Interorgan communication in neurogenic heterotopic ossification: the role of brain-derived extracellular vesicles

Brain-derived extracellular vesicles participate in interorgan communication after traumatic brain injury by transporting pathogens to initiate secondary injury.Inflammasome-related proteins encapsulated in brain-derived extracellular vesicles can cross the blood‒brain barrier to reach distal tissues.These proteins initiate inflammatory dysfunction,such as neurogenic heterotopic ossification.This recurrent condition is highly debilitating to patients because of its relatively unknown pathogenesis and the lack of effective prophylactic intervention strategies.Accordingly,a rat model of neurogenic heterotopic ossification induced by combined traumatic brain injury and achillotenotomy was developed to address these two issues.Histological examination of the injured tendon revealed the coexistence of ectopic calcification and fibroblast pyroptosis.The relationships among brain-derived extracellular vesicles,fibroblast pyroptosis and ectopic calcification were further investigated in vitro and in vivo.Intravenous injection of the pyroptosis inhibitor Ac-YVAD-cmk reversed the development of neurogenic heterotopic ossification in vivo.The present work highlights the role of brain-derived extracellular vesicles in the pathogenesis of neurogenic heterotopic ossification and offers a potential strategy for preventing neurogenic heterotopic ossification after traumatic brain injury.

Elimination of methicillin‑resistant Staphylococcus aureus biofilms on titanium implants via photothermally‑triggered nitric oxide and immunotherapy for enhanced osseointegration

Background:Treatment of methicillin-resistant Staphylococcus aureus(MRSA)biofilm infections in implant placement surgery is limited by the lack of antimicrobial activity of titanium(Ti)implants.There is a need to explore more effective approaches for the treatment of MRSA biofilm infections.Methods:Herein,an interfacial functionalization strategy is proposed by the integration of mesoporous polydopamine nanoparticles(PDA),nitric oxide(NO)release donor sodium nitroprusside(SNP)and osteogenic growth peptide(OGP)onto Ti implants,denoted as Ti-PDA@SNP-OGP.The physical and chemical properties of Ti-PDA@SNP-OGP were assessed by scanning electron microscopy,X-ray photoelectron spectroscope,water contact angle,photothermal property and NO release behavior.The synergistic antibacterial effect and elimination of the MRSA biofilms were evaluated by 2′,7′-dichlorofluorescein diacetate probe,1-N-phenylnaphthylamine assay,adenosine triphosphate intensity,O-nitrophenyl-β-D-galactopyranoside hydrolysis activity,bicinchoninic acid leakage.Fluorescence staining,assays for alkaline phosphatase activity,collagen secretion and extracellular matrix mineralization,quantitative real‑time reverse transcription‑polymerase chain reaction,and enzyme-linked immunosorbent assay(ELISA)were used to evaluate the inflammatory response and osteogenic ability in bone marrow stromal cells(MSCs),RAW264.7 cells and their co-culture system.Giemsa staining,ELISA,micro-CT,hematoxylin and eosin,Masson's trichrome and immunohistochemistry staining were used to evaluate the eradication of MRSA biofilms,inhibition of inflammatory response,and promotion of osseointegration of Ti-PDA@SNP-OGP in vivo.Results:Ti-PDA@SNP-OGP displayed a synergistic photothermal and NO-dependent antibacterial effect against MRSA following near-infrared light(NIR)irradiation,and effectively eliminated the formed MRSA biofilms by inducing reactive oxygen species(ROS)-mediated oxidative stress,destroying bacterial membrane integrity and causing leakage of intracellular components(P<0.01).In vitro experiments revealed that Ti-PDA@SNP-OGP not only facilitated osteogenic differentiation of MSCs,but also promoted the polarization of pro-inflammatory M1 macrophages to the anti-inflammatory M2-phenotype(P<0.05 or P<0.01).The favorable osteo-immune microenvironment further facilitated osteogenesis of MSCs and the anti-inflammation of RAW264.7 cells via multiple paracrine signaling pathways(P<0.01).In vivo evaluation confirmed the aforementioned results and revealed that Ti-PDA@SNP-OGP induced ameliorative osseointegration in an MRSA-infected femoral defect implantation model(P<0.01).Conclusions:Ti-PDA@SNP-OGP is a promising multi-functional material for the high-efficient treatment of MRSA infections in implant replacement surgeries.

Bioengineered materials with selective antimicrobial toxicity in biomedicine

Fungi and bacteria afflict humans with innumerous pathogen-related infections and ailments.Most of the commonly employed microbicidal agents target commensal and pathogenic microorganisms without discrimination.To distinguish and fight the pathogenic species out of the microflora,novel antimicrobials have been developed that selectively target specific bacteria and fungi.The cell wall features and antimicrobial mechanisms that these microorganisms involved in are highlighted in the present review.This is followed by reviewing the design of antimicrobials that selectively combat a specific community of microbes including Gram-positive and Gram-negative bacterial strains as well as fungi.Finally,recent advances in the antimicrobial immunomodulation strategy that enables treating microorganism infections with high specificity are reviewed.These basic tenets will enable the avid reader to design novel approaches and compounds for antibacterial and antifungal applications.

Lysosomal destabilization:A missing link between pathological calcification and osteoarthritis

Calcification of cartilage by hydroxyapatite is a hallmark of osteoarthritis and its deposition strongly correlates with the severity of osteoarthritis.However,no effective strategies are available to date on the prevention of hydroxyapatite deposition within the osteoarthritic cartilage and its role in the pathogenesis of this degenerative condition is still controversial.Therefore,the present work aims at uncovering the pathogenic mechanism of intra-cartilaginous hydroxyapatite in osteoarthritis and developing feasible strategies to counter its detrimental effects.With the use of in vitro and in vivo models of osteoarthritis,hydroxyapatite crystallites deposited in the cartilage are found to be phagocytized by resident chondrocytes and processed by the lysosomes of those cells.This results in lysosomal membrane permeabilization(LMP)and release of cathepsin B(CTSB)into the cytosol.The cytosolic CTSB,in turn,activates NOD-like receptor protein-3(NLRP3)inflammasomes and subsequently instigates chondrocyte pyroptosis.Inhibition of LMP and CTSB in vivo are effective in managing the progression of osteoarthritis.The present work provides a conceptual therapeutic solution for the prevention of osteoarthritis via alleviation of lysosomal destabilization.

Silicified collagen scaffold induces semaphorin 3A secretion by sensory nerves to improve in-situ bone regeneration

Sensory nerves promote osteogenesis through the release of neuropeptides.However,the potential application and mechanism in which sensory nerves promote healing of bone defects in the presence of biomaterials remain elusive.The present study identified that new bone formation was more abundantly produced after implantation of silicified collagen scaffolds into defects created in the distal femur of rats.The wound sites were accompanied by extensive nerve innervation and angiogenesis.Sensory nerve dysfunction by capsaicin injection resulted in significant inhibition of silicon-induced osteogenesis in the aforementioned rodent model.Application of extracellular silicon in vitro induced axon outgrowth and increased expression of semaphorin 3 A(Sema3A)and semaphorin 4D(Sema4D)in the dorsal root ganglion(DRG),as detected by the upregulation of signaling molecules.Culture medium derived from silicon-stimulated DRG cells promoted proliferation and differentiation of bone marrow mesenchymal stem cells and endothelial progenitor cells.These effects were inhibited by the use of Sema3A neutralizing antibodies but not by Sema4D neutralizing antibodies.Knockdown of Sema3A in DRG blocked silicon-induced osteogenesis and angiogenesis almost completely in a femoral defect rat model,whereas overexpression of Sema3A promoted the silicon-induced phenomena.Activation of“mechanistic target of rapamycin”(mTOR)pathway and increase of Sema3A production were identified in the DRG of rats that were implanted with silicified collagen scaffolds.These findings support the role of silicon in inducing Sema3A production by sensory nerves,which,in turn,stimulates osteogenesis and angiogenesis.Taken together,silicon has therapeutic potential in orthopedic rehabilitation.

Polyphosphate-crosslinked collagen scaffolds for hemostasis and alveolar bone regeneration after tooth extraction

Post-extraction bleeding and alveolar bone resorption are the two frequently encountered complications after tooth extraction that result in poor healing and rehabilitation difficulties.The present study covalently bonded polyphosphate onto a collagen scaffold(P-CS)by crosslinking.The P-CS demonstrated improved hemostatic property in a healthy rat model and an anticoagulant-treated rat model.This improvement is attributed to the increase in hydrophilicity,increased thrombin generation,platelet activation and stimulation of the intrinsic coagulation pathway.In addition,the P-CS promoted the in-situ bone regeneration and alveolar ridge preservation in a rat alveolar bone defect model.The promotion is attributed to enhanced osteogenic differentiation of bone marrow stromal cells.Osteogenesis was improved by both polyphosphate and blood clots.Taken together,P-CS possesses favorable hemostasis and alveolar ridge preservation capability.It may be used as an effective treatment option for post-extraction bleeding and alveolar bone loss.Statement of significance:Collagen scaffold is commonly used for the treatment of post-extraction bleeding and alveolar bone loss after tooth extraction.However,its application is hampered by insufficient hemostatic and osteoinductive property.Crosslinking polyphosphate with collagen produces a modified collagen scaffold that possesses improved hemostatic performance and augmented bone regeneration potential.

Biomaterial scaffolds for clinical procedures in endodontic regeneration

Regenerative endodontic procedures have been rapidly evolving over the past two decades and are employed extensively in clinical endodontics.These procedures have been perceived as valuable adjuvants to conventional strategies in the treatment of necrotic immature permanent teeth that were deemed to have poor prognosis.As a component biological triad of tissue engineering(i.e.,stem cells,growth factors and scaffolds),biomaterial scaffolds have demonstrated clinical potential as an armamentarium in regenerative endodontic procedures and achieved remarkable advancements.The aim of the present review is to provide a broad overview of biomaterials employed for scaffolding in regenerative endodontics.The favorable properties and limitations of biomaterials organized in naturally derived,host-derived and synthetic material categories were discussed.Preclinical and clinical studies published over the past five years on the performance of biomaterial scaffolds,as well as current challenges and future perspectives for the application of biomaterials for scaffolding and clinical evaluation of biomaterial scaffolds in regenerative endodontic procedures were addressed in depth.

Regulatory mechanisms and regeneration strategies of the soft-hard tissue interface in the human periodontium

The soft-hard tissue interface of the human periodontium is responsible for periodontal homeostasis and is essential for normal oral activities.This softhard tissue interface is formed by the direct insertion of fibrous ligaments into the bone tissue.It differs from the unique four-layer structure of the fibrocartilage interface.This interface is formed by a combination of physical,chemical,and biological factors.The physiological functions of this interface are regulated by different signaling pathways.The unique structure of this soft-hard tissue interface has inspired scientists to construct biomimetic gradient structures.These biomimetic systems include nanofiber scaffolds,cell sheets,and hydrogels.Exploring methods to repair this soft-hard tissue interface can help solve clinically unresolved problems.The present review examines the structure of the soft-hard tissue interface of the periodontium and the factors that influence the development of this interface.Relevant regulatory pathways and biomimetic reconstruction methods are also presented to provide ideas for future research on interfacial tissue engineering.