A team led by scientists at Rensselaer Polytechnic Institute has 3D printed hair follicles in human skin tissue cultured in the lab. This marks the first time researchers have used the technology to generate hair follicles, which play an important role in skin healing and function.

“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,” said Associate Professor and Study Lead Pankaj Karande, Ph.D.

“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,” Karande said.

“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 First Author Carolina Catarino, Ph.D.

The researchers created their follicle-bearing skin with 3D-printing techniques adapted for printing at the cellular level.

The scientists begin by allowing samples of skin and follicle cells to divide and multiply in the lab until there are enough printable cells. Next, the researchers mix 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 builds the skin layer by layer, while also creating channels for depositing the hair cells. Over time, the skin cells migrate to these channels surrounding the hair cells, mirroring the follicle structures present in real skin.

As of now, 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.

Here is an exclusive Tech Briefs interview — edited for length and clarity — with Catarino.

Tech Briefs: I’m certain there were way too many to count, but what was the biggest technical challenge you faced while developing this 3D-printed hair follicle method?

Catarino: The reconstruction of hair follicles using human-derived cells has proven challenging due to the loss of their stem-cell-like characteristics and functional abilities once isolated from their natural environment. In the absence of this physiological context, these cells struggle to generate new hair follicles. Research indicates that culturing these cells in a three-dimensional environment can partially restore their capacity, potentially leading to the formation of new hair follicles or hair shafts. Overcoming this inherent biological challenge in skin model reconstruction with hair follicles prompted our innovative approach: leveraging bioprinting technology to recreate the three-dimensional environment, facilitating the recovery of cell inductive capacity.

Technically, the primary obstacle in realizing this project lay in integrating various cell types into specific bio-inks and harmonizing hardware and software to construct a functional human tissue. The intricate coordination of these elements marked the most significant technical challenge we faced, emphasizing the complexity of our pursuit to advance the field of hair follicle regeneration.

Tech Briefs: How long does the entire process take? Can you explain in simple terms how it works?

Catarino: To produce the bioprinted skin sample, the initial step involves designing bio-inks composed of biomaterials such as proteins and cells. We source these cells from discarded skin samples obtained with patient consent, either isolating them in-house or purchasing them commercially. The isolation process takes approximately two weeks, after which the cells undergo a cultivation and expansion phase in the laboratory lasting 1-4 weeks to increase their quantity. Subsequently, the cells are combined with proteins and other biomaterials to formulate the bio-inks.

The bio-inks are then loaded into the bioprinting equipment, and a pre-programmed algorithm guides the deposition of each material, creating a three-dimensional tissue. The printing process commences with the deposition of the bottommost layer (dermis) primarily consisting of collagen I and dermal cells. Once the dermis gels, we proceed to print the hair follicles and the external layer of the skin (epidermis). This entire printing process for 12 samples (each about an inch in diameter) typically takes around one hour.

Post-printing, the samples are incubated in a controlled environment with regular media changes, maintaining optimal temperature and CO2 levels. This incubation period, lasting approximately two weeks, allows the tissue to mature to its final stage. After this period, the bioprinted skin samples are ready for in vitro evaluations of substances, marking a crucial step forward in the development of advanced tissue engineering techniques for various applications.

Tech Briefs: The research article says, “Right now, 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.” How is that coming along? Any updates you can share?

Catarino: We are actively engaged in refining our printing protocol and enhancing the media composition to enable an extended culture period for these samples. Our goal is to optimize the conditions to promote sustained growth and maturation. Stay tuned for forthcoming updates as we aim to share our progress and findings through publications in the near future.

Tech Briefs: Going from that, what are your next steps?

Catarino: In addition to extending the culture period to facilitate hair fiber formation, our next steps involve a comprehensive characterization of the models and their functionality, particularly in the context of drug and cosmetics testing. We are also actively exploring strategies to enhance the complexity of our model by incorporating additional structures, such as sebaceous glands and vasculature. These advancements aim to create a more physiologically relevant and intricate system, further expanding the potential applications of our bio-printed skin models.

Tech Briefs: Do you have any advice for engineers aiming to bring their ideas to fruition?

Catarino: For engineers aspiring to bring their ideas to fruition, dedicating ample time to grasp the fundamentals of the science involved and thoroughly researching existing developments in similar concepts is essential. This groundwork lays the foundation for crafting a clear and strategic pathway from idea to project. Importantly, be prepared for setbacks and failures; view each attempt as a valuable learning opportunity. The iterative process of trying, failing, and learning is integral to innovation and eventual success. Embrace challenges with resilience and persistence, knowing that each experience contributes to refining and advancing your ideas.

Tech Briefs: Anything else you’d like to add?

Catarino: It is tempting to think that we have now been able to develop a solution for hair restoration. Translation of our proof-of-concept studies to demonstrating that we can form fully grown hair in human skin will require additional research and optimization. Not to mention regulatory considerations in translating this research to human patients. Our studies have made important contributions but there is still a lot of work ahead!