There is still no cure for alopecia or excessive hair loss despite several breakthroughs in the treatment and management of more dreaded diseases. However, cancer researchers may have finally found an exciting new way to trigger hair growth that involves tapping the immune system.
A study conducted by researchers Mirna Perez-Moreno, Donatello Castellana, and Ralph Paus, and published in the journal PLOS Biology has identified a close link between macrophages and the activation of hair follicle stem cells.
Macrophages are a type of white blood cells in the immune system responsible for phagocytosis—a process that involves engulfing and digesting a number of harmful substances in the body including bacteria and viruses, cancer cells, other foreign substances, and cellular debris.
The aforementioned study is a derivative of an earlier mouse study conducted by Perez-Moreno. Accordingly, the mice under her care started to grow hair after receiving anti-inflammatory drugs. Perez-Moreno took off from this unexpected finding to refocus her attention toward the possible connection between the immune system and hair growth.
Together with colleagues, the new study required experimenting with different types of cells in the immune system to pinpoint a particular cell that may have played a role in triggering hair follicle activities.
The team subsequently found out that some macrophages in the skin died due to a process known as apoptosis. Surprisingly, the presence of dying and living macrophages stimulated the secretion of factors that activated nearby stem cells and thus, initiated hair growth.
The phenomenon further directed the attention of the researchers toward a class of signalling molecules called Wnts. Note that when macrophages die during apoptosis, these Wnts are released. The researchers replicated this natural process by treating macrophages with a Wnt inhibitor drug encapsulated in liposomes. As expected, the inhibition caused delay in hair growth
There are several implications from this finding. First, although the study involved mice, it can lead to the development of novel strategies for treating hair loss in humans according to the researchers.
“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 Perez-Moreno.
Furthermore, as reiterated by Castellana, apart from treating hair loss, the use of liposomes to encapsulate drugs for cellular introduction can have broader applications in experiments concerning the field of pathology.
The study also opens newer promises for studying macrophages. Perez-Moreno explains: “Macrophages are a very diverse cell population. It was only less that ten years ago that scientists discovered that besides from the bone marrow, macrophages originate from the yolk sac during pregnancy, and there are even other macrophages that proliferate within tissues. The diversity of the sources from which skin resident macrophages originate is not fully understood.”
In addition, the authors said, “Our study underlines the importance of macrophages as modulators in skin regenerative processes, going beyond their primary function as phagocytes [or immune system cells].”
Perez-Moreno and Castellana are from the Epithelial Cell Biology Group of the BBVA Foundation-CNIO Cancer Cell Biology Programme. Paus is an immunobiology expert from the University of Manchester and Münster.