Atomic force microscopy for characterization of decellularized extracellular matrix (dECM) based materials

In live organisms, cells are embedded in tissue-specific extracellular matrix (ECM), which provides chemical and mechanical signals important for cell differentiation, migration, and overall functionality. Careful reproduction of ECM properties in artificial cell scaffolds is necessary to get physiologically relevant results of in vitro studies and produce robust materials for cell and tissue engineering. Nanoarchitectonics is a contemporary way to building complex materials from nano-scale objects of artificial and biological origin. Decellularized ECM (dECM), remaining after cell elimination from organs, tissues and cell cultures is arguably the closest equivalent of native ECM achievable today. dECM-based materials can be used as templates or components for producing cell scaffolds using nanoarchitectonic approach. Irrespective of the form, in which dECM is used (whole acellular organ/tissue, bioink or hydrogel), the local stiffness of the dECM scaffold must be evaluated, since the fate of seeded cells depends on the mechanical properties of their environment. Careful dECM characterization is also necessary to reproduce essential ECM traits in artificial cell scaffolds by nanoparticle assembly. Atomic force microscopy (AFM) is a valuable characterization tool, as it allows simultaneous assessment of mechanical and topographic features of the scaffold, and additionally evaluate the efficiency of decellularization process and preservation of the extracellular matrix. This review depicts the current application of AFM in the field of dECM-based materials, including the basics of AFM technique and the use of flicker-noise spectroscopy (FNS) method for the quantification of the dECM micro- and nanostructure.

Decellularized extracellular matrix-decorated 3D nanofiber scaffolds enhance cellular responses and tissue regeneration

The use of decellularized extracellular matrix products in tissue regeneration is quite alluring yet practically challenging due to the limitations of its availability, harsh processing techniques, and host rejection. Scaffolds obtained by either incorporating extracellular matrix (ECM) material or coating the surface can resolve these challenges to some extent. However, these scaffolds lack the complex 3D network formed by proteins and growth factors observed in natural ECM. This study introduces an approach utilizing 3D nanofiber scaffolds decorated with dECM to enhance cellular responses and promote tissue regeneration. Notably, the dECM can be customized according to specific cellular requirements, offering a tailored environment for enhanced therapeutic outcomes. Two types of 3D expanded scaffolds, namely radially aligned scaffolds (RAS) and laterally expanded scaffolds (LES) fabricated by the gas-foaming expansion were utilized. To demonstrate the proof-of-concept, human dermal fibroblasts (HDFs) seeded on these scaffolds for up to 8 weeks, resulted in uniform and highly aligned cells which deposited ECM on the scaffolds. These cellular components were then removed from the scaffolds through decellularization (e.g., SDS treatment and freeze-thaw cycles). The dECM-decorated 3D expanded nanofiber scaffolds can direct and support cell alignment and proliferation along the underlying fibers upon recellularization. An in vitro inflammation assay indicates that dECM-decorated LES induces a lower immune response than dECM-decorated RAS. Further, subcutaneous implantation of dECM-decorated RAS and LES shows higher cell infiltration and angiogenesis within 7 and 14 days than RAS and LES without dECM decoration. Taken together, dECM-decorated 3D expanded nanofiber scaffolds hold great potential in tissue regeneration and tissue modeling. STATEMENT OF SIGNIFICANCE: Decellularized ECM scaffolds have attained widespread attention in biomedical applications due to their intricate 3D framework of proteins and growth factors. Mimicking such a complicated architecture is a clinical challenge. In this study, we developed natural ECM-decorated 3D electrospun nanofiber scaffolds with controlled alignments to mimic human tissue. Fibroblasts were cultured on these scaffolds for 8 weeks to deposit natural ECM and decellularized by either freeze-thawing or detergent to obtain decellularized ECM scaffolds. These scaffolds were tested in both in-vitro and in-vivo conditions. They displayed higher cellular attributes with lower immune response making them a good grafting tool in tissue regeneration.

Primary Human Cell-Derived Extracellular Matrix from Decellularized Fibroblast Microtissues with Tissue-Dependent Composition and Microstructure

Purpose

Human extracellular matrix (ECM) exhibits complex protein composition and architecture depending on tissue and disease state, which remains challenging to reverse engineer. One promising approach is based on cell-secreted ECM from primary human fibroblasts that can be decellularized into acellular biomaterials. However, fibroblasts cultured on rigid culture plastic or biomaterial scaffolds can experience aberrant mechanical cues that perturb the biochemical, mechanical, and the efficiency of ECM production.

Methods

Here, we demonstrate a method for preparing decellularized ECM using primary human fibroblasts with tissue and disease-specific features with two case studies: (1) cardiac fibroblasts; (2) lung fibroblasts from healthy or diseased donors. Cells aggregate into engineered microtissues in low adhesion microwells that deposited ECM and can be decellularized. We systematically investigate microtissue morphology, matrix architecture, and mechanical properties, along with transcriptomic and proteomic analysis.

Results

Microtissues exhibited tissue-specific gene expression and proteomics profiling, with ECM complexity similar to native tissues. Healthy lung microtissues exhibited web-like fibrillar collagen compared to dense patches in healthy heart microtissues. Diseased lung exhibited more disrupted collagen architecture than healthy. Decellularized microtissues had tissue-specific mechanical stiffness that was physiologically relevant. Importantly, decellularized microtissues supported viability and proliferation of human cells.

Conclusions

We show that engineered microtissues of primary human fibroblasts seeded in low-adhesion microwells can be decellularized to produce human, tissue and disease-specific ECM. This approach should be widely applicable for generating personalized matrix that recapitulate tissues and disease states, relevant for culturing patient cells ex vivo as well as implantation for therapeutic treatments.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12195-024-00809-y.

Cell-Derived Matrix: Production, Decellularization, and Application of Wound Repair

Chronic nonhealing wounds significantly reduce patients' quality of life and are a major burden on healthcare systems. Over the past few decades, tissue engineering materials have emerged as a viable option for wound healing, with cell-derived extracellular matrix (CDM) showing remarkable results. The CDM's compatibility and resemblance to the natural tissue microenvironment confer distinct advantages to tissue-engineered scaffolds in wound repair. This review summarizes the current processes for CDM preparation, various cell decellularization protocols, and common characterization methods. Furthermore, it discusses the applications of CDM in wound healing, including skin defect and wound repair, angiogenesis, and engineered vessels, and offers perspectives on future developments.

Research Progress on Injectable Microspheres as New Strategies for the Treatment of Osteoarthritis Through Promotion of Cartilage Repair

Osteoarthritis (OA) is a degenerative disease caused by a variety of factors with joint pain as the main symptom, including fibrosis, chapping, ulcers, and loss of cartilage. Traditional treatment can only delay the progression of OA, and classical delivery system have many side effects. In recent years, microspheres have shown great application prospects in the field of OA treatment. Microspheres can support cells, reproduce the natural tissue microenvironment in vitro and in vivo, and are an efficient delivery system for the release of drugs or biological agents, which can promote cell proliferation, migration, and differentiation. Thus, they have been widely used in cartilage repair and regeneration. In this review, preparation processes, basic materials, and functional characteristics of various microspheres commonly used in OA treatment are systematically reviewed. Then it is introduced surface modification strategies that can improve the biological properties of microspheres and discussed a series of applications of microsphere functionalized scaffolds in OA treatment. Finally, based on bibliometrics research, the research development, future potential, and possible research hotspots of microspheres in the field of OA therapy is systematically and dynamically evaluated. The comprehensive and systematic review will bring new understanding to the field of microsphere treatment of OA.

The role of decellularized cell derived extracellular matrix in the establishment and culture ofin vitrobreast cancer tumor model

Decades of research have shown that two-dimensional cell culture studies are insufficient for preclinical cancer diagnosis and treatment, and that cancer cells in three-dimensional (3D) culture systems have better cell-cell and cell-matrix interactions, gene expression, heterogeneity, and structural complexity that more closely resemblein vivotumors. Researchers are still optimizing 3D culturing settings for different cancers. Despite promising tumor spheroid research, tumor cell-only aggregates lack the tumor microenvironment and cannot model tumors. Here, MCF-7 breast cancer cell derived decellularized extracellular matrix (CD-dECMs) were obtained and converted into autologous, biologically active, biocompatible, and non-immunogenic hydrogels to be used as micro-environment in both organoid formation and culture. For the production of organoids, CD-dECM doping concentrations ranging from 0.1 mg ml-1to 1.5 mg ml-1were evaluated, and the lowest concentration was found to be the most effective. For organoid culture, 8 mg ml-1CD-dECM, 4 mg ml-1rat tendon collagen type I (Col I) (4 mg ml-1) and a 1:1 (v/v) mixture of these two were used and the most viable and the biggest organoids were discovered in CD-dECM/Col I (1:1) group. The results show that autologous CD-dECM can replace hydrogels in tumor organoid generation and culture at low and high concentrations, respectively.

Decellularized extracellular matrix for organoid and engineered organ culture

The repair and regeneration of tissues and organs using engineered biomaterials has attracted great interest in tissue engineering and regenerative medicine. Recent advances in organoids and engineered organs technologies have enabled scientists to generate 3D tissue that recapitulate the structural and functional characteristics of native organs, opening up new avenues in regenerative medicine. The matrix is one of the most important aspects for improving organoids and engineered organs construction. However, the clinical application of these techniques remained a big challenge because current commercial matrix does not represent the complexity of native microenvironment, thereby limiting the optimal regenerative capacity. Decellularized extracellular matrix (dECM) is expected to maintain key native matrix biomolecules and is believed to hold enormous potential for regenerative medicine applications. Thus, it is worth investigating whether the dECM can be used as matrix for improving organoid and engineered organs construction. In this review, the characteristics of dECM and its preparation method were summarized. In addition, the present review highlights the applications of dECM in the fabrication of organoids and engineered organs.

Biomaterials combined with ADSCs for bone tissue engineering: current advances and applications

In recent decades, bone tissue engineering, which is supported by scaffold, seed cells and bioactive molecules (BMs), has provided new hope and direction for treating bone defects. In terms of seed cells, compared to bone marrow mesenchymal stem cells, which were widely utilized in previous years, adipose-derived stem cells (ADSCs) are becoming increasingly favored by researchers due to their abundant sources, easy availability and multi-differentiation potentials. However, there is no systematic theoretical basis for selecting appropriate biomaterials loaded with ADSCs. In this review, the regulatory effects of various biomaterials on the behavior of ADSCs are summarized from four perspectives, including biocompatibility, inflammation regulation, angiogenesis and osteogenesis, to illustrate the potential of combining various materials with ADSCs for the treatment of bone defects. In addition, we conclude the influence of additional application of various BMs on the bone repair effect of ADSCs, in order to provide more evidences and support for the selection or preparation of suitable biomaterials and BMs to work with ADSCs. More importantly, the associated clinical case reports and experiments are generalized to provide additional ideas for the clinical transformation and application of bone tissue engineering loaded with ADSCs.

Primary Human Cell-Derived Extracellular Matrix from Decellularized Fibroblast Microtissues with Tissue-Dependent Composition and Microstructure

Human extracellular matrix (ECM) exhibits complex protein composition and architecture depending on tissue and disease state, which remains challenging to reverse engineer. One promising approach is based on cell-secreted ECM from human fibroblasts, which can then be decellularized into an acellular biomaterial. However, fibroblasts initially seeded on rigid tissue culture plastic or biomaterial scaffolds experience aberrant mechanical cues that influence ECM deposition. Here, we show that engineered microtissues of primary human fibroblasts seeded in low-adhesion microwells can be decellularized to produce human, tissue-specific ECM. We investigate: 1) cardiac fibroblasts, as well as 2) lung fibroblasts from healthy, idiopathic fibrosis and chronic obstructive pulmonary disease donors. We demonstrate optimized culture and decellularization conditions, then characterize gene expression and protein composition. We further characterize ECM microstructure and mechanical properties. We envision that this method could be utilized for biomanufacturing of patient and tissue-specific ECM for organoid drug screening as well as implantable scaffolds.

Impact

In this study, we demonstrate a method for preparing decellularized matrix using primary human fibroblasts with tissue and disease-specific features. We aggregate single cell dispersions into engineered tissues using low adhesion microwells and show culture conditions that promote ECM deposition. We demonstrate this approach for cardiac fibroblasts as well as lung fibroblasts (both normal and diseased). We systematically investigate tissue morphology, matrix architecture, and mechanical properties, along with transcriptomic and proteomic analysis. This approach should be widely applicable for generating personalized ECM with features of patient tissues and disease state, relevant for culturing patient cells ex vivo as well as implantation for therapeutic treatments.

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.

Comparison of decellularization protocols for cultured cell-derived extracellular matrix-Effects on decellularization efficacy, extracellular matrix retention, and cell functions

The in vitro reconstruction of the extracellular matrix (ECM) is required in tissue engineering and regenerative medicine because the ECM can regulate cell functions in vivo. For ECM reconstruction, a decellularization technique is used. ECM reconstructed by decellularization (dECM) is prepared from tissues/organs and cultured cells. Although decellularization methods have been optimized for tissue-/organ-derived dECM, the methods for cultured cell-derived dECM have not yet been optimized. Here, two physical (osmotic shocks) and five chemical decellularization methods are compared. The decellularization efficacies were changed according to the decellularization methods used. Among them, only the Triton X-100 and Tween 20 treatments could not decellularize completely. Additionally, when the efficacies were compared among different types of cells (monolayered cells with/without strong cell adhesion, multilayered cells), the efficacies were decreased for multilayered cells or cells with strong cell adhesion. Retained ECM contents tended to be greater in the dECM prepared by osmotic shocks than in those prepared by chemical methods. The contents impacted cell adhesion, shapes, growth and intracellular signal activation on the dECM. The comparison would be helpful for the optimization of decellularization methods for cultured cells, and it could also provide new insights into developing milder decellularization methods for tissues and organs.

The biomimetic extracellular matrix: a therapeutic tool for breast cancer research

A deeper knowledge of the functional versatility and dynamic nature of the ECM has improved the understanding of cancer biology. Translational Significance: This work provides an in-depth view of the importance of the ECM to develop more mimetic breast cancer models, which aim to recreate the components and architecture of tumor microenvironment. Special focus is placed on decellularized matrices derived from tissue and cell culture, both in procurement and applications, as they have achieved great success in cancer research and pharmaceutical sector. The extracellular matrix (ECM) is increasingly recognized as a master regulator of cell behavior and response to breast cancer (BC) treatment. During BC progression, the mammary gland ECM is remodeled and altered in the composition and organization. Accumulated evidence suggests that changes in the composition and mechanics of ECM, orchestrated by tumor-stromal interactions along with ECM remodeling enzymes, are actively involved in BC progression and metastasis. Understanding how specific ECM components modulate the tumorigenic process has led to an increased interest in the development of biomaterial-based biomimetic ECM models to recapitulate key tumor characteristics. The decellularized ECMs (dECMs) have emerged as a promising in vitro 3D tumor model, whose recent advances in the processing and application could become the biomaterial by excellence for BC research and the pharmaceutical industry. This review offers a detailed view of the contribution of ECM in BC progression, and highlights the application of dECM-based biomaterials as promising personalized tumor models that more accurately mimic the tumorigenic mechanisms of BC and the response to treatment. This will allow the design of targeted therapeutic approaches adapted to the specific characteristics of each tumor that will have a great impact on the precision medicine applied to BC patients.

Personalized in vitro Extracellular Matrix Models of Collagen VI-Related Muscular Dystrophies

Collagen VI-related dystrophies (COL6-RDs) are a group of rare congenital neuromuscular dystrophies that represent a continuum of overlapping clinical phenotypes that go from the milder Bethlem myopathy (BM) to the severe Ullrich congenital muscular dystrophy, for which there is no effective treatment. Mutations in one of the three Collagen VI genes alter the incorporation of this protein into the extracellular matrix (ECM), affecting the assembly and the structural integrity of the whole fibrillar network. Clinical hallmarks of COL6-RDs are secondary to the ECM disruption and include muscle weakness, proximal joint contractures, and distal hyperlaxity. Although some traits have been identified in patients’ ECMs, a correlation between the ECM features and the clinical phenotype has not been established, mainly due to the lack of predictive and reliable models of the pathology. Herein, we engineered a new personalized pre-clinical model of COL6-RDs using cell-derived matrices (CDMs) technology to better recapitulate the complexity of the native scenario. We found that CDMs from COL6-RD patients presented alterations in ECM structure and composition, showing a significantly decreased Collagen VI secretion, especially in the more severe phenotypes, and a decrease in Fibrillin-1 inclusion. Next, we examined the Collagen VI-mediated deposition of Fibronectin in the ECM, finding a higher alignment, length, width, and straightness than in patients with COL6-RDs. Overall, these results indicate that CDMs models are promising tools to explore the alterations that arise in the composition and fibrillar architecture due to mutations in Collagen VI genes, especially in early stages of matrix organization. Ultimately, CDMs derived from COL6-RD patients may become relevant pre-clinical models, which may help identifying novel biomarkers to be employed in the clinics and to investigate novel therapeutic targets and treatments.

Bioactive Decellularized Extracellular Matrix Hydrogel Microspheres Fabricated Using a Temperature-Controlling Microfluidic System

Hydrogel microspheres have drawn great attention as functional three-dimensional (3D) microcarriers for cell attachment and growth, which have shown great potential in cell-based therapies and biomedical research. Hydrogels derived from a decellularized extracellular matrix (dECM) retain the intrinsic physical and biological cues from the native tissues, which often exhibit high bioactivity and tissue-specificity in promoting tissue regeneration. Herein, a novel two-stage temperature-controlling microfluidic system was developed which enabled production of pristine dECM hydrogel microspheres in a high-throughput manner. Porcine decellularized peripheral nerve matrix (pDNM) was used as the model raw dECM material for continuous generation of pDNM microgels without additional supporting materials or chemical crosslinking. The sizes of the microspheres were well-controlled by tuning the feed ratios of water/oil phases into the microfluidic device. The resulting pDNM microspheres (pDNM-MSs) were relatively stable, which maintained a spherical shape and a nanofibrous ultrastructure for at least 14 days. Schwann cells and PC12 cells preseeded on the pDNM-MSs not only showed excellent viability and an adhesive property, but also promoted cell extension compared to the commercially available gelatin microspheres. Moreover, primary neural stem/progenitor cells attached well to the pDNM-MSs, which further facilitated their proliferation. The successfully fabricated dECM hydrogel microspheres provided a highly bioactive microenvironment for 3D cell culture and functionalization, which showed promising potential in versatile biomedical applications.

Decellularized extracellular matrix scaffolds: Recent trends and emerging strategies in tissue engineering

The application of scaffolding materials is believed to hold enormous potential for tissue regeneration. Despite the widespread application and rapid advance of several tissue-engineered scaffolds such as natural and synthetic polymer-based scaffolds, they have limited repair capacity due to the difficulties in overcoming the immunogenicity, simulating in-vivo microenvironment, and performing mechanical or biochemical properties similar to native organs/tissues. Fortunately, the emergence of decellularized extracellular matrix (dECM) scaffolds provides an attractive way to overcome these hurdles, which mimic an optimal non-immune environment with native three-dimensional structures and various bioactive components. The consequent cell-seeded construct based on dECM scaffolds, especially stem cell-recellularized construct, is considered an ideal choice for regenerating functional organs/tissues. Herein, we review recent developments in dECM scaffolds and put forward perspectives accordingly, with particular focus on the concept and fabrication of decellularized scaffolds, as well as the application of decellularized scaffolds and their combinations with stem cells (recellularized scaffolds) in tissue engineering, including skin, bone, nerve, heart, along with lung, liver and kidney.

Novel Corneal Endothelial Cell Carrier Couples a Biodegradable Polymer and a Mesenchymal Stem Cell-Derived Extracellular Matrix

Here, we report a transparent, biodegradable, and cell-adhesive carrier that is securely coupled with the extracellular matrix (ECM) for corneal endothelial cell (CEC) transplantation. To fabricate a CEC carrier, poly(lactide-co-caprolactone) (PLCL) solution was poured onto the decellularized ECM (UMDM) derived from in vitro cultured umbilical cord blood-MSCs. Once completely dried, ECM-PLCL was then peeled off from the substrate. It was 20 μm thick, transparent, rich in fibronectin and collagen type IV, and easy to handle. Surface characterizations exhibited that ECM-PLCL was very rough (54.0 ± 4.50 nm) and uniformly covered in high density by ECM and retained a positive surface charge (65.2 ± 57.8 mV), as assessed via atomic force microscopy. Human CECs (B4G12) on the ECM-PLCL showed good cell attachment, with a cell density similar to the normal cornea. They could also maintain a cell phenotype, with nicely formed cell-cell junctions as assessed via ZO-1 and N-cadherin at 14 days. This was in sharp contrast to the CEC behaviors on the FNC-coated PLCL (positive control). A function-related marker, Na⁺/K⁺-ATPase, was also identified via western blot and immunofluorescence. In addition, primary rabbit CECs showed a normal shape and they could express structural and functional proteins on the ECM-PLCL. A simulation test confirmed that CECs loaded on the ECM-PLCL were successfully engrafted into the decellularized porcine corneal tissue, with a high engraftment level and cell viability. Moreover, ECM-PLCL transplantation into the anterior chamber of the rabbit eye for 8 weeks proved the maintenance of normal cornea properties. Taken together, this study demonstrates that our ECM-PLCL can be a promising cornea endothelium graft with an excellent ECM microenvironment for CECs.

Instructive Hydrogels for Primary Tumor Cell Culture: Current Status and Outlook

Primary tumor organoids (PTOs) growth in hydrogels have emerged as an important in vitro model that recapitulates many characteristics of the native tumor tissue, and have important applications in fundamental cancer research and for the development of useful therapeutic treatment. This paper begins with reviewing the methods of isolation of primary tumor cells. Then, recent advances on the instructive hydrogels as biomimetic extracellular matrix for primary tumor cell culture and construction of PTO models are summarized. Emerging microtechnology for growth of PTOs in microscale hydrogels and the applications of PTOs are highlighted. This paper concludes with an outlook on the future directions in the investigation of instructive hydrogels for PTO growth.

Application of decellularized bone matrix as a bioscaffold in bone tissue engineering

Autologous bone grafts are commonly used as the gold standard to repair and regenerate diseased bones. However, they are strongly associated with postoperative complications, especially at the donor site, and increased surgical costs. In an effort to overcome these limitations, tissue engineering (TE) has been proposed as an alternative to promote bone repair. The successful outcome of tissue engineering depends on the microstructure and composition of the materials used as scaffold. Decellularized bone matrix-based biomaterials have been applied as bioscaffolds in bone tissue engineering. These biomaterials play an important role in providing the mechanical and physical microenvironment needed by cells to proliferate and survive. Decellularized extracellular matrix (dECM) can be used as a powder, hydrogel and electrospun scaffolds. These bioscaffolds mimic the native microenvironment due to their structure similar to the original tissue. The aim of this review is to highlight the bone decellularization techniques. Herein we discuss: (1) bone structure; (2) properties of an ideal scaffold; (3) the potential of decellularized bone as bioscaffolds; (4) terminal sterilization of decellularized bone; (5) cell removing confirmation in decellularized tissues; and (6) post decellularization procedures. Finally, the improvement of bone formation by dECM and the immunogenicity aspect of using the decellularized bone matrix are presented, to illustrate how novel dECM-based materials can be used as bioscaffold in tissue engineering. A comprehensive understanding of tissue engineering may allow for better incorporation of therapeutic approaches in bone defects allowing for bone repair and regeneration.

A decellularized extracellular matrix derived from keratinocytes can suppress cellular senescence induced by replicative and oxidative stresses

Keratinocyte senescence is suppressed on a keratinocyte-derived decellularized ECM (dECM) through the increase of antioxidant activity. Keratinocyte function is also increased on this dECM, suggesting that this dECM is useful to establish epidermal models.

Decellularized Extracellular Matrix for Cell Biology

The extracellular matrix (ECM) is an architecture that supports the cells in our bodies and regulates various cell functions. The ECM is composed of many proteins and carbohydrates, and these molecules activate various intracellular signaling pathways orchestrated to decide cell fates. Therefore, it is not enough to study the role of single ECM molecules to understand the roles of the ECM in the regulation of cell functions; it is necessary to understand how the ECM, as an assembly of various molecules, regulates cell functions as a whole. For this purpose, in vitro ECM models mimicking native ECM are required. Here, a decellularization technique is presented to reconstitute native ECM in vitro. In this article, methods for preparing decellularized ECM (dECM) are described for use in tumor and stem cell biology. Additionally, a method for confirmation of decellularization and a dECM modification method are described. These dECM types will be useful for comprehensive studies of ECM roles. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Preparation of in vitro extracellular matrix (ECM) models mimicking native ECM in different malignant tumor tissues Basic Protocol 2: Preparation of in vitro ECM models mimicking native ECM surrounding myoblasts differentiating into myotubes at each myogenic stage Support Protocol 1: Confirmation of myogenic stages by myogenic stages by myogenic gene expression analysis Basic Protocol 3: Confirmation of cell removal Basic Protocol 4: Reduction of chondroitin sulfate chains in cultured cell-derived decellularized ECM Support Protocol 2: Quantification of chondroitin sulfate chain amounts in the decellularized ECM.

A simple method for decellularizing a cell-derived matrix for bone cell cultivation and differentiation

The extracellular matrix regulates cell survival, proliferation, and differentiation. In vitro two-dimensional cell experiments are typically performed on a plastic plate or a substrate of a single extracellular matrix constituent such as collagen or calcium phosphate. As these approaches do not include extracellular matrix proteins or growth factors, they fail to mimic a complex cell microenvironment. The cell-derived matrix is an alternative platform for better representing the in vivo microenvironment in vitro. Standard decellularization of a cell-derived matrix is achieved by combining chemical and physical methods. In this study, we compared the decellularization efficacy of several methods: ammonium hydroxide, sodium dodecyl sulfate (SDS), or Triton X-100 with cold or heat treatment on a matrix of Saos-2 cells. We found that the protocols containing SDS were cytotoxic during recellularization. Heat treatment at 47 °C was not cytotoxic, removed cellular constituents, inactivated alkaline phosphatase activity, and maintained the levels of calcium deposition. Subsequently, we investigated the differentiation efficiency of a direct bone coculture system in the established decellularized Saos-2 matrix, an inorganic matrix of calcium phosphate, and a plastic plate as a control. We found that the decellularized Saos-2 cell matrix obtained by heat treatment at 47 °C enhanced osteoclast differentiation and matrix mineralization better than the inorganic matrix and the control. This simple and low-cost method allows us to create a Saos-2 decellularized matrix that can be used as an in vivo-like support for the growth and differentiation of bone cells.

Application of bone and cartilage extracellular matrices in articular cartilage regeneration

Articular cartilage has an avascular structure with a poor ability for self-repair; therefore, many challenges arise in cases of trauma or disease. It is of utmost importance to identify the proper biomaterial for tissue repair that has the capability to direct cell recruitment, proliferation, differentiation, and tissue integration by imitating the natural microenvironment of cells and transmitting an orchestra of intracellular signals. Cartilage extracellular matrix (cECM) is a complex nanostructure composed of divergent proteins and glycosaminoglycans (GAGs), which regulate many functions of resident cells. Numerous studies have shown the remarkable capacity of ECM-derived biomaterials for tissue repair and regeneration. Moreover, given the importance of biodegradability, biocompatibility, 3D structure, porosity, and mechanical stability in the design of suitable scaffolds for cartilage tissue engineering, demineralized bone matrix (DBM) appears to be a promising biomaterial for this purpose, as it possesses the aforementioned characteristics inherently. To the best of the authors' knowledge, no comprehensive review study on the use of DBM in cartilage tissue engineering has previously been published. Since so much work is needed to address DBM limitations such as pore size, cell retention, and so on, we decided to draw the attention of researchers in this field by compiling a list of recent publications. This review discusses the implementation of composite scaffolds of natural or synthetic origin functionalized with cECM or DBM in cartilage tissue engineering. Cutting-edge advances and limitations are also discussed in an attempt to provide guidance to researchers and clinicians.

Development of a Biomimetic Hydrogel Based on Predifferentiated Mesenchymal Stem-Cell-Derived ECM for Cartilage Tissue Engineering

The use of decellularized extracellular matrix (dECM) as a biomaterial has been an important step forward for the development of functional tissue constructs. In addition to tissues and organs, cell cultures are gaining a lot of attention as an alternative source of dECM. In this work, a novel biomimetic hydrogel is developed based on dECM obtained from mesenchymal stem cells (mdECM) for cartilage tissue engineering. To this end, cells are seeded under specific culture conditions to generate an early chondrogenic extracellular matrix (ECM) providing cues and elements necessary for cartilage development. The composition is determined by quantitative, histological, and mass spectrometry techniques. Moreover, the decellularization process is evaluated by measuring the DNA content and compositional analyses, and the hydrogel is formulated at different concentrations (3% and 6% w/v). Results show that mdECM derived hydrogels possess excellent biocompatibility and suitable physicochemical and mechanical properties for their injectability. Furthermore, it is evidenced that this hydrogel is able to induce chondrogenesis of mesenchymal stem cells (MSCs) without supplemental factors and, furthermore, to form hyaline cartilage-like tissue after in vivo implantation. These findings demonstrate for the first time the potential of this hydrogel based on mdECM for applications in cartilage repair and regeneration.

Atomic force microscopy for revealing micro/nanoscale mechanics in tumor metastasis: from single cells to microenvironmental cues

Mechanics are intrinsic properties which appears throughout the formation, development, and aging processes of biological systems. Mechanics have been shown to play important roles in regulating the development and metastasis of tumors, and understanding tumor mechanics has emerged as a promising way to reveal the underlying mechanisms guiding tumor behaviors. In particular, tumors are highly complex diseases associated with multifaceted factors, including alterations in cancerous cells, tissues, and organs as well as microenvironmental cues, indicating that investigating tumor mechanics on multiple levels is significantly helpful for comprehensively understanding the effects of mechanics on tumor progression. Recently, diverse techniques have been developed for probing the mechanics of tumors, among which atomic force microscopy (AFM) has appeared as an excellent platform enabling simultaneously characterizing the structures and mechanical properties of living biological systems ranging from individual molecules and cells to tissue samples with unprecedented spatiotemporal resolution, offering novel possibilities for understanding tumor physics and contributing much to the studies of cancer. In this review, we survey the recent progress that has been achieved with the use of AFM for revealing micro/nanoscale mechanics in tumor development and metastasis. Challenges and future progress are also discussed.

Cell-free scaffolds functionalized with bionic cartilage acellular matrix microspheres to enhance the microfracture treatment of articular cartilage defects

Microfracture surgery remains the most popular treatment for articular cartilage lesions in the clinic, but often leads to the formation of inferior fibrocartilage tissue and damage to subchondral bone. To overcome these problems, extracellular matrix (ECM) scaffolds derived from decellularized natural cartilaginous tissues were introduced and showed excellent biological properties to direct the differentiation of bone marrow stem cells. However, besides the limited allogenic/allogenic supply and the risk of disease transfer from xenogeneic tissues, the effectiveness of ECM scaffolds always varied with a high variability of natural tissue quality. In this study, we developed composite scaffolds functionalized with a cell-derived ECM source, namely, bionic cartilage acellular matrix microspheres (BCAMMs), that support the chondrogenic differentiation of bone marrow cells released from microfracture. The scaffolds with BCAMMs at different developmental stages were investigated in articular cartilage regeneration and subchondral bone repair. Compared to microfracture, the addition of cell-free BCAMM scaffolds has demonstrated a great improvement of regenerated cartilage tissue quality in a rabbit model as characterized by a semi-quantitative analysis of cells, histology and biochemical assays as well as micro-CT images. Moreover, the variation in ECM properties was found to significantly affect the cartilage regeneration, highlighting the challenges of homogenous scaffolds in working with microfracture. Together, our results demonstrate that the biofunctionalized BCAMM scaffold with cell-derived ECM shows great potential to combine with microfracture for clinical translation to repair cartilage defects.

Cell-Derived Extracellular Matrix for Tissue Engineering and Regenerative Medicine

Cell-derived extracellular matrices (CD-ECMs) captured increasing attention since the first studies in the 1980s. The biological resemblance of CD-ECMs to their in vivo counterparts and natural complexity provide them with a prevailing bioactivity. CD-ECMs offer the opportunity to produce microenvironments with costumizable biological and biophysical properties in a controlled setting. As a result, CD-ECMs can improve cellular functions such as stemness or be employed as a platform to study cellular niches in health and disease. Either on their own or integrated with other materials, CD-ECMs can also be utilized as biomaterials to engineer tissues de novo or facilitate endogenous healing and regeneration. This review provides a brief overview over the methodologies used to facilitate CD-ECM deposition and manufacturing. It explores the versatile uses of CD-ECM in fundamental research and therapeutic approaches, while highlighting innovative strategies. Furthermore, current challenges are identified and it is accentuated that advancements in methodologies, as well as innovative interdisciplinary approaches are needed to take CD-ECM-based research to the next level.

Mesenchymal Stromal Cell-Produced Components of Extracellular Matrix Potentiate Multipotent Stem Cell Response to Differentiation Stimuli

Extracellular matrix (ECM) provides both structural support and dynamic microenvironment for cells regulating their behavior and fate. As a critical component of stem cell niche ECM maintains stem cells and activates their proliferation and differentiation under specific stimuli. Mesenchymal stem/stromal cells (MSCs) regulate tissue-specific stem cell functions locating in their immediate microenvironment and producing various bioactive factors, including ECM components. We evaluated the ability of MSC-produced ECM to restore stem and progenitor cell microenvironment in vitro and analyzed the possible mechanisms of its effects. Human MSC cell sheets were decellularized by different agents (detergents, enzymes, and apoptosis inductors) to select the optimized combination (CHAPS and DNAse I) based on the conservation of decellularized ECM (dECM) structure and effectiveness of DNA removal. Prepared dECM was non-immunogenic, supported MSC proliferation and formation of larger colonies in colony-forming unit-assay. Decellularized ECM effectively promoted MSC trilineage differentiation (adipogenic, osteogenic, and chondrogenic) compared to plastic or plastic covered by selected ECM components (collagen, fibronectin, laminin). Interestingly, dECM produced by human fibroblasts could not enhance MSC differentiation like MSC-produced dECM, indicating cell-specific functionality of dECM. We demonstrated the significant integrin contribution in dECM-cell interaction by blocking the stimulatory effects of dECM with RGD peptide and suggested the involvement of key intracellular signaling pathways activation (pERK/ERK and pFAK/FAK axes, pYAP/YAP and beta-catenin) in the observed processes based on the results of inhibitory analysis. Taken together, we suppose that MSC-produced dECM may mimic stem cell niche components in vitro and maintain multipotent progenitor cells to insure their effective response to external differentiating stimuli upon activation. The obtained data provide more insights into the possible role of MSC-produced ECM in stem and progenitor cell regulation within their niches. Our results are also useful for the developing of dECM-based cell-free products for regenerative medicine.

In Vitro Biocompatibility of Decellularized Cultured Plant Cell-Derived Matrices

There has been a recent increase in exploring the use of decellularized plant tissue as a novel "green" material for biomedical applications. As part of this effort, we have developed a technique to decellularize cultured plant cells (tobacco BY-2 cells and rice cells) and tissue (tobacco hairy roots) that uses deoxyribonuclease I (DNase I)). As a proof of concept, all cultured plant cells and tissue were transformed to express recombinant enhanced green fluorescent protein (EGFP) to show that the proteins of interest could be retained within the matrices. Decellularization of lyophilized tobacco BY-2 cells with DNase for 30 min depleted the DNA content from 1503 ± 459 to 31 ± 5 ng/sample. The decellularization procedure resulted in approximately 36% total protein retention (154 ± 60 vs 424 ± 70 μg/sample) and 33% EGFP retention. Similar results for DNA removal and protein retention were observed with the rice cells and tobacco hairy root matrices. When exposed to decellularized BY-2 cell-derived matrices, monolayer cultures of human foreskin fibroblasts (hFFs) maintained or increased metabolic activity, which is an indicator of cell viability. Furthermore, hFFs were able to attach, spread, and proliferate when cultured with the decellularized BY-2 cell-derived matrices in an aggregate model. Overall, these studies demonstrate that cultured plant cells and tissue can be effectively decellularized with DNase I with substantial protein retention. The resulting material has a positive impact on hFF metabolic activity and could be employed to create a three-dimensional environment for cell growth. These results thus show the promise of using naturally derived cellulose matrices from cultured plant cells and tissues for biomedical applications.

Decellularized extracellular matrices derived from cultured cells at stepwise myogenic stages for the regulation of myotube formation

The regulation of stem cell differentiation is key for muscle tissue engineering and regenerative medicine. To this end, various substrates mimicking the native extracellular matrix (ECM) have been developed with consideration of the mechanical, topological, and biochemical properties. However, mimicking the biochemical properties of the native ECM is difficult due to its compositional complexity. To develop substrates that mimic the native ECM and its biochemical properties, decellularization is typically used. Here, substrates mimicking the native ECM at each myogenic stage are prepared as stepwise myogenesis-mimicking matrices via the in vitro myogenic culture of C2C12 myoblasts and decellularization. Cells adhered to the stepwise myogenesis-mimicking matrices at similar levels. However, the matrices derived from cells at the myogenic early stage suppressed cell growth and promoted myogenesis. This promotion of myogenesis was potentially due to the suppression of the activation of endogenous BMP signaling following the suppression of the expression of the myogenic-inhibitory factors, Id2 and Id3. Our stepwise myogenesis-mimicking matrices will be suitable ECM models for basic biological research and myogenesis of stem cells. Further, these matrices will provide insights that improve the efficacy of decellularized ECM for muscle repair.

Assessing drug response in engineered brain microenvironments

Tissue engineered systems are important models for the testing and discovery of therapeutics against a number of diseases. The use of these models in vitro can expand both our understanding of the mechanisms behind disease and allow for higher throughput and personalized modeling of therapeutic response. Over the past decade there has been an explosion of models of neurological disorders that can be used in vitro to study new therapies against devastating neurodegenerative, neurodevelopmental, and neuro-oncological disease. These models span several types of engineered microenvironments which are produced using microfluidic devices, microtissue technology and/or the incorporation of biomaterial scaffolds to model neurological conditions such as; Alzheimer's disease, idiopathic autism, Parkinson's disease, Zika-induced microcephaly and neoplasms. Using engineered brain microenvironments, therapeutics can be tested in more physiologically relevant ways leading to new knowledge of the underlying causes and interactions occurring at the tissue level. However, much is still left to learn and model within these systems to make them truly valuable in the discovery and testing of novel therapies. Here we review the current state of the art of engineered brain microenvironments being used specifically to screen and test new therapeutic strategies and discuss the current benefits and limitations that still exist.

Decellularized Extracellular Matrix for Cancer Research

Genetic mutation and alterations of intracellular signaling have been focused on to understand the mechanisms of oncogenesis and cancer progression. Currently, it is pointed out to consider cancer as tissues. The extracellular microenvironment, including the extracellular matrix (ECM), is important for the regulation of cancer cell behavior. To comprehensively investigate ECM roles in the regulation of cancer cell behavior, decellularized ECM (dECM) is now used as an in vitro ECM model. In this review, I classify dECM with respect to its sources and summarize the preparation and characterization methods for dECM. Additionally, the examples of cancer research using the dECM were introduced. Finally, future perspectives of cancer studies with dECM are described in the conclusions.

PLGA–collagen–ECM hybrid scaffolds functionalized with biomimetic extracellular matrices secreted by mesenchymal stem cells during stepwise osteogenesis-co-adipogenesis

Development of an in vitro 3D model that reflects the dynamic remodeling of ECMs during simultaneous osteogenesis and adipogenesis of hMSCs.

An extracellular matrix (ECM) model at high malignant colorectal tumor increases chondroitin sulfate chains to promote epithelial-mesenchymal transition and chemoresistance acquisition

Chemoresistance is one of the major barriers for tumor chemotherapy. It is clinically known that chemoresistance increases during tumor progression. Additionally, the extracellular matrix (ECM) is also remodeled during tumor progression. However, it remains unclear how ECM remodeling contributes to chemoresistance acquisition. Recently, it has been reported that epithelial-mesenchymal transition (EMT) contributes to chemoresistance acquisition. Here, how ECM remodeling contributes to 5-fluorouracil (5-FU) resistance acquisition was investigated from the viewpoints of EMT using in vitro ECM models mimicking native ECM in colorectal tumor tissue at three different malignant levels. 5-FU partially induced EMT and increased ABCB1 in colorectal HT-29 cells via TGF-β signaling (an invasive tumor cell model). When HT-29 cells were cultured on an ECM model (high malignant matrices) mimicking native ECM in highly malignant tumor tissues, the cells facilitated TGF-β-induced EMT and increased ABCB1 upregulation compared with that of other ECM models mimicking the low malignant level and normal tissues. High malignant matrices contained more chondroitin sulfate (CS) chains than those of other ECM models. Finally, CS chain-reduced high malignant matrices could not facilitate ABCB1 upregulation and TGF-β-induced EMT. These results demonstrated that ECM remodeling during tumor progression increased CS chains to facilitate EMT and ABCB1 upregulation, contributing to chemoresistance acquisition.

Current Status of Tissue Engineering in the Management of Severe Hypospadias

Hypospadias, characterized by misplacement of the urinary meatus in the lower side of the penis, is a frequent birth defect in male children. Because of the huge variation in the anatomic presentation of hypospadias, no single urethroplasty procedure is suitable for all situations. Hence, many surgical techniques have emerged to address the shortage of tissues required to bridge the gap in the urethra particularly in the severe forms of hypospadias. However, the rate of postoperative complications of currently available surgical procedures reaches up to one-fourth of the patients having severe hypospadias. Moreover, these urethroplasty techniques are technically demanding and require considerable surgical experience. These limitations have fueled the development of novel tissue engineering techniques that aim to simplify the surgical procedures and to reduce the rate of complications. Several types of biomaterials have been considered for urethral repair, including synthetic and natural polymers, which in some cases have been seeded with cells prior to implantation. These methods have been tested in preclinical and clinical studies, with variable degrees of success. This review describes the different urethral tissue engineering methodologies, with focus on the approaches used for the treatment of hypospadias. At present, despite many significant advances, the search for a suitable tissue engineering approach for use in routine clinical applications continues.

Biomaterials for Regenerative Medicine: Historical Perspectives and Current Trends

Biomaterials are key components in tissue engineering and regenerative medicine applications, with the intended purpose of reducing the burden of disease and enhancing the quality of life of a large number of patients. The success of many regenerative medicine strategies, such as cell-based therapies, artificial organs, and engineered living tissues, is highly dependent on the ability to design or produce suitable biomaterials that can support and guide cells during tissue healing and remodelling processes. This chapter presents an overview about basic research concerning the use of different biomaterials for tissue engineering and regenerative medicine applications. Starting from a historical perspective, the chapter introduces the basic principles of designing biomaterials for tissue regeneration approaches. The main focus is set on describing the main classes of biomaterials that have been applied in regenerative medicine, including natural and synthetic polymers, bioactive ceramics, and composites. For each class of biomaterials, some of the most important physicochemical and biological properties are presented. Finally, some challenges and concerns that remain in this field are presented and discussed.