Biohistory Jyournal, Autumn, 2003

Research: Index > Niche - The cradle of cells transcending time

Time in cells Niche - The cradle of cells transcending time

Shin-ichi Nishikawa Riken Center for Developmental Biology, Stem Cell Research Group

Our bodies weave into a single period of time all the links of cell masses that metabolize over various periods. Blood has its own time, as do the intestines. These are further bound together to create time in an individual body. Stem cells combine these different times by differentiating and supplying new cells when needed.     Stem cells differentiate into new cells in three stages (lower diagram). At the initial SC stage--an important stage that supports stem cells as stem cells-- there are cells supporting this process. These are the stem cell niche. We do not understand, however, the type of cells that constitute the stem cell niche. Here we use the tissue of hair roots in mice to discuss our understanding of the way in which the niche actively determines the conditions of a stem cell. Upper photograph Part of the hair root tissue taken from a mouse. The cells of the pigment stem cell system have been dyed blue. Lower photograph The pigment stem cells that have begun to divide move downward.

The stem cell system is divided into three stages. The stem cell niche is a cell mass that supports the stem cell at the SC stage from the periphery.

The pigment stem cell that bring the existence of the niche into sharp relief.

When a replacement hair grows, the transient portion is lost and a new hair root is created from the permanent portion. The pigment stem cells also sprout new black hair in tandem with the metabolism. We follow the cell movement during this period and identify how niche support the stem cell system.

An enlargement

We dyed only the pigment cell inside the hair root to trace the stem cell system in detail. During the dormant period, as shown in the upper diagram, the cells of the lower end of the permanent portion and the lower part of the bulge area are in the SC stage. This is thought to be the stem cell. There are only one cell or several ones for each hair root. A new pigment cell is created from this stem cell from the dormant period to the growth period.     Throughout the growth period, the pigment cell is observed in two locations--the lower part of the bulge area and the hair matrix. (Photograph: ) The pigment cell in the TA stage (Photograph: red circle) moves downward with the hair matrix as the division continues, and gradually advances to the DC stage. Part of the pigment cell remains in the bulge area at this time.     During the regression period, the hair matrix cells are lost with each transient portion, but the small amount of pigment cells that remained at the lower portion of the bulge area are unchanged. The cells in this part are firmly maintained by the stem cell niche. This is at the SC stage, so they act as stem cells during the next period.     In an extremely interesting development, we have discovered that once the cell differentiates, the stem cell traits are recovered by the niche. The niche is active. This is our most advanced understanding of the familiar topic of growing replacement hair.

Shin-ichi Nishikawa Born in Shiga Prefecture in 1948. Graduated from the Kyoto University School of Medicine in 1973. Studied as an Alexander von Humboldt Foundation scholar at The University of Cologne's Institute for Genetics in West Germany. After returning to Japan, Nishikawa served as associate professor at the Department of Thoracic Surgery in the Research Institute for Tuberculosis at Kyoto University, associate professor at the Kumamoto University School of Medicine, and professor at the Department of Molecular Genetics at the Kyoto University School of Medicine. At present, he is the deputy director of the Riken Center for Developmental Biology and the director of the Center's Stem Cell Research Group.

		Genome Imprinting - Time Implanted in a Generation

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