Growing back the hair -- Bioengineered organ replacement therapy

Organ replacement regenerative therapy is one of the intensely studied areas in medical science. It promises the possibility of replacing organs that are damaged by disease, injury, and aging. Rather than transplanting an organ from another donor into a patient, researchers are investigating the ability of patient’s cells to be modified (or bioengineered) to grow into a specific organ. One application for bioengineered organ replacement therapy is the treatment of balding – by growing back the hair.

Nude mouse with human hair growing on its back.

Current treatment options for balding include medications that stimulate hair follicles into growing hair or reduce certain hormones associated with balding. However, continuous use of these medications is required and, even then, results are not always successful. Another option is transplant of healthy hair follicles from area of the head that is not balding, but the number of possible transplants is limited to the number of healthy hair follicles available.

Hair organ regeneration is challenging for several reasons. Hair follicles are complex; they are made up of various cell types, each responsible for different tasks, such as hair elongation, pigmentation, connection with surrounding tissues, and growth cycles. Also, it is difficult for implanted cells to grow into hair with correct structures without being stuck under the skin. After implanted cells grow into proper hair follicles, they need to form connections with surrounding tissues, such as muscles and nerves, in order to function properly. Finally, regenerated hair must maintain proper hair growth cycles.

A team of researchers in Japan has gotten one step ahead in the quest for hair organ regeneration. For the first time, they were able to regenerate hair follicles using human cells. The researchers took scalp skin cells from balding males and turned them into hair follicles that can grow hair. The bioengineered hair follicle cells were implanted into the back of nude mice, and hair shafts successfully appeared on the mice after 2-3 weeks. Importantly, the hair follicles developed into a correct structure, could achieve high density (~120 hair shafts per cm²), formed proper connections with the surrounding tissues, and had restored hair growth cycles.

Diagram of a hair follicle in a cross section of skin layers

Of course the study does not promise immediate application of the therapy, and more challenges must be met in the future studies. The approach must show that hair follicles can be regenerated in much larger area, such as a human scalp. Also, improvement to the success rate must be achieved; in the study, some regenerated hair follicles had abnormal shapes or had no pigments, i.e. produced white hair. Lastly, the method must be proven effective in humans. Unfortunately, the authors in the study do not mention how much time is expected for the hair organ regeneration to become a real treatment option, and we must wait till further progress is reported.

Thank you for reading the post. See you next week!

References:
Fully functional hair follicle regeneration through the rearrangement of stem cells and their niches

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