MDCK cells, an acronym for Madin-Darby Canine Kidney cells, are a widely utilized model in biomedical research. This cell line originated in 1958, derived from the kidney tissue of an adult female cocker spaniel. Stewart H. Madin and Norman B. Darby Jr. isolated these epithelial cells from kidney tubules to study viral infections in mammalian cells.
MDCK cells are an immortalized cell line, able to grow and divide indefinitely under laboratory conditions. Their enduring nature allows scientists to maintain consistent cell populations for long-term studies, making them a reliable and reproducible tool.
The Defining Features of MDCK Cells
MDCK cells are epithelial cells, forming structures that mimic natural tissue barriers within the body. They develop into a “polarized monolayer” when cultured. In this single, tightly packed sheet, each cell exhibits distinct top (apical) and bottom (basolateral) surfaces, mirroring the structure of tissues like the lining of kidney tubules or intestines.
This cellular polarization is maintained by specialized structures known as “tight junctions” that form between individual cells in the monolayer. These junctions act like the mortar between bricks in a wall, creating a strong, selectively permeable barrier that controls the passage of substances between cells. The integrity of these tight junctions is influenced by factors such as calcium ions, which are involved in maintaining the barrier’s function.
Applications in Virology and Vaccine Development
MDCK cells serve as a host system for studying various viruses, including influenza. Their living nature allows viruses to replicate within them, providing researchers with a controlled environment to observe viral life cycles and interactions. This makes them particularly useful for understanding how different viruses infect and spread within a host.
A prominent application is their use in influenza virus research and vaccine production. Scientists can grow large quantities of influenza virus in MDCK cells, which then serve as the source material for vaccine manufacturing. This cell-based approach offers a modern alternative to traditional egg-based vaccine production methods, potentially providing a more flexible and rapid manufacturing platform. The World Health Organization has recognized mammalian cell lines like MDCK for influenza virus culture since 1995, highlighting their importance in vaccine development.
Role in Cellular and Pharmaceutical Research
Beyond virology, MDCK cells are applicable in other areas of cellular and pharmaceutical research. Their polarized monolayer structure and tight junctions are especially beneficial for drug transport studies. Researchers use these cell layers to investigate how potential drug compounds are absorbed and transported across a biological barrier, which helps predict how the drug might behave in the human body.
MDCK cells also function as a model system for fundamental cell biology, enabling scientists to explore how epithelial cells establish and maintain their distinct apical and basolateral polarity. They are also used to study the formation and function of various cell junctions, including tight junctions, adherens junctions, and desmosomes. Additionally, MDCK cells are employed in toxicity studies to assess the potential harmful effects of chemicals on kidney cells, contributing to drug safety assessments.
Variations and Strains
Different MDCK sub-types or strains have emerged over decades of laboratory use. The two most commonly studied types are MDCK I and MDCK II. These strains primarily differ in the “tightness” of their cell-to-cell junctions, a property measured as transepithelial electrical resistance (TER).
MDCK I cells are known to form a much more resistant, less “leaky” barrier, exhibiting very high TER values, sometimes exceeding 4000 Ω·cm². In contrast, MDCK II cells form a “leakier” barrier with significantly lower TER values, typically less than 300 Ω·cm². This difference in permeability allows researchers to select the specific MDCK strain that best mimics the particular biological barrier they intend to study, providing flexibility in experimental design.