Hair loss and hair shedding are very common in times of stress and can affect anyone—even those who have no family history of either condition. Apart from genetics, other factors, such as medication, stress, birth control, or lack of sleep can kill the stem cells inside hair follicles.
Stem cells have the potential to differentiate into a variety of subtypes, including hair-follicle stem cells, which are responsible for the formation and growth of hair. Unfortunately, hair follicles are similar to eggs in female mammals: Individuals are born with a finite amount and the number only keeps decreasing. Therefore, the production of new hair follicles in labs is of huge import to those who suffer from hair loss.
Biologist Ernesto Lujan launched the start-up dNovo in 2018 in an attempt to genetically reprogram blood, skin, or fat cells into hair-forming cells to treat hair loss. The process of reverting mature, specialized cells into induced pluripotent stem cells, called “reprogramming,” is slowly emerging across the globe as a way to treat patients. dNovo is currently testing the technology on mice and pigs.
The process consists of collecting cell samples from a patient, reprogramming them into hair-follicle stem cells, growing these genetically manipulated cells in the lab, and adding them to the scalp of the patient, who should see hair growth one to three months after the procedure.
Even though the procedure may seem simple, hair follicles are complicated organs and their formation is not yet fully understood. Tamara Ouspenskaia (BSc ’09, MSc ’10), who completed her PhD on the mechanisms involved in the specification of stem cells during mouse development in 2016, was part of the Fuchs lab that succeeded in growing hair on a nude mouse. The lab purified hair stem cells and injected them into the skin of the mouse, and the experiment succeeded, in part, because it chose nude mice as its subjects.
“[Nude mice] lack an immune system and thus don’t reject the injection as they can’t recognize the stem cells as foreign,” Ouspenskaia said.
The scientists then used lentiviruses to inject the reprogrammed cells into the amniotic cavity of mice. Since mice are only embryos at this stage, the reprogrammed cells will pass down their hair-growing abilities to all their descendant cells. Another way to grow a hair shaft and transplant it onto nude mice is by growing organoids—3D structures made from pluripotent stem cells.
“If conditions of growth are right, [organoids] will try to replicate the tissue normally present in the body,” Ouspenskaia said.
There are different ways to grow hair stem cells in labs, but the more complex part is ensuring that the patient’s immune system does not reject the new cells. One solution is to take functional hair follicles from other parts of the body and to transplant them onto the scalp—but this raises questions about the best regions to take the hair from.
Apart from growing the hair shaft of nude mice, the Fuchs lab showed how a mouse embryo grows hair. From day zero to 10, the embryo is surrounded by identical cells which then become clusters of cells expressing markers of future hair follicles that eventually stop dividing.
Stem cells at this stage of a mouse are called embryonic stem cells and present unique properties, as opposed to adult stem cells.
“Something special about embryonic hair-follicle stem cell[s] is that they can regrow hair follicles, [whereas] adult hair-follicle stem cell[s] can’t,” Ouspenkaia said. “If we could understand more differences between embryonic and adult hair-follicle stem cell[s], maybe we could reprogram them to grow hair again.”