This week, two new studies have been published that open up new avenues for patients with hair loss. The papers describe various methods to regenerate hair in a petri dish before transplantation.
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Study 1 - Growing human hair follicles in the lab
This study from Columbia researchers used methods to create human hair follicles in a petri dish in a lab. The study was published in the latest issue of Nature Communications, titled, “Tissue engineering of human hair follicles using a biomimetic developmental approach.”
The researchers explain that this is the first time that hair follicles have been grown outside of the skin entirely without being implanted over skin.
Dr. Angela Christiano, one of the lead authors of the study explained that rat and mouse hairs have been grown in labs from cultured cells. She said, “Cells from rats and mice grow beautiful hairs. But for reasons we don't totally understand, human cells are resistant.”
Christiano explained that in order to overcome this resistance problem, the team was trying to recreate a 3D environment where the human hair cell could feel at home and would thus regenerate and grow. To achieve this, the researchers created hanging drops of liquid within which there were little spheres of cells.
They noted that some of these cells within the spheres grew into hairs while others did not. In this latest study the team then used 3D printers to create an environment for the hair follicle for its growth and development.
Previous fabrication techniques have been unable to create such thin projections, so this work was greatly facilitated by innovations in 3D printing technology.”
Dr. Erbil Abaci, First Author
As the human skin could be 3D engineered, it could be grown within a mould. Hair follicles were collected from volunteers and placed within deep pits and covered with cells that could produce keratin.
These hair follicle cells were then nourished using JAK inhibitors which has been shown to stimulate hair growth. After three weeks time, the implanted hair follicles started sprouting hair and were growing hair.
The team explained that this method could yield large amounts of new hair follicles which could help people going for robotic hair restoration surgery. This surgery usually requires around 2,000 hair follicles to be taken from the back of the head to be transplanted over the front and top.
What we've shown is that we can basically create a hair farm: a grid of hairs that are patterned correctly and engineered so they can be transplanted back into that same patient's scalp.
That expands the availability of hair restoration to all patients--including the 30 million women in the United States who experience hair thinning and young men whose hairlines are still receding. Hair restoration surgery would no longer be limited by the number of donor hairs.”
Dr. Angela Christiano, Lead Author
People undergoing hair restoration usually need to have a good growth of hair at the back of the head for the procedure. With this new technology, the team explains, this would not be a constraint anymore.
The study was funded by NIH (National Center for Advancing Translational Sciences), National Institute of Arthritis and Musculoskeletal and Skin Diseases, New York State Stem Cell Science among others. Dr. Christiano and Dr. Jahoda, the lead authors of the study are also founders of Rapunzel Bioscience Inc. that works towards regenerative therapies for skin and hair.
Study 2 - Skin cells produce an inhibitor
The second study was performed a team again led by Christiano. The study was published in the latest issue of Cell Stem Cell and is titled, “A Subset of TREM2+ Dermal Macrophages Secretes Oncostatin M to Maintain Hair Follicle Stem Cell Quiescence and Inhibit Hair Growth.”
In this study the team found that a pathway called the JAK-STAT was active within the stem cells of the hair follicles when they were not growing. Activation of this pathway can keep the hair follicle cells dormant and does not allow them to grow, the team noted. When JAK inhibitors were used on mouse skin, these sleeping hair follicles seemed to awaken and began to grow.
The team found that there was an immune cell underneath the skin that could produce a substance called Oncostatin M. This can help keep the hair follicles quiescent, explain the researchers.
Etienne Wang, PhD, first author of the study said, “Rare subsets of immune cells were previously difficult to identify in whole skin, but this work was facilitated by our ability to sequence individual cells and pinpoint the ones making Oncostatin M.”
These cells, Wang said were similar to macrophages. The team named these macrophages “trichophages” because of their association with hair follicles. “Tricho” in Greek means hair.
The researchers noted that if these trichophages were targeted, they could help start off the hair growth cycle.
The flow of the Oncostatin M had to be stopped to allow the hair to grow. This was achieved by using molecule inhibitors and antibodies that could block a specific receptor on the trichophages called the Csf1R. Once this was blocked and Oncostatin M flow was stopped, the hair growth started, wrote the researchers.
Christiano said, “Our previous studies implicated JAK-STAT signaling as one potential new therapeutic pathway for hair loss disorders by targeting hair follicle stem cells with JAK inhibitors. Here, we show that blocking the source of the JAK activating signal outside the hair follicle is another way to target this mechanism.”
"These new pathways may lead to new treatments for both men and women suffering from hair loss, since they appear to be acting independently of male hormone pathways," she added.
This study was funded by the National Skin Center of Singapore, the National Medical Research Council of Singapore, the Locks of Love Foundation, and the National Institutes of Health.