MDCK cell line

To meet the need of conducting HTS for ADME-Tox properties, many slow and expensive in vivo ADME assays are now being replaced by in vitro cell models. For intestinal absorption, Caco-2 cell lines and Madin Darby canine kidney (MDCK) cell lines are widely used to predict the absorption rate of candidate drug compounds across the intestinal epithelial cell barrier. A number of models for Caco-2 cell permeability and MDCK cell permeability have been reported that predict the oral absorption properties of drugs, mostly limited to small organic molecules. Caco-2 and MDCK permeability are related to "A" and "D" in the ADME-Tox. 

Wang, Q., Rager, J.D., Weinstein, K., Kardos, P.S., Dobson, G.L., Li, J. and Hidalgo, l.J. (2005) Evaluation of the MDR-MDCK cell line as a permeability screen for the blood-brain barrier. International Journal of Pharmaceutics, 288, 349-359. 

While Caco-2 cells typically require 21 days to become suitable for use, the Madin-Darby Canine Kidney (MDCK) cell line, derived from the dog kidney, typically only requires 3 days. This cell-line may prove to be a useful alternative, as the two cell lines show many common features. More investigation is required into how comparable the two systems are. 

Early assessment of the ability of a drug candidate to penetrate the CNS is critical during the drug discovery selection process, especially for therapeutic indications that require delivery to a CNS site of action. Equally important is the ability to design drugs for non-CNS indications that have minimal brain penetration to avoid undesirable CNS side effects. In vitro BBB models using primary and immortalized brain capillary endothelial cells are described in the previous sections. The Ma-dine Darby canine kidney (MDCK) cell-line is increasingly used as a substitute for the more labor-intensive in vitro BBB models in passive permeability and membrane transport studies. 

Most cell lines have lost some or many of the functions characteristic of the differentiated cells from which they were derived. Such relatively undifferentiated cells are poor models for investigating the normal functions of specific cell types. Better in this regard are several more-differentiated cell lines that exhibit many properties of normal nontransformed cells. These lines Include the liver tumor (hepatoma) HepG2 line, which synthesizes most of the serum proteins made by normal liver cells (hepatocytes). Another example consists of cells from a certain cultured fibroblast line, which under certain experimental conditions behave as muscle precursor cells, or myoblasts. These cells can be Induced to fuse to form myotubes, which resemble differentiated multlnucleated muscle cells and synthesize many of the specialized proteins associated with contraction. The results of studies with this cell line have provided valuable information about the differentiation of muscle (Chapter 22). Finally, as discussed previously, the MDCK cell line retains many properties of highly differentiated epithelial cells and forms well-defined epithelial sheets in culture (see Figure 6-6). 

Compilation of descriptors, size of datasets, and statistical models used, and accuracy of published in silico absorption models. Several classification models can be found in the literature, which are regarded as qualitative models and therefore not reported. Caco-2 and FA data were selected for the compilation, since these are the main responses used in the development of computational models. However, other responses such as permeability in 2/4/A1 cell monolayers, artificial membranes, and the MDCK cell line, have also been used as responses in the computational model development. 

An additional in vitro approach that can provide valuable insight into the possible influence on BSEP inhibition of cooperative interactions with other transporters is by studying vectorial transport of probe substrates using transfected ceUs cultured as confluent monolayers in transwell devices. This approach enables quantification of both basal-to-apical transport through the cells and apical efflux. In these studies it is important to use polarized epithelial cells that express distinct apical and basolateral sinusoidal plasma membrane domains and that also exhibit a low level of endogenous expression of transporters other than BSEP that may mediate apical probe substrate efflux. Appropriate cells include dog kidney-derived MDCK cell lines and porcine kidney-derived LLC-PKl cells. It is also necessary to ensure that basolateral solute carriers are present in the cells that mediate probe substrate uptake. This may require coexpression of BSEP and relevant uptake transporter(s). MDCK cell lines... 

The LLC-PKl and MDCK cell lines are pig and dog kidney epithelial cells, respectively, that require shorter culture (4-A days) periods for monolayer formation in the transwell system. These two cell lines present their own set of challenges for data interpretation. LLC-PKl cells have endogenous BCRP activity (Jonker et al., 2000). MDCKI cells have high endogenous P-gp activity (Raggers et al., 2002 Goh et al., 2002). 

Transwell experiments were also performed to investigate BoNT / A transcytosis across a human pulmonary adenocarcinoma cell line (Calu-3), the MDCK cell line, and a primary rat alveolar epithelial cell line (Park and Simpson, 2003). Efficient BoNT/A transcytosis in both directions across polarized Calu-3 monolayers was observed, while toxin transcytosis occurred at a much lower rate across MDCK cells. These findings were in agreement with previous work demonstrating that the efficiency of BoNT/A transcytosis across MEXZK mono-layers was much lower than that observed across gut epithelial cells (Maksymowych and Simpson, 1998). BoNT/ A transcytosis was also observed across primary rat alveolar cells, although at a slightly slower rate than that seen for the human adenocarcinoma cells (Park... 

The Madin-Darby canine kidney (MDCK) cell model is another commonly used cell monolayer system for the assessment of human intestinal absorption. MDCK cell lines offer a couple of key advantages over Caco-2 cells, including the ability to reach full differentiation in 3-7 days (as opposed to 21 days for Caco-2) as well as the ability to be co-transfected with Pgp, the primary intestinal efflux transporter. Good correlation has been observed between MDCK permeability and human absorption. " The primary disadvantage of the MDCK ceU line is that it is derived from canine, rather than human, cells and, as such, expression of transporters and metaboUzing enzymes is not identical. 

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