Histology and Ultrastructure of Canine Hair Follicle Stem Cells

The study on adult canine skin aimed to identify the location of hair follicle stem cells, which are crucial for cyclical hair growth and differentiation. Through histological and electron microscopy analysis, researchers found that undifferentiated cells, identified as canine Hair Follicle Stem Cells (cHFSCs), were located in the isthmus/bulge region of the hair follicle, between the sebaceous gland duct opening and the arrector pili muscle insertion. These cells, characterized by a single nucleolus and euchromatic karyoplasm, lacked keratin filaments and other organelles in their cytoplasm and were surrounded by spindle-shaped telocytes, forming a niche in the bulge region. The findings supported the hypothesis regarding the specific location of cHFSCs in canine hair follicles.