Category Archives: Junji Fukuda

Dermal Papilla Cells, Hormones, Junji Fukuda, Serotonin

Hormonal Influences on Dermal Papilla Cells

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We have always been told that the hormone dihydrotestosterone (DHT) is by far the dominant cause of male pattern hair loss (aka androgenetic alopecia). However, numerous other hormones have positive and negative effects on scalp hair growth. I only realized this fully after a new study found yet another hormone to have an impact on hair growth. See the bottom of this post for a full list.

Serotonin and Hair Loss

A July 2025 publication by the renowned Dr. Junji Fukuda’s team in Japan found that serotonin (5-hydroxytryptamine, 5-HT) activates hair growth related genes in dermal papilla (DP) cells. Serotonin is both a neurotransmitter and a hormone. It is often confused with dopamine, since both are neurotransmitters, hormones and feel good molecules. Note that an older 2014 study also found that 5-HT plays a role in regulating hair pigmentation and stress-induced depigmentation.

In this study, the authors mention that circulating serotonin is mainly produced via intestine-microbiome interactions. They also briefly discuss how the microbiome produces various factors and metabolites that influence hair growth and hair regression. This has become an interesting new area of hair loss research, including via related research into the use of live biotherapeutic products to treat hair and skin disorders.

Serotonin Hormone and Hair Growth
Serotonin, hair growth and dermal papilla-intestine interactions. Source: Scientific Reports, July 2025.

Circulating Hormones and their Influence on Dermal Papilla Cells

One paragraph in the above study in regards to various hormones and their effect on hair growth caught my eye. Especially since I have covered a few of them on this blog (see highlighted links below) without realizing that the number has built up.

“Multiple circulating hormones influence DP cells. For example, dihydrotestosterone shortens the anagen phase of DP cells, while increased estrogen levels (e.g., during pregnancy) spur additional hair growth. Likewise, oxytocin and cortisol exert opposing effects on DP cells and hair growth, the former activating growth factor secretion (stimulatory) and the latter decreasing Gas6 expression (inhibitory). The circadian hormone melatonin promotes hair regeneration via activating Wnt signaling in DP cells. Research on novel hair growth-promoting hormones has accelerated worldwide in pharmaceutical and cosmetic industries, largely targeting these hormones.”

Other hormones that can affect hair growth include: the earlier mentioned serotonin; thyroid; growth hormone; testosterone; insulin and insulin-like growth factor (IGF); and prolactin.

Hormonal Influences on Dermal Papilla Cells

Below is a summary of all the hormones I have discussed in this post and their impact on hair growth (usually via impacting dermal papilla cells):

  • Dihydrotestosterone = Negative (-).
  • Estrogen = Positive (+).
  • Oxytocin = Positive (+).
  • Cortisol = Negative (-).
  • Melatonin = Positive (+).
  • Thyroid = Positive (+).
  • Testosterone = Negative (-).
  • IGF-1 = Positive (+).
  • Prolactin = Negative (-).
  • Serotonin = Positive (+).
Junji Fukuda, Hair Beads, Hair Follicle Germs, Yokohama National University

Preparation of Hair Beads and Hair Follicle Germs

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I have covered hair regeneration research by Yokohama University’s Dr. Junji Fukuda and his Fukuda Lab a few times in the past. He is highly respected in the world of hair loss research.

Update: June 30, 2025

Preparation of Hair Follicle Germs using Centrifugal Forces

The Fukuda team has published a new study on the preparation of hair follicle germ-like aggregates. They found that a centrifugal approach significantly improves hair follicle regeneration efficiency compared with that of conventional cell suspension injection.

Update: February 12, 2024

A new study from Dr. Junji Fukuda and his team covers their development of a microfluidic-device based approach for the large-scale preparation of hair follicle germs (HFGs).

Update: September 8, 2019

Preparation of Hair Beads and Hair Follicle Germs

Last month, Dr. Junji Fukuda and his team published a groundbreaking new study titled: “Preparation of hair beads and hair follicle germs for regenerative medicine“. The team managed to generate new hair follicles from stem cells in far higher quantities than ever before in mice. This news was widely covered, including in today’s Guardian newspaper.

The researchers’ approach entailed use of a collagen gel in combination with spheroids formed from epithelial cells. This resulted in something called bead-based hair follicle germs (bbHFGs). These germs generated hairs more efficiently than previous approaches. A hair-raising protocol per one headline.

The success of this approach will potentially lead to the preparation of microtissues with high trichogenic ability upon transplantation. A key necessity in future hair follicle germ creation and transplantation from stem cells in humans.

Past research from Dr. Fukuda is here. The researchers next step is to “find a way to expand the number of hair follicle stem cells“.

February 2, 2018

Large-Scale Production of Hair Follicle Germs

I have covered Dr. Junji Fukuda and the Fukuda Lab several times on this blog in the past. Their important hair related research takes place at Yokohama National University in Japan. Most recently, this was just two weeks ago in relation to their latest paper titled: “Spontaneous hair follicle germ (HFG) formation in vitro, enabling the large-scale production of HFGs for regenerative medicine“. It was published towards the end of 2017, but seems to now be dated as 2018.

Junji Fukuda: Hair Follicle Germs (HFGs) Preparation.
Junji Fukuda: Hair Follicle Germs (HFGs) Preparation.

At the time, I decided that this development was only worth a cursory mention in my once a month “brief items of interest” post. My decision was clouded by the fact that this research only entailed work on mice (see bottom part of image on left, courtesy Yokohama National University). We are all a bit bored/tired/frustrated with that of course.

However, earlier today, Dr. Fukuda and his team’s work was covered in the Science Daily publication. Key quote from Dr. Fukuda:

“This simple method is very robust and promising. We hope that this technique will improve human hair regenerative therapy to treat hair loss such as androgenic alopecia,” adds Fukuda. “In fact, we have preliminary data that suggests human HFG formation using human keratinocytes and dermal papilla cells.”

Perhaps this really might end up being a major development, even in humans.

Tsuji, Shiseido, Ohyama and perhaps now Fukuda? I have never been to Japan, but it looks like this may change in the future.