Ultrastructure of human scalp hair shafts as revealed by freeze-substitution fixation

Abstract

Human scalp hair is important as a diagnostic clue to many diseases, in medical jurisprudential investigations, and also as a subject of cosmetic treatments. While many ultrastructural studies of the human hair root including the hair follicle have been reported, few studies have been done on the human hair shaft. We report here the ultrastructure of human scalp hair shafts prepared by a rapid-freezing technique followed by freeze-substitution fixation that allows the observation of fine cell structures. Healthy scalp hair shafts from Japanese females 12-13 years of age were rapid-frozen and then freeze-substituted in OsO4-acetone. In addition, this technique was applied to the study of some changes of the hair shafts (i.e., hair damaged by thioglycolic acid cold permanent waving and white hair). By this method, the hair shaft was rapid-frozen throughout without appreciable ice damage although the hair shaft was nearly 100 microm in diameter. The rapid-freezing technique resulted in excellent preservation of the ultrastructure of the hair shafts: lamellar structures in the cuticle and fine fibrous ultrastructures in the cortex were observed without chemical treatments. Thioglycolic acid treatment affected the ultrastructure of both the cuticle and the cortex. Except for the absence of melanin granules, no significant differences in the ultrastructure were observed between white hair and black hair. The rapid-freezing technique followed by freeze-substitution fixation appears to be the most reliable approach for the morphological evaluation of fully keratinized cells and tissues.

The influence of hair bleach on the ultrastructure of human hair with special reference to hair damage

“…The cuticle CMC and the cortex CMC showed a slightly lower electronic density than the structures around them. In the white hair samples, melanin granules were very few or non existent, but the rest of their structures were basically the same as those of black hair 6) .…”

“…The electronic density of the A-layer is increased but that of the endocuticle is decreased with cold permanent wave treatment, which contains thioglycolic acid as a reducing ingredient, and it is thought that OsO 4 reacts with the cleaved disulfide bond of cystine through the action of the reducing agent 6) . On the other hand, in the Os+Es images of this study, the electronic density of both A-layer and endocuticle was increased in the bleached hair ( Fig.…”

Reduction and Block Staining of Human Hair Shafts and Insect Cuticles by Ammonium Thioglycolate to Enhance Transmission Electron Microscopic Observations

“…However, treatment with ATG or 2-mercaptoethanol in phosphate buffer has been used to observe the fibrillar structure in the cortex. In addition, the A-layer in hair cuticle cells is also stained [6][7].…”

Ultrastructural Localization of Hair Keratins in Human Scalp Hair Shafts as Revealed by Rapid-Freezing Immunocytochemistry.

“…Recently, we have introduced a rapidfreezing technique followed by a freeze-substitution fixation in the ultrastructural study of the human scalp hair shaft and have shown excellent ultrastructures in a form close to those in the living state [25]. Thus, we have employed the rapid-freezing technique in order to study the immunoelectron microscopic distribution of hair keratins in the hair shafts.…”

“…One reason for that is that the technical complication due to poor penetration of chemical reagents (i.e., chemical fixatives, dehydration alcohol and embedding media) into the dry tissue during preparation for transmission electron microscopy (TEM) analysis. Recently, we have overcome this obstacle by applying a rapid-freezing and subsequent freeze-substitution fixation technique to the ultrastructural study of the human scalp hair shaft and have revealed its fine inside view by TEM [25]. It would be interesting to show in situ subcellular distribution and differential expression of hair components on the fine structure of human hair as revealed by the rapidfreezing technique.…”