Gene-editing therapy fixes defects in skin cells from boy, 8, with EBS

Therapy inactivates mutated KRT14 gene copy to restore strength of epidermis

Lindsey Shapiro, PhD avatar

by Lindsey Shapiro, PhD |

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A gene-editing therapy to inactivate a harmful mutated copy of the KRT14 gene reversed defects in skin cells taken from a child with epidermolysis bullosa simplex (EBS), according to recent research.

The approach restored the ability of these skin cells, called keratinocytes, to form the structural networks that help give the outer layer of skin its strength.

Such a targeted gene-editing approach may ultimately be safe and beneficial for EBS patients, although more research is still needed, researchers say.

The study, “Allele-specific CRISPR-Cas9 editing of dominant epidermolysis bullosa simplex in human epidermal stem cells,” was published in Molecular Therapy.

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Epidermolysis bullosa simplex leads to fragile skin that easily damages, blisters

The most common type of epidermolysis bullosa, EBS is most often caused by mutations in the KRT5 or KRT14 genes, which encode production of the keratin 5 and keratin 14 proteins, respectively.

These two proteins normally form structural networks, or filaments, that support the strength and structure of the epidermis, or the outer layer of skin. EBS-causing mutations lead to a fragile epidermis that is easily damaged and forms painful blisters.

People inherit two copies of most genes, one from each parent. EBS is typically inherited in an autosomal dominant manner, meaning that only one of these copies, or alleles, needs to be mutated for the disease to be evident.

While the healthy allele still produces normal keratin proteins, the mutated one is dominant, overriding the effects of the healthy protein and preventing normal keratin filaments from forming.

As such, treatment approaches for EBS should seek to prevent the harmful effects of the mutated allele, according to the researchers.

In the study, scientists in Italy described the development of a gene-editing therapy that could accomplish this. It was designed to target a newly identified mutation in the KRT14 gene that they found in an 8-year-old boy with EBS. The identified mutation was predicted to generate a short keratin 14 protein with an altered structure.

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Scientists use CRISPR/Cas9 technology to create gene-editing therapy

Using the Nobel Prize-winning CRISPR/Cas9 technology, the scientists created a gene-editing therapy that would essentially target the mutant allele and inactivate it, meaning it would no longer make the faulty keratin protein.

The idea is that having less overall keratin production, with all of it healthy, is better for cells than having production of some of the healthy version and some of the faulty one.

When delivered to keratinocytes obtained from the EBS patient, the therapy led to efficient and precise editing of the mutant allele while leaving the healthy one alone about 95% of the time.

It did not lead to substantial off-target DNA editing in areas where it wasn’t supposed to act.

In the edited patient cells, production of the faulty version of keratin was nearly entirely prevented, leading to more normal keratin filament networks that were “virtually indistinguishable” from healthy cells, according to the researchers.

The edited cells also regained their strength and were more resilient when faced with cellular stressors.

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Goal is to use therapy to edit epidermal stem cells outside patient’s body

The researchers indicated the ultimate goal of such a therapy would be an ex vivo application, where a person’s epidermal stem cells, or the precursors to mature skin cells, are taken from the body, edited, and then returned to the patient.

Those stem cells would then continuously produce skin cells with healthy keratin filaments, enabling restoration of the epidermis.

Additional experiments indicated the therapy was able to edit this population of long-lived, self-renewing stem cells without any signs of cellular toxicity, “thus maintaining the ability to regenerate a virtually indistinguishable functional epidermis,” the scientists wrote.

“Our study provides a clear demonstration of the efficacy and potential safety of an allele-specific CRISPR-based gene-editing approach, which we envision to further translate into a long-lasting decisive clinical treatment for patients suffering from EBS and possibly other related skin-blistering diseases,” they added.

Future studies will be needed to help determine the optimal dosage of a gene-editing therapy and to further establish that it does not cause off-target effects or toxicity.