Researchers at the Keck School of Medicine of USC, along with colleagues from across the country, have genetically engineered mouse cells to produce a type of human collagen - type VII - that is missing in a family of inherited skin diseases known as dystrophic epidermolysis bullosa.

The researchers also prompted the mouse cells to create the structural fibers that normally arise from type VII collagen. Their work was published in the December issue of Nature Genetics.

“This is the first demonstration of in-vivo gene therapy where the genes have made a large extracellular molecular structure that you can actually see with a microscope,” said David Woodley, chief of dermatology at the Keck School and the study’s principal investigator.

Scientists from Shriners Hospital for Children in Portland, Ore., Northwestern University in Chicago and Xgene Corp. in San Carlos, Calif., also participated.

Woodley was helped by his previous efforts in the field: In 1992, he and his colleagues became the first team to clone the human gene for type VII collagen, one of the key components of the skin’s extracellular matrix.

Collagen makes up the tendrils and fibrils that provide a cushion for the skin’s cells to rest upon; type VII collagen, in particular, is critical to the creation of the skin’s so-called anchoring fibrils.

“Anchoring fibrils,” Woodley said, “are like connective tissue staples - they staple the epidermal layer of the skin to the dermis.” Without these fibrils, the layers of the skin can separate like layers of pastry, blistering and sloughing off at the slightest insult or injury.

That is why people without type VII collagen develop dystrophic epidermolysis bullosa, in which blisters form all over the body, leaving behind permanent scars.

“By the time people with epidermolysis bullosa are 20,” said Woodley, “they often have developed very aggressive squamous cell carcinomas.”

Ever since their successful cloning of the type VII collagen gene, Woodley and Keck School associate professors of research Mei Chen and Wei Li, with gene therapy expert Nori Kasahara of USC’s Institute for Genetic Medicine, have been working to insert that gene into cells that are missing it.

The team has been able to get the collagen gene into both fibroblasts (the cells that normally produce collagen and other fibrous tissues) and keratinocytes (the cells that normally differentiate to form the outmost layer of skin).

In the Nature Genetics article, the researchers have shown that these cells are capable of expressing type VII collagen and constructing anchoring fibrils in a mouse model.

Producing anchoring fibril structures in an animal, noted Chen, who is the first author on the paper, is a major step forward toward the use of gene therapy to actually treat patients with epidermolysis bullosa.

In subsequent work, Woodley said, the engineered cells have shown that they are capable of continuing to pump out type VII collagen for at least six months - but so far, they have only done so in lab dishes.

The question is whether they will be able to do the same in mice - and, eventually, in humans.

“I see patients all the time who would definitely benefit from our better understanding of the basic mechanisms of skin biology,” Woodley said. “That’s the goal: to help the patients who need it. Hopefully, that’s what we’re doing.”

The research published in the Nature Genetics article was supported by grants from the National Institutes of Health.

Contact Lori Oliwenstein at (323) 442-2827.