Long-Term Oral Toxicity and Anti-osteoporotic Effect of Sintered Dicalcium Pyrophosphate in Rat Model of Postmenopausal Osteoporosis.

Sintered dicalcium pyrophosphate (SDCP), a synthetic pyrophosphate analog, has shown potential for the management of osteoporosis. The long-term oral toxicity and anti-osteoporotic effect of SDCP in a postmenopausal osteoporosis rat model were evaluated in this study. SDCP was orally administered to bilateral ovariectomized (OVX) Wistar rats at a dose of 0.75 mg/kg daily for 24 weeks following by 2 weeks of observation. There were no abnormal findings in clinical signs of toxicity, food consumption, body weight, blood examination, necropsy, and histological inspection attributable to the ingestion of SDCP. The serum level of type I collagen fragments, a bone resorption marker, decreased in SDCP-treated rats, and the bone formation markers alkaline phosphatase, osteocalcin, and osteopontin significantly decreased. These findings indicate that the bone turnover rate decreased in SDCP-treated animals. Relative to OVX rats, the increase in serum tartrate-resistant acid phosphatase 5b level represents an increase in bony tissues in the SDCP-treated rats. Histological examinations of distal femoral metaphyses further revealed that the ingestion of SDCP improved the trabecular bone architecture and decreased bone porosity. Analysis of limb bone ashes showed a significant increase in bone mineral content. Our results show that SDCP inhibits bone resorption to restore bone mass in OVX rats without deleterious effects, and therefore that SDCP has potential in the management of osteoporosis.

Evaluation of the post-treatment anti-inflammatory capacity of osteoarthritic chondrocytes: An in vitro study using baicalein.

INTRODUCTION: Targeting inflammatory cascades is considered a promising way to prevent knee osteoarthritis (OA) progression. In terms of down-regulating the expression of inducible nitric oxide synthase (iNOS), interleukin (IL)-6, and matrix metalloproteinases (MMPs), pre-treatment with the flavonoid baicalein reportedly protects articular chondrocytes against the cytotoxicity of IL-1ß. However, the benefits of post-treatment baicalein on osteoarthritic chondrocytes are not fully elucidated. METHODS: In this study, primary human chondrocytes were stimulated with IL-1ß prior to baicalein application to evaluate the therapeutic effect of post-treatment. RESULTS: Post-treatment baicalein alleviated cell death and partially restored mitochondrial viability, while the senescence-associated secretory phenotype was not improved in IL-1ß-stimulated chondrocytes. Post-treatment baicalein down-regulated the expressions of IL-1ß, tumor necrosis factor-alpha, MMP-3, MMP-9, and MMP-13 mRNA as well as the protein production in stimulated cells. Even so, the levels of these factors were relative higher than those in un-treated chondrocytes. Moreover, iNOS, IL-6, IL-8, and COL1A1 expressions were consistently high, and IL-10 protein synthesis steadily increased in IL-1ß-treated chondrocytes under baicalein treated status. Moreover, Western blot analyses showed that post-treatment baicalein suppressed nuclear factor kappa-light-chain-enhancer of activated B cells and p50 production while downstream cyclooxygenase-2 was still highly expressed. CONCLUSION: Baicalein post-treatment to osteoarthritic chondrocytes had a minor benefit to the homeostasis of cartilaginous extracellular matrix.

Intra-articular Injection of platelet-rich fibrin releasates in combination with bone marrow-derived mesenchymal stem cells in the treatment of articular cartilage defects: An in vivo study in rabbits.

The use of mesenchymal stem cells (MSCs), which can be differentiated into chondrocytes under specific conditions, has been proposed for the treatment of cartilage defects. Blood-derived platelet-rich fibrin releasate (PRFr), which is rich in growth factors and cytokines, may improve cartilage regeneration. In this study, the therapeutic effects of PRFr in combination with bone marrow-derived MSCs for articular cartilage regeneration were evaluated in a rabbit model. Critical osteochondral defects were surgically created in the femoral condyle of the rabbits, and 3 × 106 of MSCs, 0.8 mL of PRFr, or a combination of MSCs and PRFr were injected intra-articularly and one week after first administration. The animals were sacrificed 12 weeks postoperatively, and the regenerated cartilages were assessed by gross inspection and histological examination. No treatment-related adverse events were noted in any of the rabbits. The size of the defect decreased and the volume of regenerated cartilage increased in the medial femoral condyles of the MSCs + PRFr group. Relative to the MSCs or PRFr group, histological examination demonstrated that the MSCs + PRFr group had thicker hyaline-like cartilaginous tissue with normal glycosaminoglycan production. Grading scores revealed that MSCs + PRFr injection had better matrix, cell distribution, and surface indices than other groups. The results showed that intra-articular injections of MSCs + PRFr into the knee can reduce cartilage defects by regenerating hyaline-like cartilage without adverse events. This approach may provide an alternative method of autologous chondrocyte implantation to repair cartilage defects with an unlimited source of cells and releasate. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1536-1543, 2017.

Injectable and biodegradable composite bone filler composed of poly(propylene fumarate) and calcium phosphate ceramic for vertebral augmentation procedure: An in vivo porcine study.

Despite its common usage in vertebral augmentation procedures (VAPs), shortcomings of commercial polymethylmethacrylate (PMMA) still remain. Accordingly, injectable and biodegradable composite cements, which are composed of poly(propylene fumarate)/α-tricalcium/hydroxyapatite (PPF/α-TCP/HAP) and PPF/tetracalcium phosphate/dicalcium phosphate (PPF/TtCP/DCP), were developed. A porcine model was used and cylindrical holes in critical size were created at the center of the lateral cortex of vertebral bodies of the lumbar spine. A fixed volume of testing materials and PMMA were randomly injected into the defects. Results showed that both composite groups had a comparable radiolucency as PMMA but a significantly lower setting temperature. Histological inspections revealed new bone formation and remodeling along the border of the two composite cements. New bone substitution and irregular sclerotic bone mantles were found along the composite cements but not in the PMMA group. Radiological and histological changes were observed in the two composite groups and these modifications were diminished along the block boundaries. These findings imply gradual substitution of decomposed composite by new bone formation, which could not be found around the PMMA block. Comparing PPF/α-TCP/HAP with the PPF/TtCP/DCP cement block, smaller particles that were spreading out were observed in the TtCP/DCP group, which represents rapid degradability. In conclusion, the composite cements have advantages such as a low setting temperature, radio-opacity, biodegradability, and osteoconductivity. The injectable PPF/calcium phosphate ceramic composite has the potential to be used in VAPs. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2232-2243, 2017.

A self-reinforcing biodegradable implant made of poly(ɛ-caprolactone)/calcium phosphate ceramic composite for craniomaxillofacial fracture fixation.

PURPOSE: Biodegradable polymer fixators have been used widely in oral and maxillofacial surgery for fracture management. However, short-comings such as insufficient mechanical strength, inappropriate degradation time, lack of radiolucency, and foreign body reactions during bone remodeling remain. MATERIAL AND METHODS: In this study, calcium phosphate ceramic (CPC, including tricalcium phosphate [TCP] and tetracalcium phosphate/dicalcium phosphate [TTCP/DCP]) and poly(ε-caprolactone) (PCL) were used to fabricate biodegradable orthopedic fixation devices. RESULTS: Different weight ratios of CPC were added to PCL, and the results showed that the PCL/CPC composites had good radiopacity, mechanical properties, and biocompatibility. CPC was transformed into hydroxyapatite when the composites were immersed in simulated body fluid. The PCL/TTCP/DCP composite had a higher compressive strength relative to PCL/TCP after setting, and this self-reinforcing property contributed to the hydration of TTCP/DCP and formation of apatite crystals. Thus, PCL/TTCP/DCP screws were prepared for animal studies. No postoperative mortality or complications were noted 6 months postsurgery. Biodegradation of the PCL/TTCP/DCP screws and newly formed bony tissue around the degraded composites were shown on both micro-computed tomography and histology. No peri-implant bone resorption was noted. CONCLUSION: The self-reinforcing PCL/TTCP/DCP composite can be used to fabricate biodegradable fixators for fracture management in craniomaxillofacial fracture fixation.

Enhancement of biodegradation and osseointegration of poly(ε-caprolactone)/calcium phosphate ceramic composite screws for osteofixation using calcium sulfate.

Internal fixation devices, which can stabilize and realign fractured bone, are widely used in fracture management. In this paper, a biodegradable composite fixator, composed of poly(ε-caprolactone), calcium phosphate ceramic and calcium sulfate (PCL/CPC/CS), is developed. The composition of CS, which has a high dissolution rate, was expected to create a porous structure to improve osteofixation to the composite fixator. PCL, PCL/CPC, and PCL/CPC/CS samples were prepared and their physical properties were characterized in vitro. In vivo performance of the composite screws was verified in the distal femurs of rabbits. Results showed that the PCL/CPC/CS composite had a higher compressive strength (28.55 ± 3.32 MPa) in comparison with that of PCL (20.64 ± 1.81 MPa) (p < 0.05). A larger amount of apatite was formed on PCL/CPC/CS than on PCL/CPC, while no apatite was found on PCL after simulated body fluid immersion. In addition, PCL/CPC/CS composites also had a faster in vitro degradation rate (13.05 ± 3.42% in weight loss) relative to PCL (1.79 ± 0.23%) and PCL/CPC (4.32 ± 2.18%) (p < 0.001). In animal studies, PCL/CPC/CS screws showed a greater volume loss than that of PCL or PCL/CPC at 24 weeks post-implantation. Under micro-computerized tomography observation, animals with PCL/CPC/CS implants had better osseointegration in terms of the structural parameters of the distal metaphysis, including trabecular number, trabecular spacing, and connectivity density, than the PCL screw. This study reveals that the addition of CS accelerates the biodegradation and enhanced apatite formation of the PCL/CPC composite screw. This osteoconductive PCL/CPC/CS is a good candidate material for internal fixation devices.

Calcium phosphate cement delivering zoledronate decreases bone turnover rate and restores bone architecture in ovariectomized rats.

Patients sustaining bony fractures frequently require the application of bone graft substitutes to fill the bone defects. In the meantime, anti-osteoporosis drugs may be added in bone fillers to treat osteoporosis, especially in postmenopausal women and the elderly. The effects of zoledronate-impregnated calcium phosphate cement (ZLN/CPC) on ovariectomized (OVX) rats were evaluated. OVX rats were implanted with ZLN/CPC, containing 0.025 mg ZLN in the greater omentum. Afterward the clinical sign of toxicity was recorded for eight weeks. The rats were sacrificed and blood samples were collected for hematology and serum bone turnover markers analyses. The four limbs of the rats were harvested and micro-computer tomography (micro-CT) scanning and bone ash analyses were performed. No clinical toxicity was observed in the treated rats. Compared to the OVX rats, levels of bone resorption markers (fragments of C-telopeptides of type I collagen) and bone formation markers (alkaline phosphatase and osteocalcin) decreased significantly in the treated rats. Osteopontin, which mediates the anchoring of osteoclasts to the mineral matrix of bones, also decreased significantly. Micro-CT scanning and histologic examinations of the distal femoral metaphyses showed that the cancellous bone architectures were restored, with a concomitant decrease in bone porosity. The bone mineral content in the bone ashes also increased significantly. This study indicates that ZLN-impregnated CPC reduces bone turnover rate and restores bone architecture in OVX rats. CPC may be an appropriate carrier to deliver drugs to treat osteoporosis, and this approach may also reduce rates of post-dosing symptoms for intravenous ZLN delivery.