Written | nagashi
In today's fast-paced life, everyone is under enormous pressure, and our daily work, study and life make us feel under pressure. In the adult world, except for fat , sleepiness and hair loss , everything else is quite easy.
Around the world, up to one billion men, women and even children suffer from hair loss. At the same time, according to the statistics of the National Health and Medical Commission, there are over 4.25 billion people in my country with hair loss, with an average of 1 in 6 people suffering from hair loss. What's even more regrettable is that despite such a large group of people suffering from hair loss, there is currently no good treatment for hair loss.
On June 9, 2021, researchers from RIKEN (RIKEN) published a research paper online entitled: Tracing the origin of hair follicle stem cells in the top international academic journal Nature.
This study combined imaging and gene expression analysis to find that cells are arranged in concentric circles in the disk-like structures that form hair follicles, which predetermines their final fate and location in the mature hair follicle .
This finding improves our understanding of hair follicle development, and future research may reveal ways to regenerate hair follicles, which could eventually be used to treat hair loss.
When you were a child, you might dream of being an astronaut one day, and an actor the next day, and then you had infinite possibilities in the future.Similarly, precursor cells in early embryos, under the control of external forces and internal factors, make a series of step-by-step "decisions" that give rise to the various cell types present in adult organisms, a process known as It is " cell differentiation ".
We know that skin is mainly composed of two parts - epidermis and dermis , the former is a layer of flat epithelial cells , forming a protective barrier against external aggression, the latter contains fibers that support the skin mother cell . Hair follicle Development begins with a clean "placode", dermal layer fibroblasts induce the formation of placodes - the thickening of cells in the epithelial layer that eventually forms the hair follicle.
The substrate forms flattened circles on the skin surface, but how these flattened disc structures eventually transform into long cylindrical 3D shapes is of interest not only to skin and hair researchers, but also to study potential hair replacements that work through developmental mechanisms Questions of interest to scientists of therapy.
In this study, the research team optimized a technique called live imaging to record the movement of cells in cultured skin tissue extracted from mouse embryos starting 11.5 days after conception. The researchers created time-lapse videos of hair follicle development by 3D and microscopic imaging of skin samples over a period of three to five days. By playing these videos in reverse, the researchers traced the embryonic placode origin of fully grown hair follicle cells .
The determination of cell fate depends on the location of the cell.
The research team found that in the early placode structure, the hair follicle stem cell is organized into the shape of concentric circles, like an arrow target. In this way, the cells in the most center form the base of the hair follicle, while the cells on the outer edges of the placode rest on the surface of the skin between the follicles.
Over time, the proliferation and movement of these cells causes the follicle to grow down from the base plate into a fully developed follicle, like an extension of a retractable telescope . Therefore, the research team also refers to this development as the " telescope model ".
The two-dimensional concentric transcriptional landscape is characteristic of the origin of stem cells
In fact, in nature, organisms form cylindrical or other 3D-shaped appendages from a flat surface Examples of such as legs and tentacles are not uncommon, the earliest Scientists have described this phenomenon for the first time in fruit flies. So while this is perhaps unsurprising, it is exciting that this "telescopic mechanism" appears to be evolutionarily conserved across species.
It is worth noting that the emergence of stem cells during hair follicle development further adds to the complexity of this system. In adult animals, this cell is stored in the bulge of the upper follicle and is essential for expanding the follicle during the growth phase of the hair cycle, part of normal tissue turnover throughout the animal's life.
Not only that, these stem cells can even repair damage to other parts of the epidermis. Previous studies also confirmed the origin of hair follicle stem cells in the early placode by tracing the transcription factor SOX9. This suggests that bulging stem cell precursors are created and maintained on the surface of the placode as the placode begins to extend downward, and then eventually colonize the bulge area.
Coordination of the transcriptional landscape of epithelial lineage and stem cell induction in developing hair follicles One-to-one correspondence for single-cell transcriptomic analysis. With this approach, the research team identified a population of cells that expressed bulge stem cell markers during the early stages of placode development.
By performing mathematical modeling on cells at all evaluated time points, the research team determined that cells expressing these markers differentiated into expanded stem cells at an early placode, well before previously reported time points at which differentiation occurred. Consistent with previous reports, these stem cell precursors expressed the gene encoding SOX9. However, by further cell lineage tracing and live imaging, these precursors were unequivocally demonstrated to originate from a previously unidentified peripheral ring region of the early placode.
Enlarged stem cells originate from the periphery of the basal lamina of the placenta
This new spatial localization of cells suggests that previously published findings related to enlarged stem cells may need to be re-examined and the regulatory conditions required to induce this population of cells revisited The problem.
All in all , this study has made tremendous progress in dissecting the role of different cell populations on mature hair follicles, this new discovery not only improves our understanding of hair follicle development, but will also drive further research to uncover the role of regenerating hair follicles. method and will ultimately facilitate the development of hair loss treatments.
Thesis link:
https://www.nature.com/articles/s41586-021-03638-5
https://www.nature.com/articles/d41586-021-01482-1
