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Institute of Biomedical Engineering and Department of Life Sciences collaborative research concerning light regulation of hair follicle stem cells on PNAS

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Poster:Post date:2018-07-20
   

Prof. Sung-Jan Lin(林頌然) from the Institute of Biomedical Engineering and Assoc. Prof. Shih-Kuo Chen(陳示國) from the Department of Life Sciences have published a paper to discuss the transmission of external sudden intense light through the intrinsically photosensitive retinal ganglion cell (ipRGC). The suprachiasmatic nucleus (SCN) further stimulates the sympathetic nerves to activate hair follicle stem cells. Stem cells are regulated by the local microenvironment and the systemic environment to remain stationary or activated. How the external environment (meganiche) talks to stem cells in the body is currently less understood. This achievement will provide a new direction for studies on the regulation of physiological functions and stem cell activity in the body by external light. The paper was published on June 29, 2018 in the Proceedings of the National Academy of Sciences (PNAS).

Prof. Lin is currently the attending physician of the Department of Dermatology (NTUH) and the deputy director of the NTU Developmental Biology and Regenerative Medicine. The laboratory has long been focusing on hair follicle stem cells and hair follicle regeneration. Hair follicles have the property of periodic growth, and activation of telogen hair follicle stem cells through appropriate stimulation is the key to hair regeneration. Prof. Lin's main research focus on how the outer environment affects stem cells and promotes hair follicle regeneration by regulating microenvironmental factors.

Prof. Chen's laboratory mainly studies how environmental light can influence the physiological functions of animals through the expression of ipRGCs in the retina, such as regulating physiological clocks, energy metabolism, and cognitive behavior. Because melanopsin is highly sensitive to blue light, regular day and night light periods, especially blue light, can affect the animal's sleep, weight metabolism, mood, and learning ability through the ipRGCs.

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Figure1. Research team, from the left to the right, Assoc. Prof. Wen-Pin Chen(陳文彬) from the Institute of Pharmacology, Assoc. Prof. Shih-Kuo Chen from the Department of Life Sciences, the first author Sabrina Mai-Yi Fan(范邁儀) from the Institute of Biomedical Engineering, Prof. Sung-Jan Lin from the Institute of Biomedical Engineering and Assistant Prof. Ming-Kai Pan(潘明楷)from the Department of Neurology.


For many animals, hair is the first line to protect the skin, and periodic hair regeneration can renew damaged hair. When seasonal changes cause changes in sunshine hours, it affects the hair growth of the animal. Therefore, hair follicle stem cells that are not exposed to light directly can experience changes in response to the external environment. But how do these two types of cells, which lack contact with each other, crosstalk? This is the issue that this study explores.

This study found that mice exposed to bright light (especially blue light) for a few minutes can activate hair follicle stem cells to regenerate new hair. This is physiological induction of “turn a blind eye”. It is not governed by photoreceptor cells related to visual imaging, such as cone and rod cells. Instead, light signals are interpreted by ipRGCs which signal via melanopsin to SCN. Subsequently, efferent sympathetic nerves are immediately activated. Increased norepinephrine release in skin promotes hedgehog signaling to activate hair follicle stem cells. This reaction does not affect the original day and night physiological cycle.

This study also revealed that ipRGCs in the retina regulate the new functions of the autonomic nervous system, as well as the possibility of multiple neural circuits in controlling the physiological clock to control many different physiological functions. For example, when a mouse is stimulated by an intense blue light, the heart beats faster, sweats, and adrenal sympathetic nerve activity increases.

Mice are nocturnal animals that intense ambient light can be a danger signal to warrants immediate reaction. In physiological conditions, mice would not receive prolonged intense light stimulation to the eyes during the day time unless they are threatened, such as being chased by predators or forced to move due to harsh environmental changes. Because it is inevitable that hair will be damaged in a critical situation, rapid regeneration of new hair can provide protection.

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Figure2. Depiction of the neural pathway for light-stimulated sympathetic activity and hair follicle stem cell activation. (Fan SMY, et al. PNAS 2018)



This study answers this physiological mechanism by combining professional and experimental methods in different fields. The first author of this study is Dr. Sabrina Mai-Yi Fan, who graduated from the
Institute of Biomedical Engineering (NTU). She is currently a postdoctoral researcher at the Department of Medical Research (NTUH). The second author is Yi-Ting Chang, a graduate of the Department of Life Sciences (NTU). She is currently studying a doctoral degree at Johns Hopkins University. The researchers from the Institute of Biomedical Engineering (NTU) also include Dr. Chih-Lung Chen, Dr. Wei-Hung Wang, Dr. Wen-Yen Huang and Hai-En Huang. Assoc. Prof. Wen-Pin Chen from the Department and Graduate Institute of Pharmacology College of Medicine (NTU), Assistant Prof. Ming-Kai Pan from the Department of Neurology (NTUH), Prof. Maksim Plikus from University of California Irvine and Ting Chen is a researcher from the National Institute of Biological Science (Beijing, China), also participated in this collaborative research as co-authors. The research team also thanked Dr. Ta-Ching Chen from the Department of Ophthalmology (NTUH), Prof. Sung-Tsang Hsieh from the Department of Anatomy and Cell Biology, College of Medicine (NTU) and Dr. June-Tai Wu from the Department of Dermatology (NTUH) for their assistance and suggestions during the experimental process.

The study was completed with the support of the research project between National Taiwan University Hospital and colleges by the National Taiwan University Hospital, Ministry of Science and Technology(MOST) and the Taiwan Bio-Development Foundation (TBF). For detailed research results, please refer to the full text "External light activates hair follicle stem cells through eyes via an ipRGC-SCN-sympathetic neural pathway"; Reference website: https://doi.org/10.1073/pnas.1719548115.

 

 

Last modification time:2019-06-27 PM 2:27

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