Bijan Khirabadi

Normothermic blood perfusion of isolated rabbit kidneys

Abstract.Cryopreservation of solid organs might be possible using a mixture of cell-permeable agents, cryoprotectants (CPA), which are designed to completely preclude ice crystal formation during cooling to cryogenic temperatures. The effects of a specific prototype solution (VS4) were evaluated by normothermic blood perfusion in vitro. Rabbit kidneys were divided into three groups: untreated controls (n=7), Euro-Collins (EC)-perfused controls (n=6) and VS4 (49%, w/v) CPA-perfused kidneys (n=7). After a 2-h blood perfusion, five of the seven CPA-perfused kidneys developed polyuria (0.21 ml×min–1×g–1) relative to untreated controls (0.07 ml×min–1×g–1) or EC-perfused kidneys (0.06 ml×min–1×g–1), owing to the lower reabsorption of water (34.3%), Na+ (34.2%) and glucose (35.6%). Furthermore, two kidneys were non-functional with virtually no urine production. Reduced tubular function was associated with reduced oxygen consumption (3.6 versus 2.3 versus 2.0 μmole×min–1×g–1 for controls, EC- and CPA-perfused kidneys, respectively) and increased weight gain (17% versus 20% versus 30%, respectively) after blood perfusion. Therefore, the current results provide insight into both the physiological effects of VS4 and the limits of reversibility of renal pathophysiological states. Our results also indicate that in vitro monitoring of oxygen consumption and weight gain of perfused organs could be used as predictors of renal function.

Using tandem scanning confocal microscopy to predict the status of donor kidneys.

Tandem scanning confocal microscopy (TSCM) is a noninvasive form of vital microscopy that can be used to evaluate superficial uriniferous tubules in living kidneys. Because TSCM has a number of advantages over conventional microscopic examination of renal biopsies, the present study was undertaken to determine whether the histopathological images obtained by TSCM correlate with post-transplant renal function. The kidneys of New Zealand male rabbits were harvested, flushed with Euro-Collins solution, and stored at 0–2°C for periods of 24, 48, 67 and 72 h prior to transplantation. TSCM observation of the kidneys prior to their transplantation revealed characteristic histopathological changes of the superficial proximal convoluted tubules that correlated closely with subsequent post-transplant renal function. These observations indicate that TSCM may be of significant value in evaluating the status of donor kidneys prior to their transplantation.

Normothermic blood perfusion of isolated rabbit kidneys. II. In vitro evaluation of renal function followed by orthotopic transplantation.

This study describes the use of a blood perfusion apparatus to assess the renal function of isolated kidneys. Eight fresh kidneys were obtained from healthy rabbits and perfused with blood at 36°C for 2 hours. Rabbit blood was drawn and diluted to a hematocrit of 25%. The kidneys were evaluated for their capacity to support life in an autograft model. Blood and urine samples were taken at regular time intervals during kidney perfusion. Serum creatinine was measured in surviving rabbits after transplantation. Over the course of the perfusion, arterial pressure was maintained at 87.2 ± 5.5 mm Hg. The renal blood flow (3.7 ± 1.0 ml/min per g) and urine output (0.11 ± 0.04 ml/min per g) were continuously monitored. Glomerular filtration rate (0.29 ± 0.02 ml/min per g) and fractional reabsorption (FR) of sodium and glucose indicated appreciable tubular function (FRNa = 67.9 ± 8.5%, FRGlu = 91.2 ± 5.8%). Protein was excluded from urine at 99.8%± 0.1%. After transplantation, the peak creatinine was 6.8 ± 3.2 mg/dl at 1.90 ± 0.92 days for the seven surviving rabbits and was above 16 mg/dl for the only rabbit that died 4 days after operation. The level of free hemoglobin generated at the end of the perfusion (2.6% ± 2.8%) was correlated with the postoperative peak creatinine (r2 = 0.84). Perfusion of seven additional kidneys by using the roller pump lead to a final hemolysis of only 0.34 ± 0.14%. Kidneys transplanted after 2 hours of blood perfusion were able to resume normal function and support life. Hemolysis was a measurable stress factor causing delayed function of the kidney after transplantation. Introduction of a roller pump significantly reduced the hemolysis.

Physiological evaluation of a rabbit kidney perfused with VS41A.

The current report compares the renal physiological impact of a standard vitrification solution, VS41A, as measured by normothermic blood perfusion, to the physiological effects of VS4, a related but more dilute vitrification solution previously shown to be consistently compatible with life support function of transplanted rabbit kidneys. VS41A, which allows survival of only about half of the kidneys perfused with it, also appeared to be more damaging than VS4 based on in vitro functional indices and histology in one rabbit kidney so evaluated.