Posted on: February 27, 2002
It is a well established fact, that hair stem cells are located in bulge, located in the upper part of outer root sheath. It was assumed, that these stem cells divide and produce so called TA cells (transient amplifiers). TA cells have an ability to divide very quickly but finite number of times. Also, they finally terminally differentiate. Hair specific TA cells are located in bulge at the bottom of the hair follicle.
Yet, question of whether that bulb region of hair follicles also contains multipotential progenitors (stem like type of cells, rather than just TA cells) is still open.
To address this issue, one of the research group created chimeric mice, buy injecting embryonic LacZ-expressing (LacZ will result in Blue staining of these cells) stem cells into early mouse embryo. This resulted in production of chimeric hair follicles, where some cells were LacZ positive (Blue), other - LacZ negative (White).
Based on comparative analysis of several chimeric hair follicles, it was concluded, that hair follicle bulb (the very bottom of hair follicle), indeed, contain multipotential progenitor cells. I.e. there are cells at the very base of the bulb, that give rise to all typer of hair fiber and inner root sheath cells.
Yet, in some instances oligopotential stem cells were found (they produced only one type of hair fiber cells).
Researches went even further and defined the number of these progenitor (stem) cells in each hair follicle bulb. "...On average the bulb contains four or fewer active progenitors, each capable of giving rise to all six follicular epithelial fates..."
3-D reconstruction models located on this official site:
molecool.wustl.edu/kopan.movies.html
support authors' idea.
This work, apart of having theoretical value, give more credentials to Dr. Gho hair multiplication technique. In this technique, bulbs of plucked hair are cultivated and resulting cells are transplanted back into donor area. If, like in mouse, hair follicle bulbs contain real stem cells, one can predict, that induced via hair multiplication hair follicle would function for many hair cycles. presence of stem cells will ensure, that hair epithelial cells population won't be depleted after several rounds of division.
From: Developmental Biology, Vol. 242, No. 1, Feb 1, 2002
By: Raphael Kopan at. al. |
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