Opportunities and challenges for use of tumor spheroids as models to test drug delivery and efficacy

Department of Periodontics & Oral Medicine, University of Michigan School of Dentistry, The University of Michigan, Ann Arbor, MI 48109-2099, United States.
Journal of Controlled Release (Impact Factor: 7.71). 05/2012; 164(2). DOI: 10.1016/j.jconrel.2012.04.045
Source: PubMed


Multicellular spheroids are three dimensional in vitro microscale tissue analogs. The current article examines the suitability of spheroids as an in vitro platform for testing drug delivery systems. Spheroids model critical physiologic parameters present in vivo, including complex multicellular architecture, barriers to mass transport, and extracellular matrix deposition. Relative to two-dimensional cultures, spheroids also provide better target cells for drug testing and are appropriate in vitro models for studies of drug penetration. Key challenges associated with creation of uniformly sized spheroids, spheroids with small number of cells and co-culture spheroids are emphasized in the article. Moreover, the assay techniques required for the characterization of drug delivery and efficacy in spheroids and the challenges associated with such studies are discussed. Examples for the use of spheroids in drug delivery and testing are also emphasized. By addressing these challenges with possible solutions, multicellular spheroids are becoming an increasingly useful in vitro tool for drug screening and delivery to pathological tissues and organs.

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    • "The different strategies that have been conceived for the fabrication of the micromodules can be divided in two main categories: scaffoldfree and scaffold-based approaches. The former comprises cellular spheroids used as a bio-ink in organ printing technology to fabricate complex architectures , such as blood vessels[3,4]and, also, as micrometric tissue replica for in vitro screening applications5678. Nevertheless, being spheroids mainly composed by cell-aggregates, the cell–extracellular matrix (ECM) interactions could result less frequent than cell–cell interactions91011. "

    Full-text · Article · Jan 2016 · Biofabrication
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    • "In the context of tumor cell cultures, most bioreactor-based approaches have introduced agitation techniques and microfluidic platforms [17e19], generating hydrodynamic conditions in the form of convectional fluid flow around cells and tissues. However, resulting superficial flows in those systems are of limited effectiveness to address internal transport limitations [20], which in turn critically affect cell behavior and function as well as drug penetration [21]. Bioreactor devices applying direct perfusion were shown to provide uniform cell distribution [22], allowing the development and maintenance of uniformly viable large tissues for prolonged culture times [22] [23]. "
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    ABSTRACT: Anticancer compound screening on 2D cell cultures poorly predicts "in vivo" performance, while conventional 3D culture systems are usually characterized by limited cell proliferation, failing to produce tissue-like-structures (TLS) suitable for drug testing. We addressed engineering of TLS by culturing cancer cells in porous scaffolds under perfusion flow. Colorectal cancer (CRC) HT-29 cells were cultured in 2D, on collagen sponges in static conditions or in perfused bioreactors, or injected subcutaneously in immunodeficient mice. Perfused 3D (p3D) cultures resulted in significantly higher (p < 0.0001) cell proliferation than static 3D (s3D) cultures and yielded more homogeneous TLS, with morphology and phenotypes similar to xenografts. Transcriptome analysis revealed a high correlation between xenografts and p3D cultures, particularly for gene clusters regulating apoptotic processes and response to hypoxia. Treatment with 5-Fluorouracil (5-FU), a frequently used but often clinically ineffective chemotherapy drug, induced apoptosis, down-regulation of anti-apoptotic genes (BCL-2, TRAF1, and c-FLIP) and decreased cell numbers in 2D, but only "nucleolar stress" in p3D and xenografts. Conversely, BCL-2 inhibitor ABT-199 induced cytotoxic effects in p3D but not in 2D cultures. Our findings advocate the importance of perfusion flow in 3D cultures of tumor cells to efficiently mimic functional features observed "in vivo" and to test anticancer compounds. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Full-text · Article · Sep 2015 · Biomaterials
    • "Once built, to proceed with high-content screening experiments [20], the spheroids are then typically manually transferred (by using a pipette) in multi-well plates (one spheroid for well), typically a 384 [21] or a 96-well plate [22]. The morpho-biological organization of the cells composing the spheroids largely depends on the spheroids' size [12] [23] [24]. In particular, the gradient of oxygen and glucose from the outer cell layers determines a stratification of cells characterized by different proliferation ratios [25]. "
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    ABSTRACT: Today, more and more biological laboratories use 3D cell cultures and tissues grown in vitro as a 3D model of in vivo tumours and metastases. In the last decades, it has been extensively established that multicellular spheroids represent an efficient model to validate effects of drugs and treatments for human care applications. However, a lack of methods for quantitative analysis limits the usage of spheroids as models for routine experiments. Several methods have been proposed in literature to perform high throughput experiments employing spheroids by automatically computing different morphological parameters, such as diameter, volume and sphericity. Nevertheless, these systems are typically grounded on expensive automated technologies, that make the suggested solutions affordable only for a limited subset of laboratories, frequently performing high content screening analysis. In this work we propose AnaSP, an open source software suitable for automatically estimating several morphological parameters of spheroids, by simply analyzing brightfield images acquired with a standard widefield microscope, also not endowed with a motorized stage. The experiments performed proved sensitivity and precision of the segmentation method proposed, and excellent reliability of AnaSP to compute several morphological parameters of spheroids imaged in different conditions. AnaSP is distributed as an open source software tool. Its modular architecture and graphical user interface make it attractive also for researchers who do not work in areas of computer vision and suitable for both high content screenings and occasional spheroid-based experiments. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
    No preview · Article · Feb 2015 · Computer Methods and Programs in Biomedicine
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