125 research outputs found
A Mathematical Model of Liver Cell Aggregation In Vitro
The behavior of mammalian cells within three-dimensional structures is an area of intense biological research and underpins the efforts of tissue engineers to regenerate human tissues for clinical applications. In the particular case of hepatocytes (liver cells), the formation of spheroidal multicellular aggregates has been shown to improve cell viability and functionality compared to traditional monolayer culture techniques. We propose a simple mathematical model for the early stages of this aggregation process, when cell clusters form on the surface of the extracellular matrix (ECM) layer on which they are seeded. We focus on interactions between the cells and the viscoelastic ECM substrate. Governing equations for the cells, culture medium, and ECM are derived using the principles of mass and momentum balance. The model is then reduced to a system of four partial differential equations, which are investigated analytically and numerically. The model predicts that provided cells are seeded at a suitable density, aggregates with clearly defined boundaries and a spatially uniform cell density on the interior will form. While the mechanical properties of the ECM do not appear to have a significant effect, strong cell-ECM interactions can inhibit, or possibly prevent, the formation of aggregates. The paper concludes with a discussion of our key findings and suggestions for future work
In vitro Toxicity Testing of Nanoparticles in 3D Cell Culture
Common 2D cell cultures do not adequately represent the functions of 3D tissues that have extensive cellācell and cellāmatrix interactions, as well as markedly different diffusion/transport conditions. Hence, testing cytotoxicity in 2D cultures may not accurately reflect the actual toxicity of nanoparticles (NPs) and other nanostructures in the body. To obtain more adequate and detailed information about NPātissue interactions, we here introduce a 3D-spheroid-culture-based NP toxicology testing system. Hydrogel inverted colloidal crystal (ICC) scaffolds are used to create a physiologically relevant and standardized 3D liver tissue spheroid model for in vitro assay application. Toxicity of CdTe and Au NPs are tested in both 2D and 3D spheroid cultures. The results reveal that NP toxic effects are significantly reduced in the spheroid culture when compared to the 2D culture data. Tissue-like morphology and phenotypic change are identified to be the major factors in diminishing toxicity. Acting as an intermediate stage bridging in vitro 2D and in vivo, our in vitro 3D cell-culture model would extend current cellular level cytotoxicity to the tissue level, thereby improving the predictive power of in vitro NP toxicology.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62993/1/1213_ftp.pd
InVERT molding for scalable control of tissue microarchitecture
Complex tissues contain multiple cell types that are hierarchically organized within morphologically and functionally distinct compartments. Construction of engineered tissues with optimized tissue architecture has been limited by tissue fabrication techniques, which do not enable versatile microscale organization of multiple cell types in tissues of size adequate for physiological studies and tissue therapies. Here we present an āIntaglio-Void/Embed-Relief Topographic moldingā method for microscale organization of many cell types, including induced pluripotent stem cell-derived progeny, within a variety of synthetic and natural extracellular matrices and across tissues of sizes appropriate for in vitro, pre-clinical, and clinical studies. We demonstrate that compartmental placement of non-parenchymal cells relative to primary or induced pluripotent stem cell-derived hepatocytes, compartment microstructure, and cellular composition modulate hepatic functions. Configurations found to sustain physiological function in vitro also result in survival and function in mice for at least 4 weeks, demonstrating the importance of architectural optimization before implantation.National Institutes of Health (U.S.) (EB008396)National Institutes of Health (U.S.) (DK56966)National Cancer Institute (U.S.) (Cancer Center Support Core Grant P30-CA14051)National Institutes of Health (U.S.). Ruth L. Kirschstein National Research Service Award (1F32DK091007)National Institutes of Health (U.S.). Ruth L. Kirschstein National Research Service Award (1F32DK095529)National Science Foundation (U.S.). Graduate Research Fellowship Program (1122374
Three-dimensional Numerical Modeling and Computational Fluid Dynamics Simulations to Analyze and Improve Oxygen Availability in the AMC Bioartificial Liver
A numerical model to investigate fluid flow and oxygen (O(2)) transport and consumption in the AMC-Bioartificial Liver (AMC-BAL) was developed and applied to two representative micro models of the AMC-BAL with two different gas capillary patterns, each combined with two proposed hepatocyte distributions. Parameter studies were performed on each configuration to gain insight in fluid flow, shear stress distribution and oxygen availability in the AMC-BAL. We assessed the function of the internal oxygenator, the effect of changes in hepatocyte oxygen consumption parameters in time and the effect of the change from an experimental to a clinical setting. In addition, different methodologies were studied to improve cellular oxygen availability, i.e. external oxygenation of culture medium, culture medium flow rate, culture gas oxygen content (pO(2)) and the number of oxygenation capillaries. Standard operating conditions did not adequately provide all hepatocytes in the AMC-BAL with sufficient oxygen to maintain O(2) consumption at minimally 90% of maximal uptake rate. Cellular oxygen availability was optimized by increasing the number of gas capillaries and pO(2) of the oxygenation gas by a factor two. Pressure drop over the AMC-BAL and maximal shear stresses were low and not considered to be harmful. This information can be used to increase cellular efficiency and may ultimately lead to a more productive AMC-BAL
Manipulation of a quasi-natural cell block for high-efficiency transplantation of adherent somatic cells
Towards ready-to-use 3-D scaffolds for regenerative medicine: adhesion-based cryopreservation of human mesenchymal stem cells attached and spread within alginateāgelatin cryogel scaffolds
Polysaccharide production by plant cells in suspension : Experiments and mathematical modeling
Entrapment of retroviral vector producer cells in three-dimensional alginate scaffolds for potential use in cancer gene therapy
Long-term 3D culture of the SCC4 cell line using three different culture methods and initial seeding densities
Thermo-responsive non-woven scaffolds for āsmartā 3D cell culture
The thermo-responsive polymer poly(N-isopropylacrylamide) has received widespread
attention for its in vitro application in the non-invasive, non-destructive release of adherent
cells on two dimensional surfaces. In this study, 3D non-woven scaffolds fabricated from
poly(propylene) (PP), poly(ethylene terephthalate) (PET) and nylon that had been grafted
with PNIPAAm were tested for their ability to support the proliferation and subsequent
thermal release of HC04 and HepG2 hepatocytes. Hepatocyte viability and proliferation was
estimated using the Alamar Blue assay and Hoechst 33258 total DNA quantification. The
assays revealed that the pure and grafted non-woven scaffolds maintained the hepatocytes
within the matrix and promoted 3D proliferation comparable to that of the commercially available AlgimatrixTM alginate scaffold. Albumin production and selected cytochrome P450
genes expression was found to be superior in cells growing on pure and grafted non-woven
PP scaffolds as compared to cells grown as a 2D monolayer. Two scaffolds, namely, PP-g-
PNIPAAm-A and PP-g-PNIPAAm-B were identified as having far superior thermal release
capabilities; releasing the majority of the cells from the matrices within 2 h. This is the first
report for the development of 3D non-woven, thermo-responsive scaffolds able to release
cells from the matrix without the use of any enzymatic assistance or scaffold degradation.The Council for Scientific and Industrial
Researchhttp://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0290hb2016Biochemistr
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