by James McIntosh, via MNT |
The discovery could lead to the development of new treatments for conditions such as alopecia.
In a new study, published in PLOS Biology, researchers from the Spanish National Cancer Research Centre (CNIO) outline a connection they discovered between macrophages – immune system cells that eat pathogens in a process called phagocytosis – and regenerative skinstem cells.
“We have discovered that macrophages, cells whose main function is traditionally attributed to fight infections and wound repair, are also involved in the activation of hair follicle stem cells in non-inflamed skin,” says study author Mirna Perez-Moreno.
Macrophages surround regenerative skin stem cells and activate them, in turn prompting the growth of hair. According to the authors, the discovery could have implications for the development of new technologies associated with regeneration, aging and cancer.
A surprise discovery
“The cyclic life of hair follicles consists of recurring phases of growth, decay and rest. Previous studies have identified signals that prompt a new phase of hair growth through the activation of resting hair follicle stem cells,” they write.
However, up until now, researchers have been unable to work out how different cells within the skin communicate with each other to prompt the growth of hair.
Perez-Moreno made an initial discovery while conducting a separate study on mice. She noticed that the mice she was working with for that project started to grow new hair after receiving anti-inflammatory drugs.
Believing that there could be a level of close communication between the immune cells and stem cells that would explain this finding, Perez-Moreno and her colleagues decided to test the various cells involved in the body’s immune system to see if any played a role in hair growth.
The researchers found that a fraction of skin-resident macrophages naturally died as part of the natural process apoptosis. To the team’s surprise, the combination of dying and surviving macrophages activated stem cells nearby, initiating hair growth.
Evidence of macrophages ‘going beyond their primary function’
When macrophages die during apoptosis, a class of signaling molecules called Wnts are released. The researchers found that administering a Wnt inhibitor drug to the macrophages delayed the growth of hair. This finding suggests that Wnts play a role in the activation of hair follicle stem cells.
Tiny droplets called liposomes were used by the team to carry the Wnt-inhibiting drug. This method of drug delivery to specific cells shows great promise, according to study author Donatello Castellana, and could be useful for future studies of different diseases.
“Our study underlines the importance of macrophages as modulators in skin regenerative processes, going beyond their primary function as phagocytic immune cells,” write the authors.
Although this particular study was conducted using mice, the researchers believe that their findings will translate over to humans and could help with the development of new methods of instigating hair growth, potentially treating conditions such as alopecia areata:
“This line of research should facilitate the development of novel therapeutic strategies for the manipulation of undesired human hair loss or growth that target perifollicular immunocytes, such as macrophages.”
“One of the current challenges in the stem cell field is to regulate the activation of endogenous stem cell pools in adult tissues – to promote regeneration without the need of transplantation,” says Perez-Moreno.
They may not have originally set out with the intention of making this discovery but, as a result, we now know that macrophages have a role to play within the biological environment surrounding skin stem cells.
Earlier in the year, Medical News Today reported on a study that found binge drinking reduces the levels of macrophages in the blood.