How does in vivo transfection work?

In vivo transfection allows for the delivery of DNA, RNAi, or mRNA molecules into living organisms and can be performed using two methods, which are: viral or nonviral methods. This application is considered to be more complex than in vitro transfection. However, in vivo transfection is rapidly emerging as a very essential tool in basic and clinical research as well as in the development of gene therapies.

Methods of in vivo transfection:

• Viral methods of in vivo transfection require the use of specially designed viral vectors (e.g., lentiviruses or adenoviruses) to deliver nucleic acids into the cells of living organisms. These viral vectors are widely used in cell and gene therapy due to their high efficiency and their ability to integrate into the host genome for a desired gene expression.
• The Nonviral lipid-based in vivo transfection method has emerged as an invaluable means for the delivery of therapeutic agents into living organisms. Specifically, LNPs (lipid nanoparticles), are breakthrough mechanisms needed for performing in vivo gene delivery more safely and effectively.

The LNPs have a positive charge, which allows them to form complexes with the nucleic acids’ payload (e.g., siRNA molecule). The formed complexes can then be inserted into the organism via injection, where they enter cells during the process of endocytosis. Once inside the cell, the nucleic acid is released by the endosome and can go on to perform its intended function. In addition to positive charge, some LNPs consist of ionizable lipids, which exhibit a neutral charge at physiological pH that makes them less toxic to organisms than cationic

In vivo transfection applications:

• Vaccine development: In vivo transfection is critical to the development of new vaccines, which can use either viral or nonviral methods to deliver nucleic acids into cells. LNP-mediated mRNA delivery has proven to be an especially powerful tool for the development of vaccines targeted toward multiple diseases, including COVID-19. In addition, research into the use of personalized mRNA vaccines to target cancer cells highlights the impact and breadth of LNP-mediated in vivo transfection
• Functional Studies:  in vivo transfection is a vital step in ensuring that physiologically relevant results are obtained. Examples of transfection used in studies of gene function include introducing DNA plasmids or mRNA to examine the effects of overexpressing certain genes in organisms or using RNAi molecules to examine the effects of gene knockdown.
• Cell and gene therapy: gene therapy involves the transfer of genetic material, usually in a carrier or vector, and the uptake of the gene into the appropriate cells of the body. Cell therapy involves the transfer of cells with the relevant function into the patient. Some protocols utilize both gene therapy and cell therapy.