RESUMEN
It was hypothesized that strontium (Sr)-doped ß-tricalcium phosphate (TCP)-based scaffolds have a positive effect on the regeneration of large bone defects (LBD). Readouts in our mice models were nuclear factor-kappa beta (NF-κB) activity and vascular endothelial growth factor receptor-2 (VEGFR-2) promoter activity during the healing process. A 2-mm critical-size femoral fracture was performed in transgenic NF-κB- and VEGFR-2-luciferase reporter mice. The fracture was filled with a 3D-printed ß-TCP scaffold with or without Sr. A bioluminescence in-vivo imaging system was used to sequentially investigate NF-κB and VEGFR-2 expression for two months. After sacrifice, soft and osseous tissue formation in the fracture sites was histologically examined. NF-κB activity increased in the ß-TCP + Sr group in the latter stage (day 40-60). VEGFR-2 activity increased in the + Sr group from days 0-15 but decreased and showed significantly less activity than the ß-TCP and non-scaffold groups from days 40-60. The new bone formation and soft tissue formation in the + Sr group were significantly higher than in the ß-TCP group, whereas the percentage of osseous tissue formation in the ß-TCP group was significantly higher than in the ß-TCP + Sr group. We analyzed longitudinal VEGFR-2 promoter activity and NF-κB activity profiles, as respective agents of angiogenesis and inflammation, during LBD healing. The extended inflammation phase and eventually more rapid resorption of scaffold caused by the addition of strontium accelerates temporary bridging of the fracture gaps. This finding has the potential to inform an improved treatment strategy for patients who suffer from osteoporosis.
Asunto(s)
Fosfatos de Calcio/química , FN-kappa B/genética , Fosfatidiletanolaminas/química , Regiones Promotoras Genéticas , Estroncio/química , Receptor 2 de Factores de Crecimiento Endotelial Vascular/genética , Animales , Regeneración Ósea , Sustitutos de Huesos , Huesos/metabolismo , Inmunohistoquímica , Ratones , Ratones Transgénicos , FN-kappa B/metabolismo , Andamios del Tejido , Receptor 2 de Factores de Crecimiento Endotelial Vascular/metabolismoRESUMEN
BACKGROUND: Bisphosphonates are a main component in the therapy of osteoporosis and other bone resorptive diseases. Previous studies have shown a positive effect of systemically applied bisphosphonates on fracture healing. Nevertheless high doses are related to side effects like osteonecrosis of the jaw, nephrotoxis and gastrointestinal symptoms. In this study we investigated the effect of locally applied pamidronate on fracture healing. METHODS: In a rodent model a simple femur fracture was set in female Wistar rats. We performed intramedullary fixation of the fracture and placed a collagen matrix around the fracture area. One group was treated with pamidronate, the other group with placebo via the matrix. To investigate the volume and quality of the callus we used micro-CT (µCT) and histology after 14 and 28 days. RESULTS: Our results show a positive influence of local applied pamidronate on callus volume. After 14 days an insignificant increase of callus volume in the treated animals was seen. 28 days after trauma the increase of callus volume in the treatment group was significantly higher in comparison to the control group. Osteonecrosis was not seen. CONCLUSIONS: Locally applied bisphosphonates increase the callus volume in fracture healing.
Asunto(s)
Conservadores de la Densidad Ósea/administración & dosificación , Conservadores de la Densidad Ósea/uso terapéutico , Difosfonatos/administración & dosificación , Difosfonatos/uso terapéutico , Fracturas del Fémur/tratamiento farmacológico , Fémur/fisiología , Curación de Fractura/efectos de los fármacos , Animales , Conservadores de la Densidad Ósea/efectos adversos , Colágeno/química , Difosfonatos/efectos adversos , Modelos Animales de Enfermedad , Femenino , Fracturas del Fémur/cirugía , Fémur/efectos de los fármacos , Fémur/cirugía , Fijación Intramedular de Fracturas , Humanos , Pamidronato , Ratas , Ratas Wistar , Andamios del Tejido/química , Microtomografía por Rayos XRESUMEN
Porphyromonas gingivalis lipopolysaccharide (PG-LPS) is an important virulence factor potentially contributing to periodontal tissue destruction. Toll-like receptor 4 (Tlr4) is a key mediator of NF-kB activation during pathogen recognition. Previous work using Tlr4-specific antibodies demonstrated a partial neutralization of PG-LPS effects on murine cementoblasts, which can affect cell function and regulate gene expression of osteoclastic markers. PG-LPS also potentially influence the inflammation process and the resorption of mineralized tissues. Yet, such inflammatory responses and cell signaling events remain to be characterized at the protein level. We thus investigated the effect of 1 and 10 µg/ml of PG-LPS, respectively, on cell morphology, cell viability, and selected key downstream molecules of the Tlr4 signaling cascade in cementoblasts. High concentrations of PG-LPS (10 µg/ml) significantly reduced cell viability after 48 h. Upon PG-LPS-stimulation, Tlr4 was significantly downregulated. Equally, IκBα, a downstream molecule, was downregulated in terms of phosphorylation and protein production. Furthermore, downstream signaling kinases, like serine/threonine kinase phospho-AKT and the mitogen-activated protein kinase (MAPK)-family, specifically phospho-ERK1/2, were significantly upregulated under high PG-LPS-concentrations. We provide new insights into PG-LPS-triggered intracellular signaling pathways in cementoblasts and thus deliver a basis for further research in PG-mediated periodontal inflammation.
Asunto(s)
Lipopolisacáridos , Porphyromonas gingivalis , Proteínas Proto-Oncogénicas c-akt , Receptor Toll-Like 4 , Animales , Ratones , Cemento Dental/metabolismo , Inflamación , Lipopolisacáridos/toxicidad , Fosforilación , Porphyromonas gingivalis/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Receptor Toll-Like 4/metabolismoRESUMEN
BACKGROUND: Chronic alcohol consumption is a known limiting factor for bone healing. One promising strategy to improve bone augmentation techniques with Bio-Oss® in oral and maxillofacial surgery might be the supportive application of platelet-concentrated biomaterials as platelet-released growth factor (PRGF). To address this matter, we performed an in vitro study investigating the protective effects of PRGF and Bio-Oss® in ethanol (EtOH) treated osteoblasts. METHODS: The SAOS-2 osteosarcoma cell line, with and without EtOH pretreatment was used. The cell viability, proliferation and alkali phosphatase activity (ALP) after application of 0%, 5% and 10% PRGF and Bio-Oss® were assessed. RESULTS: The application of PRGF and Bio-Oss® in EtOH impaired osteoblasts showed a significant beneficial influence increasing the viability of the osteoblasts in cell culture. The synergistic effect of Bio-Oss® and 5% PRGF on the proliferation of osteoblasts was also demonstrated. Bio-Oss® only in combination with PRGF increases the alkaline phosphatase (ALP) activity in EtOH pretreated cells. CONCLUSIONS: These results indicate that the simultaneous application of PRGF and Bio-Oss® inhibits EtOH induced bone healing impairment. Furthermore, in the cells, PRGF induced a protective mechanism which might promote bone regeneration.
Asunto(s)
Plaquetas/metabolismo , Proliferación Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Etanol/toxicidad , Péptidos y Proteínas de Señalización Intercelular/administración & dosificación , Minerales/administración & dosificación , Osteoblastos/efectos de los fármacos , Sustitutos de Huesos/administración & dosificación , Línea Celular , Proliferación Celular/fisiología , Supervivencia Celular/fisiología , Citoprotección/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Combinación de Medicamentos , Humanos , Osteoblastos/citología , Osteoblastos/fisiología , Resultado del TratamientoRESUMEN
INTRODUCTION: Tears in the peripheral part of the menisci have a better healing potential than tears in the central part, because the central two-thirds of the menisci are avascular. We hypothesized that healing of meniscus tears in the avascular zone can be promoted by the local application of the angiogenic factor vascular endothelial growth factor (VEGF). MATERIALS AND METHODS: A tear was created in the avascular zone of the medial meniscus in 18 merino sheep. The tear was then repaired with an uncoated suture (group 1), a suture coated with PDLLA (group 2), and by a suture coated with PDLLA/VEGF (group 3). RESULTS: After 6 weeks, we observed increased immunostaining for factor VIII in the VEGF-treated group 3. However, in this treatment group no meniscus healed completely. In the uncoated suture group and in the PDLLA-coated-suture group, partial healing was observed in three animals and complete healing in three animals, respectively. CONCLUSION: In this experiment the local application of VEGF via PDLLA-coated sutures did not promote meniscus healing. Growth factors might not always be a promising tool for tissue repair.