Independent cellular effects of cold ischemia and reperfusion: experimental molecular study.

INTRODUCTION AND OBJECTIVES: There is less information available on cell cultures on the exclusive effects of either duration of cold ischemia (CI) or rewarming-reperfusion in the kidney subjected to initial warm ischemia (WI). Therefore, the goals of our work were: (1) to evaluate the consequences on tubular cellular viability of different durations of CI on a kidney after an initial period of WI, and (2) to analyze the additional effect on tubular cell viability of rewarming of the same kidney. ANIMALS AND METHODS: Sixteen mini-pig were used. All the animals were performed a right nephrectomy after 45-minute occlusion of the vascular pedicle. The kidneys were then divided into 2 groups (phase 1): cold storage in university of wisconsin (UW) solution for 3 hours (group A, n = 8) at 4°C, or cold storage in UW for 12 hours (group B, n = 8) at 4°C. Four organs of group A and four organs of group B were autotrasplanted (AT) and reperfused for 1 hour (phase 2). Nephrectomy was finally done. Biopsies were taken from all groups to perform cultures of proximal tubule epithelium cells. The biopsies were subjected to studies of cellular morphological viability (contrast phase microscopy [CPM]) and quantitative (confluence cell [CC]) parameters. RESULTS: Phase of pure CI effects (phase 1): Both CC rate and CPM parameters were significantly lower in group B compared with group A, where cell activity reached almost normal results. Phase of CI + AT (phase 2): At produced additional harmful effects in cell cultures compared with those obtained in phase 1, more evident in group B cells. CONCLUSIONS: The presence of cold storage followed by rewarming-reperfusion induces independent and cumulative detrimental effects in viability of renal proximal tubule cells. CI periods ≤ 3 hours may ameliorate the injuries secondary to reperfusion in comparison with longer CI periods.

Optimizing outcomes by preconditioning the donor.

The criteria that define a so-called "marginal donor" kidney have been standardized since 2002. However, every transplant center must establish its own guidelines on organ acceptability. An expanded criteria donor (ECD) kidney is age at least 60 years, or 50 to 59 years with at least two of three specified comorbidities. Cadaveric kidneys have shown worse functional and survival outcomes compared with those from living donors. Thus, all efforts should be made to minimize the effects of ischemia on standard, non-heart-beating or ECD cadaveric donor kidneys. Because of an increasing shortfall between the diminishing number of deceased donor organs available and the increasing waiting lists, an increasing number of living donor transplantations are being performed in Europe. Among deceased donor kidneys, the largest percentage corresponds to ECD--aged or comorbidity donors--and donors after cardiac death. The results of transplants with kidneys from donors over 65 years are 10% to 15% lower than those from younger donors. Older donors present more comorbidities; however, acceptable results may be obtained with careful selection and shortened cold ischemic times. If the transplant center uses these donors to expand the pool of available organs, the donor must be evaluated according to age, vascular condition, renal function, and comorbidity. If the donor is accepted, suitable questions are: Has the potential donor undergone maneuvers to improve the quality of the kidneys? Which kind of approaches should we perform? Should we only use the biopsy information for a decision?

[Study on the role of the tubule in renal vasoconstriction induced by cyclosporine]. / Papel del túbulo en la vasoconstricción renal inducida por ciclosporina.

INTRODUCTION: Cyclosporine (CyA) has proved to induce cell apoptosis on cultured proximal tubule cells. However, there is no much data about the in vivo functional consequences of this injury or the long time observed CyA-induced renal vasoconstriction. MATERIAL AND METHODS: In a swine model of subacute CyA nephrotoxicity (10 mg/ Kg. dx 15 days), we performed a right nephrectomy, followed by left renal artery, vein and ureter catheterisati8n. After inducing water diuresis, three clearance periods of 15 minutes were performed before and after a furosemide 1 mg/kg infusion. Plasma and urine electrolytes, blood gas, acid excretion, plasma renin activity and aldosterone concentration, GFR, RPF, RBF, intra-renal vascular resistances, glomerular filtration pressure, distal Cl- delivery, water clearance and TTKG were measured or estimated on 7 control and 7 treated animals. Right kidney was processed for NaKATPase activity and immunostaining. RESULTS: Treated animals presented detaching proximal cells, luminal blebbing and loss of tight junctions. Cortical but not medullar sodium pump was internalised and partially inactive. Treated animals showed much lower fractional excretions of Na+, with significantly higher distal fractional reabsorption of Cl. Distal shift in fluid load resulted in a significant rise in renal O2 consumption, and modifications in the global renal estequiometry of Na+ transport/O2 uptake. Several consequences followed this situation: preglomerular resistances increased 3 times with only minor changes in postglomerular resistances and renal blood and plasma flow were significantly reduced. Furosemide partially reversed these effects. A slight increase in fractional filtration prevented GFR differences to become statistically significant. CONCLUSION: subacute CyA treatment even al doses not modifying GFR, may cause proximal tubule Na+ transport impairment, resulting in increased rates of distal delivery and absorption of fluid load. Renal uptake of O2 may be increased and tubule glomerular feedback should be expected to be activated. Absence of changes of GFR with furosemide is an early sign of CyA renal damage.

Papel del túbulo en la vasoconstricción renal inducida por ciclosporina / Study of the role of the tubule in renal vasoconstriction induced by cyclosporine

Introducción: Ciclosporina es el primero de una familia de potentes inmunosupresores con capacidad anticalcineurínica que, sin embargo, presentan como limitación terapéutica una nefrotoxicidad que puede aparecer desde periodos tempranos. Los primeros datos funcionales sugerían la existencia de vasoconstricción renal, si bien estudios posteriores han mostrado un efecto tóxico directo de ciclosporina sobre el túbulo proximal. Materiales y Métodos: En este artículo se presenta un modelo porcino de nefrotoxicidad por ciclosporina a medio plazo, analizándose los cambios hemodinámicos intrarrenales y las funciones tubulares, así como la relación entre ambos. Resultados: Ciclosporina produce específicamente una internalización e inactivación de la Na+, K+-ATPasa basolateral del túbulo proximal, determinando el desplazamiento axial de la carga filtrada hacia regiones distales (asa de Henle), con transportes activos más intensos y no modificados por ciclosporina. El resultado es un aumento en la reabsorción fraccional distal de cloro que condiciona un estímulo del “feed-back” túbulo glomerular, vasoconstricción aferente pero no eferente, aumento de las resistencias renales y caída de la presión intraglomerular. Furosemida restaura parcialmente la situación basal. La consecuencia inmediata es un aumento en el consumo de O2 por unidad de sodio trasportado. A nivel del túbulo colector no se observan cambios en la secreción de agua libre, pero la secreción de K+ parece limitada, y no se corrige al aumentar la oferta distal de sodio con furosemida, ni con aldosterona, cuyos valores fueron más altos en los animales tratados con ciclosporina. Conclusión: En resumen, el efecto vasoconstrictor de ciclosporina sobre el riñón se debe en parte a una retroalimentación túbulo glomerular activada por el desplazamiento de solutos filtrados de sus sitios de reabsorción proximal a otros sitos más distales. Las dietas con alto contenido en sodio pueden aumentar el efecto deletéreo de ciclosporina sobre el filtrado glomerular

Introduction: Cyclosporine (CyA) has proved to induce cell apoptosis on cultured proximal tubule cells. However, there is no much data about the in vivo functional consequences of this injury or the long time observed CyA-induced renal vasoconstriction. Material and Methods: In a swine model of subacute CyA nephrotoxicity (10 mg/ Kg. d x 15 days), we performed a right nephrectomy, followed by left renal artery, vein and ureter catheterisation. After inducing water diuresis, three clearance periods of 15 minutes were performed before and after a furosemide 1 mg/kg infusion. Plasma and urine electrolytes, blood gas, acid excretion, plasma renin activity and aldosterone concentration, GFR, RPF, RBF, intra-renal vascular resistances, glomerular filtration pressure, distal Cl- delivery, water clearance and TTKG were measured or estimated on 7 control and 7 treated animals. Right kidney was processed for NaKATPase activity and immunostaining. Results: Treated animals presented detaching proximal cells, luminal blebbing and loss of tight junctions. Cortical but not medullar sodium pump was internalised and partially inactive. Treated animals showed much lower fractional excretions of Na+, with significantly higher distal fractional reabsorption of Cl-. Distal shift in fluid load resulted in a significant rise in renal O2 consumption, and modifications in the global renal estequiometry of Na+ transport/O2 uptake. Several consequences followed this situation: preglomerular resistances increased 3 times with only minor changes in postglomerular resistances and renal blood and plasma flow were significantly reduced. Furosemide partially reversed these effects. A slight increase in fractional filtration prevented GFR differences to become statistically significant. Conclusión: subacute CyA treatment even al doses not modifying GFR, may cause proximal tubule Na+ transport impairment, resulting in increased rates of distal delivery and absorption of fluid load. Renal uptake of O2 may be increased and tubule glomerular feedback should be expected to be activated. Absence of changes of GFR with furosemide is an early sign of CyA renal damage

Sildenafil improves immediate posttransplant parameters in warm-ischemic kidney transplants: experimental study.

OBJECTIVE: To evaluate in an experimental model the effects of the PDE5 inhibitor sildenafil on kidney grafts autotransplanted after a period of 45 minutes of warm ischemia and 60 minutes of hypothermic pump perfusion. METHODS: Nine laboratory large-white pigs were divided into two groups. Group A (n = 4): oral dose of 100 mg sildenafil was administered 1 hour before the surgery. Group B (n = 5): no sildenafil given. Right single nephrectomy was completed after a 45-minute period of warm ischemia by complete vascular clamping. Before the autotransplant, all kidneys were submitted to a 60-minute period of hypothermic pulsatile perfusion. Renal flow, arterial pressure, and renal vascular resistance were recorded in real time for 60 minutes after autotransplant. Nitric oxide levels were determined in blood samples of the renal vein at predefined intervals. Optical and electronic microscopy was performed on all organs at the end of the procedure. RESULTS: Renal vascular flow was significantly higher and renal vascular resistance significantly lower in the sildenafil group compared with the non-sildenafil group. No significant differences were observed in systemic arterial pressure values between both groups. Nitric oxide levels were significantly higher for all periods in the sildenafil group. No differences were observed in histological studies. CONCLUSION: Our experimental work suggested a positive effect of sildenafil on the immediate posttransplant outcome of warm-ischemic kidneys without systemic secondary effects.

Effects of hypothermic perfusion in isolated pig kidneys after warm ischemia.

An experimental study in pigs was designed to evaluate the consequences of normothermic ischemia in hypothermic isolated renal perfusion (HP). We perfused 16 kidneys after 45 minutes of vascular occlusion. Another 16 kidneys were perfused without previous warm ischemia. The ureter was catheterized in all procedures and the output collected during HP. Creatinine was added to the perfusion solution initially in order to determine creatinine clearance (CrCl). HP hydrodynamics were recorded in real time through a computerized system. According to the results, renal vascular resistance as well as CrCl were higher in ischemic kidneys. Both facts, along with minimal differences in the microscopic study, suggested an increased vascular tone of the efferent postglomerular arteriole during HP. HP was proven to be an optimal technique to minimize the histological consequences of ischemia. Microvascular and biochemical changes produced during HP may be essentially related to dynamic causes.

[New perspectives in the preservation of kidney grafts]. / Nuevas perspectivas en la preservación de injertos renales.

OBJECTIVES: Graft preservation, together with overcoming the immunological barrier responsible for graft rejection, are the most important problems of organ transplantation. The different solutions to the foregoing problems are briefly analyzed. METHODS/RESULTS: The literature on graft rejection and preservation is briefly reviewed, highlighting the most outstanding developments. The availability of cyclosporine in the early eighties significantly enhanced the results of immunosuppression and made it less aggressive for graft recipients. The use of liquids for hypothermic preservation of the donor organ, with the advantages and disadvantages it entailed, was a major advancement in cold ischemia. Different solutions (Eurocollins, Wisconsin, HTK) were developed to reduce metabolic derangements from the time the organ was harvested until it was transplanted, with the aim of permitting immediate graft function in order to reduce the incidence of acute tubular necrosis. Further insight into the histological lesions caused by ischemia, the endothelial lesion and its role in tubular dysfunction have led different groups to use pulsatile perfusion once again, particularly since non-heartbeating donor programs were developed. CONCLUSIONS: Although the advancements in the preservation of renal grafts have permitted extending the cold ischemia time beyond 24 hours, the incidence of tubular necrosis continues to be significant. The foregoing, together with the development of renal transplant programs for non-hearbeating donor kidneys, have emphasized the need for further knowledge and understanding of graft viability and early function.