Mecanismo de acción de hormonas tiroideas sobre el páncreas endócrino

El rol de las hormonas tiroideas en la Diabetes Mellitus y la función endocrina del páncreas fue estudiado por primera vez en 1944 por B. A. Houssay (1 ). Trabajando con perros parcialmente panceatectomizados, sometidos a tratamiento con hormonas tiroideas, observó que adquirían una forma de diabetes irreversible, que persistía aún después de interrumpir el tratamiento tiroideo. Llamó a ésta Diabetes Meta.tiroidea ; su mecanismo parecía ser un agotamiento pancreático consecutivo a una sobreestimulación (2). Sus estudios se extendieron en animales sometidos a tiroidectomía y pancreatectomía subtotal simultánea, observando que no se reducía la severidad de la diabetes, sino que la operación exacerbaba los síntomas, la enfermedad progresaba más rápidamente y finalmente morían en hiperglucemia. A partir de estos experimentos, las hormonas tiroideas han sido consideradas como hormonas diabetogénicas. Numerosos investigadores han observado la intolerancia a la glucosa asociada con una disfunción tiroidea, tanto a nivel clínico como experimental (3-11). Pero el mecanismo por el cual las hormonas tiroideas llevan a cabo estos cambios es hasta hoy desconocido

Biocompatibility and biodegradation of polyester and polyfumarate based-scaffolds for bone tissue engineering

Biodegradable and biocompatible polymeric scaffolds have been recently introduced for tissue regeneration purpose. In the present study we aimed to develop polymeric-based scaffolds for bone regeneration. Two polyesters, poly-β-propiolactone (PBPL), poly-ε-caprolactone (PCPL) and two polyfumarates, polydiisopropyl fumarate (PDIPF), polydicyclohexyl fumarate (PDCF) were chosen to prepare films which can support osteoblastic growth. Scanning electron microscopy and water contact angle were used to characterize the matrices. Biodegradation studies were performed both in PBS buffer and using an in vitro macrophage degradation assay. Mouse calvaria-derived MC3T3E1 cells and UMR106 rat osteosarcoma cell lines were used to perform biocompatibility and cytotoxicity studies. The polyesters, the most hydrophilic polymers studied, showed a rougher and more porous surfaces than the polyfumarates. Under acellular conditions, only PBPL was degraded by hydrolytic mechanisms. However, macrophages performed an active degradation of all polymeric films. Osteoblasts developed well-defined actin fibres without evidence of cytotoxicity when growing on the films. The number of UMR106 osteoblasts that adhered to the PBPL-based film was higher than that of the cells attached to the PECL and polyfumarates (PDIPF and PDCF) matrices. Both UMR106 and MC3T3E1 osteoblastic lines showed protein levels comparable to control conditions, demonstrating that they grew well on all surfaces. However, UMR106 cells showed a significant increase in proliferation on polyester-derived scaffolds (PBPL and PECL). The alkaline phosphatase activity of UMR106, an osteoblastic marker, was significantly higher than that of control plastic dishes. MC3T3E1 cells expressed similar levels of this differentiation marker in all polymeric matrices. We found similar collagen protein content after 48 h culture of UMR106 cells on all surfaces. However, important differences were evident in the MC3T3E1 line. In conclusion, the synthetic polymeric-based scaffold we have developed and studied supports adhesion, growth and differentiation of two osteoblastic cell lines, suggesting that they could be useful in bone tissue regeneration. Copyright 2008 John Wiley & Sons, Ltd

Biocompatibility and biodegradation of polyester and polyfumarate based-scaffolds for bone tissue engineering

Biodegradable and biocompatible polymeric scaffolds have been recently introduced for tissue regeneration purpose. In the present study we aimed to develop polymeric-based scaffolds for bone regeneration. Two polyesters, poly-β-propiolactone (PBPL), poly-ε-caprolactone (PCPL) and two polyfumarates, polydiisopropyl fumarate (PDIPF), polydicyclohexyl fumarate (PDCF) were chosen to prepare films which can support osteoblastic growth. Scanning electron microscopy and water contact angle were used to characterize the matrices. Biodegradation studies were performed both in PBS buffer and using an in vitro macrophage degradation assay. Mouse calvaria-derived MC3T3E1 cells and UMR106 rat osteosarcoma cell lines were used to perform biocompatibility and cytotoxicity studies. The polyesters, the most hydrophilic polymers studied, showed a rougher and more porous surfaces than the polyfumarates. Under acellular conditions, only PBPL was degraded by hydrolytic mechanisms. However, macrophages performed an active degradation of all polymeric films. Osteoblasts developed well-defined actin fibres without evidence of cytotoxicity when growing on the films. The number of UMR106 osteoblasts that adhered to the PBPL-based film was higher than that of the cells attached to the PECL and polyfumarates (PDIPF and PDCF) matrices. Both UMR106 and MC3T3E1 osteoblastic lines showed protein levels comparable to control conditions, demonstrating that they grew well on all surfaces. However, UMR106 cells showed a significant increase in proliferation on polyester-derived scaffolds (PBPL and PECL). The alkaline phosphatase activity of UMR106, an osteoblastic marker, was significantly higher than that of control plastic dishes. MC3T3E1 cells expressed similar levels of this differentiation marker in all polymeric matrices. We found similar collagen protein content after 48 h culture of UMR106 cells on all surfaces. However, important differences were evident in the MC3T3E1 line. In conclusion, the synthetic polymeric-based scaffold we have developed and studied supports adhesion, growth and differentiation of two osteoblastic cell lines, suggesting that they could be useful in bone tissue regeneration.Facultad de Ciencias Exacta

Biocompatibility and biodegradation of polyester and polyfumarate based-scaffolds for bone tissue engineering

Biodegradable and biocompatible polymeric scaffolds have been recently introduced for tissue regeneration purpose. In the present study we aimed to develop polymeric-based scaffolds for bone regeneration. Two polyesters, poly-β-propiolactone (PBPL), poly-ε-caprolactone (PCPL) and two polyfumarates, polydiisopropyl fumarate (PDIPF), polydicyclohexyl fumarate (PDCF) were chosen to prepare films which can support osteoblastic growth. Scanning electron microscopy and water contact angle were used to characterize the matrices. Biodegradation studies were performed both in PBS buffer and using an in vitro macrophage degradation assay. Mouse calvaria-derived MC3T3E1 cells and UMR106 rat osteosarcoma cell lines were used to perform biocompatibility and cytotoxicity studies. The polyesters, the most hydrophilic polymers studied, showed a rougher and more porous surfaces than the polyfumarates. Under acellular conditions, only PBPL was degraded by hydrolytic mechanisms. However, macrophages performed an active degradation of all polymeric films. Osteoblasts developed well-defined actin fibres without evidence of cytotoxicity when growing on the films. The number of UMR106 osteoblasts that adhered to the PBPL-based film was higher than that of the cells attached to the PECL and polyfumarates (PDIPF and PDCF) matrices. Both UMR106 and MC3T3E1 osteoblastic lines showed protein levels comparable to control conditions, demonstrating that they grew well on all surfaces. However, UMR106 cells showed a significant increase in proliferation on polyester-derived scaffolds (PBPL and PECL). The alkaline phosphatase activity of UMR106, an osteoblastic marker, was significantly higher than that of control plastic dishes. MC3T3E1 cells expressed similar levels of this differentiation marker in all polymeric matrices. We found similar collagen protein content after 48 h culture of UMR106 cells on all surfaces. However, important differences were evident in the MC3T3E1 line. In conclusion, the synthetic polymeric-based scaffold we have developed and studied supports adhesion, growth and differentiation of two osteoblastic cell lines, suggesting that they could be useful in bone tissue regeneration.Facultad de Ciencias Exacta

Interaction studies of mixed matrices of Chitosanpoly- ε -Caprolactone and Alendronate for bone tissue engineering

Tissue engineering actual tendencies leads to the development of biocompatible matrices with accurate physical and mechanical properties in bone reconstruction. As a regeneration of a new tissue is achieved, the scaffold is no longer needed and so it is reasonable to use biodegradable scaffolds [1]. The rate of degradation must be in parallel with the tissue regeneration, and is very important to provide long term construct biocompatibility, because only natural tissue will remain in the body–a neo-organ. In this context one of the most common compound used is the natural polymer chitosan, whose mechanical properties can be improved by adding synthetic polymers [2]. The great interest in this macromolecule is due to its proved biocompatibility and biodegradation properties [3]. Matrix also requires the capacity to transport osteogenic agents which enhance bone regeneration. Bisphosphonates are a new class of synthetic compounds structurally related to pyrophosphate, an endogenous modulator in homeostasis of calcium, and they are clinically used for various metabolic bone disorders such as Paget’s disease, hypercalcemia of malignancy, bone metastasis and osteoporosis [4]. The reduced targetability of some bisphosphonates in relationship to the dose increased and its hepatosplenic accumulation has been reported [5]. It is due to high precipitability with divalent ions in the circulation in blood plasma, which may be taken up by reticuloendothelial system as foreign substances [6]. Therefore, new drug delivery systems are needed to overcome these problems. The aim of our work is the development of a scaffold for tissue engineering based in chitosan/poly-ε-caprolactone blend which contains an adequate concentration of alendronate (a nitrogen bisphosphonate) for osteoblastic bone growth without toxic effects

Interaction studies of mixed matrices of chitosanpoly-ε-caprolactone and alendronate for bone tissue engineering

Tissue engineering actual tendencies leads to the development of biocompatible matrices with accurate physical and mechanical properties in bone reconstruction. As a regeneration of a new tissue is achieved, the scaffold is no longer needed and so it is reasonable to use biodegradable scaffolds. The rate of degradation must be in parallel with the tissue regeneration, and is very important to provide long term construct biocompatibility, because only natural tissue will remain in the body–a neo-organ. In this context one of the most common compound used is the natural polymer chitosan, whose mechanical properties can be improved by adding synthetic polymers. The great interest in this macromolecule is due to its proved biocompatibility and biodegradation properties. Matrix also requires the capacity to transport osteogenic agents which enhance bone regeneration. Bisphosphonates are a new class of synthetic compounds structurally related to pyrophosphate, an endogenous modulator in homeostasis of calcium, and they are clinically used for various metabolic bone disorders such as Paget’s disease, hypercalcemia of malignancy, bone metastasis and osteoporosis. The reduced targetability of some bisphosphonates in relationship to the dose increased and its hepatosplenic accumulation has been reported. It is due to high precipitability with divalent ions in the circulation in blood plasma, which may be taken up by reticuloendothelial system as foreign substances. Therefore, new drug delivery systems are needed to overcome these problems. The aim of our work is the development of a scaffold for tissue engineering based in chitosan/poly-ε-caprolactone blend which contains an adequate concentration of alendronate (a nitrogen bisphosphonate) for osteoblastic bone growth without toxic effects.Facultad de Ciencias Exacta

Interaction studies of mixed matrices of chitosanpoly-ε-caprolactone and alendronate for bone tissue engineering

Tissue engineering actual tendencies leads to the development of biocompatible matrices with accurate physical and mechanical properties in bone reconstruction. As a regeneration of a new tissue is achieved, the scaffold is no longer needed and so it is reasonable to use biodegradable scaffolds. The rate of degradation must be in parallel with the tissue regeneration, and is very important to provide long term construct biocompatibility, because only natural tissue will remain in the body–a neo-organ. In this context one of the most common compound used is the natural polymer chitosan, whose mechanical properties can be improved by adding synthetic polymers. The great interest in this macromolecule is due to its proved biocompatibility and biodegradation properties. Matrix also requires the capacity to transport osteogenic agents which enhance bone regeneration. Bisphosphonates are a new class of synthetic compounds structurally related to pyrophosphate, an endogenous modulator in homeostasis of calcium, and they are clinically used for various metabolic bone disorders such as Paget’s disease, hypercalcemia of malignancy, bone metastasis and osteoporosis. The reduced targetability of some bisphosphonates in relationship to the dose increased and its hepatosplenic accumulation has been reported. It is due to high precipitability with divalent ions in the circulation in blood plasma, which may be taken up by reticuloendothelial system as foreign substances. Therefore, new drug delivery systems are needed to overcome these problems. The aim of our work is the development of a scaffold for tissue engineering based in chitosan/poly-ε-caprolactone blend which contains an adequate concentration of alendronate (a nitrogen bisphosphonate) for osteoblastic bone growth without toxic effects.Facultad de Ciencias Exacta

Propiedades biológicas de matrices porosas y no porosas de PCL/PFIP

Actualmente existe un alto interés en el estudio de polímeros sintéticos biodegradables para su aplicación como andamiajes biocompatibles en distintas áreas de ingeniería de tejidos. Poli(e-caprolactona) (PCL) y poli(diisopropilfumarato) (PDIPF) han demostrado ser buenos sustratos para la adhesión, el crecimiento y la diferenciación de dos líneas de células osteoblásticas, MC3T3E1 derivadas de células de calvaria ratón y UMR106 osteosarcoma de rata, sugiriendo que estos polímeros pueden ser útiles en la regeneración de tejido óseo. Para obtener un material con buenas propiedades mecánicas y una tasa de degradación intermedia entre ambos homopolímeros se ha preparado una mezcla de PCL y PDIPF compatibilizada por ultrasonido de alta intensidad. Esta mezcla ha demostrado poseer mejores propiedades mecánicas y mayor biocompatibilidad que los homopolímeros correspondientes. El objetivo de este trabajo es evaluar la actividad de células UMR106 frente a matrices porosas y no porosas de la mezcla de PCL-PFIP compatibilizadas. Las matrices porosas se obtuvieron mediante electrospraying de una solución de la mezcla en cloroformo. Las matrices no porosas se obtuvieron por casting de una solución en cloroformo. Las películas obtenidas se evaluaron por SEM y microscopia óptica, usando el software “Image J” para caracterizarlas morfológicamente. En ambas matrices se realizaron ensayos de adhesión (a 1h), proliferación (a 24 h) y actividad de Fosfatasa Alcalina (ALP) (a 24 y 48 h, control: superficie de placa de cultivo). La técnica de electrospraying permitió la obtención de matrices porosas formadas por microgotas tal como se observa mediante SEM. La adhesión y proliferación y la actividad de ALP de las células crecidas sobre las películas aumento significativamente sobre la matriz porosa respecto a la matriz no porosa. El aumento del área superficial proporcionada por la estructura porosa incrementó los marcadores de actividad celular

Fumarate Copolymer–Chitosan Cross-Linked Scaffold Directed to Osteochondrogenic Tissue Engineering

Natural and synthetic cross-linked polymers allow the improvement of cytocompatibility and mechanical properties of the individual polymers. In osteochondral lesions of big size it will be required the use of scaffolds to repair the lesion. In this work a borax cross-linked scaffold based on fumarate-vinyl acetate copolymer and chitosan directed to osteochondrondral tissue engineering is developed. The cross-linked scaffolds and physical blends of the polymers are analyzed in based on their morphology, glass transition temperature, and mechanical properties. In addition, the stability, degradation behavior, and the swelling kinetics are studied. The results demonstrate that the borax cross-linked scaffold exhibits hydrogel behavior with appropriated mechanical properties for bone and cartilage tissue regeneration. Bone marrow progenitor cells and primary chondrocytes are used to demonstrate its osteo- and chondrogenic properties, respectively, assessing the osteoand chondroblastic growth and maturation, without evident signs of cytotoxicity as it is evaluated in an in vitro system.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasLaboratorio de Investigación en Osteopatías y Metabolismo Minera

Cytotoxicity of copper and silver ions on specific osteoblastic properties

La plata y el cobre son ampliamente utilizados como componentes de materiales dentales, aún cuando su resistencia a la corrosión es baja. Los iones liberados pueden producir varios efectos indeseables tales como reacciones tóxicas, de inflamación y mutagénicas. El objetivo del presente estudio fue evaluar la biocompatibilidad de los componentes de los materiales dentales con respecto al crecimiento y diferenciación de las células osteoblásticas UMR106, en respuesta a disoluciones salinas de los cationes metálicos y a la liberación de los iones (Cu2+, Ag+) a partir de los metales puros. Las células control UMR106 mostraron una morfología poligonal normal con procesos citoplasmáticos conectando las células vecinas. Después de 24 h en cultivo las células expuestas al cobre mostraron importantes cambios morfológicos. En períodos más prolongados (48 h) los iones cobre indujeron la casi completa muerte de las células. Las exposiciones a los iones plata por 48 h causaron menos reducción del número de células saludables. Los osteoblastos eran relativamente pequeños con cierta pérdida de procesos, observ ándose algunas figuras mitóticas y cuerpos apoptóticos. El efecto del cobre sobre la inhibición del crecimiento de las células era linealmente dependiente con el tiempo. Tanto las células sobrevivientes como el índice mitótico se correlacionaron significativamente con la cantidad de cobre en el medio, a pesar de que esta correlaci ón era más fuerte cuando se analizaba el número de células sobrevivientes en comparación con el índice mitótico. Se pudo concluir que los iones cobre y plata son citotóxicos. En el caso de los iones cobre, se encontró una correlación de segundo orden entre la cytotoxicidad y la concentración de iones liberados.Copper and silver are widely used as components of dental materials even though their corrosion resistance is low. The released ions can produce several undesirable effects such as toxic, allergic, inflammatory and mutagenic reactions. The aim of the present study was to evaluate the biocompatibility of the components of dental metal materials on the growth and differentiation of UMR106 osteoblast cells in response to salt solutions of the metallic ions (Cu2+ and Ag+) and to ions released from pure metals. The control UM106 cells exhibited normal polygonal morphology with cytoplasmic processes connecting neighbouring cells. After 24 h in culture, cells exposed to Cu showed important morphological changes. After a longer incubation (48 h) the copper ions induced almost a complete cellular death of the culture. Exposition to silver for 48 h caused a lower reduction in the healthy cells in the culture. Osteoblasts were relatively small with lost of processes, although some mitotic figures and apoptotic bodies were still observed. The effect of Cu on the inhibition of cell growth was linearly time-dependent. Both cell surviving and the MI, significantly correlated with the Cu levels in the media, although this correlation was stronger when the number of surviving cells was analysed, in comparison with the mitotic index. It could be concluded that copper and silver ions are cytotoxic. In the case of copper ions a second order correlation between cytotoxicity and the concentration of the released metal ions was found