Rapid method for paraffin embedding of precision-cut liver slices

Precision-cut liver slices (PCLS) are tissue explants extensively used as an ex vivo model for metabolism and toxicity studies. When in vitro assays are conducted, it is imperative to perform a histomorphological evaluation as part of the viability analyses throughout the assay time. It is considered that good quality PCLS histological sections are difficult to obtain because they are hard to manipulate, and may shrink or fold during processing. Moreover, bibliography is not detailed on the embedding processes used. In this article, we propose an adjusted and rapid method for paraffin embedding of PCLS from crossbreed steers. Each PCLS was covered with a piece of gauze and placed into a histological cassette. These cassettes were submitted to a series of baths: 80 % ethanol for 10 min; 3 baths of 96 % ethanol for 10 min; 3 baths of butanol for 10 min; 1 bath of butanol-paraffin (1:1) for 20 min in a 60 °C laboratory oven; and 3 baths of paraffin for 20 min in a 60 °C laboratory oven. Folded paper boxes were used to produce paraffin blocks. It was possible to obtain complete sections with preserved cell morphology and no artifacts, and tissue appearance was similar to previous PCLS processed through the routine protocol, demonstrating the adequacy of the method implemented.