Enhancement of renal epithelial cell functions through microfluidic-based coculture with adipose-derived stem cells

Standalone cell culture microfluidic device-based microphysiological system for automated cell observation and application in nephrotoxicity tests

Microphysiological systems (MPS) offer an alternative method for culturing cells on microfluidic platforms to model organ functions in pharmaceutical and medical sciences. Although MPS hardware has been proposed to maintain physiological organ function through perfusion culture, no existing MPS can automatically assess cell morphology and conditions online to observe cellular dynamics in detail. Thus, with this study, we aimed to establish a practical strategy for automating cell observation and improving cell evaluation functions with low temporal resolution and throughput in MPS experiments. We developed a versatile standalone cell culture microfluidic device (SCCMD) that integrates microfluidic chips and their peripherals. This device is compliant with the ANSI/SLAS standards and has been seamlessly integrated into an existing automatic cell imaging system. This integration enables automatic cell observation with high temporal resolution in MPS experiments. Perfusion culture of human kidney proximal tubule epithelial cells using the SCCMD improves cell function. By combining the proximal tubule MPS with an existing cell imaging system, nephrotoxicity studies were successfully performed to automate morphological and material permeability evaluation. We believe that the concept of building the ANSI/SLAS-compliant-sized MPS device proposed herein and integrating it into an existing automatic cell imaging system for the online measurement of detailed cell dynamics information and improvement of throughput by automating observation operations is a novel potential research direction for MPS research.

Application of microfluidic chips in the simulation of the urinary system microenvironment

The urinary system, comprising the kidneys, ureters, bladder, and urethra, has a unique mechanical and fluid microenvironment, which is essential to the urinary system growth and development. Microfluidic models, based on micromachining and tissue engineering technology, can integrate pathophysiological characteristics, maintain cell-cell and cell-extracellular matrix interactions, and accurately simulate the vital characteristics of human tissue microenvironments. Additionally, these models facilitate improved visualization and integration and meet the requirements of the laminar flow environment of the urinary system. However, several challenges continue to impede the development of a tissue microenvironment with controllable conditions closely resemble physiological conditions. In this review, we describe the biochemical and physical microenvironment of the urinary system and explore the feasibility of microfluidic technology in simulating the urinary microenvironment and pathophysiological characteristics in vitro. Moreover, we summarize the current research progress on adapting microfluidic chips for constructing the urinary microenvironment. Finally, we discuss the current challenges and suggest directions for future development and application of microfluidic technology in constructing the urinary microenvironment in vitro.

Cultivating human tissues and organs over lab-on-a-chip models: Recent progress and applications

In vivo models are indispensable for preclinical studies for various human disease modeling and drug screening, however, face several obstacles such as animal model species differences and ethical clearance. Additionally, it is difficult to accurately predict the organ interaction, drug efficacy, and toxicity using conventional in vitro two-dimensional (2D) cell culture models. The microfluidic-based systems provide excellent opportunity to recapitulate the human organ/tissue functions under in vitro conditions. The organ/tissue-on-chip models are one of best emerging technologies that offer functional organs/tissues on a microfluidic chip. This technology has potential to noninvasively study the organ physiology, tissue development, and diseases etymology. This chapter comprises the benifits of 2D and three-dimensional (3D) in vitro cultures as well as highlights the importance of microfluidic-based lab-on-a-chip technique. The development of different organs/tissues-on-chip models and their biomedical application in various diseases such as cardiovascular diseases, neurodegenerative diseases, respiratory-based diseases, cancers, liver and kidney diseases, etc., have also been discussed.

Environmental Toxicology Assays Using Organ-on-Chip

Adverse effects of environmental toxicants to human health have traditionally been assayed using in vitro assays. Organ-on-chip (OOC) is a new platform that can bridge the gaps between in vitro assays (or 3D cell culture) and animal tests. Microenvironments, physical and biochemical stimuli, and adequate sensing and biosensing systems can be integrated into OOC devices to better recapitulate the in vivo tissue and organ behavior and metabolism. While OOCs have extensively been studied for drug toxicity screening, their implementation in environmental toxicology assays is minimal and has limitations. In this review, recent attempts of environmental toxicology assays using OOCs, including multiple-organs-on-chip, are summarized and compared with OOC-based drug toxicity screening. Requirements for further improvements are identified and potential solutions are suggested.

A Decade of Organs-on-a-Chip Emulating Human Physiology at the Microscale: A Critical Status Report on Progress in Toxicology and Pharmacology

Organ-on-a-chip technology has the potential to accelerate pharmaceutical drug development, improve the clinical translation of basic research, and provide personalized intervention strategies. In the last decade, big pharma has engaged in many academic research cooperations to develop organ-on-a-chip systems for future drug discoveries. Although most organ-on-a-chip systems present proof-of-concept studies, miniaturized organ systems still need to demonstrate translational relevance and predictive power in clinical and pharmaceutical settings. This review explores whether microfluidic technology succeeded in paving the way for developing physiologically relevant human in vitro models for pharmacology and toxicology in biomedical research within the last decade. Individual organ-on-a-chip systems are discussed, focusing on relevant applications and highlighting their ability to tackle current challenges in pharmacological research.

Novel Assay Analyzing Tropism between Adipose-Derived Stem Cells and Breast Cancer Cells Reveals a Low Oncogenic Response

Introduction

In the surgical world of breast cancer reconstruction, fat grafting is commonly viewed as an oncogenic risk. Scientific studies add confusion, given the stark lack of clinical evidence suggesting pro-oncogenic links. Typically, classic migration assays (e.g., Boyden chamber) between adipose-derived stem cells and breast cancer cells define this cell relationship as pro-oncogenic.

Objective

We sought to develop a new migration model which better explains existing clinical data.

Methods

Silicon chambers were used to seed isolated populations of cells simultaneously in culture dish. Once cells had adhered, chambers were removed and cells were allowed to follow natural trophic cues. Multiple permutations of MDA-MB-231, MCF-7, HS-27, and ASCs were engineered. Cells were stained with MitoTracker for fluorescent visualization. A human cytokine array (RayBiotech) was performed on the media of migrating assays. Cellular tropism and blot intensity were quantitatively measured in Image J.

Results

An in vitro model was successfully constructed where ASCs reproducibly and freely migrated. Cytokine arrays reveal higher levels of IL-6 and CCL2 in the media of Boyden chambers containing ASCs and MDA-MB-231, compared to the novel assay, comprised of the same cell numbers, types, and incubation times.

Conclusion

These data collectively show for the first time the attraction of ASCs to malignant breast cancer cells; a phenomenon which many ASC studies infer. The cytokine profile of the novel system described is less oncogenic than the commonly described Boyden chamber. These data integrate better into the clinical data, which fail to link cancer recurrence with fat grafting.

Effect of fluid shear stress on in vitro cultured ureteric bud cells

Most kidney cells are continuously exposed to fluid shear stress (FSS) from either blood flow or urine flow. Recent studies suggest that changes in FSS could contribute to the function and injury of these kidney cells. However, it is unclear whether FSS influences kidney development when urinary flow starts in the embryonic kidneys. In this study, we evaluated the influence of FSS on in vitro cultured ureteric bud (UB) cells by using a pumpless microfluidic device, which offers the convenience of conducting parallel cell culture experiments while also eliminating the need for cumbersome electronic driven equipment and intricate techniques. We first validated the function of the device by both mathematical model and experimental measurements. UB cells dissected from E15.5 mouse embryonic kidneys were cultured in the pumpless microfluidic device and subjected to FSS in the range of 0.4-0.6 dyn mm-2 for 48 h (dynamic). Control UB cells were similarly cultured in the device and maintained under a no-flow condition (static). We found from our present study that the exposure to FSS for up to 48 h led to an increase in mRNA expression levels of UB tip cell marker genes (Wnt11, Ret, Etv4) with a decrease in stalk cell marker genes (Wnt7b, Tacstd2). In further support of the enrichment of UB tip cell population in response to FSS, we also found that exposure to FSS led to a remarkable reduction in the binding of lectin Dolichos Biflorus Agglutinin. In conclusion, results of our present study show that exposure to FSS led to an enrichment in UB tip cell populations, which could contribute to the development and function of the embryonic kidney when urine flow starts at around embryonic age E15.5 in mouse. Since UB tip cells are known to be the proliferative progenitor cells that contribute to the branching morphogenesis of the collecting system in the kidney, our finding could imply an important link between the FSS from the initiation of urine flow and the development and function of the kidney.

Multilineage Constructs for Scaffold-Based Tissue Engineering: A Review of Tissue-Specific Challenges

There is a growing interest in the regeneration of tissue in interfacial regions, where biological, physical, and chemical attributes vary across tissue type. The simultaneous use of distinct cell lineages can help in developing in vitro structures, analogous to native composite tissues. This literature review gathers the recent reports that have investigated multiple cell types of various sources and lineages in a coculture system for tissue-engineered constructs. Such studies aim at mimicking the native organization of tissues and their interfaces, and/or to improve the development of complex tissue substitutes. This paper thus distinguishes itself from those focusing on technical aspects of coculturing for a single specific tissue. The first part of this review is dedicated to variables of cocultured tissue engineering such as scaffold, cells, and in vitro culture environment. Next, tissue-specific coculture methods and approaches are covered for the most studied tissues. Finally, cross-analysis is performed to highlight emerging trends in coculture principles and to discuss how tissue-specific challenges can inspire new approaches for regeneration of different interfaces to improve the outcomes of various tissue engineering strategies.

Organ-On-A-Chip Platforms: A Convergence of Advanced Materials, Cells, and Microscale Technologies

Significant advances in biomaterials, stem cell biology, and microscale technologies have enabled the fabrication of biologically relevant tissues and organs. Such tissues and organs, referred to as organ-on-a-chip (OOC) platforms, have emerged as a powerful tool in tissue analysis and disease modeling for biological and pharmacological applications. A variety of biomaterials are used in tissue fabrication providing multiple biological, structural, and mechanical cues in the regulation of cell behavior and tissue morphogenesis. Cells derived from humans enable the fabrication of personalized OOC platforms. Microscale technologies are specifically helpful in providing physiological microenvironments for tissues and organs. In this review, biomaterials, cells, and microscale technologies are described as essential components to construct OOC platforms. The latest developments in OOC platforms (e.g., liver, skeletal muscle, cardiac, cancer, lung, skin, bone, and brain) are then discussed as functional tools in simulating human physiology and metabolism. Future perspectives and major challenges in the development of OOC platforms toward accelerating clinical studies of drug discovery are finally highlighted.

Organ/body-on-a-chip based on microfluidic technology for drug discovery

Although animal experiments are indispensable for preclinical screening in the drug discovery process, various issues such as ethical considerations and species differences remain. To solve these issues, cell-based assays using human-derived cells have been actively pursued. However, it remains difficult to accurately predict drug efficacy, toxicity, and organs interactions, because cultivated cells often do not retain their original organ functions and morphologies in conventional in vitro cell culture systems. In the μTAS research field, which is a part of biochemical engineering, the technologies of organ-on-a-chip, based on microfluidic devices built using microfabrication, have been widely studied recently as a novel in vitro organ model. Since it is possible to physically and chemically mimic the in vitro environment by using microfluidic device technology, maintenance of cellular function and morphology, and replication of organ interactions can be realized using organ-on-a-chip devices. So far, functions of various organs and tissues, such as the lung, liver, kidney, and gut have been reproduced as in vitro models. Furthermore, a body-on-a-chip, integrating multi organ functions on a microfluidic device, has also been proposed for prediction of organ interactions. We herein provide a background of microfluidic systems, organ-on-a-chip, Body-on-a-chip technologies, and their challenges in the future.

A microfluidic renal proximal tubule with active reabsorptive function

In the kidney, the renal proximal tubule (PT) reabsorbs solutes into the peritubular capillaries through active transport. Here, we replicate this reabsorptive function in vitro by engineering a microfluidic PT. The microfluidic PT architecture comprises a porous membrane with user-defined submicron surface topography separating two microchannels representing a PT filtrate lumen and a peritubular capillary lumen. Human PT epithelial cells and microvascular endothelial cells in respective microchannels created a PT-like reabsorptive barrier. Co-culturing epithelial and endothelial cells in the microfluidic architecture enhanced viability, metabolic activity, and compactness of the epithelial layer. The resulting tissue expressed tight junctions, kidney-specific morphology, and polarized expression of kidney markers. The microfluidic PT actively performed sodium-coupled glucose transport, which could be modulated by administration of a sodium-transport inhibiting drug. The microfluidic PT reproduces human physiology at the cellular and tissue levels, and measurable tissue function which can quantify kidney pharmaceutical efficacy and toxicity.

Organs-on-a-chip

In the last few years, considerable attention has been given to in vitro models in an attempt to reduce the use of animals and to decrease the rate of preclinical failure associated with the development of new drugs. Simple two-dimensional cultures grown in a dish are now frequently replaced by organotypic cultures with three-dimensional (3-D) architecture, which enables interactions between cells, promoting their differentiation and increasing their in vivo likeness. Microengineering now enables the incorporation of small devices into 3-D culture models to reproduce the complex microenvironment of the modeled organ, often referred to as organs-on-a-chip (OoCs). This review describes various OoCs developed to mimic liver, brain, kidney, and lung tissues. Current challenges encountered in attempts to recreate the in vivo environment are described, as well as some examples of OoCs. Finally, attention is given to the ongoing evolution of OoCs with the aim of solving one of the major limitations in that they can only represent a single organ. Multi-organ-on-a-chip (MOC) systems mimic organ interactions observed in the human body and aim to provide the features of compound uptake, metabolism, and excretion, while simultaneously allowing for insights into biological effects. MOCs might therefore represent a new paradigm in drug development, providing a better understanding of dose responses and mechanisms of toxicity, enabling the detection of drug resistance and supporting the evaluation of pharmacokinetic–pharmacodynamics parameters.

The microbiota and autoimmunity: Their role in thyroid autoimmune diseases

Since the 1970s, the role of infectious diseases in the pathogenesis of Graves' disease (GD) has been an object of intensive research. The last decade has witnessed many studies on Yersinia enterocolitica, Helicobacter pylori and other bacterial organisms and their potential impact on GD. Retrospective, prospective and molecular binding studies have been performed with contrary outcomes. Until now it is not clear whether bacterial infections can trigger autoimmune thyroid disease. Common risk factors for GD (gender, smoking, stress, and pregnancy) reveal profound changes in the bacterial communities of the gut compared to that of healthy controls but a pathogenetic link between GD and dysbiosis has not yet been fully elucidated. Conventional bacterial culture, in vitro models, next generation and high-throughput DNA sequencing are applicable methods to assess the impact of bacteria in disease onset and development. Further studies on the involvement of bacteria in GD are needed and may contribute to the understanding of pathogenetic processes. This review will examine available evidence on the subject.

Assessment of cadmium-induced nephrotoxicity using a kidney-on-a-chip device

Cadmium (Cd) is a common environmental pollutant. Its effects on human health have attracted great attention. The kidney is the organ that is the most affected by Cd exposure. Thus, it is highly desirable to develop a reliable model to evaluate Cd-induced nephrotoxicity in vitro. We present a kidney-on-a-chip with three compartmentalized culture chambers to examine Cd-induced nephrotoxicity. The culture and collection channels represent the capillary and the glomerular capsule sides of the glomerular filtration barrier, respectively. Isolated primary rat glomerular endothelial cells (GECs) were cultured on the side surface of the middle gel channel. The integrated GEC layer demonstrated the selective permeability of the renal barrier. Therefore, it was further utilized to study the nephrotoxicity induced by Cd exposure at different concentrations. Cd induced significant cytotoxicity and disrupted the expression of tight junction protein ZO-1 in a dose-dependent manner. Moreover, Cd exposure increased the permeability of the endothelial layer to large molecules, immunoglobulin G and albumin. These results facilitate the understanding of the underlying mechanism of kidney dysfunction and glomerular disease. This is the first study on Cd-induced nephrotoxicity using primary GECs in a microfluidic device. The kidney-on-a-chip device enables direct visualization and quantitative analysis of GEC responses to Cd in real time. It may provide a micro-scale platform based on the human system for nephrotoxicity testing under varying environmental exposure.

Assembling Composite Dermal Papilla Spheres with Adipose-derived Stem Cells to Enhance Hair Follicle Induction

Intradermal adipose tissue plays an essential role for hair follicles (HFs) regeneration by regulating hair cycles. However, the effect of reconstruction of HFs and the involvement of adipose-related cells are poorly understood. We investigated assembly strategies for the interactions of dermal papilla (DP) cells with adipose-derived stem cells (ASCs) in promoting hair formation. DP cells lose DP traits during adherent culture, but preserved DP markers with a unified sphere diameter by seeding on chitosan-coated microenvironments. Next, ASCs isolated from rats were co-cultured with DP spheres by different assembling approaches to determine their interactions; a mixed sphere of ASCs with DP cells (MA-DPS), or a core-shell structure, outer ASCs shell and an inner DP core (CSA-DPS). CSA-DPS exhibited superior DP characteristics compared to MA-DPS. Conditional medium from ASCs, but not differentiated adipocytes, promoted DP markers and functional alkaline phosphatase activity from the DP cells. In vivo patch assay showed the core-shell assembling of CSA-DPS can reconstruct cellular arrangements and microenvironmental niches as dominated by PPARα signal in ASCs to induce the greater hair induction than MA-DPS or DP spheres alone. Therefore, the assembling of a core-shell sphere for DP with ASCs could reconstruct the HF cellular arrangement for hair formation. This paper set the groundwork for further evaluation of the input of other cell types.

Biology-inspired microphysiological system approaches to solve the prediction dilemma of substance testing

The recent advent of microphysiological systems - microfluidic biomimetic devices that aspire to emulate the biology of human tissues, organs and circulation in vitro - is envisaged to enable a global paradigm shift in drug development. An extraordinary US governmental initiative and various dedicated research programs in Europe and Asia have led recently to the first cutting-edge achievements of human single-organ and multi-organ engineering based on microphysiological systems. The expectation is that test systems established on this basis would model various disease stages, and predict toxicity, immunogenicity, ADME profiles and treatment efficacy prior to clinical testing. Consequently, this technology could significantly affect the way drug substances are developed in the future. Furthermore, microphysiological system-based assays may revolutionize our current global programs of prioritization of hazard characterization for any new substances to be used, for example, in agriculture, food, ecosystems or cosmetics, thus, replacing laboratory animal models used currently. Thirty-six experts from academia, industry and regulatory bodies present here the results of an intensive workshop (held in June 2015, Berlin, Germany). They review the status quo of microphysiological systems available today against industry needs, and assess the broad variety of approaches with fit-for-purpose potential in the drug development cycle. Feasible technical solutions to reach the next levels of human biology in vitro are proposed. Furthermore, key organ-on-a-chip case studies, as well as various national and international programs are highlighted. Finally, a roadmap into the future is outlined, to allow for more predictive and regulatory-accepted substance testing on a global scale.

Tissue Inhibitor of Matrix Metalloproteinases-1 Knockdown Suppresses the Proliferation of Human Adipose-Derived Stem Cells

Tissue inhibitor of metalloproteinases-1 (TIMP-1) is a multifunctional matrix metalloproteinase, and it is involved in the regulation of cell proliferation and apoptosis in various cell types. However, little is known about the effect of TIMP-1 expression on the proliferation of adipose-derived stem cells (ADSCs). Therefore, TIMP-1 expression in the ADSCs was firstly detected by western blotting, and TIMP-1 gene was knocked down by lentivirus-mediated shRNA. Cell proliferation was then evaluated by MTT assay and Ki67 staining, respectively. Cell cycle progression was determined by flow cytometry. The changes of p51, p21, cyclin E, cyclin-dependent kinase 2 (CDK2), and P-CDK2 caused by TIMP-1 knockdown were detected by western blotting. The results indicated that ADSCs highly expressed TIMP-1 protein, and the knockdown of TIMP-1 inhibited cell proliferation and arrested cell cycle progression at G₁ phase in the ADSCs possibly through the upregulation of p53, p21, and P-CDK2 protein levels and concurrent downregulation of cyclin E and CDK2 protein levels. These findings suggest that TIMP-1 works as a positive regulator of cell proliferation in ADSCs.

A Role for 3D Printing in Kidney-on-a-Chip Platforms

The advancement of "kidney-on-a-chip" platforms - submillimeter-scale fluidic systems designed to recapitulate renal functions in vitro - directly impacts a wide range of biomedical fields, including drug screening, cell and tissue engineering, toxicity testing, and disease modelling. To fabricate kidney-on-a-chip technologies, researchers have primarily adapted traditional micromachining techniques that are rooted in the integrated circuit industry; hence the term, "chip." A significant challenge, however, is that such methods are inherently monolithic, which limits one's ability to accurately recreate the geometric and architectural complexity of the kidney in vivo. Better reproduction of the anatomical complexity of the kidney will allow for more instructive modelling of physiological and pathophysiological events. Emerging additive manufacturing or "three-dimensional (3D) printing" techniques could provide a promising alternative to conventional methodologies. In this article, we discuss recent progress in the development of both kidney-on-a-chip platforms and state-of-the-art submillimeter-scale 3D printing methods, with a focus on biophysical and architectural capabilities. Lastly, we examine the potential for 3D printing-based approaches to extend the efficacy of kidney-on-a-chip systems.

Microfluidic Organ/Body-on-a-Chip Devices at the Convergence of Biology and Microengineering

Recent advances in biomedical technologies are mostly related to the convergence of biology with microengineering. For instance, microfluidic devices are now commonly found in most research centers, clinics and hospitals, contributing to more accurate studies and therapies as powerful tools for drug delivery, monitoring of specific analytes, and medical diagnostics. Most remarkably, integration of cellularized constructs within microengineered platforms has enabled the recapitulation of the physiological and pathological conditions of complex tissues and organs. The so-called “organ-on-a-chip” technology, which represents a new avenue in the field of advanced in vitro models, with the potential to revolutionize current approaches to drug screening and toxicology studies. This review aims to highlight recent advances of microfluidic-based devices towards a body-on-a-chip concept, exploring their technology and broad applications in the biomedical field.

Human adipose-derived mesenchymal stem cells repair cisplatin-induced acute kidney injury through antiapoptotic pathways

Cisplatin has been hypothesized to induce nephrotoxicity through triggering the apoptosis of tubular cells; however, the drug remains widely administered for the treatment of tumors. Recently, mesenchymal stem cells (MSCs) have been demonstrated to protect the kidney from the adverse effects induced by cisplatin. The aim of the present study was to investigate the mechanisms underlying the protective effects of human adipose-derived MSCs (AD-MSCs) on kidney function and tubular cells. Sprague-Dawley rats were divided into three groups, which included the healthy controls, those subjected to cisplatin-induced acute kidney injury (AKI) for 24 h without subsequent treatment and those subjected to cisplatin-induced AKI for 24 h, followed by AD-MSC engraftment. The rats were sacrificed at day 5 and the effects were analyzed using various methods, including biochemical analysis, structural examination and cell tracking experiments. In addition, an in vitro experiment with NRK-52E cells was performed. The cells were divided into three groups, including the healthy control, cisplatin induction and cisplatin induction with co-culture of AD-MSCs, and were subsequently assessed with a Transwell assay. After culture for four days, the cells were lysed and the total protein extract was subjected to western blot analysis. Cisplatin-induced renal dysfunction and tissue damage was shown to recover following AD-MSC infusion, although there were few AD-MSCs observed around the injured kidney tubules in the kidney. When the cisplatin-treated NRK-52E cells were co-cultured with AD-MSCs, the activation of p38 and BAX were inhibited, while the expression of Bcl-2 was upregulated, as compared with the cisplatin-treated NRK-52E cells that were not co-cultured. Therefore, AD-MSCs were shown to markedly improve cisplatin-induced renal failure and tubular cells necrosis through the secretion of certain factors, which subsequently inhibited the apoptosis pathway in vitro. It was hypothesized that AD-MSC secretion was triggered by the injured tubular cells. Thus, AD-MSCs may be important for the therapy of patients with renal injury due to their antiapoptotic capacity.

Microfluidic Organ-on-a-Chip Technology for Advancement of Drug Development and Toxicology

In recent years, the exploitation of phenomena surrounding microfluidics has seen an increase in popularity, as researchers have found a way to use their unique properties to create superior design alternatives. One such application is representing the properties and functions of different organs on a microscale chip for the purpose of drug testing or tissue engineering. With the introduction of "organ-on-a-chip" systems, researchers have proposed various methods on various organ-on-a-chip systems to mimic their in vivo counterparts. In this article, a systematic approach is taken to review current technologies pertaining to organ-on-a-chip systems. Design processes with attention to the particular instruments, cells, and materials used are presented.

Microfluidic 3D cell culture: from tools to tissue models

The transition from 2D to 3D cell culture techniques is an important step in a trend towards better biomimetic tissue models. Microfluidics allows spatial control over fluids in micrometer-sized channels has become a valuable tool to further increase the physiological relevance of 3D cell culture by enabling spatially controlled co-cultures, perfusion flow and spatial control over of signaling gradients. This paper reviews most important developments in microfluidic 3D culture since 2012. Most efforts were exerted in the field of vasculature, both as a tissue on its own and as part of cancer models. We observe that the focus is shifting from tool building to implementation of specific tissue models. The next big challenge for the field is the full validation of these models and subsequently the implementation of these models in drug development pipelines of the pharmaceutical industry and ultimately in personalized medicine applications.

Lab-on-a-chip technologies for stem cell analysis

The combination of microfabrication-based technologies with cell biology has laid the foundation for the development of advanced in vitro diagnostic systems capable of analyzing cell cultures under physiologically relevant conditions. In the present review, we address recent lab-on-a-chip developments for stem cell analysis. We highlight in particular the tangible advantages of microfluidic devices to overcome most of the challenges associated with stem cell identification, expansion and differentiation, with the greatest advantage being that lab-on-a-chip technology allows for the precise regulation of culturing conditions, while simultaneously monitoring relevant parameters using embedded sensory systems. State-of-the-art lab-on-a-chip platforms for in vitro assessment of stem cell cultures are presented and their potential future applications discussed.