Cells are the fundamental building blocks of all living organisms. To understand their intricate processes, scientists often study cells outside their natural environment using cell culture, which involves growing cells in a controlled laboratory setting. Cell lines are a primary tool in this field, transforming biological research and driving discoveries in medicine and biotechnology.
What Are Cell Lines?
A cell line is a population of cells that can be grown and propagated indefinitely in a laboratory. Unlike primary cells, which have a limited lifespan, cell lines divide continuously over many generations. This characteristic, called “immortalization,” means cells have overcome their natural limit on division, known as replicative senescence.
Cell lines can be subcultured repeatedly into new vessels with fresh nutrients, providing an ongoing supply of identical cells for experiments. This consistent availability makes them a valuable resource for long-term and repeatable studies.
Cell lines originate from various sources. Some come from normal tissues that undergo spontaneous changes enabling indefinite growth. More commonly, they are derived from tumor tissues, as cancer cells often exhibit uncontrolled proliferation, making them naturally immortalized. Other cell lines are intentionally modified for indefinite growth.
How Cell Lines Are Created
Creating a cell line begins with isolating cells from a tissue sample. These primary cells are then placed in an artificial environment with a nutrient-rich medium and specific environmental conditions.
To establish a continuous cell line, these primary cells must undergo immortalization. One common method involves introducing specific viral genes into the cells. These viral genes inactivate tumor suppressor proteins like p53 and Rb, which normally regulate cell division and induce senescence. Another approach involves expressing the human telomerase reverse transcriptase (hTERT) protein, which maintains telomere length, preventing cells from stopping division.
Once immortalized, cells are selected and expanded to create a stable cell line. Maintaining these cultures requires strict aseptic techniques to prevent contamination by microorganisms or other cell types. Researchers use sterile equipment and careful handling procedures to ensure purity and integrity.
Why Cell Lines Are Indispensable in Science
Cell lines serve as important models in scientific research and biotechnology due to their consistent availability and ease of manipulation. They provide a standardized, reproducible system for studying cellular processes, disease mechanisms, and the effects of various compounds. This controlled environment allows scientists to investigate complex biological questions without the complexities of a living organism.
In disease modeling, cell lines are extensively used, particularly in cancer research. Cancer cell lines, derived from tumors, allow scientists to study cancer biology, including growth, spread, and therapeutic targets. Large panels of cancer cell lines are screened to test new drug candidates, helping identify compounds that specifically target cancer cells. Cell lines also play a role in developing gene therapies and producing vaccines.
Cell lines are also employed in drug discovery and testing, assessing the toxicity and efficacy of new drugs before human trials. They are valuable for toxicology studies, evaluating potential harmful effects of chemicals on human cells. Their ability to grow large quantities of uniform cells makes them an efficient and ethical alternative to animal models for initial screenings.
Ethical and Practical Considerations
Cell lines present several practical and ethical challenges. A significant practical concern is contamination, which can occur from microorganisms or other faster-growing cell lines. Cross-contamination, where one cell line mixes with and outcompetes another, can lead to misidentification and invalidate research results. Estimates suggest that between one-fifth and one-third of all cell lines may be misidentified.
To mitigate these issues, laboratories implement stringent aseptic techniques and routinely test cell lines for purity and authenticity using methods like DNA fingerprinting. Obtaining cell lines from reputable cell banks also helps ensure their identity and quality. Failure to address misidentification can lead to wasted resources, misleading findings, and a lack of reproducibility in scientific literature.
Ethical considerations surround the origin of certain historically significant cell lines. The HeLa cell line, derived in 1951 from Henrietta Lacks’ cervical cancer cells without her informed consent, highlights the importance of ethical guidelines. While her cells contributed to countless scientific advancements, the lack of consent raised profound questions about patient rights, privacy, and commercialization. Modern research emphasizes informed consent and transparent policies for human biological materials to ensure ethical sourcing and maintain public trust.