Summary
Highlights
Stem cells are immature cells that can replicate while maintaining the ability to specialize into various mature cell types found in our tissues. They are crucial for regenerating and repairing tissues.
Adult stem cells are found in various tissues throughout the body, such as bone marrow (responsible for blood cell regeneration) and skin (constantly renewing). They are 'professional' cells, continually replacing worn-out or damaged cells. Brain stem cells are an exception, working at a slower pace in specific areas like the hippocampus (related to memory and learning), which can be stimulated by intellectual activity and physical exercise.
Embryonic stem cells, found in the blastocyst, are 'fascinating' and 'controversial.' They are fascinating because they are pluripotent, capable of differentiating into all 220 specialized cell types of the body. They are controversial because their extraction requires the destruction of the blastocyst, which some consider a moral issue. However, many scientists view the blastocyst as a structural collection of cells without consciousness, justifying research for therapeutic applications.
Induced Pluripotent Stem Cells (iPSCs) are 'surrogate' stem cells, meaning they don't exist naturally. They are created in the lab by reprogramming adult cells (e.g., skin fibroblasts) back to an embryonic-like state by introducing specific genes. This technique, discovered by Shinya Yamanaka, allows scientists to obtain pluripotent cells similar to embryonic stem cells without the ethical controversies associated with blastocyst destruction.
Studying stem cells involves culturing them in the lab. Adult stem cells are difficult to expand while maintaining their tissue-specific identity. Embryonic stem cells, on the other hand, are easier to grow and expand. In Italy, deriving embryonic stem cells directly from blastocysts is illegal, but labs can work with cells supplied from other countries. The ultimate goal is to differentiate these expanded cells into specific cell types, such as neurons for studying neurological diseases like Huntington's chorea, by applying specific molecules and understanding developmental processes.
Stem cells offer a powerful tool for understanding how tissues form and how diseases develop. They can be used to model diseases in vitro and test the toxicity of drugs, especially for vulnerable populations like pregnant women. For instance, embryonic stem cells can mimic fetal development, allowing for the early detection of potentially harmful drug effects that could have been fatal for the fetus.
Despite ongoing research, clinical applications of stem cells are currently limited to three main areas. Firstly, bone marrow transplantation, using enriched adult stem cells, is a long-standing treatment for leukemias, regenerating healthy blood cells after chemotherapy. Secondly, stem cells are used to treat severe skin burns by growing new skin in the lab from a healthy patch of the patient's skin and grafting it. While life-saving, the regenerated skin may lack full functionality (e.g., sweat glands, hair). Thirdly, stem cells are successfully used to treat corneal burns, which cause blindness. By isolating and expanding limbal stem cells from the patient's eye, doctors can restore vision in many cases, demonstrating the potential for fully functional tissue regeneration when the stem cell's properties are thoroughly understood.