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Human hair shape is programmed from the bulb
S Thibaut1, O Gaillard, P Bouhanna
1L'OREAL Recherche, 14 rue Théodore de Banville, 75017 Paris, France.
The British Journal of Dermatology
|April 21, 2005
Summary
Hair curliness originates in the hair follicle bulb, driven by asymmetrical cell differentiation. This study investigated the unique growth and morphology of curly hair follicles.
Area of Science:
- Dermatology
- Hair Biology
- Cellular Morphology
Background:
- Limited biological data exists for curly hair follicles.
- Understanding curly hair follicle biology is crucial for hair research.
Purpose of the Study:
- To investigate the growth and morphology of curly hair follicles.
- To elucidate the biological basis of hair curliness.
Main Methods:
- Dissection of scalp skin follicles from diverse ethnic groups (African, Guyanese, Caucasian).
- Macroscopic observation, in vitro culture (William's E medium), and immunohistochemistry.
- Analysis of follicle implantation, bulb shape, sheath symmetry, and cell proliferation (Ki-67).
Main Results:
- Curly hair follicles exhibit a curved dermal implantation and a bent bulb, unlike straight Caucasian follicles.
- In vitro growth showed maintained curvature in the hair shaft; proliferation was asymmetrical, with delayed differentiation on the convex side.
- Outer root sheath (ORS) cells expressed alpha-smooth muscle actin on the concave side, indicating mechanical stress.
Conclusions:
- Hair curliness is intrinsically programmed within the hair follicle bulb.
- Asymmetry in differentiation programs is a key factor in determining hair curl.