Developing effective treatments for genetic lung diseases such as cystic fibrosis has proven challenging. That might not be the case for much longer, with scientists developing a new type of nanoparticle that can carry gene-editing technology directly into the lungs of mice.
With the mapping of the human genome and subsequent genome-wide association studies linking defined genetic mutations with known diseases, the focus of much research has been on developing gene therapies to target the genetic causes of disease.
Messenger RNA (mRNA) is a relatively new therapeutic agent being used to prevent and treat certain genetic diseases. But to function effectively in the body, mRNA – which carries the genetic information that directs cells to make proteins – needs a stable delivery system that protects it from degradation and allows it to enter cells to deliver its gene-altering payload. Nanoparticles have proved effective vehicles for delivering mRNA.
However, the nanoparticle delivery of mRNA has its challenges. Delivering it to the correct body part and avoiding effects on other organs can be tricky. Injected nanoparticles have previously proven effective when they’re encased in a lipid (fatty) sphere that prevents mRNA degradation and improves its cell-targeting ability. Researchers from MIT and the University of Massachusetts Medical School have developed a promising lipid nanoparticle that targets the lungs, where it can deliver gene-altering mRNA.
The researchers developed nanoparticles that comprise a positively charged headgroup, which helps the particles interact with negatively charged mRNA, and a long lipid tail that helps the particles pass through the cell membrane into the cell. They experimented with 72 headgroups and 10 lipid tails with different chemical structures before identifying a nanoparticle structure that could reach the lungs.
Once the effective lipid nanoparticle structure had been found, the researchers tested it on mice. They found they could use the nanoparticles to deliver mRNA encoding CRISPR/Cas9 gene-editing components into the animals’ lungs using a method called intratracheal instillation – introducing a substance directly into the windpipe (trachea) – which allows greater dose control than inhalation.
The delivered CRISPR/Cas 9 components “cut out” a genetically encoded stop signal, turning on a gene for a green fluorescent protein and allowing researchers to determine what percentage of lung cells successfully expressed the mRNA.
The researchers found that after one dose of mRNA, about 40% of lung epithelial cells were transfected. Transfection is the process of introducing genetic material into a cell. Two mRNA doses increased the percentage to more than 50%, and three doses to 60%. Each of the epithelial cells key to treating lung disease – club cells and ciliated cells – were transfected by about 15%.
“This means that the cells we were able to edit are really the cells of interest for lung disease,” said Bowen Li, lead author of the study. “This lipid can enable us to deliver mRNA to the lung much more efficiently than any other delivery system that has been reported so far.”
Using lipid nanoparticles instead of adeno-associated virus (AAV), another vehicle used to deliver gene therapy, provided a distinct advantage. While effective, AAV produces an immune response in the body, so it can’t be used repeatedly on the same person. Lipid nanoparticles don’t produce that immune response, so multiple doses can be given if needed.
The researchers also found that the new nanoparticles broke down quickly and were cleared from the lungs within a few days, thereby reducing the risk of inflammation. Their development could, in future, be used to correct the genetic mutation that causes cystic fibrosis and other genetic lung diseases.
“This is the first demonstration of a highly efficient delivery of RNA to the lungs in mice," said Daniel Anderson, the study’s corresponding author. "We are hopeful that it can be used to treat or repair a range of genetic diseases, including cystic fibrosis."
The research team is working on making the novel nanoparticles more stable so they can be aerosolized and inhaled via a nebulizer, as well as an mRNA vaccine that could be delivered directly into the lungs.
The study was published in the journal Nature Biotechnology.
Source: MIT News
