Decellularized Extracellular Matrix Materials for Cardiac Repair and Regeneration

Harnessing synergistic effects of MMP-2 Inhibition and bFGF to simultaneously preserve and vascularize cardiac extracellular matrix after myocardial infarction

Myocardial infarction (MI) leads to cardiac extracellular matrix (ECM) degradation and fibrosis, reducing heart function. Consequently, simultaneously addressing ECM degradation and inhibiting cardiac fibrosis is essential for preserving heart function and mitigating adverse remodeling. However, the preserved ECM becomes unstable if not vascularized, as its structure and composition undergo changes over time. ECM vascularization is crucial to improve cardiac function. Presently, there is no clinically approved therapy that can simultaneously preserve and vascularize the ECM, and inhibit cardiac fibrosis. Our study develops a drug delivery system aiming to achieve these goals. It includes the peptide CTTHWGFTLC (CTT), a specific MMP-2 inhibitor, and basic fibroblast growth factor (bFGF), a potent factor with pro-angiogenic and anti-fibrotic properties. An injectable hydrogel serves as the carrier, featuring a rapid gelation that allows for the substantial retention of drugs. Additionally, the hydrogel has the capability to scavenge upregulated reactive oxygen species (ROS), thereby reducing tissue inflammation. Our findings indicate that CTT and bFGF synergistically enhance endothelial cell migration and tube formation while inhibiting the differentiation of fibroblasts into myofibroblasts. Upon delivery into hearts, the system significantly decreases MMP-2 level, promotes angiogenesis, attenuates cardiac fibrosis, and alleviates inflammation, resulting in a noteworthy cardiac function improvement. STATEMENT OF SIGNIFICANCE: 1) This work addresses key challenges in cardiac repair after myocardial infarction (MI), including extracellular matrix (ECM) degradation, vascularization, and fibrosis. 2) We combined an MMP-2/9 inhibitor (CTT) with bFGF to prevent ECM degradation, enhance vascularization, and inhibit fibrosis, providing a comprehensive strategy to improve cardiac function. 3) An injectable hydrogel was developed with rapid gelation and mechanical properties similar to heart tissue, ensuring efficient drug retention and reducing tissue stress. 4) The hydrogel enabled controlled, spatiotemporal release of CTT to dynamically reduce MMP-2/9 activity, and gradually released bFGF to promote angiogenesis and inhibit fibrosis.

Decellularized Extracellular Matrix Scaffolds: Recent Advances and Emerging Strategies in Bone Tissue Engineering

Bone tissue engineering (BTE) is a complex biological process involving the repair of bone tissue with proper neuronal network and vasculature as well as bone surrounding soft tissue. Synthetic biomaterials used for BTE should be biocompatible, support bone tissue regeneration, and eventually be degraded in situ and replaced with the newly generated bone tissue. Recently, various forms of bone graft materials such as hydrogel, nanofiber scaffolds, and 3D printed composite scaffolds have been developed for BTE application. Decellularized extracellular matrix (DECM), a kind of natural biological material obtained from specific tissues and organs, has certain advantages over synthetic and exogenous biomaterial-derived bone grafts. Moreover, DECM can be developed from a wide range of biological sources and possesses strong molding abilities, natural 3D structures, and bioactive factors. Although DECM has shown robust osteogenic, proangiogenic, immunomodulatory, and bone defect healing potential, the rapid degradation and limited mechanical properties should be improved for bench-to-bed translation in BTE. This review summarizes the recent advances in DECM-based BTE and discusses emerging strategies of DECM-based BTE.

Integrating 3D Bioprinting and Organoids to Better Recapitulate the Complexity of Cellular Microenvironments for Tissue Engineering

Organoids, with their capacity to mimic the structures and functions of human organs, have gained significant attention for simulating human pathophysiology and have been extensively investigated in the recent past. Additionally, 3D bioprinting, as an emerging bio-additive manufacturing technology, offers the potential for constructing heterogeneous cellular microenvironments, thereby promoting advancements in organoid research. In this review, the latest developments in 3D bioprinting technologies aimed at enhancing organoid engineering are introduced. The commonly used bioprinting methods and materials for organoids, with a particular emphasis on the potential advantages of combining 3D bioprinting with organoids are summarized. These advantages include achieving high cell concentrations to form large cellular aggregates, precise deposition of building blocks to create organoids with complex structures and functions, and automation and high throughput to ensure reproducibility and standardization in organoid culture. Furthermore, this review provides an overview of relevant studies from recent years and discusses the current limitations and prospects for future development.

The considerations on selecting the appropriate decellularized ECM for specific regeneration demands

An ideal biomaterial should create a customized tissue-specific microenvironment that can facilitate and guide the tissue repair process. Due to its good biocompatibility and similar biochemical properties to native tissues, decellularized extracellular matrix (dECM) generally yields enhanced regenerative outcomes, with improved morphological and functional recovery. By utilizing various decellularization techniques and post-processing protocols, dECM can be flexibly prepared in different states from various sources, with specifically customized physicochemical properties for different tissues. To initiate a well-orchestrated tissue-regenerative response, dECM exerts multiple effects at the wound site by activating various overlapping signaling pathways to promote cell adhesion, proliferation, and differentiation, as well as suppressing inflammation via modulation of various immune cells, including macrophages, T cells, and mastocytes. Functional tissue repair is likely the main aim when employing the optimized dECM biomaterials. Here, we review the current applications of different kinds of dECMs in an attempt to improve the efficiency of tissue regeneration, highlighting key considerations on developing dECM for specific tissue engineering applications.

Photo-responsive decellularized small intestine submucosa hydrogels

Decellularized small intestine submucosa (dSIS) is a promising biomaterial for promoting tissue regeneration. Isolated from the submucosal layer of animal jejunum, SIS is rich in extracellular matrix (ECM) proteins, including collagen, laminin, and fibronectin. Following mild decellularization, dSIS becomes an acellular matrix that supports cell adhesion, proliferation, and differentiation. Conventional dSIS matrix is usually obtained by thermal crosslinking, which yields a soft scaffold with low stability. To address these challenges, dSIS has been modified with methacrylate groups for photocrosslinking into stable hydrogels. However, dSIS has not been modified with clickable handles for orthogonal crosslinking. Here, we report the development of norbornene-modified dSIS, named dSIS-NB, via reacting amine groups of dSIS with carbic anhydride in acidic aqueous reaction conditions. Using triethylamine (TEA) as a mild base catalyst, we obtained high degrees of NB substitution on dSIS. In addition to describing the synthesis of dSIS-NB, we explored its adaptability in orthogonal hydrogel crosslinking and used dSIS-NB hydrogels for cancer and vascular tissue engineering. Impressively, compared with physically crosslinked dSIS and collagen matrices, orthogonally crosslinked dSIS-NB hydrogels supported rapid dissemination of cancer cells and superior vasculogenic and angiogenic properties. dSIS-NB was also exploited as a versatile bioink for 3D bioprinting applications.

Rebuilding vascular access: from the viewpoint of mechanics and materials

This review presents a comprehensive analysis of vascular access in hemodialysis, focusing on the current modalities, their associated challenges, and recent technological advancements. It closely examines the status of three primary types of vascular access: arteriovenous fistulas, arteriovenous grafts, and central venous catheters. The review delves into the complications and pathologies associated with these access types, emphasizing the mechanobiology-related pathogenesis of arteriovenous access. Furthermore, it explores recent clinical trials, biomaterials, and device innovations, highlighting novel pharmaceutical approaches, advanced materials, device designs, and cutting-edge technologies aimed at enhancing the efficacy, safety, and longevity of vascular access in hemodialysis. This synthesis of current knowledge and emerging trends underscores the dynamic evolution of vascular access strategies and their critical role in improving patient care in hemodialysis.

Single-cell transcriptomics reveals neural stem cell trans-differentiation and cell subpopulations in whole heart decellularized extracellular matrix

The whole heart decellularized extracellular matrix (ECM) has become a promising scaffold material for cardiac tissue engineering. Our previous research has shown that the whole heart acellular matrix possesses the memory function regulating neural stem cells (NSCs) trans-differentiating to cardiac lineage cells. However, the cell subpopulations and phenotypes in the trans-differentiation of NSCs have not been clearly identified. Here, we performed single-cell RNA sequencing and identified 2,765 cells in the recellularized heart with NSCs revealing the cellular diversity of cardiac and neural lineage, confirming NSCs were capable of trans-differentiating into the cardiac lineage while maintaining the original ability to differentiate into the neural lineage. Notably, the trans-differentiated heart-like cells have dual signatures of neuroectoderm and cardiac mesoderm. This study unveils an in-depth mechanism underlying the trans-differentiation of NSCs and provides a new opportunity and theoretical basis for cardiac regeneration.

Facile engineering of interactive double network hydrogels for heart valve regeneration

Regenerative heart valve prostheses are essential for treating valvular heart disease, which requested interactive materials that can adapt to the tissue remodeling process. Such materials typically involves intricate designs with multiple active components, limiting their translational potential. This study introduces a facile method to engineer interactive materials for heart valve regeneration using 1,1'-thiocarbonyldiimidazole (TCDI) chemistry. TCDI crosslinking forms cleavable thiourea and thiocarbamate linkages which could gradually release H2S during degradation, therefore regulates the immune microenvironment and accelerates tissue remodeling. By employing this approach, a double network hydrogel was formed on decellularized heart valves (DHVs), showcasing robust anti-calcification and anti-thrombosis properties post fatigue testing. Post-implantation, the DHVs could adaptively degrade during recellularization, releasing H2S to further support tissue regeneration. Therefore, the comprehensive endothelial cell coverage and notable extracellular matrix remodeling could be clearly observed. This accessible and integrated strategy effectively overcomes various limitations of bioprosthetic valves, showing promise as an attractive approach for immune modulation of biomaterials.

The Prospect of Hepatic Decellularized Extracellular Matrix as a Bioink for Liver 3D Bioprinting

The incidence of liver diseases is high worldwide. Many factors can cause liver fibrosis, which in turn can lead to liver cirrhosis and even liver cancer. Due to the shortage of donor organs, immunosuppression, and other factors, only a few patients are able to undergo liver transplantation. Therefore, how to construct a bioartificial liver that can be transplanted has become a global research hotspot. With the rapid development of three-dimensional (3D) bioprinting in the field of tissue engineering and regenerative medicine, researchers have tried to use various 3D bioprinting technologies to construct bioartificial livers in vitro. In terms of the choice of bioinks, liver decellularized extracellular matrix (dECM) has many advantages over other materials for cell-laden hydrogel in 3D bioprinting. This review mainly summarizes the acquisition of liver dECM and its application in liver 3D bioprinting as a bioink with respect to availability, printability, and biocompatibility in many aspects and puts forward the current challenges and prospects.

Engineering a robust and anisotropic cardiac-specific extracellular matrix scaffold for cardiac patch tissue engineering

Extracellular matrix (ECM) fabricated using human induced pluripotent stem cells (hiPSCs)-derived cardiac fibroblasts (hiPSC-CFs) could serve as a completely biological scaffold for an engineered cardiac patch, leveraging the unlimited source and outstanding reproducibility of hiPSC-CFs. Additionally, hiPSC-CF-derived ECM (hiPSC-CF-ECM) holds the potential to enhance maturation of exogenous cardiomyocytes, such as hiPSC-derived cardiomyocytes (hiPSC-CMs), by providing a microenvironment rich in cardiac-specific biochemical and signaling cues. However, achieving sufficient robustness of hiPSC-CF-ECM is challenging. This study aims to achieve appropriate ECM deposition, scaffold thickness, and mechanical strength of an aligned hiPSC-CF-ECM by optimizing the culture period, ranging from 2 to 10 weeks, of hiPSC-CFs grown on micro-grated substrates, which can direct the alignment of both hiPSC-CFs and their secreted ECM. The hiPSC-CFs demonstrated a production rate of 13.5 µg ECM per day per 20,000 cells seeded. An anisotropic nanofibrous hiPSC-CF-ECM scaffold with a thickness of 20.0 ± 2.1 µm was achieved after 6 weeks of culture, followed by decellularization. Compositional analysis through liquid chromatography-mass spectrometry (LC-MS) revealed the presence of cardiac-specific fibrillar collagens, non-fibrillar collagens, and matricellular proteins. Uniaxial tensile stretching of the hiPSC-CF-ECM scaffold indicated robust tensile resilience. Finally, hiPSCs-CMs cultured on the hiPSC-CF-ECM exhibited alignment following the guidance of ECM nanofibers and demonstrated mature organization of key structural proteins. The culture duration of the anisotropic hiPSC-CF-ECM was successfully refined to achieve a robust scaffold containing structural proteins that resembles cardiac microenvironment. This completely biological, anisotropic, and cardiac-specific ECM holds great potential for cardiac patch engineering.

Rapid Volumetric Bioprinting of Decellularized Extracellular Matrix Bioinks

Decellularized extracellular matrix (dECM)-based hydrogels are widely applied to additive biomanufacturing strategies for relevant applications. The extracellular matrix components and growth factors of dECM play crucial roles in cell adhesion, growth, and differentiation. However, the generally poor mechanical properties and printability have remained as major limitations for dECM-based materials. In this study, heart-derived dECM (h-dECM) and meniscus-derived dECM (Ms-dECM) bioinks in their pristine, unmodified state supplemented with the photoinitiator system of tris(2,2-bipyridyl) dichlororuthenium(II) hexahydrate and sodium persulfate, demonstrate cytocompatibility with volumetric bioprinting processes. This recently developed bioprinting modality illuminates a dynamically evolving light pattern into a rotating volume of the bioink, and thus decouples the requirement of mechanical strengths of bioprinted hydrogel constructs with printability, allowing for the fabrication of sophisticated shapes and architectures with low-concentration dECM materials that set within tens of seconds. As exemplary applications, cardiac tissues are volumetrically bioprinted using the cardiomyocyte-laden h-dECM bioink showing favorable cell proliferation, expansion, spreading, biomarker expressions, and synchronized contractions; whereas the volumetrically bioprinted Ms-dECM meniscus structures embedded with human mesenchymal stem cells present appropriate chondrogenic differentiation outcomes. This study supplies expanded bioink libraries for volumetric bioprinting and broadens utilities of dECM toward tissue engineering and regenerative medicine.

Targeted delivery of black phosphorus nanosheets by ROS responsive complex hydrogel based on angiogenesis and antioxidant promotes myocardial infarction repair

Myocardial infarction (MI) is one of the leading causes of death. This is attributed to the dramatic changes in the myocardial microenvironment post-MI. Therefore, effective intervention in the early stages of MI is significant for inhibiting its progression and improving cardiac function. Herein, an injectable composite hydrogel scaffold (Gel-pBP@Mg) was developed by integrating magnesium (Mg)-modified black phosphorus nanosheets (pBP@Mg) into a reactive oxygen species-responsive hydrogel (Gel). This loose and porous Gel provides a natural platform for carrying pBP@Mg. In situ, sustained release of pBP@Mg is achieved via responsive ROS degradation in the infarct site. The high ROS reactivity of Black phosphorus nanosheets (BPNSs) can effectively inhibit the progression of oxidative stress in the infarct area and reduce inflammatory response by down-regulating the NF-κB pathway. Additionally, the sustained release of Mg loaded on the surface of BPNSs can effectively promote angiogenesis in MI, which is significant for the long-term prognosis after infarction. Our developed Gel-pBP@Mg effectively blocked infarction progression and improved myocardial function by sustainably inhibiting the "oxidative stress-inflammation" reaction chain and pro-angiogenesis. This study reveals Gel-pBP@Mg composite therapeutic potential in treating MI through In vitro and In vivo studies, providing a promising modality for MI treatment.

Exosomes based strategies for cardiovascular diseases: Opportunities and challenges

Exosomes, as nanoscale extracellular vesicles (EVs), are secreted by all types of cells to facilitate intercellular communication in living organisms. After being taken up by neighboring or distant cells, exosomes can alter the expression levels of target genes in recipient cells and thereby affect their pathophysiological outcomes depending on payloads encapsulated therein. The functions and mechanisms of exosomes in cardiovascular diseases have attracted much attention in recent years and are thought to have cardioprotective and regenerative potential. This review summarizes the biogenesis and molecular contents of exosomes and details the roles played by exosomes released from various cells in the progression and recovery of cardiovascular disease. The review also discusses the current status of traditional exosomes in cardiovascular tissue engineering and regenerative medicine, pointing out several limitations in their application. It emphasizes that some of the existing emerging industrial or bioengineering technologies are promising to compensate for these shortcomings, and the combined application of exosomes and biomaterials provides an opportunity for mutual enhancement of their performance. The integration of exosome-based cell-free diagnostic and therapeutic options will contribute to the further development of cardiovascular regenerative medicine.

In vitro development of a muscle-tendon junction construct using decellularised extracellular matrix: Effect of cyclic tensile loading

The muscle tendon junction (MTJ) plays a crucial role in transmitting the force generated by muscles to the tendon and then to the bone. Injuries such as tears and strains frequently happen at the MTJ, where the regenerative process is limited due to poor vascularization and the complex structure of the tissue. Current solutions for a complete tear at the MTJ have not been successful and therefore, the development of a tissue-engineered MTJ may provide a more effective treatment. In this study, decellularised extracellular matrix (DECM) derived from sheep MTJ was used to provide a scaffold for the MTJ with the relevant mechanical properties and differentiation cues such as the relase of growth factors. Human mesenchymal stem cells (MSCs) were seeded on DECM and 10 % cyclic strain was applied using a bioreactor. MSCs cultured on DECM showed significantly higher gene and protein expression of MTJ markers such as collagen 22, paxillin and talin, than MSCs in 2D culture. Although collagen 22 protein expression was higher in the cells with strain than without strain, reduced gene expression of other MTJ markers was observed when the strain was applied. DECM combined with 10 % strain enhanced myogenic differentiation, while tenogenic differentiation was reduced when compared to static cultures of MSCs on DECM. For the first time, these results showed that DECM derived from the MTJ can induce MTJ marker gene and protein expression by MSCs, however, the effect of strain on the MTJ development in DECM culture needs further investigation.

Decellularized tissues as platforms for digestive system cancer models

The extracellular matrix (ECM) is a multifunctional network of macromolecules that regulate various cellular functions and physically support the tissues. Besides physiological conditions, the ECM also changes during pathological conditions such as cancer. As tumor cells proliferate, notable changes occur in the quantity and makeup of the surrounding ECM. Therefore, the role of this noncellular component of tissues in studies of tumor microenvironments should be considered. So far, many attempts have been made to create 2-dimensional (2D) or 3-dimensional (3D) models that can replicate the intricate connections within the tumor microenvironment. Decellularized tissues are proper scaffolds that imitate the complex nature of native ECM. This review aims to summarize 3D models of digestive system cancers based on decellularized ECMs. These ECM-based scaffolds will enable us to study the interactive communication between cells and their surrounding environment which brings new potential for a better understanding of the pathophysiology of cancer.

Effect of human heart valve-derived ECM and NP/PCL electrospun nanofibrous sheet on mice bone marrow mononuclear cells and cardiac repair

Background

Biomaterials can improve cardiac repair combined with transplantation of bone marrow mononuclear cells (BMMNCs). In this study, we compared the phenotype and cardiac repair between human heart valve-derived scaffold (hHVS) and natural protein/polycaprolactone (NP/PCL) anchored BMNNCs.

Methods and results

BMMNCs were obtained from mice five days following myocardial infarction. Subsequently, BMMNCs were separately cultured on hHVS and PCL. Proliferation and cardiomyogenic differentiation were detected in vitro. Cardiac function was measured after transplantation of cell-seeded cardiac patch on MI mice. After that, the BMMNCs were collected for mRNA sequencing after culturing on the scaffolds. Upon anchoring onto hHVS or PCL, BMMNCs exhibited an increased capacity for proliferation in vitro, however, the cells on hHVS exhibited superior cardiomyogenic differentiation ability. Moreover, both BMMNCs-seeded biomaterials effectively improved cardiac function after 4 weeks of transplantation, with reduced infarction area and restricted LV remodeling. Cell-seeded hHVS was superior to cell-seeded PCL.

Conclusion

BMMNCs on hHVS showed better capacity in both cell cardiac repairing and improvement for cardiac function than on PCL. Compared with seeded onto PCL, BMMNCs on hHVS had 253 genes up regulated and 189 genes down regulated. The reason for hHVS' better performance than PCL as a scaffold for BMMNCs might be due to the fact that optimized method of decellularization let more cytokines in ECM retained.

Crosslinking strategies of decellularized extracellular matrix in tissue regeneration

By removing the immunogenic cellular components through various decellularization methods, decellularized extracellular matrix (dECM) is considered a promising material in the field of tissue engineering and regenerative medicine with highly preserved physicochemical properties and superior biocompatibility. However, decellularization treatment can lead to some loss of structural integrity, mechanical strength, degradation stability, and biological performance of dECM biomaterials. Therefore, physical and chemical crosslinking methods are preferred to restore or even improve the biomechanical properties, stability, and bioactivity, and to achieve a delicate balance between degradation of the implanted biomaterial and regeneration of the host tissue. This review provides an overview of dECM biomaterials, and describes and compares the mechanisms and characteristics of commonly used crosslinking methods for dECM, with a focus on the potential applications of versatile dECM-based biomaterials derived from skin, cardiac tissues (pericardium, heart valves, myocardial tissue), blood vessels, liver, and kidney, modified with different chemical crosslinking reagents, in tissue and organ regeneration.

Engineered platforms for mimicking cardiac development and drug screening

Congenital heart defects are associated with significant health challenges, demanding a deep understanding of the underlying biological mechanisms and, thus, better devices or platforms that can recapitulate human cardiac development. The discovery of human pluripotent stem cells has substantially reduced the dependence on animal models. Recent advances in stem cell biology, genetic editing, omics, microfluidics, and sensor technologies have further enabled remarkable progress in the development of in vitro platforms with increased fidelity and efficiency. In this review, we provide an overview of advancements in in vitro cardiac development platforms, with a particular focus on technological innovation. We categorize these platforms into four areas: two-dimensional solid substrate cultures, engineered substrate architectures that enhance cellular functions, cardiac organoids, and embryos/explants-on-chip models. We conclude by addressing current limitations and presenting future perspectives.

Gelatin Methacryloyl (GelMA)-Based Biomaterial Inks: Process Science for 3D/4D Printing and Current Status

Tissue engineering for injured tissue replacement and regeneration has been a subject of investigation over the last 30 years, and there has been considerable interest in using additive manufacturing to achieve these goals. Despite such efforts, many key questions remain unanswered, particularly in the area of biomaterial selection for these applications as well as quantitative understanding of the process science. The strategic utilization of biological macromolecules provides a versatile approach to meet diverse requirements in 3D printing, such as printability, buildability, and biocompatibility. These molecules play a pivotal role in both physical and chemical cross-linking processes throughout the biofabrication, contributing significantly to the overall success of the 3D printing process. Among the several bioprintable materials, gelatin methacryloyl (GelMA) has been widely utilized for diverse tissue engineering applications, with some degree of success. In this context, this review will discuss the key bioengineering approaches to identify the gelation and cross-linking strategies that are appropriate to control the rheology, printability, and buildability of biomaterial inks. This review will focus on the GelMA as the structural (scaffold) biomaterial for different tissues and as a potential carrier vehicle for the transport of living cells as well as their maintenance and viability in the physiological system. Recognizing the importance of printability toward shape fidelity and biophysical properties, a major focus in this review has been to discuss the qualitative and quantitative impact of the key factors, including microrheological, viscoelastic, gelation, shear thinning properties of biomaterial inks, and printing parameters, in particular, reference to 3D extrusion printing of GelMA-based biomaterial inks. Specifically, we emphasize the different possibilities to regulate mechanical, swelling, biodegradation, and cellular functionalities of GelMA-based bio(material) inks, by hybridization techniques, including different synthetic and natural biopolymers, inorganic nanofillers, and microcarriers. At the close, the potential possibility of the integration of experimental data sets and artificial intelligence/machine learning approaches is emphasized to predict the printability, shape fidelity, or biophysical properties of GelMA bio(material) inks for clinically relevant tissues.

Molecular insights into the proteomic composition of porcine treated dentin matrix

Background

Human-treated dentin matrix (hTDM) has recently been studied as a natural extracellular matrix-based biomaterial for dentin pulp regeneration. However, porcine-treated dentin matrix (pTDM) is a potential alternative scaffold due to limited availability. However, there is a dearth of information regarding the protein composition and underlying molecular mechanisms of pTDM.Methods: hTDM and pTDM were fabricated using human and porcine teeth, respectively, and their morphological characteristics were examined using scanning electron microscopy. Stem cells derived from human exfoliated deciduous teeth (SHEDs) were isolated and characterized using flow cytometry and multilineage differentiation assays. SHEDs were cultured in three-dimensional environments with hTDM, pTDM, or biphasic hydroxyapatite/tricalcium phosphate. The expression of odontogenesis markers in SHEDs were assessed using real-time polymerase chain reaction and immunochemical staining. Subsequently, SHEDs/TDM and SHEDs/HA/TCP complexes were transplanted subcutaneously into nude mice. The protein composition of pTDM was analyzed using proteomics and compared to previously published data on hTDM.Results: pTDM and hTDM elicited comparable upregulation of odontogenesis-related genes and proteins in SHEDs. Furthermore, both demonstrated the capacity to stimulate root-related tissue regeneration in vivo. Proteomic analysis revealed the presence of 278 protein groups in pTDM, with collagens being the most abundant. Additionally, pTDM and hTDM shared 58 identical proteins, which may contribute to their similar abilities to induce odontogenesis.

Conclusions

Both hTDM and pTDM exhibit comparable capabilities in inducing odontogenesis, potentially owing to their distinctive bioactive molecular networks.

The trend of allogeneic tendon decellularization: literature review

Tendon injuries repair is a significant burden for orthopaedic surgeons. Finding a proper graft material to repair tendon is one of the main challenges in orthopaedics, for which the requirement of substitute for tendon repair would be different for each clinical application. Among biological scaffolds, the use of decellularized tendon increasingly represents an interesting approach to treat tendon injuries and several articles have investigated the approaches of tendon decellularization. To understand the outcomes of the the approaches of tendon decellularization on effect of tendon transplantation, a literature review was performed. This review was conducted by searching in Pubmed and Embase and 64 studies were included in this study. The findings revealed that the common approaches to decellularize tendon include chemical, physical, and enzymatic decellularization methods or their combination. With the development of tissue engineering, researchers also put forward new theories such as automatic acellular machine, 3D printing technology to manufacture acellular scaffold.

Decellularized extracellular matrix biomaterials for regenerative therapies: Advances, challenges and clinical prospects

Tissue engineering and regenerative medicine have shown potential in the repair and regeneration of tissues and organs via the use of engineered biomaterials and scaffolds. However, current constructs face limitations in replicating the intricate native microenvironment and achieving optimal regenerative capacity and functional recovery. To address these challenges, the utilization of decellularized tissues and cell-derived extracellular matrix (ECM) has emerged as a promising approach. These biocompatible and bioactive biomaterials can be engineered into porous scaffolds and grafts that mimic the structural and compositional aspects of the native tissue or organ microenvironment, both in vitro and in vivo. Bioactive dECM materials provide a unique tissue-specific microenvironment that can regulate and guide cellular processes, thereby enhancing regenerative therapies. In this review, we explore the emerging frontiers of decellularized tissue-derived and cell-derived biomaterials and bio-inks in the field of tissue engineering and regenerative medicine. We discuss the need for further improvements in decellularization methods and techniques to retain structural, biological, and physicochemical characteristics of the dECM products in a way to mimic native tissues and organs. This article underscores the potential of dECM biomaterials to stimulate in situ tissue repair through chemotactic effects for the development of growth factor and cell-free tissue engineering strategies. The article also identifies the challenges and opportunities in developing sterilization and preservation methods applicable for decellularized biomaterials and grafts and their translation into clinical products.

Hydrogels for the Treatment of Myocardial Infarction: Design and Therapeutic Strategies

Cardiovascular diseases (CVDs) have become the leading global burden of diseases in recent years and are the primary cause of human mortality and loss of healthy life expectancy. Myocardial infarction (MI) is the top cause of CVDs-related deaths, and its incidence is increasing worldwide every year. Recently, hydrogels have garnered great interest from researchers as a promising therapeutic option for cardiac tissue repair after MI. This is due to their excellent properties, including biocompatibility, mechanical properties, injectable properties, anti-inflammatory properties, antioxidant properties, angiogenic properties, and conductive properties. This review discusses the advantages of hydrogels as a novel treatment for cardiac tissue repair after MI. The design strategies of various hydrogels in MI treatment are then summarized, and the latest research progress in the field is classified. Finally, the future perspectives of this booming field are also discussed at the end of this review.

Biomimetic cryogel promotes the repair of osteoporotic bone defects through altering the ROS niche via down-regulating the ROMO1

Osteoporosis is a systemic bone disease that is prone to fractures due to decreased bone density and bone quality, and delayed union or nonunion often occurs in osteoporotic fractures. Therefore, it is particularly important to develop tissue engineering materials to promote osteoporotic fracture healing. In this study, a series of biomimetic cryogels prepared from the decellularized extracellular matrix (dECM), methacrylate gelatin (GelMA), and carboxymethyl chitosan (CMCS) via unidirectional freezing, photo- and genipin crosslinking were applied for the regeneration of osteoporotic fractures. Specifically, dECM extracted from normal or osteoporotic rats was applied for the preparation of the cryogels, named as GC-Normal dECM or GC-OVX dECM, respectively. It was verified that the GC-Normal dECM demonstrated superior performance in promoting the proliferation of BMSCs isolated from osteoporotic rats (OVX-BMSCs), and the differentiation of OVX-BMSCs into osteoblasts both in vitro and in vivo. RNA sequencing and further verifications confirmed that GC-Normal dECM cryogel could scavenge the intracellular reactive oxygen species (ROS) in OVX-BMSCs to accelerate the regeneration of osteoporotic fracture by down-regulating the reactive oxygen species modulator 1 (Romo1). The results indicated that by regulating the ROS niche of OVX-BMSCs, biomimetic the GC-Normal dECM cryogel was expected to be a clinical candidate for repairing osteoporotic bone defects.

The Current State of Extracellular Matrix Therapy for Ischemic Heart Disease

The extracellular matrix (ECM) is a three-dimensional, acellular network of diverse structural and nonstructural proteins embedded within a gel-like ground substance composed of glycosaminoglycans and proteoglycans. The ECM serves numerous roles that vary according to the tissue in which it is situated. In the myocardium, the ECM acts as a collagen-based scaffold that mediates the transmission of contractile signals, provides means for paracrine signaling, and maintains nutritional and immunologic homeostasis. Given this spectrum, it is unsurprising that both the composition and role of the ECM has been found to be modulated in the context of cardiac pathology. Myocardial infarction (MI) provides a familiar example of this; the ECM changes in a way that is characteristic of the progressive phases of post-infarction healing. In recent years, this involvement in infarct pathophysiology has prompted a search for therapeutic targets: if ECM components facilitate healing, then their manipulation may accelerate recovery, or even reverse pre-existing damage. This possibility has been the subject of numerous efforts involving the integration of ECM-based therapies, either derived directly from biologic sources or bioengineered sources, into models of myocardial disease. In this paper, we provide a thorough review of the published literature on the use of the ECM as a novel therapy for ischemic heart disease, with a focus on biologically derived models, of both the whole ECM and the components thereof.

dECM restores macrophage immune homeostasis and alleviates iron overload to promote DTPI healing

Due to its highly insidious and rapid progression, deep tissue pressure injury (DTPI) is a clinical challenge. Our previous study found that DTPI may be a skeletal muscle injury dominated by macrophage immune dysfunction due to excessive iron accumulation. Decellularized extracellular matrix (dECM) hydrogel promotes skeletal muscle injury repair. However, its role in polarizing macrophages and regulating iron metabolism in DTPI remains unclear. Here, porcine dECM hydrogel was prepared, and its therapeutic function and mechanism in repairing DTPI were investigated. The stimulus of dECM hydrogel toward RAW264.7 cells resulted in a significantly higher percentage of CD206+ macrophages and notably decreased intracellular divalent iron levels. In mice DTPI model, dECM hydrogel treatment promoted M1 to M2 macrophage conversion, improved iron metabolism and reduced oxidative stress in the early stage of DTPI. In the remodeling phase, the dECM hydrogel remarkably enhanced revascularization and accelerated skeletal muscle repair. Furthermore, the immunomodulation of dECM hydrogels in vivo was mainly involved in the P13k/Akt signaling pathway, as revealed by GO and KEGG pathway analysis, which may ameliorate the iron deposition and promote the healing of DTPI. Our findings indicate that dECM hydrogel is promising in skeletal muscle repair, inflammation resolution and tissue injury healing by effectively restoring macrophage immune homeostasis and normalizing iron metabolism.

Decellularized heart extracellular matrix alleviates activation of hiPSC-derived cardiac fibroblasts

Human induced pluripotent stem cell derived cardiac fibroblasts (hiPSC-CFs) play a critical role in modeling human cardiovascular diseases in vitro. However, current culture substrates used for hiPSC-CF differentiation and expansion, such as Matrigel and tissue culture plastic (TCPs), are tissue mismatched and may provide pathogenic cues. Here, we report that hiPSC-CFs differentiated on Matrigel and expanded on tissue culture plastic (M-TCP-iCFs) exhibit transcriptomic hallmarks of activated fibroblasts limiting their translational potential. To alleviate pathogenic activation of hiPSC-CFs, we utilized decellularized extracellular matrix derived from porcine heart extracellular matrix (HEM) to provide a biomimetic substrate for improving hiPSC-CF phenotypes. We show that hiPSC-CFs differentiated and expanded on HEM (HEM-iCFs) exhibited reduced expression of hallmark activated fibroblast markers versus M-TCP-iCFs while retaining their cardiac fibroblast phenotype. HEM-iCFs also maintained a reduction in expression of hallmark genes associated with pathogenic fibroblasts when seeded onto TCPs. Further, HEM-iCFs more homogenously integrated into an hiPSC-derived cardiac organoid model, resulting in improved cardiomyocyte sarcomere development. In conclusion, HEM provides an improved substrate for the differentiation and propagation of hiPSC-CFs for disease modeling.

Recent advances in nanotechnology for the treatment of fungal keratitis

Fungal keratitis (FK) is a serious pathogenic disease usually associated with serious ocular complications. The current mainstay of treatment for FK is topical eye drops; however, poor corneal penetration, low bioavailability of the drug and the need to administer high and frequent doses due to the presence of an effective clearance mechanism in the eye result in poor patient compliance. Nanocarriers can extend the duration of drug action through sustained and controlled release of the drug, protect the drug from ocular enzymes and help overcome ocular barriers. In this review, we discussed the mechanisms of action of antifungal drugs, the theoretical basis for the treatment of FK, and recent advances in the clinical treatment of FK. We have summarized the results of research into the most promising nanocarriers for ocular drug delivery and highlight their efficacy and safety in the therapy.

Self-healing hydrogels based on biological macromolecules in wound healing: A review

The complete healing of skin wounds has been a challenge in clinical treatment. Self-healing hydrogels are special hydrogels formed by distinctive physicochemically reversible bonds, and they are considered promising biomaterials in the biomedical field owing to their inherently good drug-carrying capacity as well as self-healing and repair abilities. Moreover, natural polymeric materials have received considerable attention in skin tissue engineering owing to their low cytotoxicity, low immunogenicity, and excellent biodegradation rates. In this paper, we review recent advances in the design of self-healing hydrogels based on natural polymers for skin-wound healing applications. First, we outline a variety of natural polymers that can be used to construct self-healing hydrogel systems and highlight the advantages and disadvantages of different natural polymers. We then describe the principle of self-healing hydrogels in terms of two different crosslinking mechanisms-physical and chemical-and dissect their performance characteristics based on the practical needs of skin-trauma applications. Next, we outline the biological mechanisms involved in the healing of skin wounds and describe the current application strategies for self-healing hydrogels based on these mechanisms. Finally, we analyze and summarize the challenges and prospects of natural-material-based self-healing hydrogels for skin applications.

Injectable Xenogeneic Dental Pulp Decellularized Extracellular Matrix Hydrogel Promotes Functional Dental Pulp Regeneration

The present challenge in dental pulp tissue engineering scaffold materials lies in the development of tissue-specific scaffolds that are conducive to an optimal regenerative microenvironment and capable of accommodating intricate root canal systems. This study utilized porcine dental pulp to derive the decellularized extracellular matrix (dECM) via appropriate decellularization protocols. The resultant dECM was dissolved in an acid pepsin solution to form dECM hydrogels. The analysis encompassed evaluating the microstructure and rheological properties of dECM hydrogels and evaluated their biological properties, including in vitro cell viability, proliferation, migration, tube formation, odontogenic, and neurogenic differentiation. Gelatin methacrylate (GelMA) hydrogel served as the control. Subsequently, hydrogels were injected into treated dentin matrix tubes and transplanted subcutaneously into nude mice to regenerate dental pulp tissue in vivo. The results showed that dECM hydrogels exhibited exceptional injectability and responsiveness to physiological temperature. It supported the survival, odontogenic, and neurogenic differentiation of dental pulp stem cells in a 3D culture setting. Moreover, it exhibited a superior ability to promote cell migration and angiogenesis compared to GelMA hydrogel in vitro. Additionally, the dECM hydrogel demonstrated the capability to regenerate pulp-like tissue with abundant blood vessels and a fully formed odontoblast-like cell layer in vivo. These findings highlight the potential of porcine dental pulp dECM hydrogel as a specialized scaffold material for dental pulp regeneration.

Papain-Based Solubilization of Decellularized Extracellular Matrix for the Preparation of Bioactive, Thermosensitive Pregels

Solubilized, gel-forming decellularized extracellular matrix (dECM) is used in a wide range of basic and translational research and due to its inherent bioactivity can promote structural and functional tissue remodeling. The animal-derived protease pepsin has become the standard proteolytic enzyme for the solubilization of almost all types of collagen-based dECM. In this study, pepsin was compared with papain, α-amylase, and collagenase for their potential to solubilize porcine liver dECM. Maximum preservation of bioactive components and native dECM properties was used as a decisive criterion for further application of the enzymes, with emphasis on minimal destruction of the protein structure and maintained capacity for physical thermogelation at neutral pH. The solubilized dECM digests, and/or their physically gelled hydrogels were characterized for their rheological properties, gelation kinetics, GAG content, proteomic composition, and growth factor profile. This study highlights papain as a plant-derived enzyme that can serve as a cost-effective alternative to animal-derived pepsin for the efficient solubilization of dECM. The resulting homogeneous papain-digested dECM preserved its thermally triggered gelation properties similar to pepsin digests, and the corresponding dECM hydrogels demonstrated their enhanced bioadhesiveness in single-cell force spectroscopy experiments with fibroblasts. The viability and proliferation of human HepaRG cells on dECM gels were similar to those on pure rat tail collagen type I gels. Papain is not only highly effective and economically attractive for dECM solubilization but also particularly interesting when digesting human-tissue-derived dECM for regenerative applications, where animal-derived materials are to be avoided.

Hydrogels for Cardiac Restorative Support: Relevance of Gelation Mechanisms for Prospective Clinical Use

PURPOSE OF REVIEW

Cardiac tissue regenerative strategies have gained much traction over the years, in particular those utilizing hydrogels. With our review, and with special focus on supporting post-myocardial infarcted tissue, we aim to provide insights in determining crucial design considerations of a hydrogel and the implications these could have for future clinical use.

RECENT FINDINGS

To date, two hydrogel delivery strategies are being explored, cardiac injection or patch, to treat myocardial infarction. Recent advances have demonstrated that the mechanism by which a hydrogel is gelated (i.e., physically or chemically cross-linked) not only impacts the biocompatibility, mechanical properties, and chemical structure, but also the route of delivery of the hydrogel and thus its effect on cardiac repair. With regard to cardiac regeneration, various hydrogels have been developed with the ability to function as a delivery system for therapeutic strategies (e.g., drug and stem cells treatments), as well as a scaffold to guide cardiac tissue regeneration following myocardial infarction. However, these developments remain within the experimental and pre-clinical realm and have yet to transition towards the clinical setting.

Localized delivery of anti-inflammatory agents using extracellular matrix-nanostructured lipid carriers hydrogel promotes cardiac repair post-myocardial infarction

A challenge in treating cardiac injury is the low heart-specificity of the drugs. Nanostructured lipid carriers (NLCs) are a relatively new format of lipid nanoparticles which have been used to deliver RNA and drugs. However, lipid nanoparticles exhibit higher affinity to the liver than the heart. To improve the delivery efficiency of NLCs into the heart, NLCs can be embedded into a scaffold and be locally released. In this study, a cardiac extracellular matrix (ECM) hydrogel-NLC composite was developed as a platform for cardiac repair. ECM-NLC composite gels at physiological conditions and releases payloads into the heart over weeks. ECM-NLC hydrogel carrying colchicine, an anti-inflammation agent, improved cardiac repair after myocardial infarction in mice. Transcriptome analysis indicated that Egfr downstream effectors participated in ECM-NLC-colchicine induced heart repair. In conclusion, ECM-NLC hydrogel is a potential platform for sustained and localized delivery of biomolecules into the heart, and loading appropriate medicines further increases the therapeutic efficacy of ECM-NLC hydrogel for cardiovascular diseases.

In need of age-appropriate cardiac models: Impact of cell age on extracellular matrix therapy outcomes

Aging is the main risk factor for cardiovascular disease (CVD). As the world's population ages rapidly and CVD rates rise, there is a growing need for physiologically relevant models of aging hearts to better understand cardiac aging. Translational research relies heavily on young animal models; however, these models correspond to early ages in human life, therefore cannot fully capture the pathophysiology of age-related CVD. Here, we first investigated the transcriptomic and proteomic changes that occur with human cardiac aging. We then chronologically aged human induced pluripotent stem cell-derived cardiomyocytes (iCMs) and showed that 14-month-old iCMs exhibited a similar aging profile to the human CMs and recapitulated age-related disease hallmarks. Using aged iCMs, we studied the effect of cell age on the young extracellular matrix (ECM) therapy, an emerging approach for myocardial infarction (MI) treatment and prevention. Young ECM decreased oxidative stress, improved survival, and post-MI beating in aged iCMs. In the absence of stress, young ECM improved beating and reversed aging-associated expressions in 3-month-old iCMs while causing the opposite effect on 14-month-old iCMs. The same young ECM treatment surprisingly increased SASP and impaired beating in advanced aged iCMs. Overall, we showed that young ECM therapy had a positive effect on post-MI recovery; however, cell age was determinant in the treatment outcomes without any stress conditions. Therefore, "one-size-fits-all" approaches to ECM treatments fail, and cardiac tissue engineered models with age-matched human iCMs are valuable in translational basic research for determining the appropriate treatment, particularly for the elderly.

Recent advances in soluble decellularized extracellular matrix for heart tissue engineering and organ modeling

Despite the advent of tissue engineering (TE) for the remodeling, restoring, and replacing damaged cardiovascular tissues, the progress is hindered by the optimal mechanical and chemical properties required to induce cardiac tissue-specific cellular behaviors including migration, adhesion, proliferation, and differentiation. Cardiac extracellular matrix (ECM) consists of numerous structural and functional molecules and tissue-specific cells, therefore it plays an important role in stimulating cell proliferation and differentiation, guiding cell migration, and activating regulatory signaling pathways. With the improvement and modification of cell removal methods, decellularized ECM (dECM) preserves biochemical complexity, and bio-inductive properties of the native matrix and improves the process of generating functional tissue. In this review, we first provide an overview of the latest advancements in the utilization of dECM in in vitro model systems for disease and tissue modeling, as well as drug screening. Then, we explore the role of dECM-based biomaterials in cardiovascular regenerative medicine (RM), including both invasive and non-invasive methods. In the next step, we elucidate the engineering and material considerations in the preparation of dECM-based biomaterials, namely various decellularization techniques, dECM sources, modulation, characterizations, and fabrication approaches. Finally, we discuss the limitations and future directions in fabrication of dECM-based biomaterials for cardiovascular modeling, RM, and clinical translation.

Dual human iPSC-derived cardiac lineage cell-seeding extracellular matrix patches promote regeneration and long-term repair of infarcted hearts

Human pluripotent stem cell-derived cardiovascular progenitor cells (hCVPCs) and cardiomyocytes (hCMs) possess therapeutic potential for infarcted hearts; however, their efficacy needs to be enhanced. Here we tested the hypotheses that the combination of decellularized porcine small intestinal submucosal extracellular matrix (SIS-ECM) with hCVPCs, hCMs, or dual of them (Mix, 1:1) could provide better therapeutic effects than the SIS alone, and dual hCVPCs with hCMs would exert synergic effects in cardiac repair. The data showed that the SIS patch well supported the growth of hCVPCs and hCMs. Epicardially implanted SIS-hCVPC, SIS-hCM, or SIS-Mix patches at 7-day post-myocardial infarction significantly ameliorated functional worsening, ventricular dilation and scar formation at 28- and 90-day post-implantation in C57/B6 mice, whereas the SIS only mildly improved function at 90-day post-implantation. Moreover, the SIS and SIS-cell patches improved vascularization and suppressed MI-induced cardiomyocyte hypertrophy and expression of Col1 and Col3, but only the SIS-hCM and the SIS-Mix patches increased the ratio of collagen III/I fibers in the infarcted hearts. Further, the SIS-cell patches stimulated cardiomyocyte proliferation via paracrine action. Notably, the SIS-Mix had better improvements in cardiac function and structure, engraftments, and cardiomyocyte proliferation. Proteomic analysis showed distinct biological functions of exclusive proteins secreted from hCVPCs and hCMs, and more exclusive proteins secreted from co-cultivated hCVPCs and hCMs than mono-cells involving in various functional processes essential for infarct repair. These findings are the first to demonstrate the efficacy and mechanisms of mono- and dual-hCVPC- and hCM-seeding SIS-ECM for repair of infarcted hearts based on the side-by-side comparison.

3D printing of thick myocardial tissue constructs with anisotropic myofibers and perfusable vascular channels

Engineering of myocardial tissues has become a promising therapeutic strategy for treating myocardial infarction (MI). However, a significant challenge remains in generating clinically relevant myocardial tissues that possess native microstructural characteristics and fulfill the requirements for implantation within the human body. In this study, a thick 3D myocardial construct with anisotropic myofibers and perfusable branched vascular channels is created with clinically relevant dimensions using a customized beam-scanning stereolithography printing technique. To obtain tissue-specific matrix niches, a decellularized extracellular matrix microfiber-reinforced gelatin-based bioink is developed. The bioink plays a crucial role in facilitating the precise manufacturing of a hierarchical microstructure, enabling us to better replicate the physiological characteristics of the native myocardial tissue matrix in terms of structure, biomechanics, and bioactivity. Through the integration of the tailored bioink with our printing method, we demonstrate a biomimetic architecture, appropriate biomechanical properties, vascularization, and improved functionality of induced pluripotent stem cell-derived cardiomyocytes in the thick tissue construct in vitro. This work not only offers a novel and effective means to generate biomimetic heart tissue in vitro for the treatment of MI, but also introduces a potential methodology for creating clinically relevant tissue products to aid in other complex tissue/organ regeneration and disease model applications.

Advances in the design, generation, and application of tissue-engineered myocardial equivalents

Due to the limited regenerative ability of cardiomyocytes, the disabling irreversible condition of myocardial failure can only be treated with conservative and temporary therapeutic approaches, not able to repair the damage directly, or with organ transplantation. Among the regenerative strategies, intramyocardial cell injection or intravascular cell infusion should attenuate damage to the myocardium and reduce the risk of heart failure. However, these cell delivery-based therapies suffer from significant drawbacks and have a low success rate. Indeed, cardiac tissue engineering efforts are directed to repair, replace, and regenerate native myocardial tissue function. In a regenerative strategy, biomaterials and biomimetic stimuli play a key role in promoting cell adhesion, proliferation, differentiation, and neo-tissue formation. Thus, appropriate biochemical and biophysical cues should be combined with scaffolds emulating extracellular matrix in order to support cell growth and prompt favorable cardiac microenvironment and tissue regeneration. In this review, we provide an overview of recent developments that occurred in the biomimetic design and fabrication of cardiac scaffolds and patches. Furthermore, we sift in vitro and in situ strategies in several preclinical and clinical applications. Finally, we evaluate the possible use of bioengineered cardiac tissue equivalents as in vitro models for disease studies and drug tests.

Characterization of Bioinks Prepared via Gelifying Extracellular Matrix from Decellularized Porcine Myocardia

Since the emergence of 3D bioprinting technology, both synthetic and natural materials have been used to develop bioinks for producing cell-laden cardiac grafts. To this end, extracellular-matrix (ECM)-derived hydrogels can be used to develop scaffolds that closely mimic the complex 3D environments for cell culture. This study presents a novel cardiac bioink based on hydrogels exclusively derived from decellularized porcine myocardium loaded with human-bone-marrow-derived mesenchymal stromal cells. Hence, the hydrogel can be used to develop cell-laden cardiac patches without the need to add other biomaterials or use additional crosslinkers. The scaffold ultrastructure and mechanical properties of the bioink were characterized to optimize its production, specifically focusing on the matrix enzymatic digestion time. The cells were cultured in 3D within the developed hydrogels to assess their response. The results indicate that the hydrogels fostered inter-cell and cell-matrix crosstalk after 1 week of culture. In conclusion, the bioink developed and presented in this study holds great potential for developing cell-laden customized patches for cardiac repair.

Human pluripotent stem cell-based models of heart development and disease

The heart is a complex organ composed of distinct cell types, such as cardiomyocytes, cardiac fibroblasts, endothelial cells, smooth muscle cells, neuronal cells and immune cells. All these cell types contribute to the structural, electrical and mechanical properties of the heart. Genetic manipulation and lineage tracing studies in mice have been instrumental in gaining critical insights into the networks regulating cardiac cell lineage specification, cell fate and plasticity. Such knowledge has been of fundamental importance for the development of efficient protocols for the directed differentiation of pluripotent stem cells (PSCs) in highly specialized cardiac cell types. In this review, we summarize the evolution and current advances in protocols for cardiac subtype specification, maturation, and assembly in cardiac microtissues and organoids.

Application of biomedical materials in the diagnosis and treatment of myocardial infarction

Myocardial infarction (MI) is a cardiovascular emergency and the leading cause of death worldwide. Inflammatory and immune responses are initiated immediately after MI, leading to myocardial death, scarring, and ventricular remodeling. Current therapeutic approaches emphasize early restoration of ischemic myocardial reperfusion, but there is no effective treatment for the pathological changes of infarction. Biomedical materials development has brought new hope for MI diagnosis and treatment. Biomedical materials, such as cardiac patches, hydrogels, nano biomaterials, and artificial blood vessels, have played an irreplaceable role in MI diagnosis and treatment. They improve the accuracy and efficacy of MI diagnosis and offer further possibilities for reducing inflammation, immunomodulation, inhibiting fibrosis, and cardiac regeneration. This review focuses on the advances in biomedical materials applications in MI diagnosis and treatment. The current studies are outlined in terms of mechanisms of action and effects. It is addressed how biomedical materials application can lessen myocardial damage, encourage angiogenesis, and enhance heart function. Their clinical transformation value and application prospect are discussed.

Extracellular Matrix/Glycopeptide Hybrid Hydrogel as an Immunomodulatory Niche for Endogenous Cardiac Repair after Myocardial Infarction

The treatment of myocardial infarction (MI) remains a substantial challenge due to excessive inflammation, massive cell death, and restricted regenerative potential, leading to maladaptive healing process and eventually heart failure. Current strategies of regulating inflammation or improving cardiac tissue regeneration have limited success. Herein, a hybrid hydrogel coassembled by acellular cardiac extracellular matrix (ECM) and immunomodulatory glycopeptide is developed for endogenous tissue regeneration after MI. The hydrogel constructs a niche recapitulating the architecture of native ECM for attracting host cell homing, controlling macrophage differentiation via glycopeptide unit, and promoting endotheliocyte proliferation by enhancing the macrophage-endotheliocyte crosstalk, which coordinate the innate healing mechanism for cardiac tissue regeneration. In a rodent MI model, the hybrid hydrogel successfully orchestrates a proreparative response indicated by enhanced M2 macrophage polarization, increased angiogenesis, and improved cardiomyocyte survival, which alleviates infarct size, improves wall thicknesses, and enhances cardiac contractility. Furthermore, the safety and effectiveness of the hydrogel are demonstrated in a porcine MI model, wherein proteomics verifies the regulation of immune response, proangiogenesis, and accelerated healing process. Collectively, the injectable composite hydrogel serving as an immunomodulatory niche for promoting cell homing and proliferation, inflammation modulation, tissue remodeling, and function restoration provides an effective strategy for endogenous cardiac repair.

An Experimental and Numerical Investigation of Cardiac Tissue-Patch Interrelation

Tissue engineered cardiac patches have great potential as a regenerative therapy for myocardial infarction. Yet, the mutual interaction of cardiac patches with healthy tissue has not been completely understood. Here, we investigated the impact of acellular and cellular patches on a beating two-dimensional (2D) cardiac cell layer, and the effect of the beating of this layer on the cells encapsulated in the patch. We cultured human-induced pluripotent stem cell-derived cardiomyocytes (iCMs) on a coverslip and placed gelatin methacryloyl hydrogel alone or with encapsulated iCMs to create acellular and cellular patches, respectively. When the acellular patch was placed on the cardiac cell layer, the beating characteristics and Ca+2 handling properties reduced, whereas placing the cellular patch restored these characteristics. To better understand the effects of the cyclic contraction and relaxation induced by the beating cardiac cell layer on the patch placed on top of it, a simulation model was developed, and the calculated strain values were in agreement with the values measured experimentally. Moreover, this dynamic culture induced by the beating 2D iCM layer on the iCMs encapsulated in the cellular patch improved their beating velocity and frequency. Additionally, the encapsulated iCMs were observed to be coupled with the underlying beating 2D iCM layer. Overall, this study provides a detailed investigation on the mutual relationship of acellular/cellular patches with the beating 2D iCM layer, understanding of which would be valuable for developing more advanced cardiac patches.

Control of the post-infarct immune microenvironment through biotherapeutic and biomaterial-based approaches

Ischemic heart failure (IHF) is a leading cause of morbidity and mortality worldwide, for which heart transplantation remains the only definitive treatment. IHF manifests from myocardial infarction (MI) that initiates tissue remodeling processes, mediated by mechanical changes in the tissue (loss of contractility, softening of the myocardium) that are interdependent with cellular mechanisms (cardiomyocyte death, inflammatory response). The early remodeling phase is characterized by robust inflammation that is necessary for tissue debridement and the initiation of repair processes. While later transition toward an immunoregenerative function is desirable, functional reorientation from an inflammatory to reparatory environment is often lacking, trapping the heart in a chronically inflamed state that perpetuates cardiomyocyte death, ventricular dilatation, excess fibrosis, and progressive IHF. Therapies can redirect the immune microenvironment, including biotherapeutic and biomaterial-based approaches. In this review, we outline these existing approaches, with a particular focus on the immunomodulatory effects of therapeutics (small molecule drugs, biomolecules, and cell or cell-derived products). Cardioprotective strategies, often focusing on immunosuppression, have shown promise in pre-clinical and clinical trials. However, immunoregenerative therapies are emerging that often benefit from exacerbating early inflammation. Biomaterials can be used to enhance these therapies as a result of their intrinsic immunomodulatory properties, parallel mechanisms of action (e.g., mechanical restraint), or by enabling cell or tissue-targeted delivery. We further discuss translatability and the continued progress of technologies and procedures that contribute to the bench-to-bedside development of these critically needed treatments.

Decellularized Extracellular Matrix: The Role of This Complex Biomaterial in Regeneration

Organ transplantation is understood as a technique where an organ from a donor patient is transferred to a recipient patient. This practice gained strength in the 20th century and ensured advances in areas of knowledge such as immunology and tissue engineering. The main problems that comprise the practice of transplants involve the demand for viable organs and immunological aspects related to organ rejection. In this review, we address advances in tissue engineering for reversing the current challenges of transplants, focusing on the possible use of decellularized tissues in tissue engineering. We address the interaction of acellular tissues with immune cells, especially macrophages and stem cells, due to their potential use in regenerative medicine. Our goal is to exhibit data that demonstrate the use of decellularized tissues as alternative biomaterials that can be applied clinically as partial or complete organ substitutes.

Therapeutic angiogenesis based on injectable hydrogel for protein delivery in ischemic heart disease

Ischemic heart disease (IHD) remains the leading cause of death and disability worldwide and leads to myocardial necrosis and negative myocardial remodeling, ultimately leading to heart failure. Current treatments include drug therapy, interventional therapy, and surgery. However, some patients with severe diffuse coronary artery disease, complex coronary artery anatomy, and other reasons are unsuitable for these treatments. Therapeutic angiogenesis stimulates the growth of the original blood vessels by using exogenous growth factors to generate more new blood vessels, which provides a new treatment for IHD. However, direct injection of these growth factors can cause a short half-life and serious side effects owing to systemic spread. Therefore, to overcome this problem, hydrogels have been developed for temporally and spatially controlled delivery of single or multiple growth factors to mimic the process of angiogenesis in vivo. This paper reviews the mechanism of angiogenesis, some important bioactive molecules, and natural and synthetic hydrogels currently being applied for bioactive molecule delivery to treat IHD. Furthermore, the current challenges of therapeutic angiogenesis in IHD and its potential solutions are discussed to facilitate real translation into clinical applications in the future.

Cells and Materials for Cardiac Repair and Regeneration

After more than 20 years following the introduction of regenerative medicine to address the problem of cardiac diseases, still questions arise as to the best cell types and materials to use to obtain effective clinical translation. Now that it is definitively clear that the heart does not have a consistent reservoir of stem cells that could give rise to new myocytes, and that there are cells that could contribute, at most, with their pro-angiogenic or immunomodulatory potential, there is fierce debate on what will emerge as the winning strategy. In this regard, new developments in somatic cells' reprogramming, material science and cell biophysics may be of help, not only for protecting the heart from the deleterious consequences of aging, ischemia and metabolic disorders, but also to boost an endogenous regeneration potential that seems to be lost in the adulthood of the human heart.

Extracellular matrix-derived scaffolds in constructing artificial ovaries for ovarian failure: a systematic methodological review

STUDY QUESTION

What is the current state-of-the-art methodology assessing decellularized extracellular matrix (dECM)-based artificial ovaries for treating ovarian failure?

SUMMARY ANSWER

Preclinical studies have demonstrated that decellularized scaffolds support the growth of ovarian somatic cells and follicles both in vitro and in vivo.

WHAT IS KNOWN ALREADY

Artificial ovaries are a promising approach for rescuing ovarian function. Decellularization has been applied in bioengineering female reproductive tract tissues. However, decellularization targeting the ovary lacks a comprehensive and in-depth understanding.

STUDY DESIGN SIZE DURATION

PubMed, Embase, Web of Science, and the Cochrane Central Register of Controlled Trials were searched from inception until 20 October 2022 to systematically review all studies in which artificial ovaries were constructed using decellularized extracellular matrix scaffolds. The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol.

PARTICIPANTS/MATERIALS SETTING METHODS

Two authors selected studies independently based on the eligibility criteria. Studies were included if decellularized scaffolds, regardless of their species origin, were seeded with ovarian cells or follicles. Review articles and meeting papers were removed from the search results, as were articles without decellularized scaffolds or recellularization or decellularization protocols, or control groups or ovarian cells.

MAIN RESULTS AND THE ROLE OF CHANCE

The search returned a total of 754 publications, and 12 papers were eligible for final analysis. The papers were published between 2015 and 2022 and were most frequently reported as coming from Iran. Detailed information on the decellularization procedure, evaluation method, and preclinical study design was extracted. In particular, we concentrated on the type and duration of detergent reagent, DNA and extracellular matrix detection methods, and the main findings on ovarian function. Decellularized tissues derived from humans and experimental animals were reported. Scaffolds loaded with ovarian cells have produced estrogen and progesterone, though with high variability, and have supported the growth of various follicles. Serious complications have not been reported.

LIMITATIONS REASONS FOR CAUTION

A meta-analysis could not be performed. Therefore, only data pooling was conducted. Additionally, the quality of some studies was limited mainly due to incomplete description of methods, which impeded specific data extraction and quality analysis. Several studies that used dECM scaffolds were performed or authored by the same research group with a few modifications, which might have biased our evaluation.

WIDER IMPLICATIONS OF THE FINDINGS

Overall, the decellularization-based artificial ovary is a promising but experimental choice for substituting insufficient ovaries. A generic and comparable standard should be established for the decellularization protocols, quality implementation, and cytotoxicity controls. Currently, decellularized materials are far from being clinically applicable to artificial ovaries.

STUDY FUNDING/COMPETING INTERESTS

This study was funded by the National Natural Science Foundation of China (Nos. 82001498 and 81701438). The authors have no conflicts of interest to declare.

TRIAL REGISTRATION NUMBER

This systematic review is registered with the International Prospective Register of Systematic Reviews (PROSPERO, ID CRD42022338449).

Biomimetic Extracellular Scaffolds by Microfluidic Superstructuring of Nanofibers

The extracellular matrix is a dynamic framework bearing chemical and morphological cues that support many cellular functions, and artificial analogs with well-defined chemistry are of great interest for biomedical applications. Herein, we describe hierarchical, extracellular-matrix-mimetic microgels, termed "superbundles" (SBs) composed of peptide amphiphile (PA) supramolecular nanofiber networks created using flow-focusing microfluidic devices. We explore the effects of altered flow rate ratio and PA concentration on the ability to create SBs and develop design rules for producing SBs with both cationic and anionic PA nanofibers and gelators. We demonstrate the morphological similarities of SBs to decellularized extracellular matrices and showcase their ability to encapsulate and retain proteinaceous cargos with a wide variety of isoelectric points. Finally, we demonstrate that the novel SB morphology does not affect the well-established biocompatibility of PA gels.