Stem cells are human cells capable of developing into many different cell types, such as muscle, blood, or brain cells. They can also repair damaged tissues within the body. Their potential in medical research is significant and widely recognized. Studying these cells may offer insights into how conditions like birth defects and cancer arise.
Core Capabilities of Stem Cells
Stem cells have unique biological properties. One property is self-renewal, meaning they can divide and produce more stem cells over a long period, maintaining an undifferentiated state. This continuous replication ensures a sustained supply of these versatile cells.
Another capability is differentiation, their capacity to develop into specialized cell types. For example, stem cells can become nerve, muscle, or blood cells, each performing specific functions. The extent of a stem cell’s differentiation potential is referred to as its potency. Pluripotent stem cells, like embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), can give rise to all cell types of the body. In contrast, multipotent stem cells, such as adult stem cells, are generally limited to differentiating into cell types found within a specific tissue or organ, like hematopoietic stem cells forming various blood cells.
Repairing and Regenerating Tissues
Stem cells are used in therapeutic applications to replace or repair damaged or diseased tissues and organs. A well-established application is treating blood disorders through bone marrow transplants. Here, hematopoietic stem cells replace cells damaged by chemotherapy or disease, regenerating the blood and immune system. This approach is used for conditions like leukemia, lymphoma, and aplastic anemia.
Stem cells are also investigated for their potential to repair damaged heart muscle following a heart attack. Studies have explored using bone marrow-derived stem cells and iPSCs to improve cardiac function and reduce scar tissue in animal models and early clinical trials. Researchers are exploring stem cells for neurodegenerative diseases, such as Parkinson’s disease and spinal cord injuries, aiming to replace damaged neurons and promote neural regeneration. For type 1 diabetes, stem cell therapy seeks to replace insulin-producing beta cells. Tissue engineering also utilizes stem cells to create new tissues or organs in the laboratory, holding promise for future regenerative medicine.
Understanding Disease and Developing Treatments
Stem cells are used for understanding diseases and developing new treatments. They create “disease in a dish” models, allowing researchers to study how diseases develop and progress in a controlled environment. For instance, patient-specific iPSC-derived neurons can model conditions like Alzheimer’s and Parkinson’s disease, providing insights into disease mechanisms.
This modeling capability extends to drug discovery and testing. Stem cell-derived tissues, such as liver or heart cells, can screen new drugs for effectiveness and potential toxicity, potentially reducing the need for animal testing and improving drug safety profiles. Patient-specific iPSCs can also be used in personalized medicine to test therapies tailored to an individual’s unique genetic makeup, allowing for more precise treatment.
Sources of Stem Cells for Medical Use
Stem cells used in medical research and therapy originate from several sources, each with distinct characteristics. Embryonic stem cells (ESCs) are derived from the inner cell mass of a 3- to 5-day-old embryo, known as a blastocyst. These cells are pluripotent, meaning they can differentiate into any cell type in the body.
Adult stem cells are found in various mature tissues, such as bone marrow, fat, and umbilical cord blood. They are generally multipotent, meaning their differentiation potential is limited to the cell types found within their tissue of origin. For example, hematopoietic stem cells from bone marrow primarily produce blood cells. Induced pluripotent stem cells (iPSCs) are adult cells, like skin or blood cells, that have been genetically reprogrammed in a laboratory to revert to an embryonic-like pluripotent state. This reprogramming allows them to differentiate into almost any cell type, making them a promising source for personalized medicine as they can be derived from the patient themselves, potentially reducing immune rejection.