Whitepaper

"Precision-cut liver tissue slices are a powerful tool to perform studies on pharmacological metabolism as well as studies investigating toxicology and efficacy of novel substances on primary material under standardized conditions. Slicing of primary liver tissue has been realized using different slicing machines. Since there has been great variability in the results, we sought to develop a highly reproducible method for slicing of liver tissue.

Liver samples from five different species (human, mouse, rat, pig, cattle) were cut using the Leica VT1200 S with Vibrocheck and the reproducibility of slice thickness and quality was determined. Compared to slicers used in the field so far, we demonstrated an improved accuracy and reproducibility of tissue slices."

"Xylene-free processing (XFP) was evaluated over several months using the Leica Peloris™ tissue processor. The criteria selected pre evaluation were processed block quality, microtomy properties, stained section quality, duration of processing, running costs, user-friendliness and reliability.

The Peloris was used to process tissue from the full range of specimen types received, including technically demanding blocks, such as surgical osteo-articular blocks measuring upto 60 x 55 x 4 mm, soft-tissue blocks of similar dimensions, as well as conventionally sized soft tissue blocks. In total several thousand pieces of tissue were processed xylene-free during the evaluation, alongside a similar range of tissues processed conventionally.

Whilst the evaluation had its limitations, the results were unequivocal, in that, with the possible exception of foetal CNS tissue, XFP exceeded expectations in every respect; it was demonstrably superior to conventional processing systems in key areas.

Three years on, users of XFP within this Department remain confident that it is the current “method of choice”, in that the incidence of any block being inadequately processed, or unsuitable for subsequent procedures in any way remains at zero; in our hands XFP is especially good for the processing of the high number of technically demanding tissues generated in this large histopathology department.

NB The work upon which the paper was based was carried-out at the Freeman Hospital and it is being furthered at the Royal Victoria Infirmary where all of the histopathology is now centred. Both hospitals belong to Newcastle upon Tyne NHS Foundation Trust."

"This paper presents the results of comparative evaluations carried out during field trials in two large public hospitals. These trials set out to examine whether the design features of the Peloris dual retort tissue processor led to reduced processing times for large specimens without compromising quality. In the context of a busy histopathology laboratory, we demonstrate that the introduction of Peloris processing would allow the processing of large, dense specimens in 6 hours leading to the completion of more runs in a working day and the reduction of turnaround times.

Ten sequential six hour and nine hour processing runs were undertaken on a Peloris processor at either 45 °C or 55 °C and the resultant blocks and sections were evaluated for quality using a comprehensive scoring system. Peloris results were compared to those achieved on a matched panel of specimens processed using a processor that represents the industry standard (the Tissue-Tek® VIP™). The results show that for large, dense specimens Peloris can produce results of an equivalent standard to an “overnight” schedule (13 hours) run on a VIP using much shorter schedules. Results also indicate that there is some advantage in processing at higher temperature (55 °C) for both the six and nine hour schedules."

This paper outlines the test procedure and scoring system which has been used to objectively evaluate the quality of tissue processing during the development and comparative evaluation of the Peloris™ tissue processor and as a mechanism for optimising standard processing protocols.

The source and content of suitable specimen panels are described and the need for standardization of every aspect of specimen handling, processing and section preparation is emphasised. The scoring system assesses 23 parameters in six groups and is based on a three point scale. The system effectively allows comparisons of processing runs to be made using different processors or different protocols on the same processor.

"This preliminary study demonstrated that xylene-free processing on the Peloris™ dual retort rapid tissue processor using isopropanol, can effectively prepare tissue from the central nervous system to a standard that is at least the equal of traditional xylene or chloroform schedules and in six hours instead of the more usual fourteen hours. The work described in this paper was carried out as an extension of a field trial conducted by Austin Health (Victoria Australia) together with Vision BioSystems (VBS) as part of the development of the Peloris tissue processor. Vision Biosystems has since formed part of the Biosystems Division of Leica Microsystems.

Tissues from the central nervous system, which are widely acknowledged as being difficult to section successfully, were processed using six, nine and twelve hour evaporative isopropanol schedules (xylenefree) using a Peloris processor. The results were compared to fourteen and twenty four hour schedules carried out using Tissue-Tek® VIPTM processors employing either xylene or chloroform. Sections were stained with H&E, Luxol Fast Blue/ Cresyl Violet, and Garvey Silver stain. Results were assessed separately by staff from Austin Health and Vision BioSystems."