Novel Decellularization Method for Tissue Slices

Live imaging of the extracellular matrix with a glycan-binding fluorophore

All multicellular systems produce and dynamically regulate extracellular matrices (ECMs) that play essential roles in both biochemical and mechanical signaling. Though the spatial arrangement of these extracellular assemblies is critical to their biological functions, visualization of ECM structure is challenging, in part because the biomolecules that compose the ECM are difficult to fluorescently label individually and collectively. Here, we present a cell-impermeable small-molecule fluorophore, termed Rhobo6, that turns on and red shifts upon reversible binding to glycans. Given that most ECM components are densely glycosylated, the dye enables wash-free visualization of ECM, in systems ranging from in vitro substrates to in vivo mouse mammary tumors. Relative to existing techniques, Rhobo6 provides a broad substrate profile, superior tissue penetration, non-perturbative labeling, and negligible photobleaching. This work establishes a straightforward method for imaging the distribution of ECM in live tissues and organisms, lowering barriers for investigation of extracellular biology.

Evaluation methods for decellularized tissues: A focus on human amniotic membrane

Tissue engineering, a multidisciplinary research field aiming to revolutionize regenerative medicine, relies on scaffolds for optimal cell cultures and organ development. Decellularized tissue extracellular matrices (dECM) scaffolds, particularly from human amniotic membrane (hAM), show promise in clinical applications. This review discusses the significance of scaffolds, emphasizing dECM-based hAM scaffolds, delving into ECM complexities, decellularization processes, and evaluation methods. Raman spectroscopy emerges as a non-destructive tool for evaluating ECM preservation, presenting potential for quantifying ECM components in hAM before and after decellularization. The review explores the role of hAM as a biomaterial, detailing its composition and characteristics and emphasizes the importance of evaluating ultrastructural components and suggests Raman spectroscopy as a valuable technique for this purpose.

Decellularization and Enzymatic Digestion Methods to Enhance ECM Protein Detection via MALDI-MS Imaging

Matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) has been used to generate spatial maps of lipids, metabolites, peptides, proteins, and glycans in tissues; however, its use for mapping extracellular matrix (ECM) protein distributions is underexplored. ECM proteins play a major role in various pathological conditions, and changes in their spatial distributions affect the function and morphology of cells within tissues. ECM protein detection is challenging because they are large, insoluble, and undergo various post-translational modifications, such as glycosylation. We describe here decellularization of tissue sections coupled with serial enzymatic digestions with PNGaseF and trypsin to improve ECM protein detection in MALDI-MSI without disrupting ECM architecture. Decellularization leads to a 3-fold increase in the number of proteins that are measured by MALDI-MSI. We also introduce a binary colocalization method to improve protein identification, which increases the number of proteins that are confidently detected. Together, these methods enhance the spatial mapping of ECM proteins by MALDI-MSI.

Innovative approaches to tissue engineering: Utilizing decellularized extracellular matrix hydrogels for mesenchymal stem cell transport

In recent years, the realm of tissue regeneration experienced significant advancements, leading to the development of innovative therapeutic agents. The systemic delivery of mesenchymal stem cells (MSCs) emerged as a promising strategy for promoting tissue regeneration. However, this approach is hindered by hurdles such as poor cell survival, limited cell propagation, and inadequate cell integration. Decellularized extracellular matrix (dECM) hydrogel serves as an innovative carrier that protects MSCs from the detrimental effects of the hostile microenvironment, facilitates their localization and retention at the injection site, and preserves their viability. Regarding its low immunogenicity, low cytotoxicity, high biocompatibility, and its ability to mimic natural extracellular matrix (ECM), this natural hydrogel offers a new avenue for systemic delivery of MSCs. This review digs into the properties of dECM hydrogels (dECMHs), the methods employed for decellularization and the utilization of dECMH as carriers for various types of MSCs for tissue regeneration purposes. This review also sheds light on the benefits of hybrid hydrogels composed of dECMH and other components such as proteins and polysaccharides. By addressing the limitations of conventional hydrogels and enhancing efficacy of cell therapy, dECMH opens new pathways for the future of tissue regeneration.

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.

Stem cells, cell therapies, and bioengineering in lung biology and diseases 2023

Repair and regeneration of a diseased lung using stem cells or bioengineered tissues is an exciting therapeutic approach for a variety of lung diseases and critical illnesses. Over the past decade, increasing evidence from preclinical models suggests that mesenchymal stromal cells, which are not normally resident in the lung, can be used to modulate immune responses after injury, but there have been challenges in translating these promising findings to the clinic. In parallel, there has been a surge in bioengineering studies investigating the use of artificial and acellular lung matrices as scaffolds for three-dimensional lung or airway regeneration, with some recent attempts of transplantation in large animal models. The combination of these studies with those involving stem cells, induced pluripotent stem cell derivatives, and/or cell therapies is a promising and rapidly developing research area. These studies have been further paralleled by significant increases in our understanding of the molecular and cellular events by which endogenous lung stem and/or progenitor cells arise during lung development and participate in normal and pathological remodeling after lung injury. For the 2023 Stem Cells, Cell Therapies, and Bioengineering in Lung Biology and Diseases Conference, scientific symposia were chosen to reflect the most cutting-edge advances in these fields. Sessions focused on the integration of "omics" technologies with function, the influence of immune cells on regeneration, and the role of the extracellular matrix in regeneration. The necessity for basic science studies to enhance fundamental understanding of lung regeneration and to design innovative translational studies was reinforced throughout the conference.

Establishment of 3D cell culture systems with decellularized lung-derived extracellular matrix hydrogel scaffold

Decellularized tissue hydrogels, especially that mimic the native tissue, have a high potential for tissue engineering, three-dimensional (3D) cell culture, bioprinting, and therapeutic agent encapsulation due to their excellent biocompatibility and ability to facilitate the growth of cells. It is important to note that the decellularization process significantly affects the structural integrity and properties of the extracellular matrix, which in turn shapes the characteristics of the resulting hydrogels at the macromolecular level. Therefore, our study aims to identify an effective chemical decellularization method for sheep lung tissue, using a mixing/agitation technique with a range of detergents, including commonly [Sodium dodecyl sulfate (SDS), Triton X-100, and 3-((3-cholamidopropyl) dimethylammonio)-1-propanesulfonate] (CHAPS), and rarely used (sodium cholate hydrate, NP-40, and 3-[N,N-Dimethyl(3-myristoylaminopropyl)ammonio]propanesulfonate) (ASB-14). After the effectiveness of the used detergents on decellularization was determined by histological and biochemical methods, lung derived decellularized extracellular matrix was converted into hydrogel. We investigated the interactions between lung cells and decellularized extracellular matrix using proliferation assay, scanning electron microscopy, and immunofluorescence microscopy methods on BEAS-2B cells in air-liquid interface. Notably, this study emphasizes the effectiveness of ASB-14 in the decellularization process, showcasing its crucial role in removing cellular components while preserving vital extracellular matrix biological macromolecules, including glycosaminoglycans, collagen, and elastin. The resulting hydrogels demonstrated favorable mechanical properties and are compatible with both cell-cell and cell-extracellular matrix interactions.

Effects of aging on the biomechanical properties of the lung extracellular matrix: dependence on tissular stretch

Introduction: Aging induces functional and structural changes in the lung, characterized by a decline in elasticity and diminished pulmonary remodeling and regenerative capacity. Emerging evidence suggests that most biomechanical alterations in the lung result from changes in the composition of the lung extracellular matrix (ECM), potentially modulating the behavior of pulmonary cells and increasing the susceptibility to chronic lung diseases. Therefore, it is crucial to investigate the mechanical properties of the aged lung. This study aims to assess the mechanical alterations in the lung ECM due to aging at both residual (RV) and functional (FV) lung volumes and to evaluate their effects on the survival and proliferation of mesenchymal stromal cells (MSCs). Methods: The lungs from young (4-6-month-old) and aged (20-24-month-old) mice were inflated with optimal cutting temperature compound to reach FV or non-inflated (RV). ECM proteins laminin, collagen I and fibronectin were quantified by immunofluorescence and the mechanical properties of the decellularized lung sections were assessed using atomic force microscopy. To investigate whether changes in ECM composition by aging and/or mechanical properties at RV and FV volumes affects MSCs, their viability and proliferation were evaluated after 72 h. Results: Laminin presence was significantly reduced in aged mice compared to young mice, while fibronectin and collagen I were significantly increased in aged mice. In RV conditions, the acellular lungs from aged mice were significantly softer than from young mice. By contrast, in FV conditions, the aged lung ECM becomes stiffer than that of in young mice, revealing that strain hardening significantly depends on aging. Results after MSCs recellularization showed similar viability and proliferation rate in all conditions. Discussion: This data strongly suggests that biomechanical measurements, especially in aging models, should be carried out in physiomimetic conditions rather than following the conventional non-inflated lung (RV) approach. The use of decellularized lung scaffolds from aged and/or other lung disease murine/human models at physiomimetic conditions will help to better understand the potential role of mechanotransduction on the susceptibility and progression of chronic lung diseases, lung regeneration and cancer.

Characterization and biocompatibility evaluation of acellular rat skin scaffolds for skin tissue engineering applications

Utilization of acellular scaffolds, extracellular matrix (ECM) without cell content, is growing in tissue engineering, due to their high biocompatibility, bioactivity ad mechanical support. Hence, the purpose of this research was to study the characteristics and biocompatibility of decellularized rat skin scaffolds using the osmotic shock method. First, the skin of male Wistar rats was harvested and cut into 1 × 1 cm2 pieces. Then, some of the harvested parts were subjected to the decellularization process by applying osmotic shock. Comparison of control and scaffold samples was conducted in order to assure cell elimination and ECM conservation by means of histological evaluations, quantification of biochemical factors, measurement of DNA amount, and photographing the ultrastructure of the samples by scanning electron microscopy (SEM). In order to evaluate stem cell viability and adhesion to the scaffold, adipose-derived mesenchymal stem cells (AD-MSCs) were seeded on the acellular scaffolds. Subsequently, MTT test and SEM imaging of the scaffolds containing cultured cells were applied. The findings indicated that in the decellularized scaffolds prepared by osmotic shock method, not only the cell content was removed, but also the ECM components and its ultrastructure were preserved. Also, the 99% viability and adhesion of AD-MSCs cultured on the scaffolds indicate the biocompatibility of the decellularized skin scaffold. In conclusion, decellularized rat skin scaffolds are biocompatible and appropriate scaffolds for future investigations of tissue engineering applications.

Biomedical Application of Decellularized Scaffolds

Tissue loss and end-stage organ failure are serious health problems across the world. Natural and synthetic polymer scaffold material based artificial organs play an important role in the field of tissue engineering and organ regeneration, but they are not from the body and may cause side effects such as rejection. In recent years, the biomimetic decellularized scaffold based materials have drawn great attention in the tissue engineering field for their good biocompatibility, easy modification, and excellent organism adaptability. Therefore, in this review, we comprehensively summarize the application of decellularized scaffolds in tissue engineering and biomedicine in recent years. The preparation methods, modification strategies, construction of artificial tissues, and application in biomedical applications are discussed. We hope that this review will provide a useful reference for research on decellularized scaffolds and promote their application tissue engineering.

Detergent-Based Decellularization for Anisotropic Cardiac-Specific Extracellular Matrix Scaffold Generation

Cell-derived extracellular matrix (ECM) has become increasingly popular in tissue engineering applications due to its ability to provide tailored signals for desirable cellular responses. Anisotropic cardiac-specific ECM scaffold decellularized from human induced pluripotent stem cell (hiPSC)-derived cardiac fibroblasts (hiPSC-CFs) mimics the native cardiac microenvironment and provides essential biochemical and signaling cues to hiPSC-derived cardiomyocytes (hiPSC-CMs). The objective of this study was to assess the efficacy of two detergent-based decellularization methods: (1) a combination of ethylenediaminetetraacetic acid and sodium dodecyl sulfate (EDTA + SDS) and (2) a combination of sodium deoxycholate and deoxyribonuclease (SD + DNase), in preserving the composition and bioactive substances within the aligned ECM scaffold while maximumly removing cellular components. The decellularization effects were evaluated by characterizing the ECM morphology, quantifying key structural biomacromolecules, and measuring preserved growth factors. Results showed that both treatments met the standard of cell removal (less than 50 ng/mg ECM dry weight) and substantially preserved major ECM biomacromolecules and growth factors. The EDTA + SDS treatment was more time-efficient and has been determined to be a more efficient method for generating an anisotropic ECM scaffold from aligned hiPSC-CFs. Moreover, this cardiac-specific ECM has demonstrated effectiveness in supporting the alignment of hiPSC-CMs and their expression of mature structural and functional proteins in in vitro cultures, which is crucial for cardiac tissue engineering.

Cryosectioning of Hydrogels as a Reliable Approach to Increase Yield and Further Tune Mechanical Properties

Decellularized extracellular matrix (dECM) hydrogels have emerged as promising materials in tissue engineering. The steps to produce dECM hydrogels containing the bioactive epitopes found in the native matrix are often laborious, including the initial harvesting and decellularization of the animal organ. Furthermore, resulting hydrogels often exhibit weak mechanical properties that require the use of additional crosslinkers such as genipin to truly simulate the mechanical properties of the desired study tissue. In this work, we have developed a protocol to readily obtain tens of thin dECM hydrogel cryosections attached to a glass slide as support, to serve as scaffolds for two-dimensional (2D) or three-dimensional (3D) cell culture. Following extensive atomic force microscopy (AFM)-based mechanical characterization of dECM hydrogels crosslinked with increasing genipin concentrations (5 mM, 10 mM, and 20 mM), we provide detailed protocol recommendations for achieving dECM hydrogels of any biologically relevant stiffness. Given that our protocol requires hydrogel freezing, we also confirm that the approach taken can be further used to increase the mechanical properties of the scaffold in a controlled manner exhibiting twice the stiffness in highly crosslinked arrays. Finally, we explored the effect of ethanol-based short- and long-term sterilization on dECM hydrogels, showing that in some situations it may give rise to significant changes in hydrogel mechanical properties that need to be taken into account in experimental design. The hydrogel cryosections produced were shown to be biocompatible and support cell attachment and spreading for at least 72 h in culture. In brief, our proposed method may provide several advantages for tissue engineering: (1) easy availability and reduction in preparation time, (2) increase in the total hydrogel volume eventually used for experiments being able to obtain 15-22 slides from a 250 µL hydrogel) with a (3) reduction in scaffold variability (only a 17.5 ± 9.5% intraslide variability provided by the method), and (4) compatibility with live-cell imaging techniques or further cell characterization of cells.

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.

Decellularization of Dense Regular Connective Tissue-Cellular and Molecular Modification with Applications in Regenerative Medicine

Healing of dense regular connective tissue, due to a high fiber-to-cell ratio and low metabolic activity and regeneration potential, frequently requires surgical implantation or reconstruction with high risk of reinjury. An alternative to synthetic implants is using bioscaffolds obtained through decellularization, a process where the aim is to extract cells from the tissue while preserving the tissue-specific native molecular structure of the ECM. Proteins, lipids, nucleic acids and other various extracellular molecules are largely involved in differentiation, proliferation, vascularization and collagen fibers deposit, making them the crucial processes in tissue regeneration. Because of the multiple possible forms of cell extraction, there is no standardized protocol in dense regular connective tissue (DRCT). Many modifications of the structure, shape and composition of the bioscaffold have also been described to improve the therapeutic result following the implantation of decellularized connective tissue. The available data provide a valuable source of crucial information. However, the wide spectrum of decellularization makes it important to understand the key aspects of bioscaffolds relative to their potential use in tissue regeneration.

Intravital tumor decellularization as a new approach to cancer treatment

This study demonstrates the possibility of tumor decellularization in living animals. Subcutaneous Ehrlich tumor induced by isolated Ehrlich ascitic carcinoma cells in mice was used as a model. The study also presents methods for ex vivo decellularization of human gastric adenocarcinoma (HGA) and hepatocellular carcinoma (HCC) induced by diethylnitrosamine (DEN) in rat. Sodium dodecyl sulfate (SDS) and Triton X-100 were used as detergents for tumor decellularization. The detergents for HGA and HCC were administered through organ vessels. For intravital decellularization of Ehrlich's subcutaneous tumor, detergents were injected directly into the tumor parenchyma. The results of the study showed that the effectiveness of tumor decellularization using SDS and Triton X-100 depended on the size, structure, stiffness and density of the tumor, as well as on the concentration, route and speed of detergent administration. The study also showed that an hour after the initiation of decellularization, the central part of Ehrlich's tumor changed the color, and after three hours, it completely acquired a translucent white color. Chemical contamination of tissues surrounding the tumor with the detergents was not observed. Histological studies showed the complete absence of all cellular components of Ehrlich's tumor and a slightly deformed extracellular matrix (ECM). There were no loco-regional recurrences or metastases of Ehrlich's tumor within 150 days after decellularization. The developed intravital decellularization method allows the effective removal of the cellular components and the DNA content of Ehrlich's subcutaneous tumor without compromising animal health. Additionally, this method can destroy tumor ECM, which will significantly improve the delivery of anticancer drugs to the tumor cells. However, more detailed and extensive studies are needed to develop an in vivo technique for isolated decellularization of the tumor or a part of the organ with the tumor. It is also necessary to identify less toxic decellularization agents and to develop the most efficient route for their delivery to the tumor cells.

A novel allogeneic acellular matrix scaffold for porcine cartilage regeneration

BACKGROUND

Cartilage defects are common sports injuries without significant treatment. Articular cartilage with inferior regenerative potential resulted in the poor formation of hyaline cartilage in defects. Acellular matrix scaffolds provide a microenvironment and biochemical properties similar to those of native tissues and are widely used for tissue regeneration. Therefore, we aimed to design a novel acellular cartilage matrix scaffold (ACS) for cartilage regeneration and hyaline-like cartilage formation.

METHODS

Four types of cartilage injury models, including full-thickness cartilage defects (6.5 and 8.5 mm in diameter and 2.5 mm in depth) and osteochondral defects (6.5 and 8.5 mm in diameter and 5 mm in depth), were constructed in the trochlear groove of the right femurs of pigs (n = 32, female, 25-40 kg). The pigs were divided into 8 groups (4 in each group) based on post-surgery treatment differences. was assessed by macroscopic appearance, magnetic resonance imaging (MRI), micro-computed tomography (micro-CT), and histologic and immunohistochemistry tests.

RESULTS

At 6 months, the ACS-implanted group exhibited better defect filling and a greater number of chondrocyte-like cells in the defect area than the blank groups. MRI and micro-CT imaging evaluations revealed that ACS implantation was an effective treatment for cartilage regeneration. The immunohistochemistry results suggested that more hyaline-like cartilage was generated in the defects of the ACS-implanted group.

CONCLUSIONS

ACS implantation promoted cartilage repair in full-thickness cartilage defects and osteochondral defects with increased hyaline-like cartilage formation at the 6-month follow-up.

Partial Decellularization as a Method to Improve the Biocompatibility of Heart Tissue Implants

Increasing the biocompatibility of some biological implants through tissue engineering is important for regenerative medicine, which recently has a rapid development dynamic. In this study we used tree different washing protocols, respectively with Sodium Lauryl Sulfate (SLS), with Sodium Deoxycholate (SD), and with saline (Sa) to achieve partial decellularization of 2-3mm thick cross-sections through Wistar rat hearts. Pieces of the heart tissue were either histologically analyzed to evaluate the decellularization processes or implanted for 5 days on 9-day-old chick embryo chorioallantoic membrane (CAM) and then histologically analyzed to evaluate CAM-implant interactions. Histological analysis of SLS or SD washed tissues showed different microscopic features of the decellularization processes, SLS-washing leading to the formation of a completely decellularized ECM layer at the periphery of the heart tissue. Both detergents induced changes in the spatial arrangement of collagen fibers of the heart tissue. Histological analysis of the CAM implants shoved that the peripheral zone with complete decellularization induced by SLS increased the biocompatibility of heart tissue implants by favoring neovascularization and cell migration. These results suggested that the biocompatibility of the heart tissue implant can be modulated by the appropriate use of a SLS-based decellularization protocol.

Pipeline for precise insoluble matrisome coverage in tissue extracellular matrices

The extracellular matrix (ECM) is assembled by hundreds of proteins orchestrating tissue patterning and surrounding cell fates via the mechanical-biochemical feedback loop. Aberrant ECM protein production or assembly usually creates pathological niches eliciting lesions that mainly involve fibrogenesis and carcinogenesis. Yet, our current knowledge about the pathophysiological ECM compositions and alterations in healthy or diseased tissues is limited since the methodology for precise insoluble matrisome coverage in the ECM is a "bottleneck." Our current study proposes an enhanced sodium dodecyl sulfonate (E-SDS) workflow for thorough tissue decellularization and an intact pipeline for the accurate identification and quantification of highly insoluble ECM matrisome proteins. We tested this pipeline in nine mouse organs and highlighted the full landscape of insoluble matrisome proteins in the decellularized ECM (dECM) scaffolds. Typical experimental validations and mass spectrometry (MS) analysis confirmed very little contamination of cellular debris remaining in the dECM scaffolds. Our current study will provide a low-cost, simple, reliable, and effective pipeline for tissue insoluble matrisome analysis in the quest to comprehend ECM discovery proteomic studies.

Lung Micrometastases Display ECM Depletion and Softening While Macrometastases Are 30-Fold Stiffer and Enriched in Fibronectin

Mechanical changes in tumors have long been linked to increased malignancy and therapy resistance and attributed to mechanical changes in the tumor extracellular matrix (ECM). However, to the best of our knowledge, there have been no mechanical studies on decellularized tumors. Here, we studied the biochemical and mechanical progression of the tumor ECM in two models of lung metastases: lung carcinoma (CAR) and melanoma (MEL). We decellularized the metastatic lung sections, measured the micromechanics of the tumor ECM, and stained the sections for ECM proteins, proliferation, and cell death markers. The same methodology was applied to MEL mice treated with the clinically approved anti-fibrotic drug nintedanib. When compared to healthy ECM (~0.40 kPa), CAR and MEL lung macrometastases produced a highly dense and stiff ECM (1.79 ± 1.32 kPa, CAR and 6.39 ± 3.37 kPa, MEL). Fibronectin was overexpressed from the early stages (~118%) to developed macrometastases (~260%) in both models. Surprisingly, nintedanib caused a 4-fold increase in ECM-occupied tumor area (5.1 ± 1.6% to 18.6 ± 8.9%) and a 2-fold in-crease in ECM stiffness (6.39 ± 3.37 kPa to 12.35 ± 5.74 kPa). This increase in stiffness strongly correlated with an increase in necrosis, which reveals a potential link between tumor hypoxia and ECM deposition and stiffness. Our findings highlight fibronectin and tumor ECM mechanics as attractive targets in cancer therapy and support the need to identify new anti-fibrotic drugs to abrogate aberrant ECM mechanics in metastases.

Multi-Step Extracellular Matrix Remodelling and Stiffening in the Development of Idiopathic Pulmonary Fibrosis

The extracellular matrix (ECM) of the lung is a filamentous network composed mainly of collagens, elastin, and proteoglycans that provides structural and physical support to its populating cells. Proliferation, migration and overall behaviour of those cells is greatly determined by micromechanical queues provided by the ECM. Lung fibrosis displays an aberrant increased deposition of ECM which likely changes filament organization and stiffens the ECM, thus upregulating the profibrotic profile of pulmonary cells. We have previously used AFM to assess changes in the Young's Modulus (E) of the ECM in the lung. Here, we perform further ECM topographical, mechanical and viscoelastic analysis at the micro- and nano-scale throughout fibrosis development. Furthermore, we provide nanoscale correlations between topographical and elastic properties of the ECM fibres. Firstly, we identify a softening of the ECM after rats are instilled with media associated with recovery of mechanical homeostasis, which is hindered in bleomycin-instilled lungs. Moreover, we find opposite correlations between fibre stiffness and roughness in PBS- vs bleomycin-treated lung. Our findings suggest that changes in ECM nanoscale organization take place at different stages of fibrosis, with the potential to help identify pharmacological targets to hinder its progression.

A novel approach for the endothelialization of xenogeneic decellularized vascular tissues by human cells utilizing surface modification and dynamic culture

Decellularized xenogeneic vascular grafts can be used in revascularization surgeries. We have developed decellularization methods using high hydrostatic pressure (HHP), which preserves the extracellular structure. Here, we attempted ex vivo endothelialization of HHP-decellularized xenogeneic tissues using human endothelial cells (ECs) to prevent clot formation against human blood. Slices of porcine aortic endothelium were decellularized using HHP and coated with gelatin. Human umbilical vein ECs were directly seeded and cultured under dynamic flow or static conditions for 14 days. Dynamic flow cultures tend to demonstrate higher cell coverage. We then coated the tissues with the E8 fragment of human laminin-411 (hL411), which has high affinity for ECs, and found that Dynamic/hL411showed high area coverage, almost reaching 100% (Dynamic/Gelatin vs Dynamic/hL411; 58.7 ± 11.4 vs 97.5 ± 1.9%, P = 0.0017). Immunostaining revealed sufficient endothelial cell coverage as a single cell layer in Dynamic/hL411. A clot formation assay using human whole blood showed low clot formation in Dynamic/hL411, almost similar to that in the negative control, polytetrafluoroethylene. Surface modification of HHP-decellularized xenogeneic endothelial tissues combined with dynamic culture achieved sufficient ex vivo endothelialization along with prevention of clot formation, indicating their potential for clinical use as vascular grafts in the future.

A Fast and Efficient Decellularization Method for Tissue Slices

The study and use of decellularized extracellular matrix (dECM) in tissue engineering, regenerative medicine, and pathophysiology have become more prevalent in recent years. To obtain dECM, numerous decellularization procedures have been developed for the entire organ or tissue blocks, employing either perfusion of decellularizing agents through the tissue's vessels or submersion of large sections in decellularizing solutions. However, none of these protocols are suitable for thin tissue slices (less than 100 µm) or allow side-by-side analysis of native and dECM consecutive tissue slices. Here, we present a detailed protocol to decellularize tissue sections while maintaining the sample attached to a glass slide. This protocol consists of consecutive washes and incubations of simple decellularizing agents: ultrapure water, sodium deoxycholate (SD) 2%, and deoxyribonuclease I solution 0.3 mg/mL (DNase I). This novel method has been optimized for a faster decellularization time (2-3 h) and a better correlation between dECM properties and native tissue-specific biomarkers, and has been tested in different types of tissues and species, obtaining similar results. Furthermore, this method can be used for scarce and valuable samples such as clinical biopsies. This protocol was validated in: Front Bioeng Biotechnol (2022), DOI: 10.3389/fbioe.2022.832178.