Stemness refers to a fundamental property found in certain cells, distinguishing them by their unique capabilities rather than defining a specific cell type. It describes the characteristics that allow a cell to both perpetuate itself and generate specialized cells within an organism.
What is Stemness?
Stemness is defined by two core properties: self-renewal and potency. Self-renewal is the ability of a cell to divide multiple times while remaining in an undifferentiated state, essentially making more copies of itself without specializing. This process ensures a continuous supply of cells with stem-like properties.
Potency describes a cell’s capacity to differentiate into various specialized cell types. This spectrum of differentiation potential can range from very broad to quite narrow. Totipotent cells, like the zygote formed after fertilization, have the highest potency and can give rise to all cell types of an organism, including extraembryonic tissues like the placenta. Pluripotent cells can differentiate into all cell types of the adult body but not extraembryonic tissues. Multipotent cells have a more limited differentiation potential, giving rise to several cell types within a specific lineage or tissue, such as blood cells or nerve cells.
Where is Stemness Found?
Stemness is observed in different categories of cells. Embryonic stem cells (ESCs) are derived from the inner cell mass of an early-stage embryo, specifically the blastocyst. These cells exhibit high pluripotency, meaning they can develop into any cell type of the adult body.
Adult, or tissue-specific, stem cells are found in various tissues throughout the body, including bone marrow, skin, and the brain. These cells have multipotent capabilities, restricted to differentiating into cell types relevant to their resident tissue, such as hematopoietic stem cells forming various blood cells. They play a significant role in tissue repair, maintenance, and regeneration throughout an individual’s life. Induced pluripotent stem cells (iPSCs) are adult cells that have been genetically reprogrammed in a laboratory to revert to an embryonic-like, pluripotent state. This technology allows scientists to create stem cells from a patient’s own cells, offering new avenues for research and potential therapeutic applications.
Why is Stemness Important?
Understanding stemness is important for comprehending fundamental biological processes, from development to disease. In development, stem cells drive the formation of an entire organism from a single fertilized egg, orchestrating the complex differentiation into diverse tissues and organs. Throughout life, stem cells are continuously active in tissue repair and regeneration, replacing damaged or aged cells to maintain organ function. For instance, hematopoietic stem cells constantly replenish blood cells, and skin stem cells renew the outer layer of skin.
The implications of stemness extend into medical applications and research. In regenerative medicine, the ability of stem cells to differentiate into specific cell types offers the potential to grow new tissues or even organs for transplantation, addressing conditions like heart failure or spinal cord injuries. Stem cells also serve as tools for disease modeling, allowing researchers to create “diseases in a dish” to study disease progression and test new drugs. The concept of stemness is also relevant in certain diseases, such as cancer. Cancer stem cells, a subpopulation within tumors, exhibit stem-like properties, including self-renewal and differentiation into various tumor cells, which can contribute to tumor growth, resistance to therapies, and recurrence.