Organ Regeneration | Hair Follicle Regeneration

Regenerative therapy of hair - Hair function

Hair Types and Hair Function

Mouse HairHuman Hair

As in many animals, human hair has a function as sensory organ and the physiological function of protecting the skin from environmental influences such as ultraviolet ray or temperature change (Figure).

In addition, humans are social animals and perceive individual, distinguishing characteristics of personality or youth to be expressed by scalp hair, eyebrow, mustache, and other bodily hair (Figure).

Hair has the above properties, including thickness, length, quality, color, density according to the area where the hair grows.

Figure: Type, distribution, and function of hair

(a) Distribution and function of hair in mice and humans

(b) Comparison between mouse hair and whiskers

(c) Comparison between human scalp hair and body hair Legend: M, pith; C, cortex of hair shaft. Bars, 20 m.

Alopecia therapeutic strategy by hair regenerative therapy: A comparison with previous technologies

Treatment strategy for male pattern alopecia

Comparison between self-hair transplantation and hair follicle regenerative therapy

In Japan, 12 million or more men have male pattern boldness, as well as various inconveniences and skin diseases related to hair, including alopecia areata, hair hypoplasia caused by a genetic predisposition.

Hair follicles, the organs that create hair, may become smaller due to the influence of androgenic hormones, and they may develop alopecia when they are destroyed by autoimmunity diseases or injury. Currently, medical or surgical treatment is successfully performed in many patients with alopecia. So far, some treatment methods have become widespread, including drugs to inhibit the influence of androgens, and autologous transplnatation of hair follicles in which hair follicles are removed from normal areas and transplanted to hair loss areas (Figure).
However, these treatment technologies are not effective in all cases and cannot increase the number of healthy hair follicles.

Therefore, hair regenerative therapy, using the patient’s cells, reproduces hair follicles from the hair follicle germ, the origin of normal hair follicles (Lower Figure 1).

Figure: Alopecic treatment strategy

(a) Treatment strategy for male pattern alopecia

(b) Comparison between self-hair transplantation and hair follicle regenerative therapy

Stem cells with organ regenerative ability in adult hair follicles

Development of hair follicle and the hair reproductive cycle

Stem cell niche in adult's hair follicle

Hair follicles, the organs producing hair, are formed by epithelial mesenchymal interaction during the fetal days, similar to other organs (Upper Figure).
While other organs are formed only during the fetal days, hair follicles reproduce during periodic hair cycles.

It is thought that the hair follicle has epithelial stem cells located in bulge area which is slightly swelled position near the sebaceous gland and retains the ability of hair follicle reproduction. This hair follicle reproduction is induced by papilla cells, which have multipotency to differentiate into dermis or subcutaneous tissue (Lower Figure).
Additionally, the stem cells of the melanocyte that controls hair color also exist around the bulge area. These stem cells are maintained at a three-dimensional niche, and they retain regenerative ability throughout the lifetime.

Figure 3: Development of hair follicle and hair follicle stem cell niche

(a) Development of hair follicle and the hair reproductive cycle

(b) Stem cell niche in adult’s hair follicle

Regeneration of hair follicle from stem cells

Reproduced hair by fetal hair follicle germ

Reproduced hair by adult whisker cell

The organ germ method, that we previously developed could autonomously regenerate fully functional hair follicle and tooth from the fetal germ cells.
We developed the organ germ method to apply the technology to adult cells in order to regenerate hair follicles that are normally connected to the dermal epidermal layer and other tissues.

This technology, a major breakthrough in the practical use of hair regenerative therapy, enables the reproductive hair follicle to connect adequately to the surrounding tissues and to be reproduced functionally. In the future, we will contribute to hair regenerative therapy via transplantation therapy through the reproduction of hair follicle germ with autologous stem cells.

Figure: Reproduction of hair by the organ prototype method

(a) Reproduced hair by fetal hair follicle germ

(b) Reproduced hair by adult whisker cell (Skin implant)