Neurons, the fundamental units of the brain, have a remarkably long lifespan, surviving for the entire lifetime of an organism in the absence of disease. Their survival is intricately linked to both internal and external factors.
Intrinsic and Extrinsic Factors in Neuronal Survival
While initially believed to be primarily determined by external factors (extrinsic), research reveals a significant role for intrinsic mechanisms as well.
Intrinsic Factors: Genetic Programming for Longevity
- Genetic Programming: Neurons are genetically programmed for longevity. A mechanism triggered at birth intrinsically reduces a general form of cell death, ensuring their long-term survival. [^1, ^7, ^9] This inherent programming contributes to their remarkable lifespan, exceeding that of many other cells in the body. [^6]
- Lack of Replicative Aging: Unlike many cells, neurons do not undergo replicative aging. In healthy conditions, their lifespan is only limited by the lifespan of the organism itself. [^3]
Extrinsic Factors: Environmental Influence
- Target Cell Interaction: Developing neurons need to connect with their target cells, which provide crucial survival signals. This interaction is essential for their survival and proper functioning. [^5]
- Tissue and Cell Support: The surrounding tissues and cells provide critical support for neuronal survival. Their influence on neuronal life is substantial. [^1]
- Microglia's Role: Microglia, specialized immune cells in the brain, play a role in removing dead or dying neurons through phagocytosis. However, recent research is exploring their involvement in the survival of live neurons as well. [^8]
Neuronal Lifespan and Malleability
Adult neurons can survive for a lifetime and retain their capacity for change (malleability) for many years, especially during childhood. This malleability is why children are exceptionally adept at learning new languages. [^2]
Potential for Extended Lifespan
Some studies suggest that neurons might even outlive the organism they reside in. If placed in a suitable environment outside of the body, they could potentially survive indefinitely. [^4]
However, it is crucial to note that large numbers of neurons die during development (migration and differentiation). [^2] Neurodegenerative diseases such as Alzheimer's further impact neuronal survival. [^7]
[^1]: Researchers have generally believed that their survival is determined nearly extrinsically, or by outside forces, such as the tissues and cells that neurons supply with nerve cells.
[^2]: Adult neurons survive for a lifetime and remain malleable for several years. This is one reason kids are especially adept at learning new languages.
[^3]: Neurons in mammals do not undergo replicative aging, and, in absence of pathologic conditions, their lifespan is limited only by the maximum…
[^4]: “Neurons do not have a fixed lifespan,” says Magrassi. “They may survive forever. It's the body that contains them that die. If you put them in…
[^5]: In order to survive, developing neurons must reach and innervate their appropriate target cells, which supply critical survival promoting…
[^6]: Unlike many cells in the body, which are relatively short-lived, neurons have evolved to survive a long time, and some keep working…
[^7]: Researchers reveal a mechanism by which long-term survival of neurons is intrinsically programmed during development.
[^8]: Microglia are known to remove dead and dying neurons in the brain by phagocytosis.
[^9]: The study, published in the journal Neuron, identifies a mechanism the researchers say is triggered at neuron birth to intrinsically decrease a general form of…
