Researchers from Harvard University have discovered that when hair follicles die during a stressful event, the body's immune system becomes primed to attack more hair follicles during similar future events.
It is well known that stress affects health, including immune system function. However, the precise ways in which a single stressful experience can damage different tissues are still not fully understood. In particular, it remains unclear whether an acute stress attack can leave lasting effects.
Previous research has indicated that stress can have both immediate and long-term effects on hair follicles. Now, scientists say that stress in mice can trigger hair loss and rapidly stimulate immune T cells to cause recurrent hair loss in the future.
The researchers explain that severe acute stress leads to hyperactivity of the sympathetic nervous system in mice, which is responsible for increasing heart rate and muscle strength in response to the "fight or flight" response. This, in turn, activates CD8+ T cells in the mice, which are capable of attacking hair follicles.
The researchers emphasize that even after the initial stress subsides, these T cells can trigger recurrent hair loss when inflammation occurs later.
The researchers wrote in the study published in the journal Cell: “Our results show that a single acute stress attack causes immediate damage, and when it does so, it activates and expands rare autoreactive CD8+ T cells, preparing the tissue for a future immune attack. Thus, a single acute stress attack can cause immediate damage, and when it does so, it makes the same tissue vulnerable to future damage.”
Scientists suspect that this type of immune response may be a way for the body to sacrifice replaceable, metabolically expensive cells in order to preserve essential stem cells. They say that by sacrificing some hair follicles when threatened, the mice's bodies may preserve the stem cells that regenerate tissue once the threat has passed.
This could represent a "strategic solution for conserving limited resources for critical stress responses".
The researchers conclude: "In short, our study reveals how stress leads to acute tissue damage over time. These mechanisms may help explain the onset of alopecia and its frequent association with stress."
Scientists say the findings could also help in better understanding conditions such as multiple sclerosis, type 1 diabetes and lupus, where the causes remain complex.
Researchers hope that further research into stress-induced hair loss in human tissue will help to better uncover the complex causes behind these conditions.
