Physiological Regeneration of Skin Appendages and Implications for Regenerative Medicine

The document from 2012 reviews the physiological regeneration of skin appendages, such as hair and feathers, and its relevance to regenerative medicine. It explains that this regeneration is driven by cycles of activation and quiescence of organ stem cells, with hair and feather follicles serving as models for studying stem cell activation and organ formation. The paper discusses how skin appendages adapt to environmental and life stage changes, and how these adaptations have evolved. Significant progress has been made in understanding the molecular aspects of hair and feather follicles, particularly the location of stem cells and regulation of their activity. The study also examines how hair follicle stem cells are affected by external factors like seasonal changes and systemic hormones, and how hormonal changes can differently influence hair growth or loss in various body areas. The role of dermal papilla cells in interpreting hormonal signals is highlighted, and the need for further research on the specificity of hormone response and regional specification of hair follicles is emphasized. Additionally, the document suggests that principles learned from physiological regeneration could be applied to regenerative medicine, potentially leading to new strategies for hair and feather growth and reprogramming cells for new follicle formation after injury.