Three-Dimensional Architecture of Macrofibrils in the Human Scalp Hair Cortex

The study investigated the three-dimensional architecture of macrofibrils in the human scalp hair cortex, revealing that human hair macrofibrils have a consistent matrix fraction and typically exhibit a double-twist architecture. Unlike wool, human hair showed significant inter-macrofibril variation in the incremental angle increase between intermediate filaments (IFs), with a negative correlation between macrofibril size and IF increment. This variation was observed across different hair types, including Caucasian, Japanese, and African, indicating a common feature in human hair. The findings advanced the understanding of the nano-level and cell-level organization of human hair, highlighting the complexity and variability of macrofibril architecture compared to wool.