Sandpaper-like shark skin is unique and may have medical uses for human wounds and burns - study

Plastic surgeons, dermatologists, and burn specialists in various parts of the world have for a few years been using the skin of various fish – including tilapia – to treat burns and wounds as a temporary covering for the skin of dogs and even humans. The skin prevents the loss of moisture and proteins from the wound and stays bonded to it until the skin heals. Tilapia is popular among Ashkenazi Jews, who make gefilte fish from it.

The process of covering wounds and burns helps the wound to recover faster and protects it from contamination. The fish skin is also rich in collagen to repair the skin without having to use gauze bandages that have to be replaced daily and painfully. The base layer uses small pores to promote vascularization – the formation of new blood vessels and dermal tissue, helping the dermal (intermediary) layer to heal at the same time as the epithelial (outer) layer, and reducing healing time and providing better outcomes.

Sharks differ from other fish in their amazing ability to heal from wounds, according to reports of sharks recovering from injuries sustained in the wild. While this healing ability has not yet been documented in controlled laboratory conditions, some of the chemical compounds found in shark skin may have significant biomedical potential.

To investigate this possibility, two dermatology researchers from the famed Karolinska Institute in Sweden studied a small shark called the spiny dogfish (Squalus acanthias) and other cartilaginous fish species at the Marine Biological Laboratory (MBL) in Woods Hole, Chicago.

Theirs was the first study that comprehensively examined the mucus layer of two shark and one skate species. Their goal was to understand the unique biochemistry of the skin of such animals. Previous research on sharks in other labs has led to the development of a new antibiotic and the discovery of biochemical pathways relevant to cystic fibrosis research.

Jakob Wikström, associate professor of dermatology and principal investigator at Karolinska, and Etty Bachar-Wikström, senior researcher and this study’s principal investigator, studied the skin mucus of two species of sharks at MBL along with their close relatives called little skates. Unlike most fish species that have relatively smooth skin protected by a thick, slimy layer of mucus, sharks have rough skin that feels like sandpaper. It wasn’t obvious whether this skin had a protective mucus layer at all.

They just published their results in the International Journal of Molecular Sciences under the title “Identification of Novel Glycans in the Mucus Layer of Shark and Skate Skin.” 

Still an obscure animal

“For obvious reasons, much more is known about fish biology than shark biology,” Wikström said. “Fish are easier to handle, and there's a bigger commercial interest in them.” Sharks are also fish, of course, but 99% of fish are bony species (Osteichthyes), unlike the cartilaginous sharks and skates (Chondrichthyes), he explained. 

They found a very thin mucus layer on shark skin that is chemically different from that of bony fish. The shark mucus is less acidic, almost neutral, and turns out to be more chemically similar to some mammalian mucus, including some human mucus, than to bony-fish mucus, she said.

It's more evidence that “the molecular biology of sharks is unique,” Wikström said.