Hydrogels derived from demineralized and decellularized bone extracellular matrix

Incorporation of calcium phosphate cement into decellularized extracellular matrix enhances its bone regenerative properties

Decellularized extracellular matrix (dECM) hydrogels are engineered constructs that are widely-used in the field of regenerative medicine. However, the development of ECM-based hydrogels for bone tissue engineering requires enhancement in its osteogenic properties. For this purpose, we initially employed bone-derived dECM hydrogel (dECM-Hy) in combination with calcium phosphate cement (CPC) paste to improve the biological and structural properties of the dECM hydrogel. A decellularization protocol for bovine bone was developed to prepare dECM-Hy, and the mechanically-tuned dECM/CPC-Hy was built based on both rheological and mechanical characteristics. The dECM/CPC-Hy displayed a double swelling ratio and compressive strength. An interconnected structure with distinct hydroxyapatite crystals was evident in dECM/CPC-Hy. The expression levels of Alp, Runx2 and Ocn genes were upregulated in dECM/CPC-Hy compared to the dECM-Hy. A 14-day follow-up of the rats receiving subcutaneous implanted dECM-Hy, dECM/CPC-Hy and mesenchymal stem cells (MSCs)-embedded (dECM/CPC/MSCs-Hy) showed no toxicity, inflammatory factor expression or pathological changes. Radiography and computed tomography (CT) of the calvarial defects revealed new bone formation and elevated number of osteoblasts-osteocytes and osteons in dECM/CPC-Hy and dECM/CPC/MSCs-Hy compared to the control groups. These findings indicate that the dECM/CPC-Hy has substantial potential for bone tissue engineering.

Liver tissue engineering using decellularized scaffolds: Current progress, challenges, and opportunities

Liver transplantation represents the only definitive treatment for patients with end-stage liver disease. However, the shortage of liver donors provokes a dramatic gap between available grafts and patients on the waiting list. Whole liver bioengineering, an emerging field of tissue engineering, holds great potential to overcome this gap. This approach involves two main steps; the first is liver decellularization and the second is recellularization. Liver decellularization aims to remove cellular and nuclear materials from the organ, leaving behind extracellular matrices containing different structural proteins and growth factors while retaining both the vascular and biliary networks. Recellularization involves repopulating the decellularized liver with appropriate cells, theoretically from the recipient patient, to reconstruct the parenchyma, vascular tree, and biliary network. The aim of this review is to identify the major advances in decellularization and recellularization strategies and investigate obstacles for the clinical application of bioengineered liver, including immunogenicity of the designed liver extracellular matrices, the need for standardization of scaffold fabrication techniques, selection of suitable cell sources for parenchymal repopulation, vascular, and biliary tree reconstruction. In vivo transplantation models are also summarized for evaluating the functionality of bioengineered livers. Finally, the regulatory measures and future directions for confirming the safety and efficacy of bioengineered liver are also discussed. Addressing these challenges in whole liver bioengineering may offer new solutions to meet the demand for liver transplantation and improve patient outcomes.

Induction of osteogenic differentiation by the extracellular matrix of fetal bone tissues and adult cartilage

Decellularized cortical bone powder derived from adult animals has been shown to induce bone remodeling. Furthermore, it is increasingly evident that the extracellular matrix (ECM) within decellularized tissues differs depending on the source tissue and the age of the animal, leading to distinct effects on cells. In this study, we prepared powders from decellularized fetal and adult porcine bone tissues and conducted biological analyses to determine if the decellularized tissue could induce adipose-derived stem cell differentiation. Decellularized fetal tissues and adult cortical bone were converted into powder by cryomilling, but decellularized adult bone marrow and cartilage were not powdered through this process. In vitro assessments revealed that decellularized fetal tissues, decellularized adult cartilage extract, and decellularized fetal cartilage powder can induce osteoblast differentiation. This study suggests that decellularized fetal bone tissues and adult cartilage contain ECM components that can induce osteoblast differentiation. Additionally, it highlights the utility of decellularized fetal cartilage powder for bone reconstruction.

3D Bioprinted Tissue-Engineered Bone with Enhanced Mechanical Strength and Bioactivities: Accelerating Bone Defect Repair through Sequential Immunomodulatory Properties

In this study, a new-generation tissue-engineered bone capable of temporally regulating the immune response, balancing proinflammatory and anti-inflammatory activities, and facilitating bone regeneration and repair to address the challenges of delayed healing and nonunion in large-sized bone defects, is innovatively developed. Using the innovative techniques including multiphysics-assisted combined decellularization, side-chain biochemical modification, and sterile freeze-drying, a novel photocurable extracellular matrix hydrogel, methacrylated bone-derived decellularized extracellular matrix (bdECM-MA), is synthesized. After incorporating the bdECM-MA with silicon-substituted calcium phosphate and bone marrow mesenchymal stem cells, the tissue-engineered bone is fabricated through digital light processing 3D bioprinting. This study provides in vitro confirmation that the engineered bone maintains high cellular viability while achieving MPa-level mechanical strength. Moreover, this engineered bone exhibits excellent osteogenesis, angiogenesis, and immunomodulatory functions. One of the molecular mechanisms of the immunomodulatory function involves the inhibition of the p38-MAPK pathway. A pioneering in vivo discovery is that the natural biomaterial-based tissue-engineered bone demonstrates sequential immunomodulatory properties that activate proinflammatory and anti-inflammatory responses in succession, significantly accelerating the repair of bone defects. This study provides a new research basis and an effective method for developing autogenous bone substitute materials and treating large-sized bone defects.

Characterization of a decellularized pericardium extracellular matrix hydrogel for regenerative medicine: insights on animal-to-animal variability

In the past years, the use of hydrogels derived from decellularized extracellular matrix (dECM) for regenerative medicine purposes has significantly increased. The intrinsic bioactive and immunomodulatory properties indicate these materials as promising candidates for therapeutical applications. However, to date, limitations such as animal-to-animal variability still hinder the clinical translation. Moreover, the choice of tissue source, decellularization and solubilization protocols leads to differences in dECM-derived hydrogels. In this context, detailed characterization of chemical, physical and biological properties of the hydrogels should be performed, with attention to how these properties can be affected by animal-to-animal variability. Herein, we report a detailed characterization of a hydrogel derived from the decellularized extracellular matrix of bovine pericardium (dBP). Protein content, rheological properties, injectability, surface microstructure, in vitro stability and cytocompatibility were evaluated, with particular attention to animal-to-animal variability. The gelation process showed to be thermoresponsive and the obtained dBP hydrogels are injectable, porous, stable up to 2 weeks in aqueous media, rapidly degrading in enzymatic environment and cytocompatible, able to maintain cell viability in human mesenchymal stromal cells. Results from proteomic analysis proved that dBP hydrogels are highly rich in composition, preserving bioactive proteoglycans and glycoproteins in addition to structural proteins such as collagen. With respect to the chemical composition, animal-to-animal variability was shown, but the biological properties were not affected, which remained consistent in different batches. Taken together these results show that dBP hydrogels are excellent candidates for regenerative medicine applications.

From bone to nanoparticles: development of a novel generation of bone derived nanoparticles for image guided orthopedic regeneration

Bone related diseases such as osteoporosis, osteoarthritis, metastatic bone cancer, osteogenesis imperfecta, and Paget's disease, are primarily treated with pharmacologic therapies that often exhibit limited efficacy and substantial side effects. Bone injuries or fractures are primarily repaired with biocompatible materials that produce mixed results in sufficiently regenerating healthy and homogenous bone tissue. Each of these bone conditions, both localized and systemic, use different strategies with the same goal of achieving a healthy and homeostatic bone environment. In this study, we developed a new type of bone-based nanoparticle (BPs) using the entire organic extracellular matrix (ECM) of decellularized porcine bone, additionally encapsulating indocyanine green dye (ICG) for an in vivo monitoring capability. Utilizing the regenerative capability of bone ECM and the functionality of nanoparticles, the ICG encapsulated BPs (ICG/BPs) have been demonstrated to be utilized as a therapeutic option for localized and systemic orthopedic conditions. Additionally, ICG enables an in situ monitoring capability in the Short-Wave Infrared (SWIR) spectrum, capturing the degradation or the biodistribution of the ICG/BPs after both local implantation and intravenous administration, respectively. The efficacy and safety of the ICG/BPs shown within this study lay the foundation for future investigations, which will delve into optimization for clinical translation.

Development of porcine skeletal muscle extracellular matrix-derived hydrogels with improved properties and low immunogenicity

Hydrogels derived from decellularized extracellular matrices (ECM) of animal origin show immense potential for regenerative applications due to their excellent cytocompatibility and biomimetic properties. Despite these benefits, the impact of decellularization protocols on the properties and immunogenicity of these hydrogels remains relatively unexplored. In this study, porcine skeletal muscle ECM (smECM) underwent decellularization using mechanical disruption (MD) and two commonly employed decellularization detergents, sodium deoxycholate (SDC) or Triton X-100. To mitigate immunogenicity associated with animal-derived ECM, all decellularized tissues were enzymatically treated with α-galactosidase to cleave the primary xenoantigen-the α-Gal antigen. Subsequently, the impact of the different decellularization protocols on the resultant hydrogels was thoroughly investigated. All methods significantly reduced total DNA content in hydrogels. Moreover, α-galactosidase treatment was crucial for cleaving α-Gal antigens, suggesting that conventional decellularization methods alone are insufficient. MD preserved total protein, collagen, sulfated glycosaminoglycan, laminin, fibronectin, and growth factors more efficiently than other protocols. The decellularization method impacted hydrogel gelation kinetics and ultrastructure, as confirmed by turbidimetric and scanning electron microscopy analyses. MD hydrogels demonstrated high cytocompatibility, supporting satellite stem cell recruitment, growth, and differentiation into multinucleated myofibers. In contrast, the SDC and Triton X-100 protocols exhibited cytotoxicity. Comprehensive in vivo immunogenicity assessments in a subcutaneous xenotransplantation model revealed MD hydrogels' biocompatibility and low immunogenicity. These findings highlight the significant influence of the decellularization protocol on hydrogel properties. Our results suggest that combining MD with α-galactosidase treatment is an efficient method for preparing low-immunogenic smECM-derived hydrogels with enhanced properties for skeletal muscle regenerative engineering and clinical applications.

Decellularized Bone Matrix/45S5 Bioactive Glass Biocomposite Hydrogel-Based Constructs with Angiogenic and Osteogenic Properties: Ex Ovo and Ex Vivo Evaluations

Decellularized extracellular matrix is often used to create an in vivo-like environment that supports cell growth and proliferation, as it reflects the micro/macrostructure and molecular composition of tissues. On the other hand, bioactive glasses (BG) are surface-reactive glass-ceramics that can convert to hydroxyapatite in vivo and promote new bone formation. This study is designed to evaluate the key properties of a novel angiogenic and osteogenic biocomposite graft made of bovine decellularized bone matrix (DBM) hydrogel and 45S5 BG microparticles (10 and 20 wt%) to combine the existing superior properties of both biomaterial classes. Morphological, physicochemical, mechanical, and thermal characterizations of DBM and DBM/BG composite hydrogels are performed. Their in vitro biocompatibility is confirmed by cytotoxicity and hemocompatibility analyses. Ex vivo chick embryo aortic arch and ex ovo chick chorioallantoic membrane (CAM) assays reveal that the present pro-angiogenic property of DBM hydrogels is enhanced by the incorporation of BG. Histochemical stainings (Alcian blue and Alizarin red) and digital image analysis of ossification on hind limbs of embryos used in the CAM model reveal the osteogenic potential of biomaterials. The findings support the notion that the developed DBM/BG composite hydrogel constructs have the potential to be a suitable graft for bone repair.

3D-printed polycaprolactone/tricalcium silicate scaffolds modified with decellularized bone ECM-oxidized alginate for bone tissue engineering

The treatment of large craniofacial bone defects requires more advanced and effective strategies than bone grafts since such defects are challenging and cannot heal without intervention. In this regard, 3D printing offers promising solutions through the fabrication of scaffolds with the required shape, porosity, and various biomaterials suitable for specific tissues. In this study, 3D-printed polycaprolactone (PCL)-based scaffolds containing up to 30 % tricalcium silicate (TCS) were fabricated and then modified by incorporation of decellularized bone matrix- oxidized sodium alginate (DBM-OA). The results showed that the addition of 20 % TCS increased compressive modulus by 4.5-fold, yield strength by 12-fold, and toughness by 15-fold compared to pure PCL. In addition, the samples containing TCS revealed the formation of crystalline phases with a Ca/P ratio near that of hydroxyapatite (1.67). Cellular experiment results demonstrated that TCS have improved the biocompatibility of PCL-based scaffolds. On day 7, the scaffolds modified with DBM and 20 % TCS exhibited 8-fold enhancement of ALP activity of placenta-derived mesenchymal stem/stromal cells (P-MSCs) compared to pure PCL scaffolds. The present study's results suggest that the incorporation of TCS and DBM-OA into the PCL-based scaffold improves its mechanical behavior, bioactivity, biocompatibility, and promotes mineralization and early osteogenic activity.

Development of a Cissus quadrangularis-Doped Extracellular Matrix and a Hyaluronic Acid-Incorporated Scaffold for Periodontal Regeneration: An In Vitro Study

PURPOSE

The study aimed to analyze whether adding Cissus quadrangularis (CQ) extract and the extracellular matrix of ovine tendon (TENDON) increases the regenerative potential of mesenchymal stem cells produced in hyaluronic acid (HA) scaffolds for tenogenesis.

MATERIALS AND METHODS

Fifty grams of powdered CQ was mixed with 250 mL of ethanol to prepare the extract. Two grams of hyaluronic acid powder was added to 100 mL of distilled water to make the HA solution. The ovine tendon was decellularized using a mixture of 10% phosphate-buffered saline (PBS), sodium dodecyl sulfate (SDS), and Triton-X. The hydrogel samples were prepared by mixing the extracellular matrix of tendon, HA, and CQ, after which they were divided into study groups such as HA, HA + CQ, HA + TENDON, and HA + CQ + TENDON. Scanning electron microscopy (SEM) analysis, swelling analysis, differentiation analysis, compression test, compatibility assay, and tenogenesis assay were later conducted.

RESULTS

The morphology of the samples was analyzed using SEM. Low levels of swelling of the hydrogels were observed. Cells were found to be viable and showed good differentiation and tenogenesis. Optimal compression levels were observed, and the properties of the prepared hydrogels were satisfactory.

CONCLUSION

The results suggest that the addition of CQ considerably increases the tenogenic potential of the extracellular matrix/HA scaffold. Hence, it can be used as a regenerative material for periodontal tissue regeneration.

Using Decellularized Magnetic Microrobots to Deliver Functional Cells for Cartilage Regeneration

The use of natural cartilage extracellular matrix (ECM) has gained widespread attention in the field of cartilage tissue engineering. However, current approaches for delivering functional scaffolds for osteoarthritis (OA) therapy rely on knee surgery, which is limited by the narrow and complex structure of the articular cavity and carries the risk of injuring surrounding tissues. This work introduces a novel cell microcarrier, magnetized cartilage ECM-derived scaffolds (M-CEDSs), which are derived from decellularized natural porcine cartilage ECM. Human bone marrow mesenchymal stem cells are selected for their therapeutic potential in OA treatments. Owing to their natural composition, M-CEDSs have a biomechanical environment similar to that of human cartilage and can efficiently load functional cells while maintaining high mobility. The cells are released spontaneously at a target location for at least 20 days. Furthermore, cell-seeded M-CEDSs show better knee joint function recovery than control groups 3 weeks after surgery in preclinical experiments, and ex vivo experiments reveal that M-CEDSs can rapidly aggregate inside tissue samples. This work demonstrates the use of decellularized microrobots for cell delivery and their in vivo therapeutic effects in preclinical tests.

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.

A bioscaffold of decellularized whole osteochondral sheet improves proliferation and differentiation of loaded mesenchymal stem cells in a rabbit model

As a Natural decellularized extracellular matrix, osteochondral tissue is the best scaffold for the restoration of osteoarthritis defects. Bioscaffolds have the most similarly innate properties like biomechanical properties and the preserved connection of the bone-to-cartilage border. Although, their compacity and low porosity particularly, are proven to be difficulties of decellularization and cell penetration. This study aims to develop a new bioscaffold of decellularized osteochondral tissue (DOT) that is recellularized by bone marrow-derived mesenchymal stem cells (BM-MSCs), as a biphasic allograft, which preserved the interface between the cartilage section and subchondral bone of the joint. Whole osteochondral tissues of rabbit knee joints were sheeted in cartilaginous parts in 200-250 µm sections while connected to the subchondral bone and then fully decellularized. The BM-MSCs were seeded on the scaffolds in vitro; some constructs were subcutaneously implanted into the back of the rabbit. The cell penetration, differentiation to bone and cartilage, viability, and cell proliferation in vitro and in vivo were evaluated by qPCR, histological staining, MTT assay, and immunohistochemistry. DNA content analysis and SEM assessments confirmed the decellularization of the bioscaffold. Then, histological and SEM evaluations indicated that the cells could successfully penetrate the bone and cartilage lacunas in implanted grafts. MTT assay confirmed cell proliferation. Prominently, gene expression analysis showed that seeded cells differentiated into osteoblasts and chondrocytes in both bone and cartilage sections. More importantly, seeded cells on the bioscaffold started ECM secretion. Our results indicate that cartilage-to-bone border integrity was largely preserved. Additionally, ECM-sheeted DOT could be employed as a useful scaffold for promoting the regeneration of osteochondral defects.

Harnessing the Native Extracellular Matrix for Periodontal Regeneration Using a Melt Electrowritten Biphasic Scaffold

Scaffolds have been used to promote periodontal regeneration by providing control over the spacio-temporal healing of the periodontium (cementum, periodontal ligament (PDL) and alveolar bone). This study proposes to enhance the biofunctionality of a biphasic scaffold for periodontal regeneration by means of cell-laid extracellular matrix (ECM) decoration. To this end, a melt electrowritten scaffold was cultured with human osteoblasts for the deposition of bone-specific ECM. In parallel, periodontal ligament cells were used to form a cell sheet, which was later combined with the bone ECM scaffold to form a biphasic PDL-bone construct. The resulting biphasic construct was decellularised to remove all cellular components while preserving the deposited matrix. Decellularisation efficacy was confirmed in vitro, before the regenerative performance of freshly decellularised constructs was compared to that of 3-months stored freeze-dried scaffolds in a rodent periodontal defect model. Four weeks post-surgery, microCT revealed similar bone formation in all groups. Histology showed higher amounts of newly formed cementum and periodontal attachment in the fresh and freeze-dried ECM functionalised scaffolds, although it did not reach statistical significance. This study demonstrated that the positive effect of ECM decoration was preserved after freeze-drying and storing the construct for 3 months, which has important implications for clinical translation.

Effect of In Vitro Culture Length on the Bone-Forming Capacity of Osteoblast-Derived Decellularized Extracellular Matrix Melt Electrowritten Scaffolds

Recent advancements in decellularization have seen the development of extracellular matrix (ECM)-decorated scaffolds for bone regeneration; however, little is understood of the impact of in vitro culture prior to decellularization on the performances of these constructs. Therefore, this study investigated the effect of in vitro culture on ECM-decorated melt electrowritten polycaprolactone scaffold bioactivity. The scaffolds were seeded with osteoblasts and cultured for 1, 2, or 4 weeks to facilitate bone-specific ECM deposition and subsequently decellularized to form an acellular ECM-decorated scaffold. The utilization of mild chemicals and DNase was highly efficient in removing DNA while preserving ECM structure and composition. ECM decoration of the melt electrowritten fibers was observed within the first week of culture, with increased ECM at 2 and 4 week culture periods. Infiltration of re-seeded cells as well as overall bone regeneration in a rodent calvarial model was impeded by a longer culture period. Thus, it was demonstrated that the length of culture has a key influence on the osteogenic properties of decellularized ECM-decorated scaffolds, with long-term culture (2+ weeks) causing pore obstruction and creating a physical barrier which interfered with bone formation. These findings have important implications for the development of effective ECM-decorated scaffolds for bone regeneration.

Recent developments in nanomaterials for upgrading treatment of orthopedics diseases

Nanotechnology has changed science in the last three decades. Recent applications of nanotechnology in the disciplines of medicine and biology have enhanced medical diagnostics, manufacturing, and drug delivery. The latest studies have demonstrated this modern technology's potential for developing novel methods of disease detection and treatment, particularly in orthopedics. According to recent developments in bone tissue engineering, implantable substances, diagnostics and treatment, and surface adhesives, nanomedicine has revolutionized orthopedics. Numerous nanomaterials with distinctive chemical, physical, and biological properties have been engineered to generate innovative medication delivery methods for the local, sustained, and targeted delivery of drugs with enhanced therapeutic efficacy and minimal or no toxicity, indicating a very promising strategy for effectively controlling illnesses. Extensive study has been carried out on the applications of nanotechnology, particularly in orthopedics. Nanotechnology can revolutionize orthopedics cure, diagnosis, and research. Drug delivery precision employing nanotechnology using gold and liposome nanoparticles has shown especially encouraging results. Moreover, the delivery of drugs and biologics for osteosarcoma is actively investigated. Different kind of biosensors and nanoparticles has been used in the diagnosis of bone disorders, for example, renal osteodystrophy, Paget's disease, and osteoporosis. The major hurdles to the commercialization of nanotechnology-based composite are eventually examined, thus helping in eliminating the limits in connection to some pre-existing biomaterials for orthopedics, important variables like implant life, quality, cure cost, and pain and relief from pain. The potential for nanotechnology in orthopedics is tremendous, and most of it looks to remain unexplored, but not without challenges. This review aims to highlight the up tp date developments in nanotechnology for boosting the treatment modalities for orthopedic ailments. Moreover, we also highlighted unmet requirements and present barriers to the practical adoption of biomimetic nanotechnology-based orthopedic treatments.

Collagen and Beyond: A Comprehensive Comparison of Human ECM Properties Derived from Various Tissue Sources for Regenerative Medicine Applications

Collagen, along with proteoglycans, glycosaminoglycans, glycoproteins, and various growth factors, forms the extracellular matrix (ECM) and contributes to the complexity and diversity of different tissues. Herein, we compared the physicochemical and biological properties of ECM hydrogels derived from four different human tissues: skin, bone, fat, and birth. Pure human collagen type I hydrogels were used as control. Physical characterization of ECM hydrogels and assessment of cell response of cord-tissue mesenchymal stem cells (CMSCs) were performed. Decellularization efficiency was found to be >90% for all ECM. Hydroxyproline quantification assay showed that collagen content in birth ECM was comparable to collagen control and significantly greater than other sources of ECM. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed the presence of γ, β, α₁ and α₂ collagen chains in all ECMs. Gelation kinetics of ECM hydrogels was significantly slower than collagen control. Compressive modulus of skin ECM was the highest and birth ECM was the lowest. Skin and birth ECM hydrogels were more stable than bone and fat ECM hydrogels. CMSCs encapsulated in birth ECM hydrogels exhibited the highest metabolic activity. Rheological characterization revealed that all ECM-derived inks exhibited shear thinning properties, and skin-derived ECM inks were most suitable for extrusion-based bioprinting for the concentration and printing conditions used in this study. Overall, results demonstrate that the physicochemical and biological properties of ECM hydrogels vary significantly depending on the tissue source. Therefore, careful selection of tissue source is important for development of ECM-based biomimetic tissue constructs for regenerative medicine applications.

Development potential of extracellular matrix hydrogels as hemostatic materials

The entry of subcutaneous extracellular matrix proteins into the circulation is a key step in hemostasis initiation after vascular injury. However, in cases of severe trauma, extracellular matrix proteins are unable to cover the wound, making it difficult to effectively initiate hemostasis and resulting in a series of bleeding events. Acellular-treated extracellular matrix (ECM) hydrogels are widely used in regenerative medicine and can effectively promote tissue repair due to their high mimic nature and excellent biocompatibility. ECM hydrogels contain high concentrations of extracellular matrix proteins, including collagen, fibronectin, and laminin, which can simulate subcutaneous extracellular matrix components and participate in the hemostatic process. Therefore, it has unique advantages as a hemostatic material. This paper first reviewed the preparation, composition and structure of extracellular hydrogels, as well as their mechanical properties and safety, and then analyzed the hemostatic mechanism of the hydrogels to provide a reference for the application and research, and development of ECM hydrogels in the field of hemostasis.

Strategies for improving the 3D printability of decellularized extracellular matrix bioink

3D bioprinting is a revolutionary technology capable of replicating native tissue and organ microenvironments by precisely placing cells into 3D structures using bioinks. However, acquiring the ideal bioink to manufacture biomimetic constructs is challenging. A natural extracellular matrix (ECM) is an organ-specific material that provides physical, chemical, biological, and mechanical cues that are hard to mimic using a small number of components. Organ-derived decellularized ECM (dECM) bioink is revolutionary and has optimal biomimetic properties. However, dECM is always "non-printable" owing to its poor mechanical properties. Recent studies have focused on strategies to improve the 3D printability of dECM bioink. In this review, we highlight the decellularization methods and procedures used to produce these bioinks, effective methods to improve their printability, and recent advances in tissue regeneration using dECM-based bioinks. Finally, we discuss the challenges associated with manufacturing dECM bioinks and their potential large-scale applications.

Dentin extracellular matrix loaded bioactive glass/GelMA support rapid bone mineralization for potential pulp regeneration

The study aims to develop a novel dentin extracellular matrix (dECM) loaded gelatin methacrylate (GelMA)-5 wt% bioactive glass (BG) (Gel-BG) hydrogel for dental pulp regeneration. We investigate the role of dECM content (2.5, 5, and 10 wt%) on the physicochemical characteristics and biological responses of Gel-BG hydrogel in contact with stem cells isolated from human exfoliated deciduous teeth (SHED). Results showed that the compressive strength of Gel-BG/dECM hydrogel significantly enhanced from 18.9 ± 0.5 kPa (at Gel-BG) to 79.8 ± 3.0 kPa after incorporation of 10 wt% dECM. Moreover, we found that in vitro bioactivity of Gel-BG improved and the degradation rate and swelling ratio reduced with increasing dECM content. The hybrid hydrogels also revealed effectual biocompatibility, >138 % cell viability after 7 days of culture; where Gel-BG/5%dECM was most suitable. In addition, the incorporation of 5 wt% dECM within Gel-BG considerably improved alkaline phosphatase (ALP) activity and osteogenic differentiation of SHED cells. Taken together, the novel bioengineered Gel-BG/dECM hydrogels having appropriate bioactivity, degradation rate, osteoconductive and mechanical properties represent the potential applications for clinical practice in the future.

Unraveling the Relevance of Tissue-Specific Decellularized Extracellular Matrix Hydrogels for Vocal Fold Regenerative Biomaterials: A Comprehensive Proteomic and In Vitro Study

Decellularized extracellular matrix (dECM) is a promising material for tissue engineering applications. Tissue-specific dECM is often seen as a favorable material that recapitulates a native-like microenvironment for cellular remodeling. However, the minute quantity of dECM derivable from small organs like the vocal fold (VF) hampers manufacturing scalability. Small intestinal submucosa (SIS), a commercial product with proven regenerative capacity, may be a viable option for VF applications. This study aims to compare dECM hydrogels derived from SIS or VF tissue with respect to protein content and functionality using mass spectrometry-based proteomics and in vitro studies. Proteomic analysis reveals that VF and SIS dECM share 75% of core matrisome proteins. Although VF dECM proteins have greater overlap with native VF, SIS dECM shows less cross-sample variability. Following decellularization, significant reductions of soluble collagen (61%), elastin (81%), and hyaluronan (44%) are noted in VF dECM. SIS dECM contains comparable elastin and hyaluronan but 67% greater soluble collagen than VF dECM. Cells deposit more neo-collagen on SIS than VF-dECM hydrogels, whereas neo-elastin (~50 μg/scaffold) and neo-hyaluronan (~ 6 μg/scaffold) are comparable between the two hydrogels. Overall, SIS dECM possesses reasonably similar proteomic profile and regenerative capacity to VF dECM. SIS dECM is considered a promising alternative for dECM-derived biomaterials for VF regeneration.

A comparative study on various cell sources for constructing tissue-engineered meniscus

Injury to the meniscus is a common occurrence in the knee joint and its management remains a significant challenge in the clinic. Appropriate cell source is essential to cell-based tissue regeneration and cell therapy. Herein, three commonly used cell sources, namely, bone marrow mesenchymal stem cell (BMSC), adipose-derived stem cell (ADSC), and articular chondrocyte, were comparatively evaluated to determine their potential for engineered meniscus tissue in the absence of growth factor stimulus. Cells were seeded on electrospun nanofiber yarn scaffolds that share similar aligned fibrous configurations with native meniscus tissue for constructing meniscus tissue in vitro. Our results show that cells proliferated robustly along nanofiber yarns to form organized cell-scaffold constructs, which recapitulate the typical circumferential fiber bundles of native meniscus. Chondrocytes exhibited different proliferative characteristics and formed engineered tissues with distinct biochemical and biomechanical properties compared to BMSC and ADSC. Chondrocytes maintained good chondrogenesis gene expression profiles and produced significantly increased chondrogenic matrix and form mature cartilage-like tissue as revealed by typical cartilage lacunae. In contrast, stem cells underwent predominately fibroblastic differentiation and generated greater collagen, which contributes to improved tensile strengths of cell-scaffold constructs in comparison to the chondrocyte. ADSC showed greater proliferative activity and increased collagen production than BMSC. These findings indicate that chondrocytes are superior to stem cells for constructing chondrogenic tissues while the latter is feasible to form fibroblastic tissue. Combination of chondrocytes and stem cells might be a possible solution to construct fibrocartilage tissue and meniscus repair and regeneration.

Physico-biological evaluation of 3D printed dECM/TOCN/alginate hydrogel based scaffolds for cartilage tissue regeneration

Cartilage damage is the leading cause of osteoarthritis (OA), especially in an aging society. Mimicking the native cartilage microenvironment for chondrogenic differentiation along with constructing a stable and controlled architectural scaffold is considerably challenging. In this study, three-dimensional (3D) printed scaffolds using tempo-oxidized cellulose nanofiber (TOCN), decellularized extracellular matrix (dECM), and sodium alginate (SA) were fabricated for cartilage tissue regeneration. We prepared three groups (dECM80, dECM50, dECM20) of 3D printable hydrogels with different ratios of TOCN and dECM where SA concentration remained the same. Two-step crosslinking was performed with CaCl₂ solution to achieve the highly stable 3D printed scaffolds. Finally, the fundamental physical characterizations showed that increasing the ratio of TOCN with dECM significantly improved the viscoelastic behaviour, stability, mechanical properties, and printability of the scaffolds. Based on the results, the 3D printed dECM50 scaffolds with controlled and identical pore sizes increased the whole-layer integrity and nutrient supply in each layer of the scaffold. Furthermore, evaluation of in vitro and in vivo biocompatibility of the scaffolds with rBMSCs indicated that dECM50 scaffolds provided a suitable microenvironment for cell proliferation and promoted chondrogenesis by remarkably expressing the cartilage-specific markers. This study demonstrates that 3D printed dECM50 scaffolds provide a favourable and promising microenvironment for cartilage tissue regeneration.

Bioactive composite hydrogels as 3D mesenchymal stem cell encapsulation environment for bone tissue engineering: in vitro and in vivo studies

Although decellularized bone matrix (DBM) has often been used in scaffold form for osteogenic applications, its use as a stem cell encapsulation matrix adaptable to surgical shaping procedures has been neglected. This study aimed to investigate the feasibility of utilizing solubilized DBM and nanohydroxyapatite (nHAp)-incorporated DBM hydrogels as encapsulation matrix for bone marrow-derived MSCs (BM-MSCs). First, DBM and DBM/nHAp hydrogels were assessed by physical, chemical, turbidimetric, thermal, and mechanical methods; then, in vitro cytocompatibility and in vitro hemocompatibility were investigated. An in vivo study was performed to evaluate the osteogenic properties of hydrogels alone or with BM-MSCs encapsulated in them. The findings revealed that hydrogels retained high levels of collagen and glycosaminoglycans after successful decellularization. They were found to be cytocompatible and hemocompatible in vitro, and were able to gel with sufficient mechanical stability at physiological temperature. BM-MSCs survived in culture for at least 2 weeks as metabolically active when encapsulated in both DBM and DBM/nHAp. Preliminary in vivo study showed that DBM-nHAp has higher osteogenicity than DBM. Moreover, BM-MSC encapsulated DMB/nHAp showed predominant bone-like tissue formation at 30 days in the rat ectopic site compared to its cell-free form.

Engineered neural tissue made using hydrogels derived from decellularised tissues for the regeneration of peripheral nerves

Engineered neural tissue (EngNT) promotes in vivo axonal regeneration. Decellularised materials (dECM) are complex biologic scaffolds that can improve the cellular environment and also encourage positive tissue remodelling in vivo. We hypothesised that we could incorporate a hydrogel derived from a decellularised tissue (dECMh) into EngNT, thereby providing an alternative to the currently used purified collagen I hydrogel for the first time. Decellularisation was carried out on bone (B-ECM), liver (LIV-ECM), and small intestinal (SIS-ECM) tissues and the resultant dECM was biochemically and mechanically characterised. dECMh differed in mechanical and biochemical properties that likely had an effect on Schwann cell behaviour observed in metabolic activity and contraction profiles. Cellular alignment was observed in tethered moulds within the B-ECM and SIS-ECM derived hydrogels only. No difference was observed in dorsal root ganglia (DRG) neurite extension between the dECMh groups and collagen I groups when applied as a coverslip coating, however, when DRG were seeded atop EngNT constructs, only the B-ECM derived EngNT performed similarly to collagen I derived EngNT. B-ECM EngNT further exhibited similar axonal regeneration to collagen I EngNT in a 10 mm gap rat sciatic nerve injury model after 4 weeks. Our results have shown that various dECMh can be utilised to produce EngNT that can promote neurite extension in vitro and axonal regeneration in vivo. STATEMENT OF SIGNIFICANCE: Nerve autografts are undesirable due to the sacrifice of a patient's own nerve tissue to repair injuries. Engineered neural tissue (EngNT) is a type of living artificial tissue that has been developed to overcome this. To date, only a collagen hydrogel has been shown to be effective in the production and utilisation of EngNT in animal models. Hydrogels may be made from decellularised extracellular matrix derived from many tissues. In this study we showed that hydrogels from various tissues may be used to create EngNT and one was shown to comparable to the currently used collagen based EngNT in a rat sciatic nerve injry model.

Decellularized ECM hydrogels: prior use considerations, applications, and opportunities in tissue engineering and biofabrication

Tissue development, wound healing, pathogenesis, regeneration, and homeostasis rely upon coordinated and dynamic spatial and temporal remodeling of extracellular matrix (ECM) molecules. ECM reorganization and normal physiological tissue function, require the establishment and maintenance of biological, chemical, and mechanical feedback mechanisms directed by cell-matrix interactions. To replicate the physical and biological environment provided by the ECM in vivo, methods have been developed to decellularize and solubilize tissues which yield organ and tissue-specific bioactive hydrogels. While these biomaterials retain several important traits of the native ECM, the decellularizing process, and subsequent sterilization, and solubilization result in fragmented, cleaved, or partially denatured macromolecules. The final product has decreased viscosity, moduli, and yield strength, when compared to the source tissue, limiting the compatibility of isolated decellularized ECM (dECM) hydrogels with fabrication methods such as extrusion bioprinting. This review describes the physical and bioactive characteristics of dECM hydrogels and their role as biomaterials for biofabrication. In this work, critical variables when selecting the appropriate tissue source and extraction methods are identified. Common manual and automated fabrication techniques compatible with dECM hydrogels are described and compared. Fabrication and post-manufacturing challenges presented by the dECM hydrogels decreased mechanical and structural stability are discussed as well as circumvention strategies. We further highlight and provide examples of the use of dECM hydrogels in tissue engineering and their role in fabricating complex in vitro 3D microenvironments.

Mechanisms of magnesium oxide-incorporated electrospun membrane modulating inflammation and accelerating wound healing

Previously, we demonstrated that magnesium oxide (MgO)-incorporated electrospun membranes show powerful antibacterial activity and promote wound healing, but the underlying mechanisms have not been entirely understood. Herein, we investigated the relationship between structure and function of MgO-incorporated membranes and interrogated critical bioactive cues that contribute to accelerated wound healing and functional restoration. Our results show that MgO-incorporated membranes exhibit good flexibility and improved water vapor transmission rates (WVTRs) and sustained Mg²⁺ release in a simulated model of wounds. MgO-incorporated membranes modulate macrophage phenotype to downregulate inflammatory response, contributing to alleviated inflammation and creating a favorable microenvironment for wound healing. Specifically, MgO-incorporated membranes stimulate macrophages to shift to a pro-healing M2 phenotype and upregulate pro-healing cytokine of transforming growth factor-beta 1 (TGF-β1) and downregulate pro-inflammatory cytokines under lipopolysaccharide (LPS) challenge conditions. Together with increased TGF-β1 by macrophages, MgO-incorporated membranes significantly boost the proliferation of fibroblasts and upregulate collagen production, thus driving granulation tissue formation and wound closure. MgO-incorporated membranes promote angiogenesis by promoting tube formation and upregulating vascular endothelial growth factor (VEGF) production of endothelial cells. Rapid epithelialization of regenerated skin tissue is attributed to the balanced phenotype of keratinocytes between proliferative and terminally differentiated populations. In addition to coordinating keratinocyte phenotype, MgO-incorporated membranes reduce the expression of inflammatory cytokine interleukin 1-alpha (IL-1α) therefore promoting hair follicle regeneration. These data provide mechanisms of MgO-incorporated membranes that inhibit bacterial infection, alleviate inflammation, facilitate extracellular matrix production and epithelialization, and potentiate hair follicle regeneration.

An extracellular matrix hydrogel from porcine urinary bladder for tissue engineering: In vitro and in vivo analyses

BACKGROUND

The necessity to manufacture scaffolds with superior capabilities of biocompatibility and biodegradability has led to the production of extracellular matrix (ECM) scaffolds. Among their advantages, they allow better cell colonization, which enables its successful integration into the hosted tissue, surrounding the area to be repaired and their formulations facilitate placing it into irregular shapes. The ECM from porcine urinary bladder (pUBM) comprises proteins, proteoglycans and glycosaminoglycans which provide support and enable signals to the cells. These properties make it an excellent option to produce hydrogels that can be used in regenerative medicine.

OBJECTIVE

The goal of this study was to assess the biocompatibility of an ECM hydrogel derived from the porcine urinary bladder (pUBMh) in vitro using fibroblasts, macrophages, and adipose-derived mesenchymal stem cells (AD-MCSs), as well as biocompatibility in vivo using Wistar rats.

METHODS

Effects upon cells proliferation/viability was measured using MTT assay, cytotoxic effects were analyzed by quantifying lactate dehydrogenase release and the Live/Dead Cell Imaging assay. Macrophage activation was assessed by quantification of IL-6, IL-10, IL-12p70, MCP-1, and TNF-α using a microsphere-based cytometric bead array. For in vivo analysis, Wistar rats were inoculated into the dorsal sub-dermis with pUBMh. The specimens were sacrificed at 24 h after inoculation for histological study.

RESULTS

The pUBMh obtained showed good consistency and absence of cell debris. The biocompatibility tests in vitro revealed that the pUBMh promoted cell proliferation and it is not cytotoxic on the three tested cell lines and induces the production of pro-inflammatory cytokines on macrophages, mainly TNF-α and MCP-1. In vivo, pUBMh exhibited fibroblast-like cell recruitment, without tissue damage or inflammation.

CONCLUSION

The results show that pUBMh allows cell proliferation without cytotoxic effects and can be considered an excellent biomaterial for tissue engineering.

Functional acellular matrix for tissue repair

In view of their low immunogenicity, biomimetic internal environment, tissue- and organ-like physicochemical properties, and functionalization potential, decellularized extracellular matrix (dECM) materials attract considerable attention and are widely used in tissue engineering. This review describes the composition of extracellular matrices and their role in stem-cell differentiation, discusses the advantages and disadvantages of existing decellularization techniques, and presents methods for the functionalization and characterization of decellularized scaffolds. In addition, we discuss progress in the use of dECMs for cartilage, skin, nerve, and muscle repair and the transplantation or regeneration of different whole organs (e.g., kidneys, liver, uterus, lungs, and heart), summarize the shortcomings of using dECMs for tissue and organ repair after refunctionalization, and examine the corresponding future prospects. Thus, the present review helps to further systematize the application of functionalized dECMs in tissue/organ transplantation and keep researchers up to date on recent progress in dECM usage.

Biofabrication of Poly(glycerol sebacate) Scaffolds Functionalized with a Decellularized Bone Extracellular Matrix for Bone Tissue Engineering

The microarchitecture of bone tissue engineering (BTE) scaffolds has been shown to have a direct effect on the osteogenesis of mesenchymal stem cells (MSCs) and bone tissue regeneration. Poly(glycerol sebacate) (PGS) is a promising polymer that can be tailored to have specific mechanical properties, as well as be used to create microenvironments that are relevant in the context of BTE applications. In this study, we utilized PGS elastomer for the fabrication of a biocompatible and bioactive scaffold for BTE, with tissue-specific cues and a suitable microstructure for the osteogenic lineage commitment of MSCs. In order to achieve this, the PGS was functionalized with a decellularized bone (deB) extracellular matrix (ECM) (14% and 28% by weight) to enhance its osteoinductive potential. Two different pore sizes were fabricated (small: 100-150 μm and large: 250-355 μm) to determine a preferred pore size for in vitro osteogenesis. The decellularized bone ECM functionalization of the PGS not only improved initial cell attachment and osteogenesis but also enhanced the mechanical strength of the scaffold by up to 165 kPa. Furthermore, the constructs were also successfully tailored with an enhanced degradation rate/pH change and wettability. The highest bone-inserted small-pore scaffold had a 12% endpoint weight loss, and the pH was measured at around 7.14. The in vitro osteogenic differentiation of the MSCs in the PGS-deB blends revealed a better lineage commitment of the small-pore-sized and 28% (w/w) bone-inserted scaffolds, as evidenced by calcium quantification, ALP expression, and alizarin red staining. This study demonstrates a suitable pore size and amount of decellularized bone ECM for osteoinduction via precisely tailored PGS elastomer BTE scaffolds.

Preparation and Characterization of Extracellular Matrix Hydrogels Derived from Acellular Cartilage Tissue

Decellularized matrices can effectively reduce severe immune rejection with their cells and eliminated nucleic acid material and provide specific environments for tissue repair or tissue regeneration. In this study, we prepared acellular cartilage matrix (ACM) powder through the decellularization method and developed ACM hydrogels by physical, chemical, and enzymatic digestion methods. The results demonstrated that the small size group of ACM hydrogels exhibited better gel conditions when the concentration of ACM hydrogels was 30 and 20 mg/mL in 1N HCl through parameter adjustment. The data also confirmed that the ACM hydrogels retained the main components of cartilage: 61.18% of glycosaminoglycan (GAG) and 78.29% of collagen, with 99.61% of its DNA removed compared to samples without the decellularization procedure (set as 100%). Through turbidimetric gelation kinetics, hydrogel rheological property analysis, and hydrogel tissue physical property testing, this study also revealed that increasing hydrogel concentration is helpful for gelation. Besides, the ex vivo test confirmed that a higher concentration of ACM hydrogels had good adhesive properties and could fill in cartilage defects adequately. This study offers useful information for developing and manufacturing ACM hydrogels to serve as potential alternative scaffolds for future cartilage defect treatment.

Injectable demineralized bone matrix particles and their hydrogel bone grafts loaded with β-tricalcium phosphate powder and granules: A comparative study

Demineralized bone matrix (DBM), has been used as a bone-graft material because of its osteoconductivity and osteoinductivity. However, the previous research report that supports the single use of DBM is limited by its rapid resorption caused by the lack of calcium and phosphate. β-Tricalcium phosphate (TCP) is an enriched calcium phosphate material suitable for bone healing with osteoconductive properties. In this study, we have developed injectable bone graft by the loading two kinds of TCP in DBM particles and thermo-sensitive DBM-derived hydrogel (hDBM). TCP powder (pTCP) and TCP granules (gTCP) were loaded into hDBM and DBM, respectively. The bone formation effect was investigated according to the morphological features of TCP. Residual growth factor concentrations were investigated; microstructure and morphology were characterized by SEM. In-vitro studies showed that hDBM/DBM/pTCP and hDBM/DBM/gTCP bone grafts were biocompatible and could promote osteogenesis by up-regulating the expression of Runx2 and OPN, bone-related genes. In-vivo studies using the rabbit-femur defect model revealed that the implanted hDBM/DBM/pTCP bone graft showed similar histology to that of fibrous dysplasia with the expression of CD68, whereas hDBM/DBM/gTCP showed good bone formation. Loading of gTCP in place of pTCP was noticed as an effective way to improve bone regeneration in an injectable hDBM/DBM hydrogel-based bone graft.

The comprehensive on-demand 3D bio-printing for composite reconstruction of mandibular defects

Background

The mandible is a functional bio-organ that supports facial structures and helps mastication and speaking. Large mandible defects, generally greater than 6-cm segment loss, may require composite tissue reconstruction such as osteocutaneous-vascularized free flap which has a limitation of additional surgery and a functional morbidity at the donor site. A 3D bio-printing technology is recently developed to overcome the limitation in the composite reconstruction of the mandible using osteocutaneous-vascularized free flap.

Review

Scaffold, cells, and bioactive molecules are essential for a 3D bio-printing. For mandibular reconstruction, materials in a 3D bio-printing require mechanical strength, resilience, and biocompatibility. Recently, an integrated tissue and organ printing system with multiple cartridges are designed and it is capable of printing polymers to reinforce the printed structure, such as hydrogel.

Conclusion

For successful composite tissue reconstruction of the mandible, biologic considerations and components should be presented with a comprehensive on-demand online platform model of customized approaches.

Anisotropic hydrogel fabricated by controlled diffusion as a bio-scaffold for the regeneration of cartilage injury

Controlled fabrication of anisotropic materials has become a hotspot in materials science, particularly biomaterials, since the next generation of tissue engineering is based on the application of heterogeneous structures that can simulate the original biological complexity of the body. The current fabrication method of producing anisotropic materials involves expensive and highly specialized equipment, and not every conventional method can be applied to preparing anisotropic materials for corresponding tissue engineering. Anisotropic materials can be easily applied to a problem in tissue engineering: cartilage injury repairing. The articular cartilage consists of four spatially distinct regions: superficial, transitional, deep, and calcified. Each region has a specific extracellular matrix composition, mechanical properties, and cellular organization; this calls for the application of an anisotropic hydrogel. Controlled diffusion, under the assistance of buoyancy, has been considered a generalized method to prepare materials using a gradient. The diffusion of two solutions can be controlled through the difference in their densities. In addition to providing anisotropy, this method realizes the in situ formation of an anisotropic hydrogel, and simplifies the preparation process, freeing it from the need for expensive equipment such as 3D printing and microfluidics. Herein, an anisotropic hydrogel based on a decellularized extracellular matrix is fabricated and characterized. The as-prepared scaffold possessed specific chemical composition, physical properties, and physiological factor gradient. In vitro experiments ensured its biocompatibility and biological effectiveness; further in vivo experiments confirmed its application in the effective regeneration of cartilage injury.

Cell-Laden Composite Hydrogel Bioinks with Human Bone Allograft Particles to Enhance Stem Cell Osteogenesis

There is a growing demand for bone graft substitutes that mimic the extracellular matrix properties of the native bone tissue to enhance stem cell osteogenesis. Composite hydrogels containing human bone allograft particles are particularly interesting due to inherent bioactivity of the allograft tissue. Here, we report a novel photocurable composite hydrogel bioink for bone tissue engineering. Our composite bioink is formulated by incorporating human allograft bone particles in a methacrylated alginate formulation to enhance adult human mesenchymal stem cell (hMSC) osteogenesis. Detailed rheology and printability studies confirm suitability of our composite bioinks for extrusion-based 3D bioprinting technology. In vitro studies reveal high cell viability (~90%) for hMSCs up to 28 days of culture within 3D bioprinted composite scaffolds. When cultured within bioprinted composite scaffolds, hMSCs show significantly enhanced osteogenic differentiation as compared to neat scaffolds based on alkaline phosphatase activity, calcium deposition, and osteocalcin expression.

Treatment strategies for meniscal lesions: from past to prospective therapeutics

Menisci play an important role in the biomechanics of knee joint function, including loading transmission, joint lubrication, prevention of soft tissue impingement during motion and joint stability. Meniscal repair presents a challenge due to a lack of vascularization that limits the healing capacity of meniscal tissue. In this review, the authors aimed to untangle the available treatment options for repairing meniscal tears. Various surgical procedures have been developed to treat meniscal tears; however, clinical outcomes are limited. Consequently, numerous researchers have focused on different treatments such as the application of exogenous and/or autologous growth factors, scaffolds including tissue-derived matrix, cell-based therapy and miRNA-210. The authors present current and prospective treatment strategies for meniscal lesions.

Printing biohybrid materials for bioelectronic cardio-3D-cellular constructs

Conductive hydrogels are emerging as promising materials for bioelectronic applications as they minimize the mismatch between biological and electronic systems. We propose a strategy to bioprint biohybrid conductive bioinks based on decellularized extracellular matrix (dECM) and multiwalled carbon nanotubes. These inks contained conductive features and morphology of the dECM fibers. Electrical stimulation (ES) was applied to bioprinted structures containing human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs). It was observed that in the absence of external ES, the conductive properties of the materials can improve the contractile behavior of the hPSC-CMs, and this effect is enhanced under the application of external ES. Genetic markers indicated a trend toward a more mature state of the cells with upregulated calcium handling proteins and downregulation of calcium channels involved in the generation of pacemaking currents. These results demonstrate the potential of our strategy to manufacture conductive hydrogels in complex geometries for actuating purposes.

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Conductive biohybrid hydrogels were 3D bioprinted using the FRESH method

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MWCNTs increased the conductivity and fiber diameter of dECM hydrogels

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Bioactuating applications were explored on the bioprinted structures

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Material’s conductivity and external electrical stimulation improved cell contractility

Research progress of natural tissue-derived hydrogels for tissue repair and reconstruction

There are many different grafts to repair damaged tissue. Various types of biological scaffolds, including films, fibers, microspheres, and hydrogels, can be used for tissue repair. A hydrogel, which is composed a natural or synthetic polymer network with high water absorption capacity, can provide a microenvironment closely resembling the extracellular matrix (ECM) of natural tissues to stimulate cell adhesion, proliferation, and differentiation. It has been shown to have great application potential in the field of tissue repair and regeneration. Hydrogels derived from natural tissues retain a variety of proteins and growth factors in optimal proportions, which is beneficial for the regeneration of specific tissues. This article reviews the latest research advances in the field of hydrogels from a variety of natural tissue sources, including bone tissue, blood vessels, nerve tissue, adipose tissue, skin tissue, and muscle tissue, including preparation methods, advantages, and applications in tissue engineering and regenerative medicine. Finally, it summarizes and discusses the challenges faced by natural tissue-derived hydrogels used in tissue repair, as well as future research and application directions.

3D printed gelatin/decellularized bone composite scaffolds for bone tissue engineering: Fabrication, characterization and cytocompatibility study

Three-dimensional (3D) printing technology enables the design of personalized scaffolds with tunable pore size and composition. Combining decellularization and 3D printing techniques provides the opportunity to fabricate scaffolds with high potential to mimic native tissue. The aim of this study is to produce novel decellularized bone extracellular matrix (dbECM)-reinforced composite-scaffold that can be used as a biomaterial for bone tissue engineering. Decellularized bone particles (dbPTs, ∼100 ​μm diameter) were obtained from rabbit femur and used as a reinforcement agent by mixing with gelatin (GEL) in different concentrations. 3D scaffolds were fabricated by using an extrusion-based bioprinter and crosslinking with microbial transglutaminase (mTG) enzyme, followed by freeze-drying to obtain porous structures. Fabricated 3D scaffolds were characterized morphologically, mechanically, and chemically. Furthermore, MC3T3-E1 mouse pre-osteoblast cells were seeded on the dbPTs reinforced GEL scaffolds (GEL/dbPTs) and cultured for 21 days to assess cytocompatibility and cell attachment. We demonstrate the 3D-printability of dbPTs-reinforced GEL hydrogels and the achievement of homogenous distribution of the dbPTs in the whole scaffold structure, as well as bioactivity and cytocompatibility of GEL/dbPTs scaffolds. It was shown that Young's modulus and degradation rate of scaffolds were enhanced with increasing dbPTs content. Multiphoton microscopy imaging displayed the interaction of cells with dbPTs, indicating attachment and proliferation of cells around the particles as well as into the GEL-particle hydrogels. Our results demonstrate that GEL/dbPTs hydrogel formulations have potential for bone tissue engineering.

An aorta ECM extracted hydrogel as a biomaterial in vascular tissue engineering application

Biological scaffolds have been undergoing significant growth in tissue engineering applications over the last years. Biopolymers extracted from ECM with various protein factors and other biological agents have been active in restoring damaged tissue. In the present study, bioactive scaffold is prepared from bovine aorta extracted natural polymeric hydrogel with advantages of availability and cost-effectiveness. The biological scaffolds were prepared through freeze-drying method to make a 3D sponge with appropriate structure, well-defined architecture and interconnected pores for vascular tissue engineering, and studied the effect of aorta hydrogel concentrations (1, 2, 3, and 4% w/v) on the scaffolds. The prepared biological scaffolds were analyzed by mechanical tests, FTIR, SEM, porosity and PBS absorption. Moreover, the morphology and proliferation of human umbilical vein cord cells on the 3D sponges were investigated. Histological analysis including, Masson trichrome (MT), hematoxylin and eosin (H&E), Verhoeff/Van Gieson (VVG) and alcian blue (AB) revealed that during this process the main components of aorta extracellular matrix containing collagen, elastin, and glycosaminoglycan were well preserved. The obtained results revealed that the scaffolds porosity were more than 90%. The Aorta-ECM4% enabled HUVECs to survive, proliferate and migrate better than 2% and 3% aorta-ECM.

Dual-Cross-linked Liquid Crystal Hydrogels with Controllable Viscoelasticity for Regulating Cell Behaviors

The liquid crystal properties and viscoelasticity of the natural bone extracellular matrix (ECM) play a decisive role in guiding cell behavior, conducting cell signals, and regulating mineralization. Here, we develop a facile approach for preparing a novel polysaccharide hydrogel with liquid crystal properties and viscoelasticity similar to those of natural bone ECM. First, a series of chitin whisker/chitosan (CHW/CS) hydrogels were prepared by chemical cross-linking with genipin, in which CHW can self-assemble to form cholesteric liquid crystals under ultrasonic treatment and CS chains can enter into the gaps between the helical layers of the CHW cholesteric liquid crystal phase to endow morphological stability and good mechanical properties. Subsequently, the obtained chemically cross-linked liquid crystal hydrogels were immersed into the desired concentration of the NaCl solution to form physical cross-linking. Due to the Hofmeister effect, the as-prepared dual-cross-linked liquid crystal hydrogels showed an enhanced modulus, viscoelasticity similar to that of natural ECM with relatively fast stress relaxation behavior, and fold surface morphology. Compared to both CHW/CS hydrogels without liquid crystal properties and CHW/CS liquid crystal hydrogels without further physical cross-linking, the dual-cross-linked CHW/CS liquid crystal hydrogels are more favorable for the adhesion, proliferation, and osteogenic differentiation of bone marrow mesenchymal stem cells. This approach could inspire the design of hydrogels mimicking the liquid crystal properties and viscoelasticity of natural bone ECM for bone repair.

Decellularized Periosteum-Derived Hydrogels Promote the Proliferation, Migration and Osteogenic Differentiation of Human Umbilical Cord Mesenchymal Stem Cells

Human umbilical cord mesenchymal stem cells (hUCMSCs) are promising for bone tissue engineering, which have a non-invasive harvesting process, high cell yield, favorable proliferation capacity, and low immunogenicity. However, the osteogenic efficacy of hUCMSCs is relatively lower than that of bone marrow mesenchymal stem cells (BMSCs). Hydrogels from decellularized extracellular matrix (dECM) preserve the biological compositions and functions of natural ECM, which can provide tissue-specific cues to regulate phenotypic expression and cell fate. It is unknown, however, whether hydrogels from periosteum can serve as pro-osteogenic carriers of hUCMSCs. Herein, a decellularized periosteum-derived hydrogel (dPH) was fabricated to reveal the effects of periosteum-specific cues on the bioactivities of hUCMSCs. A widely used non-bone/periosteum-derived ECM hydrogel product, Matrigel, was used as the control group. After decellularization, the absence of nuclei in the histological analysis indicated a successful removal of cellular components, which was also confirmed by DNA content quantification. The storage modulus of dPH increased (from 164.49 ± 29.92 Pa to 855.20 ± 20.67 Pa) with increasing concentration (from 0.5% to 1%). With a highly porous, fibrous microstructure, dPH had a more hydrophilic surface than Matrigel, of which the water contact angle reduced 62.62 ± 0.04%. Furthermore, dPH prominently promoted the initial cellular spreading with a significantly higher cell surface area (1.47-fold), cell spreading length (1.45-fold) and proliferation (approximately 1.05–1.13-fold) of hUCMSCs than those of Matrigel. Additionally, dPH was conducive to cell migration, whereas no cells migrated to Matrigel in the Transwell model. Compared with those of the Matrigel group, the osteogenesis-related genes expression levels (runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osteopontin (OPN), and osteocalcin (OCN)) and mineralized matrix formation (9.74-fold) of the hUCMSCs significantly increased in the dPH group. Our study indicated that dPH could provide a pro-osteogenic microenvironment for hUCMSCs, thereby revealing a promising application potential to repair bone defects.

Decellularised Cartilage ECM Culture Coatings Drive Rapid and Robust Chondrogenic Differentiation of Human Periosteal Cells

The control of cell behaviour in an effort to create highly homogeneous cultures is becoming an area of intense research, both to elucidate fundamental biology and for regenerative applications. The extracellular matrix (ECM) controls many cellular processes in vivo, and as such is a rich source of cues that may be translated in vitro. Herein, we describe the creation of cell culture coatings from porcine decellularised hyaline cartilage through enzymatic digestion. Surprisingly, heat-mediated sterilisation created a coating with the capacity to rapidly and robustly induce chondrogenic differentiation of human periosteal cells. This differentiation was validated through the alteration of cell phenotype from a fibroblastic to a cuboidal/cobblestone chondrocyte-like appearance. Moreover, chondrogenic gene expression further supported this observation, where cells cultured on heat sterilised ECM-coated plastic displayed higher expression of COL2A1, ACAN and PRG4 (p < 0.05) compared to non-coated plastic cultures. Interestingly, COL2A1 and ACAN expression in this context were sensitive to initial cell density; however, SOX9 expression appeared to be mainly driven by the coating independent of seeding density. The creation of a highly chondrogenic coating may provide a cost-effective solution for the differentiation and/or expansion of human chondrocytes aimed towards cartilage repair strategies.

A thermo-sensitive and injectable hydrogel derived from a decellularized amniotic membrane to prevent intrauterine adhesion by accelerating endometrium regeneration

Objective To investigate the effect of the injectable hydrogel generated from a decellularized amniotic membrane (dAM)-gel on preventing the development of an intrauterine adhesion (IUA) on a rat model. Methods The dAM-gel was developed from an amniotic membrane (AM) by a process of decellularization, lyophilization, and enzyme digestion. Histological analysis, residual component determination, electronic microscopy and turbidimetric gelation kinetics analysis were performed to characterize the dAM-gel. The proliferation and migration of endometrial cells on the dAM-gel coated surface was examined. IUA was surgically created in rats and received dAM-gel injection immediately after wound creation. Gene profiles of epithelial cells cultured on the dAM-gel coated surface were evaluated by RNA-sequencing. Results The collagen content was retained in the dAM-gel, while the GAG content decreased significantly compared with fresh AM (fAM). Gelation of the gel was temperature-sensitive and showed a matrix concentration-dependent manner. Transplantation of the dAM-gel significantly reduced fibrosis of IUA with a recovered uterine cavity, regenerated endometrium and increased microvascular density, along with elevated pregnancy rate compared with endometrium damage groups. Migration of epithelial cells was greatly promoted by the dAM-gel in a surgically created uterine wound model. By comparing the RNA-sequence data of epithelial cells that were cultured on dAM-gel coated and non-coated surfaces, respectively, distinct gene profiles relative to the cellular migration, adhesion and angiogenesis and involved signaling pathway were identified. Conclusions The injectable dAM-gel developed from AM offers a promising option for preventing endometrial fibrosis by promotion of the re-epithelialization of the damaged endometrium.

Extracellular matrix hydrogel derived from bovine bone is biocompatible in vitro and in vivo

BACKGROUND: Nowadays, biomaterials used as a scaffold must be easy to deliver in the bone defect area. Extracellular matrix (ECM) hydrogels are highly hydrated polymers that can fill irregular shapes and act as bioactive materials. OBJECTIVE: This work aims to show the effects of ECM hydrogels derived from bovine bone (bECMh) on proliferation, cytotoxicity and expression of pro-inflammatory cytokines in three cells types involved in tissue regeneration, as well as biocompatibility in vivo. METHODS: In vitro, we used an extract of bECMh to test it on macrophages, fibroblasts, and adipose-derived mesenchymal stem cells (AD-MCSs). Cell proliferation was measured using the MTT assay, cytotoxicity was measured by quantifying lactate dehydrogenase release and the Live/Dead Cell Imaging assays. Concentrations of IL-6, IL-10, IL-12p70, MCP-1 and TNF-α were quantified in the supernatants using a microsphere-based cytometric bead array. For in vivo analysis, Wistar rats were inoculated into the dorsal sub-dermis with bECMh, taking as reference the midline of the back. The specimens were sacrificed at 24 h for histological study. RESULTS: In vitro, this hydrogel behaves as a dynamic biomaterial that increases fibroblast proliferation, induces the production of pro-inflammatory cytokines in macrophages, among which MCP-1 and TNF-α stand out. In vivo, bECMh allows the colonization of host fibroblast-like and polymorphonuclear cells, without tissue damage or inflammation. CONCLUSIONS: The results indicate that bECMh is a biocompatible material that could be used as a scaffold, alone or in conjunction with cells or functional biomolecules, enhancing proliferation and allowing the filling of bone defects to its further regeneration.

The advances in nanomedicine for bone and cartilage repair

With the gradual demographic shift toward an aging and obese society, an increasing number of patients are suffering from bone and cartilage injuries. However, conventional therapies are hindered by the defects of materials, failing to adequately stimulate the necessary cellular response to promote sufficient cartilage regeneration, bone remodeling and osseointegration. In recent years, the rapid development of nanomedicine has initiated a revolution in orthopedics, especially in tissue engineering and regenerative medicine, due to their capacity to effectively stimulate cellular responses on a nanoscale with enhanced drug loading efficiency, targeted capability, increased mechanical properties and improved uptake rate, resulting in an improved therapeutic effect. Therefore, a comprehensive review of advancements in nanomedicine for bone and cartilage diseases is timely and beneficial. This review firstly summarized the wide range of existing nanotechnology applications in the medical field. The progressive development of nano delivery systems in nanomedicine, including nanoparticles and biomimetic techniques, which are lacking in the current literature, is further described. More importantly, we also highlighted the research advancements of nanomedicine in bone and cartilage repair using the latest preclinical and clinical examples, and further discussed the research directions of nano-therapies in future clinical practice.

Decellularized liver ECM-based 3D scaffolds: Compositional, physical, chemical, rheological, thermal, mechanical, and in vitro biological evaluations

The extracellular matrix (ECM) is involved in many critical cellular interactions through its biological macromolecules. In this study, a macroporous 3D scaffold originating from decellularized bovine liver ECM (dL-ECM), with defined compositional, physical, chemical, rheological, thermal, mechanical, and in vitro biological properties was developed. First, protocols were determined that effectively remove cells and DNA while ECM retains biological macromolecules collagen, elastin, sGAGs in tissue. Rheological analysis revealed the elastic properties of pepsin-digested dL-ECM. Then, dL-ECM hydrogel was neutralized, molded, formed into macroporous (~100-200 μm) scaffolds in aqueous medium at 37 °C, and lyophilized. The scaffolds had water retention ability, and were mechanically stable for at least 14 days in the culture medium. The findings also showed that increasing the dL-ECM concentration from 10 mg/mL to 20 mg/mL resulted in a significant increase in the mechanical strength of the scaffolds. The hemolysis test revealed high in vitro hemocompatibility of the dL-ECM scaffolds. Studies investigating the viability and proliferation status of human adipose stem cells seeded over a 2-week culture period have demonstrated the suitability of dL-ECM scaffolds as a cell substrate. Prospective studies may reveal the extent to which 3D dL-ECM sponges have the potential to create a biomimetic environment for cells.