Seiichi Arai’s research while affiliated with Jichi Medical University and other places

We have characterized the subcellular distribution of S100A3, a cysteine-rich calcium binding protein, in human scalp hair shaft. This was accomplished using rapid-freezing immunocytochemistry, a technique that combines rapid-freezing, freeze-substitution fixation without chemical fixatives, and subsequent electron microscopic detection of immunocytochemical labeling. This technique preserves both the antigenicity and the ultrastructural integrity of fully keratinized tissues, which are highly unmanageable when prepared for immunoelectron microscopy. In the hair shaft, S100A3 was primarily identified in the endocuticle and was also present in the intermacrofibrillar matrix surrounding macrofibril bundles of intermediate filament keratins in cortex cells. Double immunolabeling of S100A3 and hair keratins revealed the in situ spatial relationship between them. In the endocuticle, S100A3 was present on the inner portion of the endocuticle adjacent to the cell membrane complex, whereas hair keratins were present on the outer portion. These results provide the first ultrastructural evidence that an S100 protein is localized in specific subcompartments in human hair cells. (J Histochem Cytochem 47:525-532, 1999)

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.

Although many hair proteins have been investigated biochemically, little information is available on their subcellular distribution in human hair. We report here on the immunoelectron microscopic technique for defining the ultrastructural localization of hair proteins, especially hair keratins, in human scalp hair shafts: a combination of a rapid-freezing, freeze-substitution fixation without chemical fixatives, and subsequent immunocytochemistry (i.e., rapid-freezing immunocytochemistry). The hair shafts were rapid-frozen, freeze-substituted in acetone without chemical fixatives, and then embedded in LR White resin. Subsequently, ultrathin-sectioned samples were stained for hair keratins by an immunogold technique. Rapid-freezing followed by freeze-substitution without chemical fixatives well-preserved not only the fine structure of the hair shafts but also the antigenicity of hair keratins for immunocytochemistry. In the cortex, hair karatins were present mainly on the macrofibrils. In the cuticle, they were also located primarily in the endocuticle, which did not show the fibrous structure like the macrofibrils did. Rapid-freezing immunocytochemistry appears to be the most viable approach for revealing the macromolecular architecture of human hair, which is a completely keratinized tissue and one of the most delicate tissues in preparation for transmission electron microscopy.