Decellularized tissue and cell-derived extracellular matrices as scaffolds for orthopaedic tissue engineering

A novel strategy for bone defect repair: Stromal cell-derived factor 1α sustained-release acellular fish scale scaffolds combined with injection of bone marrow mesenchymal stem cells promote bone regeneration

Patients with bone defects often have weak cell vitality and differentiation ability of endogenous bone marrow mesenchymal stem cells (BMSCs), which makes bone regeneration face challenges. At present, the bone tissue engineering strategies are mainly to build grafts by loading cells on scaffolds in vitro. These strategies face many difficulties that limit their clinical application. To this end, we developed a new strategy for bone defect repair, namely chemotactic cell-free scaffolds combined with BMSCs injection. We first prepared a polydopamine-functionalized acellular fish scale scaffold that can continuously release stromal cell-derived factor 1α (SDF-1α) (termed as SDF-1α/PAFS) in vivo for at least 10 days. The study results showed that the scaffold not only has excellent mechanical properties and good biocompatibility but also has reactive oxygen scavenging activity, immunomodulation, angiogenesis, and osteogenesis. More importantly, SDF-1α/PAFS can recruit postoperatively injected BMSCs into bone defects for bone repair. We constructed the mouse cranial bone defect model, and in vivo experimental results confirmed that the strategy of combining SDF-1α/PAFS with BMSCs injection can effectively promote bone defect repair. Overall, this study provides a promising strategy for bone defect repair, with better clinical convenience and operability.

Polydopamine-functionalized acellular fish scale scaffolds for accelerated bone tissue regeneration

The complex microenvironment changes in the bone defect site are the main reason for its refractory treatment, including the significant increase in the level of reactive oxygen species (ROS) and inflammatory dysregulation. There is an urgent need to develop some bioactive materials that can regulate the microenvironment and promote bone regeneration. This study proposed a new strategy for designing bone tissue engineering scaffolds based on fish scales and developed a polydopamine-functionalized acellular fish scale scaffold (PDA-AFS). The results showed that PDA-AFS had excellent mechanical properties, special three-dimensional surface topography, and biodegradability. In vitro results showed that PDA-AFS had good biocompatibility and cell adhesion ability, could effectively reduce ROS levels, and had immunomodulatory activity. More importantly, PDA-AFS can enhance osteogenic differentiation of bone marrow mesenchymal stem cells and promote endogenous bone regeneration in critical-sized calvarial bone defects. In addition, transcriptome analysis also provided clues to its possible osteogenic mechanism. Overall, we provide a new strategy for designing bone tissue engineering scaffolds based on fish scales for bone regeneration treatment of bone defects.

The application of tissue engineering strategies for uterine regeneration

Uterine injuries, particularly damages to endometrium, are usually associated with abnormal menstruation, recurrent miscarriage, pregnancy complications, and infertility. Tissue engineering using cell-based, biomolecule-based, or biomaterial and scaffold-based strategies has emerged as a novel and promising approach for uterine regeneration. Stem cells, biomolecules, and porous scaffolds used alone or, very often, used in combination as a more effective treatment means have shown great potential in promoting uterine regeneration. The reported preclinical studies have indicated that appropriate tissue engineering strategies could safely and effectively reconstruct not only endometrium but also partial or even the whole uterine structure. However, the progress in the uterine regeneration area is slow in comparison to that of regenerating many other body tissues and hence it still remains a great challenge to apply uterine tissue engineering for clinical applications. In this review, conventional treatments for uterine-related diseases are briefly reviewed and discussed first. Subsequently, tissue engineering strategies (cell-based, biomolecule-based, biomaterial and scaffold-based, or their combinations) for uterine repair in preclinical studies and clinical trials are presented and analyzed. Finally, the challenges and perspectives in uterine regeneration are pointed and discussed. Despite various limitations and obstacles, the tissue engineering approach is viable and holds high promise for uterine regeneration.

Progress of silk fibroin biomaterial use in oral tissue regeneration engineering

The field of tissue engineering has introduced novel prospects for the regeneration of oral tissues, wherein stent materials assume a pivotal role and have garnered increasing attention. As a natural protein with good biocompatibility and adjustable biodegradability, an increasing number of studies focus on the uses of silk fibroin (SF) biomaterials for medical tissue regeneration engineering. Solid evidence has been found for using SF biomaterials in various oral tissue regeneration fields, from endodontics and periodontics to regenerating the maxillofacial bone. In order to provide researchers with a systematic understanding of the application of SF biomaterials to oral tissue regeneration, the present work reviews in detail the common forms of SF biomaterials for oral tissue regeneration as well as their preparation methods. In addition, the common additives used in the corresponding materials are introduced.

Bioactive scaffolds for tissue engineering: A review of decellularized extracellular matrix applications and innovations

Decellularized extracellular matrix (dECM) offers a three-dimensional, non-immunogenic scaffold, enriched with bioactive components, making it a suitable candidate for tissue regeneration. Although dECM-based scaffolds have been successfully implemented in preclinical and clinical settings within tissue engineering and regenerative medicine, the mechanisms of tissue remodeling and functional restoration are not fully understood. This review critically assesses the state-of-the-art in dECM scaffolds, including decellularization techniques for various tissues, quality control and cross-linking. It highlights the functional properties of dECM components and their latest applications in multiorgan tissue engineering and biomedicine. Additionally, the review addresses current challenges and limitations of decellularized scaffolds and offers perspectives on future directions in the field.

Novel Decellularization Scheme for Preparing Acellular Fish Scale Scaffolds for Bone Tissue Engineering

In bone tissue engineering, a suitable scaffold is the key. Due to their similar composition to bone tissue, special structure, good mechanical properties, and osteogenic properties, acellular fish scale scaffolds are potential scaffolds for bone tissue engineering. At present, the fish scale decellularization scheme mostly uses a combination of sodium dodecyl sulfate and ethylenediamine tetraacetic acid (EDTA), but this method has problems. We optimized this method using a combined method of Triton X-100, EDTA, and nuclease. In this study, the optimal scheme was screened with respect to the decellularization effect, extracellular matrix composition and structure retention, mechanical properties, cell biocompatibility, and osteogenic differentiation ability. The results showed that the optimal scheme was as follows: the native fish scales were incubated in 0.1% EDTA for 24 h, and then the cellular components were removed with 1% Triton X-100 for 4 days, followed by nuclease digestion for 24 h. On that basis, we proposed a novel and more suitable fish scale decellularization scheme, and the acellular fish scale scaffold prepared by this decellularization scheme may have great potential in bone tissue engineering.

Optimizations of Placenta Extracellular Matrix-Loaded Silk Fibroin/Alginate 3D-Printed Scaffolds Structurally and Functionally for Bone Tissue Engineering

Recent interest has been focused on extracellular matrix (ECM)-based scaffolds totreat critical-sized bone injuries. In this study, urea was used to decellularize and solubilize human placenta tissue. Then, different concentrations of ECM were composited with 8% alginate (Alg) and 12% silk fibroin (SF) for printing in order to produce a natural 3D construct that resembled bone tissue. The physical and biological features of the printed structures were evaluated entirely in vitro. Finally, a rat model was employed to examine the optimal 3D printed scaffold (5% ECM) as a bone transplant for the healing of cranial bone lesions. The present investigation demonstrated that decellularizing placental tissue fragments led to efficient removal of cell debris. In addition, a remarkable improvement in the printed scaffolds' mechanical and biological properties was observed by increasing the ECM concentration. The histology studies and real-time PCR results demonstrated the acceleration of bone regeneration in the bone lesions treated with 5%ECM-SF/Alg at 4 and 8 weeks after implantation. Overall, these results proved that the placental ECM-printed scaffolds could potentially construct biomimetic grafts to reconstruct significant bone defects and now promise to proceed with clinical studies.

Exploiting the Potential of Decellularized Extracellular Matrix (ECM) in Tissue Engineering: A Review Study

While significant progress has been made in creating polymeric structures for tissue engineering, the therapeutic application of these scaffolds remains challenging owing to the intricate nature of replicating the conditions of native organs and tissues. The use of human-derived biomaterials for therapeutic purposes closely imitates the properties of natural tissue, thereby assisting in tissue regeneration. Decellularized extracellular matrix (dECM) scaffolds derived from natural tissues have become popular because of their unique biomimetic properties. These dECM scaffolds can enhance the body's ability to heal itself or be used to generate new tissues for restoration, expanding beyond traditional tissue transfers and transplants. Enhanced knowledge of how ECM scaffold materials affect the microenvironment at the injury site is expected to improve clinical outcomes. In this review, recent advancements in dECM scaffolds are explored and relevant perspectives are offered, highlighting the development and application of these scaffolds in tissue engineering for various organs, such as the skin, nerve, bone, heart, liver, lung, and kidney.

Three-Dimensional Printed Customized Scaffolds Covered with Decellularized Bone Extracellular Matrix for Open-Wedge High-Tibial Osteotomy

Void fillers are required for osseous gaps generated after orthopedic procedures as medial open-wedge high-tibial osteotomy (MOWHTO) to provide sufficient structural support and a rapid osteosynthesis. We developed a novel three-dimensional (3D) printing-based platform technology using the customized 3D scaffolds covered with polycaprolactone (PCL)/β-tri-calcium phosphates (β-TCP)/bone decellularized extracellular matrix (dECM) for use as bone substitute scaffold, which can be effectively exploited to estimate the calculated correction angle with preoperative simulations. PCL/β-TCP/bone dECM scaffolds demonstrated significantly higher cell contain levels in cell seeding efficiency, excellent proliferation capacity, and promotion of early osteogenic differentiation compared with PCL/β-TCP scaffolds. The scaffolds promoted bone mineralization at the early time points of an in vivo study (8 weeks) and exhibited biodegradable properties (38% for 16 weeks). The correction angle measured after osteotomy using 3D printed scaffolds was estimated with high accuracy with low errors (10.3° ± 0.9°) and was not significantly different even in the presence of lateral cortical hinge fractures. The customized 3D scaffold enriched with PCL/β-TCP/bone dECM yielded excellent cell seeding efficiency, proliferation capacity, early osteogenic differentiation, and bone mineralization outcomes. It is expected to solve the disadvantages related to bone union in MOWHTO and to replace autografts in the future.

A Janus Microsphere Delivery System Orchestrates Immunomodulation and Osteoinduction by Fine-tuning Release Profiles

Bone regeneration is a well-orchestrated process synergistically involving inflammation, angiogenesis, and osteogenesis. Therefore, an effective bone graft should be designed to target multiple molecular events and biological demands during the bone healing process. In this study, a biodegradable gelatin methacryloyl (GelMA)-based Janus microsphere delivery system containing calcium phosphate oligomer (CPO) and bone morphogenetic protein-2 (BMP-2) is developed based on natural biological events. The exceptional adjustability of GelMA facilitates the controlled release and on-demand application of biomolecules, and optimized delivery profiles of CPO and BMP-2 are explored. The sustained release of CPO during the initial healing stages contributes to early immunomodulation and promotes mineralization in the late stage. Meanwhile, the administration of BMP-2 at a relatively high concentration within the therapeutic range enhances the osteoinductive property. This delivery system, with fine-tuned release patterns, induces M2 macrophage polarization and creates a conducive immuno-microenvironment, which in turn facilitates effective bone regeneration in vivo. Collectively, this study proposes a bottom-up concept, aiming to develop a user-friendly and easily controlled delivery system targeting individual biological events, which may offer a new perspective on developing function-optimized biomaterials for clinical use.

Enhancing osteogenesis and mandibular defect repair with magnesium-modified acellular bovine bone matrix

An acellular bovine bone matrix modified to release Magnesium ions (Mg2+) (ABBM-Mg) was prepared and evaluated for its potential in osteogenesis and mandibular defect repair. Mg2+ was incorporated into ABBM using an ion exchange method. The microstructure and mechanical properties of both ABBM and ABBM-Mg were analyzed using SEM and a biomechanical testing machine. Cytocompatibility, cell adhesion, and osteogenic differentiation were assessed using various methods including CCK-8, Live/Dead staining, SEM, ALP staining, and qPCR analysis in MC3T3-E1 cells. Additionally, a mandibular defect model in rats was established. The bone defect repair outcomes were evaluated using Micro-CT, histological HE staining, and Masson staining. The study showed that mineralization containing magnesium was redeposited on the surface of the three-dimensional porous ABBM, and the ABBM-Mg scaffold promoted cell proliferation and osteogenic differentiation compared to the ABBM scaffold. In the rat mandibular defect model, the ABBM-Mg scaffold demonstrated superior bone repair ability. This study successfully incorporated Mg2+ into ABBM without significantly affecting its microstructure and compressive strength. Furthermore, ABBM-Mg showed sustained release of Mg2+ which enhanced cell proliferation, adhesion, and osteogenic differentiation in vitro, and promoted mandibular defect healing in rats. This research opens up new possibilities for the clinical application of functionalized acellular bone matrix.

Acute Sarcopenia: Mechanisms and Management

BACKGROUND

Acute sarcopenia refers to the swift decline in muscle function and mass following acute events such as illness, surgery, trauma, or burns that presents significant challenges in hospitalized older adults.

METHODS

narrative review to describe the mechanisms and management of acute sarcopenia.

RESULTS

The prevalence of acute sarcopenia ranges from 28% to 69%, likely underdiagnosed due to the absence of muscle mass and function assessments in most clinical settings. Systemic inflammation, immune-endocrine dysregulation, and anabolic resistance are identified as key pathophysiological factors. Interventions include early mobilization, resistance exercise, neuromuscular electrical stimulation, and nutritional strategies such as protein supplementation, leucine, β-hydroxy-β-methyl-butyrate, omega-3 fatty acids, and creatine monohydrate. Pharmaceuticals show variable efficacy.

CONCLUSIONS

Future research should prioritize serial monitoring of muscle parameters, identification of predictive biomarkers, and the involvement of multidisciplinary teams from hospital admission to address sarcopenia. Early and targeted interventions are crucial to improve outcomes and prevent long-term disability associated with acute sarcopenia.

Biomimetic pulp scaffolds prepared from extracellular matrix derived from stem cells from human exfoliated deciduous teeth promote pulp-dentine complex regeneration

AIM

To evaluate the role of biomimetic pulp scaffolds derived from the extracellular matrix derived of stem cells from human exfoliated deciduous teeth (SHED-ECM-PS) in promoting pulp-dentine complex regeneration.

METHODOLOGY

SHED-ECM-PS was prepared through cell aggregation and decellularization techniques. Histological and immunofluorescence analyses, scanning electron microscopy, and DNA quantification assays were used to characterize the SHED-ECM-PS. Additionally, a tooth slice implantation model was established to evaluate the effects of SHED-ECM-PS on regeneration of the pulp-dentine complex in vivo. Extraction medium for SHED-ECM-PS was prepared, and its effect on bone marrow mesenchymal stem cells (BMMSCs) was assessed in vitro. Cell counting kit-8 and Ki-67 staining assays were performed to determine cell proliferation. The rate of apoptosis was evaluated by flow cytometry. Wound healing and transwell assays were conducted to evaluate cell migration. Alizarin red S staining was performed to examine mineralized nodule formation. Western blotting was used to detect the expression of osteogenic and odontogenic markers. The results were analysed using an independent two-tailed Student's t-test. p < .05 was considered statistically significant.

RESULTS

SHED-ECM-PS was successfully constructed, exhibiting a striped dental pulp-like shape devoid of nuclear structures or DNA components, and rich in fibronectin, collagen I, DMP1 and DSPP. Notably, SHED-ECM-PS showed no impact on the proliferation or apoptosis of BMMSCs. Histological analysis revealed that dental pulp fibroblasts formed an interwoven mesh in the root canal, and angiogenesis was observed in the SHED-ECM-PS group. Moreover, a continuous, newly formed tubular dentine layer with polarized odontoblast-like cells was observed along the inner wall of the root canal. SHED-ECM-PS promoted the migration, polar alignment and mineralized nodule formation of BMMSCs and specifically elevated the expression levels of odontogenic markers, but not osteogenic markers, compared with the control group in vitro.

CONCLUSION

SHED-ECM-PS exhibited no cytotoxicity and promoted pulp-dentine complex regeneration in vivo as well as cell migration and odontogenic differentiation of BMMSCs in vitro. These findings provide evidence that SHED-ECM-PS, as a novel biological scaffold, has the potential to improve the outcomes of REPs.

Evaluation of Articular Cartilage Regeneration Properties of Decellularized Cartilage Powder/Modified Hyaluronic Acid Hydrogel Scaffolds

The articular cartilage has poor intrinsic healing potential, hence, imposing a great challenge for articular cartilage regeneration in osteoarthritis. Tissue regeneration by scaffolds and bioactive materials has provided a healing potential for degenerated cartilage. In this study, decellularized cartilage powder (DCP) and hyaluronic acid hydrogel modified by aldehyde groups and methacrylate (AHAMA) were fabricated and evaluated in vitro for efficacy in articular cartilage regeneration. In vitro tests such as cell proliferation, cell viability, and cell migration showed that DCP/AHAMA has negligible cytotoxic effects. Furthermore, it could provide an enhanced microenvironment for infrapatellar fat pad stem cells (IFPSCs). Mechanical property tests of DCP/AHAMA showed suitable adhesive and compressive strength. IFPSCs under three-dimensional (3D) culture in DCP/AMAHA were used to assess their ability to proliferate and differentiate into chondrocytes using normal and chondroinductive media. Results exhibited increased gene expression of COL2 and ACN and decreased COL1 expression. DCP/AHAMA provides a microenvironment that recapitulates the biomechanical properties of the native cartilage, promotes chondrogenic differentiation, blocks hypertrophy, and demonstrates applicability for cartilage tissue engineering and the potential for clinical biomedical applications.

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

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

Towards Stem Cell Therapy for Critical-Sized Segmental Bone Defects: Current Trends and Challenges on the Path to Clinical Translation

The management and reconstruction of critical-sized segmental bone defects remain a major clinical challenge for orthopaedic clinicians and surgeons. In particular, regenerative medicine approaches that involve incorporating stem cells within tissue engineering scaffolds have great promise for fracture management. This narrative review focuses on the primary components of bone tissue engineering-stem cells, scaffolds, the microenvironment, and vascularisation-addressing current advances and translational and regulatory challenges in the current landscape of stem cell therapy for critical-sized bone defects. To comprehensively explore this research area and offer insights for future treatment options in orthopaedic surgery, we have examined the latest developments and advancements in bone tissue engineering, focusing on those of clinical relevance in recent years. Finally, we present a forward-looking perspective on using stem cells in bone tissue engineering for critical-sized segmental bone defects.

Use of allograft bone matrix in clinical orthopedics

Clinical orthopedics continuously aims to improve methods for bone formation. Clinical applications where bone formation is necessary include critical long bone defects in orthopedic trauma or tumor patients. Though some biomaterials combined with autologous stem cells significantly improve bone repair, critical-size damages are still challenged with the suitable implantation of biomaterials and donor cell survival. Extracellular matrix (ECM) is the fundamental structure in tissues that can nest and nourish resident cells as well as support specific functions of the tissue type. ECM also plays a role in cell signaling to promote bone growth, healing and turnover. In the last decade, the use of bone-derived ECMs or ECM-similar biomaterials have been widely investigated, including decellularized and demineralized bone ECM. In this article, we reviewed the current productions and applications of decellularized and demineralized bone matrices. We also introduce the current study of whole limb decellularization and recellularization.

Application of Decellularized Adipose Matrix as a Bioscaffold in Different Tissue Engineering

With the development of tissue engineering, the application of decellularized adipose matrix as scaffold material in tissue engineering has been intensively explored due to its wide source and excellent potential in tissue regeneration. Decellularized adipose matrix is a promising candidate for adipose tissue regeneration, while modification of decellularized adipose matrix scaffold can also allow it to transcend the limitations of adipose tissue source properties and applied to other tissue engineering fields, including cartilage and bone tissue engineering, neural tissue engineering, and skin tissue engineering. In this review, we summarized the development of the applications of decellularized adipose matrix in different tissue engineering and present future perspectives.Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Engineering a functional ACL reconstruction graft containing a triphasic enthesis-like structure in bone tunnel for the enhancement of graft-to-bone integration

Background

Anterior cruciate ligament (ACL) rupture is a common sports injury, which causes knee instability and abnormal joint kinematics. The current ACL graft was single-phasic, and not convenient for the formation of enthesis-like tissue in the bone tunnel, resulting in poor integration of graft-to-bone.

Methods

A band-shaped acellular tendon (BAT) was prepared as the core component of the ACL reconstruction graft at first, while sleeve-shaped acellular cartilage (SAC) or sleeve-shaped acellular bone (SAB) was fabricated using a vacuum aspiration system (VAS)-based decellularization protocol. The biocompatibility of the three acellular matrixes was evaluated. Furthermore, a collagen-binding peptide (CBP) derived from the A3 domain of von Willebrand factor was respectively fused into the N-terminal of GDF7, TGFβ3, or BMP2 to synthesize three recombinant growth factors capable of binding collagen (named C-GDF7, C-TGFβ3, or C-BMP2), which were respectively tethered to the BAT, SAC or SAB for improving their inducibilities in stem cell differentiation. An in-vitro experiment was performed to evaluate theirs osteogenic, chondrogenic, and tenogenic inducibilities. Then, C-TGFβ3-tethering SAC (C-TGFβ3@SAC) and C-BMP2-tethering SAB (C-BMP2@SAB) were sequentially surrounded at the bone tunnel part of C-GDF7-tethering BAT (C-GDF7@BAT), thus a sleeve-shaped acellular graft with a triphasic enthesis-like structure in bone tunnel part (named tissue-engineered graft, TE graft) was engineered. Lastly, a canine ACL reconstruction model was used to evaluate the in-vivo performance of this TE graft in enhancing graft-to-bone integration.

Results

The BAT, SAC, and SAB well preserved the structure and components of native tendon, cartilage, and bone, showing good biocompatibility. C-GDF7, C-TGFβ3, or C-BMP2 showed a stronger binding ability to BAT, SAC, and SAB. The C-GDF7@BAT, C-TGFβ3@SAC, or C-BMP2@SAB was a controlled delivery system for the scaffold-specific release of GDF7, TGFβ3, and BMP2, thus showing superior tenogenic, chondrogenic, or osteogenic inducibility, respectively. Using a canine ACL reconstruction model, abundant newly-formed bone and connective collagen fibers could be observed at the integration site between TE graft and bone tunnel at postoperative 16 weeks. Meanwhile, the failure load of the reconstructed ACL by TE graft was significantly higher than that of the autograft.

Conclusion

The TE graft could be used to reconstruct ruptured ACL and augment graft-to-bone integration, thus demonstrating high potential for clinical translation in ACL reconstruction.

Translational potential of this article

The findings of the study indicated that the TE graft could be a novel graft for ACL reconstruction with the ability to augment graft-to-bone integration, which may provide a foundation for future clinical application.

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.

Regenerative effect of microcarrier form of acellular dermal matrix versus bone matrix bio-scaffolds loaded with adipose stem cells on rat bone defect

BACKGROUND

Bone defects lead to dramatic changes in the quality of life. Acellular dermal matrix (ADM) and decellularized bone matrix (DBM) are natural scaffolds for tissue regeneration. The microcarrier scaffolds enable better vascularization and cell proliferation. This study compared the effect of microcarrier forms of DBM and ADM-loaded with adipose stem cells (ASCs) in the repair of compact bone defect in-vivo.

METHODS

Fifty-four male rats were divided into 4 groups; (i) Group (Gp) I: sham control; (ii) GpII: underwent femur bone defect induction and left to heal spontaneously; (iii) GpIII (ADM-Gp): included 2 subgroups; IIIa and IIIb: the bone defects were filled with non-loaded ADM and ADM-loaded with ASCs, respectively; (iv) GpIV (DBM-Gp): included 2 subgroups; IVa and IVb: the bone defects were filled with non-loaded DBM and DBM-loaded with ASCs, respectively. Animals were euthanized after 1, 2 and 3 months and their femur sections were stained with H&E, Masson's trichrome and immunohistochemistry for CD31, osteopontin and osteocalcin.

RESULTS

Histological analysis illustrated limited bone regeneration in the cortical defect of GpII after 3 months. The histomorphometric analysis showed significant delayed mature collagen deposition as well as CD31, osteopontin and osteocalcin expression. Superior capacity of new bone regeneration was detected with bio-scaffold micro-carriers; loaded or non-loaded with ASCs. However, DBM-loaded with ASCs displayed enhanced regeneration properties confirmed by the apparently normal architecture of the new bone and accelerated expression of CD31, osteopontin and osteocalcin in the regenerated bone after 3 months.

CONCLUSIONS

We concluded that decellularized scaffolds significantly improved compact bone regeneration with superiority of ASCs seeded-bone scaffolds.

Safety and tissue remodeling assay of small intestinal submucosa meshes using a modified porcine surgical hernia model

In studies to date, meshes based on extracellular matrix (ECM) have been extensively used in clinical applications. Unfortunately, little is known about the function of the immunogenic residual, absorbable profile during the tissue repair process. Moreover, there needs to be a recognized preclinical animal model to investigate the safety and efficacy of extracellular matrix meshes. Herein, we designed and fabricated a kind of SIS mesh followed by a scanned electron micrograph characterization and tested α-Gal antigen clearance rate and DNA residual. In order to prove the biocompatibility of the SIS mesh, cell viability, chemotaxis assay and local tissue reaction were assessed by MTT and RTCA cytotoxicity test in vitro as well as implantation and degradation experiments in vivo. Furthermore, we developed a stable preclinical animal model in the porcine ventral hernia repair investigation, which using laparoscopic plus open hybridization method to evaluate tissue adhesion, explant mechanical performance, and histologic analysis after mesh implantation. More importantly, we established a semi-quantitative scoring system to examine the ECM degradation, tissue remodeling and regeneration in the modified porcine surgical hernia model for the first time. Our results highlight the application prospect of the improved porcine ventral hernia model for the safety and efficacy investigation of hernia repair meshes.

Bioactive decellularized adipose matrix prepared using a rapid, nonchemical/enzymatic method for adipogenesis

Recent developments in the field of regenerative surgeries and medical applications have led to a renewed interest in adipose tissue-enriched mesenchymal stem cell scaffolds. Various advantages declared for the decellularized adipose matrix (DAM) have caused its extensive use in the transfer of stem cells or growth factors for soft tissue regeneration induction. Meanwhile, the long-term application of detergents toward DAM regeneration has been assumed as a risky obstacle in this era. Herein, a rapid, mechanical protocol was developed to prepare DAM (M-DAM) without chemicals/enzymes and was comprehensively compared with the ordinary DAM (traditional chemical method). Accordingly, this method could effectively hinder oils and cells, sustain the structural and biological elements, and contain a superior level of collagen content. In addition, more protein numbers, as well as higher basement membrane elements, glycoproteins, and extracellular matrix-related proteins were detected in the regenerated M-DAM. Also, superior adipogenesis and angiogenesis proteins were distinguished. The noncytotoxicity of the M-DAM was also approved, and a natural ecological niche was observed for the proliferation and differentiation of stem cells, confirming its great potential for vascularization and adipogenesis in vivo. The suggested technique could effectively prepare the modified DAM in variant constructions of tablets, powders, emulsions, hydrogels, and different three-dimensional-printed structures. Hence, this rapid, mechanical process can produce bioactive DAM, which has the potential to be widely used in various research fields of regenerative medicine.

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.

Controllable and biocompatible 3D bioprinting technology for microorganisms: Fundamental, environmental applications and challenges

3D bioprinting is a new 3D manufacturing technology, that can be used to accurately distribute and load microorganisms to form microbial active materials with multiple complex functions. Based on the 3D printing of human cells in tissue engineering, 3D bioprinting technology has been developed. Although 3D bioprinting technology is still immature, it shows great potential in the environmental field. Due to the precise programming control and multi-printing pathway, 3D bioprinting technology provides a high-throughput method based on micron-level patterning for a wide range of environmental microbiological engineering applications, which makes it an on-demand, multi-functional manufacturing technology. To date, 3D bioprinting technology has been employed in microbial fuel cells, biofilm material preparation, microbial catalysts and 4D bioprinting with time dimension functions. Nevertheless, current 3D bioprinting technology faces technical challenges in improving the mechanical properties of materials, developing specific bioinks to adapt to different strains, and exploring 4D bioprinting for intelligent applications. Hence, this review systematically analyzes the basic technical principles of 3D bioprinting, bioinks materials and their applications in the environmental field, and proposes the challenges and future prospects of 3D bioprinting in the environmental field. Combined with the current development of microbial enhancement technology in the environmental field, 3D bioprinting will be developed into an enabling platform for multifunctional microorganisms and facilitate greater control of in situ directional reactions.

Aligned skeletal muscle assembly on a biofunctionalized plant leaf scaffold

Decellularized plant scaffolds have drawn attention as alternative tissue culture platforms due to their wide accessibility, biocompatibility, and diversity of innate microstructures. Particularly, in this work, monocot leaves with innate uniaxial micropatterned topography were utilized to promote cell alignment and elongation. The leaf scaffold was biofunctionalized with poly(PEGMEMA-r-VDM-r-GMA) copolymer that prevented non-specific protein adsorption and was modified with cell adhesive RGD peptide to enable cell adhesion and growth in serum-free media. The biofunctionalized leaf supported the adhesion, growth, and alignment of various human cells including embryonic stem cells (hESC) derived muscle cells. The hESC-derived myogenic progenitor cells cultured on the biofunctionalized leaf scaffold adopted a parallel orientation and were elongated along the leaf topography. These cells showed significant early myogenic differentiation and muscle-like bundled myotube formation. The aligned cells formed compact myotube assemblies and showed uniaxial muscle contraction under chemical stimulation, a critical requirement for developing functional skeletal muscle tissue. Polymer-functionalized plant leaf scaffolds offer a novel human cell culture platform and have potential in human tissue engineering applications that require parallel alignment of cells. STATEMENT OF SIGNIFICANCE: Plant scaffolds are plentiful sources in nature and present a prefabricated construct to present topographical cues to cells. Their feature width is ideal for human cell alignment and elongation, especially for muscle cells. However, plant scaffolds lack proteins that support mammalian cell culture. We have developed a polymer coated leaf scaffold that enables cell adhesion and growth in serum-free media. Human muscle cells cultured on the biofunctionalized leaf, aligned along the natural parallel micro-patterned leaf topography, and formed muscle-like bundled myotube assemblies. These assemblies showed uniaxial muscular contraction, a critical requirement for developing functional skeletal muscle tissue. The biodiversity of the plant materials offers a novel human cell culture platform with potential in human tissue engineering.

Cost-effectiveness of decellularised bone allograft compared with fresh-frozen bone allograft for acetabular impaction bone grafting during a revision hip arthroplasty in the UK

OBJECTIVES

Fresh-frozen allograft is the gold-standard bone graft material used during revision hip arthroplasty. However, new technology has been developed to manufacture decellularised bone with potentially better graft incorporation. As these grafts cost more to manufacture, the aim of this cost-effectiveness study was to estimate whether the potential health benefit of decellularised bone allograft outweighs their increased cost.

STUDY DESIGN

A Markov model was constructed to estimate the costs and the quality-adjusted life years of impaction bone grafting during a revision hip arthroplasty.

SETTING

This study took the perspective of the National Health Service in the UK.

PARTICIPANTS

The Markov model includes patients undergoing a revision hip arthroplasty in the UK.

INTERVENTION

Impaction bone grafting during a revision hip arthroplasty using either decellularised bone allograft or fresh-frozen allograft.

MEASURES

Outcome measures included: total costs and quality-adjusted life years of both interventions over the lifetime of the model; and incremental cost-effectiveness ratios for both graft types, using base case parameters, univariate sensitivity analysis and probabilistic analysis.

RESULTS

The incremental cost-effectiveness ratio for the base case model was found to be £270 059 per quality-adjusted life year. Univariate sensitivity analysis found that changing the discount rate, the decellularised bone graft cost, age of the patient cohort and the revision rate all had a significant effect on the incremental cost-effectiveness ratio.

CONCLUSIONS

As there are no clinical studies of impaction bone grafting using a decellularised bone allograft, there is a high level of uncertainty around the costs of producing a decellularised bone allograft and the potential health benefits. However, if a decellularised bone graft was manufactured for £2887 and lowered the re-revision rate to less than 64 cases per year per 10 000 revision patients, then it would most likely be cost-effective compared with fresh-frozen allograft.

Biomimetic approach for an articular cartilage patch: Combination of decellularized cartilage matrix and silk-elastin-like-protein (SELP) hydrogel

Articular cartilage degradation due to injury, disease and aging is a common clinical issue as current regenerative therapies are unable to fully replicate the complex microenvironment of the native tissue which, being avascular, is featured by very low ability to self-regenerate. The extracellular matrix (ECM), constituting almost 90% of the entire tissue, plays a critical role in its function and resistance to compressive forces. In this context, the current tissue engineering strategies are only partially effective in restoring the biology and function of the native tissue. A main issue in tissue regeneration is treatment failure due to scarce integration of the engineered construct, often following a gradual detachment of the graft. In this scenario, we aimed to create an adhesive patch able to adequately support cartilage regeneration as a promising tool for the treatment of cartilage injuries and diseases. For this, we produced an engineered construct composed of decellularized ECM (dECM) obtained from horse joint cartilage, to support tissue regeneration, coupled with a Silk-Elastin-Like Proteins (SELP) hydrogel, which acts as a biological glue, to guarantee an adequate adherence to the host tissue. Following the production of the two biomaterials we characterized them by assessing: 1) dECM morphological, chemical, and ultrastructural features along with its capability to support chondrocyte proliferation, specific marker expression and ECM synthesis; 2) SELP microarchitecture, cytocompatibility and mechanical properties. Our results demonstrated that both materials hold unique properties suitable to be exploited to produce a tailored microenvironment to support cell growth and differentiation providing a proof of concept concerning the in vitro biological and mechanical efficacy of the construct. The SELP hydrogel displayed a very interesting physical behavior due to its high degree of resistance to mechanical stress, which is generally associated with physiological mechanical load during locomotion. Intriguingly, the shear-thinning behavior of the hydrogel may also make it suitable to be applied and spread over non-homogeneous surfaces, therefore, we hypothesize that the hybrid biomaterial proposed may be a real asset in the treatment of cartilage defects and injuries.

A Bibliometric Analysis of Research on Decellularized Matrix for Two Decades

The articles and reviews in the field of decellularized extracellular matrix (dECM) from 2001 to 2021 were retrieved and extracted from the Web of Science Core Collection. The R package Bibliometrix, CiteSpace, VOSviewer, and the online BIBLIOMETRC platform were utilized for bibliometric analysis, including specific characteristics of annual publications, influential countries/regions, core journals, leading institutions, keywords, key references, cocited authors, journals and institutions, cooperation, and historical direct citations. Our study concluded core references that fueled the development of dECM and highlighted current research directions, hotpots, and trends. From 2001 to 2021, 3,046 publications were retrieved in total, including 2,700 articles and 349 reviews. The United States (n = 895) produced the majority of publications, and the University of Pittsburgh (n = 318) published most productions. Biomaterials were identified as the most productive and influential journal in the dECM field considering the number of publications (n = 194), and total citations (n = 15,694). Immunomodulation, bioreactors, aging, three-dimensional (3D) bioprinting, bone tissue engineering, bioink, hydrogel, biomaterials, and regeneration were the latest high-frequency keywords, indicating the emerging frontiers of dECM. In the field, decellularization techniques lay the foundation. Orthotopic transplantation of recellularized dECM and induction of specific cell differentiation promoted the bursts of research. The 3D bioprinting and hydrogel based on dECM were extensively studied in recent years. The present study provided developmental trajectories, current research status, global collaboration patterns, hotpots, and trending topics of dECM. Decellularization techniques, tissue engineering to regenerate organs, and improvements in application are the major themes over the past two decades. Impact Statement The review article is significant because decellularized extracellular matrix (dECM), which derived from biological tissues and removal of immunogenic cells, is characterized by safety, biocompatibility, and low in toxicity. Showing great application prospects, dECM has been applied in multiple scenarios of tissue repairment and reconstruction, among the most popular topics in tissue engineering. Thus, analyzing and concluding the development, current condition and future trends are of great significance. Comparing to conventional review, this review article systemically and comprehensively concluded the historical development, current status, and research trending topics. Thus, it allows scholars to get a rapid overview of the dECM field, and plan research directions.

Partial decellularization eliminates immunogenicity in tracheal allografts

There is currently no suitable autologous tissue to bridge large tracheal defects. As a result, no standard of care exists for long-segment tracheal reconstruction. Tissue engineering has the potential to create a scaffold from allografts or xenografts that can support neotissue regeneration identical to the native trachea. Recent advances in tissue engineering have led to the idea of partial decellularization that allows for the creation of tracheal scaffolds that supports tracheal epithelial formation while preserving mechanical properties. However, the ability of partial decellularization to eliminate graft immunogenicity remains unknown, and understanding the immunogenic properties of partially decellularized tracheal grafts (PDTG) is a critical step toward clinical translation. Here, we determined that tracheal allograft immunogenicity results in epithelial cell sloughing and replacement with dysplastic columnar epithelium and that partial decellularization creates grafts that are able to support an epithelium without histologic signs of rejection. Moreover, allograft implantation elicits CD8+ T-cell infiltration, a mediator of rejection, while PDTG did not. Hence, we establish that partial decellularization eliminates allograft immunogenicity while creating a scaffold for implantation that can support spatially appropriate airway regeneration.

Functionalized Decellularized Bone Matrix Promotes Bone Regeneration by Releasing Osteogenic Peptides

The decellularized bone matrix (DCB) provides a promising bone substitute for the treatment of bone defects because of its similar biochemical, biophysical, and mechanical properties to normal bone tissue. However, the decellularized procedure also greatly reduced its osteogenic induction activity. In this study, peptides derived from the knuckle epitope of bone morphogenetic protein-2 were incorporated into the thermo-sensitive hydrogel poloxamer 407, and the peptide-loaded hydrogel was then filled into the pores of DCB to construct a functionalized scaffold with enhanced osteogenesis. In vitro studies have shown that the functionalized DCB scaffold possessed appropriate mechanical properties and biocompatibility and exhibited a sustained release profile of osteogenic peptide. These performances critically facilitated cell proliferation and cell spreading of bone marrow mesenchymal stem cells and upregulated the expression of osteogenic-related genes by activating the Smad/Runx2 signaling pathway, thereby promoting osteogenic differentiation and extracellular matrix mineralization. Further in vivo studies demonstrated that the functionalized DCB scaffold accelerated the repair of critical radial defects in rabbits without inducing excessive graft-related inflammatory responses. These results suggest a clinically meaningful strategy for the treatment of large segmental bone defects, and the prepared osteogenic peptide modified composite DCB scaffold has great application potential for bone regeneration.

Endogenous Regeneration of Alveolar Bone by Decellularized Tooth Matrix

The efficiency of bone tissue regeneration by decellularized tooth matrix, demineralized tooth matrix, and commercial xenograft Bio-Oss Spongiosa was compared on the model of a critical-size circular defect in the alveolar bone of the upper jaw of adult Wistar rats. The defect healing dynamics was assessed using histological, histomorphometrical, and immunohistochemical methods on days 30 and 60. In contrast to demineralized matrix and commercial xenograft, decellularized matrix induces the formation of the new bone tissue by day 60. Decellularized matrix can be considered as a biomaterial for cell-free tissue engineering for alveolar bone restoration in dentistry and maxillofacial surgery.

Extracellular Matrix-Based and Electrospun Scaffolding Systems for Vaginal Reconstruction

Congenital vaginal anomalies and pelvic organ prolapse affect different age groups of women and both have significant negative impacts on patients' psychological well-being and quality of life. While surgical and non-surgical treatments are available for vaginal defects, their efficacy is limited, and they often result in long-term complications. Therefore, alternative treatment options are urgently needed. Fortunately, tissue-engineered scaffolds are promising new treatment modalities that provide an extracellular matrix (ECM)-like environment for vaginal cells to adhere, secrete ECM, and be remodeled by host cells. To this end, ECM-based scaffolds or the constructs that resemble ECM, generated by self-assembly, decellularization, or electrospinning techniques, have gained attention from both clinicians and researchers. These biomimetic scaffolds are highly similar to the native vaginal ECM and have great potential for clinical translation. This review article aims to discuss recent applications, challenges, and future perspectives of these scaffolds in vaginal reconstruction or repair strategies.

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.

Elastic moduli of polyelectrolyte multilayer films regulate endothelium-blood interaction under dynamic conditions

A broad spectrum of biomaterials has been explored in order to design cardiovascular implants of sufficient hemocompatibility. Most of them were extensively tested for the ability to facilitate repopulation by patient cells. It was shown that stiffness, surface roughness, or hydrophilicity of polyelectrolyte films have an impact on adhesion, proliferation, and differentiation of cells. At the same time, it is still unknown how these properties influence cell functionality and as a consequence interactions with blood components under dynamic conditions. In this study, we aimed to determine the impact of chemical cross-linking of Chitosan (Chi) and Chrondroitin Sulphate (CS) on endothelium-blood cross-talk. We have found that the morphology of the endothelium monolayer was not altered by changes in coating properties. However, free radical generation by endothelial cells varied depending on the elastic properties of the coating. Simultaneously, we have observed a significant decrease in the level of adhering and circulating active platelets as well as aggregates when the endothelium monolayer was formed on stiffer films than on the other coating variants. Moreover, the same type of films has promoted significantly higher adhesion of blood morphotic elements when they were not functionalized by endothelium. The observed changes in hemocompatibility indicate the importance of a design of coatings that will promote cellularization in vivo in a relatively short time and which will regulate cell function.

Advances in Cartilage Tissue Engineering Using Bioinks with Decellularized Cartilage and Three-Dimensional Printing

Osteoarthritis, a chronic, debilitating, and painful disease, is one of the leading causes of disability and socioeconomic burden, with an estimated 250 million people affected worldwide. Currently, there is no cure for osteoarthritis and treatments for joint disease require improvements. To address the challenge of improving cartilage repair and regeneration, three-dimensional (3D) printing for tissue engineering purposes has been developed. In this review, emerging technologies are presented with an overview of bioprinting, cartilage structure, current treatment options, decellularization, bioinks, and recent progress in the field of decellularized extracellular matrix (dECM)–bioink composites is discussed. The optimization of tissue engineering approaches using 3D-bioprinted biological scaffolds with dECM incorporated to create novel bioinks is an innovative strategy to promote cartilage repair and regeneration. Challenges and future directions that may lead to innovative improvements to currently available treatments for cartilage regeneration are presented.

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

Cell source is the key to decellularized matrix (DM) strategy. This study compared 3 cell types, osteocytes with/without dominant active Wnt/β-catenin signaling (daCO and WTO) and bone marrow stromal cells (BMSCs) for their DMs in bone repair. Decellularization removes all organelles and >95% DNA, and retained >74% collagen and >71% GAG, maintains the integrity of cell basement membrane with dense boundaries showing oval and honeycomb structure in osteocytic DM and smooth but irregular shape in the BMSC-DM. DM produced higher cell survival rate (90%) and higher proliferative activity. In vitro, daCO-DM induces more and longer stress fibers in BMSCs, conducive to cell adhesion, spreading, and osteogenic differentiation. 8-wk after implantation of the critical-sized parietal bone defect model, daCO-DM formed tight structures, composed of a large number of densely-arranged type-I collagen under polarized light microscope, which is similar to and integrated with host bone. BV/TV (>54%) was 1.5, 2.9, and 3.5 times of WTO-DM, BMSC-DM, and none-DM groups, and N.Ob/T.Ar (3.2 × 10²/mm²) was 1.7, 2.9, and 3.3 times. At 4-wk, daCO-DM induced osteoclastogenesis, 2.3 times higher than WTO-DM; but BMSC-DM or none-DM didn't. daCO-DM increased the expression of RANKL and MCSF, Vegfa and Angpt1, and Ngf in BMSCs, which contributes to osteoclastogenesis, angiogenesis, and neurogenesis, respectively. daCO-DM promoted H-type vessel formation and nerve markers β3-tubulin and NeuN expression. Conclusion: daCO-DM produces metabolic and neurovascularized organoid bone to accelerate the repair of bone defects. These features are expected to achieve the effect of autologous bone transplantation, suitable for transformation application.

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Decellularized matrix of osteocytes with dominant-active β-catenin (daCO-DM) promotes osteogenesis for regenerative repair.

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daCO-DM induces BMSCs to form stress fibers, conducive to cell adhesion, spreading, and differentiation towards osteoblasts.

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daCO-DM-induced osteoblasts have strong activity secreting dense and orderly-arranged type I collagen as host bone’s.

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daCO-DM induces BMSCs to express pre-osteoclastogenic cytokine RANKL and MCSF for osteoclastogenesis of marrow monocytes.

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daCO-DM enhances BMSCs to express angiogenic Vegfa and Angpt1, and neurogenic Ngf potentially for neurovascularization.

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.

Biomedical applications of three-dimensional bioprinted craniofacial tissue engineering

Anatomical complications of the craniofacial regions often present considerable challenges to the surgical repair or replacement of the damaged tissues. Surgical repair has its own set of limitations, including scarcity of the donor tissues, immune rejection, use of immune suppressors followed by the surgery, and restriction in restoring the natural aesthetic appeal. Rapid advancement in the field of biomaterials, cell biology, and engineering has helped scientists to create cellularized skeletal muscle-like structures. However, the existing method still has limitations in building large, highly vascular tissue with clinical application. With the advance in the three-dimensional (3D) bioprinting technique, scientists and clinicians now can produce the functional implants of skeletal muscles and bones that are more patient-specific with the perfect match to the architecture of their craniofacial defects. Craniofacial tissue regeneration using 3D bioprinting can manage and eliminate the restrictions of the surgical transplant from the donor site. The concept of creating the new functional tissue, exactly mimicking the anatomical and physiological function of the damaged tissue, looks highly attractive. This is crucial to reduce the donor site morbidity and retain the esthetics. 3D bioprinting can integrate all three essential components of tissue engineering, that is, rehabilitation, reconstruction, and regeneration of the lost craniofacial tissues. Such integration essentially helps to develop the patient-specific treatment plans and damage site-driven creation of the functional implants for the craniofacial defects. This article is the bird's eye view on the latest development and application of 3D bioprinting in the regeneration of the skeletal muscle tissues and their application in restoring the functional abilities of the damaged craniofacial tissue. We also discussed current challenges in craniofacial bone vascularization and gave our view on the future direction, including establishing the interactions between tissue-engineered skeletal muscle and the peripheral nervous system.

Macromolecular crowding in animal component-free, xeno-free and foetal bovine serum media for human bone marrow mesenchymal stromal cell expansion and differentiation

Background: Cell culture media containing undefined animal-derived components and prolonged in vitro culture periods in the absence of native extracellular matrix result in phenotypic drift of human bone marrow stromal cells (hBMSCs). Methods: Herein, we assessed whether animal component-free (ACF) or xeno-free (XF) media formulations maintain hBMSC phenotypic characteristics more effectively than foetal bovine serum (FBS)-based media. In addition, we assessed whether tissue-specific extracellular matrix, induced via macromolecular crowding (MMC) during expansion and/or differentiation, can more tightly control hBMSC fate. Results: Cells expanded in animal component-free media showed overall the highest phenotype maintenance, as judged by cluster of differentiation expression analysis. Contrary to FBS media, ACF and XF media increased cellularity over time in culture, as measured by total DNA concentration. While MMC with Ficoll™ increased collagen deposition of cells in FBS media, FBS media induced significantly lower collagen synthesis and/or deposition than the ACF and XF media. Cells expanded in FBS media showed higher adipogenic differentiation than ACF and XF media, which was augmented by MMC with Ficoll™ during expansion. Similarly, Ficoll™ crowding also increased chondrogenic differentiation. Of note, donor-to-donor variability was observed for collagen type I deposition and trilineage differentiation capacity of hBMSCs. Conclusion: Collectively, our data indicate that appropriate screening of donors, media and supplements, in this case MMC agent, should be conducted for the development of clinically relevant hBMSC medicines.

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.

Automated Assessment of Cell Infiltration and Removal in Decellularized Scaffolds - Experimental Study in Rabbits

Objective  Semiquantitative and automated measurement of nuclear material removal and cell infiltration in decellularized tendon scaffolds (DTSs). Method  16 pure New Zealand rabbits were used, and the gastrocnemius muscle tendon was collected bilaterally from half of these animals (16 tendons collected); 4 were kept as control and 12 were submitted to the decellularization protocol (DTS). Eight of the DTSs were used as an in vivo implant in the experimental rotator cuff tear (RCT) model, and the rest, as well as the controls, were used in the semiquantitative and automated evaluation of nuclear material removal. The eight additional rabbits were used to make the experimental model of RCT and subsequent evaluation of cellular infiltration after 2 or 8 weeks, within the DTS. Results  The semiquantitative and automated analysis used demonstrated a removal of 79% of nuclear material ( p  < 0.001 and power > 99%) and a decrease of 88% (p < 0.001 and power >99%) in the area occupied by nuclear material after the decellularization protocol. On cell infiltration in DTS, an increase of 256% (p < 0.001 and power >99%) in the number of cells within the DTS was observed in the comparison between 2 and 8 weeks postoperatively. Conclusion  The proposed semiquantitative and automated measurement method was able to objectively measure the removal of nuclear material and cell infiltration in DTS.

Improvement of the cell viability of hepatocytes cultured in three-dimensional collagen gels using pump-free perfusion driven by water level difference

Cell-containing collagen gels are one of the materials employed in tissue engineering and drug testing. A collagen gel is a useful three-dimensional (3D) scaffold that improves various cell functions compared to traditional two-dimensional plastic substrates. However, owing to poor nutrient availability, cells are not viable in thick collagen gels. Perfusion is an effective method for supplying nutrients to the gel. In this study, we maintained hepatocytes embedded in a 3D collagen gel using a simple pump-free perfusion cell culture system with ordinary cell culture products. Flow was generated by the difference in water level in the culture medium. Hepatocytes were found to be viable in a collagen gel of thickness 3.26 (± 0.16 S.E.)-mm for 3 days. In addition, hepatocytes had improved proliferation and gene expression related to liver function in a 3D collagen gel compared to a 2D culture dish. These findings indicate that our perfusion method is useful for investigating the cellular functions of 3D hydrogels.

Synthetic materials in craniofacial regenerative medicine: A comprehensive overview

The state-of-the-art approach to regenerating different tissues and organs is tissue engineering which includes the three parts of stem cells (SCs), scaffolds, and growth factors. Cellular behaviors such as propagation, differentiation, and assembling the extracellular matrix (ECM) are influenced by the cell's microenvironment. Imitating the cell's natural environment, such as scaffolds, is vital to create appropriate tissue. Craniofacial tissue engineering refers to regenerating tissues found in the brain and the face parts such as bone, muscle, and artery. More biocompatible and biodegradable scaffolds are more commensurate with tissue remodeling and more appropriate for cell culture, signaling, and adhesion. Synthetic materials play significant roles and have become more prevalent in medical applications. They have also been used in different forms for producing a microenvironment as ECM for cells. Synthetic scaffolds may be comprised of polymers, bioceramics, or hybrids of natural/synthetic materials. Synthetic scaffolds have produced ECM-like materials that can properly mimic and regulate the tissue microenvironment's physical, mechanical, chemical, and biological properties, manage adherence of biomolecules and adjust the material's degradability. The present review article is focused on synthetic materials used in craniofacial tissue engineering in recent decades.

Decellularized Extracellular Matrix-Based Bioinks for Tendon Regeneration in Three-Dimensional Bioprinting

In the last few years, attempts to improve the regeneration of damaged tendons have been rising due to the growing demand. However, current treatments to restore the original performance of the tissue focus on the usage of grafts; although, actual grafts are deficient because they often cannot provide enough support for tissue regeneration, leading to additional complications. The beneficial effect of combining 3D bioprinting and dECM as a novel bioink biomaterial has recently been described. Tendon dECMs have been obtained by using either chemical, biological, or/and physical treatments. Although decellularization protocols are not yet standardized, recently, different protocols have been published. New therapeutic approaches embrace the use of dECM in bioinks for 3D bioprinting, as it has shown promising results in mimicking the composition and the structure of the tissue. However, major obstacles include the poor structural integrity and slow gelation properties of dECM bioinks. Moreover, printing parameters such as speed and temperature have to be optimized for each dECM bioink. Here, we show that dECM bioink for 3D bioprinting provides a promising approach for tendon regeneration for future clinical applications.

Proteomic Analysis of Decellularized Extracellular Matrix: Achieving a Competent Biomaterial for Osteogenesis

Decellularized ECMs have been used as biological scaffolds for tissue repair due to their tissue-specific biochemical and mechanical composition, poorly simulated by other materials. It is used as patches and powders, and it could be further processed via enzymatic digestion under acidic conditions using pepsin. However, part of the bioactivity is lost during the digestion process due to protein denaturation. Here, stepwise digestion was developed to prepare a competent biomaterial for osteogenesis from three different ECM sources. In addition, three different proteases were compared to evaluate the most effective digestion protocol for specific cellular processes. GAGs and peptide quantification showed that the stepwise method yielded a higher concentration of bioactive residues. Circular dichroism analysis also showed that the stepwise approach preserved the secondary structures better. The protein profiles of the digested ECMs were analyzed, and it was found to be highly diverse and tissue-specific. The digestion of ECM from pericardium produced peptides originated from 94 different proteins, followed by 48 proteins in ECM from tendon and 35 proteins in ECM from bone. In addition, digested products from pericardium ECM yielded increased proliferation and differentiation of bone marrow mesenchymal stem cells to mature osteoblasts.

Engineering an enthesis-like graft for rotator cuff repair: An approach to fabricate highly biomimetic scaffold capable of zone-specifically releasing stem cell differentiation inducers

Rotator cuff (RC) attaches to humerus across a triphasic yet continuous tissue zones (bone-fibrocartilage-tendon), termed "enthesis". Regrettably, rapid and functional enthesis regeneration is challenging after RC tear. The existing grafts bioengineered for RC repair are insufficient, as they were engineered by a scaffold that did not mimic normal enthesis in morphology, composition, and tensile property, meanwhile cannot simultaneously stimulate the formation of bone-fibrocartilage-tendon tissues. Herein, an optimized decellularization approach based on a vacuum aspiration device (VAD) was developed to fabricate a book-shaped decellularized enthesis matrix (O-BDEM). Then, three recombinant growth factors (CBP-GFs) capable of binding collagen were synthesized by fusing a collagen-binding peptide (CBP) into the N-terminal of BMP-2, TGF-β3, or GDF-7, and zone-specifically tethered to the collagen of O-BDEM to fabricate a novel scaffold (CBP-GFs/O-BDEM) satisfying the above-mentioned requirements. After ensuring the low immunogenicity of CBP-GFs/O-BDEM by a novel single-cell mass cytometry in a mouse model, we interleaved urine-derived stem cell-sheets into this CBP-GFs/O-BDEM to bioengineer an enthesis-like graft. Its high-performance on regenerating enthesis was determined in a canine model. These findings indicate this CBP-GFs/O-BDEM may be an excellent scaffold for constructing enthesis-like graft to patch large/massive RC tears, and provide breakthroughs in fabricating graded interfacial tissue.

Strategy of a cell-derived extracellular matrix for the construction of an osteochondral interlayer

Osteochondral defects pose an enormous challenge due to the lack of an effective repair strategy. To tackle this issue, the importance of a calcified cartilage interlayer (CCL) in modulating osteochondral regeneration should be valued. Herein, we proposed that an extracellular matrix (ECM) derived from a suitable cell source might efficiently promote the formation of calcified cartilage. To the end, cell sheets from four kinds of cells, including bone marrow mesenchymal stem cells (BMSCs), pre-osteoblasts (MC3T3), chondrocytes (Cho), and artificially induced hypertrophic chondrocytes (HCho), were obtained by seeding the cells on electrospun fibrous meshes, followed by decellularization to prepare decellularized ECMs (D-ECMs) for BMSC re-seeding and differentiation studies. For cell proliferation, the BMSC-derived D-ECM exhibited the strongest promotion effect. For inducing the hypertrophic phenotype of re-seeded BMSCs, both the BMSC-derived and HCho-derived D-ECMs demonstrated stronger capacity in up-regulating the depositions of related proteins and the expressions of marker genes, as compared to the MC3T3-derived and Cho-derived D-ECMs. Accordingly, from the histological results of their subcutaneous implantation in rats, both the BMSC-derived and HCho-derived D-ECMs displayed obvious Masson's trichrome and Safranin-O/Fast-Green staining colors simultaneously, representing the characteristics related to osteogenesis and chondrogenesis. Differently, MC3T3-derived and Cho-derived D-ECMs were mainly detected during the osteogenic or chondrogenic expression, respectively. These findings confirmed that the BMSC-derived D-ECM could induce hypertrophic chondrocytes, though being a little inferior to the HCho-derived D-ECM. Overall, the BMSC-derived D-ECM could be a potential material in constructing the interlayer for osteochondral tissue engineering scaffolds to improve the regeneration efficiency.

Elastic Fibers in the Intervertebral Disc: From Form to Function and toward Regeneration

Despite extensive efforts over the past 40 years, there is still a significant gap in knowledge of the characteristics of elastic fibers in the intervertebral disc (IVD). More studies are required to clarify the potential contribution of elastic fibers to the IVD (healthy and diseased) function and recommend critical areas for future investigations. On the other hand, current IVD in-vitro models are not true reflections of the complex biological IVD tissue and the role of elastic fibers has often been ignored in developing relevant tissue-engineered scaffolds and realistic computational models. This has affected the progress of IVD studies (tissue engineering solutions, biomechanics, fundamental biology) and translation into clinical practice. Motivated by the current gap, the current review paper presents a comprehensive study (from the early 1980s to 2022) that explores the current understanding of structural (multi-scale hierarchy), biological (development and aging, elastin content, and cell-fiber interaction), and biomechanical properties of the IVD elastic fibers, and provides new insights into future investigations in this domain.