MicroRNA Study Furthers Understanding of Genetic Hair Loss

A new study published in the medical journal PlosGenetics has helped to further our understanding of genetic hair loss. Researchers have found that microRNAs contribute to hair loss and follicle regression.

The researchers' aim was to further our understanding of the pathway that leads to genetic hair loss, in order to develop the next generation of hair loss treatments.

What are microRNAs?

RNA stands for Ribonucleic acid, which is one of the three major biological macromolecules that, along with DNA and proteins, is part of the essential makeup of all forms of life. Genetic information in your cells flows from your DNA, through your RNA to the proteins.

microRNAs (miRNAs) are short, single-strands of RNA molecules which regulate gene expression. They are vital for influencing the pathways that are responsible for causing many diseases, as well as androgenic alopecia - better known as Male Pattern Baldness in men or Female Pattern Hair Loss in women.

What we know already

Hair Growth Cycle Diagram

During the active phase of the hair growth cycle, epithelial cells at the base of the follicle actively divide, aided by stem cells. These constantly dividing cells are called matrix cells.

As the cells created by these matrix cells move from the base of the follicle (sometimes referred to as the follicle 'bulb'), they form a hardened hair shaft, which is what emerges from the scalp as hair. These hair shafts are made up of what researchers describe as 'dead, but mechanically sound and highly cross-linked, keratin-filled cells'. This stage of hair production is called the Anagen, or 'growth' phase.

Following the active Anagen growth stage, hair follicles degenerate during the 'Catagen' transitioning stage. The report states that a 'large portion of epithelial cells die, and the remaining stem cells are reduced to a tight cluster underneath the skin surface' during this time.

This is followed by the Telogen, or 'resting' phase of the hair growth cycle - the time when hair production halts and follicles lie dormant, awaiting the signal to resume.  The period between the Telogen phase ending and the next Anagen phase starting, is when hair finally sheds. Unexpected hair loss can occur when production remains 'stuck' in the Telogen phase for an extended period of time.

Therefore, as it has already been established that hair loss results from the premature termination of the follicle’s growth phase, researchers wanted to study the precise workings of the mechanism underlying normal hair regeneration.

Research methods and findings

Immunoflorscent staining of hair follicles - Photo by Yuan and colleagues Immunoflorscent staining of hair follicles - Photo by Yuan and colleagues

As it was understood that the hair growth cycle could be influenced by a number of 'local and systemic signalling factors', researchers honed in on trying to identify new hair follicle regression signals. It was noted that defects in the hair growth cycle could arise due to disease, ageing or injury, and that, should follicles enter their resting phase prematurely, the shafts became shorter and fell out 'resulting in visible baldness'.

By discovering more about the pathway involved in hair loss, they felt it would be likely that they could identify new targets for future hair loss treatments. What they found was that (microRNA) miR-22 induction causes premature hair loss by promoting follicle involution.

Study author, Zhengquan Yu of State Key Laboratories for Agrobiotechnology, College of Biological Sciences at China Agricultural University in Beijing, explains, "To test the function of miR-22, we generated a genetic tool to induce miR-22 overexpression in mouse hair follicles, and interestingly, found that increasing miR-22 results in hair loss in mice due to the premature regression of actively growing follicles."

Hair loss in mice. Image credit Yuan and colleagues Hair loss in mice. Image credit Yuan and colleagues

Adding, "Surprisingly, our data reveal that the expression of over 50 distinct keratin genes are markedly reduced by miR-22 and that silencing of keratin-mediated hair shaft assembly by miR-22 is a prerequisite for follicle regression. At the molecular level, we found that miR-22 directly represses multiple transcription factors, including Dlx3 and Foxn1, which positively regulate the expression of keratin genes. Indeed, deletion of Dlx3 or Foxn1 closely resembles the hair loss phenotype caused by miR-22 induction."

Yu concludes, "Thus, by suppressing Dlx3- and Foxn1-dependent keratin expression, miR-22 is sufficient to terminate hair differentiation. In addition, miR-22 contributes to follicle regression by repressing proliferation of hair stem cells and promoting their death. Collectively, miR-22 emerges as a key regulator of follicle transition from the growth to regression phase."

What this means in less technical terms, is that an excess of the microRNA miR-22 can actively cause hair loss. It prematurely sends the hair growth cycle into its resting phase by disrupting the hair's keratin levels and preventing hair stem cells from replicating, causing them to die, resulting in hair loss.

Insights could lead to next generation treatments

Belgravia Centre Male Hair Loss Treatment Products

The study's findings have produced a significant link between this specific microRNA and hair loss, however, there are hundreds more that have not yet been properly investigated.

Yu advises, "Our findings of the essential role of miR-22 highlight the importance of determining the combinatorial effects of the microRNA regulatory network in hair cycling."

These new insights into the hair growth cycle and chain of events that lead to premature hair loss in mice constitute an important development that evolves our understanding of the hair loss process. We would assume further in-depth studies of microRNAs will follow as, if the precise reactions and elements involved in causing hair loss can be identified, targeted miR-22 inhibiting treatments can then be developed.

In the meantime, as male and female pattern hair loss are degenerative conditions - so will get progressively worse with age, if left untreated - we would not advise waiting to see what researchers come up with in this respect. It can take many years of clinical trials to formulate safe and effective hair loss treatments, during which time anyone with signs of hereditary hair loss will further decline.

There are currently clinically-proven hair loss treatments available to treat both men and women, as well as a number of hair growth boosters, which have produced encouraging regrowth results in many Belgravia clients. Visit a professional hair loss specialist for more advice and for a bespoke regrowth plan personalised to your specific level of shedding and lifestyle needs.

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The Belgravia Centre

The Belgravia Centre is a world-renowned group of a hair loss clinic in Central London, UK. If you are worried about hair loss you can arrange a free consultation with a hair loss expert or complete our Online Consultation from anywhere in the world for home-use treatment.

View our Hair Loss Success Stories, which includes the world's largest gallery of hair growth photos and demonstrates the level of success that so many of Belgravia's patients achieve.

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