Is It Possible to Regrow Hair? A Look at Recent Research on Hair Regeneration

Cultures all over the globe place a high value on having a full and healthy head of hair. Although hair is no longer needed to function as a protective barrier, as it was in our evolutionary history, many people — especially men — have valid concerns about losing their hair, ranging from cosmetic to psychological. 

If you’ve noticed a newly receding hairline or a previously thick mane seeming thinner than before, you may be curious as to why hair loss occurs and if there’s anything you can do about it. 

Researchers have been studying baldness and hair loss for decades; from over-the-counter medications to topical creams to hair transplant surgeries, nothing has “cured” baldness yet. However, new treatments for hair regeneration are on the horizon.

In this article, learn more about the basics of hair growth, what causes baldness, and the results from a recent study that led to successful hair regrowth in mice using the microRNA found in dermal exosomes. 

The Basics of Hair Growth 

Hair follicles are embedded in the skin; each one produces a hair shaft and has five components. At the bottom of the follicle is the dermal papilla, followed by the matrix, outer root sheath, inner root sheath, and the hair shaft, which is the visible portion of a strand of hair. A healthy head of hair will contain between 250,000 to 500,000 hair follicles. 

The hair growth cycle has three stages: anagen, catagen, and telogen. Anagen is the active growth phase, which lasts four years on average for scalp hair. The shorter catagen phase lasts a few weeks and begins to shut down hair growth. Finally, the telogen phase is when hair growth is entirely at rest, causing the hair to fall out.

Hair Loss: What Causes Baldness? 

The most common form of baldness is androgenetic alopecia (AA). Although AA can affect both sexes, AA is commonly referred to as male pattern baldness. While males tend to lose hair on the top and front of their heads, females typically see a thinning of the hair around the crown rather than a receding hairline. 

The primary causes of baldness are genetics or family history, lifestyle factors, medications, and stress, which impacts hair loss similarly to graying hair. In women, menopause is a leading cause of hair loss. 

Androgenetic alopecia causes 95% of hair loss cases in men. As described in its name, androgen hormones are to blame for this type of hair loss. Androgens are crucial for male sexual development and reproduction, with the primary hormones being testosterone and androstenedione. 

Men with AA tend to have lower testosterone levels and higher levels of a byproduct of testosterone called dihydrotestosterone (DHT). 

In people genetically susceptible to baldness, DHT is responsible for the shrinking of hair follicles, which shortens the hair’s lifespan and eventually halts hair growth.

Specifically, DHT affects the dermal papilla cells, which contain highly specialized fibroblast cells that regulate hair growth.  When DHT levels are too high in these susceptible individuals, the anagen phase shortens, and the hair will fall out earlier.

Recent research is targeting the replenishment of dermal papilla cells at these shrunken hair follicles sites to regenerate hair growth. 

Using Exosomal MicroRNA for Hair Regrowth: Study Results 

Published in Science Advances in July 2020, researchers based out of North Carolina State University successfully used exosomal microRNA and 3D-cultured spheroid cells to regenerate hair growth in mice. Let’s take a look at these two experiments.

First, the researchers cultured dermal papilla cells alone in both a 2D model and a 3D spheroid model. The spheroid model is a structure that replicates a cell’s natural environment. 

They then treated mice with one of three therapies: the 2D-cultured dermal papilla cells, the 3D-cultured dermal papilla cells within a keratin scaffolding, or minoxidil (also known commercially as Rogaine). Although topical products like minoxidil do work for some individuals, the results are temporary and require constant reapplication. 

The results from this first experiment were striking: after 15 days, mice treated with the 3D-cultured spheroid dermal papilla cells regained 90% of lost hair. 

They found that the 3D dermal papilla spheroids progressed the hair cycle from the telogen phase to the anagen phase significantly more than the groups treated with 2D cultured cells or minoxidil. This progression from telogen to anagen indicates the growth of new hairs.  

The researchers believe that the combination of the spheroid structure and the keratin scaffolding works best for hair regrowth. These two aspects recreate the hair follicle’s microenvironments and “anchor” the hair in place, respectively.

For the second experiment, they tested another method of hair regrowth using exosomal microRNA. Exosomes are small extracellular vesicles that contain microRNA and act as messengers between cells. MicroRNAs are tiny molecules involved in gene expression and regulation. 

 The researchers measured exosomal microRNA from 2D and 3D dermal papilla cell exosomes.  The microRNA miR-218-5p was highly expressed in the 3D dermal papilla exosomes. Further experiments found that increasing miR-218-5p led to hair follicle growth, whereas inhibiting this microRNA led to follicle dysfunction. 

The 3D spheroid cells with higher expression of the microRNA miR-218-5p also had increased β-catenin and reduced SFRP2 levels, which are indicative of hair follicle growth and maintenance of the anagen phase. 

The researchers indicate that treatment with 3D cell therapy could treat baldness; however, this therapy is challenging and not very accessible due to the necessity of surgical injection. Preferably, microRNAs could easily be added to creams, lotions, or microneedle patches, reducing the invasiveness of surgical cell therapy and making microRNA a promising candidate for hair regrowth treatments. 

Key Takeaway: 

• Dermal exosomes containing the microRNA miR-218-5p could potentially be a new candidate for hair regrowth creams or microneedle patches. 
• This method would be non-invasive and non-repetitive, unlike the surgical hair regeneration methods and topical minoxidil creams, respectively. 
• In this study, mice treated with 3D-cultured spheroid dermal papilla cells with high expression of miR-218-5p led to hair follicle growth and regeneration of 90% of lost hair. However, 3D cell therapy is a more challenging and invasive procedure.

References:

Driskell RR, Clavel C, Rendl M, Watt FM. Hair follicle dermal papilla cells at a glance. J Cell Sci. 2011;124(Pt 8):1179-1182. doi:10.1242/jcs.082446

Hu S, Li Z, Lutz H, et al. Dermal exosomes containing miR-218-5p promote hair regeneration by regulating β-catenin signaling. Sci Adv. 2020;6(30):eaba1685. Published 2020 Jul 24. doi:10.1126/sciadv.aba1685

Santos Z, Avci P, Hamblin MR. Drug discovery for alopecia: gone today, hair tomorrow. Expert Opin Drug Discov. 2015;10(3):269-292. doi:10.1517/17460441.2015.1009892