Optimization of a 3D Dynamic Culturing System for In Vitro Modeling of Frontotemporal Neurodegeneration-Relevant Pathologic Features

Hep3Gel: A Shape-Shifting Extracellular Matrix-Based, Three-Dimensional Liver Model Adaptable to Different Culture Systems

Drug-induced hepatotoxicity is a leading cause of clinical trial withdrawal. Therefore, in vitro modeling the hepatic behavior and functionalities is not only crucial to better understand physiological and pathological processes but also to support drug development with reliable high-throughput platforms. Different physiological and pathological models are currently under development and are commonly implemented both within platforms for standard 2D cultures and within tailor-made chambers. This paper introduces Hep3Gel: a hybrid alginate-extracellular matrix (ECM) hydrogel to produce 3D in vitro models of the liver, aiming to reproduce the hepatic chemomechanical niche, with the possibility of adapting its shape to different manufacturing techniques. The ECM, extracted and powdered from porcine livers by a specifically set-up procedure, preserved its crucial biological macromolecules and was embedded within alginate hydrogels prior to crosslinking. The viscoelastic behavior of Hep3Gel was tuned, reproducing the properties of a physiological organ, according to the available knowledge about hepatic biomechanics. By finely tuning the crosslinking kinetics of Hep3Gel, its dualistic nature can be exploited either by self-spreading or adapting its shape to different culture supports or retaining the imposed fiber shape during an extrusion-based 3D-bioprinting process, thus being a shape-shifter hydrogel. The self-spreading ability of Hep3Gel was characterized by combining empirical and numerical procedures, while its use as a bioink was experimentally characterized through rheological a priori printability evaluations and 3D printing tests. The effect of the addition of the ECM was evident after 4 days, doubling the survival rate of cells embedded within control hydrogels. This study represents a proof of concept of the applicability of Hep3Gel as a tool to develop 3D in vitro models of the liver.

Characterization of the Microflow Through 3D Synthetic Niche Microenvironments Hosted in a Millifluidic Bioreactor

Background: Development of new medicines is a lengthy process with high risk of failure since drug efficacy measured in vitro is difficult to confirm in vivo. Intended to add a new tool aiding drug discovery, the MOAB-NICHOID device was developed: a miniaturized optically accessible bioreactor (MOAB) housing the 3D engineered scaffold NICHOID. The aim of our study was to characterize the microflow through the 3D nichoid microenvironment hosted in the MOAB-NICHOID device.

Methods: We used computational fluid dynamics (CFD) simulations to compute the flow field inside a very fine grid resembling the scaffold microenvironment.

Results: The microflow inside the multi-array of nichoid blocks is fed and locally influenced by the mainstream flow developed in the perfusion chamber of the device. Here we have revealed a low velocity, complex flow field with secondary, backward, or local recirculation micro-flows induced by the intricate architecture of the nichoid scaffold.

Conclusion: Knowledge of the microenvironment inside the 3D nichoids allows planning of cell experiments, to regulate the transport of cells towards the scaffold substrate during seeding or the spatial delivery of nutrients and oxygen which affects cell growth and viability.

Advanced 3D Cell Culture Techniques in Micro-Bioreactors, Part II: Systems and Applications

In this second part of our systematic review on the research area of 3D cell culture in micro-bioreactors we give a detailed description of the published work with regard to the existing micro-bioreactor types and their applications, and highlight important results gathered with the respective systems. As an interesting detail, we found that micro-bioreactors have already been used in SARS-CoV research prior to the SARS-CoV2 pandemic. As our literature research revealed a variety of 3D cell culture configurations in the examined bioreactor systems, we defined in review part one “complexity levels” by means of the corresponding 3D cell culture techniques applied in the systems. The definition of the complexity is thereby based on the knowledge that the spatial distribution of cell-extracellular matrix interactions and the spatial distribution of homologous and heterologous cell–cell contacts play an important role in modulating cell functions. Because at least one of these parameters can be assigned to the 3D cell culture techniques discussed in the present review, we structured the studies according to the complexity levels applied in the MBR systems.

Advanced 3D Cell Culture Techniques in Micro-Bioreactors, Part I: A Systematic Analysis of the Literature Published between 2000 and 2020

Bioreactors have proven useful for a vast amount of applications. Besides classical large-scale bioreactors and fermenters for prokaryotic and eukaryotic organisms, micro-bioreactors, as specialized bioreactor systems, have become an invaluable tool for mammalian 3D cell cultures. In this systematic review we analyze the literature in the field of eukaryotic 3D cell culture in micro-bioreactors within the last 20 years. For this, we define complexity levels with regard to the cellular 3D microenvironment concerning cell–matrix-contact, cell–cell-contact and the number of different cell types present at the same time. Moreover, we examine the data with regard to the micro-bioreactor design including mode of cell stimulation/nutrient supply and materials used for the micro-bioreactors, the corresponding 3D cell culture techniques and the related cellular microenvironment, the cell types and in vitro models used. As a data source we used the National Library of Medicine and analyzed the studies published from 2000 to 2020.

Bioengineering tools to speed up the discovery and preclinical testing of vaccines for SARS-CoV-2 and therapeutic agents for COVID-19

This review provides an update for the international research community on the cell modeling tools that could accelerate the understanding of SARS-CoV-2 infection mechanisms and could thus speed up the development of vaccines and therapeutic agents against COVID-19. Many bioengineering groups are actively developing frontier tools that are capable of providing realistic three-dimensional (3D) models for biological research, including cell culture scaffolds, microfluidic chambers for the culture of tissue equivalents and organoids, and implantable windows for intravital imaging. Here, we review the most innovative study models based on these bioengineering tools in the context of virology and vaccinology. To make it easier for scientists working on SARS-CoV-2 to identify and apply specific tools, we discuss how they could accelerate the discovery and preclinical development of antiviral drugs and vaccines, compared to conventional models.

Organ-On-A-Chip in vitro Models of the Brain and the Blood-Brain Barrier and Their Value to Study the Microbiota-Gut-Brain Axis in Neurodegeneration

We are accumulating evidence that intestinal microflora, collectively named gut microbiota, can alter brain pathophysiology, but researchers have just begun to discover the mechanisms of this bidirectional connection (often referred to as microbiota-gut-brain axis, MGBA). The most noticeable hypothesis for a pathological action of gut microbiota on the brain is based on microbial release of soluble neurotransmitters, hormones, immune molecules and neuroactive metabolites, but this complex scenario requires reliable and controllable tools for its causal demonstration. Thanks to three-dimensional (3D) cultures and microfluidics, engineered in vitro models could improve the scientific knowledge in this field, also from a therapeutic perspective. This review briefly retraces the main discoveries linking the activity of gut microbiota to prevalent brain neurodegenerative disorders, and then provides a deep insight into the state-of-the-art for in vitro modeling of the brain and the blood-brain barrier (BBB), two key players of the MGBA. Several brain and BBB microfluidic devices have already been developed to implement organ-on-a-chip solutions, but some limitations still exist. Future developments of organ-on-a-chip tools to model the MGBA will require an interdisciplinary approach and the synergy with cutting-edge technologies (for instance, bioprinting) to achieve multi-organ platforms and support basic research, also for the development of new therapies against neurodegenerative diseases.

A miniaturized hydrogel-based in vitro model for dynamic culturing of human cells overexpressing beta-amyloid precursor protein

Recent findings have highlighted an interconnection between intestinal microbiota and the brain, referred to as microbiota-gut-brain axis, and suggested that alterations in microbiota composition might affect brain functioning, also in Alzheimer's disease. To investigate microbiota-gut-brain axis biochemical pathways, in this work we developed an innovative device to be used as modular unit in an engineered multi-organ-on-a-chip platform recapitulating in vitro the main players of the microbiota-gut-brain axis, and an innovative three-dimensional model of brain cells based on collagen/hyaluronic acid or collagen/poly(ethylene glycol) semi-interpenetrating polymer networks and β-amyloid precursor protein-Swedish mutant-expressing H4 cells, to simulate the pathological scenario of Alzheimer's disease. We set up the culturing conditions, assessed cell response, scaled down the three-dimensional models to be hosted in the organ-on-a-chip device, and cultured them both in static and in dynamic conditions. The results suggest that the device and three-dimensional models are exploitable for advanced engineered models representing brain features also in Alzheimer's disease scenario.

Advanced Organ-on-a-Chip Devices to Investigate Liver Multi-Organ Communication: Focus on Gut, Microbiota and Brain

The liver is a key organ that can communicate with many other districts of the human body. In the last few decades, much interest has focused on the interaction between the liver and the gut microbiota, with their reciprocal influence on biosynthesis pathways and the integrity the intestinal epithelial barrier. Dysbiosis or liver disorders lead to0 epithelial barrier dysfunction, altering membrane permeability to toxins. Clinical and experimental evidence shows that the permeability hence the delivery of neurotoxins such as LPS, ammonia and salsolinol contribute to neurological disorders. These findings suggested multi-organ communication between the gut microbiota, the liver and the brain. With a view to in vitro modeling this liver-based multi-organ communication, we describe the latest advanced liver-on-a-chip devices and discuss the need for new organ-on-a-chip platforms for in vitro modeling the in vivo multi-organ connection pathways in physiological and pathological situations.

Combined Treatment with Three Natural Antioxidants Enhances Neuroprotection in a SH-SY5Y 3D Culture Model

Currently, the majority of cell-based studies on neurodegeneration are carried out on two-dimensional cultured cells that do not represent the cells residing in the complex microenvironment of the brain. Recent evidence has suggested that three-dimensional (3D) in vitro microenvironments may better model key features of brain tissues in order to study molecular mechanisms at the base of neurodegeneration. So far, no drugs have been discovered to prevent or halt the progression of neurodegenerative disorders. New therapeutic interventions can come from phytochemicals that have a broad spectrum of biological activities. On this basis, we evaluated the neuroprotective effect of three phytochemicals (sulforaphane, epigallocatechin gallate, and plumbagin) alone or in combination, focusing on their ability to counteract oxidative stress. The combined treatment was found to be more effective than the single treatments. In particular, the combined treatment increased cell viability and reduced glutathione (GSH) levels, upregulated antioxidant enzymes and insulin-degrading enzymes, and downregulated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 1 and 2 in respect to peroxide-treated cells. Our data suggest that a combination of different phytochemicals could be more effective than a single compound in counteracting neurodegeneration, probably thanks to a pleiotropic mechanism of action.

An Organ-On-A-Chip Engineered Platform to Study the Microbiota-Gut-Brain Axis in Neurodegeneration

After decades of research, the etiology of neurodegenerative disorders such as Alzheimer's or Parkinson's disease is still mostly unknown. Recent findings indicate that the microorganisms in the human gut might be involved in neurodegenerative pathways. Here, we discuss an innovative groundbreaking bioengineering approach that could make a difference in this intriguing scenario.

Assessing drug response in engineered brain microenvironments

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

Influence of the static magnetic field on cell response in a miniaturized optically accessible bioreactor for 3D cell culture

Hydraulic sealing is a crucial condition for the maintenance of sterility during long term operation of microfluidic bioreactors. We developed a miniaturized optically accessible bioreactor (MOAB) allowing perfused culture of 3D cellularised constructs. In the MOAB, the culture chambers are sealed by magnets that generate a weak static magnetic field (SMF). Here, we predicted computationally the exact level of SMF to which cells are subjected during culture in the MOAB and we assessed its influence on the viability, metabolic activity and gene expression of neuroblastoma-derived cells cultured up to seven days. The predicted SMF ranged from 0.32 to 0.57 T using an axial-symmetric model of a single chamber, whereas it ranged from 0.35 to 0.62 T using a 3D model of the complete device. Cell function was evaluated in SH-SY5Y neuroblastoma cells at 2 and 7 days of culture in the MOAB, compared to 2D monolayer, 3D non-perfused constructs, and 3D perfused constructs cultured in a modified MOAB with magnet-free sealing. We measured the cell metabolic activity normalized by the DNA content and the expression levels of heat-shock protein 70 (Hsp-70), Bcl-2 and Bax. We found that the level of SMF applied to cells in the MOAB did not influence their metabolic activity and exerted a stressful effect in 2D monolayer, not confirmed in 3D conditions, neither static not perfused. Instead, the magnets provided a significantly greater hydraulic sealing in long-term culture, thus the MOAB might be potentially exploitable for the development of reliable in vitro models of neurodegeneration.

Higher exosomal phosphorylated tau and total tau among veterans with combat-related repetitive chronic mild traumatic brain injury

OBJECTIVE

The objective of the study is to measure plasma and exosomal levels of tau, phosphorylated tau (p-tau), and amyloid beta (Aβ) in Veterans with historical mild traumatic brain injury (mTBI) and chronic neuropsychological symptoms.

METHODS

Tau, p-tau, Aβ40, and Aβ42 were measured by ultrasensitive immunoassay in plasma and exosomes from 195 Veterans enrolled in the Chronic Effects of Neurotrauma Consortium Multicenter Observational Study. Protein biomarkers were compared among groups with and without mTBI with loss of consciousness (LOC) or post-traumatic amnesia (PTA), and also in those with and without repetitive (≥3) mTBI (rTBI) compared to those with 0 (TBI-neg) and 1-2 mTBI.

RESULTS

There were no differences in measures of plasma and exosomal protein levels among mTBI with LOC or PTA, mTBI with alteration of consciousness only or TBI-neg. Exosomal tau and exosomal p-tau were elevated in rTBI compared to those with 2 or fewer mTBIs and TBI-neg (p < 0.05). Elevations of exosomal tau and p-tau significantly correlated with post-traumatic and post-concussive symptoms, with exosomal tau also relating specifically to cognitive, affective, and somatic post-concussive symptoms (p < 0.05).

CONCLUSION

rTBI is associated with elevations of exosomal p-tau and exosomal tau, suggesting that blood-based exosomes may provide a peripheral source of informative, centrally derived biomarkers in remote mTBI and that rTBI may contribute to chronic neuropsychological symptoms.

Exosomes in Acquired Neurological Disorders: New Insights into Pathophysiology and Treatment

Exosomes are endogenous nanovesicles that play critical roles in intercellular signaling by conveying functional genetic information and proteins between cells. Exosomes readily cross the blood-brain barrier and have promise as therapeutic delivery vehicles that have the potential to specifically deliver molecules to the central nervous system (CNS). This unique feature also makes exosomes attractive as biomarkers in diagnostics, prognostics, and therapeutics in the context of multiple significant public health conditions, including acquired neurological disorders. The purpose of this review is to summarize the state of the science surrounding the relevance of extracellular vesicles (EVs), particularly exosomes, to acquire neurological disorders, specifically traumatic brain injury (TBI), spinal cord injury (SCI), and ischemic stroke. In total, ten research articles were identified that examined exosomes in the context of TBI, SCI, or stroke; these manuscripts were reviewed and synthesized to further understand the current role of exosomes in the context of acquired neurological disorders. Of the ten published studies, four focused exclusively on TBI, one on both TBI and SCI, and five on ischemic stroke; notably, eight of the ten studies were limited to pre-clinical samples. The present review is the first to discuss the current body of knowledge surrounding the role of exosomes in the pathophysiology, diagnosis, and prognosis, as well as promising therapeutic strategies in TBI, SCI, and stroke research.

Spatiotemporal Image Correlation Analysis for 3D Flow Field Mapping in Microfluidic Devices

Microfluidic devices reproducing 3D networks are particularly valuable for nanomedicine applications such as tissue engineering and active cell sorting. There is however a gap in the possibility to measure how the flow evolves in such 3D structures. We show here that it is possible to map 3D flows in complex microchannel networks by combining wide field illumination to image correlation approaches. For this purpose, we have derived the spatiotemporal image correlation analysis of time stacks of single-plane illumination microscopy images. From the detailed analytical and numerical analysis of the resulting model, we developed a fitting method that allows us to measure, besides the in-plane velocity, the out-of-plane velocity component down to v_z ≅ 65 μm/s. We have applied this method successfully to the 3D reconstruction of flows in microchannel networks with planar and 3D ramifications. These different network architectures have been realized by exploiting the great prototyping ability of a 3D printer, whose precision can reach few tens of micrometers, coupled to poly dimethyl-siloxane soft-printing lithography.

Autologous intramuscular transplantation of engineered satellite cells induces exosome-mediated systemic expression of Fukutin-related protein and rescues disease phenotype in a murine model of limb-girdle muscular dystrophy type 2I

α-Dystroglycanopathies are a group of muscular dystrophies characterized by α-DG hypoglycosylation and reduced extracellular ligand-binding affinity. Among other genes involved in the α-DG glycosylation process, fukutin related protein (FKRP) gene mutations generate a wide range of pathologies from mild limb girdle muscular dystrophy 2I (LGMD2I), severe congenital muscular dystrophy 1C (MDC1C), to Walker-Warburg Syndrome and Muscle-Eye-Brain disease. FKRP gene encodes for a glycosyltransferase that in vivo transfers a ribitol phosphate group from a CDP –ribitol present in muscles to α-DG, while in vitro it can be secreted as monomer of 60kDa. Consistently, new evidences reported glycosyltransferases in the blood, freely circulating or wrapped within vesicles. Although the physiological function of blood stream glycosyltransferases remains unclear, they are likely released from blood borne or distant cells. Thus, we hypothesized that freely or wrapped FKRP might circulate as an extracellular glycosyltransferase, able to exert a “glycan remodelling” process, even at distal compartments. Interestingly, we firstly demonstrated a successful transduction of MDC1C blood-derived CD133+ cells and FKRP L276I^KI mouse derived satellite cells by a lentiviral vector expressing the wild-type of human FKRP gene. Moreover, we showed that LV-FKRP cells were driven to release exosomes carrying FKRP. Similarly, we observed the presence of FKRP positive exosomes in the plasma of FKRP L276I^KI mice intramuscularly injected with engineered satellite cells. The distribution of FKRP protein boosted by exosomes determined its restoration within muscle tissues, an overall recovery of α-DG glycosylation and improved muscle strength, suggesting a systemic supply of FKRP protein acting as glycosyltransferase.

Eumelanin Coated PLA Electrospun Micro Fibers as Bioinspired Cradle for SH-SY5Y Neuroblastoma Cells Growth and Maturation

Within the framework of neurodegenerative disorder therapies, the fabrication of 3D eumelanin architectures represents a novel strategy to realize tissue-engineering scaffolds for neuronal cell growth and control by providing both mechanical support and biological signals. Here, an appropriate procedure combining electrospinning, spin coating and solid-state polymerization process is established to realize the scaffolds. For biological analysis, a human derived cell line SH-SY5Y from neuroblastoma is used. Cell maturation on eumelanin microfibers, random and aligned, is evaluated by using confocal analysis and specific markers of differentiating neurons (βIII tubulin and GAP-43 expression). Cell morphology is tested by SEM analysis and immunofluorescence techniques. As results, eumelanin coated microfibers prove capable to support biological response in terms of cell survival, adhesion and spreading and to promote cell differentiation toward a more mature neuronal phenotype as confirmed by GAP-43 expression over the culture.

Secretome released from hydrogel-embedded adipose mesenchymal stem cells protects against the Parkinson's disease related toxin 6-hydroxydopamine

Neurodegenerative diseases, as Parkinson’s disease (PD), involve irreversible neural cell damage and impairment. In PD, there is a selective degeneration of the dopaminergic neurons leading to motor symptoms. A common finding in PD neurodegeneration is the increase of reactive oxygen species (ROS), leading to oxidative stress. To date there are only interventions to relieve PD symptoms, however progress has been made in the development of therapies that target the immune system or use its components as therapeutic agents; among these, mesenchymal stem cells (MSCs), which are able to express neuroprotective factors as cytokines, chemokines and angiogenic molecules, collectively named secretome, that accumulate in MSC culture medium. However, lasting cell-free administration of secretome in vitro or in vivo is challenging. We used the conditioned media from rat adipose tissue-derived MSCs (RAA-MSCs) to check for neuroprotective activity towards pro-oxidizing agents such as hydrogen peroxide (H₂O₂) or the dopaminergic selective toxin 6-hydroxydopamine (6-OHDA) that is commonly used to model PD neurodegeneration. When neuroblastoma SH-SY5Y cells were pre-conditioned with 100% RAA-MSC media, then treated with H₂O₂ and 6-OHDA, mortality and ROS generation were reduced. We implemented the controlled release of RAA-MSC secretome from injectable biodegradable hydrogels that offer a possible in situ implant with mini-invasive techniques. The hydrogels were composed of type I bovine collagen (COLL) and low-molecular-weight hyaluronic acid (LMWHA) or COLL and polyethylene glycol (PEG). Hydrogels were suitable for RAA-MSC embedding up to 48 h and secretome from these RAA-MSCs was active and counteracted 6-OHDA toxicity, with upregulation of the antioxidant enzyme sirtuin 3 (SIRT3). These results support a biomaterials-based approach for controlled delivery of MSC-produced neuroprotective factors in a PD-relevant experimental context.

Adapting tissue-engineered in vitro CNS models for high-throughput study of neurodegeneration

Neurodegenerative conditions remain difficult to treat, with the continuing failure to see therapeutic research successfully advance to clinical trials. One of the obstacles that must be overcome is to develop enhanced models of disease. Tissue engineering techniques enable us to create organised artificial central nervous system tissue that has the potential to improve the drug development process. This study presents a replicable model of neurodegenerative pathology through the use of engineered neural tissue co-cultures that can incorporate cells from various sources and allow degeneration and protection of neurons to be observed easily and measured, following exposure to neurotoxic compounds – okadaic acid and 1-methyl-4-phenylpyridinium. Furthermore, the technology has been miniaturised through development of a mould with 6 mm length that recreates the advantageous features of engineered neural tissue co-cultures at a scale suitable for commercial research and development. Integration of human-derived induced pluripotent stem cells aids more accurate modelling of human diseases, creating new possibilities for engineered neural tissue co-cultures and their use in drug screening.

Bioengineered 3D Glial Cell Culture Systems and Applications for Neurodegeneration and Neuroinflammation

Neurodegeneration and neuroinflammation are key features in a range of chronic central nervous system (CNS) diseases such as Alzheimer's and Parkinson's disease, as well as acute conditions like stroke and traumatic brain injury, for which there remains significant unmet clinical need. It is now well recognized that current cell culture methodologies are limited in their ability to recapitulate the cellular environment that is present in vivo, and there is a growing body of evidence to show that three-dimensional (3D) culture systems represent a more physiologically accurate model than traditional two-dimensional (2D) cultures. Given the complexity of the environment from which cells originate, and their various cell-cell and cell-matrix interactions, it is important to develop models that can be controlled and reproducible for drug discovery. 3D cell models have now been developed for almost all CNS cell types, including neurons, astrocytes, microglia, and oligodendrocyte cells. This review will highlight a number of current and emerging techniques for the culture of astrocytes and microglia, glial cell types with a critical role in neurodegenerative and neuroinflammatory conditions. We describe recent advances in glial cell culture using electrospun polymers and hydrogel macromolecules, and highlight how these novel culture environments influence astrocyte and microglial phenotypes in vitro, as compared to traditional 2D systems. These models will be explored to illuminate current trends in the techniques used to create 3D environments for application in research and drug discovery focused on astrocytes and microglial cells.