CRISPR-carrying lipid nanoparticles enabled researchers to correct a rare nonsense mutation in the lungs of a cystic fibrosis mouse model.
From its first description in 1935 until now, clinical outcomes for patients with cystic fibrosis have undergone a dramatic transformation. While the rare genetic disease was once an early death sentence that often prevented patients from reaching adulthood, advancements in cystic fibrosis therapeutics have greatly extended the lifespans of those suffering from the disease over the years. However, these therapies are not effective in all patients.
In a study published in Nature Communications, scientists reported a novel strategy to deliver the CRISPR-Cas9 gene-editing system into the lungs of a cystic fibrosis mouse model and correct the underlying mutations. Once developed and tested, this approach could allow clinicians to treat every patient with cystic fibrosis, including those who were previously untreatable. Cystic fibrosis results from mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes a chloride channel on the cell surface that helps control the concentration of salt and water within bodily secretions. Impaired or absent CFTR activity leads to the characteristic thick and sticky mucus associated with the disease and consequently, an increase in the frequency of respiratory infections. Clinicians have developed small molecule drugs, such as Trikafta, that effectively treat 90 percent of patients.
“The problem is that these drugs are only for symptom management,” said Yehui Sun, a graduate student in Daniel Siegwart’s laboratory at the University of Texas Southwestern Medical Center and author of this study. “[These drugs cannot] cure the root of the disease because it is a genetic disease.” The patient’s cells must produce the CFTR protein for the existing therapies to work, which leaves patients with nonsense mutations without options.
Since its initial discovery, researchers believed that they could use CRISPR-Cas9 to help cure genetic diseases. However, the lack of effective delivery carriers that could target specific organs held back this approach. To solve this problem, Siegwart and his team previously developed an advanced delivery strategy called selective organ targeting lipid nanoparticles (SORT LNP). By modifying the composition and biophysical properties of these nanoparticles, the researchers selectively targeted cells in the lungs, livers, or brains of mice after intravenous administration. Building on this work, Sun, Siegwart, and their team further optimized the formulation of their lung SORT LNP and improved its delivery, efficacy, and lung-targeting specificity, while producing minimum toxicity. After encapsulating the CRISPR system components including Cas9 mRNA, mutation-specific single guide RNA, and donor single stranded DNA template, they injected the lipid nanoparticles intravenously into a cystic fibrosis mouse model harboring the nonsense mutation, G542X. Through next-generation sequencing (NGS) of DNA extracted from its lung tissue, the researchers determined that their gene editing strategy successfully corrected the G542X mutation in murine lungs.
By Charlene Lancaster, PhD
Article can be accessed on: The Scientist