Alopecia is an autoimmune disease that causes irreversible hair loss on the scalp and body, affecting nearly 2% of the global population at some point in their lives.
A team of researchers from Australia, Singapore, and China has discovered that activated hair follicle stem cells (HFSCs)—essential for hair growth and repair—depend on a powerful protective protein called MCL-1 to function properly. Without MCL-1, these cells become stressed and eventually die, leading to hair loss, the scientists report in Nature Communications.
Hair follicles are small, tunnel-like structures in the skin where hair grows. They cycle through three distinct phases: anagen, the active growth phase; catagen, a transitional phase marked by slowed growth and follicle shrinkage; and telogen, the resting phase, during which growth stops and hair falls out. The cycle then begins again, regulated by HFSCs.
Research shows that when HFSCs are stressed by hair loss or follicle shrinkage, they may undergo apoptosis—a form of controlled cell death—contributing to further hair loss.
This apoptotic process is regulated by the BCL-2 protein family, which determines whether a cell survives or dies. While MCL-1, a member of this family, is known as a pro-survival protein, its role in HFSC regulation and hair regeneration remains unclear. To investigate MCL-1’s effect on HFSC regulation, the researchers deleted the MCL-1 gene from mouse skin cells and removed some existing hair.
They found that MCL-1 deficiency from birth does not affect hair follicle formation but gradually leads to hair loss due to a decline in HFSC levels over time.
