Cultured cells are cells grown in a controlled environment outside their natural living organism. This process, known as cell culture, involves taking cells from a plant, animal, or human and providing them with an artificial environment where they can survive and multiply. Growing cells in this manner serves as a fundamental scientific tool, offering a simplified and controllable system for studying various biological processes without the complexities of a whole organism.
What Are Cultured Cells?
The concept of growing cells outside their natural body is referred to as in vitro (Latin for “in glass”), contrasting with in vivo (Latin for “within the living organism”) studies that occur within a whole living being. In cell culture, cells are removed from living tissue and then placed in a carefully controlled artificial environment. This allows scientists to observe cellular behavior and responses in isolation, offering a clearer understanding of specific biological phenomena.
There are two main categories of cultured cells: primary cells and immortalized cell lines. Primary cells are directly isolated from tissues, such as fibroblasts from skin biopsies or hepatocytes from liver explants. These cells maintain many characteristics of their original tissue and are valuable for studies requiring high physiological relevance, though they have a limited lifespan. In contrast, immortalized cell lines are derived from primary cells but have undergone genetic modifications or natural mutations that allow them to proliferate indefinitely. While immortalized lines offer consistency and an unlimited supply for research, they may lose some of the original characteristics of their primary cell counterparts over time.
How Cells Are Grown
Growing cells in a laboratory requires a sterile environment to prevent contamination from microorganisms. This sterility is achieved through aseptic technique, a set of procedures that create a barrier between environmental microbes and the cell culture. This includes routinely sanitizing work surfaces and personal protective equipment with a 70% alcohol solution, and minimizing rapid movements or unnecessary opening of culture vessels to maintain proper airflow in a biosafety cabinet.
The cells are nourished by a nutrient-rich culture medium. This medium typically contains a balanced mixture of inorganic salts for osmotic balance and pH regulation, carbohydrates like glucose as an energy source, and amino acids for protein synthesis. Additionally, vitamins, minerals, growth factors, and hormones are often included to promote cell proliferation and differentiation. Some media also contain antibiotics, such as penicillin and streptomycin, to further inhibit bacterial contamination, although their routine use is sometimes debated.
Cells are maintained under specific environmental conditions within a CO2 incubator. Most mammalian cell lines thrive at a temperature of 37°C, mimicking the human body’s internal temperature. A controlled carbon dioxide concentration works with a buffering system in the medium to maintain a stable pH. High humidity is also maintained to prevent the culture medium from evaporating. To prevent overcrowding and nutrient depletion, cells are regularly “passaged” or “subcultured” by transferring them to new vessels with fresh medium once they reach a certain density.
Applications of Cultured Cells
Cultured cells serve as tools across numerous scientific and medical disciplines. They are widely used for disease modeling, allowing scientists to investigate the progression and mechanisms of various diseases. For instance, cancer cells can be grown in three-dimensional (3D) cultures to mimic tumor growth and metastasis, providing a more accurate representation than traditional two-dimensional cultures. Similarly, neural cells are used to study neurodegenerative conditions like Alzheimer’s and Parkinson’s diseases, while lung epithelial cells aid in respiratory infection research, helping to identify potential therapeutic targets.
The utility of cultured cells extends into drug discovery and testing. They are employed to screen new drug compounds, assessing their effectiveness and evaluating their potential toxicity before moving to animal or human trials. This allows researchers to gather initial insights into how cells respond to new drugs. While in vitro studies provide a starting point, further in vivo studies are needed to understand how the whole body responds to a drug, as complex interactions within a living organism cannot be fully replicated in culture.
Cultured cells also play a role in vaccine production. Many viral vaccines, including those for polio, measles, mumps, and rubella, are produced by growing candidate vaccine viruses in specific mammalian, avian, or insect cell lines. For example, Madin-Darby Canine Kidney (MDCK) cells are frequently used for influenza vaccine production, and Vero cells (derived from African green monkey kidney) are used for vaccines against poliovirus and rabies virus. This cell-based approach offers advantages such as faster production capabilities, especially during pandemics, and a more controlled and sterile environment compared to traditional egg-based methods.
Beyond drug and vaccine development, cultured cells are important in regenerative medicine and tissue engineering. They are used to grow tissues or organs for potential transplantation or to repair damaged body parts. For example, skin cells can be cultured to produce grafts for severe burn victims, and stem cells are being explored for developing cardiac patches to repair damaged hearts. This field holds promise for addressing organ shortages and developing personalized tissue replacement therapies.
Furthermore, cultured cells are important in gene therapy research. This involves modifying or adding genes to cells to prevent or treat diseases caused by genetic defects. Scientists can modify genes in isolated cells to create disease models, investigate hereditary conditions, or develop therapeutic interventions. Techniques such as CRISPR-Cas9 gene editing are applied in cell culture to precisely alter genes, which can lead to understanding or correcting genetic errors, thereby enabling the development of new treatments.