External Light Activates Hair Follicle Stem Cells Through Eyes Via an ipRGC–SCN–Sympathetic Neural Pathway

June 2018 in “ Proceedings of the National Academy of Sciences of the United States of America ”

Shih‐Kang Fan, Yu-Hao Chang, Chih-Lung Chen, Wei‐Hung Wang, Ming‐Kai Pan, Wen-Pin Chen, Wen‐Yen Huang, Zijian Xu, Hai-En Huang, Ting Chen, Maksim V. Plikus, Shih‐Kuo Chen, Sung‐Jan Lin

hair follicle stem cells intrinsically photosensitive retinal ganglion cells ipRGCs suprachiasmatic nucleus SCN sympathetic neural pathway norepinephrine autonomic nervous activity hair stem cells retinal ganglion cells sympathetic nervous system adrenaline

TLDR Light can turn on hair growth cells through a nerve path starting in the eyes.

The study from June 29, 2018, demonstrated that external light can activate hair follicle stem cells through a neural pathway that begins with the stimulation of intrinsically photosensitive retinal ganglion cells (ipRGCs) in the eyes. Following light stimulation, ipRGCs trigger the suprachiasmatic nucleus (SCN), which in turn activates systemic sympathetic activities. These activities lead to the release of norepinephrine in the skin, which activates hair follicle stem cells. This finding reveals a novel function of ipRGCs in regulating autonomic nervous activity and illustrates how the body can rapidly respond to external light stimuli, potentially affecting not just hair follicles but other organs as well.

View this study on pnas.org →

Discuss this study in the Community →

Cited in this study

21 / 21 results

research A New Path in Defining Light Parameters for Hair Growth: Discovery and Modulation of Photoreceptors in Human Hair Follicle

70 citations , April 2017 in “Lasers in surgery and medicine”

Blue light promotes hair growth by interacting with specific receptors in hair follicles.

research Hair Follicles’ Transit-Amplifying Cells Govern Concurrent Dermal Adipocyte Production Through Sonic Hedgehog

75 citations , October 2016 in “Genes & Development”

Cells in hair follicles help create fat cells in the skin by releasing a protein called Sonic Hedgehog.

research Exploring the Brain-Skin Connection: Leads and Lessons from the Hair Follicle

30 citations , October 2016 in “Current research in translational medicine”

Hair follicles on the scalp interact with and respond to the nervous system, influencing their own behavior and growth.

research The Modulatable Stem Cell Niche: Tissue Interactions During Hair and Feather Follicle Regeneration

66 citations , April 2016 in “Journal of Molecular Biology”

The document concludes that for hair and feather growth, it's better to target the environment around stem cells than the cells themselves.

research Visible Red Light Enhances Physiological Anagen Entry In Vivo And Has Direct And Indirect Stimulatory Effects In Vitro

35 citations , December 2014 in “Lasers in surgery and medicine”

Red light promotes hair growth by directly stimulating hair cells and improving cell communication.

research Local Circadian Clock Gates Cell Cycle Progression of Transient Amplifying Cells During Regenerative Hair Cycling

116 citations , May 2013 in “Proceedings of the National Academy of Sciences of the United States of America”

Hair grows faster in the morning and is more vulnerable to damage from radiation due to the internal clock in hair follicle cells.

research Nerve-Derived Sonic Hedgehog Defines a Niche for Hair Follicle Stem Cells Capable of Becoming Epidermal Stem Cells

396 citations , May 2011 in “Cell stem cell”

Nerve signals are crucial for hair follicle stem cells to become skin stem cells and help in wound healing.

research Beta-Catenin Activity in the Dermal Papilla Regulates Morphogenesis and Regeneration of Hair

314 citations , April 2010 in “Developmental Cell”

β-catenin in the dermal papilla is crucial for normal hair growth and repair.

research Melatonin and the Hair Follicle

109 citations , October 2007 in “Journal of pineal research”

Melatonin helps regulate hair growth and protects the hair follicle from stress.

research Modulation of Hair Growth with Small Molecule Agonists of the Hedgehog Signaling Pathway

113 citations , October 2005 in “Journal of Investigative Dermatology”

Applying a special compound can promote hair growth without harmful side effects.

research The Role of Melatonin in Neuroectodermal-Mesodermal Interactions: The Hair Follicle Synthesizes Melatonin and Expresses Functional Melatonin Receptors

122 citations , July 2005 in “The FASEB journal”

Hair follicles produce and respond to melatonin, affecting hair growth and sensitivity to estrogen.

research Prolactin and Its Receptor Are Expressed in Murine Hair Follicle Epithelium, Show Hair Cycle-Dependent Expression, and Induce Catagen

91 citations , May 2003 in “American Journal of Pathology”

Prolactin affects hair growth cycles and can cause early hair follicle regression.

research Induction of the hair growth phase in postnatal mice by localized transient expression of Sonic hedgehog

231 citations , October 1999 in “Journal of Clinical Investigation”

Activating the Sonic hedgehog gene in mice can start the hair growth phase.

research Neural Mechanisms of Hair Growth Control

101 citations , January 1997 in “Journal of Investigative Dermatology Symposium Proceedings”

Nerves and chemicals in the body can affect hair growth and loss.

research Thyroid and gonadal regulation of hair growth during the seasonal molt in the male European badger, Meles meles L

29 citations , February 1987 in “General and comparative endocrinology”

Thyroid and gonadal hormones control seasonal hair growth and molting in male European badgers.

research Propranolol induced alopecia

33 citations , August 1973 in “American Heart Journal”

Propranolol can cause reversible hair loss.