Research (English)
In the epidermis of the skin, cell nuclei and mitochondria, which are necessary for epidermal cells to survive, are lost (cell death), and the stratum corneum (outermost layer of the epidermis) is formed using the remaining cell bodies. However, how the nucleus and mitochondria are lost has not been clarified until now.
We have recently developed a live imaging method to clarify the process of cell death of skin epidermal cells and proposed a new type of cell death, "corneoptosis.
We found that during the cell death process of uppermost stratum granulosum cells, SG1 cells. the intracellular calcium ion (Ca2+) concentration rises for about an hour, followed by intracellular acidification while the Ca2+ concentration remains high. Without this acidification, the keratohyalin granules/nuclear DNA degradation did not occur. We also found that the timing of this acidification is regulated by the temperature-sensitive non selective cation channel TRPV3 protein
Matsui T*, Kadono-Maekubo N, Suzuki Y, Furuichi Y, Shiraga K, Sasaki H, Ishida A, Sonoko Takahashi S, Okada T, Toyooka K, Sharif J, Abe T, Kiyonari H, Tominaga M, Miyawaki A, Amagai M*: A unique mode of keratinocyte death requires intracellular acidification. Proc. Natl. Acad. Sci. 118:e2020722118, 2021. (*Corresponding author)
(Commentary in PNAS by Jessica L. Moorea and Prof. Valentina Greco.)
Our another research interest is in "epithelial evolution". Around 360 million years ago, the first terrestrial vertebrate, amphibians emerged from the water and adapted to the life on land. They evolved their surface multilayered epithelia into keratinized stratified squamous epithelia to prevent water loss and to protect the body from sunlight. Placing particular emphasis on this epithelium, we intend to uncover the mystery of "epithelial evolution"
Matsui T and Amagai M: Dissecting the formation, structure and barrier function of the stratum corneum. Int. Immunol. 27: 269-80, 2015.
Matsui T: Endogenous Retroviral-Like Aspartic Protease, SASPase as a Key Modulator of Skin Moisturization. Treatment of Dry Skin Syndrome -The Art and Science of Moisturizers-Edited by Lodén and Maibach, Springer, Part 2: 179-192, 2012.
~News and Topics~
May 16th, 2022: Our paper demonstraing the novel electron microscopic staining method is just published.
May 15th, 2024: The research results have been published online in the scientific journal Nature Communications (May 15, 2024). The discovery is that the stratum corneum, the outermost dead cell layer of the skin that serves the skin barrier function, forms a three-layered structure of pH (hydrogen ion index) to maintain stratum corneum homeostasis.
Fukuda K, Ito Y, Furuichi Y, Matsui T, Horikawa H, Miyano T, Okada T, Logtestijn V. M, Tanaka J. R, Miyawaki A, Amagai M:Three stepwise pH progressions in stratum corneum for homeostatic maintenance of the skin. Nature Communications 15:4062, 2024.