Fish skins help tissue repair

Materials World magazine
1 Jul 2019

Cod fish skin grafts are proven to accelerate the healing of wounds and burns. Ceri Jones examines how they support cell regrowth.

Cod fish skin has proven to assist tissue repair and is rapidly shifting from innovative to mainstream medical care. Following its successful use treating a severe pet injury, a veterinary team presented its findings at the Society of Veterinary Soft Tissue Surgery convention, held in June 2019, to argue for wider use of cod skin in skin cell therapies.

On 13 February 2019, a one year old puppy called Stella was caught in a house fire in Michigan, USA, and suffered second and third-degree burns over 10% of her body. Stella was rushed to Michigan State University (MSU) Veterinary Medical Center where the team deemed it too risky to attempt surgery under anaesthesia due to lung damage from smoke inhalation, so decided to apply cod fish skin grafts to her body.

MSU Veterinarian and Surgical Resident, Brea Sandness, said, ‘We were able to place them on her with minimal sedation, which not only allowed us to heal her without additional stress to her lungs, but improved the way her burns healed.’

Fish skins are a traditional treatment for burns in Brazil, which was adopted in the USA following the California wildfires. Many wild animals were caught in the blaze and vets stitched tilapia skins to the injuries of two bears and a cougar, as the sterilised skins degrade naturally and would be safe if eaten.

Unlike tilapia, which acts as a natural wound dressing, coldwater fish skins actively support and encourage tissue healing. ‘Descaled grafts have been shown to stimulate the production of cells and become functional, living tissue. In Stella’s case, these grafts, which can be changed as often as the burn requires, were absorbed by her body as new tissue grew into the graft,’ MSU said.

Over several weeks, Stella recovered and MSU attributed the extent and speed of this in part to the application of the cod skin grafts.

Skin deep

Cod skin grafts are currently being used in cell regeneration for animals and humans. Central to tissue healing are the similarities – and differences – between mammalian and fish skin, according to medical research company and graft supplier Kerecis.

The USA-Icelandic firm said Atlantic cod is an ideal match as it is so far removed from mammalian skin that it cannot transfer viruses, pathogens or diseases, but the structure is near enough that it provides a support system for regeneration and minimises rejection.

Further, proteins, sterols, fat-soluble vitamins, phospholipids and high levels of Omega 3 polyunsaturated fatty acids support natural healing.

‘Fish skin has an appropriate surface chemistry and microstructures that facilitate cellular attachment, competent mechanical strength and biodegradation rate without undesirable byproducts,’ Kerecis said.

‘These favourable effects are in large part mediated by the Omega 3 (n-3) fatty acids, eicosapentaenoic acid and docosahexaenoic acid, which are found in high concentration in fish oil. One reason why wounds fail to heal is the shortage of lipids that are formed in the Golgi apparatus of the keratinocytes.’

Thermal damage affects multiple layers of skin, causing loss of lipids and therefore moisture, causing skin to contract and scar. Any graft needs to be a barrier against infection, a porous membrane to facilitate cell life, and an active repairer.

Existing grafts made from human, tilapia, pig or cow skin require harsh chemical antiviral processing. They retain collagen but are stripped of the necessary lipids that support tissue repair, making them thin and less effective. As cod skin cannot transfer disease, it doesn’t need to undergo such harsh preparation, so once descaled and sterilised, it retains its thickness and the microstructure layers that support cell regeneration, heat and moisture control. The skin is anti-microbial and non-allergenic by its nature. In addition to healing, cod skin is thought to help alleviate pain to a degree.

Cod skin has a microporous scaffold structure that reduces the myelofibroblast activity that can lead to the development of fibrin, fibrosis and even cirrhosis. Research shows that when covered in cod skin, cells gradually migrate into the scaffold structure to rebuild dermal layers and build vascularisation.

Also, animal in vitro studies on burns suggested that cod skin was able to protect against S. aureus bacteria for 10 hours longer than a human graft.

What lies beneath

Once the gauze-like graft is applied to the skin, it is hydrated and then cannot be removed, as new tissue starts to build up through it, unlike with a dressing. The process is not as invasive as conventional skin grafting or flap coverage techniques, and is claimed to be cheaper due to the lesser degree of processing and reduced need for grafting surgery. Plus, using fish resolves any cultural issues that arise from using donor tissue from humans, pigs or cows.

Kerecis is currently exploring the use of cod skin products in treating diabetic and non-critical wounds, for internal surgery and brain and spinal dura protection, as well as trialling the effectiveness of unprocessed fish skin.