Editing Genes Inside the Body

In recent months we’ve reported on several studies using CRISPR technology to treat disease. Although the technique has only been around for about five years, dozens of trials in humans have already been proposed. Most of these involve removing cells from the patient, editing their DNA and reintroducing them into the body. Now researchers are working on ways to edit the DNA without having to remove the cells at all.

Editing genes with CRISPR requires two elements: a protein that cuts the DNA to disable the faulty gene and a fragment of RNA that informs that protein where to make the cut. But proteins and RNAs are large molecules that do not enter cells readily. So researchers are investigating different ways to deliver the CRISPR components to tissues inside the body.

One method utilizes fatty particles to target diseases of the liver. In one study on mice, the company reported successfully disabling a gene involved in a rare genetic disease with a high degree of efficiency and no ill effects. Another company is using gold nanoparticles to carry the CRISPR components into muscle to treat debilitating muscular dystrophy. Although the method was only effective in 5 percent of the cells, it was successful at improving muscle strength in mice, and repeated injections could produce further improvement over time.

A third research team has built on the muscular dystrophy study by using a virus to more effectively deliver the CRISPR genes throughout the body. But this carries a risk that the CRISPR gene could linger in the system, causing unwanted effects. So, yet another team is looking at ways to develop a “kamikaze” CRISPR system that automatically disables after a set period of time. They have tested the system on Huntington’s disease in mice, successfully disabling the gene with 65 percent efficiency.

With advances being made daily, gene editing will likely be used to target many more diseases in the not-too-distant future.