Trichohyaline granules in hair cortex

Area of Science:

• Dermatology
• Cell Biology
• Hair Follicle Biology

Background:

• The hair cortex is crucial for hair structure and properties.
• Understanding the cellular components involved in hair keratinization is key to hair biology.

Purpose of the Study:

• To identify and characterize granular structures within the keratogenous zone of the human hair cortex.
• To investigate the presence and distribution of these granules in other species.

Main Methods:

• Transmission electron microscopy was used to examine the ultrastructure of human hair follicles.
• A comparative survey of hair cortex from human, guinea pig, and mouse was conducted.

Main Results:

• A distinct granular structure, 0.1-0.3 micron in diameter, was observed in human hair cortical cells within the keratogenous zone.
• These granules, identified as trichohyaline granules, were electron-dense, homogeneous, and not membrane-bound.
• Similar trichohyaline granules were found in guinea pig hair cortex but were notably absent in mouse hair cortex.
• The granules appeared fused to tonofilaments and disappeared before complete cortical keratinization.

Conclusions:

• The observed granular structures are identified as trichohyaline granules, playing a role in the keratogenous zone of hair cortex.
• The presence of trichohyaline granules is conserved in human and guinea pig hair but not in mouse hair, indicating species-specific variations in hair formation.
• Further research is warranted to elucidate the precise function of trichohyaline granules in hair keratinization.