It has been revealed how skin "chooses" the locations for hair growth

The arrangement of future hairs on the skin may arise through cell movement in response to chemical signals. Scientists at the University of Geneva have shown that such a mechanism can reproduce different patterns of hair primordia in two rodent species. The study was published in the journal Proceedings of the National Academy of Sciences.

Even before birth, placodes appear on the embryo's skin — small areas from which hair follicles subsequently develop. In laboratory mice, new primordia emerge in sequential waves between already existing ones.

The traditional explanation attributes this to skin growth and the inhibition of new primordia formation near existing ones. However, this framework poorly explains some of the more ordered patterns found in other animals.

The authors considered chemotaxis — the directed movement of cells along a chemical gradient. In the mathematical model, motile dermal cells interacted with an attracting signal from the epidermis on a growing area of skin.

This mechanism reproduced the pattern of sequential primordia emergence in the common house mouse. The researchers then tested the model on the spiny mouse Acomys dimidiatus, in which hair primordia form a particularly regular pattern with a pronounced directionality.

To obtain the second arrangement pattern, it was sufficient to account for differences in the directionality of interactions and skin growth, consistent with experimental data. A completely separate mechanism for each species was not required.

According to the scientists, the result demonstrates how local cell behavior can generate complex tissue structure.