MIT engineers in collaboration with the Massachusetts School of Medicine figured out how to transport messenger RNA using nanoparticles
Engineers at MIT and the University of Massachusetts School of Medicine have designed a new type of nanoparticle that can be introduced into the lungs, where it can release messenger RNA that codes for useful proteins. The researchers say that, with further development, these particles could offer an inhalable treatment for cystic fibrosis and other lung diseases. The study was published in Nature Biotechnology.
‘This is the first demonstration of highly efficient transport of RNA to the lungs in mice. We hope it can be used to treat or repair a number of genetic diseases, including cystic fibrosis,” says Daniel Anderson, a professor in MIT’s Department of Chemical Engineering and a member of the Koch Institute for Integrative Cancer Research and the Institute for Medical Engineering and Sciences. IMES). ) from MIT.
In a mouse study, Anderson and his colleagues used the particles to provide the mRNA that encodes the machinery needed for editing the CRISPR/Cas9 gene. This could open the door to the design of therapeutic nanoparticles capable of eliminating and replacing pathogenic genes.
Lungs in the spotlight
Messenger RNA has great therapeutic potential to treat various diseases caused by defective genes. Until now, an obstacle to its implantation was the difficulty of delivering it to the correct part of the body without unwanted effects. Injected nanoparticles tend to accumulate in the liver, so several clinical trials are already underway evaluating potential mRNA treatments for liver disease. RNA-based Covid-19 vaccines, which are injected directly into muscle tissue, have also been shown to be effective. In many of these cases, the mRNA is encapsulated in a lipid nanoparticle, a fatty sphere that protects the mRNA from premature breakage and helps it get into target cells.
Several years ago, Anderson’s lab began designing particles that could better transfect the epithelial cells that make up most of the lining of the lungs. In 2019, his lab created nanoparticles that could deliver mRNA that codes for a bioluminescent protein in lung cells. These particles were made of polymers rather than lipids, making them easier to aerosolize for inhalation into the lungs. However, more work is needed on these particles to increase their potency and maximize their utility.
In their new study, the researchers set out to develop lipid nanoparticles that could reach the lungs. Particles are composed of molecules that contain two parts: a positively charged head group and a long lipid tail. The positive charge of the main group helps the particles interact with the negatively charged mRNA, and it also helps the mRNA escape cellular structures that engulf the particles once they enter cells.
The lipid structure of the tail, in turn, helps the particles to cross the cell membrane. The researchers created 10 different chemical structures for the lipid tails, along with 72 different head groups. By selecting different combinations of these structures in mice, the researchers were able to identify those most likely to reach the lungs.
In additional tests with mice, the researchers showed that they could use the particles to carry mRNA with CRISPR/Cas9 components designed to remove a genetically encoded stop signal in the animals’ lung cells. When that signal is removed, the gene for a fluorescent protein is turned on. Measuring this fluorescent signal allows researchers to determine what percentage of cells successfully expressed the mRNA.
The researchers found that after a dose of mRNA, about 40% of lung epithelial cells were transfected. Two doses raised the level to over 50% and three doses to 60%. The most important targets for treating lung disease are two types of epithelial cells called club cells and hair cells, each of which is about 15% transfected.
“That means that the cells that we were able to edit are really the cells of interest for lung disease,” says Li. “This lipid may allow us to transport mRNA to the lung much more efficiently than any other transport system known to date.”
The new particles are also quickly broken down, allowing them to be removed from the lung within a few days and reducing the risk of inflammation. The particles can also be administered multiple times to the same patient if repeated dosing is required. This makes them more advantageous than another mRNA delivery method, which uses a modified version of the harmless adenovirus. These viruses are very efficient at delivering RNA, but they cannot be delivered repeatedly because they induce an immune response in the host.
To deliver the particles in this study, the researchers used a method called intratracheal instillation, which is often used as a model for drug delivery into the lungs. Now they are working on making the nanoparticles more stable and can be aerosolized and inhaled with a nebulizer.
The researchers also plan to test the particles to deliver mRNA capable of correcting the genetic mutation of the gene that causes cystic fibrosis in a mouse model of the disease. They also hope to develop treatments for other lung diseases, such as idiopathic pulmonary fibrosis, as well as mRNA vaccines that can be delivered directly to the lungs.