Interleukin (IL)-17 may plays a central role in skin aging, according to research from Institute for Research in Biomedicine (IRB Barcelona) in collaboration with the National Center for Genomic Analysis (CNAG).

The study, which was led by Dr. Guiomar Solanas, Dr. Salvador Aznar Benitah, both at IRB Barcelona, and Dr. Holger Heyn, at CNAG, describes the changes undergone by different types of cells with aging and identifies how some immune cells in the skin express high levels of IL-17.

“Our results show that IL-17 is involved in various functions related to aging. We have observed that blocking the function of this protein slows down the appearance of various deficiencies associated with aging skin. This discovery opens up new possibilities for treating some of the symptoms or facilitating skin recovery after surgery, for example,” explains Dr. Benitah, ICREA researcher and head of the Stem Cells and Cancer laboratory at IRB Barcelona, in a news release.

“Single cell sequencing has allowed us to dive deep into the complexity of cell types and states forming the skin and how these change during lifespan. We did not only find differences in the composition of aged skin, but also changes in cell activity states. Particularly immune cells showed specific age-related profiles, which we could pinpoint by analyzing thousands of individual cells on at a time,” says Dr. Holger Heyn, head of the Single Cell Genomics laboratory at CNAG.

The study describes how, during aging, the presence of immune cells, namely gamma delta T cells, innate lymphoid cells, and CD4+ T cells, significantly increases in the skin. These same cells also start expressing very high levels of the pro-inflammatory cytokine IL-17.

"Aging is associated with mild but persistent inflammation and, in the skin, this is characterized by a significant increase in IL-17, which causes skin deterioration," explains Dr. Paloma Solá, first author of the paper, together with Dr. Elisabetta Mereu, who is now a researcher at the Josep Carreras Leukemia Research Institute.

Reversing the symptoms of aging in skin

Previous studies had described that IL-17 is related to some autoimmune skin diseases, such as psoriasis, and there are existing treatments that block this protein. The team of researchers studied the response of various aspects to blocking IL-17 activity, including hair follicle growth, transepidermal water loss, wound healing, and genetic markers of ageing. These four parameters showed an improvement after treatment, as the acquisition of these ageing traits was significantly delayed.

“IL-17 protein is essential for vital body functions, such as defense against microbes and wound healing, so permanently blocking it would not be an option. What we have observed is that its temporary inhibition offers benefits that could be of interest at a therapeutic level,” says Dr. Solanas, associate researcher at IRB Barcelona.

Future work by the researchers will focus on clarifying the ageing processes that are related to inflammatory states in the skin and how these are linked to IL-17. The team will also address whether IL-17 is involved in the ageing and deterioration of other tissues and organs.

PHOTO CAPTION: Immunofluorescence staining of IL-17(white) in aged mouse skin

PHOTO CREDIT: IRB Barcelona