator configurations (i.e., single-pin, dual-pin, and multipin barclamps) affect structural stiffness. Structural stiffness widely varied among the external fixators. Proper external fixator selection will enable early fracture immobilization in malalignment and malrotation in suboptimal conditions (e.g., wartime conditions or a civilian disaster), with subsequent external fixator adjustment for an anatomic reduction.

Asunto(s)

Tratamiento de Urgencia/instrumentación , Fijadores Externos , Fracturas de la Tibia/terapia , Fenómenos Biomecánicos , Tratamiento de Urgencia/métodos , Diseño de Equipo , Fijadores Externos/clasificación , Ensayo de Materiales , Errores Médicos , Factores de Tiempo

RESUMEN

BACKGROUND: Controlled release of transforming growth factor-beta1 (TGF-beta1) to a bone defect may be beneficial for the induction of a bone regeneration cascade. The objectives of this work were to assess the feasibility of using biodegradable polymer microparticles as carriers for controlled TGF-beta1 delivery and the effects of released TGF-beta1 on the proliferation and differentiation of marrow stromal cells in vitro. METHODS: Recombinant human TGF-beta1 was incorporated into microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG). Fluorescein isothiocynate-labeled bovine serum albumin (FITC-BSA) was co-encapsulated as a porogen. The effects of PEG content (0, 1, or 5% by weight [wt%]) and buffer pH (3, 5, or 7.4) on the protein release kinetics and the degradation of PLGA were determined in vitro for as long as 28 days. Rat marrow stromal cells were seeded on a biodegradable poly(propylene fumarate) (PPF) substrate. The dose response and biological activity of released TGF-beta1 was determined after 3 days in culture. The effects of TGF-beta1 released from PLGA/PEG microparticles on marrow stromal cell proliferation and osteoblastic differentiation were assessed during a 21-day period. RESULTS: TGF-beta1 was encapsulated along with FITC-BSA into PLGA/PEG blend microparticles and released in a multiphasic fashion including an initial burst for as long as 28 days in vitro. Increasing the initial PEG content resulted in a decreased cumulative mass of released proteins. Aggregation of FITC-BSA occurred at lower buffer pH, which led to decreased release rates of both proteins. The degradation of PLGA was increased at higher PEG content and significantly accelerated at acidic pH conditions. Rat marrow stromal cells cultured on PPF substrates showed a dose response to TGF-beta1 released from the microparticles similar to that of added TGF-beta1, indicating that the activity of TGF-beta1 was retained during microparticle fabrication and after growth factor release. At an optimal TGF-beta1 dosage of 1.0 ng/ml after 3 days, the released TGF-beta1 enhanced the proliferation and osteoblastic differentiation of marrow stromal cells over 21 days of culture, with increased total cell number, alkaline phosphatase activity, and osteocalcin production. CONCLUSIONS: PLGA/PEG blend microparticles can serve as delivery vehicles for controlled release of TGF-beta1, and the released growth factor enhances marrow stromal cell proliferation and osteoblastic differentiation in vitro. CLINICAL RELEVANCE: Controlled release of TGF-beta1 from PLGA/PEG microparticles is representative of emerging tissue engineering technologies that may modulate cellular responses to encourage bone regeneration at a skeletal defect site.

Asunto(s)

Células de la Médula Ósea/fisiología , Portadores de Fármacos , Osteoblastos/fisiología , Polietilenglicoles , Poliglactina 910 , Factor de Crecimiento Transformador beta/farmacocinética , Animales , Materiales Biocompatibles , Biodegradación Ambiental , Células de la Médula Ósea/efectos de los fármacos , Diferenciación Celular/efectos de los fármacos , División Celular/efectos de los fármacos , Células Cultivadas , Fluoresceína-5-Isotiocianato/análogos & derivados , Masculino , Microscopía Electrónica de Rastreo , Microesferas , Osteoblastos/efectos de los fármacos , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes/administración & dosificación , Proteínas Recombinantes/farmacocinética , Proteínas Recombinantes/farmacología , Albúmina Sérica Bovina , Células del Estroma/citología , Células del Estroma/efectos de los fármacos , Células del Estroma/fisiología , Factor de Crecimiento Transformador beta/administración & dosificación , Factor de Crecimiento Transformador beta/farmacología , Factor de Crecimiento Transformador beta1

RESUMEN

STUDY DESIGN: A case report of cervical myelopathy caused by ossification of the posterior longitudinal ligament in a patient with vitamin D-resistant rickets is presented together with a review of literature. OBJECTIVE: To report the diagnosis of ossification of the posterior longitudinal ligament in a white woman with vitamin D-resistant rickets. SUMMARY OF BACKGROUND DATA: The association between ossification of the posterior longitudinal ligament and untreated vitamin D-resistant rickets has been reported in Japan, but infrequently in white populations. In whites, ossification of the posterior longitudinal ligament is closely associated with diffuse idiopathic skeletal hyperostosis. A clear association between ossification of the posterior longitudinal ligament and vitamin D-resistant rickets in white populations has not yet been established. METHODS: The medical record and imaging studies of a patient treated at the authors' institution for cervical myelopathy caused by ossification of the posterior longitudinal ligament in the setting of treated vitamin D-resistant rickets were reviewed. A Medline search of the medical literature between 1966-1999 was performed to identify pertinent studies and similar case reports. RESULTS: The occurrence of spinal stenosis in untreated adults with vitamin D-resistant rickets has been reported in all regions of the spine in Japanese patients. The association between ossification of the posterior longitudinal ligament and untreated vitamin D-resistant rickets was first reported in Japan, where ossification of the posterior longitudinal ligament is endemic. This association may be incidental, because reports on ossification of the posterior longitudinal ligament in whites are not as frequent as in Japanese, reflecting the higher prevalence of this condition in Japan. CONCLUSION: Ossification of the posterior longitudinal ligament and ossification of the posterior longitudinal ligament associated with deranged calcium or phosphate metabolism may be different pathologic entities sharing a common outcome. Adequate treatment of vitamin D-resistant rickets may not always prevent or reverse ossification of the posterior longitudinal ligament.

Asunto(s)

Hipofosfatemia Familiar/complicaciones , Osificación del Ligamento Longitudinal Posterior/diagnóstico , Densidad Ósea , Calcio/sangre , Vértebras Cervicales/diagnóstico por imagen , Vértebras Cervicales/patología , Vértebras Cervicales/cirugía , Diagnóstico Diferencial , Femenino , Humanos , Hipofosfatemia Familiar/tratamiento farmacológico , Hipofosfatemia Familiar/metabolismo , Laminectomía , Imagen por Resonancia Magnética , Persona de Mediana Edad , Osificación del Ligamento Longitudinal Posterior/complicaciones , Osificación del Ligamento Longitudinal Posterior/metabolismo , Osificación del Ligamento Longitudinal Posterior/cirugía , Fosfatos/sangre , Compresión de la Médula Espinal/diagnóstico , Compresión de la Médula Espinal/etiología , Compresión de la Médula Espinal/cirugía , Tomografía Computarizada por Rayos X , Vitamina D/uso terapéutico

RESUMEN

New injectable, in situ crosslinkable biodegradable polymer composites were investigated consisting of poly(propylene fumarate) (PPF), poly(ethylene glycol)-dimethacrylate (PEG-DMA), and beta-tricalcium phosphate (beta-TCP). We examined the effects of the PEG-DMA/PPF double-bond ratio and beta-TCP content on the crosslinking characteristics of the composites including the maximum crosslinking temperature and the gel point, as well as the properties of the crosslinked composites such as the compressive strength and modulus, and the water-holding capacity. The maximum crosslinking temperature was constant averaging 39.7 degrees C for the composite formulations tested. The gel points varied from 8.0 +/- 1.0 to 12.6 +/- 2.5 min and were not affected by the relative amounts of PEG-DMA. The compressive strength at yield of PEG-DMA/PPF composites without beta-TCP increased from 5.9 +/- 1.0 to 11.2 +/- 2.2 MPa as the double-bond ratio of PEG-DMA/PPF increased from 0.38 to 1.88. An increase in compressive modulus was also observed from 30.2 +/- 3.5 to 58.4 +/- 6.2 MPa for the same range of the PEG-DMA/PPF double-bond ratio. Also, the addition of beta-TCP (33 wt%) enhanced the mechanical properties of all composites. The equilibrium water content of networks without beta-TCP increased from 21.7 +/- 0.2 to 30.6 +/- 0.2% for a double-bond ratio of PEG-DMA/PPF ranging from 0.38 to 1.88. However, the mechanical properties of the swollen composites under compression were smaller than the dry ones. These data demonstrate the feasibility of fabricating injectable biodegradable polymer composites with engineered mechanical properties for orthopedic tissue engineering.

Asunto(s)

Acrilatos/química , Materiales Biocompatibles , Resinas Compuestas , Fumaratos/química , Polietilenglicoles/química , Polipropilenos/química , Biodegradación Ambiental , Metacrilatos , Temperatura

RESUMEN

Poly (Propylene Fumarate) (PPF), a novel, bulk erosion, biodegradable polymer, has been shown to have osteoconductive effects in vivo when used as a bone regeneration scaffold (Peter, S. J., Suggs, L. J., Yaszemski, M. J., Engel, P. S., and Mikos, A. J., 1999, J. Biomater. Sci. Polym. Ed., 10, pp. 363-373). The material properties of the polymer allow it to be injected into irregularly shaped voids in vivo and provide mechanical stability as well as function as a bone regeneration scaffold. We fabricated a series of biomaterial composites, comprised of varying quantities of PPF, NaCl and beta-tricalcium phosphate (beta-TCP), into the shape of right circular cylinders and tested the mechanical properties in four-point bending and compression. The mean modulus of elasticity in compression (Ec) was 1204.2 MPa (SD 32.2) and the mean modulus of elasticity in bending (Eb) was 1274.7 MPa (SD 125.7). All of the moduli were on the order of magnitude of trabecular bone. Changing the level of NaCl from 20 to 40 percent, by mass, did not decrease Ec and Eb significantly, but did decrease bending and compressive strength significantly. Increasing the beta-TCP from 0.25 g/g PPF to 0.5 g/g PPF increased all of the measured mechanical properties of PPF/NVP composites. These results indicate that this biodegradable polymer composite is an attractive candidate for use as a replacement scaffold for trabecular bone.

Asunto(s)

Implantes Absorbibles/normas , Regeneración Ósea/fisiología , Fosfatos de Calcio/química , Técnicas de Cultivo/métodos , Fumaratos/química , Polipropilenos/química , Fenómenos Biomecánicos , Fuerza Compresiva , Elasticidad , Humanos , Ensayo de Materiales , Porosidad , Análisis de Regresión

RESUMEN

Human recombinant bone morphogenetic protein-2 (rhBMP-2) has been proven effective in stimulating the regeneration of bone in both skeletal and extraskeletal locations. Through encapsulation within, and release from, biodegradable poly(DL-lactic-co-glycolic acid) (PLGA) microspheres, a proven vehicle for sustained delivery of various proteins, the local concentrations of rhBMP-2 could be maintained at optimal levels to stimulate bone regeneration and remodeling at the site of healing in diverse clinical settings. Thus the purpose of this work was to investigate the encapsulation of rhBMP-2 in PLGA microspheres and its biologic activity upon release. Using in vitro tests in simulated body fluids, the effect of rhBMP-2 released from PLGA microspheres upon osteoblast cell cultures was found to be statistically similar to the effect produced by positive controls consisting of nonencapsulated aqueous rhBMP-2 in simulated body fluids. This clarifies an important step in skeletal tissue engineering strategies aimed at the use of encapsulated rhBMP-2 to stimulate bone regeneration and remodeling.

Asunto(s)

Materiales Biocompatibles/uso terapéutico , Proteínas Morfogenéticas Óseas/uso terapéutico , Regeneración Ósea/efectos de los fármacos , Remodelación Ósea/efectos de los fármacos , Ácido Láctico/uso terapéutico , Microesferas , Osteoblastos/citología , Osteoblastos/efectos de los fármacos , Ácido Poliglicólico/uso terapéutico , Polímeros/uso terapéutico , Proteínas Recombinantes/uso terapéutico , Factor de Crecimiento Transformador beta , Proteína Morfogenética Ósea 2 , Células Cultivadas/efectos de los fármacos , Portadores de Fármacos , Evaluación Preclínica de Medicamentos , Feto/citología , Humanos , Copolímero de Ácido Poliláctico-Ácido Poliglicólico

RESUMEN

Recombinant human transforming growth factor beta1 (TGF-beta1) was incorporated into microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) to create a delivery vehicle for the growth factor. The entrapment efficiency of TGF-beta1 in the microparticles containing 5% PEG was 40.3 +/- 1.2% for a TGF-beta1 loading density of 6.0 ng/1 mg of microparticles. For the same loading, 17.9 +/- 0.6 and 32.1 +/- 2.5% of the loaded TGF-beta1 was released after 1 and 8 days, respectively, followed by a plateau for the remaining 3 weeks. Rat marrow stromal cells showed a dose response to TGF-beta1 released from the microparticles similar to that of added TGF-beta1, indicating the activity of TGF-beta1 was retained during microparticle fabrication and after TGF-beta1 release. An optimal TGF-beta1 dosage of 1.0 ng/mL was determined through a 3-day dose response study for maximal alkaline phosphatase (ALP) activity. The TGF-beta1 released from the microparticles loaded with 6.0 ng TGF-beta1/1 mg of microparticles for the optimal dosage of TGF-beta1 enhanced the proliferation and osteoblastic differentiation of marrow stromal cells cultured on poly(propylene fumarate) substrates. The cells showed significantly increased total cell number, ALP activity, and osteocalcin production with values reaching 138,700 +/- 3300 cells/cm(2), 22.8 +/- 1.5 x 10(-7) micromol/min/cell, and 15.9 +/- 1.5 x 10(-6) ng/cell, respectively, after 21 days as compared to cells cultured under control conditions without TGF-beta1. These results suggest that controlled release of TGF-beta1 from the PLGA/PEG blend microparticles may find applications in modulating cellular response during bone healing at a skeletal defect site.

Asunto(s)

Cápsulas , Ácido Láctico , Osteoblastos/efectos de los fármacos , Polietilenglicoles , Ácido Poliglicólico , Polímeros , Factor de Crecimiento Transformador beta/farmacología , Animales , Materiales Biocompatibles , Células Cultivadas , Sistemas de Liberación de Medicamentos , Implantes de Medicamentos , Fumaratos , Humanos , Copolímero de Ácido Poliláctico-Ácido Poliglicólico , Polipropilenos , Ratas

RESUMEN

We investigated the crosslinking characteristics of an injectable composite paste of poly(propylene fumarate) (PPF), N-vinyl pyrrolidinone (N-VP), benzoyl peroxide (BP), sodium chloride (NaCl), and beta-tricalcium phosphate (beta-TCP). We examined the effects of PPF molecular weight, N-VP/PPF ratio, BP/PPF ratio, and NaCl weight percent on the crosslinking temperature, heat release upon crosslinking, gel point, and the composite compressive strength and modulus. The maximum crosslinking temperature did not vary widely among formulations, with the absolute values falling between 38 degrees and 48 degrees C, which was much lower than that of 94 degrees C for poly(methyl methacrylate) bone cement controls tested under the same conditions. The total heat released upon crosslinking was decreased by an increase in PPF molecular weight and a decrease in N-VP/PPF ratio. The gel point was affected strongly by the PPF molecular weight, with a decrease in PPF molecular weight more rapidly leading to a gel point. An increase in initiator concentration had the same effect to a lesser degree. The time frame for curing was varied from 1-121 min, allowing the composite to be tailored to specific applications. The compressive strength and compressive modulus values increased with decreasing N-VP/PPF, increasing NaCl content, and increasing BP/PPF ratio. For all formulations, the compressive strength values fell between 1 and 12 MPa, and the compressive modulus values fell between 23 and 265 MPa. These data suggest that injectable PPF/beta-TCP pastes can be prepared with handling characteristics appropriate for clinical orthopedic applications and that the mechanical properties of the cured composites are suitable for trabecular bone replacement.

Asunto(s)

Cementos para Huesos/química , Fosfatos de Calcio/química , Fumaratos/química , Polipropilenos/química , Biodegradación Ambiental , Rastreo Diferencial de Calorimetría , Fenómenos Químicos , Química Física , Fuerza Compresiva , Reactivos de Enlaces Cruzados , Geles , Ensayo de Materiales , Peso Molecular , Pomadas , Temperatura

RESUMEN

To synthesize high molecular weight poly(propylene fumarate) (PPF), fumaryl chloride and propylene glycol were reacted in the presence of potassium carbonate, which serves as a proton scavenger. Transesterification of the resulting low molecular weight oligomer led to a polymer with greater molecular weight than those from previous reaction methods without requiring the use of a catalyst. According to two-dimensional NMR, the backbone structure of this polymer was as expected and contained no byproducts formed by acid catalyzed addition across the fumarate double bond. Kinetic studies of the transesterification showed that the molecular weight reached a final Mn of 4900 (+/-700) and Mw of 9100 (+/-1300) after 16 h, while the polydispersity index remained below 1.8 throughout the reaction. Thus the PPF synthesized by the new method is of higher molecular weight and greater purity than our previously prepared material.

Asunto(s)

Cementos para Huesos/química , Fumaratos/química , Polipropilenos/química , Acilación , Cementos para Huesos/síntesis química , Cromatografía en Gel , Depuradores de Radicales Libres/química , Fumaratos/síntesis química , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Polipropilenos/síntesis química , Propilenglicol/química , Protones , Espectroscopía Infrarroja por Transformada de Fourier