Wnt3a-induced ST2 decellularized matrix ornamented PCL scaffold for bone tissue engineering

The limited bioactivity of scaffold materials is an important factor that restricts the development of bone tissue engineering.Wnt3a activates the classicWnt/β-catenin signaling pathway which effects bone growth and development by the accumulation ofβ-catenin in the nucleus.In this study,we fabricated 3D printed PCL scaffold with Wnt3a-induced murine bone marrow-derived stromal cell line ST2 decellularized matrix(Wnt3a-ST2-dCM-PCL)and ST2 decellularized matrix(ST2-dCM-PCL)by freeze-thaw cycle and DNase decellularization treatment which efficiently decellularized>90%DNA while preserved most protein.Compared to ST2-dCM-PCL,Wnt3a-ST2-dCM-PCL significantly enhanced newly-seeded ST2 proliferation,osteogenic differentiation and upregulated osteogenic marker genes alkaline phosphatase(Alp),Runx2,type I collagen(Col 1)and osteocalcin(Ocn)mRNA expression.After 14 days of osteogenic induction,Wnt3a-ST2-dCM-PCL promoted ST2 mineralization.These results demonstrated that Wnt3a-induced ST2 decellularized matrix improve scaffold materials’osteoinductivity and osteoconductivity.

Sterilization and disinfection methods for decellularized matrix materials:Review,consideration and proposal

Sterilization is the process of killing all microorganisms,while disinfection is the process of killing or removing all kinds of pathogenic microorganisms except bacterial spores.Biomaterials involved in cell experiments,animal experiments,and clinical applications need to be in the aseptic state,but their physical and chemical properties as well as biological activities can be affected by sterilization or disinfection.Decellularized matrix(dECM)is the low immunogenicity material obtained by removing cells from tissues,which retains many inherent components in tissues such as proteins and proteoglycans.But there are few studies concerning the effects of sterilization or disinfection on dECM,and the systematic introduction of sterilization or disinfection for dECM is even less.Therefore,this review systematically introduces and analyzes the mechanism,advantages,disadvantages,and applications of various sterilization and disinfection methods,discusses the factors influencing the selection of sterilization and disinfection methods,summarizes the sterilization and disinfection methods for various common dECM,and finally proposes a graphical route for selecting an appropriate sterilization or disinfection method for dECM and a technical route for validating the selected method,so as to provide the reference and basis for choosing more appropriate sterilization or disinfection methods of various dECM.

A novel decellularized matrix of Wnt signaling-activated osteocytes accelerates the repair of critical-sized parietal bone defects with osteoclastogenesis, angiogenesis, and neurogenesis

Cell source is the key to decellularized matrix(DM)strategy.This study compared 3 cell types,osteocytes with/without dominant active Wnt/β-catenin signaling(daCO and WTO)and bone marrow stromal cells(BMSCs)for their DMs in bone repair.Decellularization removes all organelles and>95%DNA,and retained>74%collagen and>71%GAG,maintains the integrity of cell basement membrane with dense boundaries showing oval and honeycomb structure in osteocytic DM and smooth but irregular shape in the BMSC-DM.DM produced higher cell survival rate(90%)and higher proliferative activity.In vitro,daCO-DM induces more and longer stress fibers in BMSCs,conducive to cell adhesion,spreading,and osteogenic differentiation.8-wk after implantation of the critical-sized parietal bone defect model,daCO-DM formed tight structures,composed of a large number of densely-arranged type-I collagen under polarized light microscope,which is similar to and integrated with host bone.BV/TV(>54%)was 1.5,2.9,and 3.5 times of WTO-DM,BMSC-DM,and none-DM groups,and N.Ob/T.Ar(3.2×10^(2)/mm^(2))was 1.7,2.9,and 3.3 times.At 4-wk,daCO-DM induced osteoclastogenesis,2.3 times higher than WTO-DM;but BMSC-DM or none-DM didn't.daCO-DM increased the expression of RANKL and MCSF,Vegfa and Angpt1,and Ngf in BMSCs,which contributes to osteoclastogenesis,angiogenesis,and neurogenesis,respectively.daCO-DM promoted H-type vessel formation and nerve markersβ3-tubulin and NeuN expression.Conclusion:daCO-DM produces metabolic and neurovascularized organoid bone to accelerate the repair of bone defects.These features are expected to achieve the effect of autologous bone transplantation,suitable for transformation application.

Ureteral reconstruction with decellularized small intestinal submucosa matrix for ureteral stricture: A preliminary report of two cases

Objective:To determine the feasibility of decellularized small intestinal submu-cosa(5IS)matrix in repairing ureteral strictures.Methods:Two patients with ureteral stenoses underwent ureteral reconstruction with SIS ma-trix at the Zhejiang Provincial Corps Hospital of Chinese People's Armed Forces between June 2014 and June 2016.The ureteral stenoses were repaired with a semi-tubular SIS matrix and the postoperative recoveries were observed.Results:Both operations were successfully completed.The average operative time was 90 min and the average length of hospital stay was 15 days.No fevers,incision infections,intestinal obstruction,graft rejection,or other serious complications were noted.After 2 months,ure-teroscopic examinations showed that the surfaces of the original patches were covered by mu-Cosa and there were no apparent stenoses in the lumens.The ureteral stents were replaced every 2 months postoperatively and removed 12 months postoperatively.No infections or uri-nary leakage occurred after removal of the stents.Intravenous urography was performed 6 and 12 months postoperatively.The results showed that the ureters were not obstructed and there was no apparent stenosis at the anastomosis sites.The average follow-up time was>12 months.Long-term follow-up is still ongoing,and computed tomography examin ations of the urinary tract have been conducted in the outpatient department of our hospital 1,3,and 6 months after removal of the double-J stents,suggesting the absence of hydronephrosis.The serum creatinine levels remained stable during the follow-up.Conclusion:SIS matrix reconstruction is a feasible method to repair ureters stenosis.

Decellularized adipose matrix provides an inductive microenvironment for stem cells in tissue regeneration

Stem cells play a key role in tissue regeneration due to their self-renewal and multidirectional differentiation,which are continuously regulated by signals from the extracellular matrix(ECM)microenvironment.Therefore,the unique biological and physical characteristics of the ECM are important determinants of stem cell behavior.Although the acellular ECM of specific tissues and organs(such as the skin,heart,cartilage,and lung)can mimic the natural microenvironment required for stem cell differentiation,the lack of donor sources restricts their development.With the rapid development of adipose tissue engineering,decellularized adipose matrix(DAM)has attracted much attention due to its wide range of sources and good regeneration capacity.Protocols for DAM preparation involve various physical,chemical,and biological methods.Different combinations of these methods may have different impacts on the structure and composition of DAM,which in turn interfere with the growth and differentiation of stem cells.This is a narrative review about DAM.We summarize the methods for decellularizing and sterilizing adipose tissue,and the impact of these methods on the biological and physical properties of DAM.In addition,we also analyze the application of different forms of DAM with or without stem cells in tissue regeneration(such as adipose tissue),repair(such as wounds,cartilage,bone,and nerves),in vitro bionic systems,clinical trials,and other disease research.

A decellularized nerve matrix scaffold inhibits neuroma formation in the stumps of transected peripheral nerve after peripheral nerve injury

Traumatic painful neuroma is an intractable clinical disease characterized by improper extracellular matrix(ECM)deposition around the injury site.Studies have shown that the microstructure of natural nerves provides a suitable microenvironment for the nerve end to avoid abnormal hyperplasia and neuroma formation.In this study,we used a decellularized nerve matrix scaffold(DNM-S)to prevent against the formation of painful neuroma after sciatic nerve transection in rats.Our results showed that the DNM-S effectively reduced abnormal deposition of ECM,guided the regeneration and orderly arrangement of axon,and decreased the density of regenerated axons.The epineurium-perilemma barrier prevented the invasion of vascular muscular scar tissue,greatly reduced the invasion ofα-smooth muscle actin-positive myofibroblasts into nerve stumps,effectively inhibited scar formation,which guided nerve stumps to gradually transform into a benign tissue and reduced pain and autotomy behaviors in animals.These findings suggest that DNM-S-optimized neuroma microenvironment by ECM remodeling may be a promising strategy to prevent painful traumatic neuromas.

Preliminary studies of constructing a tissue-engineered lamellar corneal graft by culturing mesenchymal stem cells onto decellularized corneal matrix

AIM:To construct a competent corneal lamellar substitute in order to alleviate the shortage of human corneal donor.METHODS:Rabbit mesenchymal stem cells(MSCs)were isolated from bone marrow and identified by flow cytometric,osteogenic and adipogenic induction.Xenogenic decellularized corneal matrix(XDCM)was generated from dog corneas.MSCs were seeded and cultured on XDCM to construct the tissueengineered cornea.Post-transplantation biocompatibility of engineered corneal graft were tested by animal experiment.Rabbits were divided into two groups then underwent lamellar keratoplasty(LK)with different corneal grafts:1)XDCM group(n=5):XDCM;2)XDCM-MSCs groups(n=4):tissue-engineered cornea made up with XDCM and MSCs.The ocular surface recovery procedure was observed while corneal transparency,neovascularization and epithelium defection were measured and compared.In vivo on focal exam was performed 3 mo postoperatively.RESULTS:Rabbit MSCs were isolated and identified.Flow cytometry demonstrated isolated cells were CD90 positive and CD34,CD45 negative.Osteogenic and adipogenic induction verified their multipotent abilities.MSC-XDCM grafts were constructed and observed.In vivo transplantation showed the neovascularization in XDCMMSC group was much less than that in XDCM group postoperatively.Post-transplant 3-month confocal test showed less nerve regeneration and bigger cell-absent area in XDCM-MSC group.CONCLUSION:This study present a novel corneal tissue-engineered graft that could reduce post-operatively neovascularization and remain transparency,meanwhile shows that co-transplantation of MSCs may help increase corneal transplantation successful rate and enlarge the source range of corneal substitute to overcome cornea donor shortage.

Decellularized extracellular matrix materials for treatment of ischemic cardiomyopathy

Ischemic cardiomyopathy(ICM)affect millions of patients globally.Decellularized extracellular matrix materials(dECM)have components,microstructure and mechanical properties similar to healthy cardiac tissues,and can be manufactured into various forms of implantable biomaterials including injectable hydrogels or epicardial patches,which have been extensively reported to attenuate pathological left ventricular remodeling and maintain heart function.Recently,dECM medical devices for ICM treatment have been approved for clinical use or studied in clinical trials,exhibiting considerable translation potential.Cells,growth factors and other bioactive agents have been incorporated with different dECM materials to improve the therapeutic outcomes.In addition,more detailed aspects of the biological effects and mechanisms of dECM treatment are being revealed.This review summarized recent advances in dECM materials from variable sources for cardiac repair,including extraction of extracellular matrix,cell integration,smart manufacturing of injectable hydrogels and cardiac patch materials,and their therapeutic applications.Besides,this review provides an outlook on the cutting-edge development directions in the field.

Decellularized extracellular matrix-based composite scaffolds for tissue engineering and regenerative medicine

Despite the considerable advancements in fabricating polymeric-based scaffolds for tissue engineering,the clinical transformation of these scaffolds remained a big challenge because of the difficulty of simulating native organs/tissues'microenvironment.As a kind of natural tissue-derived biomaterials,decellularized extracellular matrix(dECM)-based scaffolds have gained attention due to their unique biomimetic properties,providing a specific microenvironment suitable for promoting cell proliferation,migration,attachment and regulating differentiation.The medical applications of dECM-based scaffolds have addressed critical challenges,including poor mechanical strength and insufficient stability.For promoting the reconstruction of damaged tissues or organs,dif-ferent types of dECM-based composite platforms have been designed to mimic tissue microenvironment,including by integrating with natural polymer or/and syntenic polymer or adding bioactive factors.In this review,we summarized the research progress of dECM-based composite scaffolds in regenerative medicine,highlighting the critical challenges and future perspectives related to the medical application of these composite materials。

TGF-β1-supplemented decellularized annulus fibrosus matrix hydrogels promote annulus fibrosus repair

Annulus fibrosus(AF)repair remains a challenge because of its limited self-healing ability.Endogenous repair strategies combining scaffolds and growth factors show great promise in AF repair.Although the unique and beneficial characteristics of decellularized extracellular matrix(ECM)in tissue repair have been demonstrated,the poor mechanical property of ECM hydrogels largely hinders their applications in tissue regeneration.In the present study,we combined polyethylene glycol diacrylate(PEGDA)and decellularized annulus fibrosus matrix(DAFM)to develop an injectable,photocurable hydrogel for AF repair.We found that the addition of PEGDA markedly improved the mechanical strength of DAFM hydrogels while maintaining their porous structure.Transforming growth factor-β1(TGF-β1)was further incorporated into PEGDA/DAFM hydrogels,and it could be continuously released from the hydrogel.The in vitro experiments showed that TGF-β1 facilitated the migration of AF cells.Furthermore,PEGDA/DAFM/TGF-β1 hydrogels supported the adhesion,proliferation,and increased ECM production of AF cells.In vivo repair performance of the hydrogels was assessed using a rat AF defect model.The results showed that the implantation of PEGDA/DAFM/TGF-β1 hydrogels effectively sealed the AF defect,prevented nucleus pulposus atrophy,retained disc height,and partially restored the biomechanical properties of disc.In addition,the implanted hydrogel was infiltrated by cells resembling AF cells and well integrated with adjacent AF tissue.In summary,findings from this study indicate that TGF-β1-supplemented DAFM hydrogels hold promise for AF repair.

Fibrotic liver extracellular matrix induces cancerous phenotype in biomimetic micro-tissues of hepatocellular carcinoma model

Background: Despite considerable advancements in identifying factors contributing to the development of hepatocellular carcinoma(HCC), the pathogenesis of HCC remains unclear. In many cases, HCC is a consequence of prolonged liver fibrosis, resulting in the formation of an intricate premalignant microenvironment. The accumulation of extracellular matrix(ECM) is a hallmark of premalignant microenvironment. Given the critical role of different matrix components in regulating cell phenotype and function, this study aimed to elucidate the interplay between the fibrotic matrix and malignant features in HCC. Methods: Liver tissues from both control(normal) and carbon tetrachloride(CCl_(4))-induced fibrotic rats were decellularized using sodium dodecyl sulfate(SDS) and Triton X-100. The resulting hydrogel from decellularized ECM was processed into micro-particles via the water-in-oil emulsion method. Microparticles were subsequently incorporated into three-dimensional liver biomimetic micro-tissues(MTs) comprising Huh-7 cells, human umbilical vein endothelial cells(HUVECs), and LX-2 cells. The MTs were evaluated using the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium(MTS) assay at day 11, immunofluorescence staining, immunoblotting, and spheroid migration assay at day 14 after co-culture. Results: Fibrotic matrix from CCl4-treated rat livers significantly enhanced the growth rate of the MTs and their expression of CCND1 as compared to the normal one. Fibrotic matrix, also induced the expression of epithelial-to-mesenchymal transition(EMT)-associated genes such as TWIST1, ACTA2, MMP9, CDH2, and VIMENTIN in the MTs as compared to the normal matrix. Conversely, the expression of CDH1 and hepatic maturation genes HNF4A, ALB, CYP3A4 was decreased in the MTs when the fibrotic matrix was used. Furthermore, the fibrotic matrix increased the migration of the MTs and their secretion of alpha-fetoprotein. Conclusions: Our findings suggest a regulatory role for the fibrotic matrix in promoting cancerous phenotype, which could potentially accelerate the progression of malignancy in the liver.

Decellularized Extracellular Matrix Containing Electrospun Fibers for Nerve Regeneration:A Comparison Between Core–Shell Structured and Preblended Composites

Advanced biomaterial-based strategies for treatment of peripheral nerve injury require precise control over both topological and biological cues for facilitating rapid and directed nerve regeneration.As a highly bioactive and tissue-specifc natural material,decellularized extracellular matrix(dECM)derived from peripheral nerves(decellularized nerve matrix,DNM)has drawn increasing attention in the feld of regenerative medicine,due to its outstanding capabilities in facilitating neurite outgrowth and remyelination.To induce and maintain sufcient topological guidance,electrospinning was conducted for fabrication of axially aligned nanofbers consisting of DNM and poly(ε-caprolactone)(PCL).Core–shell structured fbers were prepared by coaxial electrospinning using DNM as the shell and PCL as the core.Compared to the aligned electrospun fbers using preblended DNM/PCL,the core–shell structured fbers exhibited lower tensile strength,faster degradation,but considerable toughness for nerve guidance conduit preparation and relatively intact fbrous structure after long-term degradation.More importantly,the full DNM surface coverage of the aligned core–shell fbers efectively promoted axonal extension and Schwann cells migration.The DNM contents further triggered neurite bundling and myelin formation toward nerve fber maturation and functionalization.Herein,we not only pursue a multi-functional scafold design for nerve regeneration,a detailed comparison between core–shell structured and preblended electrospinning of DNM/PCL composites was also provided as an applicable paradigm for advanced tissue-engineered strategies using dECM-based biomaterials.

Decellularized extracellular matrix mediates tissue construction and regeneration

Contributing to organ formation and tissue regeneration,extracellular matrix(ECM)constituents provide tissue with three-dimensional(3D)structural integrity and cellular-function regulation.Containing the crucial traits of the cellular microenvironment,ECM substitutes mediate cell–matrix interactions to prompt stem-cell proliferation and differentiation for 3D organoid construction in vitro or tissue regeneration in vivo.However,these ECMs are often applied generically and have yet to be extensively developed for specific cell types in 3D cultures.Cultured cells also produce rich ECM,particularly stromal cells.Cellular ECM improves 3D culture development in vitro and tissue remodeling during wound healing after implantation into the host as well.Gaining better insight into ECM derived from either tissue or cells that regulate 3D tissue reconstruction or organ regeneration helps us to select,produce,and implant the most suitable ECM and thus promote 3D organoid culture and tissue remodeling for in vivo regeneration.Overall,the decellularization methodologies and tissue/cell-derived ECM as scaffolds or cellular-growth supplements used in cell propagation and differentiation for 3D tissue culture in vitro are discussed.Moreover,current preclinical applications by which ECM components modulate the wound-healing process are reviewed.

Tailoring the multiscale mechanics of tunable decellularized extracellular matrix (dECM) for wound healing through immunomodulation

With the discovery of the pivotal role of macrophages in tissue regeneration through shaping the tissue immune microenvironment, various immunomodulatory strategies have been proposed to modify traditional biomaterials. Decellularized extracellular matrix (dECM) has been extensively used in the clinical treatment of tissue injury due to its favorable biocompatibility and similarity to the native tissue environment. However, most reported decellularization protocols may cause damage to the native structure of dECM, which undermines its inherent advantages and potential clinical applications. Here, we introduce a mechanically tunable dECM prepared by optimizing the freeze-thaw cycles. We demonstrated that the alteration in micromechanical properties of dECM resulting from the cyclic freeze-thaw process contributes to distinct macrophage-mediated host immune responses to the materials, which are recently recognized to play a pivotal role in determining the outcome of tissue regeneration. Our sequencing data further revealed that the immunomodulatory effect of dECM was induced via the mechnotrasduction pathways in macrophages. Next, we tested the dECM in a rat skin injury model and found an enhanced micromechanical property of dECM achieved with three freeze-thaw cycles significantly promoted the M2 polarization of macrophages, leading to superior wound healing. These findings suggest that the immunomodulatory property of dECM can be efficiently manipulated by tailoring its inherent micromechanical properties during the decellularization process. Therefore, our mechanics-immunomodulation-based strategy provides new insights into the development of advanced biomaterials for wound healing.

Injectable decellularized extracellular matrix hydrogel loaded with exosomes encapsulating curcumin for prevention of cardiac fibrosis after myocardial infarction

Excessive cardiac fibrosis impairs cardiac repair after myocardial infarction(MI).In this work,an in-jectable composite hydrogel integrating natural biomaterials,exosomes,and bioactive molecules is de-veloped to prevent or alleviate cardiac fibrosis.Curcumin,a natural molecule with antifibrotic activity,is encapsulated in the exosomes that are isolated from bone marrow-derived mesenchymal stem cells to enhance its water solubility and bioavailability.These composite exosomes are efficiently internalised by fibroblasts and effectively inhibit their transition to myofibroblasts in vitro.Decellularized porcine cardiac extracellular matrix(dECM)hydrogel is used as the carrier for delivering these composite exosomes to the infarcted myocardium,not only improving the retention of exosomes but also providing mechani-cal support and structural protection.Injection of this hydrogel into the infarcted heart of a mouse MI model leads to a decrease in collagen deposition,alleviation of fibrosis,a reduction in infarct size,and an improvement in cardiac function.The reported composite hydrogel comprising natural materials and biomolecules exhibits good biocompatibility and bioactivity.Altogether,this study demonstrates that the dECM hydrogel is a suitable platform for the local delivery of antifibrotic biomolecule-encapsulating exo-somes to prevent myocardial fibrosis after MI and have great potential for the treatment of MI in clinical settings.

Decellularized extracellular matrix particle-based biomaterials for cartilage repair applications

Cartilage Decellularized ExtraCellular Matrix(dECM)materials have shown promising cartilage regenera-tion capacity due to their chondrogenic bioactivity.However,the limited retention of ECM components and the reduced integrity of functional ECM molecules during traditional decellularization processes im-pair the biomimicry of these materials.The current study aims to fabricate biomimetic materials con-taining decellularized cartilage particles that have an intact molecular structure and native composition as biomaterial inks and hydrogels for cartilage repair.For this,we established a novel two-fraction de-cellularization strategy for the preparation of reconstituted dECM(rdECM)particles by mixing the two-fraction components,as well as a one-fraction decellularization strategy for the preparation of biomimetic dECM(bdECM)particles.Hyaluronic acid-tyramine(THA)hydrogels containing rdECM or bdECM particles were produced and characterized via rheological test,swelling and stability evaluation,and compression test.The results showed that our novel decellularization strategies preserved intact proteoglycans and collagen at a higher retention rate with adequate DNA removal compared to traditional methods of de-cellularization.The addition of rdECM or bdECM particles significantly increased the shear moduli of the THA bioinks while preserving their shear-thinning properties.bdECM particle-embedded THA hydrogels also achieved long-term stability with a swelling ratio of 70%and high retention of glycosaminoglycans and collagen after long-term incubation,while rdECM particle-embedded THA hydrogels showed unsat-isfactory stability as self-standing biomaterials.Compared to pure THA hydrogels,the addition of bdECM particles significantly enhanced the compression moduli.In summary,our decellularization methods are successful in the retention of functional and intact cartilage components with high yield.Both rdECM and bdECM particles can be supplemented in THA bioinks for biomimetic cartilage 3D printing.Hydro-gels with cartilage bdECM particles possess the functional structure and the natural composition of car-tilage ECM,long-term stability,and enhanced mechanical properties,and are promising biomaterials for cartilage repair.

Decellularized extracellular matrix as scaffold for cancer organoid cultures of colorectal peritoneal metastases

Peritoneal metastases (PM) from colorectal cancer (CRC) are associated with poor survival. The extracellular matrix (ECM) plays a fundamental role in modulating the homing of CRC metastases to the peritoneum. The mechanisms underlying the interactions between metastatic cells and the ECM, however, remain poorly understood, and the number of in vitro models available for the study of the peritoneal metastatic process is limited. Here, we show that decellularized ECM of the peritoneal cavity allows the growth of organoids obtained from PM, favoring the development of three-dimensional (3D) nodules that maintain the characteristics of in vivo PM. Organoids preferentially grow on scaffolds obtained from neoplastic peritoneum, which are characterized by greater stiffness than normal scaffolds. A gene expression analysis of organoids grown on different substrates reflected faithfully the clinical and biological characteristics of the organoids. An impact of the ECM on the response to standard chemotherapy treatment for PM was also observed. The ex vivo 3D model, obtained by combining patient-derived decellularized ECM with organoids to mimic the metastatic niche, could be an innovative tool to develop new therapeutic strategies in a biologically relevant context to personalize treatments.

Construction of tissue-engineered heart valves by using decellularized scaffolds and endothelial progenitor cells

Background Tissue-engineered heart valves have the potential to overcome the limitations of present heart valve replacements. This study was designed to develop a tissue engineering heart valve by using human umbilical cord blood-derived endothelial progenitor cells （EPCs） and decellularized valve scaffolds. Methods Decellularized valve scaffolds were prepared from fresh porcine heart valves. EPCs were isolated from fresh human umbilical cord blood by density gradient centrifugation, cultured for 3 weeks in EGM-2-MV medium, by which time the resultant cell population became endothelial in nature, as assessed by immunofluorescent staining. EPC-derived endothelial cells were seeded onto the decellularized scaffold at 3 × 10^6 cells/cm^2 and cultured under static conditions for 7 days. Proliferation of the seeded cells on the scaffolds was detected using the MTT assay. Tissue-engineered heart valves were analyzed by HE staining, immunofluorescent staining and scanning electron microscopy. The anti-thrombogenic function of the endothelium on the engineered heart valves was evaluated by platelet adhesion experiments and reverse transcription-polymerase chain reaction （RT-PCR） analysis for the expression of endothelial nitric oxide synthase （eNOS） and tissue-type plasminogen activator （t-PA）.Results EPC-derived endothelial cells showed a histolytic cobblestone morphology, expressed specific markers of the endothelial cell lineage including von Willebrand factor （vWF） and CD31, bound a human endothelial cell-specific lectin, Ulex Europaeus agglutinin-1 （UEA-1）, and took up Dil-labeled low density lipoprotein （Dil-Ac-LDL）. After seeding on the decellularized scaffold, the cells showed excellent metabolic activity and proliferation. The cells formed confluent endothelial monolayers atop the decellularized matrix, as assessed by HE staining and immunostaining for vWF and CD31. Scanning electron microscopy demonstrated the occurrence of tight junctions between cells forming the confluent monolayer. Platelets adhesion experiments suggested that the neo-endothelium was non-thrombogenic. The expression levels of eNOS and t-PA genes in the neo-endothelium were quite similar to those in human umbilical vein endothelial cells. Conclusions EPCs isolated from the human umbilical cord blood can differentiate into endothelial cells in vitro and form a functional endothelium atop decellularized heart valve scaffolds. Thus, EPCs may be a promising cell source for constructing tissue-engineered heart valves.

Decellularized Disc Hydrogels for hBMSCs tissue-specific differentiation and tissue regeneration

Tissue specificity,a key factor in the decellularized tissue matrix(DTM),has shown bioactive functionalities in tuning cell fate-e.g.,the differentiation of mesenchymal stem cells.Notably,cell fate is also determined by the living microenvironment,including material composition and spatial characteristics.Herein,two neighboring tissues within intervertebral discs,the nucleus pulposus(NP)and annulus fibrosus(AF),were carefully processed into DTM hydrogels(abbreviated DNP-G and DAF-G,respectively)to determine the tissue-specific effects on stem cell fate,such as specific components and different culturing methods,as well as in vivo regeneration.Distinct differences in their protein compositions were identified by proteomic analysis.Interestingly,the fate of human bone marrow mesenchymal stem cells(hBMSCs)also responds to both culturing methods and composition.Generally,hBMSCs cultured with DNP-G(3D)differentiated into NP-like cells,while hBMSCs cultured with DAF-G(2D)underwent AF-like differentiation,indicating a close correlation with the native microenvironments of NP and AF cells,respectively.Furthermore,we found that the integrin-mediated RhoA/LATS/YAP1 signaling pathway was activated in DAF-G(2D)-induced AF-specific differentiation.Additionally,the activation of YAP1 determined the tendency of NP-or AF-specific differentiation and played opposite regulatory effects.Finally,DNP-G and DAF-G specifically promoted tissue regeneration in NP degeneration and AF defect rat models,respectively.In conclusion,DNP-G and DAF-G can specifically determine the fate of stem cells through the integrin-mediated RhoA/LATS/YAP1 signaling pathway,and this tissue specificity is both compositional and spatial,supporting the utilization of tissue-specific DTM in advanced treatments of intervertebral disc degeneration.

Cardiac tissue-derived extracellular matrix scaffolds for myocardial repair:advantages and challenges

Decellularized extracellular matrix(dECM)derived from myocardium has been widely explored as a nature scaffold for cardiac tissue engineering applications.Cardiac dECM offers many unique advantages such as preservation of organ-specific ECM microstructure and composition,demonstration of tissue-mimetic mechanical properties and retention of biochemical cues in favor of subsequent recellularization.However,current processes of dECM decellularization and recellularization still face many challenges including the need for balance between cell removal and extracellular matrix preservation,efficient recellularization of dECM for obtaining homogenous cell distribution,tailoring material properties of dECM for enhancing bioactivity and prevascularization of thick dECM.This review summarizes the recent progresses of using dECM scaffold for cardiac repair and discusses its major advantages and challenges for producing biomimetic cardiac patch.