Cells become stem cells through both natural developmental processes and advanced laboratory techniques.
During natural development, particularly in the very early stages of an embryo, specialized stem cells emerge. As an example, by about five or six days after fertilization, the embryo develops into a blastocyst. This structure contains a clump of cells inside, known as the inner cell mass, which are human embryonic stem cells. As noted in research, these cells can be extracted from the blastocyst and grown in a laboratory culture. The very first embryonic stem cells that form are considered totipotent, meaning they can give rise to all embryonic and extra-embryonic cell types. Later, these become pluripotent, able to form any cell type of the body.
Natural Formation of Stem Cells
- Embryonic Development: Stem cells are foundational during embryonic growth, giving rise to all tissues and organs. The inner cell mass of the blastocyst is a key source of these pluripotent stem cells.
- Adult Tissues: Even in mature organisms, small populations of tissue-specific or adult stem cells reside in various tissues like bone marrow, skin, and the gut. These multipotent stem cells are less versatile than embryonic stem cells but are crucial for repair and regeneration within their specific tissue type.
Creating Stem Cells in the Laboratory
Beyond natural development, scientists can create stem cells artificially:
- Extraction from Blastocyst: As mentioned earlier, embryonic stem cells can be extracted from the blastocyst and grown in a laboratory culture for research and potential therapeutic use.
- Induced Pluripotent Stem Cells (iPSCs): A revolutionary technique involves reprogramming mature, specialized cells (like skin cells) back into a stem cell-like state. This process uses specific genetic factors to turn back the cellular clock, resulting in iPSCs that behave much like embryonic stem cells.
Why is this important?
- Understanding Development: Studying how stem cells form naturally helps us understand the complex process of embryonic development.
- Regenerative Medicine: Creating stem cells in the lab offers potential for generating tissues and organs to replace those damaged by disease or injury.
- Disease Modeling: Stem cells can be differentiated into specific cell types affected by diseases, providing models for studying the illness and testing new drugs.
In summary, cells become stem cells either through the inherent processes of early embryonic development, where they are initially totipotent and then pluripotent, or through laboratory methods like extracting embryonic stem cells or reprogramming mature cells into iPSCs.
