Skin cell gun

Operation

Stem cells from a postage stamp-sized sample of the patient's healthy skin are isolated using an enzymatic tissue processing protocol. The resulting cell suspension is then transferred to a sterile syringe, which is then inserted into the skin gun. Using its unique spray mechanism, the gun uniformly distributes cells directly into the wound. The newly introduced stem cells begin to migrate, multiply, and differentiate, creating new skin tissue in a matter of days.

The entire process – from collecting the skin sample, processing it into a cell suspension, and using the skin gun to spray the stem cells – takes approximately 1.5–2 hours from start to finish. Full re-epithelialization can occur in as little as four days, and after a few months the skin will regain its color and texture.

History

Early experimental versions of the device were developed by Dr. Jörg Gerlach and StemCell Systems GmbH in Berlin, Germany. Dr. Gerlach and SCS had already developed cell culture bioreactors for culturing usable liver and other solid organ tissues from stem cells, and were seeking a similar platform to culture living skin. They soon discovered that, compared to other organs, the skin is a special case. A skin wound is itself an accessible environment that provides excellent conditions to culture new skin tissue in vivo. This solves the problems of wait times and special challenges in transplanting delicate, cultured tissue inherent to in vitro skin culture technologies.

Researchers developed stem cell isolation techniques that maximize stem cell availability for transplantation. To ensure minimal loss in transplanting the isolated cells, engineers at StemCell Systems designed a deposition device, the skin gun, to gently deliver the cell suspension without exposing cells to harsh forces in conventional spray devices.

The skin gun method was first used experimentally at Charité – Universitätsmedizin Berlin on a group of nineteen patients. The clinician in that study determined that the results from the skin gun treatment was so significantly better than traditional grafting that he discontinued performing skin grafts on a control group on the basis of medical ethics.

Subsequently several skin gun procedures have been performed at UPMC Mercy Hospital in Pittsburgh, including patients who have been able to leave hospital within four days of treatment.

Biological basis of wound healing

After an abrasion, cut, burn, or other injury, the body uses several different biological processes to repair the skin. Wound healing generally has three different stages: the inflammatory stage, the proliferative stage and the remodeling stage.

Once the skin is damaged, a series of interrelated events take place in close succession in order to repair the skin. Within minutes after an injury occurs, blood platelets collect at the site of injury to form a clot. This clot limits bleeding at the injury site.

The inflammatory phase involves increased white blood cell activity, removing bacteria and debris from the wound. Biochemical signals instruct regenerative cells to begin dividing, to create new skin tissues much more rapidly than normal.

The proliferative phase is marked by the formation of new skin tissue at the injury site and the general shrinking and eventual disappearance of the wound. New blood vessels are also established during the healing process. The wound is made smaller by myofibroblasts, which hold on to the edges of the wound and slowly get smaller by a system similar to the contraction of muscle cells.

During the remodeling phase, the skin acquires its permanent texture and unneeded cells are disposed of through apoptosis.

Applications

To date skin gun treatment has been used exclusively with second degree burns, though there is strong evidence that the treatment will be successful in treating a variety of skin wounds and skin disorders. Patients with infected wounds or with delay in wound healing are suitable for cell grafting treatment. Third-degree burns, however, completely deprive victims of both their epidermis and dermis skin levels, which exposes the tissue surrounding the muscles. The skin gun has not progressed to the point where it can be used for such advanced wounds, and these patients must seek more traditional treatment methods. The skin gun is generally not used for burn victims with anything less than a second-degree burn either. First degree-burns still maintain portions of the epidermis and can readily heal on their own, thus they do not need this expensive technology.

Currently, the skin gun's applications have not been extended to include the regeneration of skin lost due to other injuries or skin diseases. It is also limited in that it is only effective immediately following the burn incident.

Benefits and side effects

The average healing time for patients with second degree burns is three to four weeks. This is reduced to a matter of days with skin gun treatment.

Traditional skin grafting can be risky, in that chances for infection are relatively high. The skin gun alleviates this concern because the increased speed in which the wound heals directly correlates to the decreased time the wound can be vulnerable to infection. Because of the rapid re-epithelialization associated with skin gun treatment, harmful side effects that can result from an open wound are significantly reduced. Applying the skin cells is quick and doesn't harm the patient because only a thin layer of the patients’ healthy skin is extracted from the body into the aqueous spray. The electronic spray distributes the skin cells uniformly without damaging the skin cells, and patients feel as if they are sprayed with salt water.

Because the skin cells are actually the patient’s own cells, the skin that is regenerated looks more natural than skin grown from traditional methods. During recovery, the skin cells grow into fully functional layers of the skin, including the dermis, epidermis, and blood vessels. The regenerated skin leaves little scarring. The basic idea of optimizing regenerative healing techniques to damaged biological structures demonstrated by the skin gun in the future may also be applied to engineering reconstruction of vital organs, such as the heart and kidneys.

There are major limitations: the method will not work on deep burns that go through bone and muscle, specifically below the dermis. As of 2011, only several dozen patients have been treated; it remains an experimental, not a proven, method. As of 2011, the skin gun was still in its prototyping stage, since it has only treated a dozen patients in Germany and the US, compared to over 50,000 treated with Dermagraft bioengineered skin substitute. There is thus a lack of published peer reviewed clinical evidence, and no knowledge of long-term stability of the newly generated skin.

In popular culture

The skin gun has been featured in numerous books and television shows, including the following examples.