Hair Birth in Four Dimensions: Scientists Create a Unique Map of Follicle Development

Scientists at Johns Hopkins University School of Medicine have developed a technology that can reconstruct the formation of hundreds of hair follicles in three dimensions and then add a fourth dimension—time. The result is a molecular “stop-motion animation” showing how the organ develops.

The findings were published in the scientific journal Cell. The study was funded by the U.S. National Institutes of Health (NIH).

Hair follicles are the smallest and most numerous organs in the human body, yet they develop according to the same fundamental principles as other organs. The new technology could therefore help researchers understand how disruptions in developmental processes contribute to congenital disorders and other diseases.

To create the four-dimensional map, the researchers developed a method called 3D DNase-Enhanced Expression Profiling (3DEEP). The technique makes it possible to examine relatively large sections of tissue while simultaneously determining the locations of millions of RNA molecules associated with gene activity.

The researchers then identified different cell types, estimated the molecular “age” of each follicle and arranged them from the youngest to the most mature. This allowed individual three-dimensional snapshots to be transformed into a continuous picture of organ development over time.

The team identified several key stages in the process. First, precursor cells organize themselves spatially and establish the axis of the future follicle. They then differentiate into various specialized cell types. During the final stage, these cells grow and reorganize, forming a mature follicle capable of producing hair.

The scientists also compared normal mice with animals lacking Foxn1, a gene essential for hair growth. They found that follicle development was delayed in the hairless mice. Although their cells could divide even more actively than those in normal animals, they were less capable of maturing and acquiring the necessary functions at the appropriate time.

According to the researchers, the Foxn1 mutation disrupts communication between cells and the timing of their development. As a result, the developing hair follicle breaks down before it can begin producing hair.

The authors believe the new method could eventually be used not only to investigate the mechanisms behind hair loss, but also to study the development of other organs, congenital disorders and even the processes involved in tumor formation.

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