Hollow fibre membrane bioreactors for tissue engineering applications

Recent advances in scaffolding biomaterials for cultivated meat

The emergence of cultivated meat provides a sustainable and ethical alternative to traditional animal agriculture, highlighting its increasing importance in the food industry. Biomaterial scaffolds are critical components in cultivated meat production for enabling cell adhesion, proliferation, differentiation, and orientation. While there's extensive research on scaffolding biomaterials, applying them to cultivated meat production poses distinct challenges, with each material offering its own set of advantages and disadvantages. This review summarizes the most recent scaffolding biomaterials used in the last five years for cell-cultured meat, detailing their respective advantages and disadvantages. We suggest future research directions and provide recommendations for scaffolds that support scalable, cost-effective, and safe high-quality meat production. Additionally, we highlight commercial challenges cultivated meat faces, encompassing bioreactor design, cell culture mediums, and regulatory and food safety issues. In summary, this review provides a comprehensive guide and valuable insights for researchers and companies in the field of cultivated meat production.

Stem Cell-Based Strategies: The Future Direction of Bioartificial Liver Development

Acute liver failure (ALF) results from severe liver damage or end-stage liver disease. It is extremely fatal and causes serious health and economic burdens worldwide. Once ALF occurs, liver transplantation (LT) is the only definitive and recommended treatment; however, LT is limited by the scarcity of liver grafts. Consequently, the clinical use of bioartificial liver (BAL) has been proposed as a treatment strategy for ALF. Human primary hepatocytes are an ideal cell source for these methods. However, their high demand and superior viability prevent their widespread use. Hence, finding alternatives that meet the seed cell quality and quantity requirements is imperative. Stem cells with self-renewing, immunogenic, and differentiative capacities are potential cell sources. MSCs and its secretomes encompass a spectrum of beneficial properties, such as anti-inflammatory, immunomodulatory, anti-ROS (reactive oxygen species), anti-apoptotic, pro-metabolomic, anti-fibrogenesis, and pro-regenerative attributes. This review focused on the recent status and future directions of stem cell-based strategies in BAL for ALF. Additionally, we discussed the opportunities and challenges associated with promoting such strategies for clinical applications.

Enhancing the palatability of cultivated meat

Cultivated meat (CM) has transitioned from a futuristic concept to a present reality, with select products approved for consumption and sale in Singapore, Israel, and the USA. This evolution has emphasized scalable, cost-effective, and sustainable production, as well as navigation of regulatory pathways. As CM develops, a crucial challenge lies in delivering products that are highly appealing to consumers. Central to this will be refining CM palatability, a term encompassing food's taste, aroma, texture, tenderness, juiciness, and color. We explore the scientific and engineering approaches to producing palatable CM, including cell-line selection, cell differentiation, and post-processing techniques. This includes a discussion of the structural and compositional properties of meat that are intrinsically coupled to palatability.

Challenges and strategies: Scalable and efficient production of mesenchymal stem cells-derived exosomes for cell-free therapy

Exosomes are small membrane vesicles secreted by most cell types, and widely exist in cell supernatants and various body fluids. They can transmit numerous bioactive elements, such as proteins, nucleic acids, and lipids, to affect the gene expression and function of recipient cells. Mesenchymal stem cells (MSCs) have been confirmed to be a potentially promising therapy for tissue repair and regeneration. Accumulating studies demonstrated that the predominant regenerative paradigm of MSCs transplantation was the paracrine effect but not the differentiation effect. Exosomes secreted by MSCs also showed similar therapeutic effects as their parent cells and were considered to be used for cell-free regenerative medicine. However, the inefficient and limited production has hampered their development for clinical translation. In this review, we summarize potential methods to efficiently promote the yield of exosomes. We mainly focus on engineering the process of exosome biogenesis and secretion, altering the cell culture conditions, cell expansion through 3D dynamic culture and the isolation of exosomes. In addition, we also discuss the application of MSCs-derived exosomes as therapeutics in disease treatment.

Scaling up human mesenchymal stem cell manufacturing using bioreactors for clinical uses

Human mesenchymal stem cells (hMSCs) are multipotent cells and an attractive therapeutic agent in regenerative medicine and intensive clinical research. Despite the great potential, the limitation that needs to be overcome is the necessity of ex vivo expansion because of insufficient number of hMSCs presented within adult organs and the high doses required for a transplantation. As a result, numerous research studies aim to provide novel expansion methods in order to achieve appropriate numbers of cells with preserved therapeutic quality. Bioreactor-based cell expansion provide high-level production of hMSCs in accordance with good manufacturing practice (GMP) and quality standards. This review summarizes current knowledge about the hMSCs manufacturing platforms with a main focus to the application of bioreactors for large-scale production of GMP-grade hMSCs.

On the quest of reliable 3D dynamic in vitro blood-brain barrier models using polymer hollow fiber membranes: Pitfalls, progress, and future perspectives

With the increasing concern of neurodegenerative diseases, the development of new therapies and effective pharmaceuticals targeted to central nervous system (CNS) illnesses is crucial for ensuring social and economic sustainability in an ageing world. Unfortunately, many promising treatments at the initial stages of the pharmaceutical development process, that is at the in vitro screening stages, do not finally show the expected results at the clinical level due to their inability to cross the human blood-brain barrier (BBB), highlighting the inefficiency of in vitro BBB models to recapitulate the real functionality of the human BBB. In the last decades research has focused on the development of in vitro BBB models from basic 2D monolayer cultures to 3D cell co-cultures employing different system configurations. Particularly, the use of polymeric hollow fiber membranes (HFs) as scaffolds plays a key role in perfusing 3D dynamic in vitro BBB (DIV-BBB) models. Their incorporation into a perfusion bioreactor system may potentially enhance the vascularization and oxygenation of 3D cell cultures improving cell communication and the exchange of nutrients and metabolites through the microporous membranes. The quest for developing a benchmark 3D dynamic in vitro blood brain barrier model requires the critical assessment of the different aspects that limits the technology. This article will focus on identifying the advantages and main limitations of the HFs in terms of polymer materials, microscopic porous morphology, and other practical issues that play an important role to adequately mimic the physiological environment and recapitulate BBB architecture. Based on this study, we consider that future strategic advances of this technology to become fully implemented as a gold standard DIV-BBB model will require the exploration of novel polymers and/or composite materials, and the optimization of the morphology of the membranes towards thinner HFs (<50 μm) with higher porosities and surface pore sizes of 1–2 µm to facilitate the intercommunication via regulatory factors between the cell co-culture models of the BBB.

Technological and structural aspects of scaffold manufacturing for cultured meat: recent advances, challenges, and opportunities

In vitro cultured meat is an emerging area of research focus with an innovative approach through tissue engineering (i.e., cellular engineering) to meet the global food demand. The manufacturing of lab-cultivated meat is an innovative business that alleviates life-threatening environmental issues concerning public health and animal well-being on the global platform. There has been a noteworthy advancement in cultivating artificial meat, but still, there are numerous challenges that impede the swift headway of lab-grown meat production at a commercially large scale. In this review, we focus on the manufacturing of edible scaffolds for cultured meat production. In brief, first an introduction to cultivating artificial meat and its current scenario in the market is provided. Further, a discussion on the understanding of composition, cellular, and molecular communications in muscle tissue is presented, which are vital to scaling up the production of lab-grown meat. In continuation, the major components (e.g., cells, biomaterial scaffolds, and their manufacturing technologies, media, and potential bioreactors) for cultured meat production are conferred followed by a comprehensive discussion on the most recent advances in lab-cultured meat. Finally, existing challenges and opportunities including future research perspectives for scaling-up cultured meat production are discussed with conclusive interpretations.

Design considerations of benchtop fluid flow bioreactors for bio-engineered tissue equivalents in vitro

One of the major aims of bio-engineering tissue equivalents in vitro is to create physiologically relevant culture conditions to accurately recreate the cellular microenvironment. This often includes incorporation of factors such as the extracellular matrix, co-culture of multiple cell types and three-dimensional culture techniques. These advanced techniques can recapitulate some of the properties of tissue in vivo, however fluid flow is a key aspect that is often absent. Fluid flow can be introduced into cell and tissue culture using bioreactors, which are becoming increasingly common as we seek to produce increasingly accurate tissue models. Bespoke technology is continuously being developed to tailor systems for specific applications and to allow compatibility with a range of culture techniques. For effective perfusion of a tissue culture many parameters can be controlled, ranging from impacts of the fluid flow such as increased shear stress and mass transport, to potentially unwanted side effects such as temperature fluctuations. A thorough understanding of these properties and their implications on the culture model can aid with a more accurate interpretation of results. Improved and more complete characterisation of bioreactor properties will also lead to greater accuracy when reporting culture conditions in protocols, aiding experimental reproducibility, and allowing more precise comparison of results between different systems. In this review we provide an analysis of the different factors involved in the development of benchtop flow bioreactors and their potential biological impacts across a range of applications.

Bioartificial livers: a review of their design and manufacture

Acute liver failure (ALF) is a rapidly progressive disease with high morbidity and mortality rates. Liver transplantation and artificial liver support systems, such as artificial livers (ALs) and bioartificial livers (BALs), are the two major therapies for ALF. Compared to ALs, BALs are composed of functional hepatocytes that provide essential liver functions, including detoxification, metabolite synthesis, and biotransformation. Furthermore, BALs can potentially provide effective support as a form of bridging therapy to liver transplantation or spontaneous recovery for patients with ALF. In this review, we systematically discussed the currently available state-of-the-art designs and manufacturing processes for BAL support systems. Specifically, we classified the cell sources and bioreactors that are applied in BALs, highlighted the advanced technologies of hepatocyte culturing and bioreactor fabrication, and discussed the current challenges and future trends in developing next generation BALs for large scale clinical applications.

Large-scale cultured meat production: Trends, challenges and promising biomanufacturing technologies

Food systems of the future will need to face an increasingly clear reality - that a protein-rich diet is essential for good health, but traditional meat products will not suffice to ensure safety, sustainability, and equity of food supply chains at a global scale. This paper provides an in-depth analysis of bioprocess technologies needed for cell-based meat production and challenges in reaching commercial scale. Specifically, it reviews state-of-the-art bioprocess technologies, current limitations, and opportunities for research across four domains: cell line development, cell culture media, scaffolding, and bioreactors. This also includes exploring innovations to make cultured meat a viable protein alternative across numerous key performance indicators and for specific applications where traditional livestock is not an option (e.g., local production, space exploration). The paper explores tradeoffs between production scale, product quality, production cost, and footprint over different time horizons. Finally, a discussion explores various factors that may impact the ability to successfully scale and market cultured meat products: social acceptance, environmental tradeoffs, regulatory guidance, and public health benefits. While the exact nature of the transition from traditional livestock to alternative protein products is uncertain, it has already started and will likely continue to build momentum in the next decade.

Integrating biomaterials and food biopolymers for cultured meat production

Cultured meat has recently achieved mainstream prominence due to the emergence of societal and industrial interest. In contrast to animal-based production of traditional meat, the cultured meat approach entails laboratory cultivation of engineered muscle tissue. However, bioengineers have hitherto engineered tissues to fulfil biomedical endpoints, and have had limited experience in engineering muscle tissue for its post-mortem traits, which broadly govern consumer definitions of meat quality. Furthermore, existing tissue engineering approaches face fundamental challenges in technical feasibility and industrial scalability for cultured meat production. This review discusses how animal-based meat production variables influence meat properties at both the molecular and functional level, and whether current cultured meat approaches recapitulate these properties. In addition, this review considers how conventional meat producers employ exogenous biopolymer-based meat ingredients and processing techniques to mimic desirable meat properties in meat products. Finally, current biomaterial strategies for engineering muscle and adipose tissue are surveyed in the context of emerging constraints that pertain to cultured meat production, such as edibility, sustainability and scalability, and potential areas for integrating biomaterials and food biopolymer approaches to address these constraints are discussed. STATEMENT OF SIGNIFICANCE: Laboratory-grown or cultured meat has gained increasing interest from industry and the public, but currently faces significant impediment to market feasibility. This is due to fundamental knowledge gaps in producing realistic meat tissues via conventional tissue engineering approaches, as well as translational challenges in scaling up these approaches in an efficient, sustainable and high-volume manner. By defining the molecular basis for desirable meat quality attributes, such as taste and texture, and introducing the fundamental roles of food biopolymers in mimicking these properties in conventional meat products, this review aims to bridge the historically disparate fields of meat science and biomaterials engineering in order to inspire potentially synergistic strategies that address some of these challenges.

Modelling of hollow fiber membrane bioreactor for mammalian cell cultivation using computational hydrodynamics

The hollow fiber membrane bioreactor (HFMB) has been investigated for the cultivation of mammalian Chinese hamster ovary cell expansion. The experiments were carried out in Petri's dishes and in the hollow fiber membrane bioreactor having 20 fibers (S2025 from FiberCell Systems). The approach to HFMB modelling which combines the model of cell growth kinetics and hydrodynamics has been proposed. The hydrodynamic model is made using ANSYS Fluent software. The mathematical model of HFMB was developed, allowing the study of the hydrodynamics into the lumen and the extracapillary spaces, the filtration through the membrane fiber with the cell expansion on outer membrane surface. The direct nutrient medium flow variant into the extracapillary space was suggested. Based on the numerical simulations, the optimal parameters were selected for daily changes in the medium flow-rate into the lumen space. The HFMB scaling up was performed for the larger size HFMB (60 fibers).

Evaluation of drug combination for glioblastoma based on an intestine-liver metabolic model on microchip

An intestine-liver-glioblastoma biomimetic system was developed to evaluate the drug combination therapy for glioblastoma. A hollow fiber (HF) was embedded into the upper layer of the microfluidic chip for culturing Caco-2 cells to mimic drug delivery as an artificial intestine. HepG2 cells cultured in the bottom chamber of the chip acted as an artificial liver for metabolizing the drugs. The dual-drug combination to glioblastoma U251 cells was evaluated based on the intestine-liver metabolic model. The drugs, irinotecan (CPT-11), temozolomide (TMZ) and cyclophosphamide (CP), were used to dynamically stimulate the cells by continuous infusion into the intestine unit. After intestine absorption and liver metabolism, the prodrugs were transformed to active metabolites, which induced glioblastoma cells apoptosis. The anticancer activity of the CPT-11 and TMZ combination is significantly enhanced compared to that of the single drug treatments. Combination index (CI) values of the combination groups, CPT-11 and TMZ, CPT-11 and CP, and TMZ and CP, at half maximal inhibitory concentration were 0.137, 0.288, and 0.482, respectively. The results indicated that the CPT-11 and TMZ combination was superior to the CPT-11 and CP group as well as the TMZ and CP group towards the U251 cells. The metabolism mechanism of CPT-11 and TMZ was further studied by coupling with mass spectrometric analysis. The biomimetic model enables the performance of long-term cell co-culture, drug delivery, metabolism and real-time analysis of drug effects, promising systematic in vitro mimicking of physiological and pharmacological processes.

Bioengineering Organs for Blood Detoxification

For patients with severe kidney or liver failure the best solution is currently organ transplantation. However, not all patients are eligible for transplantation and due to limited organ availability, most patients are currently treated with therapies using artificial kidney and artificial liver devices. These therapies, despite their relative success in preserving the patients' life, have important limitations since they can only replace part of the natural kidney or liver functions. As blood detoxification (and other functions) in these highly perfused organs is achieved by specialized cells, it seems relevant to review the approaches leading to bioengineered organs fulfilling most of the native organ functions. There, the culture of cells of specific phenotypes on adapted scaffolds that can be perfused takes place. In this review paper, first the functions of kidney and liver organs are briefly described. Then artificial kidney/liver devices, bioartificial kidney devices, and bioartificial liver devices are focused on, as well as biohybrid constructs obtained by decellularization and recellularization of animal organs. For all organs, a thorough overview of the literature is given and the perspectives for their application in the clinic are discussed.

Next generation in vitro liver model design: Combining a permeable polystyrene membrane with a transdifferentiated cell line

Herein we describe the manufacture and characterisation of biocompatible, porous polystyrene membranes, suitable for cell culture. Though widely used in traditional cell culture, polystyrene has not been used as a hollow fibre membrane due to its hydrophobicity and non-porous structure. Here, we use microcrystalline sodium chloride (4.7 ± 1.3 µm) to control the porosity of polystyrene membranes and oxygen plasma surface treatment to reduce hydrophobicity. Increased porogen concentration correlates to increased surface pore density, macrovoid formation, gas permeability and mean pore size, but a decrease in mechanical strength. For tissue engineering applications, membranes spun from casting solutions containing 40% (w/w) sodium chloride represent a compromise between strength and permeability, having surface pore density of 208.2 ± 29.7 pores/mm², mean surface pore size of 2.3 ± 0.7 µm, and Young's modulus of 115.0 ± 8.2 MPa. We demonstrate the biocompatibility of the material with an exciting cell line-media combination: transdifferentiation of the AR42J-B13 pancreatic cell line to hepatocyte-like cells. Treatment of AR42J-B13 with dexamethasone/oncostatin-M over 14 days induces transdifferentiation towards a hepatic phenotype. There was a distinct loss of the pancreatic phenotype, shown through loss of expression of the pancreatic marker amylase, and gain of the hepatic phenotype, shown through induction of expression of the hepatic markers transferrin, carbamoylphosphate synthetase and glutamine synthetase. The combination of this membrane fabrication method and demonstration of biocompatibility of the transdifferentiated hepatocytes provides a novel, superior, alternative design for in vitro liver models and bioartificial liver devices.

Optimizing T Cell Expansion in a Hollow-Fiber Bioreactor

Purpose of Review

Recent developments in regenerative medicine have precipitated the need to expand gene-modified human T cells to numbers that exceed the capacity of well-plate-based, and flask-based processes. This review discusses the changes in process development that are needed to meet the cell expansion requirements by utilizing hollow-fiber bioreactors. Maintenance of cell proliferation over long periods can become limited by unfilled demands for nutrients and oxygen and by the accumulation of waste products in the local environment.

Recent Findings

Perfusion feeding, improved gas exchange, and the efficient removal of lactate can increase the yield of T cells from an average of 10.8E +09 to more than 28E +09 in only 10 days.

Summary

Aggressively feeding cells and actively keeping cells in the bioreactor improves gas exchange and metabolite management over semi-static methods. The ability to remove the environmental constraints that can limit cell expansion by using a two-chamber hollow-fiber bioreactor will be discussed.

Bioengineering Solutions for Manufacturing Challenges in CAR T Cells

The next generation of therapeutic products to be approved for the clinic is anticipated to be cell therapies, termed "living drugs" for their capacity to dynamically and temporally respond to changes during their production ex vivo and after their administration in vivo. Genetically engineered chimeric antigen receptor (CAR) T cells have rapidly developed into powerful tools to harness the power of immune system manipulation against cancer. Regulatory agencies are beginning to approve CAR T cell therapies due to their striking efficacy in treating some hematological malignancies. However, the engineering and manufacturing of such cells remains a challenge for widespread adoption of this technology. Bioengineering approaches including biomaterials, synthetic biology, metabolic engineering, process control and automation, and in vitro disease modeling could offer promising methods to overcome some of these challenges. Here, we describe the manufacturing process of CAR T cells, highlighting potential roles for bioengineers to partner with biologists and clinicians to advance the manufacture of these complex cellular products under rigorous regulatory and quality control.

Hollow Fiber Bioreactors for In Vivo-like Mammalian Tissue Culture

Tissue culture has been used for over 100 years to study cells and responses ex vivo. The convention of this technique is the growth of anchorage dependent cells on the 2-dimensional surface of tissue culture plastic. More recently, there is a growing body of data demonstrating more in vivo-like behaviors of cells grown in 3-dimensional culture systems. This manuscript describes in detail the set-up and operation of a hollow fiber bioreactor system for the in vivo-like culture of mammalian cells. The hollow fiber bioreactor system delivers media to the cells in a manner akin to the delivery of blood through the capillary networks in vivo. The system is designed to fit onto the shelf of a standard CO2 incubator and is simple enough to be set-up by any competent cell biologist with a good understanding of aseptic technique. The systems utility is demonstrated by culturing the hepatocarcinoma cell line HepG2/C3A for 7 days. Further to this and in line with other published reports on the functionality of cells grown in 3-dimensional culture systems the cells are shown to possess increased albumin production (an important hepatic function) when compared to standard 2-dimensional tissue culture.

Hollow fiber bioreactor technology for tissue engineering applications

Hollow fiber bioreactors are the focus of scientific research aiming to mimic physiological vascular networks and engineer organs and tissues in vitro. The reason for this lies in the interesting features of this bioreactor type, including excellent mass transport properties. Indeed, hollow fiber bioreactors allow limitations to be overcome in nutrient transport by diffusion, which is often an obstacle to engineer sizable constructs in vitro. This work reviews the existing literature relevant to hollow fiber bioreactors in organ and tissue engineering applications. To this purpose, we first classify the hollow fiber bioreactors into 2 categories: cylindrical and rectangular. For each category, we summarize their main applications both at the tissue and at the organ level, focusing on experimental models and computational studies as predictive tools for designing innovative, dynamic culture systems. Finally, we discuss future perspectives on hollow fiber bioreactors as in vitro models for tissue and organ engineering applications.