Effect of energy level of photobiomodulation therapy on bone repair in rats / Efecto del nivel de energía de la terapia de fotobiomodulación sobre la reparación ósea en ratas

Abstract The aim of this experimental study was to determine the effect of photobiomodulation therapy on bone repair in a rat tibia osteotomy model at 15 and 30 days. The sample consisted of 36 male Holtzman rats that were randomized into 6 equal groups. Groups A1 and A2: osteotomy + 1 J laser energy. Groups B1 and B2: osteotomy + 3 J laser energy. Groups C1 and C2 (controls): osteotomy only. The bone repair was analyzed by histological evaluation of osteoblasts and osteocytes both at 15 days (groups A1, B1, and C1) and at 30 days (groups A2, B2, and C2). Within the results, in all groups a greater number of osteoblasts was found at 15 days vs 30 days (p<0.05), and a greater number of osteocytes in B1 and C2 vs B2 and C1, respectively (p<0.05). When evaluating the 3 groups worked up to 15 days, more osteoblasts were found in A1 and C1 vs B1 (p<0.001); and osteocytes predominated in A1 and B1 vs C1 (p<0.001). At 30 days there was a greater quantity of osteoblasts in C2 vs A2 and B2 (p<0.05) and of osteocytes in C2 vs B2 (p<0.05). It is concluded that 1 J photobiomodulation therapy improved bone repair at 15 days; however, this improvement was not observed at 30 days because there were no differences between the irradiated groups and the control.

Resumen El objetivo de este estudio experimental fue determinar el efecto de terapia de fotobiomodulación sobre la reparación ósea en un modelo de osteotomía de tibia de rata a los 15 y 30 días. La muestra estuvo compuesta por 36 ratas Holtzman macho que se aleatorizaron en 6 grupos iguales. Grupos A1 y A2: osteotomía + energía láser de 1 Joule. Grupos B1 y B2: osteotomía + energía láser 3 Joule. Grupos C1 y C2 (controles): solo osteotomía. La reparación ósea fue analizada por evaluación histológica de osteoblastos y osteocitos tanto a los 15 días (grupos A1, B1 y C1) como a los 30 días (grupos A2, B2 y C2). Como resultados se encontró que en todos los grupos hubo mayor número de osteoblastos a los 15 días vs. 30 días (p<0,05), y mayor número de osteocitos en B1 y C2 vs B2 y C1, respectivamente (p<0,05). Al evaluar a los animales a los 15 días, se observó mayor número de osteoblastos en A1 y C1 vs B1 (p<0.001); y mayor número de osteocitos en A1 y B1 vs C1 (p<0,001). Al evaluar a los ratones a los 30 días hubo mayor cantidad de osteoblastos en C2 vs A2 y B2 (p<0,05) y de osteocitos en C2 vs B2 (p<0,05). Se concluye que la terapia de fotobiomodulación con 1 Joule mejoró la reparación ósea a los 15 días; sin embargo, dicha mejora no se observó a los 30 días porque no hubo diferencias entre los grupos irradiados y el control.

What changes in the biology of bone movement induced with mini-implants/miniplates is the synchronicity

ABSTRACT Introduction: Induced tooth-bone movement occurs by a synchronicity of dental and bone phenomena, thanks to the osteocytic network, which is a three-dimensional network that controls the bone shape or design. Objective: To describe the tooth-bone movement induced by enhanced anchorage, divided into three distinct moments: zero, start and stop. Question: From this description, the main question arises: with the use of mini-implants/miniplates, what changes in the biology of induced tooth-bone movement? The answer is: nothing changes, either biologically or microscopically. Conclusion: This technique optimizes the treatment time, and the range of therapeutic possibilities is broadened, thanks to the synchronicity of phenomena - which remain the same, in all teeth and bones, yet in a synchronized manner. Bone anchorage represents synchronicity in induced tooth-bone movement.

RESUMO Introdução: A movimentação osseodentária induzida ocorre meio de uma sincronicidade de fenômenos dentários e ósseos, graças à rede osteocítica, uma rede tridimensional de controle do formato ou design ósseo. Objetivo: Descrever a movimentação osseodentária induzida com ancoragem ampliada, dividindo-a em três momentos distintos: zero, start e stop. Questionamento: Dessa descrição origina-se a principal pergunta: com o uso de mini-implantes/miniplacas, o que muda na biologia da movimentação osseodentária induzida? A resposta é: não muda nada, nem biologicamente, nem microscopicamente. Conclusão: O que se otimiza, com essa técnica, é o tempo de tratamento, e se amplia o leque de possibilidades terapêuticas, graças à sincronicidade dos fenômenos - que continuam sendo os mesmos, em todos os dentes e nos ossos, só que de forma sincronizada. A ancoragem óssea representa a sincronicidade na movimentação osseodentária induzida.

Radiotherapy-induced bone deterioration is exacerbated in diabetic rats treated with streptozotocin

Following radiotherapy, patients have decreased bone mass and increased risk of fragility fractures. Diabetes mellitus (DM) is also reported to have detrimental effects on bone architecture and quality. However, no clinical or experimental study has systematically characterized the bone phenotype of the diabetic patients following radiotherapy. After one month of streptozotocin injection, three-month-old male rats were subjected to focal radiotherapy (8 Gy, twice, at days 1 and 3), and then bone mass, microarchitecture, and turnover as well as bone cell activities were evaluated at 2 months post-irradiation. Micro-computed tomography results demonstrated that DM rats exhibited greater deterioration in trabecular bone mass and microarchitecture following irradiation compared with the damage to bone structure induced by DM or radiotherapy. The serum biochemical, bone histomorphometric, and gene expression assays revealed that DM combined with radiotherapy showed lower bone formation rate, osteoblast number on bone surface, and expression of osteoblast-related markers (ALP, Runx2, Osx, and Col-1) compared with DM or irradiation alone. DM plus irradiation also caused higher bone resorption rate, osteoclast number on bone surface, and expression of osteoclast-specific markers (TRAP, cathepsin K, and calcitonin receptor) than DM or irradiation treatment alone. Moreover, lower osteocyte survival and higher expression of Sost and DKK1 genes (two negative modulators of Wnt signaling) were observed in rats with combined DM and radiotherapy. Together, these findings revealed a higher deterioration of the diabetic skeleton following radiotherapy, and emphasized the clinical importance of health maintenance.

Expression of CD44 in previously grafted alveolar bone / Expresión del marcador óseo CD44 en hueso alveolar previamente injertado

Objetive: To determine the expressions of the bone surface marker CD44 in samples of alveolar bone previously regenerated with allograft, xenograft, and mixed, using the technique of guided bone regeneration. Material and Methods: This exploratory study was approved by the institutional research and ethics committee. By means of intentional sampling and after obtaining informed consent for tissue donation, 20 samples of alveolar bone previously regenerated with guided bone regeneration therapy with particulate bone graft and membrane were taken during implant placement. The samples were stained with hematoxylin-eosin for histological analysis, and by immunohistochemistry for the detection of CD44. Results: Sections with hematoxylin-eosin showed bone tissue with the presence of osteoid matrix and mature bone matrix of usual appearance. Of the CD44+ samples, 80% were allograft and 20% xenograft. The samples with allograft-xenograft were negative. There were no differences in the intensity of CD44 expression between the positive samples. The marker was expressed in osteocytes, stromal cells, mononuclear infiltrate, and some histiocytes. Eighty percent of the CD44+ samples and 100% of the samples in which 60 or more cells were labelled corresponded to allografts (p=0.000). A total of 67% of the samples from the anterior sector, and 40% from the posterior sector were CD44+ (p=0.689). Conclusion: This study shows for the first time that guided bone regeneration using allografts is more efficient for the generation of mature bone determined by the expression of CD44, compared to the use of xenografts and mixed allograft-xenograft, regardless of the regenerated anatomical area.

Objetivo: Determinar la expresión del marcador de membrana óseo CD44 en muestras de hueso alveolar previamente regenerado con aloinjerto, xenoinjerto y mezcla mediante la técnica de regeneración ósea guiada. Material y Métodos: Con aval del Comité de Investigación y Ética, se realizó un estudio exploratorio. Por muestreo intencional y firma de consentimiento informado de donación, se tomaron durante la colocación del implante, 20 muestras de hueso alveolar previamente regenerado con terapia de regeneración ósea guiada con injerto óseo particulado y membrana. Las muestras fueron teñidas con hematoxilina-eosina para el análisis histológico y por inmunohistoquímica para la detección del CD44. Resultados: : Los cortes con hematoxilina-eosina mostraron tejido óseo con presencia de matriz osteoide y matriz ósea madura de aspecto usual. De las muestras CD44+, 80% fueron de aloinjerto y 20% de xenoinjerto. Las muestras con aloinjerto-xeoninjerto fueron negativas. No hubo diferencias en la intensidad de la expresión del CD44 entre las muestras positivas. El marcador se expresó en osteocitos, células estromales, infiltrado mononuclear y algunos histiocitos. El 80% de las muestras CD44+ y el 100% de las muestras con marcación de 60 o más células correspondían a aloinjertos (p=0,000). El 67% de las muestras del sector anterior y el 40% del sector posterior fueron CD44+ (p=0,689). Conclusión: Este estudio muestra por primera vez que la regeneración ósea guiada usando aloinjertos, es más eficiente para la generación de hueso maduro determinado por la expresión de CD44, comparado con el uso de xenoinjertos y mezcla de aloinjerto-xenoinjerto, independientemente del sector anatómico regenerado.

Evaluation of Effects of Irradiation with 980 nm Diode Laser at 0.8 W, 1.2 W and 1.4 W, on Sheep Bone - An In Vitro Histological Study

Diode laser has been a boon to treat various periodontal diseases in the last decade. Literature cautions that contact of diode laser would be detrimental to bone and leads to bone resorption. However, till date no studies have documented bone damage at different power settings of laser. So, the objective of this study was to evaluate the effects of 980 nm diode laser irradiation on sheep bone under different power settings in continuous wave mode for fixed amount of time. MethodsA fresh femur of sheep devoid of any muscle and soft tissue was obtained. Three markings, each 10 mm long were made for the specimens. The specimens were categorized as sample A, B and C. 980 nm Diode Laser was used to irradiate the specimens with 0.8 W, 1.2 W and 1.4 W at continuous mode as the power settings for sample A, B and C respectively for 10 seconds in direct contact with bone in a brushing like pattern. ResultsThe depth of bone damage was measured using Haematoxylin and Eosin stain. Bone damage was minimum for group 1 followed by group 2 and 3. ConclusionsWhen the specimens were irradiated by a 980 nm diode laser in direct contact with the bone tissue, damage was seen both clinically and microscopically in all groups.

Observation of dendrite osteocytes of mice at different developmental stages using Ploton silver staining and phalloidin staining / 南方医科大学学报

OBJECTIVE@#To assess the value of Ploton silver staining and phalloidin-iFlour 488 staining in observation of the morphology of osteocyte dendrites of mice at different developmental stages.@*METHODS@#The humerus and femurs were harvested from mice at 0 (P0), 5 (P5), 15 (P15), 21 (P21), 28 (P28), and 35 days (P35) after birth to prepare cryo-sections and paraffin sections. HE staining of P35 mouse femur sections served as a reference for observing osteocytes in the trabecular bone and cortical bone. The humeral sections at different developmental stages were stained with Ploton silver staining to observe the morphology of osteocytes and canaliculi, and the canalicular lengths in the cortical and trabecular bones of the humerus of the mice in each developmental stage were recorded. The cryo-sections of the humerus from P10 and P15 mice were stained with phalloidin iFlour-488 to observe the morphology of osteocytes and measurement of the length of osteocyte dendrites in the cortical bone.@*RESULTS@#In the trabecular bone of the humerus of P0-P15 mice, Ploton silver staining only visualized the outline of the osteocytes, and the morphology of the canaliculi was poorly defined. In P21 or older mice, Ploton silver staining revealed the morphology of the trabecular bone osteocytes and the canaliculi, which were neatly arranged and whose lengths increased significantly with age (P21 @*CONCLUSIONS@#Mouse osteocyte dendrites elongate progressively and their arrangement gradually becomes regular with age. Ploton silver staining can clearly visualize the morphology of the osteocytes and the canaliculi in adult mice but not in mice in early stages of development. Phalloidin iFlour-488 staining for labeling the cytoskeleton can be applied for mouse osteocytes at all developmental stages and allows morphological observation of mouse osteocytes in early developmental stages.

Research progress on the relationship between osteocytes and periodontitis / 口腔疾病防治

@#Osteocytes, which develop from osteoblasts, are recognized as the main cells embedded in mature bone tissue. The traditional notion is that osteocytes exclusively play a structural role, however, with the development of related research in recent years, the role of osteocytes in bone metabolism has been explored. Periodontitis is a chronic inflammatory disease initiated by plaque biofilm, and is the main cause of adult tooth loss. Clinically, periodontitis primarily manifests as attachment loss, bleeding on probing and other symptoms. Alveolar bone resorption is the most characteristic pathological change. Current research demonstrated that osteocytes sense mechanical stress, participate in bone remodeling, regulate mineral balance, and participate in endocrine function. Thus, these cells play an important role in bone homeostasis and systemic metabolic balance. Osteocytes are actively involved in the development of periodontitis through the high expression of receptor activator of nuclear factor kappa B ligand (RANKL), secretion of sclerostin, and effect on apoptosis, senescence and autophagy. In the future, the detection of bone cell metabolism-related products will have certain application prospects for the clinical evaluation of periodontitis prevention and treatment. Therefore, this paper reviewed the role of osteocytes in bone homeostasis and the relationship between osteocytes and periodontitis, to provide new ideas for the prevention and treatment of periodontitis.

Effects of Simulated Microgravity on Function of SOC Channels in Osteocytes MLO-Y4 / 医用生物力学

Objective To study the effect of simulated microgravity on activity of the store-operated calcium (SOC) channels in osteocytes and its possible mechanism, so as to elucidate the potential mechanism of weightlessness bone loss. Methods Osteocytes (MLO-Y4) as the experimental subjects were divided into simulated microgravity (SM) group and normal gravity group (CON). After rotating for 24 h and 48 h, confocal microscope was used to detect the intracellular calcium ion concentration level to reflect activity of the SOC channels after thapsigargin (TG)-induced endoplasmic reticulum (ER) depletion. Immunofluorescence staining was used to observe the distribution of ER membrane protein IP3R and spectrin membrane skeleton, in order to preliminarily explore the possible mechanism of functional changes of SOC channels. Results During the period of calcium release from ER, ［Ca2+］i had no significant difference between SM group and CON group for 24 h and 48 h; while during the period of extracellular calcium influx by SOC channels, ［Ca2+］i of SM group had significant differences in the first 4 minutes for 24 h, as well as in the whole time for 48 h. Compared with CON group, the spectrin membrane skeleton of SM group was gathered at the rim of membrane, while ER membrane protein IP3R of SM group was gathered at the nuclear envelope of ER. These two tendencies were more obvious for 48 h. Conclusions The stimulated microgravity could inhibit activity of SOC channels in osteocytes. Changes in the distribution of the spectrin membrane skeleton and ER membrane protein IP3R under the simulated microgravity might reduce the activity of SOC channels by affecting the conformation coupling process between the membrane and ER.

Predicting the Role of Osteal Macrophages and Osteocytes in Bone Tissue Network Using a Mathematical Modeling / 치위생과학회지

The aim of this study was to investigate the role of osteal macrophages (osteomac) and osteocytes in bone remodeling using a mathematical model. We constructed the bone system with pre-osteoblasts, osteoclasts, osteocytes, and osteomac. Each link of the parameters and ordinary differential equations followed the Graham's model in 2013 except for the parameters of osteomac signaling and osteocytes signaling to link preosteoblasts and osteoblasts. We simulated the changes in each cell and bone volume according to the changes in the parameters of osteomac signaling and osteocytes signaling. The results showed bone volume was unstable and decreased gradually when the effectiveness of osteocytes and osteomac dropped below a certain level. When the parameters of osteomac signaling and osteocytes signaling to link preosteoblasts and osteoblasts had a value less than 1, bone volume increased with the increase in the parameter of osteomac signaling to link preosteoblasts and osteoblasts. Moreover, although the parameter of osteocytes signaling to link preosteoblasts and osteoblasts, increased in case of a small parameter of osteomac signaling, bone volulme decreased. If the parameters of osteomac signaling to link preosteoblasts and osteoblasts were over a certain level, bone volume was positively maintained, despite the parameter of osteocyte signaling to link preosteoblasts and osteoblasts. We suggested the osteomac may affect bone remodeling and may play an important role in bone cell network.

TCP wear particles causes injury of periprosthetic osteocytes in the mouse calvaria / 中国应用生理学杂志

OBJECTIVE@#To study whether tricalcium phosphate(TCP) wear particles cause injuries of periprosthetic osteocytes in the mouse calvaria, and to explain its molecular mechanism.@*METHODS@#Thirty six-week(ICR)male mice were randomly divided into sham group, model (TCP) group and 3-methyladenine (3-MA) group. A murine calvarial model of osteolysis was established by 30 mg of TCP wear particles implantation over the periosteum around the middle suture of calvaria in mice. On the second postoperative day, the autophagy specific inhibitor 3-MA (1.0 mg/kg) was subcutaneously injected to the calvaria in the 3-MA-treated mice every other day. After 2 weeks, blood and the calvaria were obtained. Micro-CT was used to detect bone mineral density(BMD), bone volume fraction (BVF) and porosity number. HE staining and flow cytometry were performed to analyze the viability and apoptosis of periprosthetic osteocytes. The serum levels of dentin matrix protein 1(DMP-1) and sclerostin (SOST) were determined by ELISA. The proteins expressions of DMP-1, SOST, Beclin-1 and microtuble-associated protein 1 light chain 3 (LC-3) were detected by Western blot in the calvaria osteocytes.@*RESULTS@#Compared with the sham group, the mice in the TCP group showed that a significant decrease in the viability of periprosthetic osteocytes, but obvious increases in number of osteocytes death and osteocytes apoptosis (<0.05), and in serum level and protein expression of SOST; significant decreases in serum level and protein expression of DMP-1 (<0.05), and remarkable up-regulation of autophagy-related factors beclin-1 and the conversion of LC3-Ⅱ from LC3-I in the calvaria osteocytes. Compared with TCP group, the mice in the 3-MA group showed that injuries of calvaria osteocytes were obviously aggravated, and osteocytes apoptosis was significantly increased (<0.05).@*CONCLUSIONS@#TCP wear particles can cause injuries of periprosthetic osteocytes via activation of apoptosis and autophagy, which promotes osteolysis around the prosthesis osteolysis and joint aseptic loosening.

Evaluation of apoptosis and osteopontin expression in osteocytes exposed to orthodontic forces of different magnitudes

The in vivo response of osteocytes to different force magnitudes soon after they are applied remains to be elucidated. The aim of this study was to examine the early effects of applying a very light (LF: 0,16 N) and a very strong (SF: 2,26 N) orthodontic force during one hour on apoptosis and osteopontin (OPN) expression on alveolar bone osteocytes, in rats. Results: LF: compared to the control group, they showed a significant increase in OPN expression, and a significant decrease in the number of TUNELpositive osteocytes. SF: compared to the control group, they showed a significant increase in OPN expression and a significant decrease in the number of TUNELpositive osteocytes. Our results show that osteocytes respond very early to the application of tension and pressure forces of different magnitudes, and application of forces decreases the number of apoptotic osteocytes and increases OPN expression. These results allow concluding that osteocytes activate rapidly when subjected to locally applied forces, whether these forces be pressure or tension, light or strong forces. Grants: UBACyT 200201301002270 BA and School of Dentistry, University of Buenos Aires (AU)

Hasta el momento no se ha dilucidado la respuesta temprana in vivo de los osteocitos a la aplicación de fuerzas de diferentes magnitudes sobre el hueso. El objetivo de este estudio fue examinar la respuesta temprana de la aplicación de una fuerza ortodóncica muy liviana (FL: 0,16 N) y muy fuerte (FF: 2,26 N) durante una hora sobre la expresión de apoptosis y osteopontina (OPN) en los osteocitos del hueso alveolar, en ratas. Resultados: FL: en comparación con el grupo control, mostraron un aumento significativo en la expresión de OPN y una disminución significativa en el número de osteocitos TUNELpositivos. FF: en comparación con el grupo control, mostraron un aumento significativo en la expresión de OPN y una disminución signi ficativa en el número de osteocitos TUNELpositivos. Nuestros resultados muestran que los osteocitos responden muy temprano a la aplicación de fuerzas de tensión y presión de diferentes magnitudes, y la aplicación de fuerzas disminuye el número de osteocitos apoptóticos y aumenta la expresión de OPN. Estos resultados permiten concluir que los osteocitos se activan rápidamente cuando se los somete a fuerzas aplicadas localmente, ya sean estas fuerzas de presión o tensión, livianas o fuertes (AU)

Visión celular y molecular de la ortopedia funcional de los maxilares

Actualmente, los mecanismos biológicos que subyacen a la estimulación ortopédica funcional están en proceso de entendimiento; sin embargo, se sabe que el osteocito juega un rol esencial, al recibir y transformar dicho estímulo funcional hacia una señal bioquímica, lo que da como consecuencia la secreción de diversas moléculas. Estas se movilizan entre los osteocitos, gracias a su extensa red de uniones comunicantes, y llegan en última instancia a activar a las células efectoras del tejido óseo: osteoblastos y osteoclastos. El objetivo de la revisión es actualizar y compendiar algunos de los más importantes mecanismos celulares y moleculares subyacentes a la terapia ortopédica funcional de los maxilares.

Currently, the biological mechanisms underlying functional orthopedic stimulation are in process of understanding. However, it is known that osteocyte plays an essential role, to receive and process the functional stimulus to biochemical signals giving as result the secretion of various molecules. Such molecules are mobilized between the osteocytes, thanks to its extensive network of gap junctions, ultimately coming to activate effector cells of bone tissue: osteoblasts and osteoclasts. The aim of the review is to update some of the cellular and molecular mechanisms underlying functional orthopedic therapy of the maxillary.

Efecto osteoinductor del mineral trióxido agregado versus el cemento Portland tipo I sobre lesiones óseas mandibulares

Introducción: Estudio experimental donde se procuró determinar el efecto osteoinductor del mineral trióxido agregado (MTA) versus el cemento Portland tipo I sobre lesiones óseas mandibulares. Metodología: Se emplearon 12 conejos machos de la raza New Zealand de 3 meses de edad, los cuales fueron divididos en 4 grupos iguales. Todos los conejos fueron anestesiados utilizando pentobarbital sódico. Se procedió a la incisión en la piel mandibular para exponer el hueso sobre el que se realizó 3 cavidades de 3mm cada una. En una cavidad se colocó MTA, en otra cemento Portland y en la tercena ninguna pasta. Se procedió al sacrificio de los grupos experimentales a la 1era, 2da, 3era y 4ta semana respectiva y se evaluó las muestras obtenidas de las áreas quirúrgicas mediante conteo de osteocitos y osteoblastos. Resultados: Tanto el MTA como el cemento Portland poseen la misma capacidad osteoinductiva en la 1era, 2da y 3era semana (p>0,05). Sin embargo, en la 4ta semana el MTA tuvo mayor capacidad osteoinductora al estimular mayor número de osteoblastos que el cemento Portland (p=0,024). Conclusiones: El MTA y el cemento Portland tipo I mostraron similar efecto osteoinductor durante las 3 primeras semanas de evaluación. El MTA demostró mayor efecto osteoinductor durante la cuarta semana de valoración.

Introduction: An experimental study was carried out to determine the osteoinductive effect of Mineral Trioxide Aggregate (MTA) versus Portland Cement type I on mandibular bone lesions. Methodology: Twelve 3-month-old male New Zealand rabbits were divided into 4 equal groups. All rabbits were anesthetized using Pentobarbital. An incision of the mandibular skin was performed to expose the bone on which 3 cavities of 2mm each one were made. In one cavity MTA was placed, in another Portland Cement type I and the third remained empty. The experimental groups were sacrificed at the 1st, 2nd, 3rd and 4th respective weeks and evaluated histologically by counting osteocytes and osteoblasts. Results: Both MTA and Portland cement have the same osteoinductive capacity in the 1st, 2nd and 3rd week (0.05

Hypoxia Inducible Factor-1alpha Directly Induces the Expression of Receptor Activator of Nuclear Factor-kappaB Ligand in MLO-Y4 Osteocytes

Osteocytes may function as mechanotransducers by regulating local osteoclastogenesis. Reduced availability of oxygen, i.e. hypoxia, could occur during disuse, bone development, and fracture. Receptor activator of nuclear factor-kappaB ligand (RANKL) is an osteoblast/stromal cell derived essential factor for osteoclastogenesis. The hypoxia induced osteoclastogenesis via increased RANKL expression in osteoblasts was demonstrated. Hypoxic regulation of gene expression generally involves activation of the hypoxia-inducible factor (HIF) transcription pathway. In the present study, we investigated whether hypoxia regulates RANKL expression in murine osteocytes and HIF-1alpha mediates hypoxia-induced RANKL expression by transactivating RANKL promoter, to elucidate the role of osteocyte in osteoclastogenesis in the context of hypoxic condition. The expression levels of RANKL mRNA and protein, as well as hypoxia inducible factor-1alpha (HIF-1alpha) protein, were significantly increased in hypoxic condition in MLO-Y4s. Constitutively active HIF-1alpha alone significantly increased the levels of RANKL expression in MLO-Y4s under normoxic conditions, whereas dominant negative HIF-1alpha blocked hypoxia-induced RANKL expression. To further explore to find if HIF-1alpha directly regulates RANKL transcription, a luciferase reporter assay was conducted. Hypoxia significantly increased RANKL promoter activity, whereas mutations of putative HIF-1alpha binding elements in RANKL promoter prevented this hypoxia-induced RANKL promoter activity in MLO-Y4s. These results suggest that HIF-1alpha mediates hypoxia-induced up-regulation of RANKL expression, and that in osteocytes of mechanically unloaded bone, hypoxia enhances osteoclastogenesis, at least in part, via an increased RANKL expression in osteocytes.

Mini-implants and miniplates generate sub-absolute and absolute anchorage

The functional demand imposed on bone promotes changes in the spatial properties of osteocytes as well as in their extensions uniformly distributed throughout the mineralized surface. Once spatial deformation is established, osteocytes create the need for structural adaptations that result in bone formation and resorption that happen to meet the functional demands. The endosteum and the periosteum are the effectors responsible for stimulating adaptive osteocytes in the inner and outer surfaces.Changes in shape, volume and position of the jaws as a result of skeletal correction of the maxilla and mandible require anchorage to allow bone remodeling to redefine morphology, esthetics and function as a result of spatial deformation conducted by orthodontic appliances. Examining the degree of changes in shape, volume and structural relationship of areas where mini-implants and miniplates are placed allows us to classify mini-implants as devices of subabsolute anchorage and miniplates as devices of absolute anchorage.

Uma demanda funcional sobre o osso promove alterações na forma espacial da rede de osteócitos e seus prolongamentos, distribuídos uniformemente na estrutura mineralizada. A partir da deformação espacial captada, os osteócitos comandam a necessidade de adaptações estruturais, formando osso em novas áreas e reabsorvendo em outras, para que sejam atendidas as demandas funcionais. O endósteo e o periósteo são os verdadeiros efetores desses estímulos osteocíticos adaptativos, nas superfícies internas e externas. As alterações de forma, volume e posição dos ossos maxilares, nas correções esqueléticas da maxila e mandíbula, requerem uma ancoragem para que a remodelação óssea redefina a morfologia, a estética e as funções, a partir de deformações espaciais dirigidas por aparelhos. Verificar o grau de alterações na forma, volume e relações estruturais das áreas onde se fixaram os mini-implantes e as miniplacas poderá levar à classificação dos mini-implantes como dispositivos de ancoragem subabsoluta e as miniplacas, como de ancoragem absoluta.

Influencia de la variación de la presión de oxígeno ambiental en la formación ósea en cuyes nativos del nivel del mar / Influence of environmental oxygen pressure variation in sea level native guinea pigs bone formation

Introducción: La hipoxia caracteriza a los tejidos inicialmente injuriados; la variación en la disposición del oxígeno tisular en el proceso de reparación ósea determina la aparición de diversas moléculas implicadas en la sanación del tejido. Objetivos: Determinar si la variación de la presión de oxígeno ambiental influirá en la formación ósea posterior a una osteotomía en cuyes nativos del nivel del mar. Diseño: Experimental. Lugar: Facultad de Odontología de la Universidad Nacional Mayor de San Marcos, Lima, Perú, e Instituto Veterinario de Investigaciones Tropicales y de Altura, Mantaro, Perú. Material biológico: Cuyes. Intervenciones: Se utilizó 5 grupos de 10 cuyes cada uno, uno sin inducción de osteotomía (grupo control) y cuatro grupos experimentales: mar 15 días y mar 30 días (expuestos a PO2 ambiental de 157 mmHg), altura 15 días y altura 30 días (expuestos a PO2 ambiental de 107 mmHg). Principales medidas de resultados: Conteo de osteocitos. Resultados: El grupo mar 15 días presentó menor número de osteocitos comparado con el grupo altura 15 días (63 180 vs. 80 310, p<0,05). A su vez, el grupo mar 30 días presentó también menor número de osteocitos comparado con el grupo altura 30 días (160 640 vs. 167 370, p<0,05). Conclusión: La menor presión de oxígeno ambiental favoreció una mayor formación ósea en cuyes nativos del nivel mar...

Introduction: Hypoxia characterizes initially injured tissue; variation in oxygen available determines the appearance of molecules involved in bone repair. Objectives: To determine if environmental oxygen pressure variation influences bone formation following osteotomy in sea level native guinea pigs. Design: Experimental. Setting: Faculty of Dentistry, Universidad Nacional Mayor de San Marcos, Lima, Peru, and Tropical and High Altitude Research Veterinary Institute, Mantaro, Peru. Biological material: Guinea pigs. Interventions: Five groups of 10 guinea pigs each included one without osteotomy (control group) and four experimental groups: sea 15 days and sea 30 days (exposed to environmental PO2 157 mmHg), high altitude 15 days and high altitude 30 days (exposed to environmental PO2 107 mmHg). Main outcome measures: Osteocytes count. Results: The 15 days sea group had lower number of osteocytes compared with the 15 days high altitude group (63 180 vs. 80 310, p<0.05). The 30 days sea group had also lower number of osteocytes compared with the 30 days high altitude group (160 640 vs. 167 370, p<0.05). Conclusions: The lower environmental oxygen pressure favored higher bone formation in sea level native guinea pigs...

Role of Osteocyte-derived Insulin-Like Growth Factor I in Developmental Growth, Modeling, Remodeling, and Regeneration of the Bone

The osteocyte has long been considered to be the primary mechanosensory cell in the bone. Recent evidence has emerged that the osteocyte is also a key regulator of various bone and mineral metabolism and that its regulatory effects are in part mediated through locally produced osteocyte-derived factors, such as sclerostin, receptor activator of nuclear factor-kappa B ligand (RANKL), and fibroblast growth factor (FGF)-23. Osteocytes secrete large amounts of insulin-like growth factor (IGF)-I in bone. Although IGF-I produced locally by other bone cells, such as osteoblasts and chondrocytes, has been shown to play important regulatory roles in bone turnover and developmental bone growth, the functional role of osteocyte-derived IGF-I in the bone and mineral metabolism has not been investigated and remains unclear. However, results of recent studies in osteocyte Igf1 conditional knockout transgenic mice have suggested potential regulatory roles of osteocyte-derived IGF-I in various aspects of bone and mineral metabolism. In this review, evidence supporting a regulatory role for osteocyte-derived IGF-I in the osteogenic response to mechanical loading, the developmental bone growth, the bone response to dietary calcium depletion and repletion, and in fracture repair is discussed. A potential coordinated regulatory relationship between the effect of osteocyte-derived IGF-I on bone size and the internal organ size is also proposed.

Construction and identification of lentiviral vector encoding human survivin gene / 中国组织工程研究

BACKGROUND:Inhibiting the apoptosis of intervertebral disc cel s can postpone the degenerative process of intervertebral disc. Survivin has a strong function of regulating cel proliferation and anti-apoptosis. OBJECTIVE:To construct and identify the lentiviral vector encoding survivin gene of human. METHODS:The survivin gene of human (BIRC5) was synthesized through the gene synthesis technology, amplified by PCR and analyzed by electrophoresis. The target gene was cloned into lentiviral expression plasmid to obtain the recombinant lentiviral vector Lenti-BIRC5. After transformation into competent E. coli cel s, the candidate clones were identified by PCR firstly. The positive clones were identified by gene sequencing. The lentivirus plasmid containing target gene was transfected into 293T cel s, and the expression of recombinant lentiviral vector Flag-Survivin fusion protein was detected through western blot analysis. RESULTS AND CONCLUSION:The PCR results of electrophoresis and DNA sequencing showed that lentiviral vector containing human survivin gene was constructed successful y. Western blot analysis results showed that the target gene was transfected successful y and over-expressed in cultured cel s. The lentiviral expression vector of human survivin gene Lenti-BIRC5 was constructed successful y, which lays a foundation for the study addressing the anti-apoptotic effects of survivin on human nucleus pulposus cel s.

Recent Progress in Osteocyte Research

The last decade has seen an exponential increase in our understanding of osteocytes function and biology. These cells, once considered inert by-standers trapped into the mineralized bone, has now risen to be key regulators of skeletal metabolism, mineral homeostasis, and hematopoiesis. As tools and techniques to study osteocytes improved and expanded, it has become evident that there is more to these cells than initially thought. Osteocytes are now recognized not only as the key responders to mechanical forces but also as orchestrators of bone remodeling and mineral homeostasis. These cells are the primary source of several important proteins, such as sclerostin and fibroblast growth factor 23, that are currently target as novel therapies for bone loss (as the case for antisclerostin antibodies) or phosphate disorders. Better understanding of the intricate cellular and molecular mechanisms that govern osteocyte biology will open new avenue of research and ultimately indentify novel therapeutics to treat bone and mineral disorders. This review summarizes novel findings and discusses future avenues of research.

Recent Progress in Osteocyte Research

The last decade has seen an exponential increase in our understanding of osteocytes function and biology. These cells, once considered inert by-standers trapped into the mineralized bone, has now risen to be key regulators of skeletal metabolism, mineral homeostasis, and hematopoiesis. As tools and techniques to study osteocytes improved and expanded, it has become evident that there is more to these cells than initially thought. Osteocytes are now recognized not only as the key responders to mechanical forces but also as orchestrators of bone remodeling and mineral homeostasis. These cells are the primary source of several important proteins, such as sclerostin and fibroblast growth factor 23, that are currently target as novel therapies for bone loss (as the case for antisclerostin antibodies) or phosphate disorders. Better understanding of the intricate cellular and molecular mechanisms that govern osteocyte biology will open new avenue of research and ultimately indentify novel therapeutics to treat bone and mineral disorders. This review summarizes novel findings and discusses future avenues of research.