Dataset Information

Biolistic transfection and expression analysis of acute cortical slices.

ABSTRACT:

Background

Biolistic gene gun transfection has been used to transfect organotypic cultures (OTCs) or dissociated cultures in vitro. Here, we modified this technique to allow successful transfection of acute brain slices, followed by measurement of neuronal activity within a few hours.

New method

We established biolistic transfection of murine acute cortical slices to measure calcium signals. Acute slices are mounted on plasma/thrombin coagulate and transfected with a calcium sensor. Imaging can be performed within 4 h post transfection without affecting cell viability.

Results

Four hours after GCaMP6s transfection, acute slices display remarkable fluorescent protein expression level allowing to study spontaneous activity and receptor pharmacology. While optimal gas pressure (150 psi) and gold particle size used (1 μm) confirm previously published protocols, the amount of 5 μg DNA was found to be optimal for particle coating.

Comparison with existing methods

The major advantage of this technique is the rapid disposition of acute slices for calcium imaging. No transgenic GECI expressing animals or OTC for long periods are required. In acute slices, network interaction and connectivity are preserved. The method allows to obtain physiological readouts within 4 h, before functional tissue modifications might come into effect. Limitations of this technique are random transfection, low expression efficiency when using specific promotors, and preclusion or genetic manipulations that require a prolonged time before physiological changes become measurable, such as expression of recombinant proteins that require transport to distant subcellular localizations.

Conclusion

The method is optimal for short-time investigation of calcium signals in acute slices.

SUBMITTER: Hamad MIK

PROVIDER: S-EPMC7125026 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundOrganotypic brain slices (OTBS) are an excellent experimental compromise between the facility of working with cell cultures and the biological relevance of using animal models where anatomical, morphological, and cellular function of specific brain regions can be maintained. The biological characteristics of OTBS can subsequently be examined under well-defined conditions. They do, however, have a number of limitations; most brain slices are derived from neonatal animals, as it is difficult to properly prepare and maintain adult OTBS. There are ample problems with tissue integrity as OTBS are delicate and frequently become damaged during the preparative stages. Notwithstanding these obstacles, the introduced exogenous proteins into both neuronal cells, and cells imbedded within tissues, have been consistently difficult to achieve.ResultsFollowing the ex vivo extraction of adult mouse brains, mounted inside a medium-agarose matrix, we have exploited a precise slicing procedure using a custom built vibroslicer. To transfect these slices we used an improved biolistic transfection method using a custom made low-pressure barrel and novel DNA-coated nanoparticles (40 nm), which are drastically smaller than traditional microparticles. These nanoparticles also minimize tissue damage as seen by a significant reduction in lactate dehydrogenase activity as well as propidium iodide (PI) and dUTP labelling compared to larger traditional gold particles used on these OTBS. Furthermore, following EYFP exogene delivery by gene gun, the 40 nm treated OTBS displayed a significantly larger number of viable NeuN and EYFP positive cells. These OTBS expressed the exogenous proteins for many weeks.ConclusionsOur described methodology of producing OTBS, which results in better reproducibility with less tissue damage, permits the exploitation of mature fully formed adult brains for advanced neurobiological studies. The novel 40 nm particles are ideal for the viable biolistic transfection of OTBS by reducing tissue stress while maintaining long term exogene expression.