3D-Printed Skin Closes Wounds for More Natural-Looking Reconstructive Surgery Outcomes

Reconstructive surgery for injuries or diseases affecting the face or head is often imperfect and usually leads to scarring or permanent hair loss. Now, researchers who harnessed fat cells and supporting structures from clinically procured human tissue to precisely correct injuries in rats have found that fat tissue holds the key to 3D printing layered living skin and potentially hair follicles. The discovery holds significant potential for facial reconstructive surgery and hair growth treatments in humans.

Scientists at Penn State (University Park, PA, USA) have pioneered a technique for intraoperatively printing a complete, live system of multiple skin layers, including the deepest layer, known as the hypodermis. "Intraoperatively" implies the capability to print this tissue during surgery, suggesting a more immediate and integrated method of repairing damaged skin. Notably, while the top visible skin layer, the epidermis, naturally forms with support from the middle layer and does not require printing, the hypodermis is crucial as it is composed of connective tissue and fat, offering essential structure and support over the skull.

The research began with human adipose, or fat, tissue sourced from patients undergoing surgery. From this, the team extracted the extracellular matrix – the intricate network of molecules and proteins providing tissue structure – to formulate a component of their bioink. Another bioink component was created using stem cells derived from the adipose tissue. These cells possess the unique potential to evolve into various cell types, given the right environment. The bioprinter used in their research had three compartments: one each for the matrix-fibrinogen mixture, the stem cells, and a clotting solution that aids in binding the other components to the injury site. This three-compartment system allowed precise co-printing of the matrix-fibrinogen mixture.

The team printed directly into the injury site with the target of forming the hypodermis which aids in wound healing, hair follicle generation, temperature control, and more. They successfully created both the hypodermis and dermis layers, with the epidermis naturally forming on its own within two weeks. Moreover, the researchers observed the formation of downgrowths in the hypodermis, signaling the initial stages of early hair follicle development. While fat cells themselves do not directly compose the cellular structure of hair follicles, they play a significant role in follicular regulation and maintenance. This ability to precisely cultivate hair at sites of injury or disease could greatly influence the naturalness of reconstructive surgery outcomes.

“With this work, we demonstrate bioprinted, full thickness skin with the potential to grow hair in rats. That’s a step closer to being able to achieve more natural-looking and aesthetically pleasing head and face reconstruction in humans,” said Ibrahim T. Ozbolat, professor of engineering science and mechanics, of biomedical engineering and of neurosurgery at Penn State, who led the international collaboration that conducted the work. “We believe this could be applied in dermatology, hair transplants, and plastic and reconstructive surgeries — it could result in a far more aesthetic outcome. With the fully automated bioprinting ability and compatible materials at the clinical grade, this technology may have a significant impact on the clinical translation of precisely reconstructed skin.”

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