A cell line is a population of cells derived from a living organism that can be maintained and grown indefinitely in a laboratory setting for research purposes. Among the thousands of lines available, Madin-Darby Canine Kidney (MDCK) cells are one of the most widely utilized mammalian models in biomedical research. Their popularity stems from their unique ability to organize themselves into structures that closely mimic the barriers found in the body. MDCK cells have become a standard tool for investigating various cellular functions, from how tissues absorb nutrients to how viruses spread.
Origin and Identity of MDCK Cells
The full name of the cell line, Madin-Darby Canine Kidney, reveals its origin, having been isolated in 1958 by Stewart H. Madin and Norman B. Darby Jr. The cells were derived from the kidney tubules of an adult Cocker Spaniel dog. This canine origin is significant because MDCK cells are mammalian, yet they are easier to grow and manipulate than many human cell lines, making them an accessible model for mammalian biology. MDCK cells are classified as epithelial cells, which form continuous sheets or linings on the surfaces of organs, such as the kidney tubules. These cells inherently serve a barrier function, controlling the movement of substances between two compartments.
Unique Biological Properties
The value of MDCK cells lies in their capacity to recreate a functioning biological barrier in a two-dimensional culture. When grown on a permeable surface, the cells spontaneously organize into a monolayer, a single sheet of cells that is structurally polarized. This cellular polarity means the cell has two distinct surfaces: the apical membrane, which faces the open environment, and the basolateral membrane, which faces the substrate. This organization is maintained by the tight junction, a specialized structure that acts as a molecular “seal” encircling the cells near their apical surface. Composed of proteins like ZO-1, occludin, and claudin, the tight junction physically bind adjacent cells together, restricting the passage of molecules between them and forcing them to pass directly through the cell. This measurable property is known as transepithelial resistance.
Primary Applications in Biomedical Research
Drug Transport and Screening
The highly organized and polarized nature of MDCK cells makes them an exceptional model for studying the transport of substances across tissue barriers, which is relevant in pharmacology. When grown on a permeable support, the monolayer separates the culture medium into two separate chambers, apical and basolateral, allowing researchers to accurately measure how compounds move across the cell sheet. This setup is widely used to predict how well a drug will be absorbed in the intestines or excreted by the kidneys. Researchers can genetically modify MDCK cells by introducing human transport proteins, such as P-glycoprotein (P-gp), to create more sophisticated models for drug screening. These engineered lines enable scientists to study drug efflux—the process where cells actively pump certain drugs back out—which is a major factor in determining a medicine’s effectiveness, while the barrier function provides quantitative data on drug permeability and toxicity.
Virology and Vaccine Production
MDCK cells are also a preferred system in virology, primarily for the study and production of influenza viruses. The cells are highly susceptible to infection by various strains of influenza A and B viruses, allowing researchers to monitor viral replication and test the efficacy of antiviral drugs. The polarized nature of the cells is particularly useful because it mimics the epithelial lining of the respiratory tract, providing insight into how a virus is released directionally. The World Health Organization has recognized MDCK cells as a suitable substrate for the production of seasonal influenza vaccines, offering an alternative to the traditional egg-based production method.
Renal Physiology
Beyond virology and drug transport, the kidney origin of MDCK cells allows them to be used as a simple model for renal physiology and disease. When cultured in a three-dimensional matrix, they can spontaneously organize into hollow, sphere-like structures that resemble kidney tubules. This makes them a model for investigating the cellular mechanisms behind cystic kidney diseases.