When we created a small wound in the skin, matrix-producing neutrophils would rapidly accumulate around the lesion to build matrix "rings" that protected from small molecules or microbes… magical images from the hands of the master of microscopy Uderhardt and @alazozcan.bsky.social

We propose that what is unique to neutrophils is their capacity to dynamically reinforce the matrix: the skin becomes stiffer at night-time, when neutrophils enter the tissue! An experiment from the mind and hands of @TVicanolo !

To demonstrate this, we generated a reporter mouse in which collagens produced by neutrophils (or fibroblasts, for comparison) are labeled with mCherry. Amazing craft by @alazozcan.bsky.social to set this up...

But how do neutrophil mediate this unexpected property of the skin? Although questions remain, we find that they are uniquely specialized in depositing matrix components, such as Collagen 3, in specific areas of the skin where large matrix fibers provide mechanical reinforcement to the skin

An exciting finding was that neutropenic mice, or mice lacking TGF signaling in neutrophils, both have major alterations in the skin: matrix structure, composition and skin mechanics are dramatically altered, resulting in a more permeable skin

We report that neutrophils from the skin (and other epithelial barriers) are unique. They produce matrix components, including collagens and enzymes that remodel the matrix. This program, induced through TGFb signaling, is shared by mice and humans.