Microfluidic Cell Culture Systems

Jeffrey T Borenstein, Vishal Tandon, Sarah L Tao, Joseph L. Charest

• Publisher: Elsevier
• Year: 2018
• eBook ISBN: 9780128136720
• Edition: 2
• Topic: Sciences physiques
• Subtopic: Nanotechnologie

Techniques for microfabricating intricate microfluidic structures that mimic the microenvironment of tissues and organs, combined with the development of biomaterials with carefully engineered surface properties, have enabled new paradigms in and cell culture-based models for human diseases. The dimensions of surface features and fluidic channels made accessible by these techniques are well-suited to the size scale of biological cells. Microfluidic Cell Culture Systems applies design and experimental techniques used in in microfluidics, and cell culture technologies to organ-on-chip systems.This book is intended to serve as a professional reference, providing a practical guide to design and fabrication of microfluidic systems and biomaterials for use in cell culture systems and human organ models. The book covers topics ranging from academic first principles of microfluidic design, to clinical translation strategies for cell culture protocols. The goal is to help professionals coming from an engineering background to adapt their expertise for use in cell culture and organ models applications, and likewise to help biologists to design and employ microfluidic technologies in their cell culture systems.This 2nd edition contains new material that strengthens the focus on in vitro models useful for drug discovery and development. One new chapter reviews liver organ models from an industry perspective, while others cover new technologies for scaling these models and for multi-organ systems. Other new chapters highlight the development of organ models and systems for specific applications in disease modeling and drug safety. Previous chapters have been revised to reflect the latest advances.- Provides design and operation methodology for microfluidic and microfabricated materials and devices for organ-on-chip disease and safety models. This is a rapidly expanding field that will continue to grow along with advances in cell biology and microfluidics technologies.- Comprehensively covers strategies and techniques ranging from academic first principles to industrial scale-up approaches. Readers will gain insight into cell-material interactions, microfluidic flow, and design principles.- Offers three fundamental types of information: 1) design principles, 2) operation techniques, and 3) background information/perspectives. The book is carefully designed to strike a balance between these three areas, so it will be of use to a broad range of readers with different technical interests and educational levels.

Chapter 1

Design principles for dynamic microphysiological systems

Madeline Cooper⁎; Joseph L. Charest^†; Jonathan Coppeta^{‡ ⁎} Stanford University School of Medicine, Stanford, CA, United States
^† Biomedical Engineering, Draper, Cambridge, MA, United States
^‡ Biosystems and Tissue Engineering, Draper, Cambridge, MA, United States

Abstract

The increasing complexity and cost of drug discovery and medical research requires new approaches to efficiently develop the next generation of patient therapies. In vitro multiorgan systems have the potential to reduce cost and increase patient safety by bridging the gap between standard techniques of static cell culture and animal models and true human physiology. Multiorgan systems are dynamic cell culture platforms in which multiple tissue chambers are connected via flow of common media to recapitulate many aspects of the parent in vivo organ systems. These systems are complex feats of engineering requiring a cross-disciplinary design approach from many technical fields including biology, physiology, materials, and engineering. Herein we review key design aspects of multiorgan systems providing a framework to guide the development of future systems and highlight the results from one state-of-the-art system.

Keywords

Multiorgan systems; Human-on-chip; Body-on-chip; Organ-on-chip; Microfluidics; Cell culture; Drug discovery

1 Introduction

The current estimated cost of discovering a single new drug and bringing it to market is $802 million [1], with capitalized expenditures inclusive of failure amortization exceeding $2.5 billion [2]. One of the underlying issues is that methods to understand drug behavior during preclinical pharmaceutical development, such as basic cell culture and animal model studies, have not changed significantly for a half century [3]. The resulting inability to predict clinical effects of drugs in humans increases patient health risks, trial failure rates, and corresponding costs. As the complexities of drug targets and products, such as monoclonal antibodies and cell-based therapies, increase, the associated development and manufacturing will continue to grow exacerbating rising costs to bring these new therapies to market.

Conventional methods of studying biological responses, using static culture of single cell types and other organisms ranging in simplicity from yeast to nonhuman primates, lead to one of the main bottlenecks in drug development and deeper understanding of human physiology—the inability to study authentic human-specific organs ex vivo. Animal models capture systemic complexity but are often poor predictors of human physiological response. Single human cell types in static culture lack both essential cell-cell interactions between different cell types and the in vivo biological context required to create predictive models. Models capable of bridging the gap between human physiological response and conventional preclinical cell cultures or animal models are required. Creation of more predictive preclinical models based on recent advances in 3D organotypic models, along with efforts to integrate these complex models in multiorgan interacting systems, may help bridge this gap.

Advancements from 2D to 3D models have already revealed many biological phenomena that had previously been a mystery [4]. However, these models generally do not capture interactions between multiple tissues and organs and fail to model human systemic response to potential therapies. Microfluidic multiorgan systems have the potential to recapitulate fundamental aspects of human biology, inclusive of organ and tissue interactions, resulting in methods to predict drug behavior on the systemic human state.

1.1 What Are Microfluidic Multiorgan Cell Culture Systems?

A microfluidic multiorgan system (also known as body-on-chip or human-on-chip) is an in vitro cell culture device in which multiple tissue types are grown in separate chambers that interact with each other through a common media flowing between the chambers. Flow of media not only provides a means of paracrine signaling (e.g., metabolic communication, cytokine and hormonal) but also is designed to provide the “organs” with appropriate biophysical input, mimicking physiological effects like mechanical stimulation from perfusion of blood through the human body.

Distinct from the classic single “organ-on-chip” models, multiorgan systems link together multiple organs into more physiologically relevant systems where the organs interact, much as they do in the human body. As individual organ-on-chip models advance, it is important to simultaneously develop multiorgan systems to both take advantage of the more sophisticated models and also advance the models beyond what is possible in isolation. Thus, it is important to develop technologies for individual organ chips in a manner that is compatible with integration into larger systems. This will allow facile integration with disparate organs that mimics aspects of human physiology and is reliable from both a biological and an engineering perspective. If the single tissue chip only appears to have accurate physiological properties when in isolation but not when connected to other organs, its applications to the study of human biology may be limited. Second, the process of evolving single-organ chips toward more advanced engineering capabilities and high-throughput systems shares many of the same technical challenges that must be considered for multiorgan systems. Time and resources will be saved developing high-throughput single-organ models and multiorgan system technologies synchronously.

1.2 General Principles for Multiorgan System Development

Guided by our experience in microfluidic multiorgan system design and a review of existing models, we have generated the following suggested basic guiding principles for engineering a multiorgan system: establish (1) “reconfigurability” to integrate diverse and dynamic models; (2) physiological fluid perfusion of organs for nutrients, waste excretion, paracrine and endocrine cross talk, and biophysical cues; (3) physiological scaling of tissue and media; (4) platform scalability to accommodate organ system complexity; (5) common media; (6) facile, in-line, noninvasive tissue monitoring techniques and mechanisms for intermittent sampling without compromising samples or replicates; (7) materials and methods of construction supporting tissue and overall system requirements; and (8) system characteristics that allow consistent replication of results and long-term culture.

First, the motivation and value of the multiorgan approaches will be presented followed by examples of how the above design principles have been addressed previously. Finally, an example of a multiorgan system incorporating these principles will be described, along with specific applications.

1.3 Value of Microfluidic Multiorgan Systems

The value of in vitro multiorgan systems lies in the ability to make in vitro-to-in vivo correlations; once these systems advance to the point where they can be validated against aspects of human physiology, they will offer significant benefit in the medical pipeline spanning basic research, drug development, and patient-specific treatment.

1.3.1 Improvements in effectiveness and expense of drug development process

The current gold standard for preclinical testing in the drug development pathway involves testing compounds in 2D monocultures of human cells and various animal models such as mice and rats. However, only about one in nine drugs that pass preclinical testing successfully completes clinical trials and enters the market [5,6] with most failures resulting from safety and efficacy issues. This process wastes an inordinate amount of resources and money. These inadequacies also leave clinical trial participants vulnerable to exposure to potentially harmful compounds as a result of the inability to accurately predict adverse drug reactions (ADRs). In fact, it is estimated that preclinical testing correctly predicts ADRs as infrequently as 30% of the time [7].

In simple in vitro cell culture models, it has been shown that the same cells have drastically different drug sensitivities depending on their culture format. One stark, but not uncommon, example arises from experiments done by Horning et al. They show a 20-fold increase in the half maximal inhibitory concentration (IC₅₀) of doxorubicin when breast cancer tumor cells were grown in a 3D spheroid-like form instead of a 2D format [8]. Significant improvements in drug responsiveness, gene expression, morphology, and other parameters are similarly observed when cells cultured in a static 3D environment are integrated with microfluidics to create a physiologically dynamic 3D model [9].

Animal models provide organism-level complexity not currently possible with in vitro cultures; however, interspecies physiological differences can lead to differences in drug target binding, metabolizing enzymes and metabolites, and bioavailability. For example, human cells have species-specific surface receptors that allow them to uptake drugs or other pathways that render them uniquely affected by the drug's toxicity [10]. Additionally, the response to pathophysiological states may also be highly species and pathology dependent requiring detailed mechanistic knowledge [11,12]. Furthermore, maintenance and use of animals is expensive and time-consuming and raises ethical concerns. If multiorgan systems could replace a significant fraction of the drug development process that currently occurs in animal models, we would almost certainly see the cost and time requirements off-drug development reduced [10].

1.3.2 PK/PD modeling and understanding basic human biology

Much of the early work in developing “body-on-a-chip” technology pioneered by Shuler et al. focused on the potential for microfluidic multiorgan systems to mimic the in vivo coupling of human organs as they process and react to drug compounds. As previously outlined by Oleaga et al., such efforts are focused on validating organ models by matching experimental in vitro results with known...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Chapter 1: Design principles for dynamic microphysiological systems
• Chapter 2: Microfluidic systems for controlling stem cell microenvironments
• Chapter 3: Microfluidic platforms with nanoscale features
• Chapter 4: Microfabricated kidney tissue models
• Chapter 5: Application of complex in vitro models (CIVMs) in drug discovery for safety testing and disease modeling
• Chapter 6: Hepatic microphysiological systems: Current and future applications in drug discovery and development
• Chapter 7: Microphysiological models of human organs: A case study on microengineered lung-on-a-chip systems
• Chapter 8: Cardiac tissue models
• Chapter 9: Neural tissue microphysiological systems in the era of patient-derived pluripotent stem cells
• Chapter 10: A high-throughput system to probe and direct biological functions driven by complex hemodynamic environments
• Chapter 11: Body-on-a-chip systems: Design, fabrication, and applications
• Chapter 12: On-chip disease models of the human retina
• Index