Controlling stem cell behavior with decellularized extracellular matrix scaffolds

The effect of epididymosomes on the development of frozen-thawed mouse spermatogonial stem cells after culture in a decellularized testicular scaffold and transplantation into azoospermic mice

PURPOSE

This study examined SSC proliferation on an epididymosome-enriched decellularized testicular matrix (DTM) hydrogel and spermatogenesis induction in azoospermic mice.

METHODS

Epididymosomes were extracted and characterized using SEM and western blotting. After cryopreservation, thawed SSCs were cultured in a hydrogel-based three-dimensional (3D) culture containing 10 ng/mL GDNF or 20 µg/mL epididymosomes. SSCs were assessed using the MTT assay, flow cytometry, and qRT-PCR after two weeks of culture. The isolated SSCs were microinjected into the efferent ducts of busulfan-treated mice. DiI-labeled SSCs were followed, and cell homing was assessed after two weeks. After 8 weeks, the testes were evaluated using morphometric studies and immunohistochemistry.

RESULTS

The expression of PLZF, TGF-β, and miR-10b did not increase statistically significantly in the 3D + GDNF and 3D + epididymosome groups compared to the 3D group. Among the groups, the GDNF-treated group exhibited the highest expression of miR-21 (*P < 0.05). Caspase-3 expression was lower in the epididymosome-treated group than in the other groups (***P < 0.001). Compared to the 3D and negative control groups, the 3D + epididymosomes and 3D + GDNF groups showed an increase in spermatogenic cells. Immunohistochemical results confirmed the growth and differentiation of spermatogonial cells into spermatids in the treatment groups.

CONCLUSION

The DTM hydrogel containing 20 µg/mL epididymosomes or 10 ng/mL GDNF is a novel and safe culture system that can support SSC proliferation in vitro to obtain adequate SSCs for transplantation success. It could be a novel therapeutic agent that could recover deregulated SSCs in azoospermic patients.

Binary Fabrication of Decellularized Lung Extracellular Matrix Hybridgels for in vitro Chronic Obstructive Pulmonary Disease Modeling

Limited treatments and a lack of appropriate animal models have spurred the study of scaffolds to mimic lung disease in vitro. Decellularized human lung and its application in extracellular matrix (ECM) hydrogels has advanced the development of these lung ECM models. Controlling the biochemical and mechanical properties of decellularized ECM hydrogels continues to be of interest due to inherent discrepancies of hydrogels when compared to their source tissue. To optimize the physiologic relevance of ECM hydrogel lung models without sacrificing the native composition we engineered a binary fabrication system to produce a Hybridgel composed of an ECM hydrogel reinforced with an ECM cryogel. Further, we compared the effect of ECM-altering disease on the properties of the gels using elastin poor Chronic Obstructive Pulmonary Disease (COPD) vs non-diseased (ND) human lung source tissue. Nanoindentation confirmed the significant loss of elasticity in hydrogels compared to that of ND human lung and further demonstrated the recovery of elastic moduli in ECM cryogels and Hybridgels. These findings were supported by similar observations in diseased tissue and gels. Successful cell encapsulation, distribution, cytotoxicity, and infiltration were observed and characterized via confocal microscopy. Cells were uniformly distributed throughout the Hybridgel and capable of survival for 7 days. Cell-laden ECM hybridgels were found to have elasticity similar to that of ND human lung. Compositional investigation into diseased and ND gels indicated the conservation of disease-specific elastin to collagen ratios. In brief, we have engineered a composited ECM hybridgel for the 3D study of cell-matrix interactions of varying lung disease states that optimizes the application of decellularized lung ECM materials to more closely mimic the human lung while conserving the compositional bioactivity of the native ECM. STATEMENT OF SIGNIFICANCE: The lack of an appropriate disease model for the study of chronic lung diseases continues to severely inhibit the advancement of treatments and preventions of these otherwise fatal illnesses due to the inability to recapture the biocomplexity of pathologic cell-ECM interactions. Engineering biomaterials that utilize decellularized lungs offers an opportunity to deconstruct, understand, and rebuild models that highlight and investigate how disease specific characteristics of the extracellular environment are involved in driving disease progression. We have advanced this space by designing a binary fabrication system for a ECM Hybridgel that retains properties from its source material required to observe native matrix interactions. This design simulates a 3D lung environment that is both mechanically elastic and compositionally relevant when derived from non-diseased tissue and pathologically diminished both mechanically and compositionally when derived from COPD tissue. Here we describe the ECM hybridgel as a model for the study of cell-ECM interactions involved in COPD.

Optimization strategies for mesenchymal stem cell-based analgesia therapy: a promising therapy for pain management

Pain is a very common and complex medical problem that has a serious impact on individuals' physical and mental health as well as society. Non-steroidal anti-inflammatory drugs and opioids are currently the main drugs used for pain management, but they are not effective in controlling all types of pain, and their long-term use can cause adverse effects that significantly impair patients' quality of life. Mesenchymal stem cells (MSCs) have shown great potential in pain treatment. However, limitations such as the low proliferation rate of MSCs in vitro and low survival rate in vivo restrict their analgesic efficacy and clinical translation. In recent years, researchers have explored various innovative approaches to improve the therapeutic effectiveness of MSCs in pain treatment. This article reviews the latest research progress of MSCs in pain treatment, with a focus on methods to enhance the analgesic efficacy of MSCs, including engineering strategies to optimize the in vitro culture environment of MSCs and to improve the in vivo delivery efficiency of MSCs. We also discuss the unresolved issues to be explored in future MSCs and pain research and the challenges faced by the clinical translation of MSC therapy, aiming to promote the optimization and clinical translation of MSC-based analgesia therapy.

Evaluation of the effects of decellularized extracellular matrix nanoparticles incorporation on the polyhydroxybutyrate/nano chitosan electrospun scaffold for cartilage tissue engineering

Recent research focuses on fabricating scaffolds imitating the extracellular matrix (ECM) in texture, composition, and functionality. Moreover, specific nano-bio-particles can enhance cell differentiation. Decellularized ECM nanoparticles possess all of the mentioned properties. In this research, cartilage ECM, extracted from the cow's femur condyle, was decellularized, and ECM nanoparticles were synthesized. Finally, nanocomposite electrospun fibers containing polyhydroxybutyrate (PHB), chitosan (Cs) nanoparticles, and ECM nanoparticles were fabricated and characterized. TEM and DLS results revealed ECM nanoparticle sizes of 17.51 and 21.6 nm, respectively. Optimal performance was observed in the scaffold with 0.75 wt% ECM nanoparticles (PHB-Cs/0.75E). By adding 0.75 wt% ECM, the ultimate tensile strength and elongation at break increased by about 29 % and 21 %, respectively, while the water contact angle and crystallinity decreased by about 36° and 2 %, respectively. Uneven and rougher surfaces of the PHB-Cs/0.75E were determined by FESEM and AFM images, respectively. TEM images verified the uniform dispersion of nanoparticles within the fibers. After 70 days of degradation in PBS, the PHB-Cs/0.75E and PHB-Cs scaffolds demonstrated insignificant weight loss differences. Eventually, enhanced viability, attachment, and proliferation of the human costal chondrocytes on the PHB-Cs/0.75E scaffold, concluded from MTT, SEM, and DAPI staining, confirmed its potential for cartilage tissue engineering.

Hydrogels in Gene Delivery Techniques for Regenerative Medicine and Tissue Engineering

Hydrogels are 3D networks swollen with water. They are biocompatible, strong, and moldable and are emerging as a promising biomedical material for regenerative medicine and tissue engineering to deliver therapeutic genes. The excellent natural extracellular matrix simulation properties of hydrogels enable them to be co-cultured with cells or enhance the expression of viral or non-viral vectors. Its biocompatibility, high strength, and degradation performance also make the action process of carriers in tissues more ideal, making it an ideal biomedical material. It has been shown that hydrogel-based gene delivery technologies have the potential to play therapy-relevant roles in organs such as bone, cartilage, nerve, skin, reproductive organs, and liver in animal experiments and preclinical trials. This paper reviews recent articles on hydrogels in gene delivery and explains the manufacture, applications, developmental timeline, limitations, and future directions of hydrogel-based gene delivery techniques.

Periapical lesion-derived decellularized extracellular matrix as a potential solution for regenerative endodontics

Pulp regeneration remains a crucial target in the preservation of natural dentition. Using decellularized extracellular matrix is an appropriate approach to mimic natural microenvironment and facilitate tissue regeneration. In this study, we attempted to obtain decellularized extracellular matrix from periapical lesion (PL-dECM) and evaluate its bioactive effects. The decellularization process yielded translucent and viscous PL-dECM, meeting the standard requirements for decellularization efficiency. Proteomic sequencing revealed that the PL-dECM retained essential extracellular matrix components and numerous bioactive factors. The PL-dECM conditioned medium could enhance the proliferation and migration ability of periapical lesion-derived stem cells (PLDSCs) in a dose-dependent manner. Culturing PLDSCs on PL-dECM slices improved odontogenic/angiogenic ability compared to the type I collagen group. In vivo, the PL-dECM demonstrated a sustained supportive effect on PLDSCs and promoted odontogenic/angiogenic differentiation. Both in vitro and in vivo studies illustrated that PL-dECM served as an effective scaffold for pulp tissue engineering, providing valuable insights into PLDSCs differentiation. These findings pave avenues for the clinical application of dECM's in situ transplantation for regenerative endodontics.

Transplantation of a bioengineered tissue patch promotes uterine repair in the sheep

Innovative bioengineering strategies utilizing extracellular matrix (ECM) based scaffolds derived from decellularized tissue offer new prospects for restoring damaged uterine tissue. Despite successful fertility restoration in small animal models, the translation to larger and more clinically relevant models have not yet been assessed. Thus, our study investigated the feasibility to use a 6 cm2 graft constructed from decellularized sheep uterine tissue, mimicking a future application to repair a uterine defect in women. Some grafts were also recellularized with fetal sheep bone marrow-derived mesenchymal stem cells (SF-MSCs). The animals were followed for six weeks post-surgery during which blood samples were collected to assess the systemic immune cell activation by fluorescence-activated cell sorting (FACS) analysis. Tissue regeneration was assessed by histology, immunohistochemistry, and gene expression analyses. There was a large intra-group variance which prompted us to implement a novel scoring system to comprehensively evaluate the regenerative outcomes. Based on the regenerative score each graft received, we focused our analysis to map potential differences that may have played a role in the success or failure of tissue repair following the transplantation therapy. Notably, three out of 15 grafts exhibited major regeneration that resembled native uterine tissue, and an additional three grafts showed substantial regenerative outcomes. For the better regenerated grafts, it was observed that the systemic T-cell subgroups were significantly different compared with the failing grafts. Hence, our data suggest that the T-cell response play an important role for determining the uterus tissue regeneration outcomes. The remarkable regeneration seen in the best-performing grafts after just six weeks following transplantation provides compelling evidence that decellularized tissue for uterine bioengineering holds great promise for clinically relevant applications.

Extracellular matrix-derived materials for tissue engineering and regenerative medicine: A journey from isolation to characterization and application

Biomaterial choice is an essential step during the development tissue engineering and regenerative medicine (TERM) applications. The selected biomaterial must present properties allowing the physiological-like recapitulation of several processes that lead to the reestablishment of homeostatic tissue or organ function. Biomaterials derived from the extracellular matrix (ECM) present many such properties and their use in the field has been steadily increasing. Considering this growing importance, it becomes imperative to provide a comprehensive overview of ECM biomaterials, encompassing their sourcing, processing, and integration into TERM applications. This review compiles the main strategies used to isolate and process ECM-derived biomaterials as well as different techniques used for its characterization, namely biochemical and chemical, physical, morphological, and biological. Lastly, some of their applications in the TERM field are explored and discussed.

Acellular carotid scaffold and evaluation the biological and biomechanical properties for tissue engineering

Introduction

The issues associated with the limitation of appropriate autologous vessels for vascular reconstruction via bypass surgery highlight the need for new alternative strategies based on tissue engineering. The present study aimed to prepare decellularized scaffolds from ovine carotid using chemical decellularization method.

Methods

Ovine carotid were decellularized with Triton X-100 and tri-n-butyl phosphate (TnBP) at 37 °C. Histological analysis, biochemical tests, biomechanical assay and biocompatibility assay were used to investigate the efficacy of decellularization.

Results

Decellularization method could successfully decellularize ovine carotid without leaving any cell remnants. Scaffolds showed minimal destruction of the three-dimensional structure and extracellular matrix, as well as adequate mechanical resistance and biocompatibility for cell growth and proliferation.

Conclusion

Prepared acellular scaffold exhibited the necessary characteristics for clinical applications.

Applications of selected polysaccharides and proteins in dentistry: A review

In the last ten years, remarkable characteristics and a variety of functionalities have been created in biopolymeric materials for clinical dental applications. This review gives an overview of current knowledge of natural biopolymers (biological macromolecules) in terms of structural, functional, and property interactions. Natural biopolymers such as polysaccharides (chitosan, bacterial cellulose, hyaluronic acid, and alginate) and polypeptides (collagen and silk fibroin) have been discussed for dental uses. These biopolymers exhibit excellent properties alone and when employed with other composite molecules making them ideal for treatment of periodontitis, endodontics, dental pulp regeneration and oral wound healing. These biopolymers together with the composite materials exhibit better biocompatibility, inertness, elasticity and flexibility which makes them a leading candidate to be used for other dental applications like caries management, oral appliances, dentures, dental implants and oral surgeries.

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 .

Advances focusing on the application of decellularization methods in tendon-bone healing

BACKGROUND

The tendon or ligament is attached to the bone by a triphasic but continuous area of heterogeneous tissue called the tendon-bone interface (TBI). The rapid and functional regeneration of TBI is challenging owing to its complex composition and difficulty in self-healing. The development of new technologies, such as decellularization, has shown promise in the regeneration of TBI. Several ex vivo and in vivo studies have shown that decellularized grafts and decellularized biomaterial scaffolds achieved better efficacy in enhancing TBI healing. However further information on the type of review that is available is needed.

AIM OF THE REVIEW

In this review, we discuss the current application of decellularization biomaterials in promoting TBI healing and the possible mechanisms involved. With this work, we would like to reveal how tissues or biomaterials that have been decellularized can improve tendon-bone healing and to provide a theoretical basis for future related studies.

KEY SCIENTIFIC CONCEPTS OF THE REVIEW

Decellularization is an emerging technology that utilizes various chemical, enzymatic and/or physical strategies to remove cellular components from tissues while retaining the structure and composition of the extracellular matrix (ECM). After decellularization, the cellular components of the tissue that cause an immune response are removed, while various biologically active biofactors are retained. This review further explores how tissues or biomaterials that have been decellularized improve TBI healing.

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

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

The potential role of mechanotransduction in the management of pediatric calvarial bone flap repair

Pediatric patients suffering traumatic brain injuries may require a decompressive craniectomy to accommodate brain swelling by removing a portion of the skull. Once the brain swelling subsides, the preserved calvarial bone flap is ideally replaced as an autograft during a cranioplasty to restore protection of the brain, as it can reintegrate and grow with the patient during immature skeletal development. However, pediatric patients exhibit a high prevalence of calvarial bone flap resorption post-cranioplasty, causing functional and cosmetic morbidity. This review examines possible solutions for mitigating pediatric calvarial bone flap resorption by delineating methods of stimulating mechanosensitive cell populations with mechanical forces. Mechanotransduction plays a critical role in three main cell types involved with calvarial bone repair, including mesenchymal stem cells, osteoblasts, and dural cells, through mechanisms that could be exploited to promote osteogenesis. In particular, physiologically relevant mechanical forces, including substrate deformation, external forces, and ultrasound, can be used as tools to stimulate bone repair in both in vitro and in vivo systems. Ultimately, combating pediatric calvarial flap resorption may require a combinatorial approach using both cell therapy and bioengineering strategies.

A Library of Elastin-like Proteins with Tunable Matrix Ligands for In Vitro 3D Neural Cell Culture

Hydrogels with encapsulated cells have widespread biomedical applications, both as tissue-mimetic 3D cultures in vitro and as tissue-engineered therapies in vivo. Within these hydrogels, the presentation of cell-instructive extracellular matrix (ECM)-derived ligands and matrix stiffness are critical factors known to influence numerous cell behaviors. While individual ECM biopolymers can be blended together to alter the presentation of cell-instructive ligands, this typically results in hydrogels with a range of mechanical properties. Synthetic systems that allow for the facile incorporation and modulation of multiple ligands without modification of matrix mechanics are highly desirable. In the present work, we leverage protein engineering to design a family of xeno-free hydrogels (i.e., devoid of animal-derived components) consisting of recombinant hyaluronan and recombinant elastin-like proteins (ELPs), cross-linked together with dynamic covalent bonds. The ELP components incorporate cell-instructive peptide ligands derived from ECM proteins, including fibronectin (RGD), laminin (IKVAV and YIGSR), collagen (DGEA), and tenascin-C (PLAEIDGIELTY and VFDNFVL). By carefully designing the protein primary sequence, we form 3D hydrogels with defined and tunable concentrations of cell-instructive ligands that have similar matrix mechanics. Utilizing this system, we demonstrate that neurite outgrowth from encapsulated embryonic dorsal root ganglion (DRG) cultures is significantly modified by cell-instructive ligand content. Thus, this library of protein-engineered hydrogels is a cell-compatible system to systematically study cell responses to matrix-derived ligands.

Recent Progress of In Vitro 3D Culture of Male Germ Stem Cells

Male germline stem cells (mGSCs), also known as spermatogonial stem cells (SSCs), are the fundamental seed cells of male animal reproductive physiology. However, environmental influences, drugs, and harmful substances often pose challenges to SSCs, such as population reduction and quality decline. With advancements in bioengineering technology and biomaterial technology, an increasing number of novel cell culture methods and techniques have been employed for studying the proliferation and differentiation of SSCs in vitro. This paper provides a review on recent progress in 3D culture techniques for SSCs in vitro; we summarize the microenvironment of SSCs and spermatocyte development, with a focus on scaffold-based culture methods and 3D printing cell culture techniques for SSCs. Additionally, decellularized testicular matrix (DTM) and other biological substrates are utilized through various combinations and approaches to construct an in vitro culture microenvironment suitable for SSC growth. Finally, we present some perspectives on current research trends and potential opportunities within three areas: the 3D printing niche environment, alternative options to DTM utilization, and advancement of the in vitro SSC culture technology system.

Decellularization Techniques for Tissue Engineering: Towards Replicating Native Extracellular Matrix Architecture in Liver Regeneration

The process of tissue regeneration requires the utilization of a scaffold, which serves as a structural framework facilitating cellular adhesion, proliferation, and migration within a physical environment. The primary aim of scaffolds in tissue engineering is to mimic the structural and functional properties of the extracellular matrix (ECM) in the target tissue. The construction of scaffolds that accurately mimic the architecture of the extracellular matrix (ECM) is a challenging task, primarily due to the intricate structural nature and complex composition of the ECM. The technique of decellularization has gained significant attention in the field of tissue regeneration because of its ability to produce natural scaffolds by removing cellular and genetic components from the extracellular matrix (ECM) while preserving its structural integrity. The present study aims to investigate the various decellularization techniques employed for the purpose of isolating the extracellular matrix (ECM) from its native tissue. Additionally, a comprehensive comparison of these methods will be presented, highlighting their respective advantages and disadvantages. The primary objective of this study is to gain a comprehensive understanding of the anatomical and functional features of the native liver, as well as the prevalence and impact of liver diseases. Additionally, this study aims to identify the limitations and difficulties associated with existing therapeutic methods for liver diseases. Furthermore, the study explores the potential of tissue engineering techniques in addressing these challenges and enhancing liver performance. By investigating these aspects, this research field aims to contribute to the advancement of liver disease treatment and management.

Extracellular matrix-induced signaling pathways in mesenchymal stem/stromal cells

The extracellular matrix (ECM) is a crucial component of the stem cell microenvironment, or stem-cell niches, and contributes to the regulation of cell behavior and fate. Accumulating evidence indicates that different types of stem cells possess a large variety of molecules responsible for interactions with the ECM, mediating specific epigenetic rearrangements and corresponding changes in transcriptome profile. Signals from the ECM are crucial at all stages of ontogenesis, including embryonic and postnatal development, as well as tissue renewal and repair. The ECM could regulate stem cell transition from a quiescent state to readiness to perceive the signals of differentiation induction (competence) and the transition between different stages of differentiation (commitment). Currently, to unveil the complex networks of cellular signaling from the ECM, multiple approaches including screening methods, the analysis of the cell matrixome, and the creation of predictive networks of protein-protein interactions based on experimental data are used. In this review, we consider the existing evidence regarded the contribution of ECM-induced intracellular signaling pathways into the regulation of stem cell differentiation focusing on mesenchymal stem/stromal cells (MSCs) as well-studied type of postnatal stem cells totally depended on signals from ECM. Furthermore, we propose a system biology-based approach for the prediction of ECM-mediated signal transduction pathways in target cells. Video Abstract.

Generation of Haploid Spermatids on Silk Fibroin-Alginate-Laminin-Based Porous 3D Scaffolds

In vitro production of sperm is a desirable idea for fertility preservation in azoospermic men and prepubertal boys suffering from cancer. In this study, a biocompatible porous scaffold based on a triad mixture of silk fibroin (SF), alginate (Alg), and laminin (LM) is developed to facilitate the differentiation of mouse spermatogonia stem cells (SSCs). Following SF extraction, the content is analyzed by SDS-PAGE and stable porous 3D scaffolds are successfully prepared by merely Alg, SF, and a combination of Alg-SF, or Alg-SF-LM through freeze-drying. Then, the biomimetic scaffolds are characterized regarding the structural and biological properties, water absorption capacity, biocompatibility, biodegradability, and mechanical behavior. Neonatal mice testicular cells are seeded on three-dimensional scaffolds and their differentiation efficiency is evaluated using real-time PCR, flow cytometry, immunohistochemistry. Blend matrices showed uniform porous microstructures with interconnected networks, which maintained long-term stability and mechanical properties better than homogenous structures. Molecular analysis of the cells after 21 days of culture showed that the expression of differentiation-related proteins in cells that are developed in composite scaffolds is significantly higher than in other groups. The application of a composite system can lead to the differentiation of SSCs, paving the way for a novel infertility treatment landscape in the future.

Human induced pluripotent stem cell-derived liver-on-a-chip for studying drug metabolism: the challenge of the cytochrome P450 family

The liver is the primary organ responsible for the detoxification and metabolism of drugs. To date, a lack of preclinical models that accurately emulate drug metabolism by the human liver presents a significant challenge in the drug development pipeline, particularly for predicting drug efficacy and toxicity. In recent years, emerging microfluidic-based organ-on-a-chip (OoC) technologies, combined with human induced pluripotent stem cell (hiPSC) technology, present a promising avenue for the complete recapitulation of human organ biology in a patient-specific manner. However, hiPSC-derived organoids and liver-on-a-chip models have so far failed to sufficiently express cytochrome P450 monooxygenase (CYP450) enzymes, the key enzymes involved in first-pass metabolism, which limits the effectiveness and translatability of these models in drug metabolism studies. This review explores the potential of innovative organoid and OoC technologies for studying drug metabolism and discusses their existing drawbacks, such as low expression of CYP450 genes. Finally, we postulate potential approaches for enhancing CYP450 expression in the hope of paving the way toward developing novel, fully representative liver drug-metabolism models.

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

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

Xeno-free culture and proliferation of hPSCs on 2D biomaterials

Human pluripotent stem cells (human embryonic stem cells (hESCs) and induced pluripotent stem cells (hiPSCs)) have unlimited proliferative potential, whereas adult stem cells such as bone marrow-derived stem cells and adipose-derived stem cells have problems with aging. When hPSCs are intended to be cultured on feeder-free or xeno-free conditions without utilizing mouse embryonic fibroblasts or human fibroblasts, they cannot be cultured on conventional tissue culture polystyrene dishes, as adult stem cells can be cultured but should be cultivated on material surfaces grafted or coated with (a) natural or recombinant extracellular matrix (ECM) proteins, (b) ECM protein-derived peptides and specific synthetic polymer surfaces in xeno-free and/or chemically defined conditions. This review describes current developing cell culture biomaterials for the proliferation of hPSCs while maintaining the pluripotency and differentiation potential of the cells into 3 germ layers. Biomaterials for the cultivation of hPSCs without utilizing a feeder layer are essential to decrease the risk of xenogenic molecules, which contributes to the potential clinical usage of hPSCs. ECM proteins such as human recombinant vitronectin, laminin-511 and laminin-521 have been utilized instead of Matrigel for the feeder-free cultivation of hPSCs. The following biomaterials are also discussed for hPSC cultivation: (a) decellularized ECM, (b) peptide-grafted biomaterials derived from ECM proteins, (c) recombinant E-cadherin-coated surface, (d) polysaccharide-immobilized surface, (e) synthetic polymer surfaces with and without bioactive sites, (f) thermoresponsive polymer surfaces with and without bioactive sites, and (g) synthetic microfibrous scaffolds.

Current Trends on Bioengineering Approaches for Ovarian Microenvironment Reconstruction

Ovarian tissue has a unique microarchitecture and a complex cellular and molecular dynamics that are essential for follicular survival and development. Due to this great complexity, several factors may lead to ovarian insufficiency, and therefore to systemic metabolic disorders and female infertility. Techniques currently used in the reproductive clinic such as oocyte cryopreservation or even ovarian tissue transplant, although effective, have several limitations, which impair their wide application. In this scenario, mimetic ovarian tissue reconstruction comes as an innovative alternative to develop new methodologies for germ cells preservation and ovarian functions restoration. The ovarian extracellular matrix (ECM) is crucial for oocyte viability maintenance, once it acts actively in folliculogenesis. One of the key components of ovarian bioengineering is biomaterials application that mimics ECM and provides conditions for cell anchorage, proliferation, and differentiation. Therefore, this review aims at describing ovarian tissue engineering approaches and listing the main limitations of current methods for preservation and reestablishment of ovarian fertility. In addition, we describe the main elements that structure this study field, highlighting the main advances and the challenges to overcome to develop innovative methodologies to be applied in reproductive medicine. Impact Statement This review presents the main advances in the application of tissue bioengineering in the ovarian tissue reconstruction to develop innovative solutions for ovarian fertility reestablishment.

Bioengineering liver tissue by repopulation of decellularised scaffolds

Liver transplantation is the only curative therapy for end stage liver disease, but is limited by the organ shortage, and is associated with the adverse consequences of immunosuppression. Repopulation of decellularised whole organ scaffolds with appropriate cells of recipient origin offers a theoretically attractive solution, allowing reliable and timely organ sourcing without the need for immunosuppression. Decellularisation methodologies vary widely but seek to address the conflicting objectives of removing the cellular component of tissues whilst keeping the 3D structure of the extra-cellular matrix intact, as well as retaining the instructive cell fate determining biochemicals contained therein. Liver scaffold recellularisation has progressed from small rodent in vitro studies to large animal in vivo perfusion models, using a wide range of cell types including primary cells, cell lines, foetal stem cells, and induced pluripotent stem cells. Within these models, a limited but measurable degree of physiologically significant hepatocyte function has been reported with demonstrable ammonia metabolism in vivo. Biliary repopulation and function have been restricted by challenges relating to the culture and propagations of cholangiocytes, though advances in organoid culture may help address this. Hepatic vasculature repopulation has enabled sustainable blood perfusion in vivo, but with cell types that would limit clinical applications, and which have not been shown to have the specific functions of liver sinusoidal endothelial cells. Minority cell groups such as Kupffer cells and stellate cells have not been repopulated. Bioengineering by repopulation of decellularised scaffolds has significantly progressed, but there remain significant experimental challenges to be addressed before therapeutic applications may be envisaged.

Degenerative tendon matrix induces tenogenic differentiation of mesenchymal stem cells

PURPOSE

Mesenchymal stem cells (MSCs) react dynamically with the surrounding microenvironment to promote tissue-specific differentiation and hence increase targeted regenerative capacity. Extracellular matrix (ECM) would be the first microenvironment to interact with MSCs injected into the tissue lesion. However, degenerative tissues would have different characteristics of ECM in comparison with healthy tissues. Therefore, the influence of degenerative ECM on tissue-specific differentiation of MSCs and the formation of matrix composition need to be considered for the sophisticated therapeutic application of stem cells for tissue regeneration.

METHODS

Human degenerative tendon tissues were obtained from patients undergoing rotator cuff repair and finely minced into 2 ~ 3 mm fragments. Different amounts of tendon matrix (0.005 g, 0.01 g, 0.025 g, 0.05 g, 0.1 g, 0.25 g, 0.5 g, 1 g, and 2 g) were co-cultured with bone marrow MSCs (BM MSCs) for 7 days. Six tendon-related markers, scleraxis, tenomodulin, collagen type I and III, decorin, and tenascin-C, osteogenic marker, alkaline phosphatase (ALP), and chondrogenic marker, aggrecan (ACAN), were analyzed by qRT-PCR. Cell viability and senescence-associated beta-galactosidase assays were performed. The connective tissue growth factor was used as a positive control.

RESULTS

The expressions of six tendon-related markers were significantly upregulated until the amount of tendon matrix exceeded 0.5 g, the point where the mRNA expressions of all six genes analyzed started to decrease. The tendon matrix exerted an inhibitory effect on ACAN expression but had a negligible effect on ALP expression. Cell viability did not change significantly over the culture period. The amount of tendon matrix exceeding 0.01 g significantly increased the SA-βgal activity of BM MSCs.

CONCLUSION

This study successfully demonstrated tendon ECM-stimulated tenogenesis of BM MSCs through an indirect co-culture system without the use of exogenous growth factors and the alteration of cellular viability. In contrast to the initial hypothesis, the tenogenesis of BM MSCs induced with the degenerative tendon matrix accompanied cellular senescence.

Highly Efficient Cardiac Differentiation and Maintenance by Thrombin-Coagulated Fibrin Hydrogels Enriched with Decellularized Porcine Heart Extracellular Matrix

Biochemical and biophysical properties instruct cardiac tissue morphogenesis. Here, we are reporting on a blend of cardiac decellularized extracellular matrix (dECM) from porcine ventricular tissue and fibrinogen that is suitable for investigations employing an in vitro 3D cardiac cell culture model. Rapid and specific coagulation with thrombin facilitates the gentle inclusion of cells while avoiding sedimentation during formation of the dECM-fibrin composite. Our investigations revealed enhanced cardiogenic differentiation in the H9c2 myoblast cells when using the system in a co-culture with Nor-10 fibroblasts. Further enhancement of differentiation efficiency was achieved by 3D embedding of rat neonatal cardiomyocytes in the 3D system. Calcium imaging and analysis of beating motion both indicate that the dECM-fibrin composite significantly enhances recovery, frequency, synchrony, and the maintenance of spontaneous beating, as compared to various controls including Matrigel, pure fibrin and collagen I as well as a fibrin-collagen I blend.

Novel fabrication of bioengineered injectable chitosan hydrogel loaded with conductive nanoparticles to improve therapeutic potential of mesenchymal stem cells in functional recovery after ischemic myocardial infarction

In recent decades, myocardial regeneration through stem cell transplantation and tissue engineering has been viewed as a promising technique for treating myocardial infarction. As a result, the researcher attempts to see whether co-culturing modified mesenchymal stem cells with Au@Ch-SF macro-hydrogel and H9C2 may help with tissue regeneration and cardiac function recovery. The gold nanoparticles (Au) incorporated into the chitosan-silk fibroin hydrogel (Au@Ch-SF) were validated using spectral and microscopic examinations. The most essential elements of hydrogel groups were investigated in detail, including weight loss, mechanical strength, and drug release rate. Initially, the cardioblast cells (H9C2 cells) was incubated with Au@Ch-SF macro-hydrogel, followed by mesenchymal stem cells (2 × 10⁵) were transplanted into the Au@Ch-SF macro-hydrogel+H9C2 culture at the ratio of 2:1. Further, cardiac phenotype development, cytokines expression and tissue regenerative performance of modified mesenchymal stem cells treatment were studied through various in vitro and in vivo analyses. The Au@Ch-SF macro-hydrogel gelation time was much faster than that of Ch and Ch-SF hydrogels, showing that Ch and SF exhibited greater intermolecular interactions. The obtained Au@Ch-SF macro-hydrogel has no toxicity on mesenchymal stem cells (MS) or cardiac myoblast (H9C2) cells, according to the biocompatibility investigation. MS cells co-cultured with Au@Ch-SF macro-hydrogel and H9C2 cells also stimulated cardiomyocyte fiber restoration, which has been confirmed in myocardial infarction rats using -MHC and Cx43 myocardial indicators. We developed a novel method of co-cultured therapy using MS cells, Au@Ch-SF macro-hydrogel, and H9C2 cells which could promote the regenerative activities in myocardial ischemia cells. These study findings show that co-cultured MS therapy might be effective for the treatment of myocardial injury.

Decellularized tympanic membrane scaffold with bone marrow mesenchymal stem cells for repairing tympanic membrane perforation

BACKGROUND

Tympanic membrane perforation (TMP) is a common disease in otology, and few acellular techniques have been reported for repairing this condition. Decellularized extracellular matrix (ECM) scaffolds have been used in organ reconstruction.

OBJECTIVE

This study on tissue engineering aimed to develop a tympanic membrane (TM) scaffold prepared using detergent immersion and bone marrow mesenchymal stem cells (BMSCs) as repair materials to reconstruct the TM.

RESULTS

General structure was observed that the decellularized TM scaffold with BMSCs retained the original intact anatomical ECM structure, with no cell residue, as observed using scanning electron microscopy (SEM), and exhibited low immunogenicity. Therefore, we seeded the decellularized TM scaffold with BMSCs for recellularization. Histology and eosin staining, SEM and immunofluorescence in vivo showed that the recellularized TM patch had a natural ultrastructure and was suitable for the migration and proliferation of BMSCs. The auditory brainstem response (ABR) evaluated after recellularized TM patch repair was slightly higher than that of the normal TM, but the difference was not significant.

CONCLUSION

The synthetic ECM scaffold provides temporary physical support for the three-dimensional growth of cells during the tissue developmental stage. The scaffold stimulates cells to secrete their own ECM required for tissue regeneration. The recellularized TM patch shows potential as a natural, ultrastructure biological material for TM reconstruction.

Neural progenitor cell-derived extracellular matrix as a new platform for neural differentiation of human induced pluripotent stem cells

The culture microenvironment has been demonstrated to regulate stem cell fate and to be a crucial aspect for quality-controlled stem cell maintenance and differentiation to a specific lineage. In this context, extracellular matrix (ECM) proteins are particularly important to mediate the interactions between the cells and the culture substrate. Human induced pluripotent stem cells (hiPSCs) are usually cultured as anchorage-dependent cells and require adhesion to an ECM substrate to support their survival and proliferation in vitro. Matrigel, a common substrate for hiPSC culture is a complex and undefined mixture of ECM proteins which are expensive and not well suited to clinical application. Decellularized cell-derived ECM has been shown to be a promising alternative to the common protein coatings used in stem cell culture. However, very few studies have used this approach as a niche for neural differentiation of hiPSCs. Here, we developed a new stem cell culture system based on decellularized cell-derived ECM from neural progenitor cells (NPCs) for expansion and neural differentiation of hiPSCs, as an alternative to Matrigel and poly-l-ornithine/laminin-coated well plates. Interestingly, hiPSCs were able to grow and maintain their pluripotency when cultured on decellularized ECM from NPCs (NPC ECM). Furthermore, NPC ECM enhanced the neural differentiation of hiPSCs compared to poly-l-ornithine/laminin-coated wells, which are used in most neural differentiation protocols, presenting a statistically significant enhancement of neural gene expression markers, such as βIII-Tubulin and MAP2. Taken together, our results demonstrate that NPC ECM provides a functional microenvironment, mimicking the neural niche, which may have interesting future applications for the development of new strategies in neural stem cell research.

Intravital microscopy datasets examining key nephron segments of transplanted decellularized kidneys

This study contains intravital microscopy (IVM) data examining the microarchitecture of acellular kidney scaffolds. Acellular scaffolds are cell-free collagen-based matrices derived from native organs that can be used as templates for regenerative medicine applications. This data set contains in vivo assays that evaluate the effectiveness of decellularization and how these acellular nephron compartments perform in the post-transplantation environment. Qualitative and quantitative assessments of scaffold DNA concentrations, tissue fluorescence signals, and structural and functional integrities of decellularized tubular and peritubular capillary segments were acquired and compared to the native (non-transplanted) organ. Cohorts of 2–3-month-old male Sprague Dawley rats were used: non-transplanted (n = 4), transplanted day 0 (n = 4), transplanted day 1 (n = 4), transplanted day 2 (n = 4), and transplanted day 7 (n = 4). Micrographs and supporting measurements are provided to illustrate IVM processes used to perform this study and are publicly available in a data repository to assist scientific reproducibility and extend the use of this powerful imaging application to analyze other scaffold systems. Measurements(s) DNA quantification • tissue fluorescence • microvascular leakage • tubular and peritubular capillary integrity Technology Type(s) intravital microscopy • multiphoton microscopy • UV-visible spectroscopy Sample Characterization(s) rats • native and decellularized kidneys

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.

How the Nonwoven Polymer Volume Microstructure Is Transformed under Tension in an Aqueous Environment

The fibrous porous structure of polymers can mimic the extracellular matrix of the native tissue, therefore such polymers have a good potential for use in regenerative medicine. Organs and tissues within the body exhibit different mechanical properties depending on their functionality, thus artificial scaffolds should have mechanical behaviors similar to the extracellular matrix in conditions like living organisms, primarily in aqueous media. Several methods have been investigated in aquatic environments, including noninvasive techniques based on ultrasonic focused beams for biological objectives. In this study we explored the tensile behavior of poly(L-lactide) nonwoven polymer scaffolds using high-frequency ultrasound microscopy combined with a horizontal testing machine, which provided a visualization of the reorganization and transformation of the dynamic volume microstructure. The mechanisms of unwinding, elongation, orientation, and deformation of polymer fibers under uniaxial tension were revealed. We observed an association between the lined plastic deformation from 100 to 400% and the formation of multiple necks in the fibers, which caused stress relaxation and significant rarefaction of the fibrous microstructure. It was shown that both peaks on the stress–strain curve corresponded to the microstructure of aligned fibers in terms of initial diameter and thinning fibers. We discuss the possible influence of these microstructure transformations on cell behavior.

Extraction and Biological Evaluation of Matrix-Bound Nanovesicles (MBVs) from High-Hydrostatic Pressure-Decellularized Tissues

Decellularized tissues are widely used as promising materials in tissue engineering and regenerative medicine. Research on the microstructure and components of the extracellular matrix (ECM) was conducted to improve the current understanding of decellularized tissue functionality. The presence of matrix-bound nanovesicles (MBVs) embedded within the ECM was recently reported. Results of a previous experimental investigation revealed that decellularized tissues prepared using high hydrostatic pressure (HHP) exhibited good in vivo performance. In the current study, according to the hypothesis that MBVs are one of the functional components in HHP-decellularized tissue, we investigated the extraction of MBVs and the associated effects on vascular endothelial cells. Using nanoparticle tracking assay (NTA), transmission electron microscopy (TEM), and RNA analysis, nanosized (100–300 nm) and membranous particles containing small RNA were detected in MBVs derived from HHP-decellularized small intestinal submucosa (SIS), urinary bladder matrix (UBM), and liver. To evaluate the effect on the growth of vascular endothelial cells, which are important in the tissue regeneration process, isolated SIS-derived MBVs were exposed to vascular endothelial cells to induce cell proliferation. These results indicate that MBVs can be extracted from HHP-decellularized tissues and may play a significant role in tissue remodeling.

Tissue Engineering Approaches to Uncover Therapeutic Targets for Endothelial Dysfunction in Pathological Microenvironments

Endothelial cell dysfunction plays a central role in many pathologies, rendering it crucial to understand the underlying mechanism for potential therapeutics. Tissue engineering offers opportunities for in vitro studies of endothelial dysfunction in pathological mimicry environments. Here, we begin by analyzing hydrogel biomaterials as a platform for understanding the roles of the extracellular matrix and hypoxia in vascular formation. We next examine how three-dimensional bioprinting has been applied to recapitulate healthy and diseased tissue constructs in a highly controllable and patient-specific manner. Similarly, studies have utilized organs-on-a-chip technology to understand endothelial dysfunction's contribution to pathologies in tissue-specific cellular components under well-controlled physicochemical cues. Finally, we consider studies using the in vitro construction of multicellular blood vessels, termed tissue-engineered blood vessels, and the spontaneous assembly of microvascular networks in organoids to delineate pathological endothelial dysfunction.

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

Human-Origin iPSC-Based Recellularization of Decellularized Whole Rat Livers

End-stage liver diseases lead to mortality of millions of patients, as the only treatment available is liver transplantation and donor scarcity means that patients have to wait long periods before receiving a new liver. In order to minimize donor organ scarcity, a promising bioengineering approach is to decellularize livers that do not qualify for transplantation. Through decellularization, these organs can be used as scaffolds for developing new functional organs. In this process, the original cells of the organ are removed and ideally should be replaced by patient-specific cells to eliminate the risk of immune rejection. Induced pluripotent stem cells (iPSCs) are ideal candidates for developing patient-specific organs, yet the maturity and functionality of iPSC-derived cells do not match those of primary cells. In this study, we introduced iPSCs into decellularized rat liver scaffolds prior to the start of differentiation into hepatic lineages to maximize the exposure of iPSCs to native liver matrices. Through exposure to the unique composition and native 3D organization of the liver microenvironment, as well as the more efficient perfusion culture throughout the differentiation process, iPSC differentiation into hepatocyte-like cells was enhanced. The resulting cells showed significantly higher expression of mature hepatocyte markers, including important CYP450 enzymes, along with lower expression of fetal markers, such as AFP. Importantly, the gene expression profile throughout the different stages of differentiation was more similar to native development. Our study shows that the native 3D liver microenvironment has a pivotal role to play in the development of human-origin hepatocyte-like cells with more mature characteristics.

Supramolecular Biomaterials in the Netherlands

Synthetically designed biomaterials strive to recapitulate and mimic the complex environment of natural systems. Using natural materials as a guide, the ability to create high performance biomaterials that control cell fate, and support the next generation of cell and tissue-based therapeutics, is starting to emerge. Supramolecular chemistry takes inspiration from the wealth of non-covalent interactions found in natural materials that are inherently complex, and using the skills of synthetic and polymer chemistry, recreates simple systems to imitate their features. Within the past decade, supramolecular biomaterials have shown utility in tissue engineering and the progress predicts a bright future. On this 30th anniversary of the Netherlands Biomaterials and Tissue Engineering society, we will briefly recount the state of supramolecular biomaterials in the Dutch academic and industrial research and development context. This review will provide the background, recent advances, industrial successes and challenges, as well as future directions of the field, as we see it. Throughout this work, we notice the intricate interplay between simplicity and complexity in creating more advanced solutions. We hope that the interplay and juxtaposition between these two forces can propel the field forward.

Induction of Corneal Epithelial Differentiation of Induced Pluripotent and Orbital Fat-Derived Stem Cells Seeded on Decellularized Human Corneas

Up to 40% of donor corneas are deemed unsuitable for transplantation, aggravating the shortage of graft tissue. In most cases, the corneal extracellular matrix is intact. Therefore, their decellularization followed by repopulation with autologous cells may constitute an efficient alternative to reduce the amount of discarded tissue and the risk of immune rejection after transplantation. Although induced pluripotent (hiPSCs) and orbital fat-derived stem cells (OFSCs) hold great promise for corneal epithelial (CE) reconstruction, no study to date has evaluated the capacity of decellularized corneas (DCs) to support the attachment and differentiation of these cells into CE-like cells. Here, we recellularize DCs with hiPSCs and OFSCs and evaluate their differentiation potential into CE-like cells using animal serum-free culture conditions. Cell viability and adhesion on DCs were assessed by calcein-AM staining and scanning electron microscopy. Cell differentiation was evaluated by RT-qPCR and immunofluorescence analyses. DCs successfully supported the adhesion and survival of hiPSCs and OFSCs. The OFSCs cultured under differentiation conditions could not express the CE markers, TP63, KRT3, PAX6, and KRT12, while the hiPSCs gave rise to cells expressing high levels of these markers. RT-qPCR data suggested that the DCs provided an inductive environment for CE differentiation of hiPSCs, supporting the expression of PAX6 and KRT12 without the need for any soluble induction factors. Our results open the avenue for future studies regarding the in vivo effects of DCs as carriers for autologous cell transplantation for ocular surface reconstruction.

Fully Synthetic 3D Fibrous Scaffolds for Stromal Tissues-Replacement of Animal-Derived Scaffold Materials Demonstrated by Multilayered Skin

The extracellular matrix (ECM) of soft tissues in vivo has remarkable biological and structural properties. Thereby, the ECM provides mechanical stability while it still can be rearranged via cellular remodeling during tissue maturation or healing processes. However, modern synthetic alternatives fail to provide these key features among basic properties. Synthetic matrices are usually completely degraded or are inert regarding cellular remodeling. Based on a refined electrospinning process, a method is developed to generate synthetic scaffolds with highly porous fibrous structures and enhanced fiber-to-fiber distances. Since this approach allows for cell migration, matrix remodeling, and ECM synthesis, the scaffold provides an ideal platform for the generation of soft tissue equivalents. Using this matrix, an electrospun-based multilayered skin equivalent composed of a stratified epidermis, a dermal compartment, and a subcutis is able to be generated without the use of animal matrix components. The extension of classical dense electrospun scaffolds with high porosities and motile fibers generates a fully synthetic and defined alternative to collagen-gel-based tissue models and is a promising system for the construction of tissue equivalents as in vitro models or in vivo implants.

New paradigms in regenerative engineering: Emerging role of extracellular vesicles paired with instructive biomaterials

Mesenchymal stem cells (MSCs) have long been regarded as critical components of regenerative medicine strategies, given their multipotency and persistence in a variety of tissues. Recently, the specific role of MSCs in mediating regenerative outcomes has been attributed (in part) to secreted factors from transplanted cells, namely extracellular vesicles. This viewpoint manuscript highlights the promise of cell-derived extracellular vesicles as agents of regeneration, enhanced by synergy with appropriate biomaterials platforms. Extracellular vesicles are a potentially interesting regenerative tool to enhance the synergy between MSCs and biomaterials. As a result, we believe these technologies will improve patient outcomes through efficient therapeutic strategies resulting in predictable patient outcomes.

Expanding the Repertoire of Electrospinning: New and Emerging Biopolymers, Techniques, and Applications

Electrospinning has emerged as a versatile and accessible technology for fabricating polymer fibers, particularly for biological applications. Natural polymers or biopolymers (including synthetically derivatized natural polymers) represent a promising alternative to synthetic polymers, as materials for electrospinning. Many biopolymers are obtained from abundant renewable sources, are biodegradable, and possess inherent biological functions. This review surveys recent literature reporting new fibers produced from emerging biopolymers, highlighting recent developments in the use of sulfated polymers (including carrageenans and glycosaminoglycans), tannin derivatives (condensed and hydrolyzed tannins, tannic acid), modified collagen, and extracellular matrix extracts. The proposed advantages of these biopolymer-based fibers, focusing on their biomedical applications, are also discussed to highlight the use of new and emerging biopolymers (or new modifications to well-established ones) to enhance or achieve new properties for electrospun fiber materials.

Nerve Decellularized Matrix Composite Scaffold With High Antibacterial Activity for Nerve Regeneration

Nerve decellularized matrix (NDM) has received much attention due to its natural composition and structural advantages that had proven to be an excellent candidate for peripheral nerve regeneration. However, NDM with simultaneous biocompatibility, promoting nerve regeneration, as well as resistant to infection was rarely reporter. In this study, a porous NDM-CS scaffold with high antimicrobial activity and high biocompatibility was prepared by combining the advantages of both NDM and chitosan (CS) in a one-step method. The NDM-CS scaffold possessed high porosity and hydrophilicity, exhibited excellent biocompatibility which was suitable for cell growth and nutrient exchange. Meanwhile, NDM-CS scaffold had a significant antibacterial effect on both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), which could avoid wound infection during the repair process. In addition, the NDM-CS scaffold could support the growth and viability of Schwann cells effectively. Among them, the E2C1 group had the strongest ability to enhance proliferation, polarization and migration of Schwann cells among the three groups. The positive effect on Schwann cells indicated their ability in the process of nerve injury repair. Therefore, this NDM-CS scaffold may have potential prospects for application in neural tissue engineering.

Formation of organoid-like structures in the decellularized rat testis

Objectives

In testis, the extracellular matrix (ECM) in addition to the supportive role for cells in the seminiferous epithelium, is also essential for the accurate functioning of these cells. Thus, using a decellularized testicular ECM (DTECM), as a scaffold for three-dimensional (3D) culture of testicular cells can mimic native ECM for studying in vitro spermatogenesis.

Materials and Methods

The rat testis was decellularized via perfusion of 0.5% sodium dodecyl sulfate (SDS) for 48 hr, followed by 1% Triton X-100 for 6 hr, and then 1% DNase I for 1 hr. The efficiency of decellularization was evaluated by histology, immunohistochemistry (IHC), scanning electron microscopy (SEM), and MTT test. The prepared scaffolds were recellularized with testicular cells and cultured and assessed with hematoxylin-eosin (H&E) staining after two weeks.

Results

Based on the H&E image, no trace of cell components could be observed in DTECM. IHC images demonstrated collagen types I and IV, laminin, and fibronectin were preserved. Masson's trichrome and alcian blue staining revealed that collagen and glycosaminoglycans (GAGs) were retained, and the SEM image indicated that 3D testicular architecture remained after the decellularization process. Based on the results of the MTT test, DTECM was cytocompatible, and H&E images represented that DTECM supports testicular cell arrangements in seminiferous tubule-like structures (STLSs) and organoid-like structures (OLSs).

Conclusion

The results showed that the applied protocol successfully decellularized the testis tissue of the rat. Therefore, these scaffolds may provide an appropriate vehicle for in vitro reconstruction of the seminiferous tubule.

Advancing models of neural development with biomaterials

Human pluripotent stem cells have emerged as a promising in vitro model system for studying the brain. Two-dimensional and three-dimensional cell culture paradigms have provided valuable insights into the pathogenesis of neuropsychiatric disorders, but they remain limited in their capacity to model certain features of human neural development. Specifically, current models do not efficiently incorporate extracellular matrix-derived biochemical and biophysical cues, facilitate multicellular spatio-temporal patterning, or achieve advanced functional maturation. Engineered biomaterials have the capacity to create increasingly biomimetic neural microenvironments, yet further refinement is needed before these approaches are widely implemented. This Review therefore highlights how continued progression and increased integration of engineered biomaterials may be well poised to address intractable challenges in recapitulating human neural development.

Injectable hydrogels for vascular embolization and cell delivery: The potential for advances in cerebral aneurysm treatment

Cerebral aneurysms are vascular lesions caused by the biomechanical failure of the vessel wall due to hemodynamic stress and inflammation. Aneurysmal rupture results in subarachnoid hemorrhage often leading to death or disability. Current treatment options include open surgery and minimally invasive endovascular options aimed at secluding the aneurysm from the circulation. Cerebral aneurysm embolization with appropriate materials is a therapeutic approach to prevent rupture and the resultant clinical sequelae. Metallic platinum coils are a typical, practical option to embolize cerebral aneurysms. However, the development of an alternative treatment modality is of interest because of poor occlusion permanence, coil migration, and coil compaction. Moreover, minimizing the implanted foreign materials during therapy is of importance not just to patients, but also to clinicians in the event an open surgical approach has to be pursued in the future. Polymeric injectable hydrogels have been investigated for transcatheter embolization and cell therapy with the potential for permanent aneurysm repair. This review focuses on how the combination of injectable embolic biomaterials and cell therapy may achieve minimally invasive remodeling of a degenerated cerebral artery with promise for superior outcomes in treatment of this devastating disease.

Biomimicked hierarchical 2D and 3D structures from natural templates: applications in cell biology

Intricate structures of natural surfaces and materials have amazed people over the ages. The unique properties of various surfaces also created interest and curiosity in researchers. In the recent past, with the advent of superior microscopy techniques, we have started to understand how these complex structures provide superior properties. With that knowledge, scientists have developed various biomimicked and bio-inspired surfaces for different non-biological applications. In the last two decades, we have also started to learn how structures of the tissue microenvironment influence cell function and behaviour, both in physiological and pathological conditions. Hence, it became essential to decipher the role and importance of structural hierarchy in the cellular context. With advances in microfabricated techniques, such complex structures were made by superimposing features of different dimensions. However, the fabricated topographies are far from matching the complexities presentin vivo. Hence, the need of biomimicking the natural surfaces for cellular applications was felt. In this review, we discuss a few examples of hierarchical surfaces found in plants, insects, and vertebrates. Such structures have been widely biomimicked for various applications but rarely studied for cell-substrate interaction and cellular response. Here, we discuss the research work wherein 2D hierarchical substrates were prepared using biomimicking to understand cellular functions such as adhesion, orientation, differentiation, and formation of spheroids. Further, we also present the status of ongoing research in mimicking 3D tissue architecture using de-cellularized plant-based and tissue/organ-based scaffolds. We will also discuss 3D printing for fabricating 2D and 3D hierarchical structures. The review will end by highlighting the various advantages and research challenges in this approach. The biomimickedin-vivolike substrate can be used to better understand cellular physiology, and for tissue engineering.

Circumferential esophageal replacement by a decellularized esophageal matrix in a porcine model

BACKGROUND

Tissue engineering is an attractive alternative to conventional esophageal replacement techniques using intra-abdominal organs which are associated with a substantial morbidity. The objective was to evaluate the feasibility of esophageal replacement by an allogenic decellularized esophagus in a porcine model. Secondary objectives were to evaluate the benefit of decellularized esophagus recellularization with autologous bone marrow mesenchymal stromal cells and omental maturation of the decellularized esophagus.

METHODS

Eighteen pigs divided into 4 experimental groups according to mesenchymal stromal cells recellularization and omental maturation underwent a 5-cm long circumferential replacement of the thoracic esophagus. Turbo green florescent protein labelling was used for in vivo mesenchymal stromal cells tracking. The graft area was covered by a stent for 3 months. Clinical and histologic outcomes were analyzed over a 6-month period.

RESULTS

The median follow-up was 112 days [5; 205]. Two animals died during the first postoperative month, 2 experienced an anastomotic leakage, 13 experienced a graft area stenosis following stent migration of which 3 were sacrificed as initially planned after successful endoscopic treatment. The stent could be removed in 2 animals: the graft area showed a continuous mucosa without stenosis. After 3 months, the graft area showed a tissue specific regeneration with a mature epithelium and muscular cells. Clinical and histologic results were similar across experimental groups.

CONCLUSION

Circumferential esophageal replacement by a decellularized esophagus was feasible and allowed tissue remodeling toward an esophageal phenotype. We could not demonstrate any benefit provided by the omental maturation of the decellularized esophagus nor its recellularization with mesenchymal stromal cells.

A Preliminary Study on the Promotion of Canine Adipose-Derived Stem Cell Differentiation by Perfusion-Decellularized Ureter Matrix

BACKGROUND

This study was to assess the possibility of the perfusing decellularized ureters (DUs) promoting the differentiation of the canine adipose stem cell (cASCs).

METHODS

cASCs were isolated and cultured in different induction media to determine their multidirectional differentiation potential. The perfusion system was used to prepare the DUs, and the prepared DUs were systematically evaluated. The DU coating was prepared by enzymatic digestion for cell culture. The cASCs were seeded on the coverslips covered with DU coating and samples were collected on days 3, 7, and 10. Immunofluorescence staining and molecular biology testing were used to examine the differentiation of cASCs seeded on the DU coating.

RESULTS

The cASCs were isolated and identified by flow cytometry. The prepared DUs removed the nuclear materials, and the 3-dimensional structure and biological compositions of the ureter were well preserved. Immunofluorescence staining showed the expression of anti-alpha smooth muscle actin (α-SMA). Western blot results suggested that the content of α-SMA in the experimental group was significantly higher than that in the control group at 3 different time points, and the mRNA expressions of α-SMA in the experimental group gradually increased with extended the culture time, whereas there was no significant change in the control group.

CONCLUSION

The cASCs seeded on the coverslips of DU coating could differentiate into smooth muscle cells, and the number of differentiated cASCs increased significantly with extended incubation time.