Reversing the imbalance in bone homeostasis via sustained release of SIRT-1 agonist to promote bone healing under osteoporotic condition

The imbalance of bone homeostasis is the root cause of osteoporosis.However current therapeutic approaches mainly focus on either anabolic or catabolic pathways,which often fail to turn the imbalanced bone metabolism around.Herein we reported that a SIRT-1 agonist mediated molecular therapeutic strategy to reverse the imbalance in bone homeostasis by simultaneously regulating osteogenesis and osteoclastogenesis via locally sustained release of SRT2104 from mineral coated acellular matrix microparticles.Immobilization of SRT2104 on mineral coating(MAM/SRT)harnessing their electrostatic interactions resulted in sustained release of SIRT-1 agonist for over 30 days.MAM/SRT not only enhanced osteogenic differentiation and mineralization,but also attenuated the formation and function of excessive osteoclasts via integrating multiple vital upstream signals(β-catenin,FoxOs,Runx2,NFATc1,etc.)in vitro.Osteoporosis animal model also validated that it accelerated osteoporotic bone healing and improved osseointegration of the surrounding bone.Overall,our work proposes a promising strategy to treat osteoporotic bone defects by reversing the imbalance in bone homeostasis using designated small molecule drug delivery systems.

Role of Cu element in biomedical metal alloy design

Biomedical metals are widely used as implant materials in the human or animal body to repair organs and restore function, such as heart valves, meninges, peritoneum and artificial organs.Alloying element affects the microstructure, mechanical property, corrosion resistance and wear resistance, but also influences the antibacterial and biological activity.Recently, antibacterial metal alloys have shown great potential as a new kind of biomedical materials, in which Cu has been widely used as antibacterial agent element.In addition, biodegradable metal alloys, including magnesium alloy and zinc alloy, also have attracted much attention worldwide.Cu was also used as alloying element to adjust the degradation rate.Thus, the role of Cu in the alloy design will be very important for the development of new alloy.In this paper, we summarized the recent research results on the Cu-containing metal alloy for biomedical application and hoped that this review would give more suggestions for the further development of biomedical metal alloy.

Epimedium-Derived Flavonoids Modulate the Balance between Osteogenic Differentiation and Adipogenic Differentiation in Bone Marrow Stromal Cells of Ovariectomized Rats via Wnt/β-Catenin Signal Pathway Activation

Objective： To observe the function of wnt/β-catenin signal pathway on the process that epimedium-derived flavonoids （EFs） regulate the balance between osteogenic differentiation and adipogenic differentiation in bone marrow stromal ceils of ovariectomized rats, and to provide an experimental evidence for the mechanism of EFs on treating postmenopausal osteoporosis. Methods： Bone marrow stromal cells from ovariectomized rats were separated and cultivated in the condition of osteoinductive medium or liquid medium for 15 days. Low- （1 μg/mL）, medium- （10 μg/mL） and high- （100 μg/mL） dose EFs were administrated correspondingly. Alkaline phosphatase （ALP） staining, ALP activity determination, oil red O staining and real- time polymerese chain reaction （RT-PCR） were used to determine the effect of EFs on osteogenic differentiation and adipogenic differentiation in bone marrow stromal cells of ovariectomized rats. Moreover, in order to explore the mechanism of EFs on osteogenic differentiation and adipogenic differentiation in bone marrow stromal cells of ovariectomized rats, Dickkopf-related protein 1 （DKK1） was used in the medium group. Enzyme linked immunosorbent assay （ELISA） and RT-PCR were used to determine mRNA levels of 13-catenin, low density lipoprotein receptor-related protein 5 （LRP5） and T cell factor （TCF） protein, known as wnt/β-catenin signal pathway related factors. Results： EFs increased mRNA expression levels of ALP and early osteoblast differentiation factors, such as runt-related transcription factor 2 （Runx2）, osteocaicin and collagen I, and decreased mRNA expression levels of fat generation factors, such as peroxisome proliferator activated receptor gamma 2 （PPAR r/-2） and CCAAT enhancer-binding protein-α （C/EBP α） in a dose-dependent manner. While osteobiast differentiation factors were down-regulated, fat generation factors were up-regulated when DKK1 was applied. Also EFs up-regulated mRNA expression levels of β-catenin, LRP5 and TCF protein which could be blocked by DKK1. Conclusion： EFs regulate the balance between osteogenic differentiation and adipogenic differentiation in bone marrow stromal cells of ovariectomized rats by activating wnt/13-catenin signal pathway, which may be an important molecular mechanism of EFs on treatinq DostmenoDausal osteoDorosis.

Glucan HBP-A Increase Type Ⅱ Collagen Expression of Chondrocytes in Vitro and Tissue Engineered Cartilage in Vivo

Objective：Although chondroprotective activities have been documented for polysaccharides,the potential target of different polysaccharide may differ.The study was aimed to explore the effect of glucan HBP-A in chondrocyte monolayer culture and chondrocytes-alginate hydrogel constructs in vivo,especially on the expression of type Ⅱ collagen.Methods：Chondrocytes isolated from rabbit articular cartilage were cultured and verified by immunocytochemical staining of type Ⅱ collagen.Chondrocyte viability was assessed after being treated with HBP-A in different concentrations.Morphological status of chondrocytes-alginate hydrogel constructs in vitro was observed by scanning electron microscope（SEM）.The constructs were treated with HBP-A and then injected to nude mice subcutaneously.Six weeks after transplantation,the specimens were observed through transmission electron microscopy（TEM）.The mRNA expressions of disintegrin and metalloproteinase with thrombospondin motifs 5（ADAMTs-5）,aggrecan and type Ⅱ collagen in both monolayer culture and constructs were determined by real time polymerase chain reaction（PCR）.The expression of typeⅡ collagen and matrix metalloproteinases-3（MMP-3） in chondrocyte monolayer culture was also tested through Western blot and enzyme linked immunosorbent assay（ELISA）,respectively.Results：MMP-3 secretion and ADAMTs-5 mRNA expression in vitro were inhibited by HBP-A at 0.3 mg/mL concentration.In morphological study,there were significant appearance of collagen in those constructs treated by HBP-A.Accordingly,in both chondrocyte monolayer culture and chondrocytes-alginate hydrogel constructs,the expression of type Ⅱcollagen was increased significantly in HBP-A group when compared with control group（P〈0.001）.Conclusions：The study documented that the potential pharmacological target of glucan HBP-A in chondrocytes monolayer culture and tissue engineered cartilage in vivo may be concerned with the inhibition of catabolic enzymes MMP-3,ADAMTs-5,and increasing of type Ⅱ collagen expression.

Biocorrosion properties of Ti–3Cu alloy in F ion-containing solution and acidic solution and biocompatibility

Ti–3Cu alloy has shown low melting point and strong antibacterial properties against S.aureus and E.coli and thus has potential application as dental materials and orthopedic application.In this paper, the corrosion properties of Ti–3Cu alloy in five kinds of simulated solutions were investigated in comparison with cp-Ti(commercially pure titanium) by electrochemical technology and immersion experiment.Electrochemical results have demonstrated that Ti–3Cu alloy exhibited much nobler corrosion potential, lower corrosion current density and high corrosion resistance than cp-Ti in all solutions, especially in saliva-pH6.8+0.2 F and saliva-pH3.5, indicating that Ti–3Cu alloy has much better anticorrosion properties than cpTi.Immersion results have shown that Ti ion and Cu ion were released from Ti–3Cu, especially in saliva-pH6.8+0.2 F and saliva-pH3.5 solutions.Both electrochemical data and immersion results have indicated that high corrosion rate and high metal ion release rate were detected in F ion-containing solution and low-pH solution, displaying that F^- and low pH had much strong aggressive attack to cp-Ti and Ti–3Cu alloy.The corroded surface morphology was observed by scanning electron microscopy(SEM), and the roughness was tested in the end.The good corrosion resistance of antibacterial Ti–3Cu alloy suggests its great potential as a long-term biomedical application.

Excavating bioactivities of nanozyme to remodel microenvironment for protecting chondrocytes and delaying osteoarthritis

Osteoarthritis(OA)is the main cause of disability in the elderly.Effective intervention in the early and middle stage of osteoarthritis can greatly prevent or slow down the development of the disease,and reduce the probability of joint replacement.However,there is to date no effective intervention for early and middle-stage OA.OA microenvironment mainly destroys the balance of oxidative stress,extracellular matrix synthesis and degradation of chondrocytes under the joint action of biological and mechanical factors.Herein,hollow Prussian blue nanozymes(HPBzymes)were designed via a modified hydrothermal template-free method.The aim of this study was to investigate the effects of HPBzymes on chondrocytes and the progression of OA.The intrinsic bioactivities of HPBzymes were excavated in vitro and in vivo,remodeling microenvironment for significantly protecting chondrocytes and delaying the progression of traumatic OA by inhibiting reactive oxygen species(ROS)and Rac1/nuclear factor kappa-B(NF-κB)signaling in a rat model.HPBzyme significantly diminished interleukin(IL)-1β-stimulated inflammation,extracellular matrix degradation,and apoptosis of human chondrocytes.HPBzyme attenuated the expression of Rac1 and the ROS levels and prevented the release and nuclear translocation of NF-κB.Deeply digging the intrinsic bioactivities of nanozyme with single component to remodel microenvironment is an effective strategy for ROS-associated chronic diseases.This study reveals that excavating the bioactivities of nanomedicine deserves attention for diagnosis and treatment of severe diseases.

Hyaluronic acid facilitates bone repair effects of calcium phosphate cement by accelerating osteogenic expression

Calcium phosphate cements(CPC)are widely anticipated to be an optimum bone repair substitute due to its satisfied biocompatibility and degradability,suitable to be used in minimally invasive treatment of bone defects.However the clinical application of CPC is still not satisfied by its poor cohesiveness and mechanical properties,in particular its osteoinductivity.Hyaluronic acid reinforced calcium phosphate cements(HA/CPC)showed extroadinary potential not only enhancing the compressive strength of the cements but also significantly increasing its osteoinductivity.In our study,the compressive strength of HA/CPC increased significantly when the cement was added 1%hyaluronic acid(denoted as 1-HA/CPC).In the meantime,hyaluronic acid obviously promoted ALP activity,osteogenic related protein and mRNA expression of hBMSCs(human bone marrow mesenchymal stem cells)in vitro,cement group of HA/CPC with 4%hyaluronic acid adding(denoted as 4-HA/CPC)showed optimal enhancement in hBMSCs differentiation.After being implanted in rat tibial defects,4-HA/CPC group exhibited better bone repair ability and bone growth promoting factors,comparing to pure CPC and 1-HA/CPC groups.The underlying biological mechanism of this stimulation for HA/CPC may be on account of higher osteogenic promoting factors secretion and osteogenic genes expression with hyaluronic acid incorporation.These results indicate that hyaluronic acid is a highly anticipated additive to improve physicochemical properties and osteoinductivity performance of CPCs for minimally invasive healing of bone defects.

ALD-induced TiO_(2)/Ag nanofilm for rapid surface photodynamic ion sterilization

The daily life of people in the intelligent age is inseparable from electronic device,and a number of bacteria on touch screens are increasingly threatening the health of users.Herein,a photocatalytic TiO_(2)/Ag thin film was synthesized on a glass by atomic layer deposition and subsequent in situ reduction.Ultraviolet-visible(UV-Vis)spectra showed that this film can harvest the simulated solar light more efficiently than that of pristine TiO_(2).The antibacterial tests in vitro showed that the antibacterial efficiency of the TiO_(2)/Ag film against S.aureus and E.coli was 98.2%and 98.6%,under visible light irradiation for 5 min.The underlying mechanism was that the in-situ reduction of Ag on the surface of TiO_(2)reduced the bandgap of TiO_(2)from 3.44 to 2.61 eV due to the formation of Schottky heterojunction at the interface between TiO_(2)and Ag.Thus,TiO_(2)/Ag can generate more reactive oxygen species for bacterial inactivation on the surface of electronic screens.More importantly,the TiO_(2)/Ag film had great biocompatibility with/without light irradiation.The platform not only provides a more convenient choice for the traditional antibacterial mode but also has limitless possibilities for application in the field of billions of touch screens.

Effect of cyclic mechanical loading on immunoinflammatory microenvironment in biofabricating hydroxyapatite scaffold for bone regeneration

It has been proven that the mechanical microenvironment can impact the differentiation of mesenchymal stem cells(MSCs).However,the effect of mechanical stimuli in biofabricating hydroxyapatite scaffolds on the inflammatory response of MSCs remains unclear.This study aimed to investigate the effect of mechanical loading on the inflammatory response of MSCs seeded on scaffolds.Cyclic mechanical loading was applied to biofabricate the cell-scaffold composite for 15 min/day over 7,14,or 21 days.At the predetermined time points,culture supernatant was collected for inflammatory mediator detection,and gene expression was analyzed by qRT-PCR.The results showed that the expression of inflammatory mediators(IL1B and IL8)was downregulated(p<0.05)and the expression of ALP(p<0.01)and COL1A1(p<0.05)was upregulated under mechanical loading.The cell-scaffold composites biofabricated with or without mechanical loading were freeze-dried to prepare extracellular matrix-based scaffolds(ECM-based scaffolds).Murine macrophages were seeded on the ECM-based scaffolds to evaluate their polarization.The ECM-based scaffolds that were biofabricated with mechanical loading before freeze-drying enhanced the expression of M2 polarization-related biomarkers(Arginase 1 and Mrc1,p<0.05)of macrophages in vitro and increased bone volume/total volume ratio in vivo.Overall,these findings demonstrated that mechanical loading could dually modulate the inflammatory responses and osteogenic differentiation of MSCs.Besides,the ECM-based scaffolds that were biofabricated with mechanical loading before freeze-drying facilitated the M2 polarization of macrophages in vitro and bone regeneration in vivo.Mechanical loading may be a promising biofabrication strategy for bone biomaterials.

A single-cell transcriptome of mesenchymal stromal cells to fabricate bioactive hydroxyapatite materials for bone regeneration

The osteogenic microenvironment of bone-repairing materials plays a key role in accelerating bone regeneration but remains incompletely defined,which significantly limits the application of such bioactive materials.Here,the transcriptional landscapes of different osteogenic microenvironments,including three-dimensional(3D)hydroxyapatite(HA)scaffolds and osteogenic medium(OM),for mesenchymal stromal cells(MSCs)in vitro were mapped at single-cell resolution.Our findings suggested that an osteogenic process reminiscent of endochondral ossification occurred in HA scaffolds through sequential activation of osteogenic-related signaling pathways,along with inflammation and angiogenesis,but inhibition of adipogenesis and fibrosis.Moreover,we revealed the mechanism during OM-mediated osteogenesis involves the ZBTB16 and WNT signaling pathways.Heterogeneity of MSCs was also demonstrated.In vitro ossification of LRRC75A+MSCs was shown to have better utilization of WNT-related ossification process,and PCDH10+MSCs with superiority in hydroxyapatite-related osteogenic process.These findings provided further understanding of the cellular activity modulated by OM conditions and HA scaffolds,providing new insights for the improvement of osteogenic biomaterials.This atlas provides a blueprint for research on MSC heterogeneity and the osteogenic microenvironment of HA scaffolds and a database reference for the application of bioactive materials for bone regeneration.

Strontium modulates osteogenic activity of bone cement composed of bioactive borosilicate glass particles by activating Wnt/β-catenin signaling pathway

There is a need for synthetic grafts to reconstruct large bone defects using minimal invasive surgery.Our previous study showed that incorporation of Sr into bioactive borate glass cement enhanced the osteogenic capacity in vivo.However,the amount of Sr in the cement to provide an optimal combination of physicochemical properties and capacity to stimulate bone regeneration and the underlying molecular mechanism of this stimulation is yet to be determined.In this study,bone cements composed of bioactive borosilicate glass particles substituted with varying amounts of Sr(0 mol%to 12 mol%SrO)were created and evaluated in vitro and in vivo.The setting time of the cement increased with Sr substitution of the glass.Upon immersion in PBS,the cement degraded and converted more slowly to HA(hydroxyapatite)with increasing Sr substitution.The released Sr2+modulated the proliferation,differentiation,and mineralization of hBMSCs(human bone marrow mesenchymal stem cells)in vitro.Osteogenic characteristics were optimally enhanced with cement(designated BG6Sr)composed of particles substituted with 6mol%SrO.When implanted in rabbit femoral condyle defects,BG6Sr cement supported better peri-implant bone formation and bone-implant contact,comparing to cements substituted with 0mol%or 9mol%SrO.The underlying mechanism is involved in the activation of Wnt/β-catenin signaling pathway in osteogenic differentiation of hBMSCs.These results indicate that BG6Sr cement has a promising combination of physicochemical properties and biological performance for minimally invasive healing of bone defects.

Improvement in antibacterial ability and cell cytotoxicity of Ti-Cu alloy by anodic oxidation

Ti-Cu alloy has potential to be used in plastic surgery and dental implants due to its strong antibacterialproperties,high strength and good corrosion resistance.In this paper,Ti-5Cu was anodic-oxidized to enhance the surface compatibility.The influence of the oxidation on the corrosion resistance,antibacterial properties and biological properties was investigated.X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)results showed that a double-layer oxide coating with dense inner layer and porous outside layer was formed on Ti-Cu sample.The oxide coating consisted mainly of TiO2,CuzO and small amount of CuO,improved the corrosion resistance of Ti-Cu alloy by one order of magnitude due to the formation of the dense oxide inner layer,but high Cu ion release was detected.The plate count results showed that the antibac-terial activity of Ti-Cu sample was improved to≥99%due to the comprehensive function of CuO and Cu_(2)O in the coating and Cu^(2+)release.Cell test results showed that thecoating exhibited good cell compatibility,the porous sur-face structure improved the adhesion of cells,and Cu ion release promoted the cell proliferation.

Corrigendum to“Strontium modulates osteogenic activity of bone cement composed of bioactive borosilicate glass particles by activating Wnt/β-catenin signaling pathway”[Bioact.Mater.5(2020)334-347]

The authors regret that the printed version of the above article contained a number of errors which were not identified during the proofing stage.The correct and final version follows.The authors would like to apologies for any inconvenience caused.The authors regret:1.“…and the underlying molecular mechanism of this simulation is yet to be determined”,Page 335,needs to be corrected to“and the underlying molecular mechanism of this stimulation is yet to be determined”.

A novel biomedical titanium alloy with high antibacterial property and low elastic modulus

β-type titanium alloys have attracted much attention as implant materials because of their low elastic modulus and high strength,which is closer to human bones and can avoid the problem of stress fielding and extend the lifetime of prosthetics.However,other issues,such as the infection or inflammation postimplantation,still trouble the titanium alloy's clinical application.In this paper,we developed a novel nearβ-titanium alloy(Ti-13Nb-13Zr-13Ag,TNZA)with low elastic modulus and strong antibacterial ability by the addition of Ag element followed by proper microstructure controlling,which could reduce the stress shielding and bacterial infections simultaneously.The microstructure,mechanical properties,corrosion resistance,antibacterial properties and cell toxicity were studied using SEM,electrochemical testing,mechanical test and cell tests.The results have demonstrated that TNZA alloy exhibited an elastic modulus of 75-87 GPa and a strong antibacterial ability(up to 98%reduction)and good biocompatibility.Moreover,it was also shown that this alloy's corrosion resistance was better than that of Ti-13Nb-13Zr.All the results suggested that Ti-13Nb-13Zr-13Ag might be a competitive biomedical titanium alloy.

3D printed silk-gelatin hydrogel scaffold with different porous structure and cell seeding strategy for cartilage regeneration

Hydrogel scaffolds are attractive for tissue defect repair and reorganization because of their human tissue-like characteristics.However,most hydrogels offer limited cell growth and tissue formation ability due to their submicron-or nano-sized gel networks,which restrict the supply of oxygen,nutrients and inhibit the proliferation and differentiation of encapsulated cells.In recent years,3D printed hydrogels have shown great potential to overcome this problem by introducing macro-pores within scaffolds.In this study,we fabricated a macroporous hydrogel scaffold through horseradish peroxidase(HRP)-mediated crosslinking of silk fibroin(SF)and tyramine-substituted gelatin(GT)by extrusion-based low-temperature 3D printing.Through physicochemical characterization,we found that this hydrogel has excellent structural stability,suitable mechanical properties,and an adjustable degradation rate,thus satisfying the requirements for cartilage reconstruction.Cell suspension and aggregate seeding methods were developed to assess the inoculation efficiency of the hydrogel.Moreover,the chondrogenic differentiation of stem cells was explored.Stem cells in the hydrogel differentiated into hyaline cartilage when the cell aggregate seeding method was used and into fibrocartilage when the cell suspension was used.Finally,the effect of the hydrogel and stem cells were investigated in a rabbit cartilage defect model.After implantation for 12 and 16 weeks,histological evaluation of the sections was performed.We found that the enzymatic cross-linked and methanol treatment SF5GT15 hydrogel combined with cell aggregates promoted articular cartilage regeneration.In summary,this 3D printed macroporous SF-GT hydrogel combined with stem cell aggregates possesses excellent potential for application in cartilage tissue repair and regeneration.