Histological structure of human nail as studied by synchrotron X-ray microdiffraction

Area of Science:

• Biophysics
• Materials Science
• Dermatology

Background:

• Human nails are complex biological structures crucial for protection and dexterity.
• The mechanical properties of nails are attributed to their unique keratinous composition and arrangement.
• Understanding nail structure is vital for diagnosing and treating nail diseases like onychomycosis.

Purpose of the Study:

• To elucidate the three-dimensional keratin organization within human nail plates.
• To investigate the impact of onychomycosis on the nail's keratin structure.
• To correlate nail structure with its mechanical properties.

Main Methods:

• Synchrotron X-ray microdiffraction was employed to analyze keratin molecule orientation in three distinct nail layers.
• Microscopic analysis characterized the histological dorsal, intermediate, and ventral plates.
• Lipid bilayer presence and distribution were also examined.

Main Results:

• Human nails exhibit three layers with specific keratin orientations: dorsal, intermediate (alpha-keratin filaments perpendicular to growth axis), and ventral.
• Keratin filaments in dorsal and ventral layers are oriented parallel and perpendicular to the growth axis.
• Lipid bilayers are present in specific regions, contributing to nail structure.
• Onychomycosis was found to disrupt the native keratin structure, likely during synthesis.

Conclusions:

• The human nail's layered keratin organization provides exceptional mechanical rigidity.
• Onychomycosis significantly alters the nail's structural integrity by disrupting keratin arrangement.
• Further research into fungal-keratin interactions is warranted for therapeutic development.