The breakthrough by a team at Rensselaer Polytechnic Institute (RPI), Troy, New York, marks the first time researchers have used the technology to generate hair follicles, which play an important role in skin healing and function. The team – whose work is detailed in Science Advances – stressed that skin grafts that grow hair are still several years away.
In a statement, study lead Pankaj Karande, Ph.D. said: “Our work is a proof-of-concept that hair follicle structures can be created in a highly precise, reproducible way using 3D-bioprinting. This kind of automated process is needed to make future biomanufacturing of skin possible.
“The reconstruction of hair follicles using human-derived cells has historically been a challenge. Some studies have shown that if these cells are cultured in a three-dimensional environment, they can potentially originate new hair follicles or hair shafts, and our study builds on this work.”
Hair follicles produce sweat, helping regulate body temperature, and they contain stem cells that help skin heal. They are also an entry point for topical drugs and cosmetics, making them an important part of dermatological testing. Currently, initial safety testing is done on engineered skin tissues that lack hair follicles.
“Right now, contemporary skin models - the engineered structures that mimic human skin - are quite simple. Increasing their complexity by adding hair follicles would give us even more information about how skin interacts with topical products,” said Carolina Catarino, Ph.D., first author of the study.
The researchers created their follicle-bearing skin with 3D-printing techniques adapted for printing at the cellular level.
According to RPI, the scientists began by allowing samples of skin and follicle cells to divide and multiply in the lab until there are enough printable cells.
The researchers then mixed each type of cell with proteins and other materials to create the bio-ink used by the printer. Using an extremely thin needle to deposit the bio-ink, the printer built the skin layer by layer, while also creating channels for depositing the hair cells. Over time, the skin cells migrated to these channels surrounding the hair cells, mirroring the follicle structures present in real skin.
These tissues have a lifespan of two to three weeks, which is not enough time for hair shafts to develop. The research team’s future work aims to extend that period, allowing the hair follicle to mature further and paving the way for their use in drug testing and skin grafts.