Cortical Cell Types and Intermediate Filament Arrangements Correlate with Fiber Curvature in Japanese Human Hair

The study investigated the structural biology of naturally straight and curved hair from Japanese women, focusing on the correlation between cortical cell types, intermediate filament (IF) arrangements, and fiber curvature. Using transmission electron microscopy (TEM) and fluorescence light microscopy (FLM), the researchers classified cortical cells into four types (A, B, C, and D). Types A and B resembled orthocortex cells in wool, while Types C and D were similar to meso- and paracortical cells but with distinct differences. The study concluded that the distribution and arrangement of these cortical cells and their IFs influence hair curvature, providing a possible mechanism for how these structural features contribute to hair shape.