HeLa cells are a significant advancement in biomedical research. These unique cells can proliferate indefinitely in a laboratory, distinguishing them from most human cells. Their continuous growth has made them a foundational model system across diverse fields of study. Scientists worldwide use HeLa cells extensively due to their consistent behavior, aiding in the understanding of human biology and disease.
The Origin and Unique Nature of HeLa Cells
HeLa cells originated from tissue samples collected in 1951 from Henrietta Lacks, an African American woman diagnosed with cervical cancer. Her cells were obtained during a biopsy at Johns Hopkins Hospital without her knowledge or explicit consent, a common practice at the time. Researchers observed that, unlike other human cells, Lacks’s cervical cancer cells continued to divide and grow in culture. This discovery revealed their “immortality,” meaning they could proliferate indefinitely.
The resilience of HeLa cells stems from several biological factors. A key contributor is the presence of Human Papillomavirus (HPV) type 18 integrated into their genome. This viral integration disrupted tumor suppressor genes like p53 and Rb, which regulate cell growth and division, allowing the cells to bypass natural cell cycle checkpoints. HeLa cells also exhibit high levels of telomerase activity, an enzyme that rebuilds the protective caps at the ends of chromosomes called telomeres. This sustained telomerase activity prevents cellular aging and programmed cell death seen in normal human cells, enabling their perpetual division.
Cultivating HeLa Cells in the Laboratory
Cultivating HeLa cells in a laboratory requires a controlled and sterile environment to prevent contamination and promote healthy cell growth. Scientists work within laminar flow hoods, which provide a filtered air stream to maintain aseptic conditions, shielding the cells from airborne microbes. The cells are grown in specialized flasks or dishes, submerged in a cell culture medium mimicking human body conditions. This medium contains a blend of nutrients, including amino acids, vitamins, mineral salts, and glucose, along with growth factors and antibiotics to deter bacterial contamination.
Maintaining a healthy HeLa cell culture involves regular monitoring and procedures. As the cells proliferate, they will eventually cover the entire surface of their flask, a state known as confluence. To prevent overgrowth and ensure continued health, scientists perform subculturing, or “splitting” the cells, every two to three days. This process involves detaching the cells from the flask surface using enzymes like trypsin, diluting them, and transferring them to new flasks with fresh medium for more space to grow. For long-term storage, HeLa cells can be cryopreserved by freezing them slowly in a protective solution containing dimethyl sulfoxide (DMSO) and storing them in liquid nitrogen at -196 degrees Celsius for later revival and use.
HeLa Cells’ Profound Impact on Medical Research
HeLa cells have shaped medical research, serving as a consistent model system for scientific investigations. Their stable genetic makeup and ability to grow in large quantities made them valuable for developing the polio vaccine in the 1950s. Jonas Salk’s team used HeLa cells to grow large batches of the poliovirus, which enabled the testing and production of the vaccine that eradicated polio globally. This breakthrough demonstrated the potential of immortalized cell lines for vaccine development and large-scale biological production.
In cancer research, HeLa cells have been instrumental in understanding mechanisms of cell division, gene expression, and tumor progression. Scientists have used them to screen potential anti-cancer drugs, observe the effects of radiation, and investigate how genetic mutations contribute to uncontrolled cell growth. Their consistent behavior allows researchers to study complex cellular processes in a controlled environment, leading to insights into various cancers. These cells also provided a standardized system for studying cellular biology, including DNA replication, protein synthesis, and cellular signaling pathways.
HeLa cells have also played a role in virology, acting as hosts for studying various viruses. Researchers used them to understand the life cycles of viruses like HIV, helping to develop antiviral therapies. They have been used in human papillomavirus (HPV) research, providing a model to study the virus that transformed the original cells. More recently, HeLa cells have contributed to studies on emerging pathogens, including SARS-CoV-2, the COVID-19 virus, to investigate viral entry and evaluate potential therapies.
Their utility extends to genetics, for mapping genes and understanding chromosomal abnormalities, and toxicology, for assessing the effects of chemicals and environmental agents.
The Ethical Considerations and Lasting Legacy
The initial collection and use of HeLa cells sparked an ethical controversy, as Henrietta Lacks’s cells were taken without her informed consent. This lack of permission, coupled with the commercialization of the cells, highlighted a gap in medical ethics regarding patient rights and ownership of biological materials. The Lacks family remained unaware of their use for over two decades, learning about them in the 1970s. This case highlighted a historical context where patient consent for tissue samples was not routinely sought or legally required.
The story of Henrietta Lacks and her cells became a catalyst for change in biomedical research practices. It played a role in shaping modern bioethics, leading to stricter regulations and guidelines for research involving human subjects. These new policies emphasized the necessity of informed consent, ensuring individuals understand and agree to the use of their biological samples. The case also spurred discussions about patient privacy, commercialization of human tissues, and benefit-sharing from scientific discoveries. The Lacks family has since become advocates for ethical practices, engaging with researchers and institutions to ensure recognition and respect for Henrietta Lacks’s legacy, and contribute to dialogues about responsible scientific conduct.