Role of the extracellular matrix in morphogenesis

Perspectives on Synthetic Materials to Guide Tissue Regeneration for Osteochondral Defect Repair

Regenerative engineering holds the potential to treat clinically pervasive osteochondral defects (OCDs). In a synthetic materials-guided approach, the scaffold's chemical and physical properties alone instruct cellular behavior in order to effect regeneration, referred to herein as "instructive" properties. While this alleviates the costs and off-target risks associated with exogenous growth factors, the scaffold must be potently instructive to achieve tissue growth. Moreover, toward achieving functionality, such a scaffold should also recapitulate the spatial complexity of the osteochondral tissues. Thus, in addition to the regeneration of the articular cartilage and underlying cancellous bone, the complex osteochondral interface, composed of calcified cartilage and subchondral bone, should also be restored. In this Perspective, we highlight recent synthetic-based, instructive osteochondral scaffolds that have leveraged new material chemistries as well as innovative fabrication strategies. In particular, scaffolds with spatially complex chemical and morphological features have been prepared with electrospinning, solvent-casting-particulate-leaching, freeze-drying, and additive manufacturing. While few synthetic scaffolds have advanced to clinical studies to treat OCDs, these recent efforts point to the promising use of the chemical and physical properties of synthetic materials for regeneration of osteochondral tissues.

Fabrication and Plasma Surface Activation of Aligned Electrospun PLGA Fiber Fleeces with Improved Adhesion and Infiltration of Amniotic Epithelial Stem Cells Maintaining their Teno-inductive Potential

Electrospun PLGA microfibers with adequate intrinsic physical features (fiber alignment and diameter) have been shown to boost teno-differentiation and may represent a promising solution for tendon tissue engineering. However, the hydrophobic properties of PLGA may be adjusted through specific treatments to improve cell biodisponibility. In this study, electrospun PLGA with highly aligned microfibers were cold atmospheric plasma (CAP)-treated by varying the treatment exposure time (30, 60, and 90 s) and the working distance (1.3 and 1.7 cm) and characterized by their physicochemical, mechanical and bioactive properties on ovine amniotic epithelial cells (oAECs). CAP improved the hydrophilic properties of the treated materials due to the incorporation of new oxygen polar functionalities on the microfibers' surface especially when increasing treatment exposure time and lowering working distance. The mechanical properties, though, were affected by the treatment exposure time where the optimum performance was obtained after 60 s. Furthermore, CAP treatment did not alter oAECs' biocompatibility and improved cell adhesion and infiltration onto the microfibers especially those treated from a distance of 1.3 cm. Moreover, teno-inductive potential of highly aligned PLGA electrospun microfibers was maintained. Indeed, cells cultured onto the untreated and CAP treated microfibers differentiated towards the tenogenic lineage expressing tenomodulin, a mature tendon marker, in their cytoplasm. In conclusion, CAP treatment on PLGA microfibers conducted at 1.3 cm working distance represent the optimum conditions to activate PLGA surface by improving their hydrophilicity and cell bio-responsiveness. Since for tendon tissue engineering purposes, both high cell adhesion and mechanical parameters are crucial, PLGA treated for 60 s at 1.3 cm was identified as the optimal construct.

A Bibliometric Review of Artificial Extracellular Matrices Based on Tissue Engineering Technology Literature: 1990 through 2019

Artificial extracellular matrices (aECMs) are an extension of biomaterials that were developed as in-vitro model environments for tissue cells that mimic the native in vivo target tissues’ structure. This bibliometric analysis evaluated the research productivity regarding aECM based on tissue engineering technology. The Web of Science citation index was examined for articles published from 1990 through 2019 using three distinct aECM-related topic sets. Data were also visualized using network analyses (VOSviewer). Terms related to in-vitro, scaffolds, collagen, hydrogels, and differentiation were reoccurring in the aECM-related literature over time. Publications with terms related to a clinical direction (wound healing, stem cells, artificial skin, in-vivo, and bone regeneration) have steadily increased, as have the number of countries and institutions involved in the artificial extracellular matrix. As progress with 3D scaffolds continues to advance, it will become the most promising technology to provide a therapeutic option to repair or replace damaged tissue.

Cell-derived matrices (CDM)-Methods, challenges and applications

Extracellular matrix (ECM) provides both physical support and bioactive signals such as growth factors and cytokines to cells at their microenvironment or niche. Engineering the matrix niche becomes an important approach to study or manipulate cellular fate. This work presents an overview on the reconstitution of the ECM niche through a wide range of approaches ranging from coating culture dish with ECM molecules to decellularization of native tissues. In particular, we focused on reconstituting the complex ECM niche through cell-derived matrix (CDM) by reviewing the methodological approaches used in our group to derive ECM from mature cells such as chondrocytes and nucleus pulposus cells (NPCs), undifferentiated stem cells such as mesenchymal stem cells (MSCs), as well as MSCs undergoing chondrogenic and osteogenic differentiation, in 2D or 3D models. Specific attention has also been given to key factors that should be considered in various applications and challenges in relation to the CDM. Last but not the least, a few future perspectives and their significance have been proposed.

Adjustable and Versatile 3D Tumor Spheroid Culture Platform with Interfacial Elastomeric Wells

Three-dimensional (3D) cell culture platforms have recently received a great deal of attention, as these systems are able to recapitulate the in vivo microenvironment of tissues or tumors. Herein, we describe adjustable and versatile elastomeric well structures for spheroid formation and their use for in situ analyses as a tunable 3D cell culture platform. Elastomeric spherical wells are fabricated using a one-step interfacial reaction between aqueous droplets on immiscible liquid polydimethylsiloxane (PDMS) without any template or expensive equipment. Because of their differing surface tensions, spherical wells are spontaneously formed on liquid PDMS with various sizes and curvatures that are easily controlled. Using arrays of these optimized wells, single tumor spheroids within each well were successfully formed at high efficiency (up to 97%) by coculturing tumor cells and fibroblasts to reflect the complex microenvironment of cancer tissue. Moreover, the tumor spheroids formed within the interfacial wells were directly applied for observing drug responses and monitoring reactive oxygen species (ROS) to investigate tumor cell responses to drugs or their 3D microenvironment. We believe that our proposed platform provides a significant contribution to the multimodal analyses of anticancer therapeutics and the tumor microenvironment.

A Comparison of Osteoblast and Osteoclast In Vitro Co-Culture Models and Their Translation for Preclinical Drug Testing Applications

As the population of western societies on average ages, the number of people affected by bone remodeling-associated diseases such as osteoporosis continues to increase. The development of new therapeutics is hampered by the high failure rates of drug candidates during clinical testing, which is in part due to the poor predictive character of animal models during preclinical drug testing. Co-culture models of osteoblasts and osteoclasts offer an alternative to animal testing and are considered to have the potential to improve drug development processes in the future. However, a robust, scalable, and reproducible 3D model combining osteoblasts and osteoclasts for preclinical drug testing purposes has not been developed to date. Here we review various types of osteoblast-osteoclast co-culture models and outline the remaining obstacles that must be overcome for their successful translation.

Influence of substrate stiffness on human induced pluripotent stem cells: preliminary results

Skeletal muscle differentiation was proven to be influenced by changes in the substrate stiffness. However, a lack of knowledge features this field, concerning skeletal muscle tissues obtained from human induced pluripotent stem cells. Here we report the fabrication of polydimethylsiloxane-based substrates in a range of stiffness values from 3.5 to 141 kPa and the response of human induced pluripotent stem cells cultured on them for 5 days. The substrates were able to sustain cell adhesion and proliferation throughout the whole period. An inversely proportional relationship (although not significant) was found between the proliferation rate and the substrate stiffness. Initial analyses of iPSCs skeletal muscle differentiation shown no influences on markers of the early stages. These results lay the foundations for further studies on the influence of extrinsic mechanical stimuli on induced pluripotent stem cells-derived skeletal muscle tissues.

A 3D approach to reproduction

For over a century, 2D cell culture has been extensively used for all the different research fields. However, this in vitro system does not allow to reproduce the natural structures of the original tissue, causing several changes and, in most cases, the loss of cell-to-cell communications and cell-to-extracellular matrix interactions. Based on this, during the last years, novel 3D platforms, able to mimic the in vivo milieu, are being developed. The advantages of the use of 3D models are: the reduction of the gap between cell culture and physiological environment; imitation of the specific architecture; partially maintenance of the mechanical and biochemical cues of the original tissue. Currently, 3D systems are used in a broad range of studies, including the field of reproduction, where they have been applied to promote maturation of follicles and oocytes and embryo culture. Here, we review 2D and 3D cell culture methods, discussing advantages and limitations of these techniques. We report the fundamental mechanisms involved in cell ability to perceive and respond to mechanical cues and their role in transmitting signals to and between cells and in regulating intracellular signaling pathways. In particular, we focus on the main effectors of the Hippo pathway, Yes-associated protein (YAP) and WW domain-containing transcription regulator protein 1 (TAZ), describing their behavior and function in oocytes and embryos. Lastly, we provide an overall perspective of the most recent 3D technologies developed in the field of reproduction, describing how their use may revolutionize the understanding of cellular behavior and provide novel tools, useful in reproductive technologies and livestock production.

Extracellular matrix decorated polycaprolactone scaffolds for improved mesenchymal stem/stromal cell osteogenesis towards a patient-tailored bone tissue engineering approach

The clinical demand for tissue-engineered bone is growing due to the increase of non-union fractures and delayed healing in an aging population. Herein, we present a method combining additive manufacturing (AM) techniques with cell-derived extracellular matrix (ECM) to generate structurally well-defined bioactive scaffolds for bone tissue engineering (BTE). In this work, highly porous three-dimensional polycaprolactone (PCL) scaffolds with desired size and architecture were fabricated by fused deposition modeling and subsequently decorated with human mesenchymal stem/stromal cell (MSC)-derived ECM produced in situ. The successful deposition of MSC-derived ECM onto PCL scaffolds (PCL-MSC ECM) was confirmed after decellularization using scanning electron microscopy, elemental analysis, and immunofluorescence. The presence of cell-derived ECM within the PCL scaffolds significantly enhanced MSC attachment and proliferation, with and without osteogenic supplementation. Additionally, under osteogenic induction, PCL-MSC ECM scaffolds promoted significantly higher calcium deposition and elevated relative expression of bone-specific genes, particularly the gene encoding osteopontin, when compared to pristine scaffolds. Overall, our results demonstrated the favorable effects of combining MSC-derived ECM and AM-based scaffolds on the osteogenic differentiation of MSC, resulting from a closer mimicry of the native bone niche. This strategy is highly promising for the development of novel personalized BTE approaches enabling the fabrication of patient defect-tailored scaffolds with enhanced biological performance and osteoinductive properties.

Injectable microfluidic hydrogel microspheres based on chitosan and poly(ethylene glycol) diacrylate (PEGDA) as chondrocyte carriers

Chitosan/PEGDA double-network hydrogel microspheres prepared by microfluidic method as chondrocyte carriers for bottom-up cartilage tissue engineering.

Traditional and Advanced Cell Cultures in Hematopoietic Stem Cell Studies

Hematopoiesis is the main function of bone marrow. Human hematopoietic stem and progenitor cells reside in the bone marrow microenvironment, making it a hotspot for the development of hematopoietic diseases. Numerous alterations that correspond to disease progression have been identified in the bone marrow stem cell niche. Complex interactions between the bone marrow microenvironment and hematopoietic stem cells determine the balance between the proliferation, differentiation and homeostasis of the stem cell compartment. Changes in this tightly regulated network can provoke malignant transformation. However, our understanding of human hematopoiesis and the associated niche biology remains limited due to accessibility to human material and the limits of in vitro culture models. Traditional culture systems for human hematopoietic studies lack microenvironment niches, spatial marrow gradients, and dense cellularity, rendering them incapable of effectively translating marrow physiology ex vivo. This review will discuss the importance of 2D and 3D culture as a physiologically relevant system for understanding normal and abnormal hematopoiesis.

Multi-modal liquid biopsy platform for cancer screening: screening both cancer-associated rare cells and cancer cell-derived vesicles on the fabric filters for a reliable liquid biopsy analysis

Circulating tumor cells (CTCs) are receiving a great amount of scientific interest as a diagnostic biomarker for various types of cancer. Despite the recent progress in the development of highly sensitive CTC isolation devices, post-capture analysis of CTCs is still hindered by technical challenges associated with their rarity. Herein, we present a multi-modal CTC screening platform which is capable to analyze CTCs and CTC-derived extracellular vesicles (EVs), simultaneously from a single sample. Cytochalasin B (CB) treatment promotes cells to release large number of EVs from their surface, as demonstrated by CB-treated cells (5 µg/mL for 3 h) secreting 3.5-fold more EVs, compared to the non-treated cells. CB further generates 1.7-fold more EVs from the cells captured on our CTC filtration device (the fabric filter), compared to those from the cell culture flasks, owing to its multiple pore structure design which reduces the non-specific binding of EVs. Both CB-treated cancer cells and CB-induced EVs are found to overexpress tumor-associated markers, demonstrating a potential for the development of CTC dual-screening platform. Collectively, the results presented in this study reveal that our multi-modal cancer screening platform can synergistically improve the reliability and efficacy of the current CTC analysis systems.

3D cell culture stimulates the secretion of in vivo like extracellular vesicles

For studying cellular communications ex-vivo, a two-dimensional (2D) cell culture model is currently used as the “gold standard”. 2D culture models are also widely used in the study of RNA expression profiles from tumor cells secreted extracellular vesicles (EVs) for tumor biomarker discovery. Although the 2D culture system is simple and easily accessible, the culture environment is unable to represent in vivo extracellular matrix (ECM) microenvironment. Our study observed that 2D- culture derived EVs showed significantly different profiles in terms of secretion dynamics and essential signaling molecular contents (RNAs and DNAs), when compared to the three-dimensional (3D) culture derived EVs. By performing small RNA next-generation sequencing (NGS) analysis of cervical cancer cells and their EVs compared with cervical cancer patient plasma EV-derived small RNAs, we observed that 3D- culture derived EV small RNAs differ from their parent cell small RNA profile which may indicate a specific sorting process. Most importantly, the 3D- culture derived EV small RNA profile exhibited a much higher similarity (~96%) to in vivo circulating EVs derived from cervical cancer patient plasma. However, 2D- culture derived EV small RNA profile correlated better with only their parent cells cultured in 2D. On the other hand, DNA sequencing analysis suggests that culture and growth conditions do not affect the genomic information carried by EV secretion. This work also suggests that tackling EV molecular alterations secreted into interstitial fluids can provide an alternative, non-invasive approach for investigating 3D tissue behaviors at the molecular precision. This work could serve as a foundation for building precise models employed in mimicking in vivo tissue system with EVs as the molecular indicators or transporters. Such models could be used for investigating tumor biomarkers, drug screening, and understanding tumor progression and metastasis.

Self-Contained Three-Dimensional Bioprinter for Applications in Cardiovascular Research

Bioprinting is a technique of creating 3D cell-laden structures by accurately dispensing biomaterial to form complex synthetic tissue. The printed constructs aim to mimic the native tissue by preserving the cell functionality and viability within the printed structure. The 3D bioprinting system presented in this paper aims to facilitate the process of 3D bioprinting through its ability to control the environmental parameters within an enclosed printing chamber. This design of the bioprinter targets to eliminate the need for a laminar flow hood, by regulating the necessary environmental conditions important for cell survival, especially during long duration prints. A syringe-based extrusion (SBE) deposition method comprising multiple nozzles is integrated into the system. This allows for a wider selection of biomaterials that can be used for the formation of the extracellular matrix (ECM). Tissue constructs composed of alginate-gelatin hydrogels were mixed with fibrinogen and human endothelial cells which were then characterized and compared using two methodologies: casted and bioprinted. Furthermore, vasculature was incorporated in the bioprinted constructs using sacrificial printing. Structural and functional characterization of the constructs were performed by assessing rheological, mechanical properties, and analyzing live-dead assay measurements.

Hydrogels for Liver Tissue Engineering

Bioengineered livers are promising in vitro models for drug testing, toxicological studies, and as disease models, and might in the future be an alternative for donor organs to treat end-stage liver diseases. Liver tissue engineering (LTE) aims to construct liver models that are physiologically relevant. To make bioengineered livers, the two most important ingredients are hepatic cells and supportive materials such as hydrogels. In the past decades, dozens of hydrogels have been developed to act as supportive materials, and some have been used for in vitro models and formed functional liver constructs. However, currently none of the used hydrogels are suitable for in vivo transplantation. Here, the histology of the human liver and its relationship with LTE is introduced. After that, significant characteristics of hydrogels are described focusing on LTE. Then, both natural and synthetic materials utilized in hydrogels for LTE are reviewed individually. Finally, a conclusion is drawn on a comparison of the different hydrogels and their characteristics and ideal hydrogels are proposed to promote LTE.

Laminin-derived peptide C16 regulates Tks expression and reactive oxygen species generation in human prostate cancer cells

Laminin peptides influence cancer biology. We investigated the role of a laminin-derived peptide C16 regulating invadopodia molecules in human prostate cancer cells (DU145). C16 augmented invadopodia activity of DU145 cells, and stimulated expression Tks4, Tks5, cortactin, and membrane-type matrix metalloproteinase 1. Reactive oxygen species generation is also related to invadopodia formation. This prompted us to address whether C16 would induce reactive oxygen species generation in DU145 cells. Quantitative fluorescence and flow cytometry showed that the peptide C16 increased reactive oxygen species in DU145 cells. Furthermore, significant colocalization between Tks5 and reactive oxygen species was observed in C16-treated cells. Results suggested that the peptide C16 increased Tks5 and reactive oxygen species in prostate cancer cells. The role of C16 increasing Tks and reactive oxygen species are novel findings on invadopodia activity.

Carboxymethyl kappa carrageenan-modified decellularized small-diameter vascular grafts improving thromboresistance properties

The development of decellularized small-diameter vascular grafts is a potential solution for patients requiring vascular reconstructive procedures. However, there is a limitation for acellular scaffolds due to incomplete recellularization and exposure of extracellular matrix components to whole blood resulting in platelet adhesion. To address this issue, a perfusion decellularization method was developed using a custom-designed set up which completely removed cell nuclei and preserved three-dimensional structure and mechanical properties of native tissue (sheep carotid arteries). Afterwards, carboxymethyl kappa carrageenan (CKC) was introduced as a novel anticoagulant in vascular tissue engineering which can inhibit thrombosis formation. The method enabled uniform immobilization of CKC on decellularized arteries as a result of interaction between amine functional groups of decellularized arteries and carboxyl groups of CKC. The CKC modified graft significantly reduced platelet adhesion from 44.53 ± 2.05% (control) to 19.57 ± 1.37% (modified) and supported endothelial cells viability, proliferation, and nitric oxide production. Overall, the novel CKC modified scaffold provides a promising solution for thrombosis formation of small-diameter vessels and could be a potent graft for future in vivo applications in vascular bypass procedures. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1690-1701, 2019.

Spatial control of oxygen delivery to three-dimensional cultures alters cancer cell growth and gene expression

Commonly used monolayer cancer cell cultures fail to provide a physiologically relevant environment in terms of oxygen delivery. Here, we describe a three-dimensional (3D) bioreactor system where cancer cells are grown in Matrigel in modified six-well plates. Oxygen is delivered to the cultures through a polydimethylsiloxane (PDMS) membrane at the bottom of the wells, with microfabricated PDMS pillars to control oxygen delivery. The plates receive 3% oxygen from below and 0% oxygen at the top surface of the media, providing a gradient of 3-0% oxygen. We compared growth and transcriptional profiles for cancer cells grown in Matrigel in the bioreactor, 3D cultures grown in 21% oxygen, and cells grown in a standard hypoxia chamber at 3% oxygen. Additionally, we compared gene expression of conventional two-dimensional monolayer culture and 3D Matrigel culture in 21% oxygen. We conclude that controlled oxygen delivery may provide a more physiologically relevant 3D system.

Human Organoids Share Structural and Genetic Features with Primary Pancreatic Adenocarcinoma Tumors

Patient-derived pancreatic ductal adenocarcinoma (PDAC) organoid systems show great promise for understanding the biological underpinnings of disease and advancing therapeutic precision medicine. Despite the increased use of organoids, the fidelity of molecular features, genetic heterogeneity, and drug response to the tumor of origin remain important unanswered questions limiting their utility. To address this gap in knowledge, primary tumor- and patient-derived xenograft (PDX)-derived organoids, and 2D cultures for in-depth genomic and histopathologic comparisons with the primary tumor were created. Histopathologic features and PDAC representative protein markers (e.g., claudin 4 and CA19-9) showed strong concordance. DNA- and RNA-sequencing (RNAseq) of single organoids revealed patient-specific genomic and transcriptomic consistency. Single-cell RNAseq demonstrated that organoids are primarily a clonal population. In drug response assays, organoids displayed patient-specific sensitivities. In addition, the in vivo PDX response to FOLFIRINOX and gemcitabine/abraxane treatments were examined, which was recapitulated in vitro with organoids. This study has demonstrated that organoids are potentially invaluable for precision medicine as well as preclinical drug treatment studies because they maintain distinct patient phenotypes and respond differently to drug combinations and dosage. IMPLICATIONS: The patient-specific molecular and histopathologic fidelity of organoids indicate that they can be used to understand the etiology of the patient's tumor and the differential response to therapies and suggests utility for predicting drug responses.

Human Organotypic Respiratory Models

Biomedical research aiming to understand the molecular basis of human lung tissue development, homeostasis and disease, or to develop new therapies for human respiratory diseases, requires models that faithfully recapitulate the human condition. This has stimulated biologists and engineers to develop in vitro organotypic models mimicking human respiratory tissues. In this chapter, we provide examples of different types of model systems ranging from simple unicellular cultures to more complex multicellular systems. The models contain, in varying degree, cell types present in real tissue in combination with different extracellular matrix components that can critically affect cell phenotype and function. We also describe how organotypic respiratory models can be combined with human innate immune cells, to better recapitulate tissue inflammation, a key component in, for example, infectious diseases. These models have the potential to provide new insights into lung physiology, tissue infection and inflammation, disease mechanisms, as well as provide a platform for identification of novel targets and screening of candidate drugs in human lung disorders.

Three-Dimensional Magnetic Levitation Culture System Simulating White Adipose Tissue

White adipose tissue (WAT) has attracted interest for tissue engineering and cell-based therapies as an abundant source of adipose stem/stromal cells (ASC). However, technical challenges in WAT cell culture have limited its applications in regenerative medicine. Traditional two-dimensional (2D) cell culture models, which are essentially monolayers of cells on glass or plastic substrates, inadequately represent tissue architecture, biochemical concentration gradients, substrate stiffness, and most importantly for WAT research, cell phenotypic heterogeneity. Physiological cell culture platforms for WAT modeling must recapitulate the native diversity of cell types and their coordination within the organ. For this purpose, we developed a three-dimensional (3D) model using magnetic levitation. Here, we describe our protocol that we successfully employed to build adipose tissue organoids (adipospheres) that preserve the heterogeneity of the constituent cell types in vitro. We demonstrate the capacity of assembling adipospheres from multiple cell types, including ASCs, endohtelial cells, and leukocytes that recreate tissue organization. These adipospheres mimicked WAT organogenesis in that they enabled the formation of vessel-like endothelial structures with lumens and differentiation of unilocular adipocytes. Altogether, magnetic levitation is a cell culture platform that recreates tissue structure, function, and heterogeneity in vitro, and serves as a foundation for high-throughput WAT tissue culture and analysis.

Novel Models to Study Stromal Cell-Leukocyte Interactions in Health and Disease

To study human immunology in general and stromal immunology in particular, it is highly motivated to move from monolayers to 3D cultures, such as organotypic models, that better mimic the function of living tissue. These models can potentially contain most if not all cell types present in tissues, in combination with different extracellular matrix components that can critically affect cell phenotype. Besides their well-established use in studies of tissue-specific cells, such as epithelial cells, endothelial cells and stromal fibroblasts in combination with extracellular components, these models have also been shown to be valuable to study how tissue participates in the regulation of leukocyte differentiation and function. Organotypic models with leukocytes represent novel powerful tools to study human stromal immunology and mechanisms involved in the regulation of leukocyte functions and inflammatory processes in human health and disease. In particular, these models are robust, long-lived and reproducible and allow monitoring of disease progression in real time, as well as the mixing of cellular constituents from healthy and pathological tissues. These models are also easy to manipulate, either genetically or by adding external stimulants, such as cytokines and pathogens, to mimic pathological conditions. It is thus not surprising that these models are proposed to be useful in toxicology screening assays, evaluating therapeutic efficacy of drugs and antibiotics, as well as in personalized medicine. Within this chapter, the most recent developments in creating organotypic models for the purpose of study of human leukocyte and stromal cell interactions, in health and disease, will be discussed, in particular focusing on live imaging. Special emphasis will be given on an organotypic model resembling human lung and its usefulness in studying the fine control of physiological and pathological processes in human health and disease. Using these models in studies on human stromal cell and leukocyte interactions will likely help identifying novel disease traits and may point out new potential targets to monitor and treat human diseases.

Adipose Tissue Function and Expandability as Determinants of Lipotoxicity and the Metabolic Syndrome

The adipose tissue organ is organised as distinct anatomical depots located all along the body axis and it is constituted of three different types of adipocytes : white, beige and brown which are integrated with vascular, immune, neural and extracellular stroma cells. These distinct adipocytes serve different specialised functions. The main function of white adipocytes is to ensure healthy storage of excess nutrients/energy and its rapid mobilisation to supply the demand of energy imposed by physiological cues in other organs, whereas brown and beige adipocytes are designed for heat production through uncoupling lipid oxidation from energy production. The concert action of the three type of adipocytes/tissues has been reported to ensure an optimal metabolic status in rodents. However, when one or multiple of these adipose depots become dysfunctional as a consequence of sustained lipid/nutrient overload, then insulin resistance and associated metabolic complications ensue. These metabolic alterations negatively affects the adipose tissue functionality and compromises global metabolic homeostasis. Optimising white adipose tissue expandability and its functional metabolic flexibility and/or promoting brown/beige mediated thermogenic activity counteracts obesity and its associated lipotoxic metabolic effects. The development of these therapeutic approaches requires a deep understanding of adipose tissue in all broad aspects. In this chapter we will discuss the characteristics of the different adipose tissue depots with respect to origins and precursors recruitment, plasticity, cellular composition and expandability capacity as well as molecular and metabolic signatures in both physiological and pathophysiological conditions.

Endothelial Cell Culture Under Perfusion On A Polyester-Toner Microfluidic Device

This study presents an inexpensive and easy way to produce a microfluidic device that mimics a blood vessel, serving as a start point for cell culture under perfusion, cardiovascular research, and toxicological studies. Endpoint assays (i.e., MTT reduction and NO assays) were used and revealed that the components making up the microchip, which is made of polyester and toner (PT), did not induce cell death or nitric oxide (NO) production. Applying oxygen plasma and fibronectin improved the adhesion and proliferation endothelial cell along the microchannel. As expected, these treatments showed an increase in vascular endothelial growth factor (VEGF-A) concentration profiles, which is correlated with adherence and cell proliferation, thus promoting endothelialization of the device for neovascularization. Regardless the simplicity of the device, our “vein-on-a-chip” mimetic has a potential to serve as a powerful tool for those that demand a rapid microfabrication method in cell biology or organ-on-a-chip research.

Optimization of Human Myocardium Decellularization Method for the Construction of Implantable Patches

Cardiac tissue engineering by means of synthetic or natural scaffolds combined with stem/progenitor cells is emerging as the response to the unsatisfactory outcome of approaches based solely on the injection of cells. Parenchymal and supporting cells are surrounded, in vivo, by a specialized and tissue-specific microenvironment, consisting mainly of extracellular matrix (ECM) and soluble factors incorporated in the ECM. Since the naturally occurring ECM is the ideal platform for ensuring cell engraftment, survival, proliferation, and differentiation, the acellular native ECM appears by far the most promising and appealing substrate among all biomaterials tested so far. To obtain intact scaffold of human native cardiac ECM while preserving its composition, we compared the decellularized ECM (d-ECM) produced through five different protocols of decellularization (named Pr1, Pr2, Pr3, Pr4, and Pr5) in terms of efficiency of decellularization, composition, and three-dimensional architecture of d-ECM scaffolds and of their suitability for cell repopulation. The decellularization procedures proved substantially different. Specifically, only three, of the five protocols tested, proved effective in producing thoroughly acellular d-ECM. In addition, the d-ECM delivered differed in architecture and composition and, more importantly, in its ability to support engraftment, survival, and differentiation of cardiac primitive cells in vitro.

Regulators of Collagen Fibrillogenesis during Molar Development in the Mouse

Development of mammalian teeth and surrounding tissues includes time-space changes in the extracellular matrix composition and organization. This requires complex control mechanisms to regulate its synthesis and remodeling. Fibril-associated collagens with interrupted triple helices (FACITs) and a group of small leucine-rich proteoglycans (SLRPs) are involved in the regulation of collagen fibrillogenesis. Recently, collagen type XII and collagen type XIV, members of the FACITs family, were found in the peridental mesenchyme contributing to alveolar bone formation. This study was designed to follow temporospatial expression of collagen types XIIa and XIVa in mouse first molar and adjacent tissues from embryonic day 13, when the alveolar bone becomes morphologically apparent around the molar tooth bud, until postnatal day 22, as the posteruption stage. The patterns of decorin, biglycan, and fibromodulin, all members of the SLRPs family and interacting with collagens XIIa and XIVa, were investigated simultaneously. The situation in the tooth was related to what happens in the alveolar bone, and both were compared to the periodontal ligament. The investigation provided a complex localization of the five antigens in soft tissues, the dental pulp, and periodontal ligaments; in the mineralized tissues, predentin/dentin and alveolar bone; and junction between soft and hard tissues. The results illustrated developmentally regulated and tissue-specific changes in the balance of the two FACITs and three SLRPs.

Mechanotransduction and Growth Factor Signalling to Engineer Cellular Microenvironments

Engineering cellular microenvironments involves biochemical factors, the extracellular matrix (ECM) and the interaction with neighbouring cells. This progress report provides a critical overview of key studies that incorporate growth factor (GF) signalling and mechanotransduction into the design of advanced microenvironments. Materials systems have been developed for surface-bound presentation of GFs, either covalently tethered or sequestered through physico-chemical affinity to the matrix, as an alternative to soluble GFs. Furthermore, some materials contain both GF and integrin binding regions and thereby enable synergistic signalling between the two. Mechanotransduction refers to the ability of the cells to sense physical properties of the ECM and to transduce them into biochemical signals. Various aspects of the physics of the ECM, i.e. stiffness, geometry and ligand spacing, as well as time-dependent properties, such as matrix stiffening, degradability, viscoelasticity, surface mobility as well as spatial patterns and gradients of physical cues are discussed. To conclude, various examples illustrate the potential for cooperative signalling of growth factors and the physical properties of the microenvironment for potential applications in regenerative medicine, cancer research and drug testing.

Adipose‑derived stem cells and hyaluronic acid based gel compatibility, studied in vitro

Minimally invasive aesthetic and cosmetic procedures have increased in popularity. Injectable dermal fillers provide soft tissue augmentation, improve facial rejuvenation and wrinkles, and correct tissue defects. To investigate the use of adipose‑derived stem cells integrated with a hyaluronic acid based gel as a dermal filler, the present study used cytotoxicity studies, proliferation studies, adipogenic and osteogenic differentiation, apoptosis assays and scanning electron microscopy. Although hyaluronic acid induced low levels of apoptosis in adipose‑derived stem cells, its significantly promoted proliferation of adipose‑derived stem cells. Hyaluronic acid demonstrates little toxicity against adipose‑derived stem cells. Adipose‑derived stem cells were able to differentiate into adipocytes and osteoblasts. Furthermore, scanning electron microscopy revealed that adipose‑derived stem cells maintained intact structures on the surface of hyaluronic acid as well as in it, and demonstrated abundant cell attachments. The present study demonstrated the compatibility of adipose‑derived stem cells and hyaluronic acid based gels in vitro.

Establishment of a 3D cell culture model of primary bovine mammary epithelial cells extracted from fresh milk

For the investigation of molecular processes underlying diseases of the bovine mammary gland, primary bovine mammary epithelial cells (pbMEC) are used. They are known to contribute to the innate immune system of the bovine mammary gland. The functionality of pbMEC depends on the maintenance of in vivo characteristics. So far, the optimization of pbMEC culture conditions was intended in a variety of experiments. For this purpose, most of the studies used stable cell lines or primary cells obtained from udder biopsies of slaughtered animals. By contrast, within our study, pbMEC of healthy and first lactating Brown Swiss cows were non-invasively isolated from fresh milk. The non-invasively isolated pbMEC were cultivated on the extracellular matrix-like scaffold Matrigel®_. Further, they were challenged with different compositions of proliferation media, containing lactogenic hormones and/or the essential amino acid L-lysine. Changes in expression levels of genes coding for milk proteins and for components of the janus kinase/signal transducers and activators of transcription (JAK-STAT) and mTOR pathways were analyzed by RT-qPCR. The secreted proteins were analyzed by LC-MS/MS measurements. We showed for the first time the establishment of a physiologically functional 3D cell culture model of pbMEC isolated from fresh milk. This represents a primary cell culture model system, based on non-invasive cell collection, that can be used to unravel physiological processes in an unbiased manner.

Assembly of Hepatocyte Spheroids Using Magnetic 3D Cell Culture for CYP450 Inhibition/Induction

There is a significant need for in vitro methods to study drug-induced liver injury that are rapid, reproducible, and scalable for existing high-throughput systems. However, traditional monolayer and suspension cultures of hepatocytes are difficult to handle and risk the loss of phenotype. Generally, three-dimensional (3D) cell culture platforms help recapitulate native liver tissue phenotype, but suffer from technical limitations for high-throughput screening, including scalability, speed, and handling. Here, we developed a novel assay for cytochrome P450 (CYP450) induction/inhibition using magnetic 3D cell culture that overcomes the limitations of other platforms by aggregating magnetized cells with magnetic forces. With this platform, spheroids can be rapidly assembled and easily handled, while replicating native liver function. We assembled spheroids of primary human hepatocytes in a 384-well format and maintained this culture over five days, including a 72 h induction period with known CYP450 inducers/inhibitors. CYP450 activity and viability in the spheroids were assessed and compared in parallel with monolayers. CYP450 activity was induced/inhibited in spheroids as expected, separate from any toxic response. Spheroids showed a significantly higher baseline level of CYP450 activity and induction over monolayers. Positive staining in spheroids for albumin and multidrug resistance-associated protein (MRP2) indicates the preservation of hepatocyte function within spheroids. The study presents a proof-of-concept for the use of magnetic 3D cell culture for the assembly and handling of novel hepatic tissue models.

Proteomic composition and immunomodulatory properties of urinary bladder matrix scaffolds in homeostasis and injury

Urinary bladder matrix (UBM) is used clinically for management of wounds and reinforcement of surgical soft tissue repair, among other applications. UBM consists of the lamina propria and basal lamina of the porcine urinary bladder, and is decellularized as part of the process to manufacture the medical device. UBM is composed mainly of Collagen I, but also contains a wide variety of fibrillar and basement membrane collagens, glycoproteins, proteoglycans and ECM-associated factors. Upon application of the biomaterial in a traumatic or non-traumatic setting in a mouse model, there is a cascade of immune cells that respond to the damaged tissue and biomaterial. Here, through the use of multicolor flow cytometry, we describe the various cells that infiltrate the UBM scaffold in a subcutaneous and volumetric muscle injury model. A wide variety of immune cells are found in the UBM scaffold immune microenvironment (SIM) including F4/80⁺ macrophages, CD11c⁺ dendritic cells, CD3⁺ T cells and CD19⁺ B cells. A systemic IL-4 upregulation and a local M2-macrophage response were observed in the proximity of the implanted UBM. The recruitment and activation of these cells is dependent upon signals from the scaffold and communication between the different cell types present.

Characterization of rat or human hepatocytes cultured in microphysiological systems (MPS) to identify hepatotoxicity

The liver is the main site for drug and xenobiotics metabolism, including inactivation or bioactivation. In order to improve the predictability of drug safety and efficacy in clinical development, and to facilitate the evaluation of the potential human health effects from exposure to environmental contaminants, there is a critical need to accurately model human organ systems such as the liver in vitro. We are developing a microphysiological system (MPS) based on a new commercial microfluidic platform (Nortis, Inc.) that can utilize primary liver cells from multiple species (e.g., rat and human). Compared to conventional monolayer cell culture, which typically survives for 5-7days or less, primary rat or human hepatocytes in an MPS exhibited higher viability and improved hepatic functions, such as albumin production, expression of hepatocyte marker HNF4α and canaliculi structure, for up to 14days. Additionally, induction of Cytochrome P450 (CYP) 1A and 3A4 in cryopreserved human hepatocytes was observed in the MPS. The acute cytotoxicity of the potent hepatotoxic and hepatocarcinogen, aflatoxin B₁, was evaluated in human hepatocytes cultured in an MPS, demonstrating the utility of this model for acute hepatotoxicity assessment. These results indicate that MPS-cultured hepatocytes provide a promising approach for evaluating chemical toxicity in vitro.

MSCs on an acellular dermal matrix (ADM) sourced from neonatal mouse skin regulate collagen reconstruction of granulation tissue during adult cutaneous wound healing

The novel strategy of MSCs seeded on ADM sourced from neonatal mouse skin promotes full-thickness cutaneous wound healing.

The function of heparan sulfate during branching morphogenesis

Branching morphogenesis is a fundamental process in the development of diverse epithelial organs such as the lung, kidney, liver, pancreas, prostate, salivary, lacrimal and mammary glands. A unifying theme during organogenesis is the importance of epithelial cell interactions with the extracellular matrix (ECM) and growth factors (GFs). The diverse developmental mechanisms giving rise to these epithelial organs involve many organ-specific GFs, but a unifying paradigm during organogenesis is the regulation of GF activity by heparan sulfates (HS) on the cell surface and in the ECM. This primarily involves the interactions of GFs with the sulfated side-chains of HS proteoglycans. HS is one of the most diverse biopolymers and modulates GF binding and signaling at the cell surface and in the ECM of all tissues. Here, we review what is known about how HS regulates branching morphogenesis of epithelial organs with emphasis on the developing salivary gland, which is a classic model to investigate epithelial-ECM interactions. We also address the structure, biosynthesis, turnover and function of HS during organogenesis. Understanding the regulatory mechanisms that control HS dynamics may aid in the development of therapeutic interventions for diseases and novel strategies for tissue engineering and regenerative medicine.

The synergistic effect of type I collagen and hyaluronic acid on the biological properties of Col/HA-multilayer-modified titanium coatings: an in vitro and in vivo study

The synergistic effect on osseointegration is existed between Type I collagen (ColI) and hyaluronic acid (HA), and the early osseogenetic activity of ColI/HA multilayer modified titanium coatings (TC) is higher than that ColI modified TC and HA modified TC.

A 3D Culture Model to Study How Fluid Pressure and Flow Affect the Behavior of Aggregates of Epithelial Cells

Cells are surrounded by mechanical stimuli in their microenvironment. It is important to determine how cells respond to the mechanical information that surrounds them in order to understand both development and disease progression, as well as to be able to predict cell behavior in response to physical stimuli. Here we describe a protocol to determine the effects of interstitial fluid flow on the migratory behavior of an aggregate of epithelial cells in a three-dimensional (3D) culture model. This protocol includes detailed methods for the fabrication of a 3D cell culture chamber with hydrostatic pressure control, the culture of epithelial cells as an aggregate in a collagen gel, and the analysis of collective cell behavior in response to pressure-driven flow.

Identification of Novel Equine (Equus caballus) Tendon Markers Using RNA Sequencing

Although several tendon-selective genes exist, they are also expressed in other musculoskeletal tissues. As cell and tissue engineering is reliant on specific molecular markers to discriminate between cell types, tendon-specific genes need to be identified. In order to accomplish this, we have used RNA sequencing (RNA-seq) to compare gene expression between tendon, bone, cartilage and ligament from horses. We identified several tendon-selective gene markers, and established eyes absent homolog 2 (EYA2) and a G-protein regulated inducer of neurite outgrowth 3 (GPRIN3) as specific tendon markers using RT-qPCR. Equine tendon cells cultured as three-dimensional spheroids expressed significantly greater levels of EYA2 than GPRIN3, and stained positively for EYA2 using immunohistochemistry. EYA2 was also found in fibroblast-like cells within the tendon tissue matrix and in cells localized to the vascular endothelium. In summary, we have identified EYA2 and GPRIN3 as specific molecular markers of equine tendon as compared to bone, cartilage and ligament, and provide evidence for the use of EYA2 as an additional marker for tendon cells in vitro.

Arl4c is a key regulator of tubulogenesis and tumourigenesis as a target gene of Wnt-β-catenin and growth factor-Ras signalling

Epithelial tubular morphogenesis (tubulogenesis) is a fundamental morphogenetic process of many epithelial organs. In this developmental process, epithelial cells migrate, proliferate, polarize and differentiate towards surrounding mesenchymal tissue to form tubule structures. Although epithelial tissue structures are basically stable in the postnatal period, epithelial cells regain highly proliferative and invasive potentials within mesenchymal tissue during tumour formation (tumourigenesis). Therefore, there must be a common molecular basis orchestrating the cellular behaviours involved in both tubulogenesis and tumourigenesis. ADP-ribosylation factor (Arf)-like protein 4c (Arl4c), which belongs to the small GTP-binding protein family, is expressed by the simultaneous activation of Wnt-β-catenin and growth factor-Ras-mitogen-activated protein kinase signalling, was identified as an essential regulator of tubulogenesis. Arl4c expression was also involved in the tumour formation of colorectal and lung cancers. In this review, we focus on Arl4c as a novel Wnt signal target molecule that links epithelial tubulogenesis to tumourigenesis.

Peptidic Biomaterials: From Self-Assembling to Regenerative Medicine

Peptidic biomaterials represent a particularly exciting topic in regenerative medicine. Peptidic scaffolds can be specifically designed for biomimetic customization for targeted therapy. The field is at a pivotal point where preclinical research is being translated into clinics, so it is crucial to understand the theory and describe the status of this rapidly developing technology. In this review, we highlight major advantages and current limitations of self-assembling peptide-based biomaterials, and we discuss the most widely used classes of assembling peptides, describing recent and promising approaches in tissue engineering, drug delivery, and clinics. We also suggest design strategies and hurdles that still need to be overcome to fully exploit their therapeutic potential.

A high-throughput in vitro ring assay for vasoactivity using magnetic 3D bioprinting

Vasoactive liabilities are typically assayed using wire myography, which is limited by its high cost and low throughput. To meet the demand for higher throughput in vitro alternatives, this study introduces a magnetic 3D bioprinting-based vasoactivity assay. The principle behind this assay is the magnetic printing of vascular smooth muscle cells into 3D rings that functionally represent blood vessel segments, whose contraction can be altered by vasodilators and vasoconstrictors. A cost-effective imaging modality employing a mobile device is used to capture contraction with high throughput. The goal of this study was to validate ring contraction as a measure of vasoactivity, using a small panel of known vasoactive drugs. In vitro responses of the rings matched outcomes predicted by in vivo pharmacology, and were supported by immunohistochemistry. Altogether, this ring assay robustly models vasoactivity, which could meet the need for higher throughput in vitro alternatives.