New research describes some of the factors that determine when hair grows, when it stops growing, and when it falls out.
The researchers report their findings in three papers focusing on stem cells located in hair follicles (hfSCs), which can regenerate hair follicles as well as skin.
These hfSCs are governed by the signaling pathways BMP and Wnt—which are groups of molecules that work together to control cell functions, including the cycles of hair growth.
The most recent paper, published in the journal Stem Cells, focuses on how the gene Wnt7b activates hair growth. Without Wnt7b, hair is much shorter.
Researchers in the University of Southern California lab of Krysztof Kobielak first proposed Wnt7b’s role in a January PNAS publication. The paper identified a complex network of genes—including the Wnt and BMP signaling pathways—controlling the cycles of hair growth.
Reduced BMP signaling and increased Wnt signaling activate hair growth. The inverse—increased BMP signaling and decreased Wnt signaling—keeps the hfSCs in a resting state.
A third paper published in Stem Cells in September further clarified the workings of the BMP signaling pathway by examining the function of two key proteins, called Smad1 and Smad5. These proteins transmit the signals necessary for regulating hair stem cells during new growth.
“Collectively, these new discoveries advance basic science and, more importantly, might translate into novel therapeutics for various human diseases,” says Kobielak.
“Since BMP signaling has a key regulatory role in maintaining the stability of different types of adult stem cell populations, the implication for future therapies might be potentially much broader than baldness—and could include skin regeneration for burn patients and skin cancer.”
Funding for all three studies came from the Donald E. and Delia B. Baxter Foundation Award and National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health. Eve Kandyba, the first author for all three papers, was a fellow of the California Institute for Regenerative Medicine (CIRM)–Research Training Program II in Stem Cell Biology.