Optimization of long-term incubation of precision-cut kidney slices

Precision-cut kidney slices (PCKS) provide a powerful model to close the gap between in vivo and in vitro research. Publications by various authors favor different incubation conditions, media, and antibiotics, that have not yet been compared in a standardized manner. After preparation, rat-PCKS were incubated in a total of nine combinations of incubation media and antibiotics for four days. We found that a combination of DMEM/F-12 and gentamicin showed the highest levels of viability. Utilizing both qualitative and quantitative methods, we observed stable levels of cellular viability for 10 days when incubated in the most suitable medium combination of DMEM and gentamicin. Additionally, a calcein acetoxymethyl/ethidium homodimer-1 based live/dead staining, analysis of total protein content and lactate dehydrogenase (LDH) were explored to assess both short- and long-term tissue viability. PCKS showed a significant decrease in total protein content, leveling off at around 60% over the duration of 10 days. To be able to evaluate viability irrespective of decreases in total protein detected, we chose to utilize the alamarBlue Cell Viability Assay. Quantifying both intra- and extracellular activity of LDH, while using different concentrations of ethanol as a positive control, we explored enzyme content as a parameter for cell membrane damage and cytotoxicity in PCKS. Overall, we showed that PCKS are suitable for both short- and long-term observation by optimizing incubation parameters, with numerous possibilities for other assays and methods in future studies.