This story is part 7 of an occasional series on the current progression in Regenerative Medicine. In 1999, I defined regenerative medicine as the collection of interventions that restore to normal function tissues and organs that have been damaged by disease, injured by trauma, or worn by time. I include a full spectrum of chemical, gene, and protein-based medicines, cell-based therapies, and biomechanical interventions that achieve that goal.

If your hair has been thinning or falling out altogether, it may be time to blame Covid-19. As the pandemic wears on, it has become clear that the effects of Covid-19 are not limited to respiratory health but can negatively impact anything from mental health to hearing and balance. Hair seems to be yet another one of its casualties.

Just in the past year, Google searches for hair loss have increased by eight percent. Social media groups dedicated to the discussion of hair loss have reported huge spikes in subscribers during the pandemic. Parallel to online trends, many dermatologists have described an influx of patients with hair loss or hair thinning.

So, why is this happening, and is it temporary? The good news is that hair loss caused by the pandemic is probably temporary. Hair loss can occur due to a myriad of reasons including genetics, aging, changes in hormones, changes in diets, or damaging hairstyles. However, the surplus of hair loss that occurred across the nation during the pandemic was likely induced by the physical shock of contracting Covid or the emotional shock of living through the pandemic. This process is triggered by a condition called telogen effluvium.

Telogen effluvium materializes when the brain or body is under stress, causing hair follicles to stop growing prematurely. As we typically lose 50 to 100 hairs a day, without the addition of new hair growth this can cause balding or thinning of hair over time. This is a temporary condition. Once the body returns to rest, hair growth can return to normal.

However, while telogen effluvium may explain the temporary hair loss that has been experienced by the masses in the past few years, the great hair loss event of the pandemic begs the question of why we lose our hair in the first place?

A study run by Professor Rui Yi at Northwestern University shows significant progress in discovering the answer to that age-old question; perhaps, finally providing a window of treatment for the large portion of the population that is experiencing hair loss.

Previously, the accepted hypothesis about the cause of permanent hair loss was that hair loss was induced by the death of stem cells. Stem cells are known for their ability to grow into any type of cell or tissue in the body, including hair. Scientists hypothesized that as we age, the stem cells responsible for growing hair follicles were eventually exhausted and would die in place.

However, Dr. Yi’s study demonstrates that this process may not be the case. Dr. Yi et al. approached their experiment by studying hair follicles inside of live tissues. He and his colleagues used lasers that penetrate deep into tissue and can produce a real-time microscopic image of that tissue. After using their laser approach to observe the hair follicles inside the ears of anesthetized mice, Dr. Yi made a surprising discovery.

Instead of the stem cells dying inside their hair follicles, researchers observed that when animals started to grow old, their stem cells actually altered their shape to squeeze out of tiny holes in the hair follicle, darting away after their escape. Much like employees who walk off the job in unfair working conditions, as hair follicles age and wear out, it seems as though stem cells abandon their hair growth profession.

After discovering this mechanism of hair loss, Dr. Yi and colleagues isolated two genes called FOXC1 and NFATC1 that seemed to be less active in older hair follicle cells and may be responsible for inducing the stem cells’ escape.

Overall, hair loss is a truly fascinating topic whose causes seem to range from pandemics to tiny stem cells escaping their role in hair growth. As the nation’s scalps recover from the events of the past two years, the next step in hair loss research will be to confirm this mechanism of hair loss, determine where exactly stem cells escape to, and how we can develop treatments that prevent or prolong the escape of stem cells to limit overall hair loss.