The Development of a Novel in vitro Model Using Kidney Biopsy Specimens to Study the Effects of Warm and Cold Ischaemia on the Kidney

Traditional experimental methods of assessing renal function typically rely on whole kidneys and subsequent measures of glomerular filtration rate. In this study, we measured the viability of kidney biopsy samples of fixed length using formazan-based colorimetry in an attempt to evaluate the suitability of this assay in predicting whole organ viability. A series of experiments were set up to study the response of the ischaemic rabbit kidney tissue of fixed length (5 mm) obtained using a 16-gauge needle to various preservative solutions at various temperatures. Samples were maintained at 37 °C in a Hereaus EK/O2 incubator in an atmosphere of 5% CO2 in air, or at 1–4 °C in a Labheat incubator (Borolabs, U.K.) or at 20 °C in air for up to 96 hours. The formation of formazan within renal biopsy cores was most rapid during the first hour and then levelled off for the rest of the assay period (4 hours). Formazan formation was marginally more from renal cortex than medulla, although the differences were not statistically significant. The viability of kidney tissue was temperature dependent such that incubating a non-perfused kidney for 20 hours resulted in a 90% reduction in formazan formation and therefore viability at 37 °C compared to 1 °C. Formazan formation from rabbit kidney biopsy samples taken on day 0 and placed singly wells of a 24 well at-bottomed tissue culture plate containing 1.8 ml of preservative solution was assessed daily for 4 days. This was compared with the viability of tissue taken daily from whole kidneys perfused with the same preservative solution. Initial viability assessments were similar as were changes with time. This assay was able to demonstrate the superiority of the currently available renal preservative solutions Soltran and Viaspan in maintaining the viability of renal tissue at low temperatures compared with other randomly selected solutions. In conclusion, maintaining freshly obtained renal biopsy samples in a tissue culture system is a cheap, convenient and potentially useful model of renal ischaemia. Biochemical tests of cellular viability including formazan based colorimetry on isolated tissue may offer the opportunity to study the effects of ischaemia on the kidney, and may aid in the development of drugs for treating renal ischaemia.