Stem cells are unspecialized cells that can develop into many different cell types. A stem cell line is a population of these cells grown in a laboratory, derived from an initial source that can reproduce for long periods. Their ability to self-renew in a stable state while retaining the potential to specialize makes them a tool in biological research and medicine.
Major Categories of Stem Cell Lines
Stem cell lines are categorized by their origin and differentiation capabilities. Embryonic stem cell lines (ESCLs) are derived from the inner cell mass of an early-stage embryo. These cells are pluripotent, meaning they can differentiate into any cell type found in the adult body. This potential makes them a resource for studying human development.
Adult stem cell lines, also known as somatic stem cells, are sourced from tissues in a developed organism. Unlike embryonic stem cells, adult stem cells are multipotent or unipotent, meaning their differentiation is restricted to the cell types of their tissue of origin. For instance, hematopoietic stem cells from bone marrow generate blood and immune cells. Establishing stable lines from these cells is more challenging.
Induced pluripotent stem cell lines (iPSCs) are created in a lab by reprogramming specialized adult cells, such as skin cells, into a pluripotent state. This process involves introducing specific genes to reset the cell’s genetic programming. Since they can be generated from any individual, iPSCs are valuable for creating disease-specific models and personalized medicine.
Establishing and Culturing Stem Cell Lines
Establishing a stem cell line begins with isolating founder cells. These cells are grown in a controlled laboratory environment using a nutrient-rich culture medium supplemented with growth factors. These supplements signal the cells to remain undifferentiated and continue dividing. The cells are grown on a coated substrate to support their growth.
To expand the cell population, a process called passaging is performed. This involves detaching the cells from their culture dish and transferring a small number to a new dish. This method expands a small number of initial cells into millions, ensuring a large supply for research.
Cryopreservation is a step in managing cell lines that involves freezing cells at very low temperatures in liquid nitrogen. This process pauses all cellular activity, allowing the line to be stored for years and revived when needed. This ensures a stable supply for future experiments.
Applications in Scientific Discovery
Stem cell lines serve as models for scientific research. They are used to study the earliest stages of human development, allowing observation of how cells form tissues and organs. Scientists can guide their differentiation to map the genetic changes that occur along developmental pathways.
These cell lines are also used to investigate the mechanisms of disease. Using iPSC technology, a cell from a patient with a genetic disorder can be converted into a stem cell line. These patient-specific cells are then differentiated into the affected cell type, creating a “disease-in-a-dish” model. This allows scientists to study disease development at the cellular level and identify treatment targets.
Stem cell lines are a platform for studying gene function with technologies like CRISPR-Cas9. Researchers can alter or disable specific genes in a stem cell line and then observe the consequences when the cells differentiate. This uncovers the roles genes play in development and disease.
Therapeutic Potential and Development
Stem cell lines are used in translational medicine for drug discovery and toxicology. Before human testing, companies use stem cell-derived specialized cells, like heart or liver cells, to screen new drugs for efficacy and toxicity. This identifies harmful compounds early, making drug development safer and more efficient.
In regenerative medicine, stem cell lines can create cell-based therapies for repairing or replacing damaged tissues. Research is exploring treatments for conditions like spinal cord injuries, diabetes, and neurodegenerative diseases. The goal is to transplant lab-grown specialized cells into a patient to restore lost function. While many therapies are in clinical trials, hematopoietic stem cell transplantation is an established treatment for some blood and immune disorders.
iPSCs enable personalized medicine. Generating stem cell lines from a patient’s own cells can create tailored therapies that avoid immune rejection. These patient-specific cells can be used to test an individual’s drug response or to develop personalized cell replacement therapies.
Ethical Considerations and Oversight
The use of stem cell lines, particularly those from human embryos, has been the subject of ethical debate. The creation of human embryonic stem cell lines (hESCLs) raises concerns because it involves the destruction of a blastocyst. This has led to differing regulations and public funding policies globally, reflecting various viewpoints on the status of the human embryo.
The development of iPSCs provides a method for creating pluripotent stem cells without using embryos, mitigating some ethical objections. However, iPSC technology has its own considerations, including the genetic modification of human cells and potential misuse. Donating somatic cells for research also requires informed consent procedures to ensure donors understand how their cells will be used.
To address these issues, stem cell research is governed by regulatory frameworks and oversight bodies. In many countries, committees like institutional review boards (IRBs) must approve research involving human stem cells. These bodies evaluate the scientific and ethical soundness of research proposals. Standardized protocols and quality control measures are also in place to ensure the safety of cell lines for clinical use.