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Feature Articles: July 01, 2017 (Vol. 37, No. 13)

GEN Roundup: Watch This 3D Cell Culture Space

Possibilities for Basic Research, Drug Discovery, and Therapeutics Expand Geometrically

  • Once confined to disease modeling and drug safety testing, 3D cell culture is expanding in multiple directions, exploring new possibilities in basic research, drug discovery, and therapeutics. In basic research, 3D cell culture is being used to establish models of disease and unravel the mysteries of differentiation. In drug discovery, 3D cell culture is demonstrating that it isn’t just for toxicology—it can be adapted for target identification and drug candidate screening, too. And in therapeutics, 3D cell culture promises to realize several exciting applications, from patient-specific drug-efficacy screening to the manufacturing of bioprinted organs.

    These possibilities are coming within our grasp because 3D cell culture, unlike 2D cell culture, has depth—and not just in the obvious geometrical sense. 3D cell culture captures structural and organizational variations, and hence physiological variations, that can help it represent real, living tissue far better than 2D cell culture ever could. 3D cell culture, besides being more convenient than animal models (and relatively free of ethical issues), permits extraordinary control—from the genetic level upward.

    In addition to raising the possibility of patient-specific models, 3D cell culture could progress beyond relatively simple self-aggregated spheroids to replicate all manner of developmental contingencies in environments consisting of multiple cell types and diverse extracellular elements. And if that means manipulating cells magnetically or embedding them in microfluidic structures, so be it.

    Realizing these heady possibilities is a daunting challenge. It’s on the order of transitioning from checkers to chess—three-dimensional chess. Fortunately, it isn’t beyond our panel of experts. Consider them the grandmasters of 3D cell culture. For your edification, they have answered our questions about 3D cell culture’s opening game, as well as how the endgame may develop. 

  • GEN: Are 3D cell culture models as strongly focused as ever on drug safety testing, or are they finding new applications?

    Dr. Aho: The focus of 3D cell culture models has definitely expanded beyond drug safety testing. It is becoming increasingly clear that these models mimic cells in vivo at a greater capacity than traditional cell culture.

    In addition to drug toxicity, 3D models are progressively being developed and used in developmental biology research, disease modeling, and regenerative medicine. 3D models also provide an enhanced system for drug discovery. Because they better recapitulate disease in vitro, 3D models have the potential to accelerate the testing timeline for drug efficacy studies.

    Dr. Banks: Another major application area of 3D cell culture models is in oncology. Spheroids in both media and Matrigel® can be used as surrogate models of tumor proliferation and tumor invasion. Automated brightfield or fluorescence microscopy is typically used for spheroid or invadipodia area measurements. In addition to spheroids, collagen-based scaffolds that encourage cell aggregation into tumoroids have been used for immunotherapy applications such as natural killer cell cytotoxicity assays. Finally, magnetic particles have been used to bioprint cells for cell migration and invasion experiments.

    Dr. Eglen: We would argue that 3D cell culture models have been used for many years in basic research and disease modeling, notably in cancer research—this was, after all, one of the original applications of Corning® Matrigel®, a naturally occurring extracellular matrix for us in 3D cell culture. That said, it is true that 3D cell culture models are increasingly being used in preclinical lead optimization, particularly in evaluating potential compound toxicity and metabolic liability.

    Furthermore, disease research areas are expanding to include neurology, stem cell research, cell therapy, and (potentially) tissue engineering. Perhaps the most exciting work is the development of 3D technologies for the optimal production of patient-specific cells, either for compound testing or possibly cell therapy.

    Interestingly, spheroids derived from stem cells grown in 3D models show improved “stemness,” that is, characteristics that may lead to increased efficacy in regenerative medicine. Researchers have seen that spheroids display enhanced anti-inflammatory, tissue regenerative, and reparative responses, as well as better post-transplant survival of mesenchymal stem cells.

    Autologous tissue for transplantation may also come from organoids produced via 3D cell culture. For example, renal organoids derived from pluripotent stem cells have been successfully transplanted under the renal capsules of adult mice. Clearly, research in this area is advancing rapidly, probably due to a convergence of several multidisciplinary fields, ranging from bioengineering, materials science, phenotypic screening, and cell biology.

    Dr. Trezise: Drug safety continues to be a significant application area for 3D models. This application area has become only more interesting as more data has become available indicating that 3D models offer translational benefits. In addition, there is a growing trend to develop 3D models that can advance developmental biology, target validation, and drug efficacy studies. This trend is particularly evident in the field of oncology, where researchers are combining patient-specific tumor cells and 3D cell culture methods to create tumor organoids. These mini-tumors are being used to determine sensitivity to combinations of different chemical, biological, and cellular therapeutics in the context of personalized medicine.

    Dr. Klette: 3D cell culture models are widely used for drug safety testing, such as studying hepatic injury from compound screens, and for examining drug metabolism using 3D hepatocyte models. In personalized medicine, however, patient-derived primary 3D models are being used for cancer screening in biotherapeutics. Here, 3D models provide enhanced physiological relevance to determine drug efficacy and potential impacts on carcinogenesis, metastasis, and tumor reoccurrence. If we look outside drug discovery and biologics, we notice that areas such as regenerative medicine and cell therapies can take advantage of 3D models as a predictor of disease and (when scaled to therapeutic levels) as a disease treatment.

    Dr. Guye: 3D cell models are applied throughout the biomedical and life sciences. 3D technologies that are compatible with high-throughput screening are used not only for screening purposes, but also for target and hit validation, lead optimization, and investigational toxicology.

    Basically, given their ability to extend cell lifetimes and incorporate multiple cell types, 3D models are increasingly finding their way into basic research, where they are helping to recapitulate disease progression and assess the impact of certain genes and pathways on disease progression/prevention—activities that help scientists define adverse outcome pathways. Importantly, we expect human 3D cell culture models to significantly reduce the percentage of drugs that progress to clinical trials and fail due to lack of efficacy.

    Dr. Kugelmeier: The focus on drug safety testing is still valid, and sophisticated organoid models might contribute to even more accurate drug safety testing because of increased physiological fidelity of these models. But there are also significant new research areas. Combining organoid technology with stem cell biology could lead to therapeutic applications. Also, cancer research—especially cancer research that focuses on cancer stem cells—needs 3D models. Of these models, cell spheroids are among the most important. Sophisticated cell-spheroid platforms not only allow research but also provide drug-testing possibilities using patient cells for personalized medicine. Finally, these platforms may enable therapeutic applications with stem cell spheroids in regenerative medicine.

    Mrs. Hussain: The focus for 3D cell culture methods is still the drug safety testing that occurs before in vivo testing. Recently, there has been a renewed interest in phenotypic drug screening to discover new drug targets. With this shift, there is growing emphasis on bridging the gap between phenotypic screens and 3D methods. Phenotypic screens, in vitro, were traditionally carried out using 2D methods that do not take into account the complexity of the in vivo environment. 3D methods are now sought to build biologically relevant models that are more predictive of phenotypic response to new drug targets.

    Dr. Bulpin: Applications continue to expand for 3D models, including the development of specific disease models and complex tissue models that can be used for basic research as well as drug discovery. Another promising area for 3D models is personalized medicine. Several types of cells can be used in these models including “immortalized” cells, genetically engineered cells, induced pluripotent stem cell–derived cells, primary human cells, and patient-derived cells (including patient-derived xenografts). Another potential research avenue is engineering 3D tissues for organ transplants.

    Dr. Joore: Over the last year, we observed a growing interest in 3D tissue models that could be used in studies of disease processes, whether the studies emphasized screening or efficacy analysis. These are, I think, two sides of the same coin. Once researchers realize they need better predictive models for safety testing, they start to see that improved models would also have potential for discovery and development. Molecule-to-molecule screens have generated lots of very specific inhibitors, but not so many therapies. Researchers are now starting to appreciate the richness of 3D model data, especially in combination with the throughput of our organ-on-a-chip platforms.

    Ms. Floyd: Cancer researchers and developmental biologists have certainly benefitted from 3D cell culture models, which are more physiologically relevant than are 2D systems to the study of cellular differentiation. Further, 3D in vitro systems are well positioned to obtain approvals from authorities such as the Organization for Economic Co-operation and Development Organization (OECD). The OECD and other bodies are considering alternatives to whole-animal testing, including alternatives that can accomplish skin-sensitization studies for the safety assessment of chemicals.

    Prof. Przyborski: What has changed more recently is the ease of access to innovative technologies on the market that enable researchers to more readily practice 3D cell culture routinely. 3D cell culture has had impact in multiple areas in basic research, drug screening, and safety assessment. Researchers are now looking to 3D technologies to create more sophisticated models that are representative of real human tissues. Investment in more advanced in vitro assays at an early stage will improve predictions of drug action and inform the decision-making process as to whether to further invest in a particular drug candidate.

    Dr. Kennedy: 3D cell cultures continue to be extensively explored for drug safety screening; however, there is a growing interest in expanding the use of more complex 3D models into areas such as disease modeling and precision medicine. For example, preclinical hepatic research is now looking to exploit the benefits of spheroid cultures by building 3D co-culture models that consist of multiple primary liver cell types to create new models of hepatic and biliary disease. Likewise, stem cell–derived organoids are opening the possibility of tailoring therapeutic regimens to patients’ genetic makeups and to identify the best treatment options.