Artemisinic acid attenuates osteoclast formation and titanium particle-induced osteolysis via inhibition of RANKL-induced ROS accumulation and MAPK and NF-κB signaling pathways.

Periprosthetic osteolysis (PPO) is the most common cause of joint arthroplasty failure. Its progression involves both biological and mechanical factors. Osteoclastogenesis induced by wear from debris-cell interactions, ultimately leading to excessive bone erosion, is considered the primary cause of PPO; therefore, targeting osteoclasts is a promising treatment approach. Currently available drugs have various side effects and limitations. Artemisinic acid (ArA) is a sesquiterpene isolated from the traditional herb Artemisia annua L. that has various pharmacological effects, such as antimalarial, anti-inflammatory, and antioxidant activities. Therefore, this study was aimed at investigating the effect of ArA on osteoclast formation and bone resorption function in vitro, as well as wear particle-induced osteolysis in vivo, and to explore its molecular mechanism of action. Here, we report that ArA inhibits RANKL-stimulated osteoclast formation and function. Mechanistically, ArA suppresses intracellular reactive oxygen species levels by activating the antioxidant response via nuclear factor erythroid-2-related factor 2 (Nrf2) pathway upregulation. It also inhibits the mitogen-activated kinases (MAPK) and nuclear factor-κB (NF-κB) pathways, as well as the transcription and expression of NFATc1 and c-Fos. In vivo experiments demonstrated that ArA reduces osteoclast formation and alleviates titanium particle-induced calvarial osteolysis. Collectively, our study highlights that ArA, with its osteoprotective and antioxidant effects, is a promising therapeutic agent for preventing and treating PPO and other osteoclast-mediated osteolytic diseases.

TiO2 nanotube topography enhances osteogenesis through filamentous actin and XB130-protein-mediated mechanotransduction.

TiO2 nanotube topography, as nanomechanical stimulation, can significantly promote osteogenesis and improve the osteointegration on the interface of implants and bone tissue. However, the underlying mechanism has not been fully elucidated. XB130 is a member of the actin filament-associated protein family and is involved in the regulation of cytoskeleton and tyrosine kinase-mediated signalling as an adaptor protein. Whether XB130 is involved in TiO2 nanotubes-induced osteogenic differentiation and how it functions in mechano-biochemical signalling transduction remain to be elucidated. In this study, the role of XB130 on TiO2 nanotube-induced osteogenesis and mechanotransduction was systematically investigated. TiO2 nanotube topography was fabricated via anodic oxidation and characterized. The osteogenic effect was significantly accelerated by the TiO2 nanotube surface in vitro and vivo. XB130 was significantly upregulated during this process. Moreover, XB130 overexpression significantly promoted osteogenic differentiation, whereas its knockdown inhibited it. Filamentous actin depolymerization could change the expression and distribution of XB130, thus affecting osteogenic differentiation. Mechanistically, XB130 could interact with Src and result in the activation of the downstream PI3K/Akt/GSK-3ß/ß-catenin pathway, which accounts for the regulation of osteogenesis. This study for the first time showed that the enhanced osteogenic effect of TiO2 nanotubes could be partly due to the filamentous actin and XB130 mediated mechano-biochemical signalling transduction, which might provide a reference for guiding the design and modification of prostheses to promote bone regeneration and osseointegration. STATEMENT OF SIGNIFICANCE: TiO2 nanotubes topography can regulate cytoskeletal rearrangement and thus promote osteogenic differentiation of BMSCs. However, how filamentous actin converts mechanical stimulus into biochemical activity remains unclear. XB130 is a member of actin filament-associated protein family and involves in the regulation of tyrosine kinase-mediated signalling. Therefore, we hypothesised that XB130 might bridge the mechano-biochemical signalling transduction during TiO2 nanotubes-induced osteogenic differentiation. For the first time, this study shows that TiO2 nanotubes enhance osteogenesis through filamentous actin and XB130 mediated mechanotransduction, which provides new theoretical basis for guiding the design and modification of prostheses to promote bone regeneration and osseointegration.

Mechanical overloading leads to chondrocyte degeneration and senescence via Zmpste24-mediated nuclear membrane instability.

Patients with OA and varus knees are subject to abnormal mechanical environment and objective of this study was to investigate the molecular mechanisms underlying chondrocyte senescence caused by mechanical overloading and the role of Zmpste24-mediated nuclear membrane instability in varus knees. Finite element analysis showed that anteromedial region of tibial plateau experienced the most mechanical stress in an osteoarthritis patient with a varus knee. Immunohistochemistry exhibited lower Zmpste24 expression and higher expression of senescence marker p21 in the anteromedial region. Animal experiments and cell-stretch models also demonstrated an inverse relationship between Zmpste24 and mechanically induced senescence. Zmpste24 overexpression rescued cartilage degeneration and senescence in vitro by scavenging ROS. In conclusion, anteromedial tibial plateau is exposed to abnormal stress in varus knees, downregulation of Zmpste24, and nuclear membrane stability may explain increased senescence in this region. Zmpste24 and nuclear membrane stability are potential targets for treating osteoarthritis caused by abnormal alignment.

Aspirin prevents estrogen deficiency-induced bone loss by inhibiting osteoclastogenesis and promoting osteogenesis.

BACKGROUND: Aspirin is a commonly used antipyretic, analgesic, and anti-inflammatory drug. Numerous researches have demonstrated that aspirin exerts multiple biological effects on bone metabolism. However, its spatiotemporal roles remain controversial according to the specific therapeutic doses used for different clinical conditions, and the detailed mechanisms have not been fully elucidated. Hence, in the present study, we aimed to identify the dual effects of different aspirin dosages on osteoclastic activity and osteoblastic bone formation in vitro and in vivo. METHODS: The effects of varying doses of aspirin on osteoclast and osteoblast differentiation were evaluated in vitro. The underlying molecular mechanisms were detected using quantitative real-time polymerase chain reaction, western blotting, and immunofluorescence techniques. An ovariectomized rat osteoporosis model was used to assess the bone-protective effects of aspirin in vivo. RESULTS: Aspirin dose-dependently suppressed RANKL-induced osteoclasts differentiation and bone resorption in vitro and reduced the expression of osteoclastic marker genes, including TRAP, cathepsin K, and CTR. Further molecular analysis revealed that aspirin impaired the RANKL-induced NF-κB and MAPK signaling pathways and prevented the nuclear translocation of the NF-κB p65 subunit. Low-dose aspirin promoted osteogenic differentiation, whereas these effects were attenuated when high-dose aspirin was administered. Both low and high doses of aspirin prevented bone loss in an ovariectomized rat osteoporosis model in vivo. CONCLUSION: Aspirin inhibits RANKL-induced osteoclastogenesis and promotes osteogenesis in a dual regulatory manner, thus preventing bone loss in vivo. These data indicate that aspirin has potential applications in the prevention and treatment of osteopenia.

Paxlovid accelerates cartilage degeneration and senescence through activating endoplasmic reticulum stress and interfering redox homeostasis.

BACKGROUND: The COVID-19 pandemic has become a huge threat to human health, infecting millions of people worldwide and causing enormous economic losses. Many novel small molecule drugs have been developed to treat patients with COVID-19, including Paxlovid, which block the synthesis of virus-related proteins and replication of viral RNA, respectively. Despite satisfactory clinical trial results, attention is now being paid to the long-term side effects of these antiviral drugs on the musculoskeletal system. To date, no study has reported the possible side effects, such as osteoarthritis, of Paxlovid. This study explored the effects of antiviral drug, Paxlovid, on chondrocyte proliferation and differentiation. METHODS: In this study, both in vitro and in vivo studies were performed to determine the effect of Paxlovid on chondrocyte degeneration and senescence. Furthermore, we explored the possible mechanism behind Paxlovid-induced acceleration of cartilage degeneration using transcriptome sequencing and related inhibitors were adopted to verify the downstream pathways behind such phenomenon. RESULTS: Paxlovid significantly inhibited chondrocyte extracellular matrix protein secretion. Additionally, Paxlovid significantly induced endoplasmic reticulum stress, oxidative stress, and downstream ferroptosis, thus accelerating the senescence and degeneration of chondrocytes. In vivo experiments showed that intraperitoneal injection of Paxlovid for 1 week exacerbated cartilage abrasion and accelerated the development of osteoarthritis in a mouse model. CONCLUSIONS: Paxlovid accelerated cartilage degeneration and osteoarthritis development, potentially by inducing endoplasmic reticulum stress and oxidative stress. Long-term follow-up is needed with special attention to the occurrence and development of osteoarthritis in patients treated with Paxlovid.

Use of a Gigli Saw as a Substitute Osteotomy Tool When Oscillating Saw Malfunctions Occur During Hip Arthroplasty.

OBJECTIVE: The oscillating saw has some inherent disadvantages, such as notch formation and blood splash. The objective is to introduce the Gigli saw as a substitute osteotomy tool when oscillating saw malfunctions occur during surgery. METHODS: During our retrospective study, 120 patients (120 hips) who underwent primary total hip arthroplasty (THA) because of femoral neck fracture, femoral head necrosis, developmental hip dysplasia (Crowe I), or primary osteoarthritis between October 2017 and April 2020 at our institute were included. Sixty patients (26 men and 34 women) with a mean age of 67.3 years (±15.1 years) underwent femoral neck osteotomy using a Gigli saw. The other 60 patients (32 men and 28 women) with a mean age of 64.4 years (±18.8 years) underwent femoral neck osteotomy using an oscillating saw. Intraoperative evaluations, including osteotomy time, osteotomy height, number of notch formations, and blood splash generation, were performed. Routine anteroposterior views of the pelvis and proximal femur were obtained for all patients after surgery. RESULTS: The mean osteotomy times were 26.60 ± 14.80 s and 31.80 ± 14.20 s with the oscillating saw and Gigli saw, respectively (t = 1.964, P = 0.0519). The mean osteotomy heights were 1.26 ± 0.22 cm and 1.20 ± 0.14 cm with the oscillating saw and Gigli saw, respectively (t = 1.782, P = 0.0773). The use of a Gigli saw did not result in bone notch formation or blood splash generation when multiple blood splashes were generated in the oscillating saw group. Postoperative radiographs showed no prostheses malposition in the Gigli saw and oscillating saw groups. CONCLUSION: The Gigli saw has various advantages and can be a substitute tool for femoral neck osteotomy during THA when oscillating saw malfunctions occur.

Use of Customized 3D-Printed Titanium Augment With Tantalum Trabecular Cup for Large Acetabular Bone Defects in Revision Total Hip Arthroplasty: A Midterm Follow-Up Study.

Aims: In revision total hip arthroplasty (THA), large acetabular bone defects pose challenges for surgeons. Recently, wide application of trabecular tantalum, which has outstanding biocompatibility and mechanical properties, and the development of three-dimensional (3D) printing have led to the introduction of new schemes for acetabular reconstruction. However, few studies have focused on the treatment of bone defects with customized 3D-printed titanium augments combined with tantalum trabecular cup. Thus, we aimed to evaluate the effect of this therapy in patients who underwent revision THAs. Patients and Methods: We included 23 patients with Paprosky type III acetabular bone defects who underwent revision THA between January 2013 and June 2019. The preoperative hip rotation center and functional score were compared with those at 2-7 years (average 4.7 years) postoperatively to evaluate the midterm prognosis of our treatment choice. Results: Postoperatively, the rotation centres of all hips were comparable with those of the contralateral hips. Hip function improved with average Harris Hip Score improved from 33.5 (22.7-40.2) to 86.1 (73.5-95.6) and average Oxford Hip Score improved from 8.3 (0-14) to 38.8 (35-48) during follow-up. One dislocation, which occurred due to extreme hip flexion within 6 weeks, was treated with closed reduction, and no recurrent dislocation occurred. No nerve injury, infection, aseptic loosening, or osteolysis were observed and no re-revision was performed in any patient. Conclusion: Satisfactory midterm outcomes were obtained with 3D-printed titanium augment combined with tantalum cup for the treatment of acetabular defects in revision THA. Changes in the Harris Hip Score and Oxford Hip Score suggested a significant improvement in hip function.

TiO2 Nanotubes Promote Osteogenic Differentiation Through Regulation of Yap and Piezo1.

Surface modification of titanium has been a hot topic to promote bone integration between implants and bone tissue. Titanium dioxide nanotubes fabricated on the surface of titanium by anodic oxidation have been a mature scheme that has shown to promote osteogenesis in vitro. However, mechanisms behind such a phenomenon remain elusive. In this study, we verified the enhanced osteogenesis of BMSCs on nanotopographic titanium in vitro and proved its effect in vivo by constructing a bone defect model in rats. In addition, the role of the mechanosensitive molecule Yap is studied in this research by the application of the Yap inhibitor verteporfin and knockdown/overexpression of Yap in MC3T3-E1 cells. Piezo1 is a mechanosensitive ion channel discovered in recent years and found to be elemental in bone metabolism. In our study, we preliminarily figured out the regulatory relationship between Yap and Piezo1 and proved Piezo1 as a downstream effector of Yap and nanotube-stimulated osteogenesis. In conclusion, this research proved that nanotopography promoted osteogenesis by increasing nuclear localization of Yap and activating the expression of Piezo1 downstream.

DNA-Based Daisy Chain Rotaxane Nanocomposite Hydrogels as Dual-Programmable Dynamic Scaffolds for Stem Cell Adhesion.

Interlocked DNA nanostructures perform programmable movements in nanoscales such as sliding, contraction, and expansion. However, utilizing nanoscaled interlocked movements to regulate the functions of larger length scaled matrix and developing their applications has not yet been reported. Herein we describe the assembly of DNA-based daisy chain rotaxane nanostructure (DNA-DCR) composed of two hollow DNA nanostructures as macrocycles, two interlocked axles and two triangular prism-shaped DNA structures as stoppers, in which three mechanical states─fixed extended state (FES), sliding state (SS), and fixed contracted state (FCS)─are characterized by using toehold-mediated strand displacement reaction (SDR). The DNA-DCRs are further used as nanocomposites and introduced into hydrogel matrix to produce interlocked hydrogels, which shows modulable stiffness by elongating the interlocked axles to regulate the hydrogel swelling with hybridization chain reaction (HCR) treatment. Then the DCR-hydrogels are employed as dynamic biointerfaces for human mesenchymal stem cells (hMSCs) adhesion studies. First, hMSCs showed lower cell density on bare DCR-hydrogel treated with HCR-initiated swelling for stiffness decreasing. Second, the cell adhesion ligand (RGD) modified DNA-DCRs are constructed for hydrogel functionalization. DCR(RGD) hydrogel endows the mobility of RGDs by switching the mechanical states of DNA-DCR. HMSCs showed increased cell density on DCRSS(RGD) hydrogel than on DCRFCS(RGD) hydrogel. Therefore, our DNA-DCR nanocomposite hydrogel exhibit dual-programmable performances including swelling adjustment and offering sliding for incorporated ligands, which can be both utilized as dynamic scaffolds for regulating the stem cell adhesion. The dual-programmable cross-scale regulation from interlocked DNA nanostructures to hydrogel matrix was achieved, demonstrating a new pathway of DNA-based materials.

Debridement without bone grafting prevents osteolytic lesions progression in revision THAs with prosthesis revised.

Background: Bone defects in revision total hip arthroplasties (rTHAs) caused by osteolysis are routinely treated with autografts or allografts, despite their various disadvantages. Currently, little is known about the prognosis of ungrafted cavities with complete debridement following prosthetic revision in rTHAs with component loosening, as few reports have focused on the application of debridement without bone grafting in osteolytic lesions that do not compromise structural stability in revision THAs with revised components. Methods: In this study, 48 patients receiving rTHAs with components revised for aseptic loosening with osteolysis between 2015 and 2019 were included. Anteroposterior and lateral radiographs of hips before and after revision surgery and last follow-up were compared to measure whether the size of the debrided osteolytic cavity without bone graft had changed. Results: In total, 48 patients with 59 osteolytic lesions were enrolled. The mean follow-up period was 3.33 years (range 2-6 years). None of the 59 cavities had progressed at the last follow-up, and 11 (18.6%) regressed. Two patients underwent re-revision according to dislocation during follow-up. Conclusion: In rTHAs with revised components, osteolytic lesions that do not influence structural stability could be debrided without grafting to avoid the disadvantages of grafting. Debridement and component revision are sufficient to prevent the progression of osteolytic lesions during surgery, without having adverse effects on the short-to mid-term prognosis.

Cyclic Mechanical Strain Regulates Osteoblastic Differentiation of Mesenchymal Stem Cells on TiO2 Nanotubes Through GCN5 and Wnt/ß-Catenin.

Bone marrow mesenchymal stem cells (BMSCs) play a critical role in bone formation and are extremely sensitive to external mechanical stimuli. Mechanical signals can regulate the biological behavior of cells on the surface of titanium-related prostheses and inducing osteogenic differentiation of BMSCs, which provides the integration of host bone and prosthesis benefits. But the mechanism is still unclear. In this study, BMSCs planted on the surface of TiO2 nanotubes were subjected to cyclic mechanical stress, and the related mechanisms were explored. The results of alkaline phosphatase staining, real-time PCR, and Western blot showed that cyclic mechanical stress can regulate the expression level of osteogenic differentiation markers in BMSCs on the surface of TiO2 nanotubes through Wnt/ß-catenin. As an important member of the histone acetyltransferase family, GCN5 exerted regulatory effects on receiving mechanical signals. The results of the ChIP assay indicated that GCN5 could activate the Wnt promoter region. Hence, we concluded that the osteogenic differentiation ability of BMSCs on the surface of TiO2 nanotubes was enhanced under the stimulation of cyclic mechanical stress, and GCN5 mediated this process through Wnt/ß-catenin.

A novel efficient and precise technique for removing acetabular osteophytes in patients undergoing total hip arthroplasty: the SH-9Hospital acetabular edge file.

BACKGROUND: Total hip arthroplasty (THA) is frequently performed in patients with end-stage hip disease. Periacetabular osteophytes are common during THA; however, these osteophytes should be removed intraoperatively to avoid potential impingement between osteophytes and femoral prostheses and decrease dislocation risk. There are no current standard procedures or surgical technique criteria to remove these osteophytes. Osteophytes around the acetabulum are usually removed with an osteotome, yet this presents certain disadvantages. Hence, this study aimed to introduce a novel and more efficient technique than the aforementioned one, the SH-9Hospital acetabular edge file. METHODS: Fifty-four patients (54 hips) who underwent primary THA using osteotome and the SH-9Hospital acetabular edge file to remove periacetabular osteophytes intraoperatively were retrospectively studied. Clinical and radiographic data were obtained for all patients intra- and postoperatively. RESULTS: The mean osteophyte removal time was 274.6±102.7 s and 51.3±21.1 s in the osteotome and SH-9Hospital acetabular edge file groups, respectively. Intraoperative images and postoperative radiographs showed that acetabular osteophytes were removed thoroughly and precisely by the acetabular edge file and that there was no iatrogenic injury and prostheses malposition in both groups. CONCLUSIONS: The SH-9Hospital acetabular edge file was a novel, efficient, highly precise, and repeatable method for removing periacetabular osteophytes in patients undergoing total hip arthroplasty.

A novel and efficient surgical knotting technique for high-tension closures.

BACKGROUND: The closure of high-tension incisions without any assistance can be difficult and challenging for surgeons. A common practice is to fix the first knot with a clamp and then tie a reverse locking knot; however, this practice has certain disadvantages. The aim of this study was to introduce a novel and efficient surgical knotting technique with various advantages. METHODS: The two knotting methods used in this study were the absorbable braided suture where the first suture was fixed with a clamp (with assistance) and the SH-9Hospital knotting technique (without assistance) applied on the smooth surface of a cylinder. Mechanical testing was performed using a universal material testing machine. The load-elongation curve and ultimate tensile load (UTL) were recorded. RESULTS: The mean knotting time was 36.40±1.50 s (range, 32-41 s) and 24.80±1.16 s (range, 21-28 s) in the clamp and SH-9Hosptial groups, respectively. The mean UTL was 120.8±10.14 N (range, 81.11-136.55 N)and 126.5±6.29 N (range, 104.88-139.56 N) in the clamp and SH-9Hospital groups, respectively. The knot strength of the SH-9Hospital technique was not inferior to traditional clinical practice. CONCLUSIONS: The SH-9Hospital knotting technique was a secure, convenient, and efficient method for high-tension closure.

Use of a novel Screen-Enrich-Combine(-biomaterials) Circulating System to fill a 3D-printed open Ti6Al4V frame with mesenchymal stem cells/ß-tricalcium phosphate to repair complex anatomical bone defects in load-bearing areas.

BACKGROUND: Repairing complex anatomical load-bearing bone defects is difficult because it requires the restoration of the load-bearing function, reconstructing the anatomical shape, and repair by regenerated bone. We previously developed a Screen-Enrich-Combine(-biomaterials) Circulating System (SECCS) for rapid intraoperative enrichment of autologous bone marrow mesenchymal stem cells (MSCs) to enhance the osteogenic ability of porous bone substitutes. In this study, we prepared a 3D-printed Ti6A14V macroporous frame matching the defect shape to provide early load-bearing support and evaluated the efficacy of filling the frame with SECCS-processed MSCs/beta tricalcium phosphate (ß-TCP) for long-term bone growth. METHODS: Fifteen 2-year-old goats were involved in this study, and the lateral part of their distal femur was removed by an electric saw and was fitted by a matching electron beam melting technology-prepared (EBM) Ti6Al4V frame. Three types of frames, filled with nothing, pure porous ß-TCP, or SECCS-processed MSCs/ß-TCP, were fixed onto the defect site. Repair efficacy was evaluated by X-ray radiography, computed tomography (CT), histology, and histomorphometry. RESULTS: In the basic regular hexagon printing unit, the combined side width (w) and the inscribed circle diameter (d) determines the printing frame's mechanical strength. The compressive load was significantly higher for w=1.9 mm, d=4.4 mm than for w=1.7 mm, d=4.0 mm or w=2.0 mm, d=5.0 mm (P<0.05). The EBM-prepared Ti6Al4V defect-matched frame was well maintained 9 months after implantation. The MSCs successfully adhered to the wall of the porous ß-TCP in the SECCS-processed group and had spread fully in the test samples. Each goat in the MSCs/ß-TCP-the filled group, had approximately 31,321.7±22,554.7 of MSCs and a larger area of new bone growth inside the frame than the control and blank areas groups. CONCLUSIONS: Filling the 3D-printed Ti6Al4V large-aperture frame with osteogenic materials achieved biological reconstruction over a larger area of regenerated bone to repair complex anatomical weight-bearing bone defects under the condition of early frame-supported load bearing. MSCs/ß-TCP prepared by SECCS can be used as a filling material for this type of bone defect to obtain more efficacious bone repair.

Exposure to high levels of magnesium disrupts bone mineralization in vitro and in vivo.

BACKGROUND: The removal of permanent internal fixation devices by secondary surgery could be avoided if these devices were made of degradable magnesium and magnesium alloys. Before such implants can be used clinically, however, the biological effect of magnesium exposure on surrounding bone must be evaluated. Previous studies have focused on bone formation; few have examined the effects of magnesium on the bone quality that affect many biomechanical properties. METHODS: Using bone quality parameters, we analyzed in vivo changes in bone properties and biomechanics after exposure to locally high levels of magnesium. RESULTS: Local bone mineralization was significantly disrupted following exposure to a porous rod of pure magnesium. Normal crystal formation and crystallinity were inhibited and the mineral-to-matrix ratio decreased. These results were consistent with those of in vitro experiments, in which high levels of magnesium inhibited mineral deposition by mesenchymal stem cells (MSCs) but increased alkaline phosphatase (ALP) expression. The same mineralization inhibition was observed around magnesium implants via micro-computerized tomography (micro-CT) and von Kossa staining. Such reduced bone quality around degrading magnesium rods could negatively impact bone biomechanics. CONCLUSIONS: This study showed that exposure to the local high magnesium levels that arise from rapidly degrading magnesium devices may significantly disrupt bone mineralization and negatively impact bone biomechanics.

F-actin Regulates Osteoblastic Differentiation of Mesenchymal Stem Cells on TiO2 Nanotubes Through MKL1 and YAP/TAZ.

Titanium and titanium alloys are widely used in orthopedic implants. Modifying the nanotopography provides a new strategy to improve osseointegration of titanium substrates. Filamentous actin (F-actin) polymerization, as a mechanical loading structure, is generally considered to be involved in cell migration, endocytosis, cell division, and cell shape maintenance. Whether F-actin is involved and how it functions in nanotube-induced osteogenic differentiation of mesenchymal stem cells (MSCs) remain to be elucidated. In this study, we fabricated TiO2 nanotubes on the surface of a titanium substrate by anodic oxidation and characterized their features by scanning electron microscopy (SEM), X-ray energy dispersive analysis (EDS), and atomic force microscopy (AFM). Alkaline phosphatase (ALP) staining, Western blotting, qRT-PCR, and immunofluorescence staining were performed to explore the osteogenic potential, the level of F-actin, and the expression of MKL1 and YAP/TAZ. Our results showed that the inner diameter and roughness of TiO2 nanotubes increased with the increase of the anodic oxidation voltage from 30 to 70 V, while their height was 2 µm consistently. Further, the larger the tube diameter, the stronger the ability of TiO2 nanotubes to promote osteogenic differentiation of MSCs. Inhibiting F-actin polymerization by Cyto D inhibited osteogenic differentiation of MSCs as well as the expression of proteins contained in focal adhesion complexes such as vinculin (VCL) and focal adhesion kinase (FAK). In contrast, after Jasp treatment, polymerization of F-actin enhanced the expression of RhoA and transcription factors YAP/TAZ. Based on these data, we concluded that TiO2 nanotubes facilitated the osteogenic differentiation of MSCs, and this ability was enhanced with the increasing diameter of the nanotubes within a certain range (30-70 V). F-actin mediated this process through MKL1 and YAP/TAZ.

Quercetin inhibits macrophage polarization through the p-38α/ß signalling pathway and regulates OPG/RANKL balance in a mouse skull model.

Aseptic loosening caused by wear particles is a common complication after total hip arthroplasty. We investigated the effect of the quercetin on wear particle-mediated macrophage polarization, inflammatory response and osteolysis. In vitro, we verified that Ti particles promoted the differentiation of RAW264.7 cells into M1 macrophages through p-38α/ß signalling pathway by using flow cytometry, immunofluorescence assay and small interfering p-38α/ß RNA. We used enzyme-linked immunosorbent assays to confirm that the protein expression of M1 macrophages increased in the presence of Ti particles and that these pro-inflammatory factors further regulated the imbalance of OPG/RANKL and promoted the differentiation of osteoclasts. However, this could be suppressed, and the protein expression of M2 macrophages was increased by the presence of the quercetin. In vivo, we revealed similar results in the mouse skull by µ-CT, H&E staining, immunohistochemistry and immunofluorescence assay. We obtained samples from patients with osteolytic tissue. Immunofluorescence analysis indicated that most of the macrophages surrounding the wear particles were M1 macrophages and that pro-inflammatory factors were released. Titanium particle-mediated M1 macrophage polarization, which caused the release of pro-inflammatory factors through the p-38α/ß signalling pathway, regulated OPG/RANKL balance. Macrophage polarization is expected to become a new clinical drug therapeutic target.

LncRNA expression profiles and the negative regulation of lncRNA-NOMMUT037835.2 in osteoclastogenesis.

Bone is a rigid and dynamic organ that continuously undergoes remodeling and repair. The balance between osteoblastic bone formation and osteoclastic bone resorption is essential for normal bone homeostasis. Osteoclasts are giant multinucleated cells derived from the monocyte/macrophage hematopoietic lineage and are regulated by various cytokines. Long non-coding (lnc) RNAs are known to regulate many biological processes in the skeletal system in both normal and diseased states; however, the lncRNA-mediated regulation of osteoclastogenesis has not been extensively studied. Hence, in the present study, we performed microarray analysis of lncRNAs expressed during different stages of osteoclast differentiation and fusion. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed the biological functions of target genes of lncRNAs that were specifically up- or downregulated at the different stages. Microarray and bioinformatic prediction results were used to generate co-expression networks of lncRNAs-mRNAs and lncRNAs-transcription factors. Based on the analysis, we identified one lncRNA, NONMMUT037835.2, which plays an important role during osteoclastogenesis. Upregulation of lncRNA-NONMMUT037835.2 inhibited osteoclastic differentiation, whereas downregulation of lncRNA-NONMMUT037835.2 promoted osteoclast formation and fusion. Our study also indicated that lncRNA-NOMMUT037835.2 might regulated osteoclastogenesis through negatively regulating RANK expression and inhibiting NF-κB/MAPK signaling pathway. Our results lead to a better understanding of the molecular mechanisms and provided a theoretical basis for developing therapeutic agents for diseases related to dysregulation of bone homeostasis.

Clinical Applications of 3-Dimensional Printing Technology in Hip Joint.

Three-dimensional (3D) printing is a digital rapid prototyping technology based on a discrete and heap-forming principle. We identified 53 articles from PubMed by searching "Hip" and "Printing, Three-Dimensional"; 52 of the articles were published from 2015 onwards and were, therefore, initially considered and discussed. Clinical application of the 3D printing technique in the hip joint mainly includes three aspects: a 3D-printed bony 1:1 scale model, a custom prosthesis, and patient-specific instruments (PSI). Compared with 2-dimensional image, the shape of bone can be obtained more directly from a 1:1 scale model, which may be beneficial for preoperative evaluation and surgical planning. Custom prostheses can be devised on the basis of radiological images, to not only eliminate the fissure between the prosthesis and the patient's bone but also potentially resulting in the 3D-printed prosthesis functioning better. As an alternative support to intraoperative computer navigation, PSI can anchor to a specially appointed position on the patient's bone to make accurate bone cuts during surgery following a precise design preoperatively. The 3D printing technique could improve the surgeon's efficiency in the operating room, shorten operative times, and reduce exposure to radiation. Well known for its customization, 3D printing technology presents new potential for treating complex hip joint disease.

Mechanical strain promotes osteogenic differentiation of mesenchymal stem cells on TiO2 nanotubes substrate.

Previous studies demonstrated cycle mechanical strain induced osteogenic differentiation of MSCs. But in general, MSCs are typically seeded on a flexible membrane or within a soft matrix. TiO2 nanotubes substrate topography plays a critical role in promoting the MSCs response and affects MSCs fate. Titanium implants surface modified by TiO2 nanotubes topography provides the opportunity to improve osseointegration by additionally regulating the MSCs fate. Titanium is one of most commonly used materials in the orthopedics and can undergo elastic deformation under certain mechanical stress. Therefore, for clinic trails, it is necessary to investigate the effect of mechanical strain on osteogenesis of MSCs on TiO2 nanotubes modified titanium substrate. But until now, there has been no research focused on the relationship between mechanical strain and osteogenesis of MSCs on the TiO2 nanotubes topography substrate. Here, we firstly applied the mechanical stress to the TiO2 nanotubes modified titanium specimen to investigate the effects of mechanical strain on the biological behaviors of MSCs. Our present study showed that mechanical strain promoted cell proliferation, spreading and increased vinculin expression of MSCs on the TiO2 nanotubes substrate. Additionally, mechanical strain enhanced the ALP activity and osteogenesis genes expression such as Runx2, BSP, ALP, OPN and OCN. Our results preliminarily demonstrated that mechanical strain enhanced the osteogenic differentiation of MSCs through the FAK-Erk1/2-Runx2 pathway on the TiO2 nanotubes substrate.