Can Printed 'Skin' Heal Burns and Prevent Scars?
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Cells suspended in a water-based gel make up the “ink” in this 3D printer.<br>Wake Forest Institute for Regenerative Medicine
A hand touches a scalding hot plate, sharp pain erupts and, immediately, the body gets to work. Damaged cells send out distress signals; immune cells rush in. As inflammation subsides, a coordinated repair process begins. Eventually, collagen fibers aligned in tight parallel rows will replace much of the damaged tissue. The wound heals, but it does not resemble normal skin.
For a small burn or cut, a scar is a small price to pay for rapid healing that mitigates the risk of infection. But in larger burn wounds, scarring can be devastating.
Each year, 11 million people require hospital care for burns. Long after the wounds have healed, scarring can cause complications. Unlike normal skin’s random, basket-weave pattern, which makes it flexible and resilient, scar tissue tightens as it heals and, once mature, grows more slowly than surrounding skin. This can hinder movement and, in children with extensive burns, interfere with normal growth and development. Severe scars often lack hair follicles, sweat glands and nerve endings, reducing the ability to experience touch and to regulate body temperature.
Quick fact: Scientists are using nanomaterials to treat slow-healing wounds on burn victims
Scientists have tested special nanomaterials on pigs and mice that, when activated by light, produce toxic molecules that kill bacteria in infected lesions, with little damage to the surrounding tissue. The experiments provide hope for people with chonic wounds that resist antibiotic treatment.
Scientists have long tried to develop ways to nudge the body to build healthy tissue instead of defaulting to emergency repair. In recent years, 3D bioprinting technology has emerged as one of the most promising approaches. By depositing patients’ own, precultured skin cells suspended in an inklike gel, these printers can create personalized skin substitutes, kick-starting the regeneration process. Although it is early days, the technology is coming closer to clinical reality.
The key is accessing the body’s ability to rebuild, says wound healing researcher Johan Junker of Linköping University in Sweden. Our bodies, he says, “have been practicing this for millions of years, and we do it constantly, because our skin and every tissue in our body, more or less, always turns over. So why not just provide as good a set of building blocks as we can and then let nature do its thing?”
Inks made of cells
For nearly a century, the gold standard for closing severe burn wounds has been split-thickness skin grafts. Surgeons remove the outermost layer of skin, the epidermis, and a sliver of the underlayer, the dermis, from an unburned part of the patient’s body and use it to cover the wound.
But in cases of extensive burns, there may not always be enough healthy skin to graft. And although this approach improves healing and aesthetics, it doesn’t eliminate scarring, because much of the skin’s functionality resides in the dermis, which has been replaced only in part. (Harvesting skin from other parts of the body can introduce scarring there, too.)
Personalized skin substitutes created using traditional culture methods—multiplying cells in a lab dish, then layering them into a premade gel scaffold—have recently shown that scarless healing is possible: A product called denovoSkin, which replaces the dermis as well as the epidermis, has been used to treat children with severe burns in compassionate use cases. However, this approach requires special laboratory facilities and takes several weeks, which matters because the longer a wound remains open, the worse the risk of scarring. And the more severe the wound, the harder it is to build a viable three-dimensional skin substitute.
Bioprinting offers a way around some of these challenges, and a variety of research groups are working to find an optimal formula for the “ink” of such printable skin.
The severe wounds such technologies could treat are an overlooked health burden, says Hafiza Parkar, a regenerative medicine researcher at the University of Pretoria in South Africa, who is developing a 3D bioprinted skin substitute. Wound healing affects every single part of medicine, Parkar says, and the burden falls hardest on low- and middle-income countries.
In Sweden, Junker, with colleague materials scientist Daniel Aili and others, recently designed a bioink that could improve healing, which has been dubbed “skin in a syringe.” They began with fibroblasts—the main cells of the dermis—collected from abdominal skin from tummy-tuck procedures, and then grew the cells on porous gelatin beads in a bioreactor. Fibroblasts produce proteins that form the skin’s scaffolding and release growth factors that dampen inflammation, helping...