Science

Unique mRNA delivery method could repair defective genes before birth

In utero delivery of Cas9 mRNA/gRNA by ADP-LNP leads to extensive cell editing in the fetal brain. Credit: University of California, Davis

New research shows that biomedical tools can successfully deliver genetic material to edit defective genes in developing fetal brain cells. The technology, tested in mice, could halt the progression of genetically based neurodevelopmental conditions such as Angelman syndrome and Rett syndrome before birth.

“The implications of this tool for the treatment of neurodevelopmental conditions are profound, with the potential to correct genetic abnormalities at a basal level during a critical period of brain development,” said the study’s lead author, a professor at the University of California, Davis. said Aijun Wang, professor of surgery and biomedical engineering.

The research is a collaboration between the Wang and Marcy labs at the University of California, Berkeley, and is published in ACS Nano. The research team hopes to develop this technology as a treatment for genetic diseases that can be diagnosed with prenatal testing. Treatment can be done in utero to avoid further damage to the cells as they develop and mature.

Complex transportation system with innovative delivery methods

Proteins play an important role in the functioning of our bodies. These are assembled within cells based on instructions from messenger RNA (mRNA). In certain genetic conditions, genes express (produce) more or less protein than the body needs. In these cases, the body may become dysregulated and need to suppress excess genes or compensate for low protein levels.

“Proteins are difficult to deliver because they are large and have complex structures,” Wang says. “Their delivery remains a huge challenge and a dream in treating the disease.”

Instead of delivering proteins, scientists have discovered a way to deliver mRNA into cells, which is translated into functional proteins within the cells. This delivery method uses a proprietary lipid nanoparticle (LNP) formulation to carry the mRNA. The purpose is to introduce (transfect) mRNA genetic material into cells. The mRNA then translates the instructions to build the protein.

Delivery of mRNA using LNPs is already transforming disease treatment. It has applications in vaccine development, gene editing, and protein replacement therapy. Recently, mRNA delivery has become more popular with its use in Pfizer and Moderna’s COVID-19 vaccines.

The importance of efficiency in LNP delivery of mRNA

In a recent Nature Nanotechnology paper, Wang, Murthy, and their team described a new LNP formulation for safely and efficiently delivering mRNA. LNPs carrying mRNA must reach cells, where they are taken up through a process known as endocytosis. There, the cells destroy the LNP carrier, thereby allowing the mRNA cargo to be released.

The size of a single mRNA is approximately 100 nanometers. For comparison, paper is approximately 100,000 nanometers thick.

“The LNPs developed in this study use a new acid-degradable linker that allows the LNPs to be rapidly degraded within cells. The new linker also allows us to engineer the LNPs to have lower toxicity. ,” said Niren Murthy, professor of bioengineering at the University of California. He is a professor at Berkeley and a co-investigator on this project.

“Once a cell takes up LNPs, the particles are broken down in the acidic environment of the cell’s endosomes. This allows for more efficient and earlier transfer of mRNA to the cytosol, the fluid component within the cell where mRNA is translated into protein. “So we want to make the mRNA effective and functional,” Wang explained.

Efficiency is closely related to toxicity. Therefore, it is important to know how many LNP carriers a cell needs to take up to produce enough protein. If the uptake efficiency is low, scientists must use large amounts of nanoparticles. This means multiple doses or high doses that can cause a toxic immune response.

“So far, the biggest obstacle to delivering mRNA to the central nervous system is the toxicity that causes inflammation,” Wang said.

This study showed that the LNP method has a higher efficiency of mRNA translation, reducing the need for potentially toxic doses.

Can new medical approaches repair defective genes before birth?

Staining of neural stem cells and neural progenitor cells in fetal brain transfected with Cre mRNA delivered by LNP. Credit: University of California, Davis

Delivery of CAS9 enzyme construction manual for gene editing

A new study describes the use of LNP technology for Cas9 mRNA delivery to treat genetic disorders of the central nervous system in utero. The researchers tested the tool on the genes responsible for Angelman syndrome, a rare neurodevelopmental disease.

In genetic disorders, damage accumulates during pregnancy and immediately after birth. Research has shown that it is more efficient to treat brain cells before an infant’s blood-brain barrier is fully formed. Therefore, the sooner you fix it, the better. The idea was to halt the progression of the disease in the womb.

The researchers injected the LNPs containing the mRNA into the ventricles of fetal brains in a mouse model. The mRNA is translated into the protein CAS9, which acts like a pair of gene-editing scissors. The resulting CAS9 edits the gene responsible for Angelman syndrome.

“mRNA is like a Lego manual that explains how to put the pieces together to form a functional protein. The cell itself has all the pieces to build CAS9. All you have to do is supply the protein, and the cell will receive it and translate it.” Wang explained.

Survey results

In this study, the LNP tool was shown to be highly efficient in delivering mRNA that is translated into CAS-9.

Using tracers, the researchers were able to see all the edited neurons in the brain. Their study showed that the nanoparticles were taken up by neural stem cells and neural progenitor cells during the brain’s development. The nanoparticles caused gene editing in 30% of brain stem cells in a mouse model.

“It’s a big deal to transfect 30% of the entire brain, especially stem cells. These cells migrate and spread to many locations throughout the brain as the fetus develops further,” Wang said.

In this study, as the fetus progressed, the stem cells proliferated and migrated to form the central nervous system. The study revealed that more than 60% of neurons in the hippocampus and 40% of neurons in the cortex were transfected.

“This is a very promising method for genetic diseases that affect the central nervous system. By the time a baby is born, many neurons may have (already) been modified. This means they can be born asymptomatic,” Dr. Wang explained.

Wang expects the proportion of transfected cells to be even higher in diseased mouse models.

“Bad neurons with mutations can be killed off by the accumulation of disease symptoms, while good neurons can remain and proliferate. This could lead to amplification of therapeutic effects. “If we have a good understanding of what works, we can use this knowledge to work with naturally occurring cellular pathways,” he said.

More information: Kewa Gao et al, Broad gene editing in the brain through in utero delivery of mRNA using acid-degradable lipid nanoparticles, ACS Nano (2024). DOI: 10.1021/acsnano.4c05169 Sheng Zhao et al, Acid-degradable lipid nanoparticles enhance mRNA delivery, Nature Nanotechnology (2024). DOI: 10.1038/s41565-024-01765-4

Citation: Unique mRNA delivery method could correct defective genes before birth (October 24, 2024) https://phys.org/news/2024-10-unique-mrna-delivery- Retrieved October 24, 2024 from method-faulty.html

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