Here is a collection of studies on hair follicle cycles and regeneration mechanisms. Specific attention in the links is on the “Bulge” and stem cells contained in it. Studies observed that Epithelial Stem Cells in the Bulge contribute to hair cycles, follicle regeneration, and wound repair in epidermal layer of the skin. The Bulge is independent from the Dermal Papilla but interplay with each other during follicular cycling. The cellular “communication” between the Bulge and the Dermal Papilla is not fully understood yet.
Controls of Hair Follicle Cycling, K.S. Stenn and R. Paus (2001)
The illustration of hair follicles in different stages is detailed in this paper. Section on Stem Cells of the Follicle discusses their role and location. (Location of stem cells seems to change with stages of growth.) Section on Telogen stage has an interesting suggestion that Telogen may not be a resting phase, as we previously understood.
Capturing and Profiling Adult Hair Stem Cells (2006)
In this study they isolated and traced stem cells and observed their activity. They were able to address the debate whether bulge stem cells directly contribute to hair regeneration at onset of anagen phase. They showed direct involvement of bulge cells in regeneration process during anagen. They also observed some low presence of bulge stem cells in telogen phase.
Epithelial Stem Cells: A folliculocentric View, G. Cotsarelis (2006)
This is a general review on studies involving the Bulge, stem cells roles. The colored illustrations of follicles in different stages are clear to interpret. Two different models illustrate Bulge stem cell locations at different growth stages based on two theories.
For those that might find this interesting, this study is on how stem cells from follicle bulge migrate towards epidermis and contribute to wound healing process.