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Food safety is threatened by numerous pathogens and toxins, including mycotoxins. To date, mycotoxins toxicity studies mainly rely on in vitro 2D cell models affected by several limitations, in prims the poor predictability of in vivo conditions. Important efforts have been made in the development of a variety of three-dimensional (3D) models overcoming this limitation and filling the gap between the oversimplified structure of monolayer cultures and the highly complex wholeanimal systems. In the present study, we focused on the cytotoxic effects of sterigmatocystin (STE), ochratoxin A (OTA) and patulin (PAT) using human 3D spheroids derived from bone marrow-derived mesenchymal stem cells (BM-MSC) and human umbilical vein endothelial cells (HUVEC). Cytotoxicity of STE, OTA and PAT (from 6.25 to 100 µM) was determined individually during 24, 48 and 72 h of mycotoxins exposure by ATP assay. The ATP assay showed that after 24 -72 h of exposure, only about 20% cell mortality was induced by the highest STE concentration (100 µM) in spheroids of both cell lines, and no IC50 values were reached at the range of concentrations tested. Contrarily, lower IC50 values were obtained in spheroids exposed to OTA and PAT, suggesting a higher toxicity of these mycotoxins compared to STE in our models. The 3D cell cultures represent a physiologically relevant and innovative in vitro tool for obtaining more realistic and trustworthy results, with the advantage of reducing the number of animals under experimentation, in compliance with the European Union recommendations. This model represents a key tool to address a potential improvement of data quality and a more robust risk assessment. [ABSTRACT FROM AUTHOR]

Humans are exposed to complex mixtures of mycotoxins through diet. Despite the serious threat they pose, mycotoxin risk assessment often overlooks co-exposure. With the aim of filling this gap, the present study investigates the combined cytotoxicity of sterigmatocystin (STE), ochratoxin A (OTA) and patulin (PAT) in human tumour Neuroblastoma and healthy Mesenchymal Stem Cells three-dimensional (3D) spheroids. The range of concentrations tested (1.56-50 μM for STE, 0.78-25 μM for OTA and 0.15-5 μM for PAT) was selected considering the IC 50 values obtained in previous studies and the estimated dietary exposure of consumers. To ensure appropriate experimental conditions, assessments for single mycotoxins and their combinations were conducted simultaneously. The nature of the toxicological interactions among the mycotoxins was then defined using the isobologram analysis. Our results demonstrated increased cytotoxicity in mycotoxin mixtures compared to individual exposure, with abundance of synergistic interactions. These findings highlight that the co-occurrence of STE, OTA and PAT in food may increase their individual toxic effects and should not be underestimated. Moreover, the use of advanced culture models increased the reliability and physiological relevance of our results which can serve as a groundwork for formulating standardized regulatory approaches towards mycotoxin mixtures in food and feed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Hydrogels have emerged as versatile biomaterials with remarkable applications in biomedicine and tissue engineering. Here, we present an overview of recent and ongoing research in Italy, focusing on extracellular matrix-derived, natural, and synthetic hydrogels specifically applied to biomedicine and tissue engineering. The analyzed studies highlight the versatile nature and wide range of applicability of hydrogel-based studies. Attention is also given to the integration of hydrogels within bioreactor systems, specialized devices used in biological studies to culture cells under controlled conditions, enhancing their potential for regenerative medicine, drug discovery, and drug delivery. Despite the abundance of literature on this subject, a comprehensive overview of Italian contributions to the field of hydrogels-based biomedical research is still missing and is thus our focus for this review. Consolidating a diverse range of studies, the Italian scientific community presents a complete landscape for hydrogel use, shaping the future directions of biomaterials research. This review aspires to serve as a guide and map for Italian researchers interested in the development and use of hydrogels in biomedicine.

Mycotoxins are secondary metabolites produced by filamentous fungi associated with a variety of acute and chronic foodborne diseases. Current toxicology studies mainly rely on monolayer cell cultures and animal models, which are undeniably affected by several limitations. To bridge the gap between the current in vitro toxicology approach and the in vivo predictability of the data, we here investigated the cytotoxic effects induced by the mycotoxins sterigmatocystin (STE), ochratoxin A (OTA) and patulin (PAT) on different 2D and 3D cell cultures. We focused on human tumours (neuroblastoma SH-SY5Y cells and epithelial breast cancer MDA-MB-213 cells) and healthy cells (bone marrow-derived mesenchymal stem cells, BM-MSC, and umbilical vein endothelial cells, HUVECs). The cytotoxicity of STE, OTA, and PAT was determined after 24, 48 and 72 h of exposure using an ATP assay in both culture models. Three-dimensional spheroids' morphology was also analysed using the MATLAB-based open source software AnaSP 1.4 version. Our results highlight how each cell line and different culture models showed specific sensitivities, reinforcing the importance of using more complex models for toxicology studies and a multiple cell line approach for an improved and more comprehensive risk assessment.

Diffuse intrinsic pontine glioma (DIPG), affecting children aged 4-7 years, is a rare, aggressive tumor that originates in the pons and then spreads to nearby tissue. DIPG is the leading cause of death for pediatric brain tumors due to its infiltrative nature and inoperability. Radiotherapy has only a palliative effect on stabilizing symptoms. In silico and preclinical studies identified ONC201 as a cytotoxic agent against some human cancer cell lines, including DIPG ones. A single-crystal X-ray analysis of the complex of the human mitochondrial caseinolytic serine protease type C ( h ClpP) and ONC201 (PDB ID: 6DL7) allowed h ClpP to be identified as its main target. The hyperactivation of h ClpP causes damage to mitochondrial oxidative phosphorylation and cell death. In some DIPG patients receiving ONC201, an acquired resistance was observed. In this context, a wide program was initiated to discover original scaffolds for new h ClpP activators to treat ONC201-non-responding patients. Harmaline, a small molecule belonging to the chemical class of β-carboline, was identified through Fingerprints for Ligands and Proteins (FLAP), a structure-based virtual screening approach. Molecular dynamics simulations and a deep in vitro investigation showed interesting information on the interaction and activation of h ClpP by harmaline.

The importance of drug delivery for disease treatment is supported by a vast literature and increasing ongoing clinical studies. Several categories of nano-based drug delivery systems have been considered in recent years, among which lipid-based nanomedicines, both artificial and cell-derived, remain the most approved. The best artificial systems in terms of biocompatibility and low toxicity are liposomes, as they are composed of phospholipids and cholesterol, the main components of cell membranes. Extracellular vesicles-biological nanoparticles released from cells-while resembling liposomes in size, shape, and structure, have a more complex composition with up to hundreds of different types of lipids, proteins, and carbohydrates in their membranes, as well as an internal cargo. Although nanoparticle technologies have revolutionized drug delivery by enabling passive and active targeting, increased stability, improved solubilization capacity, and reduced dose and adverse effects, the clinical translation remains challenging due to manufacturing limitations such as laborious and time-consuming procedures and high batch-to-batch variability. A sea change occurred when microfluidic strategies were employed, offering advantages in terms of precise particle handling, simplified workflows, higher sensitivity and specificity, and good reproducibility and stability over bulk methods. This review examines scientific advances in the microfluidics-mediated production of lipid-based nanoparticles for therapeutic applications. We will discuss the preparation of liposomes using both hydrodynamic focusing of microfluidic flow and mixing by herringbone and staggered baffle micromixers. Then, an overview on microfluidic approaches for producing extracellular vesicles and extracellular vesicles-mimetics for therapeutic applications will describe microfluidic extrusion, surface engineering, sonication, electroporation, nanoporation, and mixing. Finally, we will outline the challenges, opportunities, and future directions of microfluidic investigation of lipid-based nanoparticles in the clinic., Competing Interests: The authors have no conflicts to disclose., (© 2023 Author(s).)

Current investigations in the field of toxicology mostly rely on 2D cell cultures and animal models. Although well-accepted, the traditional 2D cell-culture approach has evident drawbacks and is distant from the in vivo microenvironment. To overcome these limitations, increasing efforts have been made in the development of alternative models that can better recapitulate the in vivo architecture of tissues and organs. Even though the use of 3D cultures is gaining popularity, there are still open questions on their robustness and standardization. In this review, we discuss the current spheroid culture and organ-on-a-chip techniques as well as the main conceptual and technical considerations for the correct establishment of such models. For each system, the toxicological functional assays are then discussed, highlighting their major advantages, disadvantages, and limitations. Finally, a focus on the applications of 3D cell culture for mycotoxin toxicity assessments is provided. Given the known difficulties in defining the safety ranges of exposure for regulatory agency policies, we are confident that the application of alternative methods may greatly improve the overall risk assessment.

Background: Tumor hypoxia stimulates release of extracellular vesicles (EVs) that facilitate short- and long-range intercellular communication and metastatization. Albeit hypoxia and EVs release are known features of Neuroblastoma (NB), a metastasis-prone childhood malignancy of the sympathetic nervous system, whether hypoxic EVs can facilitate NB dissemination is unclear., Methods: Here we isolated and characterized EVs from normoxic and hypoxic NB cell culture supernatants and performed microRNA (miRNA) cargo analysis to identify key mediators of EVs biological effects. We then validated if EVs promote pro-metastatic features both in vitro and in an in vivo zebrafish model., Results: EVs from NB cells cultured at different oxygen tensions did not differ for type and abundance of surface markers nor for biophysical properties. However, EVs derived from hypoxic NB cells (hEVs) were more potent than their normoxic counterpart in inducing NB cells migration and colony formation. miR-210-3p was the most abundant miRNA in the cargo of hEVs; mechanistically, overexpression of miR-210-3p in normoxic EVs conferred them pro-metastatic features, whereas miR-210-3p silencing suppressed the metastatic ability of hypoxic EVs both in vitro and in vivo., Conclusion: Our data identify a role for hypoxic EVs and their miR-210-3p cargo enrichment in the cellular and microenvironmental changes favoring NB dissemination., (© 2023. The Author(s).)

3D constructs are fundamental in tissue engineering and cancer modeling, generating a demand for tailored materials creating a suitable cell culture microenvironment and amenable to be bioprinted. Gelatin methacrylate (GelMA) is a well-known functionalized natural polymer with good printability and binding motifs allowing cell adhesion; however, its tight micropores induce encapsulated cells to retain a non-physiological spherical shape. To overcome this problem, blended GelMa is here blended with Pluronic F-127 (PLU) to modify the hydrogel internal porosity by inducing the formation of larger mesoscale pores. The change in porosity also leads to increased swelling and a slight decrease in Young's modulus. All blends form stable hydrogels both when cast in annular molds and bioprinted in complex structures. Embedded cells maintain high viability, and while Neuroblastoma cancer cells typically aggregate inside the mesoscale pores, Mesenchymal Stem Cells stretch in all three dimensions, forming cell-cell and cell-ECM interactions. The results of this work prove that the combination of tailored porous materials with bioprinting techniques enables to control both the micro and macro architecture of cell-laden constructs, a fundamental aspect for the development of clinically relevant in vitro constructs., (© 2022 The Authors. Macromolecular Bioscience published by Wiley-VCH GmbH.)

The classification of high dimensional gene expression data is key to the development of effective diagnostic and prognostic tools. Feature selection involves finding the best subset with the highest power in predicting class labels. Here, we conducted a comparative study focused on different combinations of feature selectors (Chi-Squared, mRMR, Relief-F, and Genetic Algorithms) and classification learning algorithms (Random Forests, PLS-DA, SVM, Regularized Logistic/Multinomial Regression, and kNN) to identify those with the best predictive capacity. The performance of each combination is evaluated through an empirical study on three benchmark cancer-related microarray datasets. Our results first suggest that the quality of the data relevant to the target classes is key for the successful classification of cancer phenotypes. We also proved that, for a given classification learning algorithm and dataset, all filters have a similar performance. Interestingly, filters achieve comparable or even better results with respect to the GA-based wrappers, while also being easier and faster to implement. Taken together, our findings suggest that simple, well-established feature selectors in combination with optimized classifiers guarantee good performances, with no need for complicated and computationally demanding methodologies.

Major progress in the understanding and treatment of cancer have tremendously improved our knowledge of this complex disease and improved the length and quality of patients' lives. Still, major challenges remain, in particular with respect to cancer metastasis which still escapes effective treatment and remains responsible for 90% of cancer related deaths. In recent years, the advances in cancer cell biology, oncology and tissue engineering converged into the engineered human tissue models of cancer that are increasingly recapitulating many aspects of cancer progression and response to drugs, in a patient-specific context. The complexity and biological fidelity of these models, as well as the specific questions they aim to investigate, vary in a very broad range. When selecting and designing these experimental models, the fundamental question is "how simple is complex enough" to accomplish a specific goal of cancer research. Here we review the state of the art in developing and using the human tissue models in cancer research and developmental drug screening. We describe the main classes of models providing different levels of biological fidelity and complexity, discuss their advantages and limitations, and propose a framework for designing an appropriate model for a given study. We close by outlining some of the current needs, opportunities and challenges in this rapidly evolving field., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Given the increasing importance of establishing better risk assessments for mycotoxins, novel in vitro tools for the evaluation of their toxicity are mandatory. In this study, an in vitro 3D spheroid model from SH-SY5Y cells, a human neuroblastoma cell line, was developed, optimized and characterized to test the cytotoxic effects caused by the mycotoxin sterigmatocystin (STE). STE induced a concentration- and time-dependent cell viability decrease in spheroids. Spheroids displayed cell disaggregation after STE exposure, increasing in a dose-dependent manner and over time. STE also induced apoptosis as confirmed by immunofluorescence staining and Western blot. Following the decreased proliferation and increased apoptosis, STE cytostasis effects were observed by migration assays both in 2D and 3D cell culture. Increased ROS generation, as well as DNA damage were also observed. Taken together, these data highlight the cytotoxic properties of STE and suggest that cell culture models play a pivotal role in the toxicological risk assessment of mycotoxins. The evaluation of cytotoxicity in spheroids (3D) rather than monolayer cultures (2D) is expected to more accurately reflect in vivo-like cell behaviour., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Neuroblastoma is an embryonal malignancy of early childhood arising from the embryonic sympatho-adrenal lineage of the neural crest. About half of all cases are currently classified as high-risk of disease recurrence, with an overall survival rate of less than 40% at 5 years despite intensive therapy. Recent studies on matched primary tumours and at the relapse revealed downregulation of genes transcriptionally silenced by YAP as significant association with neuroblastoma relapse. Here, we evaluated the pharmacological targeting of YAP/TAZ with the YAP/TAZ-TEAD inhibitor Verteporfin (VP) in Tumour Initiating Cells (TICs) derived from High-Risk Neuroblastoma patients. VP treatment suppresses YAP/TAZ expression, induces apoptosis and causes the re-organization of the cytoskeleton reducing cells migration and clonogenic ability. Moreover, VP reduces the percentage of side population cells and ABC transporters involved in drug resistance, and the percentage of stem cell subpopulations CD133+ and CD44 + of TICs. Finally, we demonstrated that VP sensitizes TICs to the standard drugs used for neuroblastoma therapy etoposide and cis-platin opening the way to use VP as drug repositioning candidate for recurrent neuroblastoma., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The ongoing COVID-19 epidemic highlights the need for effective tools capable of predicting the onset of infection outbreaks at their early stages. The tracing of confirmed cases and the prediction of the local dynamics of contagion through early indicators are crucial measures to a successful fight against emerging infectious diseases (EID). The proposed framework is model-free and applies Early Warning Detection Systems (EWDS) techniques to detect changes in the territorial spread of infections in the very early stages of onset. This study uses publicly available raw data on the spread of SARS-CoV-2 mainly sourced from the database of the Italian Civil Protection Department. Two distinct EWDS approaches, the Hub-Jones (H&J) and Strozzi-Zaldivar (S&Z), are adapted and applied to the current SARS-CoV-2 outbreak. They promptly generate warning signals and detect the onset of an epidemic at early surveillance stages even if working on the limited daily available, open-source data. Additionally, EWDS S&Z criterion is theoretically validated on the basis of the epidemiological SIR. Discussed EWDS successfully analyze self-accelerating systems, like the SARS-CoV-2 scenario, to precociously identify an epidemic spread through the calculation of onset parameters. This approach can also facilitate early clustering detection, further supporting common fight strategies against the spread of EIDs. Overall, we are presenting an effective tool based on solid scientific and methodological foundations to be used to complement medical actions to contrast the spread of infections such as COVID-19., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

3D in vitro constructs have gained more and more relevance in tissue engineering and in cancer-modeling. In recent years, with the development of thicker and more physiologically relevant tissue patches, the integration of a vascular network has become pivotal, both for sustaining the construct in vitro and to help the integration with the host tissue once implanted. Since 3D bioprinting is rising to be one of the most versatile methods to create vascularized constructs, we here briefly review the most promising advances in bioprinting techniques.

Live imaging of stem cells and their support cells can be used to visualize cellular dynamics and fluctuations of intracellular signals, proteins, and organelles in order to better understand stem cell behavior in the niche. We describe a simple protocol for imaging stem cells in the Drosophila ovary that improves on alternative protocols in that flies of any age can be used, dissection is simplified because the epithelial sheath that surrounds each ovariole need not be removed, and ovarioles are imaged in a closed chamber with a large volume of medium that buffers oxygen, pH, and temperature. We also describe how to construct the imaging chamber, which can be easily modified and used to image other tissues and non-adherent cells. Imaging is limited by follicle cells moving out of the germarium in culture around the time of egg chamber budding; however, the epithelial sheath delays this abnormal cell migration. This protocol requires an hour to prepare the ovarioles, followed by half an hour on the confocal microscope to locate germaria and set z limits. Successful imaging time depends on germarial morphology at the time of dissection, but we suggest 10-11 h to encompass all specimens.

Human-induced pluripotent stem cells (hiPSCs) are reprogrammed cells that have hallmarks similar to embryonic stem cells including the capacity of self-renewal and differentiation into cardiac myocytes. The improvements in reprogramming and differentiating methods achieved in the past 10 years widened the use of hiPSCs, especially in cardiac research. hiPSC-derived cardiac myocytes (CMs) recapitulate phenotypic differences caused by genetic variations, making them attractive human disease models and useful tools for drug discovery and toxicology testing. In addition, hiPSCs can be used as sources of cells for cardiac regeneration in animal models. Here, we review the advances in the genetic and epigenetic control of cardiomyogenesis that underlies the significant improvement of the induced reprogramming of somatic cells to CMs; the methods used to improve scalability of throughput assays for functional screening and drug testing in vitro; the phenotypic characteristics of hiPSCs-derived CMs and their ability to rescue injured CMs through paracrine effects; we also cover the novel approaches in tissue engineering for hiPSC-derived cardiac tissue generation, and finally, their immunological features and the potential use in biomedical applications.

Adult stem cells provide a renewable source of differentiated cells for a wide variety of tissues and generally give rise to multiple cell types. Basic principles of stem cell organization and regulation underlying this behaviour are emerging. Local niche signals maintain stem cells, while different sets of signals act outside the niche to diversify initially equivalent stem cell progeny. Here we show that Drosophila ovarian follicle stem cells (FSCs) produced two distinct cell types directly. This cell fate choice was determined by the anterior-posterior position of an FSC and by the magnitude of spatially graded Wnt pathway activity. These findings reveal a paradigm of immediate diversification of stem cell derivatives according to stem cell position within a larger population, guided by a graded niche signal. We also found that FSCs strongly resemble mammalian intestinal stem cells in many aspects of their organization, including population asymmetry and dynamic heterogeneity.

In vivo, cells reside in a complex environment regulating their fate and function. Most of this complexity is lacking in standard in vitro models, leading to readouts falling short of predicting the actual in vivo situation. The use of engineering tools, combined with deep biological knowledge, leads to the development and use of bioreactors providing biologically sound niches. Such bioreactors offer new tools for biological research, and are now also entering the field of cancer research. Here we present the development and validation of a modular bioreactor system providing: (i) high throughput analyses, (ii) a range of biological conditions, (iii) high degree of control, and (iv) application of physiological stimuli to the cultured samples. The bioreactor was used to engineer a three-dimensional (3D) tissue model of cancer, where the effects of mechanical stimulation on the tumor phenotype were evaluated. Mechanical stimuli applied to the engineered tumor model activated the mechanotransduction machinery and resulted in measurable changes of mRNA levels towards a more aggressive tumor phenotype.

The pressing need for effective cell therapy for the heart has led to the investigation of suitable cell sources for tissue replacement. In recent years, human pluripotent stem cell research expanded tremendously, in particular since the derivation of human-induced pluripotent stem cells. In parallel, bioengineering technologies have led to novel approaches for in vitro cell culture. The combination of these two fields holds potential for in vitro generation of high-fidelity heart tissue, both for basic research and for therapeutic applications. However, this new multidisciplinary science is still at an early stage. Many questions need to be answered and improvements need to be made before clinical applications become a reality. Here we discuss the current status of human stem cell differentiation into cardiomyocytes and the combined use of bioengineering approaches for cardiac tissue formation and maturation in developmental studies, disease modeling, drug testing, and regenerative medicine., (© 2015 by the Society for Experimental Biology and Medicine.)

During development and regeneration, tissues emerge from coordinated sequences of stem cell renewal, specialization, and assembly that are orchestrated by cascades of regulatory factors. This complex in vivo milieu, while necessary to fully recapitulate biology and to properly engineer progenitor cells, is difficult to replicate in vitro. We are just starting to fully realize the importance of the entire context of cell microenvironment-the other cells, three-dimensional matrix, molecular and physical signals. Bioengineered environments that combine tissue-specific transport and signaling are critical to study cellular responses at biologically relevant scales and in settings predictive of human condition. We therefore developed microbioreactors that couple the application of fast dynamic changes in environmental signals with versatile, high-throughput operation and imaging capability. Our base device is a microfluidic platform with an array of microwells containing cells or tissue constructs that are exposed to stable concentration gradients. Mathematical modeling of flow and mass transport can predict the shape of these gradients and the kinetic changes in local concentrations. A single platform, the size of a microscope slide, contains up to 120 biological samples. As an example of application, we describe studies of cell fate specification and mesodermal lineage commitment in human embryonic stem cells and induced pluripotent stem cells. The embryoid bodies formed from these cells were subjected to single and multiple concentration gradients of Wnt3a, Activin A, bone morphogenic protein 4 (BMP4), and their inhibitors, and the gene expression profiles were correlated to the concentration gradients of morphogens to identify the exact conditions for mesodermal differentiation., (© 2014 by the Society for Experimental Biology and Medicine.)

Electrical signals have been implied in many biological mechanisms, including wound healing, which has been associated with transient electrical currents not present in intact skin. One method to generate electrical signals similar to those naturally occurring in wounds is by supplementation of galvanic particles dispersed in a cream or gel. We constructed a three-layered model of skin consisting of human dermal fibroblasts in hydrogel (mimic of dermis), a hydrogel barrier layer (mimic of epidermis) and galvanic microparticles in hydrogel (mimic of a cream containing galvanic particles applied to skin). Using this model, we investigated the effects of the properties and amounts of Cu/Zn galvanic particles on adult human dermal fibroblasts in terms of the speed of wound closing and gene expression. The collected data suggest that the effects on wound closing are due to the ROS-mediated enhancement of fibroblast migration, which is in turn mediated by the BMP/SMAD signaling pathway. These results imply that topical low-grade electric currents via microparticles could enhance wound healing., (© 2013 Elsevier Inc. All rights reserved.)

Stem cells hold promise to revolutionize modern medicine by the development of new therapies, disease models and drug screening systems. Standard cell culture systems have limited biological relevance because they do not recapitulate the complex 3-dimensional interactions and biophysical cues that characterize the in vivo environment. In this review, we discuss the current advances in engineering stem cell environments using novel biomaterials and bioreactor technologies. We also reflect on the challenges the field is currently facing with regard to the translation of stem cell based therapies into the clinic., (Copyright © 2013 Elsevier Inc. All rights reserved.)

A classical paradigm of tissue engineering is to grow tissues for implantation by using human stem cells in conjunction with biomaterial scaffolds (templates for tissue formation) and bioreactors (culture systems providing environmental control). A reverse paradigm is now emerging through microphysiological platforms for preclinical testing of drugs and modeling of disease that contain large numbers of very small human tissues. We discuss the biomimetic approach as a common underlying principle and some of the specifics related to the design and utilization of platforms with heart micro-tissues for high-throughput screening in vitro., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

During development and regeneration, tissues emerge from coordinated sequences of stem cell renewal, specialization and assembly that are orchestrated by cascades of regulatory signals. The complex and dynamic in vivo milieu cannot be replicated using standard in vitro techniques. Microscale technologies now offer potential for conducting highly controllable and sophisticated experiments at biologically relevant scales, with real-time insights into cellular responses. We developed a microbioreactor providing time sequences of space-resolved gradients of multiple molecular factors in three-dimensional (3D) cell culture settings, along with a versatile, high-throughput operation and imaging compatibility. A single microbioreactor yields up to 120 data points, corresponding to 15 replicates of a gradient with 8 concentration levels. Embryoid bodies (EBs) obtained from human embryonic and induced pluripotent stem cells (hESC, hiPSC) were exposed to concentration gradients of Wnt3a, Activin A, BMP4 and their inhibitors, to get new insights into the early-stage fate specification and mesodermal lineage commitment. We were able to evaluate the initiation of mesodermal induction by measuring and correlating the gene expression profiles to the concentration gradients of mesoderm-inducing morphogens. We propose that the microbioreactor systems combining spatial and temporal gradients of molecular and physical factors to hESC and hiPSC cultures can form a basis for predictable in vitro models of development and disease.

Electrical activity is abundant in early retinal development, and electrical stimulation has been shown to modulate embryonic stem cell differentiation towards a neuronal fate. The goal of this study was to simulate in vitro retinal developmental electrical activity to drive changes in mouse retinal progenitor cell (mRPC) gene expression and morphology. We designed a biomimetic electrical stimulation protocol based on spontaneous waves present during retinal development, and applied it to retinal progenitor cells (RPCs) over 3 days of culture. Analysis of protein localization and calcium dynamics, indicate that mRPCs undergo functional neuronal maturation. Our findings suggest that this type of electrical stimulation may be utilized for application in neural tissue engineering and open possibilities for understanding mechanisms guiding active electric membrane development and functional organization during early retinogenesis.

The goal of this study was to simulate in vitro the spontaneous electrical wave activity associated with retinal development and investigate if such biometrically designed signals can enhance differentiation of mouse retinal progenitor cells (mRPC). To this end, we cultured cells on an electroconductive transplantable polymer, polypyrrole (PPy) and measured gene expression and morphology of the cells. Custom-made 8-well cell culture chambers were designed to accommodate PPy deposited onto indium tin oxide-coated (ITO) glass slides, with precise control of the PPy film thickness. mRPCs were isolated from post-natal day 1 (P1) green fluorescent protein positive (GFP+) mice, expanded, seeded onto PPY films, allowed to adhere for 24 hours, and then subjected to electrical stimulation (100 µA pulse trains, 5 s in duration, once per minute) for 4 days. Cultured cells and non-stimulated controls were processed for immunostaining and confocal analysis, and for RNA extraction and quantitative PCR. Stimulated cells expressed significantly higher levels of the early photoreceptor marker cone-rod homebox (CRX, the earliest known marker of photoreceptor identity), and protein kinase-C (PKC), and significantly lower levels of the glial fibrillary acidic protein (GFAP). Consistently, stimulated cells developed pronounced neuronal morphologies with significantly longer dendritic processes and larger cell bodies than non-stimulated controls. Taken together, the experimental evidence shows that the application of an electrical stimulation designed based on retinal development can be implemented to direct and enhance retinal differentiation of mRPCs, suggesting a role for biomimetic electrical stimulation in directing progenitor cells toward neural fates.

Cardiac tissue engineering aims to create functional tissue constructs that can reestablish the structure and function of injured myocardium. Although bioreactors have facilitated the engineering of cardiac patches of clinically relevant size in vitro, a major drawback remains the transportation of the engineered tissues from a production facility to a medical operation facility while maintaining tissue viability and preventing contamination. Furthermore, after implantation, most of the cells are endangered by hypoxic conditions that exist before vascular flow is established. We developed a portable device that provides the perfusion and electrical stimulation necessary to engineer cardiac tissue in vitro, and to transport it to the site where it will be implantated. The micropump-powered perfusion apparatus may additionally function as an extracorporeal active pumping system providing nutrients and oxygen supply to the graft post-implantation. Such a system, through perfusion of oxygenated media and bioactive molecules (e.g. growth factors), could transiently support the tissue construct until it connects to the host vasculature and heart muscle, after which it could be taken away or let biodegrade.

In the past few decades the scientific community has been recognizing the paramount role of the cell microenvironment in determining cell behavior. In parallel, the study of human stem cells for their potential therapeutic applications has been progressing constantly. The use of advanced technologies, enabling one to mimic the in vivo stem cell microenviroment and to study stem cell physiology and physio-pathology, in settings that better predict human cell biology, is becoming the object of much research effort. In this review we will detail the most relevant and recent advances in the field of biosensors and micro- and nano-technologies in general, highlighting advantages and disadvantages. Particular attention will be devoted to those applications employing stem cells as a sensing element.

Advanced cell culture systems creating a controlled and predictable microenvironment together with computational modeling may be useful tools to optimize the efficiency of cell infections. In this paper, we will present a phenomenological study of a virus-host infection system, and the development of a multilayered microfluidic platform used to accurately tune the virus delivery from a diffusive-limited regime to a convective-dominated regime. Mathematical models predicted the convective-diffusive regimes developed within the system itself and determined the dominating mass transport phenomena. Adenoviral vectors carrying the enhanced green fluorescent protein (EGFP) transgene were used at different multiplicities of infection (MOI) to infect multiple cell types, both in standard static and in perfused conditions. Our results validate the mathematical models and demonstrate how the infection processes through perfusion via microfluidic platform led to an enhancement of adenoviral infection efficiency even at low MOIs. This was particularly evident at the longer time points, since the establishment of steady-state condition guaranteed a constant viral concentration close to cells, thus strengthening the efficiency of infection. Finally, we introduced the concept of effective MOI, a more appropriate variable for microfluidic infections that considers the number of adenoviruses in solution per cell at a certain time.

Micropatterning techniques and substrate engineering are becoming useful tools to investigate several aspects of cell-cell interaction biology. In this work, we rationally study how different micropatterning geometries can affect myoblast behavior in the early stage of in vitro myogenesis. Soft hydrogels with physiological elastic modulus (E = 15 kPa) were micropatterned in parallel lanes (100, 300, and 500 μm width) resulting in different local and global myoblast densities. Proliferation and differentiation into multinucleated myotubes were evaluated for murine and human myoblasts. Wider lanes showed a decrease in murine myoblast proliferation: (69 ± 8)% in 100 μm wide lanes compared to (39 ± 7)% in 500 μm lanes. Conversely, fusion index increased in wider lanes: from (46 ± 7)% to (66 ± 7)% for murine myoblasts, and from (15 ± 3)% to (36 ± 2)% for human primary myoblasts, using a patterning width of 100 and 500 μm, respectively. These results are consistent with both computational modeling data and conditioned medium experiments, which demonstrated that wider lanes favor the accumulation of endogenous secreted factors. Interestingly, human primary myoblast proliferation is not affected by patterning width, which may be because the high serum content of their culture medium overrides the effect of secreted factors. These data highlight the role of micropatterning in shaping the cellular niche through secreted factor accumulation, and are of paramount importance in rationally understanding myogenesis in vitro for the correct design of in vitro skeletal muscle models.

Introduction: The heart is one of the least regenerative organs in the body and any major insult can result in a significant loss of heart cells. The development of an in vitro-based cardiac tissue could be of paramount importance for many aspects of the cardiology research. In this context, we developed an in vitro assay based on human cardiomyocytes (hCMs) and ad hoc micro-technologies, suitable for several applications: from pharmacological analysis to physio-phatological studies on transplantable hCMs. We focused on the development of an assay able to analyze not only hCMs viability, but also their functionality., Methods: hCMs were cultured onto a poly-acrylamide hydrogel with tunable tissue-like mechanical properties and organized through micropatterning in a 20×20 array. Arrayed hCMs were characterized by immunofluorescence, GAP-FRAP analyses and live and dead assay. Their functionality was evaluated monitoring the excitation-contraction coupling., Results: Micropatterned hCMs maintained the expression of the major cardiac markers (cTnT, cTnI, Cx43, Nkx2.5, α-actinin) and functional properties. The spontaneous contraction frequency was (0.83±0.2) Hz, while exogenous electrical stimulation lead to an increase up to 2 Hz. As proof of concept that our device can be used for screening the effects of pathological conditions, hCMs were exposed to increasing levels of H(2)O(2). Remarkably, hCMs viability was not compromised with exposure to 0.1 mM H(2)O(2), but hCMs contractility was dramatically suppressed. As proof of concept, we also developed a microfluidic platform to selectively treat areas of the cell array, in the perspective of performing multi-parametric assay., Conclusions: Such system could be a useful tool for testing the effects of multiple conditions on an in vitro cell model representative of human heart physiology, thus potentially helping the processes of therapy and drug development.

The New York Stem Cell Foundation's "Fifth Annual Translational Stem Cell Research Conference" convened on October 12-13, 2010 at the Rockefeller University in New York City. The conference attracted over 400 scientists, patient advocates, and stem cell research supporters from 16 countries. In addition to poster and platform presentations, the conference featured panels entitled "Road to the Clinic" and "Regulatory Roadblocks.", (© 2011 New York Academy of Sciences.)

In developing tissues, proteins and signaling molecules present themselves in the form of concentration gradients, which determine the fate specification and behavior of the sensing cells. To mimic these conditions in vitro, we developed a microfluidic device designed to generate stable concentration gradients at low hydrodynamic shear and allowing long term culture of adhering cells. The gradient forms in a culture space between two parallel laminar flow streams of culture medium at two different concentrations of a given morphogen. The exact algorithm for defining the concentration gradients was established with the aid of mathematical modeling of flow and mass transport. Wnt3a regulation of β-catenin signaling was chosen as a case study. The highly conserved Wnt-activated β-catenin pathway plays major roles in embryonic development, stem cell proliferation and differentiation. Wnt3a stimulates the activity of β-catenin pathway, leading to translocation of β-catenin to the nucleus where it activates a series of target genes. We cultured A375 cells stably expressing a Wnt/β-catenin reporter driving the expression of Venus, pBARVS, inside the microfluidic device. The extent to which the β-catenin pathway was activated in response to a gradient of Wnt3a was assessed in real time using the BARVS reporter gene. On a single cell level, the β-catenin signaling was proportionate to the concentration gradient of Wnt3a; we thus propose that the modulation of Wnt3a gradients in real time can provide new insights into the dynamics of β-catenin pathway, under conditions that replicate some aspects of the actual cell-tissue milieu. Our device thus offers a highly controllable platform for exploring the effects of concentration gradients on cultured cells.

The in vitro development of human myotubes carrying genetic diseases, such as Duchenne Muscular Dystrophy, will open new perspectives in the identification of innovative therapeutic strategies. Through the proper design of the substrate, we guided the differentiation of human healthy and dystrophic myoblasts into myotubes exhibiting marked functional differentiation and highly defined sarcomeric organization. A thin film of photo cross-linkable elastic poly-acrylamide hydrogel with physiological-like and tunable mechanical properties (elastic moduli, E: 12, 15, 18 and 21 kPa) was used as substrate. The functionalization of its surface by micro-patterning in parallel lanes (75 microm wide, 100 microm spaced) of three adhesion proteins (laminin, fibronectin and matrigel) was meant to maximize human myoblasts fusion. Myotubes formed onto the hydrogel showed a remarkable sarcomere formation, with the highest percentage (60.0% +/- 3.8) of myotubes exhibiting sarcomeric organization, of myosin heavy chain II and alpha-actinin, after 7 days of culture onto an elastic (15 kPa) hydrogel and a matrigel patterning. In addition, healthy myotubes cultured in these conditions showed a significant membrane-localized dystrophin expression. In this study, the culture substrate has been adapted to human myoblasts differentiation, through an easy and rapid methodology, and has led to the development of in vitro human functional skeletal muscle myotubes useful for clinical purposes and in vitro physiological study, where to carry out a broad range of studies on human muscle physiopathology.

Responding to the need of creating an accurate and controlled microenvironment surrounding the cell while meeting the requirements for biological processes or pharmacological screening tests, we aimed at designing and developing a microscaled culture system suitable for analyzing the synergic effects of extracellular matrix proteins and soluble environments on cell phenotype in a high-throughput fashion. We produced cell arrays deposing micrometer-scale protein islands on hydrogels using a robotic DNA microarrayer, constrained the culture media in a droplet-like volume and developed a suitable perfusion system. The droplet-confined cell arrays were used either with conventional culture methods (batch operating system) or with automated stable and constant perfusion (steady-state operating system). Mathematical modeling assisted the experimental design and assessed efficient mass transport and proper fluidodynamic regimes. Cells cultured on arrayed islands (500 mum diameter) maintained the correct phenotype both after static and perfused conditions, confirmed by immunostaining and gene expression analyses through total RNA extraction. The mathematical model, validated using a particle tracking experiment, predicted the constant value of velocities over the cell arrays (less than 10% variation) ensuring the same mass transport regime. BrdU analysis on an average of 96 cell spots for each experimental condition showed uniform expression inside each cell island and low variability in the data (average of 13%). Perfused arrays showed longer doubling times when compared with static cultures. In addition, perfused cultures showed a reduced variability in the collected data, allowing to detect statistically significant differences in cell behavior depending on the spotted ECM protein.

An in vitro muscle-like structure with parallel-oriented contractile myotubes is needed as a model of muscle tissue regeneration. For this purpose, it is necessary to reproduce a controllable microscale environment mimicking the in vivo cues. In this work we focused on the application of topological and electrical stimuli on muscle precursor cell (MPC) culture to influence MPC orientation and induce myotube alignment. The two stimulations were tested both independently and together. A structural and topological template was achieved using micropatterned poly-(L-lactic acid) membranes. Electrical stimulation, consisting of square pulses of 70 mV/cm amplitude each 30 s, was applied to the MPC culture. The effect of different pulse durations on cultures was evaluated by galvanotaxis analysis. The highest cell displacement rate toward the cathode was observed for 3 ms pulse stimulation, which was then applied in combination with topological stimuli. Topological and electrical stimuli had an additive effect in enhancing differentiation of cultured MPC, shown by high Troponin I protein production and, in parallel, Myogenin and Desmin genes, down- and upregulation respectively.

Micropatterning and microfabrication techniques have been widely used to pattern cells on surfaces and to have a deeper insight into many processes in cell biology such as cell adhesion and interactions with the surrounding environment. The aim of this study was the development of an easy and versatile technique for the in vitro production of arrays of functional cardiac and skeletal muscle myofibers using micropatterning techniques on soft substrates. Cardiomyocytes were used for the production of oriented cardiac myofibers whereas mouse muscle satellite cells for that of differentiated parallel myotubes. We performed micro-contact printing of extracellular matrix proteins on soft polyacrylamide-based hydrogels photopolymerized onto functionalized glass slides. Our methods proved to be simple, repeatable and effective in obtaining an extremely selective adhesion of both cardiomyocytes and satellite cells onto patterned soft hydrogel surfaces. Cardiomyocytes resulted in aligned cardiac myofibers able to exhibit a synchronous contractile activity after 2 days of culture. We demonstrated for the first time that murine satellite cells, cultured on a soft hydrogel substrate, fuse and form aligned myotubes after 7 days of culture. Immunofluorescence analyses confirmed correct expression of cell phenotype, differentiation markers and sarcomeric organization. These results were obtained in myotubes derived from satellite cells from both wild type and MDX mice which are research models for the study of muscle dystrophy. These arrays of both cardiac and skeletal muscle myofibers could be used as in vitro models for pharmacological screening tests or biological studies at the single fiber level.

We discuss the utilization of micro-bioreactor arrays for controlling cellular environments in studies of factors that regulate the differentiation of human embryonic stem cells. To this end, we have designed a simple and practical system that couples a microfluidic platform with an array of micro-bioreactors, and has the size of a microscope slide [E. Figallo, C. Cannizzaro, S. Gerecht, J.A. Burdick, R. Langer, N. Elvassore, G. Vunjak-Novakovic, Lab Chip 7 (2007) 710-719]. The system allows quantitative studies of cells cultured in monolayers or encapsulated in three-dimensional hydrogels. We review the operating requirements for studies of human embryonic stem cells (hESCs) under steady-state and dynamic conditions, and the related control of the mass transport and hydrodynamic shear. We describe the design and fabrication of the individual bioreactor components, and the criteria for selecting the bioreactor configuration and operating parameters, based on the analysis of the characteristic times and scales of reaction, convection and diffusion. To illustrate the utility of the bioreactor, we present a "case study" of hESC cultivation with detailed experimental methods and representative biological readouts.

The success of cell therapy for skeletal muscle disorders depends upon two main factors: the cell source and the method of delivery. In this work we have explored the therapeutic potential of human muscle precursor cells (hMPCs), obtained from single human muscle fibers, implanted in vivo via micropatterned scaffolds. hMPCs were initially expanded and characterized in vitro by immunostaining and flow cytometric analysis. For in vivo studies, hMPCs were seeded onto micropatterned poly-lactic-glycolic acid 3D-scaffolds fabricated using soft-lithography and thermal membrane lamination. Seeded scaffolds were then implanted in predamaged tibialis anterior muscles of CD1 nude mice; hMPCs were also directly injected in contralateral limbs as controls. Similarly to what we previously described with mouse precursors cells, we found that hMPCs were able to participate in muscle regeneration and scaffold-implanted muscles contained a greater number of human nuclei, as revealed by immunostaining and Western blot analyses. These results indicate that hMPCs derived from single fibers could be a good and reliable cell source for the design of therapeutic protocols and that implantation of cellularized scaffolds is superior to direct injection for the delivery of myogenic cells into regenerating skeletal muscle.

The aim of this study was to develop a methodology for the in vitro expansion of skeletal-muscle precursor cells (SMPC) in a three-dimensional (3D) environment in order to fabricate a cellularized artificial graft characterized by high density of viable cells and uniform cell distribution over the entire 3D domain. Cell seeding and culture within 3D porous scaffolds by conventional static techniques can lead to a uniform cell distribution only on the scaffold surface, whereas dynamic culture systems have the potential of allowing a uniform growth of SMPCs within the entire scaffold structure. In this work, we designed and developed a perfusion bioreactor able to ensure long-term culture conditions and uniform flow of medium through 3D collagen sponges. A mathematical model to assist the design of the experimental setup and of the operative conditions was developed. The effects of dynamic vs static culture in terms of cell viability and spatial distribution within 3D collagen scaffolds were evaluated at 1, 4 and 7 days and for different flow rates of 1, 2, 3.5 and 4.5 ml/min using C2C12 muscle cell line and SMPCs derived from satellite cells. C2C12 cells, after 7 days of culture in our bioreactor, perfused applying a 3.5 ml/min flow rate, showed a higher viability resulting in a three-fold increase when compared with the same parameter evaluated for cultures kept under static conditions. In addition, dynamic culture resulted in a more uniform 3D cell distribution. The 3.5 ml/min flow rate in the bioreactor was also applied to satellite cell-derived SMPCs cultured on 3D collagen scaffolds. The dynamic culture conditions improved cell viability leading to higher cell density and uniform distribution throughout the entire 3D collagen sponge for both C2C12 and satellite cells.

Myoblast transplantation is a potentially useful therapeutic tool in muscle diseases, but the lack of an efficient delivery system has hampered its application. Here we have combined cell biology and polymer processing to create an appropriate microenvironment for in vivo transplantation of murine satellite cells (mSCs). Cells were prepared from single muscle fibers derived from C57BL/6-Tgn enhanced green fluorescent protein (GFP) transgenic mice. mSCs were expanded and seeded within micro-patterned polyglycolic acid 3-dimensional scaffolds fabricated using soft lithography and thermal membrane lamination. Myogenicity was then evaluated in vitro using immunostaining, flow cytometry, and reverse transcription polymerase chain reaction analyses. Scaffolds containing mSCs were implanted in pre-damaged tibialis anterior muscles of GFP-negative syngenic mice. Cells detached from culture dishes were directly injected into contra-lateral limbs as controls. In both cases, delivered cells participated in muscle regeneration, although scaffold-implanted muscles showed a much higher number of GFP-positive fibers in CD57 mice. These findings suggest that implantation of cellularized scaffolds is better than direct injection for delivering myogenic cells into regenerating skeletal muscle.