Sr-HA scaffolds fabricated by SPS technology promote the repair of segmental bone defects.

BACKGROUND: Ideal bone defect repair scaffolds should be biodegradable, biocompatible, bioactive, porous, and provide adequate mechanical support. However, it is challenging to fabricate such an ideal bone repair scaffold. Previously, we showed that 5 wt.% strontium-doped hydroxyapatite (Sr-HA) scaffolds prepared by spark plasma sintering (SPS) technology exhibited good biocompatibility. Moreover, unlike pure hydroxyapatite (HA) scaffolds, HA scaffolds containing strontium (Sr) exhibited superior bioactivity, higher proliferation rate of BMSCs and MG-63 osteoblast cells, as well as enhanced BMSCs differentiation. METHODS: In this study, we prepared pure HA scaffolds and 5 wt.% strontium containing Sr-HA scaffolds by SPS technology without adhesive, ammonium bicarbonate as pore former. Subsequently, scanning electron microscope (SEM) and X-Ray diffraction (XRD) were used to characterize the properties of Sr-HA and HA scaffolds. The ability of the scaffolds to repair bone defects was evaluated using a critical-sized rabbit tibia-bone defect rabbit model. Thirty 3-month-old New Zealand white rabbits were randomly divided into three groups (blank control group, Sr-HA scaffolds implanted group and HA scaffolds implanted group) with 10 rabbits in each group. These rabbits are sacrificed after 8 weeks and 16 weeks of surgery, and the repair effects of each scaffold were evaluated with X-ray, micro-CT, and HE staining. The three-point bending test was employed to assess the mechanical property of repaired bones. RESULTS: XRD pattern indicated that Sr-HA and HA scaffolds possess a similar crystal structure after sintering, and that incorporation of strontium did not form impure phase. SEM showed that the porosity of Sr-HA and HA scaffolds was about 40 %. Universal Testing Machine tests showed that Sr-HA scaffolds had better compressive strength than HA scaffolds. Bone defect was obvious, and the fibrous tissue was formed in the bone defects of rabbits in the blank control group after 8 weeks of surgery. Sr-HA and HA scaffolds enhanced osteointegration of the host bone, and extensive woven bone was formed on the surface of the Sr-HA scaffolds. After 16 weeks, the bone strump became blunt and a small amount of callus was formed in the blank control group. Comparatively, the scaffolds were substantially degraded in the Sr-HA scaffolds implanted group while scaffolds shadows still were observed in the HA implanted group. Bone remodeling and cavity recanalization were completely developed in the Sr-HA scaffolds group. The compressive strength of repaired bone in the Sr-HA scaffolds implantation group was higher than that of HA scaffolds implantation group after 8 weeks and 16 weeks of surgery. CONCLUSIONS: Our results show that the Sr-HA composite scaffolds can effectively repair bone defects and have good biodegradable properties.

Proprotein convertase 1/3-mediated down-regulation of brain-derived neurotrophic factor in cortical neurons induced by oxygen-glucose deprivation.

Brain-derived neurotrophic factor (BDNF) has robust effects on synaptogenesis, neuronal differentiation and synaptic transmission and plasticity. The maturation of BDNF is a complex process. Proprotein convertase 1/3 (PC1/3) has a key role in the cleavage of protein precursors that are directed to regulated secretory pathways; however, it is not clear whether PC1/3 mediates the change in BDNF levels caused by ischemia. To clarify the role of PC1/3 in BDNF maturation in ischemic cortical neurons, primary cortical neurons from fetal rats were cultured in a humidified environment of 95% N2 and 5% CO2 in a glucose-free Dulbecco's modified Eagle's medium at 37°C for 3 hours. Enzyme-linked immunosorbent assays and western blotting showed that after oxygen-glucose deprivation, the secreted and intracellular levels of BDNF were significantly reduced and the intracellular level of PC1/3 was decreased. Transient transfection of cortical neurons with a PC1/3 overexpression plasmid followed by oxygen-glucose deprivation resulted in increased PC1/3 levels and increased BDNF levels. When levels of the BDNF precursor protein were reduced, the concentration of BDNF in the culture medium was increased. These results indicate that PC1/3 cleavage of BDNF is critical for the conversion of pro-BDNF in rat cortical neurons during ischemia. The study was approved by the Animal Ethics Committee of Wuhan University School of Basic Medical Sciences.

Unilateral and Bilateral Percutaneous Kyphoplasty for Thoracolumbar Osteoporotic Compression Fractures.

OBJECTIVE: To compare the efficacies of unilateral and bilateral percutaneous kyphoplasty (PKP) in the treatment of thoracolumbar osteoporotic compression fractures. STUDY DESIGN: Experimental study. PLACE AND DURATION OF STUDY: Department of Orthopedics, Hubei 672 Orthopedics Hospital of Integrated Chinese and Western Medicine, China, from November 2014 to January 2017. METHODOLOGY: One hundred and seventy-eight patients with single-level thoracolumbar osteoporotic compression fractures included in this study. These patients were randomly assigned to unilateral (n=83) and bilateral (n=95) PKP groups. The operation time, bone cement volume, number of X-ray views, preoperative and postoperative pain visual analogue scale scores (VAS), Oswestry Dysfunction Index (ODI), Cobb angle, and vertebral height in both groups were recorded. RESULTS: Operation time, bone cement volume and intraoperative number of X-ray views were significantly different between unilateral and bilateral PKP groups (29.8 ±2.7 vs. 31.5 ±3.9 minutes; 9.3 ±2.6 vs. 11.2 ±3.7 times; 3.1 ±0.7 vs. 3.5 ±1.2 ml, respectively, p <0.05). VAS scores and ODI in both groups were significantly different before and 24 hours, 3 months and 6 months after surgery. The heights of anterior and middle borders of vertebral body and Cobb angle in the two groups were significantly different before and after surgery (p <0.05). CONCLUSION: The short-term efficacy was identical between unilateral and bilateral PKP. The unilateral PKP is characterized by short operation time, low hospital cost, less number of X-ray views and less bone cement volume. The unilateral PKP shows a higher risk of re-fracture of adjacent vertebral body compared with the bilateral PKP.

MiR-375 Mediates Chondrocyte Metabolism and Oxidative Stress in Osteoarthritis Mouse Models through the JAK2/STAT3 Signaling Pathway.

OBJECTIVE: The aim of this work was to determine the effect of miR-375 on chondrocyte metabolism and oxidative stress in osteoarthritis (OA) mouse models through the JAK2/STAT3 signaling pathway. METHODS: Chondrocytes were divided into control, IL-1ß, IL-1ß + miR-375 mimic, IL-1ß + miR-375 inhibitor, IL-1ß + miR-NC (negative control), and IL-1ß + miR-375 inhibitor + siJAK2 groups. The chondrocyte proliferation was determined by MTT assay, the superoxide dismutase (SOD) and malondialdehyde (MDA) levels by corresponding kits, and the chondrocyte apoptosis by TUNEL staining. Furthermore, OA mouse models were divided into Sham, OA + miR-NC, and OA + miRNA-375 antagomir groups. The pathological changes were observed, and the expressions of miR-375 and the JAK2/STAT3 pathway were determined by qRT-PCR and Western blotting, respectively. RESULTS: IL-1ß-induced chondrocytes had significant increases in miR-375 and MDA, with decreased proliferation and SOD levels, as compared to the control group. Meanwhile, they also exhibited elevated apoptosis, with upregulations of ADAMTS-5 and MMP-13 and downregulations of COL2A1 and ACAN, as well as decreased p-JAK2/JAK2, p-STAT3/STAT3, and Bcl-2/Bax. However, these changes were significantly improved after transfection with miR-375 inhibitor, but transfection with miR-375 mimic resulted in severer exacerbation. Notably, the improvement of miR-375 inhibitor could be abolished by transfection with siJAK2. Furthermore, miR-375 antagomir significantly alleviated OA progression in OA mice in vivo. CONCLUSION: MiR-375 suppression enhanced the ability of chondrocyte to antagonize the oxidative stress and maintained the homeostasis of extracellular matrix metabolism to protect chondrocytes from OA via activation of the JAK2/STAT3 pathway, indicating that miR-375 is a potential molecular target for OA treatment.

Low serum concentrations of Irisin are associated with increased risk of hip fracture in Chinese older women.

OBJECTIVE: Irisin derived from muscle in response to exercise may be the molecular entity responsible for muscle wasting-osteoporosis connectivity in the elderly. The objective of the study was to determine whether serum Irisin (sIrisin) provides information on hip fracture prediction which were independent of bone mineral density (BMD) and the fracture risk assessment tool (FRAX) algorithm. METHODS: This study enrolled 160 older women (ages, 70-90y) with minimal trauma hip fractures (MTHFs) and 160 age-matched women without fracture serving as controls. Clinical features, BMD and bone turnover markers including sIrisin levels were measured after fracture within 2 days as baseline. RESULTS: sIrisin levels were significantly lower (361.5±140.0ng/mL vs 478.5±159.6ng/mL, P<0.001) in cases than controls. After multivariate analysis, sIrisin remained as an independent variable of BMD, which explained 17.8% of femoral neck BMD and 22.5% of lumbar spine BMD, respectively. The odds ratio (OR) of MTHFs comparing the lowest (<320.1ng/mL) to highest (>524.5ng/mL) quartiles was 1.95 (95% CI 1.23-3.79, P<0.05) for sIrisin. Adjustment for age, body mass index, time since menopause and exercise ≥30min/day yielded similar results, and BMD of femoral neck also did not change these associations. Taking FRAX score into account attenuated the association somewhat: OR of hip fracture was 1.81 (95% CI 1.26-3.49, P<0.05) in first versus fourth quartile of sIrisin. There was a negative gradient of risk by decreasing quartile in sIrisin. CONCLUSIONS: Low concentrations of sIrisin in older women were independently associated with increased risk of hip fractures when adjusted for BMD or FRAX score.

Construction of a plasmid for overexpression of human circadian gene period2 and its biological activity in osteosarcoma cells.

Beyond their established role in the mammalian circadian clock, recent studies have confirmed that the circadian genes have been implicated in tumor onset and progression. Currently, the biological effects of circadian genes on osteosarcoma cells' proliferation and migration are not well understood. Period2 (Per2) is one of the core circadian genes that act as master regulators of development and is frequently dysregulated in several cancers. However, the effects of human Per2 (hPer2) on the biological behavior of osteosarcoma cells are rarely reported. In the present study, to address the expression of hPer2 in osteosarcoma cells, the pEGFP-N1-hPer2 eukaryotic expression vector was constructed and transfected into cultured MG63 cells using Lipofectamine™ 2000. The overexpression of hPer2 in MG63 cells was verified by qRT-PCR and Western blotting, respectively. Finally, we investigated the effects of hPer2 protein overexpression on MG63 cells' viability, cycle, apoptosis, and invasive ability. In conclusion, the recombinant pEGFP-N1-hPer2 plasmid had been constructed successfully and expressed effectively in MG63 cells. Furthermore, results also showed that the viability, proliferation, and invasive abilities were suppressed, and the apoptosis was enhanced in MG63 cells. This preliminary study provides ground work for further research on the roles of circadian gene hPer2 in osteosarcoma cells MG63 and would offer promise for the development of novel therapeutic strategies in the treatment of osteosarcoma.

Doxorubicin Inhibits Proliferation of Osteosarcoma Cells Through Upregulation of the Notch Signaling Pathway.

Doxorubicin plays a major role in the treatment of osteosarcoma disorders. The Notch signaling pathway exerts various biological functions, including cell proliferation, differentiation, and apoptosis. In the present study, we investigated the effects of different doses of doxorubicin on proliferation and apoptosis of osteosarcoma cells with or without Notch signaling. Results found that cellular viability was downregulated while caspase 3 activity and expression were promoted in osteosarcoma cells following treatment with various doses of doxorubicin for 24, 48, and 72 h, and the effects showed a dose- and time-dependent manner. Furthermore, it was found that various doses of doxorubicin activated the Notch signaling pathway, shown by the elevated expression of Notch target genes NOTCH1, HEY1, HES1, AND HES5. It was further proved that, after small interfering RNA (siRNA)-mediated knockdown of Notch, the effects of doxorubicin on the viability and apoptosis of osteosarcoma cells were significantly reduced. It was indicated that doxorubicin treatment reduced the proliferation and promoted the apoptosis of osteosarcoma cells, and this effect was mediated by the Notch signaling pathway.

Research and application of absorbable screw in orthopedics: a clinical review comparing PDLLA screw with metal screw in patients with simple medial malleolus fracture.

OBJECTIVE: To observe the therapeutic effect of absorbable screw in medial malleolus fracture and discuss its clinical application in orthopedics. METHODS: A total of 129 patients with simple medial malleolus fracture were studied. Among them, 64 patients were treated with poly-D, L-lactic acid (PDLLA) absorbable screws, while the others were treated with metal screws. All the patients were followed up for 12-20 months (averaged 18.4 months) and the therapeutic effect was evaluated according to the American Orthopaedic Foot and Ankle Society clinical rating systems. RESULTS: In absorbable screw group, we obtained excellent and good results in 62 cases (96.88%); in steel screw group, 61 cases (93.85%) achieved excellent and good results. There was no significant difference between the two groups. CONCLUSION: In the treatment of malleolus fracture, absorbable screw can achieve the same result compared with metal screw fixation. Absorbable screw is preferred due to its advantages of safety, cleanliness and avoiding the removal procedure associated with metallic implants.

Clinical efficacy of artificial skin combined with vacuum sealing drainage in treating large-area skin defects.

OBJECTIVE: To observe the clinical efficacy of artificial skin combined with vacuum sealing drainage (VSD) in treating large-area skin defects. METHODS: Totally 18 patients with skin defects, treated with artificial skin combined with VSD from September 2008 to May 2009 in our hospital, were retrospectively analyzed in this study. There were 15 males and 3 females, aged 7-66 years, 34.3 years on average. Among them, 10 cases had skin laceration caused by traffic accidents (7 with open fractures), 1 mangled injury, 1 blast injury, 1 stump infection combined with skin defects after amputation and 5 heel ulcers. RESULTS: All skin grafts in 16 cases survived after being controlled by VSD for one time. For the rest 2 patients, one with skin avulsion on the left foot was given median thickness skin grafts after three times of VSD, the other with open fractures in the left tibia and fibula caused by a traffic accident was given free flap transplantation. Skin grafts of both patients survived, with normal color and rich blood supply. CONCLUSION: Skin grafting in conjunction with artificial skin and VSD is much more effective than traditional dressing treatment and worth wide application in clinic.

N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride nanoparticle as a novel delivery system for parathyroid hormone-related protein 1-34.

Chitosan (CS) and epoxy propyl trimethyl ammonium chloride (EPTAC) were used to prepare the water-soluble N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC). HTCC and sodium tripolyphosphate (TPP) were mixed to form HTCC nanoparticles based on ionic gelation. Parathyroid hormone-related protein 1-34 (PTHrP1-34) was incorporated into the HTCC nanoparticles. The particle size and morphology of nanoparticles were determined by transmission electron microscopy (TEM). HTCC/PTHrP1-34 nanoparticles were 100-180 nm in size and their encapsulation efficiency and loading capacity were related to HTCC concentration, TPP concentration and initial concentration of PTHrP1-34. Relatively optimum encapsulation efficiency (78.4%) and loading capacity (13.7%) of PTHrP1-34 is achieved, and the in vitro release profile of PTHrP1-34 from nanoparticles has an initial burst, which is followed up by a slow release phase. These studies showed that HTCC/PTHrP1-34 nanoparticles are suitable for the treatment of osteoporosis, because of their slow-continuous-release properties, and the relevant in vivo experiments and clinical trials should be further studied.

Mitotic arrest defective protein 2 expression abnormality and its clinicopathologic significance in human osteosarcoma.

Osteosarcoma is the most common primary malignancy of bone. Overexpression of mitotic arrest defective protein 2 (MAD2) is found in many human neoplasms, but its role in the oncogenesis of osteosarcoma is an untouched topic. The objective of this research was to observe the expression of MAD2 in human osteosarcoma and explore its clinicopathologic significance. MAD2 expression was analyzed in 48 primary osteosarcoma cases (19 osteoblastic osteosarcomas, 17 chondroblastic osteosarcomas and 12 fibroblastic osteosarcomas) using immunohistochemistry. A total of 20 normal bone specimens formed a control group. MAD2 was commonly overexpressed in human osteosarcoma. Immunopositivity was higher in tumors with lower differentiation and higher clinical stage. Increased expression of MAD2 was associated with earlier metastasis and poorer survival. Our findings provide evidence that MAD2 contributes to the pathogenesis and development of human osteosarcoma, Testing may have a clinical role in predicting prognosis, selecting appropriate chemotherapeutic strategies and providing novel strategies for osteosarcoma therapy.