Human Respiratory System Lungs Anatomy
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A newly created nanoparticle that carries a messenger RNA (mRNA) payload that can be administered to the lungs may offer a method to provide an inhalable treatment for cystic fibrosis and other lung diseases.

Designed by engineers at MIT and the University of Massachusetts Medical School and applied in a recent mouse study, the new nanoparticles delivered mRNA that encoded the machinery needed for CRISPR/Cas9 gene editing, a breakthrough that could provide a pathway for designing therapeutic nanoparticles capable of snipping out and replacing disease-causing genes.

“This is the first demonstration of highly efficient delivery of RNA to the lungs in mice,” said Daniel Anderson, a professor in MIT’s Department of Chemical Engineering and a member of MIT’s Koch Institute for Integrative Cancer Research and Institute for Medical Engineering and Science (IMES). “We are hopeful that it can be used to treat or repair a range of genetic diseases, including cystic fibrosis.”

The use of mRNA continues to show its ability as a therapeutic for the treatment of diseases with a genetic basis. But a challenge has been finding ways to deliver the mRNA therapeutic to the right part of the body without there being any off-target effects. mRNA treatments for liver disease are already underway, and the RNA-based COVID vaccines have also proven mRNA’s merit. One method often used for the delivery of mRNA is via a lipid nanoparticle, where the lipid encapsulates the mRNA to help it enter targeted cells without being broken down before it reaches the target.

The Anderson lab at MIT has sought to design particles that can be used for the delivery of therapeutics. In 2019, the lab created nanoparticles that could deliver mRNA encoding a bioluminescent protein to lung cells. Those particles were made from polymers instead of lipids, which made them easier to aerosolize for inhalation into the lungs. However, more work is needed on those particles to increase their potency and maximize their usefulness.

For the current study, published today in Nature Biotechnology, the research team looked to design nanoparticles that could target the lungs comprising two parts: a positively charged headgroup and a long lipid tail. The positive charge serve to both interact with negatively charged mRNA, while also helping it to escape from the lipid outer structure once it enters the target cell. For its part, the lipid structure helps the nanoparticles pass through the cell membrane. In total, the team developed 72 different headgroups and 10 different chemical structures for the lipid tails, which it then screened in mice to determine those that were most likely to reach the lungs.

Further testing revealed that the nanoparticles could be used with mRNA that encodes CRISPR/Cas9 components designed to edit out a stop signal that was genetically encoded into lung cells of the mouse models. When the stop signal was removed a gene for a fluorescent protein was turned on, which then allowed the researchers to measure the fluorescent signal as a method to determine the percentage of cells that successfully expressed the mRNA.

After one dose, the team’s measurements show that 40% of the epithelial cells were transfected. A second dose raised this to 50% of cells, and a third dose to 60% of the cells. The most important target for treating lung disease are two types of epithelial cells—club cells and ciliated cells. Each of these two types were transfected at around 15%.

“This means that the cells we were able to edit are really the cells of interest for lung disease,” said Bowen Li, a former MIT postdoc who is now an assistant professor at the University of Toronto and a senior author on 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.”

The nanoparticles also exhibited other positive characteristics: they broke down quickly allowing them to be cleared from the lungs and reduced inflammation risk and they could be delivered multiple times important of a patient requires multiple doses.

The researchers now plan to see if they can deliver nanoparticles designed to correct a genetic mutation in cystic fibrosis in mouse models of the disease. Other treatments using this method include for idiopathic pulmonary fibrosis, as well as mRNA vaccines that could be delivered directly to the lungs.

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