Age-related secretion of grancalcin by macrophages induces skeletal stem/progenitor cell senescence during fracture healing

Skeletal stem/progenitor cell(SSPC)senescence is a major cause of decreased bone regenerative potential with aging,but the causes of SSPC senescence remain unclear.In this study,we revealed that macrophages in calluses secrete prosenescent factors,including grancalcin(GCA),during aging,which triggers SSPC senescence and impairs fracture healing.Local injection of human rGCA in young mice induced SSPC senescence and delayed fracture repair.Genetic deletion of Gca in monocytes/macrophages was sufficient to rejuvenate fracture repair in aged mice and alleviate SSPC senescence.Mechanistically,GCA binds to the plexin-B2 receptor and activates Arg2-mediated mitochondrial dysfunction,resulting in cellular senescence.Depletion of Plxnb2 in SSPCs impaired fracture healing.Administration of GCA-neutralizing antibody enhanced fracture healing in aged mice.Thus,our study revealed that senescent macrophages within calluses secrete GCA to trigger SSPC secondary senescence,and GCA neutralization represents a promising therapy for nonunion or delayed union in elderly individuals.

Facile and rapid fabrication of a novel 3D-printable,visible light-crosslinkable and bioactive polythiourethane for large-to-massive rotator cuff tendon repair

Facile and rapid 3D fabrication of strong,bioactive materials can address challenges that impede repair of large-to-massive rotator cuff tears including personalized grafts,limited mechanical support,and inadequate tissue regeneration.Herein,we developed a facile and rapid methodology that generates visible light-crosslinkable polythiourethane(PHT)pre-polymer resin(~30 min at room temperature),yielding 3D-printable scaffolds with tendon-like mechanical attributes capable of delivering tenogenic bioactive factors.Ex vivo characterization confirmed successful fabrication,robust human supraspinatus tendon(SST)-like tensile properties(strength:23 MPa,modulus:459 MPa,at least 10,000 physiological loading cycles without failure),excellent suture retention(8.62-fold lower than acellular dermal matrix(ADM)-based clinical graft),slow degradation,and controlled release of fibroblast growth factor-2(FGF-2)and transforming growth factor-β3(TGF-β3).In vitro studies showed cytocompatibility and growth factor-mediated tenogenic-like differentiation of mesenchymal stem cells.In vivo studies demonstrated biocompatibility(3-week mouse subcutaneous implantation)and ability of growth factor-containing scaffolds to notably regenerate at least 1-cm of tendon with native-like biomechanical attributes as uninjured shoulder(8-week,large-to-massive 1-cm gap rabbit rotator cuff injury).This study demonstrates use of a 3D-printable,strong,and bioactive material to provide mechanical support and pro-regenerative cues for challenging injuries such as large-to-massive rotator cuff tears.

Engineering an extracellular matrix-functionalized,load-bearing tendon substitute for effective repair of large-to-massive tendon defects

A significant clinical challenge in large-to-massive rotator cuff tendon injuries is the need for sustaining high mechanical demands despite limited tissue regeneration,which often results in clinical repair failure with high retear rates and long-term functional deficiencies.To address this,an innovative tendon substitute named“BioTenoForce”is engineered,which uses(i)tendon extracellular matrix(tECM)’s rich biocomplexity for tendon-specific regeneration and(ii)a mechanically robust,slow degradation polyurethane elastomer to mimic native tendon’s physical attributes for sustaining long-term shoulder movement.Comprehensive assessments revealed outstanding performance of BioTenoForce,characterized by robust core-shell interfacial bonding,human rotator cuff tendon-like mechanical properties,excellent suture retention,biocompatibility,and tendon differentiation of human adipose-derived stem cells.Importantly,BioTenoForce,when used as an interpositional tendon substitute,demonstrated successful integration with regenerative tissue,exhibiting remarkable efficacy in repairing large-to-massive tendon injuries in two animal models.Noteworthy outcomes include durable repair and sustained functionality with no observed breakage/rupture,accelerated recovery of rat gait performance,and>1 cm rabbit tendon regeneration with native tendon-like biomechanical attributes.The regenerated tissues showed tendon-like,wavy,aligned matrix structure,which starkly contrasts with the typical disorganized scar tissue observed after tendon injury,and was strongly correlated with tissue stiffness.Our simple yet versatile approach offers a dual-pronged,broadly applicable strategy that overcomes the limitations of poor regeneration and stringent biomechanical requirements,particularly essential for substantial defects in tendon and other load-bearing tissues.

Large animal models of cardiac ischemia-reperfusion injury:Where are we now?

Large animal models of cardiac ischemia-reperfusion are critical for evaluation of the efficacy of cardioprotective interventions prior to clinical translation.Nonetheless,current cardioprotective strategies/interventions formulated in preclinical cardiovascular research are often limited to small animal models,which are not transferable or reproducible in large animal models due to different factors such as:(i)complex and varied features of human ischemic cardiac disease(ICD),which are challenging to mimic in animal models,(ii)significant differences in surgical techniques applied,and(iii)differences in cardiovascular anatomy and physiology between small versus large animals.This article highlights the advantages and disadvantages of different large animal models of preclinical cardiac ischemic reperfusion injury(IRI),as well as the different methods used to induce and assess IRI,and the obstacles faced in using large animals for translational research in the settings of cardiac IR.

4D bioprinting of programmed dynamic tissues

Setting time as the fourth dimension,4D printing allows us to construct dynamic structures that can change their shape,property,or functionality over time under stimuli,leading to a wave of innovations in various fields.Recently,4D printing of smart biomaterials,biological components,and living cells into dynamic living 3D constructs with 4D effects has led to an exciting field of 4D bioprinting.4D bioprinting has gained increasing attention and is being applied to create programmed and dynamic cell-laden constructs such as bone,cartilage,and vasculature.This review presents an overview on 4D bioprinting for engineering dynamic tissues and organs,followed by a discussion on the approaches,bioprinting technologies,smart biomaterials and smart design,bioink requirements,and applications.While much progress has been achieved,4D bioprinting as a complex process is facing challenges that need to be addressed by transdisciplinary strategies to unleash the full potential of this advanced biofabrication technology.Finally,we present future perspectives on the rapidly evolving field of 4D bioprinting,in view of its potential,increasingly important roles in the development of advanced dynamic tissues for basic research,pharmaceutics,and regenerative medicine.

Macrophage-derived extracellular vesicles regulate skeletal stem/progenitor Cell lineage fate and bone deterioration in obesity

Obesity-induced chronic inflammation exacerbates multiple types of tissue/organ deterioration and stem cell dysfunction;however,the effects on skeletal tissue and the underlying mechanisms are still unclear.Here,we show that obesity triggers changes in the microRNA profile of macrophage-secreted extracellular vesicles,leading to a switch in skeletal stem/progenitor cell(SSPC)differentiation between osteoblasts and adipocytes and bone deterioration.Bone marrow macrophage(BMM)-secreted extracellular vesicles(BMM-EVs)from obese mice induced bone deterioration(decreased bone volume,bone microstructural deterioration,and increased adipocyte numbers)when administered to lean mice.Conversely,BMM-EVs from lean mice rejuvenated bone deterioration in obese recipients.We further screened the differentially expressed microRNAs in obese BMM-EVs and found that among the candidates,miR-140(with the function of promoting adipogenesis)and miR-378a(with the function of enhancing osteogenesis)coordinately determine SSPC fate of osteogenic and adipogenic differentiation by targeting the Pparα-Abca1 axis.BMM miR-140 conditional knockout mice showed resistance to obesity-induced bone deterioration,while miR-140 overexpression in SSPCs led to low bone mass and marrow adiposity in lean mice.BMM miR-378a conditional depletion in mice led to obesity-like bone deterioration.More importantly,we used an SSPC-specific targeting aptamer to precisely deliver miR-378a-3p-overloaded BMM-EVs to SSPCs via an aptamer-engineered extracellular vesicle delivery system,and this approach rescued bone deterioration in obese mice.Thus,our study reveals the critical role of BMMs in mediating obesity-induced bone deterioration by transporting selective extracellular-vesicle microRNAs into SSPCs and controlling SSPC fate.

Engineering microparticles based on solidified stem cell secretome with an augmented pro-angiogenic factor portfolio for therapeutic angiogenesis

Tissue (re)vascularization strategies face various challenges, as therapeutic cells do not survive long enough in situ, while the administration of pro-angiogenic factors is hampered by fast clearance and insufficient ability to emulate complex spatiotemporal signaling. Here, we propose to address these limitations by engineering a functional biomaterial capable of capturing and concentrating the pro-angiogenic activities of mesenchymal stem cells (MSCs). In particular, dextran sulfate, a high molecular weight sulfated glucose polymer, supplemented to MSC cul-tures, interacts with MSC-derived extracellular matrix (ECM) components and facilitates their co-assembly and accumulation in the pericellular space. Upon decellularization, the resulting dextran sulfate-ECM hybrid material can be processed into MIcroparticles of SOlidified Secretome (MIPSOS). The insoluble format of MIPSOS protects protein components from degradation, while facilitating their sustained release. Proteomic analysis demonstrates that MIPSOS are highly enriched in pro-angiogenic factors, resulting in an enhanced pro-angiogenic bioactivity when compared to naïve MSC-derived ECM (cECM). Consequently, intravital microscopy of full-thickness skin wounds treated with MIPSOS demonstrates accelerated revascularization and healing, far superior to the ther-apeutic potential of cECM. Hence, the microparticle-based solidified stem cell secretome provides a promising platform to address major limitations of current therapeutic angiogenesis approaches.

The application of patient-derived induced pluripotent stem cells for modeling and treatment of Alzheimer’s disease

Alzheimer’s disease(AD)is the most prevalent age-related neurodegenerative disease which is mainly caused by aggregated protein plaques in degenerating neurons of the brain.These aggregated protein plaques are mainly consisting of amyloidβ(Aβ)fibrils and neurofibrillary tangles(NFTs)of phosphorylated tau protein.Even though the transgenic murine models can recapitulate some of the AD phenotypes,they are not the human cell models of AD.Recent breakthrough in somatic cell reprogramming made it available to use induced pluripotent stem cells(i PSCs)for patientspecific disease modeling and autologous transplantation therapy.Human i PSCs provide alternative ways to obtain specific human brain cells of AD patients to study the molecular mechanisms and therapeutic approaches for familial and sporadic forms of AD.After differentiation into neuronal cells,i PSCs have enabled the investigation of the complex aetiology and timescale over which AD develops in human brain.Here,we first go over the pathological process of and transgenic models of AD.Then we discuss the application of i PSC for disease model and cell transplantation.At last the challenges and future applications of i PSCs for AD will be summarized to propose cell-based approaches for the treatment of this devastating disorder.

Stem cell-derived hepatocyte therapy using versatile biomimetic nanozyme incorporated nanofiber-reinforced decellularized extracellular matrix hydrogels for the treatment of acute liver failure

Reactive oxygen species(ROS)-associated oxidative stress,inflammation storm,and massive hepatocyte necrosis are the typical manifestations of acute liver failure(ALF),therefore specific therapeutic interventions are essential for the devastating disease.Here,we developed a platform consisting of versatile biomimetic copper oxide nanozymes(Cu NZs)-loaded PLGA nanofibers(Cu NZs@PLGA nanofibers)and decellularized extracellular matrix(dECM)hydrogels for delivery of human adipose-derived mesenchymal stem/stromal cells-derived hepatocyte-like cells(hADMSCs-derived HLCs)(HLCs/Cu NZs@fiber/dECM).Cu NZs@PLGA nanofibers could conspicuously scavenge excessive ROS at the early stage of ALF,and reduce the massive accumulation of pro-inflammatory cytokines,herein efficiently preventing the deterioration of hepatocytes necrosis.Moreover,Cu NZs@PLGA nanofibers also exhibited a cytoprotection effect on the transplanted HLCs.Meanwhile,HLCs with hepatic-specific biofunctions and anti-inflammatory activity acted as a promising alternative cell source for ALF therapy.The dECM hydrogels further provided the desirable 3D environment and favorably improved the hepatic functions of HLCs.In addition,the pro-angiogenesis activity of Cu NZs@PLGA nanofibers also facilitated the integration of the whole implant with the host liver.Hence,HLCs/Cu NZs@fiber/dECM performed excellent synergistic therapeutic efficacy on ALF mice.This strategy using Cu NZs@PLGA nanofiber-reinforced dECM hydrogels for HLCs in situ delivery is a promising approach for ALF therapy and shows great potential for clinical translation.

“Slow walk”mimetic tensile loading maintains human meniscus tissue resident progenitor cells homeostasis in photocrosslinked gelatin hydrogel

Meniscus,the cushion in knee joint,is a load-bearing tissue that transfers mechanical forces to extracellular matrix(ECM)and tissue resident cells.The mechanoresponse of human tissue resident stem/progenitor cells in meniscus(hMeSPCs)is significant to tissue homeostasis and regeneration but is not well understood.This study reports that a mild cyclic tensile loading regimen of~1800 loads/day on hMeSPCs seeded in 3-dimensional(3D)photocrosslinked gelatin methacryloyl(GelMA)hydrogel is critical in maintaining cellular homeostasis.Experimentally,a“slow walk”biomimetic cyclic loading regimen(10%tensile strain,0.5 Hz,1 h/day,up to 15 days)is applied to hMeSPCs encapsulated in GelMA hydrogel with a magnetic force-controlled loading actuator.The loading significantly increases cell differentiation and fibrocartilage-like ECM deposition without affecting cell viability.Transcriptomic analysis reveals 332 mechanoresponsive genes,clustered into cell senescence,mechanical sensitivity,and ECM dynamics,associated with interleukins,integrins,and collagens/matrix metalloproteinase pathways.The cell-GelMA constructs show active ECM remodeling,traced using a green fluorescence tagged(GFT)-GelMA hydrogel.Loading enhances nascent pericellular matrix production by the encapsulated hMeSPCs,which gradually compensates for the hydrogel loss in the cultures.These findings demonstrate the strong tissue-forming ability of hMeSPCs,and the importance of mechanical factors in maintaining meniscus homeostasis.

机械敏感蛋白PC1调控破骨细胞及骨吸收的作用机制

Mechanical loading is required for bone homeostasis,but the underlying mechanism is still unclear.Our previous studies revealed that the mechanical protein polycystin-1(PC1,encoded by Pkd1)is critical for bone formation.However,the role of PC1 in bone resorption is unknown.Here,we found that PC1directly regulates osteoclastogenesis and bone resorption.The conditional deletion of Pkd1 in the osteoclast lineage resulted in a reduced number of osteoclasts,decreased bone resorption,and increased bone mass.A cohort study of 32,500 patients further revealed that autosomal dominant polycystic kidney disease,which is mainly caused by loss-of-function mutation of the PKD1 gene,is associated with a lower risk of hip fracture than those with other chronic kidney diseases.Moreover,mice with osteoclastspecific knockout of Pkd1 showed complete resistance to unloading-induced bone loss.A mechanistic study revealed that PC1 facilitated TAZ nuclear translocation via the C-terminal tail-TAZ complex and that conditional deletion of Taz in the osteoclast lineage resulted in reduced osteoclastogenesis and increased bone mass.Pharmacological regulation of the PC1-TAZ axis alleviated unloading-and estrogen deficiency-induced bone loss.Thus,the PC1-TAZ axis may be a potential therapeutic target for osteoclast-related osteoporosis.

Nanosecond pulsed electric fields prime mesenchymal stem cells to peptide ghrelin and enhance chondrogenesis and osteochondral defect repair in vivo

Mesenchymal stem cells(MSCs) are important cell sources in cartilage tissue development and homeostasis,and multiple strategies have been developed to improve MSCs chondrogenic differentiation with an aim of promoting cartilage regeneration.Here we report the effects of combining nanosecond pulsed electric fields(ns PEFs) followed by treatment with ghrelin(a hormone that stimulates release of growth hormone) to regulate chondrogenesis of MSCs.ns PEFs and ghrelin were observed to separately enhance the chondrogenesis of MSCs,and the effects were significantly enhanced when the bioelectric stimulation and hormone were combined,which in turn improved osteochondral tissue repair of these cells within Sprague Dawley rats.We further found that ns PEFs can prime MSCs to be more receptive to subsequent stimuli of differentiation by upregulated Oct4/Nanog and activated JNK signaling pathway.Ghrelin initiated chondrogenic differentiation by activation of ERK1/2 signaling pathway,and RNA-seq results indicated 243 genes were regulated,and JAK-STAT signaling pathway was involved.Interestingly,the sequential order of applying these two stimuli is critical,with ns PEFs pretreatment followed by ghrelin enhanced chondrogenesis of MSCs in vitro and subsequent cartilage regeneration in vivo,but not vice versa.This synergistic prochondrogenic effects provide us new insights and strategies for future cell-based therapies.

Research advances on antioxidation,neuroprotection,and molecular mechanisms of Lycium barbarum polysaccharides

Lycium barbarum polysaccharides(LBPs)are the major polysaccharides extracted from L.barbarum,which is used in traditional Chinese medicine(TCM)for treating diseases.Studies have shown that LBPs have important biological activities,such as antioxidation,anti-aging,neuroprotection,immune regulation.LBPs inhibit oxidative stress,improve neurodegeneration and stroke-induced neural injury,increase proliferation and differentiation of neural stem cell,and promote neural regeneration.Here we have reviewed latest advances in the biomedical activities of LBPs and improved methods for the isolation,extraction,and purification of LBPs.Then,new discoveries to decrease oxidative stress and cellular apoptosis,inhibit aging progress,and improve neural repair in neurodegeneration and ischemic brain injury have been discussed in detail through in vitro cell culture and in vivo animal studies.Importantly,the molecular mechanisms of LBPs in playing neuroprotective roles are further explored.Lastly,we discuss the perspective of LBPs as biomedical compounds in TCM and modern medicine and provide the experimental and theoretical evidence to use LBPs for the treatment of aging-related neurological diseases and stroke-induced neural injuries.