Encapsulated human hepatocellular carcinoma cells by alginate gel beads as an in vitro metastasis model

Cell microencapsulation techniques for cancer modelling and drug discovery

Cell encapsulation into spherical microparticles is a promising bioengineering tool in many fields, including 3D cancer modelling and pre-clinical drug discovery. Cancer microencapsulation models can more accurately reflect the complex solid tumour microenvironment than 2D cell culture and therefore would improve drug discovery efforts. However, these microcapsules, typically in the range of 1 - 5000 µm in diameter, must be carefully designed and amenable to high-throughput production. This review therefore aims to outline important considerations in the design of cancer cell microencapsulation models for drug discovery applications and examine current techniques to produce these. Extrusion (dripping) droplet generation and emulsion-based techniques are highlighted and their suitability to high-throughput drug screening in terms of tumour physiology and ease of scale up is evaluated.

Effect of calcium concentration on metastasis of hepatocellular carcinoma cells cultured in alginate gel beads

Changes in sodium alginate and calcium ion concentrations have a considerable impact on the structural properties of calcium alginate gel (ALG) beads, consequently influencing the biological characteristics of the cells encapsulated within them. This study aimed to examine the effects of calcium on the metastatic potential of hepatocellular carcinoma (HCC) cells encapsulated in ALG beads. The results showed that the invasion ability of HCC cells significantly increased when they were encapsulated in beads prepared with a calcium concentration of 200 mM compared to those prepared with a calcium concentration of 50 mM. Furthermore, the expression levels of genes related to metastasis were significantly elevated in ALG beads prepared with a calcium concentration of 200 mM. Specifically, the expression of activated matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9), and urokinase-type plasminogen activator system proteins was found to be high. Conversely, the expression of phosphatase and tensin homolog deleted on chromosome 10 was observed to be significantly reduced. These findings indicate that manipulating the calcium ion concentration during the fabrication of ALG beads enables the generation of three-dimensional HCC cells with varying metastatic capacities. This model offers a valuable tool for investigating the mechanisms underlying liver cancer metastasis and screening potential therapeutic drugs.

Liver Cancer: New Insights into Surgical and Nonsurgical Treatments

Introduction:

Hepatocellular carcinoma (HCC) is the most common type of liver cancer that has increased in recent years worldwide. Primary liver cancer or HCC is considered the 5th and 7th most common cancer among men and women, respectively. It is also the second leading cause of cancer death worldwide. Unfortunately, HCC is frequently diagnosed at an advanced stage when the majority of the patients do not have access to remedial therapies. Furthermore, current systemic chemotherapy shows low efficacy and minimum survival benefits. Liver cancer therapy is a multidisciplinary, multiple-choice treatment based on the complex interaction of the tumour stage, the degree of liver disease, and the patient's general state of health.

Methods:

In this paper, we reviewed new insights into nonsurgical and surgical treatment of liver cancer in five English databases, including Scopus, PubMed, Web of Science, EMBASE, and Google Scholar up to December 2019.

Results:

The results demonstrated, in addition to current therapies such as chemotherapy and surgical resection, new approaches, including immunotherapy, viral therapy, gene therapy, new ablation therapies, and adjuvant therapy, are widely used for the treatment of HCC. In recent years, biomaterials such as nanoparticles, liposomes, microspheres, and nanofibers are also regarded as reliable and innovative patents for the treatment and study of liver cancers.

Conclusion:

Multidisciplinary and multi-choice treatments and therapies are available for this liver cancer, while there are differences in liver cancer management recommendations among specialties and geographic areas. Current results have shown that treatment strategies have been combined with the advancement of novel treatment modalities. In addition, the use of new approaches with greater efficacy, such as combination therapy, biomaterials, ablation therapy, etc. can be considered the preferred treatment for patients.

Recent advances in bionanomaterials for liver cancer diagnosis and treatment

According to the World Health Organization, liver cancer is the fourth leading cause of cancer associated with death worldwide. It demands effective treatment and diagnostic strategies to hinder its recurrence, complexities, aggressive metastasis and late diagnosis. With recent progress in nanotechnology, several nanoparticle-based diagnostic and therapeutic modalities have entered into clinical trials. With further developments in nanoparticle mediated liver cancer diagnosis and treatment, the approach holds promise for improved clinical liver cancer management. In this review, we discuss the key advances in nanoparticles that have potential for liver cancer diagnosis and treatment. We also discuss the potential of nanoparticles to overcome the limitations of existing therapeutic modalities.

Cancer Cell Direct Bioprinting: A Focused Review

Three-dimensional printing technologies allow for the fabrication of complex parts with accurate geometry and less production time. When applied to biomedical applications, two different approaches, known as direct or indirect bioprinting, may be performed. The classical way is to print a support structure, the scaffold, and then culture the cells. Due to the low efficiency of this method, direct bioprinting has been proposed, with or without the use of scaffolds. Scaffolds are the most common technology to culture cells, but bioassembly of cells may be an interesting methodology to mimic the native microenvironment, the extracellular matrix, where the cells interact between themselves. The purpose of this review is to give an updated report about the materials, the bioprinting technologies, and the cells used in cancer research for breast, brain, lung, liver, reproductive, gastric, skin, and bladder associated cancers, to help the development of possible treatments to lower the mortality rates, increasing the effectiveness of guided therapies. This work introduces direct bioprinting to be considered as a key factor above the main tissue engineering technologies.

3D Modeling of Epithelial Tumors-The Synergy between Materials Engineering, 3D Bioprinting, High-Content Imaging, and Nanotechnology

The current statistics on cancer show that 90% of all human cancers originate from epithelial cells. Breast and prostate cancer are examples of common tumors of epithelial origin that would benefit from improved drug treatment strategies. About 90% of preclinically approved drugs fail in clinical trials, partially due to the use of too simplified in vitro models and a lack of mimicking the tumor microenvironment in drug efficacy testing. This review focuses on the origin and mechanism of epithelial cancers, followed by experimental models designed to recapitulate the epithelial cancer structure and microenvironment, such as 2D and 3D cell culture models and animal models. A specific focus is put on novel technologies for cell culture of spheroids, organoids, and 3D-printed tissue-like models utilizing biomaterials of natural or synthetic origins. Further emphasis is laid on high-content imaging technologies that are used in the field to visualize in vitro models and their morphology. The associated technological advancements and challenges are also discussed. Finally, the review gives an insight into the potential of exploiting nanotechnological approaches in epithelial cancer research both as tools in tumor modeling and how they can be utilized for the development of nanotherapeutics.

Engineering confining microenvironment for studying cancer metastasis

The physical microenvironment of cells plays a fundamental role in regulating cellular behavior and cell fate, especially in the context of cancer metastasis. For example, capillary deformation can destroy arrested circulating tumor cells while the dense extracellular matrix can form a physical barrier for invading cancer cells. Understanding how metastatic cancer cells overcome the challenges brought forth by physical confinement can help in developing better therapeutics that can put a stop to this migratory stage of the metastatic cascade. Numerous in vivo and in vitro assays have been developed to recapitulate the metastatic processes and study cancer cell migration in a confining microenvironment. In this review, we summarize some of the representative techniques and the exciting new findings. We critically review the advantages, as well as challenges associated with these tools and methodologies, and provide a guide on the applications that they are most suited for. We hope future efforts that push forward our current understanding on metastasis under confinement can lead to novel and more effective diagnostic and therapeutic strategies against this dreaded disease.

Evaluation of anti-tumor effects of crocin on a novel 3D tissue-engineered tumor model based on sodium alginate/gelatin microbead

Crocin, as one of the biologically active components of saffron, has anti-inflammatory, anti-oxidant, anti-depressant and auxiliary anti-tumor effects. Studies have shown that crocin could promote breast cancer cell apoptosis. However, conventional methods are mainly based on two-dimensional (2D) cell culture models, which are difficult to reproduce the tumor environment in vivo due to space constraints. In this study, we prepared a three-dimensional (3D) cell model in vitro based on sodium alginate/gelatin to evaluate the inhibitory effect of crocin on MCF-7 cells, which could bridge the gap in crocin drug evaluation between 2D and 3D cell model in vitro. Different from the 2D culture, the cells were found to aggregate in a spherical shape in the 3D microgel beads. And the CCK-8 assay showed that the growth of MCF-7 cells exposed to crocin was inhibited in a time-related and concentration-related manner. Compared with 2D culture (IC₅₀ that MCF-7 cells treated with crocin at 24 h, 48 h, 72 h: 3.68, 2.55 and 1.53 mg/mL, respectively), the IC₅₀ value of 3D culture (IC₅₀ that MCF-7 cells treated with crocin at 24 h, 48 h, 72 h: 10.12, 6.89 and 6.64 mg/mL, respectively) was significantly increased by 2.77, 2.70, 4.34 times, respectively. Besides, live/dead staining and scanning electron microscope (SEM) revealed that the 2D cultured cells shrank and ruptured after crocin treatment, and the number of living cells was considerably reduced; the size of the cell colonies in the 3D microgel beads decreased.

Advances in Bio-Based Polymers for Colorectal CancerTreatment: Hydrogels and Nanoplatforms

Adenocarcinoma of the colon is the most common malignant neoplasia of the gastrointestinal tract and is a major contributor to mortality worldwide. Invasiveness and metastatic behavior are typical of malignant tumors and, because of its portal drainage, the liver is the closest capillary bed available in this case, hence the common site of metastatic dissemination. Current therapies forecast total resection of primary tumor when possible and partial liver resection at advanced stages, along with systemic intravenous therapies consisting of chemotherapeutic agents such as 5-fluorouracil. These cures are definitely not exempt from drawbacks and heavy side effects. Biocompatible polymeric networks, both in colloids and bulk forms, able to absorb large quantities of water and load a variety of molecules-belong to the class of innovative drug delivery systems, thus suitable for the purpose and tunable on each patient can represent a promising alternative. Indeed, the implantation of polymeric scaffolds easy to synthesize can substitute chemotherapy and combination therapies scheduling, shortening side effects. Moreover, they do not require a surgical removal thanks to spontaneous degradation and guarantees an extended and regional cargo release, maintaining high drug concentrations. In this review, we focus our attention on the key role of polymeric networks as drug delivery systems potentially able to counteract this dramatic disease.

Study on the stability and cellular affinity of gelatin-polysaccharide composite films

The gelatin film has great potential in biomedical applications, especially in wound healing. The combination of gelatin films and stem cells could further accelerate the skin regeneration. Although polysaccharide modification can improve the mechanical property and biological activity of gelatin films, information about the stability and cellular affinity is still limited. This study investigated the influence of polysaccharides on the stability and cellular affinity of gelatin films. Two kinds of gelatin-polysaccharide composite films, including gelatin-hyaluronic acid (G-HA) and gelatin-chitosan (G-CS), were prepared in this study. It was found that G-HA composite film had better short-term and long-term stability compared with G-CS composite film. And G-HA composite film also had better biological safety than G-CS film. Moreover, the surface of G-HA composite film supported the adhesion and growth of human umbilical cord Wharton's jelly-derived mesenchymal stem cells (WJ MSCs) better than G-CS film surface. These data illustrated that G-HA composite film has better stability and cellular affinity compared with G-CS film, which could be considered a promising delivery system of stem cells for further in vivo studies. Therefore, this work would be very helpful to optimize the preparation of gelatin-polysaccharide composite films.

Liver Cancer: Current and Future Trends Using Biomaterials

Hepatocellular carcinoma (HCC) is the fifth most common type of cancer diagnosed and the second leading cause of death worldwide. Despite advancement in current treatments for HCC, the prognosis for this cancer is still unfavorable. This comprehensive review article focuses on all the current technology that applies biomaterials to treat and study liver cancer, thus showing the versatility of biomaterials to be used as smart tools in this complex pathologic scenario. Specifically, after introducing the liver anatomy and pathology by focusing on the available treatments for HCC, this review summarizes the current biomaterial-based approaches for systemic delivery and implantable tools for locally administrating bioactive factors and provides a comprehensive discussion of the specific therapies and targeting agents to efficiently deliver those factors. This review also highlights the novel application of biomaterials to study HCC, which includes hydrogels and scaffolds to tissue engineer 3D in vitro models representative of the tumor environment. Such models will serve to better understand the tumor biology and investigate new therapies for HCC. Special focus is given to innovative approaches, e.g., combined delivery therapies, and to alternative approaches-e.g., cell capture-as promising future trends in the application of biomaterials to treat HCC.

Design of spherically structured 3D in vitro tumor models -Advances and prospects

Three-dimensional multicellular tumor models are receiving an ever-growing focus as preclinical drug-screening platforms due to their potential to recapitulate major physiological features of human tumors in vitro. In line with this momentum, the technologies for assembly of 3D microtumors are rapidly evolving towards a comprehensive inclusion of tumor microenvironment elements. Customized spherically structured platforms, including microparticles and microcapsules, provide a robust and scalable technology to imprint unique biomolecular tumor microenvironment hallmarks into 3D in vitro models. Herein, a comprehensive overview of novel advances on the integration of tumor-ECM components and biomechanical cues into 3D in vitro models assembled in spherical shaped platforms is provided. Future improvements regarding spatiotemporal/mechanical adaptability, and degradability, during microtumors in vitro 3D culture are also critically discussed considering the realistic potential of these platforms to mimic the dynamic tumor microenvironment. From a global perspective, the production of 3D multicellular spheroids with tumor ECM components included in spherical models will unlock their potential to be used in high-throughput screening of therapeutic compounds. It is envisioned, in a near future, that a combination of spherically structured 3D microtumor models with other advanced microfluidic technologies will properly recapitulate the flow dynamics of human tumors in vitro.

STATEMENT OF SIGNIFICANCE

The ability to correctly mimic the complexity of the tumor microenvironment in vitro is a key aspect for the development of evermore realistic in vitro models for drug-screening and fundamental cancer biology studies. In this regard, conventional spheroid-based 3D tumor models, combined with spherically structured biomaterials, opens the opportunity to precisely recapitulate complex cell-extracellular matrix interactions and tumor compartmentalization. This review provides an in-depth focus on current developments regarding spherically structured scaffolds engineered into in vitro 3D tumor models, and discusses future advances toward all-encompassing platforms that may provide an improved in vitro/in vivo correlation in a foreseeable future.

Microencapsulation of low-passage poorly-differentiated human mucoepidermoid carcinoma cells by alginate microcapsules: in vitro profiling of angiogenesis-related molecules

Background

Human mucoepidermoid carcinoma (MEC) is regarded as the most common primary salivary malignancy. High-grade MEC has a high risk of recurrence and poor prognosis. Tumor angiogenesis, induced by poorly differentiated cancer cells of high-grade MEC, contributes to tumor growth and metastasis. Therefore, elucidating molecular mechanisms underlying the pro-angiogenic ability of poorly differentiated MEC cells is critical for the understanding of high-grade MEC progression. It is well known that three-dimensional (3D) cell culture, in contrast with conventional two-dimensional (2D) culture, provides a better approach to in vitro recapitulation of in vivo characteristics of cancer cells and their surrounding microenvironment. The purpose of this study was to model a 3D environment for in vitro gene expression profiling of key molecules in poorly differentiated MEC cells for cancer neovascularization and compared them with traditional 2D cell culture.

Methods

Low-passage poorly differentiated MEC cells, derived from human patient samples of high-grade MEC, were microencapsulated in sodium alginate gel microcapsules (3D culture) and compared with cells grown in 2D culture. Cancer cell proliferation was determined by MTT assays for 1 week, and gene expression of VEGF-A, bFGF and TSP-1 was analyzed by western blotting or ELISA. The hypoxic environment in 3D versus 2D culture were assessed by western blotting or immunofluorescence for HIF1α, and the effect of hypoxia on VEGF-A gene expression in 3D cultured cancer cells was assessed by western blotting with the use of the HIF1α inhibitor, 2-methoxyestradiol (2-MeOE2).

Results

When encapsulated in alginate gel microcapsules, low-passage poorly differentiated human MEC cells grew in blocks and demonstrated stronger and relatively unlimited proliferation activities. Moreover, significant differences were found in gene expression, with 3D-grown cancer cells a significant increment of VEGF-A and bFGF and a drastic reduction of TSP-1. Consistently, 3D-grown cancer cells secreted significantly more VEGF-A than 2D culture cancer cells. Furthermore, 3D-grown cancer cells showed significantly higher expression of HIF1α, a molecular indicator of hypoxia; the increased expression of VEGF-A in 3D cultured cancer cells was shown to be dependent on the HIF1α activities.

Conclusions

The present work shows the effects of 3D culture model by alginate microencapsulation on the proangiogenic potentials of low-passage poorly differentiated human MEC cells. Cancer cells in this 3D system demonstrate significant intensification of key molecular processes for tumor angiogenesis. This is due to a better modeling of the hypoxic tumor microenvironment during 3D culture.

Effects of gelling bath on the physical properties of alginate gel beads and the biological characteristics of entrapped HepG2 cells

Optimizing alginate gel beads is necessary to support the survival, proliferation, and function of entrapped hepatocytes. In this study, gelling bath was modified by decreasing calcium ion concentration and increasing sodium ion concentration. Alginate gel beads (using 36% G sodium alginate) prepared in the modified gelling bath had more homogeneous structure and better mass transfer properties compared with the traditional gelling bath that contains only calcium ions. Moreover, alginate gel beads generated in the modified gelling bath could significantly promote the HepG2 cell proliferation and the growth of cell spheroids, and maintain the albumin secretion ability similar to alginate gel beads prepared in the traditional gelling bath with only calcium ions. The mass transfer properties and cell proliferation were similar in ALG beads with different M/G ratio (36% G and 55% G) generated in the modified gelling bath, whereas they were significantly increased compared with alginate gel beads (55% G) in traditional gelling bath. These results indicated that adjusting the gelling bath was a simple and convenient method to enhance the mass transfer properties of alginate gel beads for 3D hepatocyte culture, which might provide more hepatocytes for the bioartificial liver support system.

Evaluating Biomaterial- and Microfluidic-Based 3D Tumor Models

Cancer is a major cause of morbidity and mortality worldwide, with a disease burden estimated to increase over the coming decades. Disease heterogeneity and limited information on cancer biology and disease mechanisms are aspects that 2D cell cultures fail to address. Here, we review the current ‘state-of-the-art’ in 3D tissue-engineering (TE) models developed for, and used in, cancer research. We assess the potential for scaffold-based TE models and microfluidics to fill the gap between 2D models and clinical application. We also discuss recent advances in combining the principles of 3D TE models and microfluidics, with a special focus on biomaterials and the most promising chip-based 3D models.

Mesenchymal stem cells enhance the metastasis of 3D-cultured hepatocellular carcinoma cells

Background

Accumulating evidences have demonstrated that mesenchymal stem cells (MSC) could be recruited to the tumor microenvironment. Umbilical cord mesenchymal stem cells (UCMSC) were attractive vehicles for delivering therapeutic agents against cancer. Nevertheless, the safety of UCMSC in the treatment of tumors including hepatocellular carcinoma (HCC) was still undetermined.

Methods

In this study, an in vitro co-culture system was established to evaluate the effect of UCMSC on the cell growth, cancer stem cell (CSC) characteristics, drug resistance, metastasis of 3D-cultured HCC cells, and the underlying mechanism was also investigated.

Results

It was found that after co-cultured with UCMSC, the metastatic ability of 3D-cultured HCC cells was significantly enhanced as indicated by up-regulation of matrix metalloproteinase (MMP), epithelial-mesenchymal transition (EMT)-related genes, and migration ability. However, cell growth, drug resistance and CSC-related gene expression of HCC cells were not affected by UCMSC. Moreover, EMT was reversed, MMP-2 expression was down-regulated, and migration ability of HCC cell was significantly inhibited when TGF-β receptor inhibitor SB431542 was added into the co-culture system.

Conclusions

Therefore, these data indicated that UCMSC could significantly enhance the tumor cell metastasis, which was due to the EMT of HCC cells induced by TGF-β.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2595-4) contains supplementary material, which is available to authorized users.

Development of a Biomimetic Chondroitin Sulfate-modified Hydrogel to Enhance the Metastasis of Tumor Cells

Tumor metastasis with resistance to anticancer therapies is the main cause of death in cancer patients. It is necessary to develop reliable tumor metastasis models that can closely recapitulate the pathophysiological features of the native tumor tissue. In this study, chondroitin sulfate (CS)-modified alginate hydrogel beads (ALG-CS) are developed to mimic the in vivo tumor microenvironment with an abnormally increased expression of CS for the promotion of tumor cell metastasis. The modification mechanism of CS on alginate hydrogel is due to the cross-linking between CS and alginate molecules via coordination of calcium ions, which enables ALG-CS to possess significantly different physical characteristics than the traditional alginate beads (ALG). And quantum chemistry calculations show that in addition to the traditional egg-box structure, novel asymmetric egg-box-like structures based on the interaction between these two kinds of polymers are also formed within ALG-CS. Moreover, tumor cell metastasis is significantly enhanced in ALG-CS compared with that in ALG, as confirmed by the increased expression of MMP genes and proteins and greater in vitro invasion ability. Therefore, ALG-CS could be a convenient and effective 3D biomimetic scaffold that would be used to construct standardized tumor metastasis models for tumor research and anticancer drug screening.

The knee joint loose body as a source of viable autologous human chondrocytes

Loose bodies are fragments of cartilage or bone present in the synovial fluid. In the present study we assessed if loose bodies could be used as a source of autologous human chondrocytes for experimental purposes. Histochemical examination of loose bodies and differential enzymatic digestions were undertaken, the isolated cells were cultured in alginate bead microspheres and immunolocalisations were undertaken for chondrogenic markers such as aggrecan, and type II collagen. Isolated loose body cells had high viability (≥90% viable), expressed chondrogenic markers (aggrecan, type II collagen) but no type I collagen. Loose bodies may be a useful source of autologous chondrocytes of high viability.

Sirt1 Is Required for Resveratrol-Mediated Chemopreventive Effects in Colorectal Cancer Cells

Sirt1 is a NAD⁺-dependent protein-modifying enzyme involved in regulating gene expression, DNA damage repair, metabolism and survival, as well as acts as an important subcellular target of resveratrol. The complex mechanisms underlying Sirt1 signaling during carcinogenesis remain controversial, as it can serve both as a tumor promoter and suppressor. Whether resveratrol-mediated chemopreventive effects are mediated via Sirt1 in CRC growth and metastasis remains unclear; which was the subject of this study. We found that resveratrol suppressed proliferation and invasion of two different human CRC cells in a dose-dependent manner, and interestingly, this was accompanied with a significant decrease in Ki-67 expression. By transient transfection of CRC cells with Sirt1-ASO, we demonstrated that the anti-tumor effects of resveratrol on cells was abolished, suggesting the essential role of this enzyme in the resveratrol signaling pathway. Moreover, resveratrol downregulated nuclear localization of NF-κB, NF-κB phosphorylation and its acetylation, causing attenuation of NF-κB-regulated gene products (MMP-9, CXCR4) involved in tumor-invasion and metastasis. Finally, Sirt1 was found to interact directly with NF-κB, and resveratrol did not suppress Sirt1-ASO-induced NF-κB phosphorylation, acetylation and NF-κB-regulated gene products. Overall, our results demonstrate that resveratrol can suppress tumorigenesis, at least in part by targeting Sirt1 and suppression of NF-κB activation.

Generation and functional assessment of 3D multicellular spheroids in droplet based microfluidics platform

Here we describe a robust, microfluidic technique to generate and analyze 3D tumor spheroids, which resembles tumor microenvironment and can be used as a more effective preclinical drug testing and screening model. Monodisperse cell-laden alginate droplets were generated in polydimethylsiloxane (PDMS) microfluidic devices that combine T-junction droplet generation and external gelation for spheroid formation. The proposed approach has the capability to incorporate multiple cell types. For the purposes of our study, we generated spheroids with breast cancer cell lines (MCF-7 drug sensitive and resistant) and co-culture spheroids of MCF-7 together with a fibroblast cell line (HS-5). The device has the capability to house 1000 spheroids on chip for drug screening and other functional analysis. Cellular viability of spheroids in the array part of the device was maintained for two weeks by continuous perfusion of complete media into the device. The functional performance of our 3D tumor models and a dose dependent response of standard chemotherapeutic drug, doxorubicin (Dox) and standard drug combination Dox and paclitaxel (PCT) was analyzed on our chip-based platform. Altogether, our work provides a simple and novel, in vitro platform to generate, image and analyze uniform, 3D monodisperse alginate hydrogel tumors for various omic studies and therapeutic efficiency screening, an important translational step before in vivo studies.

Biomek Cell Workstation: A Flexible System for Automated 3D Cell Cultivation

The shift from 2D cultures to 3D cultures enables improvement in cell culture research due to better mimicking of in vivo cell behavior and environmental conditions. Different cell lines and applications require altered 3D constructs. The automation of the manufacturing and screening processes can advance the charge stability, quality, repeatability, and precision. In this study we integrated the automated production of three 3D cell constructs (alginate beads, spheroid cultures, pellet cultures) using the Biomek Cell Workstation and compared them with the traditional manual methods and their consequent bioscreening processes (proliferation, toxicity; days 14 and 35) using a high-throughput screening system. Moreover, the possible influence of antibiotics (penicillin/streptomycin) on the production and screening processes was investigated. The cytotoxicity of automatically produced 3D cell cultures (with and without antibiotics) was mainly decreased. The proliferation showed mainly similar or increased results for the automatically produced 3D constructs. We concluded that the traditional manual methods can be replaced by the automated processes. Furthermore, the formation, cultivation, and screenings can be performed without antibiotics to prevent possible effects.

3 dimensional cell cultures: a comparison between manually and automatically produced alginate beads

Cancer diseases are a common problem of the population caused by age and increased harmful environmental influences. Herein, new therapeutic strategies and compound screenings are necessary. The regular 2D cultivation has to be replaced by three dimensional cell culturing (3D) for better simulation of in vivo conditions. The 3D cultivation with alginate matrix is an appropriate method for encapsulate cells to form cancer constructs. The automated manufacturing of alginate beads might be an ultimate method for large-scaled manufacturing constructs similar to cancer tissue. The aim of this study was the integration of full automated systems for the production, cultivation and screening of 3D cell cultures. We compared the automated methods with the regular manual processes. Furthermore, we investigated the influence of antibiotics on these 3D cell culture systems. The alginate beads were formed by automated and manual procedures. The automated steps were processes by the Biomek(®) Cell Workstation (celisca, Rostock, Germany). The proliferation and toxicity were manually and automatically evaluated at day 14 and 35 of cultivation. The results visualized an accumulation and expansion of cell aggregates over the period of incubation. However, the proliferation and toxicity were faintly and partly significantly decreased on day 35 compared to day 14. The comparison of the manual and automated methods displayed similar results. We conclude that the manual production process could be replaced by the automation. Using automation, 3D cell cultures can be produced in industrial scale and improve the drug development and screening to treat serious illnesses like cancer.

The application of engineered liver tissues for novel drug discovery

INTRODUCTION

Drug-induced liver injury remains a major cause of drug attrition. Furthermore, novel drugs are being developed for treating liver diseases. However, differences between animals and humans in liver pathways necessitate the use of human-relevant liver models to complement live animal testing during preclinical drug development. Microfabrication tools and synthetic biomaterials now allow for the creation of tissue subunits that display more physiologically relevant and long-term liver functions than possible with declining monolayers.

AREAS COVERED

The authors discuss acellular enzyme platforms, two-dimensional micropatterned co-cultures, three-dimensional spheroidal cultures, microfluidic perfusion, liver slices and humanized rodent models. They also present the use of cell lines, primary liver cells and induced pluripotent stem cell-derived human hepatocyte-like cells in the creation of cell-based models and discuss in silico approaches that allow integration and modeling of the datasets from these models. Finally, the authors describe the application of liver models for the discovery of novel therapeutics for liver diseases.

EXPERT OPINION

Engineered liver models with varying levels of in vivo-like complexities provide investigators with the opportunity to develop assays with sufficient complexity and required throughput. Control over cell-cell interactions and co-culture with stromal cells in both two dimension and three dimension are critical for enabling stable liver models. The validation of liver models with diverse sets of compounds for different applications, coupled with an analysis of cost:benefit ratio, is important for model adoption for routine screening. Ultimately, engineered liver models could significantly reduce drug development costs and enable the development of more efficacious and safer therapeutics for liver diseases.

Three-dimensional in vitro tumor models for cancer research and drug evaluation

Cancer occurs when cells acquire genomic instability and inflammation, produce abnormal levels of epigenetic factors/proteins and tumor suppressors, reprogram the energy metabolism and evade immune destruction, leading to the disruption of cell cycle/normal growth. An early event in carcinogenesis is loss of polarity and detachment from the natural basement membrane, allowing cells to form distinct three-dimensional (3D) structures that interact with each other and with the surrounding microenvironment. Although valuable information has been accumulated from traditional in vitro studies in which cells are grown on flat and hard plastic surfaces (2D culture), this culture condition does not reflect the essential features of tumor tissues. Further, fundamental understanding of cancer metastasis cannot be obtained readily from 2D studies because they lack the complex and dynamic cell-cell communications and cell-matrix interactions that occur during cancer metastasis. These shortcomings, along with lack of spatial depth and cell connectivity, limit the applicability of 2D cultures to accurate testing of pharmacologically active compounds, free or sequestered in nanoparticles. To recapitulate features of native tumor microenvironments, various biomimetic 3D tumor models have been developed to incorporate cancer and stromal cells, relevant matrix components, and biochemical and biophysical cues, into one spatially and temporally integrated system. In this article, we review recent advances in creating 3D tumor models employing tissue engineering principles. We then evaluate the utilities of these novel models for the testing of anticancer drugs and their delivery systems. We highlight the profound differences in responses from 3D in vitro tumors and conventional monolayer cultures. Overall, strategic integration of biological principles and engineering approaches will both improve understanding of tumor progression and invasion and support discovery of more personalized first line treatments for cancer patients.

Potential effect of matrix stiffness on the enrichment of tumor initiating cells under three-dimensional culture conditions

Cancer stem cell (CSC) or tumor initiating cell (TIC) plays an important role in tumor progression and metastasis. Biophysical forces in tumor microenvironment have an important effect on tumor formation and development. In this study, the potential effect of matrix stiffness on the biological characteristics of human head and neck squamous cell carcinoma (HNSCC) TICs, especially the enrichment of HNSCC TICs, was investigated under three-dimensional (3D) culture conditions by means of alginate gel (ALG) beads with different matrix stiffnesses. ALG beads with soft (21 kPa), moderate (70 kPa) and hard (105 kPa) stiffness were generated by changing alginate concentration. It was found that significant HNSCC TIC enrichment was achieved in the ALG beads with moderate matrix stiffness (70 kPa). The gene expression of stemness markers Oct3/4 and Nanog, TIC markers CD44 and ABCG2 was enhanced in cells under this moderate (70 kPa) stiffness. HNSCC TIC proportion was also highly enriched under moderate matrix stiffness, accompanying with higher tumorigenicity, metastatic ability and drug resistance. And it was also found that the possible molecular mechanism underlying the regulated TIC properties by matrix stiffness under 3D culture conditions was significantly different from 2D culture condition. Therefore, the results achieved in this study indicated that 3D biophysical microenvironment had an important effect on TIC characteristics and alginate-based biomimetic scaffolds could be utilized as a proper platform to investigate the interaction between tumor cells and 3D microenvironment.

Enrichment of cancer stem cell-like cells by culture in alginate gel beads

Cancer stem cells (CSCs) are most likely the reason of cancer reoccurrence and metastasis. For further elucidation of the mechanism underlying the characteristics of CSCs, it is necessary to develop efficient culture systems to culture and expand CSCs. In this study, a three-dimensional (3D) culture system based on alginate gel (ALG) beads was reported to enrich CSCs. Two cell lines derived from different histologic origins were encapsulated in ALG beads respectively and the expansion of CSCs was investigated. Compared with two-dimensional (2D) culture, the proportion of cells with CSC-like phenotypes was significantly increased in ALG beads. Expression levels of CSC-related genes were greater in ALG beads than in 2D culture. The increase of CSC proportion after being cultured within ALG beads was further confirmed by enhanced tumorigenicity in vivo. Moreover, increased metastasis ability and higher anti-cancer drug resistance were also observed in 3D-cultured cells. Furthermore, we found that it was hypoxia, through the upregulation of hypoxia-inducible factors (HIFs) that occurred in ALG beads to induce the increasing of CSC proportion. Therefore, ALG bead was an efficient culture system for CSC enrichment, which might provide a useful platform for CSC research and promote the development of new anti-cancer therapies targeting CSCs.