Investigating if it is possible to recover hair seems to be an exclusive task in the field of aesthetics, but it is not. The finding that now publishes a group of the National Center of Oncological Investigations (CNIO) reveals keys to grow the hair, but also brings new knowledge on a wider problem: how the tissues in the adult organism are regenerated, and especially the skin What they have discovered is an unexpected connection between the body’s defense system and the regeneration of the skin. As revealed by the authors in the work, published in PLOS Biology, cells of the immune system called macrophages -responsible for example of devouring possible pathogens- are also responsible for activating the growth of skin stem cells. These stem cells allow hair regeneration and also cause, when they fail, squamous cell cancer. Discovering that macrophages activate them can be relevant not only for therapies against hair loss, but also for oncological research.

The authors of the work are Mirna Pérez-Moreno and Donatello Castellana, from the Epithelial Cell Biology group of the BBVA-CNIO Foundation Program of Cellular Cancer Biology, in collaboration with Ralf Paus, from the universities of Manchester and Münster.

“We have discovered that macrophages, cells whose main function has been attributed to the defense of infections and repair of wounds, participate in the process of hair regeneration,” explains Pérez-Moreno. “We have even managed to induce hair growth. It is the first evidence we have of the role of macrophages in the cyclical hair growth”.

Preliminary evidence

The researchers did not investigate why the relationship between macrophages and hair. The work, begun more than four years ago, is based on an observation by Pérez-Moreno while analyzing another problem. The mice with whom I worked then were treated with anti-inflammatory drugs, which had as an unexpected side effect the reactivation of hair growth.

Convinced that the explanation must be in the immune system – inflammation is a defensive response of the organism – Pérez-Moreno began experimenting with the different types of cells responsible for the defense of the organism.

They then detected a curious phenomenon: in a specific phase of the cyclic growth -normal- of the hair, a part of the macrophages dies -by the process of self-induced cell death known as apoptosis-, and that is when the hair begins to grow again. That is, the death of a part of the macrophages seems to be the signal that pushes the hair follicle to enter the next stage of the cycle.

The researchers also revealed how the signal is transmitted by macrophages. Perez-Moreno explains: “The death of a part of macrophages stimulates those who remain alive to secrete factors that activate the skin’s stem cells, and thus promote hair growth.”

Reproduce the natural process

Among these factors that secrete macrophages are proteins called Wnt. The confirmation that macrophages are responsible for the production of these proteins is another of the novel aspects of the work.

The researchers demonstrated all of the above by artificially reproducing the natural process. For this they used a Wnt inhibitor drug, and in doing so delayed, as expected, hair growth.

Although this work has been done entirely in mice, the researchers believe that their finding “should facilitate the development of new therapeutic strategies” for the treatment of hair growth in humans.

The possibility of attacking one type of cell to affect another may have wider applications than the “only” hair growth. In addition, the use of liposomes as a vehicle for drugs to specific cell types is a very promising experimental pathway in several pathologies, says Donatello Castellana.

They also consider the implications for cancer research important: “Skin stem cells have been identified as the cells that give rise to squamous cell cancer, one of the most frequent tumors in the world,” says Pérez-Moreno. “Our work has identified that macrophages contribute to regulate the controlled proliferation of stem cells through the Wnt pathway; Maybe there are tumors related to a mismatch in the macrophages that secrete Wnt. “

From a more basic perspective, the result is framed in the effort to understand how adult tissues regenerate, especially the skin. And here the important thing is the new great role played by macrophages.

“The skin is made up of different structures, among them the follicles, which form the hair and regenerate throughout our lives thanks to the presence of stem cells”, explain the researches.