Hair follicle formation, growth and regeneration: stem cell and progenitor activation by dermal papilla (DP) cells and their embryonic precursors.

Cell communication between tissue stem cells (SCs) and their cellular microenvironment within so-called SC niches is critical for SC self-renewal, differentiation and thus overall tissue homeostasis. It is also critical for new growth and repair during regeneration. How specialized niche cells acquire their inductive properties remains largely unknown. The focus of the lab is to understand the general molecular mechanisms of niche cell fate specification and function that is required for SC activation during tissue formation, gorwth and regeneration.

The hair follicle (HF) is an excellent model system for studying the molecular cross-talk between stem/progenitor cells and the niche. During embryonic HF formation epidermal progenitors in hair placodes receive niche signals from dermal condensates (DC), precursors of the mature HF mesenchyme, i.e. the dermal papilla (DP). DP cells then act as niche for hair bulb progenitors to coordinate continuous hair growth and for stem cells in the adult HF bulge/germ to launch a new hair cycle. Importantly, isolated mature DP cells can induce new HF formation after cell transplantation into skin of recipient immunocompromised mice.

The lab is interested in two key questions:

1. What are the DC/DP signals?

2. What controls DC/DP cell fate?

Our immediate goal is to answer these fundamental questions by building upon our new extensive genome-wide knowledge of their molecular repertoire and applying our recently established genetic DP niche labeling and gene targeting strategies for exploring the role of DP signature genes during HF formation, growth and regeneration. Our long-term goal is to use the hair follicle as model system to understand how niche cells govern stem cell functions and provide a rational basis for developing future hair regenerative therapies.

For more detailed information on our approach, recent discoveries and next frontiers see the recent lecture at the 75th Annual Meeting of the Society of Investigative Dermatology: