A study by researchers at the University of Southern California (USC) has identified a novel 'dermal clock' signalling that coordinates stem cell activity and regulates hair regeneration in animal models.
The study led by Cheng-Ming Chuong, M.D., Ph.D., principal investigator and professor of pathology at the Keck School of Medicine of USC, also indicated that this signalling switch involves bone morphogenetic protein (Bmp) pathway.
"Conceptually, the findings have important implications for stem cell research and in understanding how stem cell activity is regulated during regeneration. The research presents a new dimension for the regulation of hair re-growth and ultimately organ regeneration," said Chuong.
He said that hair being one of the few organs to regenerate regularly makes it an important model for organ regeneration in mammals. Also, owing to recent work in the field, hair cycling has been proved to be one of the mainstream models for organ regeneration. However, he indicated that most of these works focus on the cyclic regeneration of one single hair follicle.
"Each of us has thousands of hair follicles. In our study, we were motivated to analyze the coordinative behavior of cyclic regeneration in a population of organs," said Chuong.
It was found that hairs, even in normal mice, regenerate in waves, rather than individually. Thus the researchers indicated that hair stem cells are not just regulated by the micro-environment within one hair follicle, as has previously been thought. They were also regulated by adjacent hair follicles, other skin compartments and systemic hormones, in a hierarchical order.
The researchers found that at the molecular level, periodic expression of Bmp in the skin macro-environment was apparently at the center of the mechanism for coordinated hair stem cell activation.
During the regeneration of many cells, they must communicate activation signals among themselves. So, the macro-environment can be either permissive or suppressive for stem cell activation at different time points.
"Our research shows that the formation of new tissues or organs from stem cells -- such as the formation of new hairs -- can be more robust if it occurs in a permissive macro-environment. I hope that our research will draw more attention to the hair follicle as the model for physiological regeneration in mammals, and as an abundant source of adult stem cells for the purposes of stem cell therapy," said Maksim Plikus, Ph.D., a post-doctoral fellow and the first author of the study.
This study will be published in the next issue of the journal Nature.