Transseptal transcatheter mitral valve implantation versus redo surgical mitral valve replacement for degenerated mitral bioprostheses

Background

The growing use of surgical bioprostheses raises concerns about a future reoperation for bioprosthesis degeneration. There are few data on outcome after transcatheter mitral valve-in-valve implantation (TMVI) compared with redo surgical mitral valve replacement (SMVR).

Purpose

To compare the feasibility, safety and outcomes of TMVI versus SMVR for degenerated mitral bioprosthesis in high-risk patients.

Methods

In our institution, 52 patients underwent TMVI by transseptal approach and 33 SMVR for degenerated mitral bioprosthesis. The composite endpoint of event-free survival included cardiovascular mortality, stroke, major bleeding, hospitalization for heart failure or mitral valve reintervention.

Results

Mean age and EuroSCORE II were higher in TMVI group vs. SMVR group (age 63±21 years vs. 51±15 years, p=0.002; EuroSCORE II 12.5±12.2% vs. 6.2±3.3%, p=0.001) (Table). In-hospital mortality was 3.8% after TMVI vs. 3.0% after SMVR (p=1.0).

Median follow-up was 2.2 years. At 5 years, survival was 69.7±9.4% after TMVI vs. 86.6±7.6% after SMVR (p=0.10) and event-free survival was lower after TMVI (40.1±9.9% vs 78.7±8.8% respectively, p=0.003) (Figure). In multivariate analysis, older age (p=0.02), neurologic history (p=0.05) and non-elective procedure (p<0.0001) were associated with lower event-free survival, while TMVI vs. SMVR was no longer significant (p=0.17). At last follow-up, 84% patients from TMVI group and 78% from SMVR group were NYHA I-II class. Mean mitral valve gradient and pulmonary artery systolic pressure were respectively 6.8±2.5 mmHg and 45±14 mmHg in TMVI group, and 4.8±2.0 mmHg and 37±11 mmHg in SMVR group.

Conclusion

TMVI is an alternative to SMVR in high-risk patients with degenerated mitral bioprosthesis. Comparison of mid-term results of the two techniques must take into account the differences in patient characteristics.

Event-free survival

Funding Acknowledgement

Type of funding source: None

Supplementation of increasing amounts of linseed oil to dairy cows fed total mixed rations: effects on digestion, ruminal fermentation characteristics, protozoal populations, and milk fatty acid composition

The effect of linseed oil (LO) supplementation on nutrient digestibility, forage (i.e., timothy hay) in sacco ruminal degradation, ruminal fermentation characteristics, protozoal populations, milk production, and milk fatty acid (FA) profile in dairy cows was investigated. Four ruminally cannulated, primiparous lactating cows were used in a 4 × 4 Latin square design (28-d periods). They were fed a total mixed ration (50:50 forage:concentrate (F:C) ratio [dry matter (DM) basis] without supplementation (control, CTL), or supplemented (wt/wt; DM basis) with LO at 2, 3, or 4%. Supplementation with LO had no effect on DM intake (19 kg/d) and apparent total-tract digestibility of nutrients (organic matter, neutral detergent fiber, acid detergent fiber, starch, and gross energy). Ruminal pH, ammonia, and total volatile FA concentrations were not changed by LO supplementation to diets. Extent of changes in volatile FA pattern and effective ruminal degradability of DM of timothy hay were minor. Neither the total numbers nor the genera distribution of protozoa was changed by the addition of increasing amounts of LO to the diet. Milk yield increased linearly (26.1, 27.3, 27.4, and 28.4 kg/d for CTL to LO4, respectively) as the amount of LO added to the diet increased. Milk fat content was not affected by LO supplementation, whereas milk protein content decreased linearly with increasing amounts of LO in the diet. Milk fat proportions of several intermediates of ruminal biohydrogenation of polyunsaturated FA (i.e., trans-10 18:1, trans-11 18:1, cis-9,trans-11 18:2, trans-11,cis-15 18:2, and cis-9,trans-11,cis-15 18:3) increased linearly with LO addition to the diet. The proportion of cis-9,cis-12 18:2 decreased linearly (2.06, 1.99, 1.91, and 1.83% for CTL to LO4, respectively) as the amount of LO in the diet increased. Milk fat content of cis-9,cis-12,cis-15 18:3 increased as the level of LO in the diet increased up to 3% but no further increase was observed when 4% of LO was fed (0.33, 0.79, 0.86, and 0.86% for CTL to LO4, respectively). A similar quadratic response to LO supplementation was also observed for cis-5,cis-8,cis-11,cis-14,cis-17 20:5 and cis-5,cis-7,cis-10,cis-13,cis-16 22:5. The results of the present study show that LO can be safely supplemented up to 4% in forage-based diets of dairy cows to enrich milk with potential health beneficial FA (i.e., n-3 FA) without causing any detrimental effects on rumen function, digestion, and milk production.

Concentration and chain length of polyethylene glycol in islet isolation solution: evaluation in a pancreatic islet transplantation model

To improve graft preservation and consequently reduce conservation injuries, the composition of preservation solution is of outmost importance. It was demonstrated that the colloid polyethylene glycol (PEG), used in SCOT solution, has protective effects on cell membranes and immunocamouflage properties. The aim of this study was to optimize the concentration and chain length of PEG to improve pancreatic islet preservation and outcome. In a model of murine islet allotransplantation, islets were isolated with SCOT containing various concentrations of PEG 20 kDa or 35 kDa. Better islet yield (IEQ) was obtained with SCO +PEG at 15-30 g/L versus other PEG concentrations and control CMRL-1066 + 1% BSA solution (p < 0.05). Allograft survival was better prolonged (up to 20 days) in the groups SCOT + PEG 20 kDa 10-30 g/L compared to PEG 35 kDa (less than 17.8 days) and to control solutions (less than 17.5 days). In terms of graft function recovery, the use of PEG 20 kDa 15-30 g/L induced no primary nonfunction and delayed graft function contrary to CMRL-1066 and other PEG solutions. The use of the extracellular-type solution SCOT containing PEG 20 kDa 15 g/L as colloid could be a new way to optimize graft integrity preservation and allograft outcome.

[Ischemic lesions in kidneys after extracorporeal shock wave lithotripsy demonstrated by Proton NMR spectroscopy of urine samples]

PURPOSE

The aim of this prospective study was to investigate the effect of extracorporeal shock wave lithotripsy (SWL) on kidneys of patients with pyelic stone disease. The effects of SWL were assessed by high-resolution proton nuclear magnetic resonance (HNMR) spectroscopy of urine samples.

METHODS

Twenty-three patients, aged 31-80years (mean: 55years), with pyelic stone disease were investigated before and after SWL. Multiparameter analysis was performed by HNMR spectroscopy of urine samples collected before and 5h after SWL (second miction post-SWL).

RESULTS

The most relevant resonances determined by HNMR spectroscopy were acetate, lactate, trimethylamine N-oxide and amino acids. Excretion of these markers increased significantly in comparison with pre-SWL urinary samples.

CONCLUSION

These results show that early ischemic damage occurs after SWL. Post-SWL. HNMR spectroscopy is an effective tool for noninvasive follow-up of renal damage.

A new preservation solution (SCOT 15) Improves the islet isolation process from pancreata of non-heart-beating donors: a Murine model

INTRODUCTION

Due to the organ shortage, there is increased use of organs harvested from non-heart-beating donors (NHBD). These organs have been subjected to a period of warm ischemia that is most deleterious to functional recovery. We have designed a new preservation solution, "Solution de Conservation des Organes et des Tissus" (SCOT 15; Macopharma, Tourcoing, France) which contains an extracellular ionic composition including PEG 20 kD (15 g/L) as a colloid.

METHODS

Our objective was to compare SCOT 15 with University of Wisconsin (UW) solution or islet culture medium CMRL 1066 + 1% of Bovine Serum Albumin (BSA), as the working and preservation solution for islet isolation from pancreata subjected to warm ischemia using a murine model.

RESULTS

Warm ischemia decreased the islet yield and cellular viability regardless of the preservation solution. Either when the pancreas was or was not subjected to warm ischemia, the best islet yield was obtained with SCOT 15 (P < .05 vs UW or CMRL 1066). The same results were observed for islet viability as assessed using the 3,(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test; namely, better viability with SCOT 15 as compared with UW or CMRL 1066 (P < .01).

CONCLUSION

In a murine model SCOT 15 was a better preservation solution for islet isolation than UW solution or culture medium (CMRL 1066).

Effects of the molecular weight of peg molecules (8, 20 and 35 KDA) on cell function and allograft survival prolongation in pancreatic islets transplantation

The normopotassic solution SCOT (Macopharma, France) used for the isolation of the islets of Langerhans may improve both graft function and survival. We believe that this is due to the immunoprotective properties of polyethyleneglycol (PEG) (20 kDa; 1.5 mM/L), which is contained in this solution. However, the optimal PEG chain length remains to be determined. Three extracellular type solutions (SCOT without PEG) containing various PEG-8 kDa, 20 kDa, or 35 kDa- at 1.5 mM/L were compared in vitro for viscosity and osmolarity as well as in vivo using a murine model of pancreatic islet allotransplantation. We compared the effects of the various solutions on functional cell recovery (primary nonfunction rate, PNF) and immunoprotection (allograft survival time). We showed that the viscosity of PEG 35 kDa solutions was too high for physiological use. PEG 20 kDa solution provided the best graft function (0% PNF, P < .05). PEG 8 kda and 20 kDa solutions significantly increased allograft survival time compared to the PEG 35 kDa solution (P < .05). Graft survival was similar with PEG 20 kDa and PEG 8 kDa solutions: 27.50 +/- 3.70 days versus 23.13 +/- 4.39 days (NS). However, the number of PNF with PEG 8 kDa solution (50%) was significantly higher (P < .01) than that with the PEG 20 kDa solution (0%). These preliminary results indicated that the optimal chain length at 1.5 mM/L of PEG is 20 kDa.

Effects of the molecular weight of peg molecules (8, 20 and 35 KDA) on cell function and allograft survival prolongation in pancreatic islets transplantation

The normopotassic solution SCOT (Macopharma, France) used for the isolation of the islets of Langerhans may improve both graft function and survival. We believe that this is due to the immunoprotective properties of polyethyleneglycol (PEG) (20 kDa; 1.5 mM/L), which is contained in this solution. However, the optimal PEG chain length remains to be determined. Three extracellular type solutions (SCOT without PEG) containing various PEG-8 kDa, 20 kDa, or 35 kDa- at 1.5 mM/L were compared in vitro for viscosity and osmolarity as well as in vivo using a murine model of pancreatic islet allotransplantation. We compared the effects of the various solutions on functional cell recovery (primary nonfunction rate, PNF) and immunoprotection (allograft survival time). We showed that the viscosity of PEG 35 kDa solutions was too high for physiological use. PEG 20 kDa solution provided the best graft function (0% PNF, P < .05). PEG 8 kda and 20 kDa solutions significantly increased allograft survival time compared to the PEG 35 kDa solution (P < .05). Graft survival was similar with PEG 20 kDa and PEG 8 kDa solutions: 27.50 +/- 3.70 days versus 23.13 +/- 4.39 days (NS). However, the number of PNF with PEG 8 kDa solution (50%) was significantly higher (P < .01) than that with the PEG 20 kDa solution (0%). These preliminary results indicated that the optimal chain length at 1.5 mM/L of PEG is 20 kDa.

Polyethyleneglycols and immunocamouflage of the cells tissues and organs for transplantation

In allogenic transplant the immediate immune response is due to the recipient T cell recognition of non-self molecules presented on graft resident donor antigen presenting cells. An alternative to the transplantation tolerance paradigm is based on the development of strategies which distort alloimmune recognition of the graft by antigen reactive cells of the recipient. Immunocamouflage relies on the modification of the cell membrane surface with non-immunogenic molecules creating a barrier that prevents the recognition of antigenic sites by cells and antibodies of the recipient. Polymers can spontaneously bind to cell and tissues surfaces and sterically stabilize the underlying surface from interactions with other components in the surrounding. They can be adsorbed or chemically grafted to surfaces. Polyethylene glycol (PEG) seems to be the more effective at sterically stabilizing underlying surfaces. The outstanding protection provided by this polymer has been attributed to its molecular properties, such as its low interfacial energy, its conformation, hydrophilicity and high flexibility. The main advantage of immunocamouflage, is that it directly modify the inherent immunogenicity of the donor tissue itself, using means that are strictly physicochemical in nature and do not rely on the details of activation pathways, leaving fully competent, the immune system of the recipient.

[Transplantation of cryopreserved carotids in the rabbit: effect of cryoprotective agents]

The cryopreservation of blood vessels has been carried out for some decades with variable results. In order to study the behaviour of cryopreserved allografts by using new technique of cryopreservation a study on the ultrastructure arterial tissue consequences by microscopic techniques has been carried. The graft has been harvested from carotid artery of donor rabbit, implanted to a carotid artery of a recipient rabbit and extracted at 1, 3 and 5 months after the operation. An intimal thickening and a cellular loss in the media have been observed. However, good patency has been observed in all cryopreserved allografts. Manifestations of rejection are delayed in groups with polyethylene glycol.

[Effect of preservation of the kidney on the long-term function following autotransplantation]

The consequences of ischaemia-reperfusion injury from kidney recipients on delayed graft function and graft survival still remain a matter of debate. Using an autotransplanted pig kidney model, the influence of trimetazidine added to two standard preservation solutions (Euro-Collins and University of Wisconsin) was studied. The renal parameters were analysed over a period of 12 weeks after transplantation. The degree of interstitial fibrosis, and the number of CD4, CD8 and macrophage positive cells were analysed at 2, 4-5 and 11-12 weeks after the transplantation. Glomerular filtration and sodium reabsorption were significantly more improved after cold-flush and preservation with trimetazidine-supplemented solutions than with trimetazidine-free solutions. The cytoprotective action of trimetazidine also reduced interstitial fibrosis and the number of infiltrating CD4 and CD8-positive cells. These results indicate that the condition of cold preservation may influence long-term kidney graft functions and that trimetazidine reduces to a certain extent the degree of interstitial fibrosis.

Protective effect of polyethylene glycol against prolonged cold ischemia and reperfusion injury: study in the isolated perfused rat kidney

The purpose of this study was to evaluate an intracellular solution with polyethylene glycol (PEG, molecular weight 20,000) as an impermeant, compared with University of Wisconsin (UW) and Euro-Collins (EC) solutions, after a 48-h cold storage (CS). The normothermic isolated perfused rat kidney (IPK) technique was used to assess renal function after CS. Five groups were studied: a control group (immediately reperfused, n = 10); one that received EC (n = 16); one that received UW (n = 16); and two that each received an intracellular (IC) solution, one with PEG (ICPEG, n = 16) and one without PEG (IC, n = 16). The perfusion flow rate was significantly greater in the PEG group and correlated with less significant cellular and interstitial edema and lower renal vascular resistance than in the IC, EC, and UW groups. Glomerular filtration rate was significantly higher in the PEG group during reperfusion than in the IC, EC, and UW groups. Proximal tubular functions were more efficient with PEG: fractional sodium reabsorption and total sodium reabsorption were significantly greater during reperfusion in the PEG group than in the IC, EC, and UW groups. Of greater interest is the protective effect of PEG on lipid peroxidation, which reflects ischemia/reperfusion damage. The second major effect is the dramatic ATP restoration during reperfusion, which outlines the preservation of oxidative phosphorylation after preservation by ICPEG. These results are supported by histological studies, particularly concerning brush border and mitochondrial preservation. Our results indicate that PEG is promising for cold ischemia and reperfusion injury protection.

Protection of autotransplanted pig kidneys from ischemia-reperfusion injury by polyethylene glycol

BACKGROUND

Ischemia-reperfusion injury (IRI) is often responsible for graft rejection and leads to delayed graft function of cadaveric kidneys. We have shown that adding polyethylene glycol (PEG 20M) to the preservation solutions helps protect isolated perfused pig kidneys against cold ischemia and reperfusion injury.

METHODS

We compared the effects of adding PEG to a simplified high-K+ perfusion solution of cold-stored kidneys to Euro-Collins or University of Wisconsin solutions on the function of reperfused autotransplanted pig kidneys. The left kidney was cold-flushed with the preservation solutions and stored for 48 hr at 4 degrees C before reimplantation. Creatinine clearance and fractional excretion of sodium were analyzed 2 days before surgery and over 7 days after transplantation. Histological sections were obtained 40 min after reperfusion and on day 7 after surgery.

RESULTS

Adding PEG to the perfusate significantly reduced IRI from autotransplanted pig kidneys. Creatinine clearance was significantly higher and fractional excretion of sodium was significantly lower in pigs transplanted with kidneys cold-flushed with PEG-supplemented perfusate than in those flushed with Euro-Collins or University of Wisconsin solutions. PEG supplementation also better preserved the integrity of kidney cells and markedly reduced interstitial cell infiltrates.

CONCLUSION

PEG protects against IRI and reduces early cellular inflammation. PEG may impair the recruitment and migration of leukocytes into retransplanted pig kidneys. Cold preservation of donor organs with PEG-supplemented solutions may therefore help limit IRI in human renal transplantation.

Noninvasive monitoring of citrate, acetate, lactate, and renal medullary osmolyte excretion in urine as biomarkers of exposure to ischemic reperfusion injury

Injury during the transplant process affects the alloantigen-dependent factors and the alloantigen-independent processes of "chronic" rejection. Consequently, the determination of reliable parameters for the assessment of ischemic damage is essential for the prediction of renal changes after ischemia/reperfusion injury. The aim of this study was to assess the ability of (1)H NMR spectroscopy to predict the early graft dysfunction in an ischemia/reperfusion model after preservation in two standard preservation solutions, Euro-Collins (EC) and University of Wisconsin (UW). The second aim was to specify the role of the UW solution in preventing renal medullary injury. Urine and plasma samples from three experimental groups were examined during 2 weeks: control group (n = 5), EC group (cold flushed and 48-h cold storage of kidney in EC and autotransplantation, n = 12), and UW group (cold flushed and 48-h cold storage of kidney in UW and autotransplantation; n = 12). We also examined these kidneys 30-40 min after implantation and on the sacrifice day. Creatinine clearance was significantly reduced in the EC group during the second week. Fractional excretion of sodium and urine N-acetyl-beta-d-glucosaminidase activity were improved but not significantly different in the preserved groups. Urinary concentrations of the alpha-class glutathione S-transferase were significantly greater in the EC group during the first week after transplantation. The most relevant resonances for evaluating renal function after transplantation determined by (1)H NMR spectroscopy were those arising from citrate, dimethylamine (DMA), lactate, and acetate in urine and trimethylamine-N-oxide (TMAO) in urine and plasma. These findings suggest that graft dysfunction is associated with damage to the renal medulla determined by TMAO release in urine and plasma associated with DMA and acetate excretion. Citrate is also a urinary marker that can discriminate kidneys with a favorable evolution. Our results suggest that (1)H NMR spectroscopy is an efficient technique for detecting ischemic damage when accurate and precise data on graft injury is required. In addition, this study outlines the specific impact of the UW solution against injury to the renal medulla.

Kidney retrieval conditions influence damage to renal medulla: evaluation by proton nuclear magnetic resonance (NMR) pectroscopy

In the present investigation, the influence of retrieval condition on medullary damage in kidneys was assessed. The isolated perfused pig kidney was used to assess initial renal function from multiorgan donors or single organ donors after cold flush and 24 h cold storage preservation with two preservation solutions: Euro-Collins and University of Wisconsin solutions. Kidneys flushed with cold heparinized saline and immediately perfused were used as a control group. Kidneys were perfused for 90 min at 37.5 degrees C and renal perfusion flow rate, glomerular filtration rate, tubular reabsorption of Na+ and lactate dehydrogenase and N-acetyl-beta-D-glucosaminidase excretion were determined. Ischaemia reperfusion impairment was also determined by 1H NMR (proton nuclear magnetic resonance) spectroscopy. Renal function was significantly decreased in experimental groups when compared to the control group, but there was no significant difference between experimental groups after 24 h cold storage. The release of lactate dehydrogenase in the effluent and the urinary excretion of N-acetyl-beta-D-glucosaminidase were not significantly different after 24 h cold storage. The most relevant resonances determined by 1H NMR spectroscopy were citrate, trimethylamine-N-oxide, lactate, acetate and amino acids. Excretion of these markers was significantly different when compared to biochemical markers. A resonance P (Peak) detected particularly in Euro-Collins solution multiorgan donors after 24 h cold storage was identified and well correlated to renal dysfunction. N-acetyl-beta-D-glucosaminidase spectroscopy, which is a non-invasive and non-destructive technique, is more efficient to assess renal damage than conventional histology and biochemical analysis.

Citrate, acetate and renal medullary osmolyte excretion in urine as predictor of renal changes after cold ischaemia and transplantation

In organ transplantation, the determination of reliable parameters to assess ischaemic damage is essential to predict renal injury after preservation. The aim of this study was to assess renal medullary injury by 1H NMR (proton nuclear magnetic resonance) spectroscopy after preservation and reperfusion. Three experimental groups of pigs were examined during a 2-week period: control group (n = 4), Euro-Collins group (EC) (cold flushed and 48 h cold storage of kidney in EC and autotransplantation, n = 7), and University of Wisconsin (UW) group (cold flushed and 48 h cold storage of kidney in UW and autotransplantation, n = 7). Creatinine and urea were improved in the two cold stored groups. The most relevant resonances determined by 1H NMR spectroscopy after transplantation were those arising from citrate and acetate in urine and trimethylamine-N-oxide (TMAO) in urine and plasma. We demonstrate that graft dysfunction is associated with damage to the renal medulla as determined by TMAO release in urine and plasma. Conversely, citrate excretion can discriminate kidneys with favourable outcome. This study outlines the specific and beneficial impact of UW solution on renal preservation and suggests that 1H NMR spectroscopy is efficient both to detect ischaemic damage of preserved kidneys and to discriminate the preservation quality between different preservation solutions.

A new approach to the evaluation of liver graft function by nuclear magnetic resonance spectroscopy. A comparative study between Euro-Collins and University of Wisconsin solutions

The incidence of primary dysfunction or non-function of liver grafts still occurs at an unacceptable rate and the identification of new markers of graft viability and metabolic capacity is essential. Proton nuclear magnetic resonance (H NMR) spectroscopy has previously shown potential in the evaluation of renal allograft dysfunction after ischaemia reperfusion. The aim of this study was to compare liver graft function in a rat isolated perfused liver model after 24 hours of preservation in either Euro-Collins (EC) or University of Wisconsin (UW) solutions. Livers were reperfused for 90 min with a modified Krebs-Henseleit medium. Functional parameters measured were: pressure and resistances, bile and transaminase production. The production of lactate, pyruvate, citrate and succinate, beta-hydroxybutyrate and aceto-acetate was measured by H NMR. There was a significant difference in both haemodynamics and bile production in favour of the UW group. The transaminases were similar in the two groups. Measurements of citrate, succinate and ketone bodies by H NMR were all higher in the UW group. These markers indicate better metabolic function of these grafts during reperfusion. In conclusion, discriminating different hepatic metabolic pathways is possible and easy by H NMR and can be used to assess both the preservation quality of liver grafts and their functional recovery.

Influence of retrieval conditions on renal medulla injury: evaluation by proton NMR spectroscopy in an isolated perfused pig kidney model

BACKGROUND

Delayed graft function (DGF) has remained an important complication after renal transplantation. The exact causes of DGF remain to be clarified, particularly the impact of retrieval conditions and preservation factors. In the present investigation, (1)HNMR spectroscopy of urine was assessed in order to detect the influence of retrieval condition on renal medulla damage.

METHODS

The isolated perfused pig kidney (IPK) was used to assess initial renal function from multiorgan donors (MOD) or single organ donors (SOD) after in situ cold flush and 24-h cold storage (CS) preservation with two standard preservation solutions: Euro-Collins (EC) and University of Wisconsin (UW) solutions. Kidneys flushed with cold heparinized saline and immediately perfused were used as the control group. Kidneys were perfused for 90 min at 37.5 degrees C for functional evaluation. During reperfusion, renal perfusion flow rate (PF) was measured. Glomerular filtration rate (GFR), tubular reabsorption of Na(+), and lactate dehydrogenase (LDH) and N-acetyl-beta-d-glucosaminidase (NAG) excretions were determined. Ischemia-reperfusion impairment was also determined by histological techniques and (1)HNMR spectroscopy.

RESULTS

PF, GFR, and tubular reabsorption of Na(+) were significantly decreased in experimental groups when compared to the control group but there was no significant difference between experimental SOD groups. GFR was significantly greater in UW-MOD than in EC-MOD and tubular reabsorption of Na(+) was significantly greater in UW-MOD than in EC-MOD after 45 min of reperfusion. The release of LDH in the effluent and the urinary excretion of NAG were not significantly different after 24-h CS in the various experimental groups. The most relevant resonances determined by (1)HNMR spectroscopy were citrate, trimethylamine-N-oxide, lactate, acetate, and amino acids. Excretion of these markers was significantly different when compared to biochemical markers. A resonance (P) detected particularly in EC-MOD after 24-h CS was identified and well correlated to renal dysfunction. Histological study showed that ultrastructural damage and mitochondrial injury were more pronounced in the EC-MOD group.

CONCLUSION

These results show that retrieval condition influences renal medullary damage. NMR spectroscopy, which is a noninvasive and nondestructive technique, is more efficient in assessing renal damage than conventional histology and biochemical analysis.

Pharmacological limitation of damage to renal medulla after cold storage and transplantation by trimetazidine

Delayed graft function remains an important complication after renal transplantation. In this study, we investigated the influence of trimetazidine (TMZ), a cytoprotective agent, on renal medullary damage after prolonged preservation and autotransplantation. Pig kidneys were cold-flushed and preserved (48 h at 4 degrees C) with two standard renal preservation solutions Euro-Collins and University of Wisconsin supplemented or not with TMZ (10(-6) M). Analysis of plasma and urine from 48-h-cold-stored and autotransplanted kidneys was performed with biochemical methods and proton NMR spectroscopy. Histological study by light and electron microscopy was performed after reperfusion (30-40 min) and on day 14. The results showed that the preservation in either Euro-Collins or University of Wisconsin solution containing TMZ improved significantly glomerular filtration rate compared with kidneys preserved without TMZ. TMZ significantly reduced renal medullary damage, evidenced by decreased excretion of trimethylamine-N-oxide, dimethylamine, dimethylglycine, and acetate in urine. Proximal tubular injury in TMZ-free groups was assessed by significantly greater Na(+) excretion, amino aciduria, and lactic aciduria than in TMZ-supplemented groups. Urinary concentrating ability was significantly improved in TMZ-preserved groups compared with TMZ-free groups. In TMZ-supplemented groups, there was also a greater excretion of citrate, which is a citric acid cycle metabolite. An extensive reduction in apical brush border of tubular cells, notably those of the proximal tubules, was noted in TMZ-free groups. This study clearly shows that TMZ has a beneficial action on in vivo renal preservation and its major impact is the vulnerable renal medulla.

Replacement of a tracheal segment by a mixed graft (aorta and prosthesis): an experimental study in rabbits

OBJECTIVE

To develop a new graft and to verify its technical feasibility, viability, and ability to reduce the risk of infection by interposition of an aortic segment between the airway and the prosthetic component of the graft.

DESIGN

Experimental study.

SETTING

Multicentre study, France.

ANIMALS

38 New Zealand rabbits.

INTRODUCTION

A 1 cm aortic segment was obtained from the thoracic aorta of a rabbit and cryopreserved or stored at +4 degrees C. The aortic segment, surrounded by a ringed expanded polytetrafluoroethylene (ePTFE) prosthesis was used to replace 1 cm of cervical trachea in two groups of rabbits, either with cryopreserved or fresh aorta.

MAIN OUTCOME MEASURES

Macroscopic, microbiological, and histological studies four months later.

RESULTS

12/20 animals in the cryopreserved group survived and 13/18 in those had had fresh aorta inserted. Partial or total necrosis of the aortic muscular layer was replaced by connective tissue, which was a guide for epithelialisation from the anastomoses.

CONCLUSION

This new graft is worthy of further investigation, as it is technically feasible and easy to insert.

Early evaluation of renal reperfusion injury after prolonged cold storage using proton nuclear magnetic resonance spectroscopy

BACKGROUND

Proton nuclear magnetic resonance (NMR) spectroscopy can be used as a non-invasive tool to measure renal damage. In the present investigation, proton NMR spectroscopy of urine was assessed in order to detect cellular damage after different periods of cold ischaemia in two standard preservation solutions.

METHODS

The isolated perfused pig kidney was used to assess initial renal function after in situ cold flush and cold storage (CS) for 24 or 48 h in two standard preservation solutions: EuroCollins (EC) and University of Wisconsin (UW) solutions. Kidneys flushed with cold heparinized saline and immediately perfused were used as a control group. Kidneys were perfused for 2 h at 37.5 degrees C for functional evaluation. During reperfusion, renal perfusion flow rate was measured. Glomerular filtration rate (GFR), tubular reabsorption of sodium ions, and lactate dehydrogenase (LDH) and N-acetyl-beta-D-glucosaminidase (NAG) excretion were determined. Impairment caused by ischaemia and reperfusion was also determined by histological techniques and proton NMR spectroscopy.

RESULTS

The perfusion flow rate, GFR and tubular reabsorption of sodium were significantly decreased in experimental groups compared with the control group. There was no significant difference between experimental groups after 24 h of CS. The perfusion flow rate was significantly decreased in the EC group after 48 h of cold ischaemia compared with that in the UW group. After 48 h of CS, GFR and tubular reabsorption of sodium were significantly reduced in the EC group compared with those in the UW group. The release of LDH into the effluent and the urinary excretion of NAG were not significantly different after 24 h of CS. After more than 45 and 60 min of reperfusion respectively, LDH and NAG excretion was no different in the 48-h CS groups. The most relevant resonances determined by proton NMR spectroscopy were of citrate, trimethylamine-N-oxide, lactate, acetate and amino acids. Excretion of these markers was significantly more accurate and efficient to assess renal ischaemia-reperfusion injury than that of biochemical markers. A resonance (P) detected particularly in the EC group after 48 h of CS was identified and correlated well with renal dysfunction. After CS for 48 h and 2 h of reperfusion, renal injury was histologically more pronounced in EC groups than in UW groups. However, the difference was not significant after CS for 24 h.

CONCLUSION

NMR spectroscopy, which is a non-invasive and non-destructive technique, is more accurate and efficient when assessing kidney damage after cold ischaemia and reperfusion when compared to conventional histological and biochemical analysis.

Renoprotective effects of trimetazidine against ischemia-reperfusion injury and cold storage preservation: a preliminary study

BACKGROUND

Initial ischemia-reperfusion injury is associated with organ retrieval, storage, and transplantation adversely affects early graft function and influences the development of chronic graft dysfunction. We have recently shown that the protective agent trimetazidine (TMZ) added to preservation solutions: Euro-collins (EC) and University of Wisconsin (UW) was efficient to protect kidneys from ischemia-reperfusion injury in an isolated perfused kidney model. We extended these observations to investigate the role of this drug in the development and progression of organ dysfunction in the autotransplant pig kidney model.

METHODS

Five experimental groups were studied. After 48-hr cold preservation, autotransplantation and immediate controlateral nephrectomy was then performed in group EC (EC+placebo (n=8), EC+TMZ (n=8), UW+placebo (n=7), and (UW+TMZ) (n=7) and compared with control group (uninephrectomized, n=4) during 14 days. Blood and urine samples were collected for the measurement of creatinine and blood urea nitrogen on postoperative days 1, 3, 5, 7, 11, and 14. Histological analysis was performed after reperfusion and at day 14.

RESULTS

Survivals were 100% in group B and D versus 42% in group A and 57% in group C. Urine production occurred earlier after autotransplantation from TMZ preserved kidneys than in placebo preserved groups. Peak creat and blood urea nitrogen was significantly greater in groups B and D than in groups A and C. TMZ was also efficient both to reduce ischemia-reperfusion injury and to decrease cellular infiltration.

CONCLUSION

These results support the beneficial effect of TMZ against ischemia-reperfusion injury and its early effects on grafts in the form of delayed graft function and decreased graft survival. In addition, TMZ reduces inflammatory cellular infiltration in the renal parenchyma.

Efficiency of trimetazidine in renal dysfunction secondary to cold ischemia-reperfusion injury: a proposed addition to University of Wisconsin solution

Nonspecific injury in cadaveric renal transplants adversely affects early graft function and influences long-term graft survival after organ transplantation. Trimetazidine (TMZ) has been reported to exert a protective action against normothermic ischemia and reperfusion injury in several experimental and clinical studies. In an isolated perfused pig kidney model, we investigated the effects of TMZ added to University of Wisconsin solution (UW) during 48 or 72 h of cold storage (CS) and the consequence during reperfusion. Under all conditions tested renal perfusate flow rate (PFR), renal functions, and tubular injury markers were determined during a 120-min perfusion period. Lipid peroxidation and histological examination (optical and electron microscopy) were also determined after CS and reperfusion. The addition of TMZ (10(-6) M) to the UW solution improved dramatically the quality of preserved kidneys and consequently the functional recovery during reperfusion. TMZ + UW also significantly had a protecting role against reperfusion injury and lipid peroxidation when compared to UW alone. These results were correlated with both a better preservation of the proximal brush border membrane and reduced cellular and mitochondrial swelling. These results also suggested that the TMZ-induced renoprotection correlated well with the observed decrease membrane lipid peroxidation. Therefore, trimetazidine may be useful for clinical kidney graft preservation.

Trimetazidine reverses deleterious effects of ischemia-reperfusion in the isolated perfused pig kidney model

BACKGROUND

Delayed graft function has remained an important complication after renal transplantation.

METHODS

The purpose of this study was to evaluate Euro-Collins (EC) plus trimetazidine (TMZ) in comparison with standard EC solution after 24- or 48-hour cold storage. The normothermic isolated perfused pig kidney technique combined with proton nuclear magnetic spectroscopy was used.

RESULTS

The study verified that TMZ plus EC had a beneficial preservation effect over EC in terms of better perfusate flow rate at both 24 and 48 h (p < 0.01 and p < 0.001, respectively). In addition, TMZ also was beneficial in terms of increased glomerular filtration rate, better proximal tubular functions, and less tubular injury markers. Lipid peroxidation, evaluated by malondialdehyde renal tissue levels, was decreased in kidney homogenates preserved with TMZ, particularly after 48-hour cold storage. Citrate excretion which reflects a better intracellular pH regulation was detected in urine from kidneys preserved with TMZ. Histological data paralleled findings of the above when comparing cellular injury factors such as vacuolization, necrosis, tubular structure, and interstitial edema.

CONCLUSION

These results indicate that, under the conditions of our experiments, the addition of TMZ to EC solution increased the preservation quality of kidneys particularly after prolonged cold ischemia.

Lipid peroxidation after cold storage and normothermic reperfusion: the effect of trimetazidine

Ischemia reperfusion injury is still a leading cause of early graft dysfunction after transplantation. Trimetazidine (TMZ) has been postulated to be protective against renal damage from oxygen free radicals. The aim of this study was to assess the effect TMZ during cold storage (CS) and normothermic reperfusion in an isolated perfused pig kidney model. Three groups were studied: control group, immediately perfused (G0), 48 h CS in Euro-Collins solution (G1), and 48 h CS in Euro-Collins solution plus TMZ (G2). Glomerular filtration rate (GFR) and fractional sodium reabsorption (FRNa+) were calculated during reperfusion from urine and perfusate samples. Lipid peroxidation was determined by the renal tissue level of Schiff bases (SB) and malondialdehyde (MDA) after reperfusion. A histological evaluation was performed after reperfusion. Renal function was significantly improved and lipid peroxidation reduced after preservation in Euro-Collins solution plus TMZ. Functional data were closely related to histological damage. In conclusion, TMZ is a useful protective agent against renal damage induced by CS.

Effects of trimetazidine on lipid peroxidation and phosphorus metabolites during cold storage and reperfusion of isolated perfused rat kidneys

This study was undertaken to evaluate the effect of trimetazidine (TMZ) during cold storage (CS) and the consequence during normothermic reperfusion in an isolated perfused rat kidney model (IPK). IPK was used to assess the rate of perfusion flow, the ratio of ATP to inorganic phosphate (ATP/Pi) as a reflection of the energetic status during reperfusion, intracellular pH (pHi), tissue water content and malondialdehyde (MDA) tissue levels in four different preservation solutions after 48-hr preservation at 4 degreesC and 2-hr reperfusion at 37.5 degreesC: EuroCollins (EC), University of Wisconsin (UW), EC plus TMZ (10(-)6 M) (EC + TMZ) and UW plus TMZ (10(-)6 M) (UW + TMZ). When TMZ was added to the preservation solutions, perfusion flow rate (PFR) was significantly improved during reperfusion. Tissue water content, which reflected tissue edema, was significantly lower in TMZ groups than in groups without TMZ during both CS and reperfusion conditions. In TMZ groups, ATP/Pi ratio was also significantly improved during CS and reperfusion. In addition, TMZ lowered the pHi both during preservation and after reperfusion. MDA renal tissue level significantly decreased with TMZ both during the preservation period and after reperfusion. These overall results strongly suggested that TMZ contributes to renal protection from cold ischemia-reperfusion injury in this IPK model, especially when TMZ was added to UW solution and during prolonged hypothermic ischemia.

Trimetazidine prevents renal injury in the isolated perfused pig kidney exposed to prolonged cold ischemia

BACKGROUND

Ischemia caused by cold storage (CS) and reperfusion of the kidney is often responsible for delayed graft function after transplantation. Significant attention has been focused on the cascade of events involved in ischemia-reperfusion injury, with the objective of identifying drugs to ameliorate the functional damage that occurs.

METHODS

The purpose of this study was to evaluate the renal function of isolated perfused pig kidneys after 48 hr of CS with Euro-Collins (EC) solution plus trimetazidine (EC+TMZ), standard EC solution, or University of Wisconsin (UW) solution. Normothermic isolated perfused pig kidneys were randomized into five experimental groups: (A) control group (cold flush with cold heparinized saline and immediately reperfused; n=6); (B) cold flush with cold heparinized saline with TMZ (10(-6) M), n=6; (C) 48 hr of CS with EC and reperfusion (n=8); (D) 48 hr of CS with EC+TMZ alone and reperfusion (n=8); (E) 48 hr of CS with UW and reperfusion (n=8). Proton nuclear magnetic resonance spectroscopy and biochemical studies were performed for the functional evaluation during reperfusion. Lipid peroxidation was also determined. Histological examination (optical and electron microscopy) was performed after CS and reperfusion.

RESULTS

Using TMZ, the renal perfusate flow rate as well as the glomerular filtration rate and proximal tubular function were significantly improved. This improvement of renal function during reperfusion was correlated with a less significant cellular and interstitial edema. In addition, tubular injury markers were significantly lower in the group preserved with EC+TMZ, and TMZ reduced lipid peroxidation dramatically during reperfusion.

CONCLUSIONS

The addition of TMZ to the EC solution increased the preservation quality and renal tubular function, and gave protection from reperfusion injury better than EC alone or UW. These results strongly suggest that TMZ has a cytoprotective effect and may therefore be useful for kidney preservation.

Evaluation of injury preservation in pig kidney cold storage by proton nuclear magnetic resonance spectroscopy of urine

The isolated perfused kidney (IPK) model from pig was used to assess initial renal functions after cold flush and a 24- and 48-hour cold storage preservation (CSP) with Euro-Collins (EC) and to determine ischemia reperfusion (IR) impairment by biochemical, histological and proton nuclear magnetic resonance (NMR) spectroscopy of urine analysis. Eighteen pig kidneys were used. There were three experimental groups: Group 1--control kidneys flushed with cold heparinized saline, Group 2--cold flush followed by 24-hour CSP and reperfusion, Group 3--cold flush followed by 48-hour CSP and reperfusion. Kidneys were perfused for 2-hour at 37.5C for the determination of exogenous creatinine clearance (CCr), perfusion flow rate (PFR) and tubular function. Functional parameters and histological data are very poor after prolonged cold ischemia. Levels of tubular injury markers determined by proton NMR spectroscopy analysis were significantly higher with a longer ischemic time correlating well with the increased degree of renal functional and anatomic impairment. A new peak detected only in the 48-hour ischemic group was identified. In this model, proton NMR spectroscopy may be a useful technique in the evaluation of both new preservation solutions or methods.

Evaluation of normothermic ischemia and simple cold preservation injury in pig kidney by proton nuclear magnetic resonance spectroscopy

The isolated perfused pig kidney (IPK) model was used to mimic the non-heart-beating donor situation. This model was performed to assess initial renal functions after normothermic ischemia, cold flush, and 24 hr cold-storage preservation (CSP) with Euro-Collins and to determine normothermic ischemia and reperfusion impairment by biochemical, histological, and proton nuclear magnetic resonance (NMR) spectroscopy analysis. Twenty-four pig kidneys were used. There were three experimental groups: Group 1 (G1), control kidneys flushed with cold heparinized saline and immediately perfused; Group 2 (G2), cold flush followed by 24 hr CSP and reperfusion; and Group 3 (G3), 30 min of normothermic ischemia followed by cold flush and 24 hr CSP and reperfusion. Kidneys were perfused for 2 hr at 37.5 degrees C for functional evaluation. Perfusate flow rate is significantly different for G3 (P < 0.01). Glomerular filtration rate is less in G3 (P < 0.05). Fractional reabsorptions of sodium (FRNa+) and glucose (Glc) excretion in urine are different in G3 (P < 0.01 and P < 0.05, respectively). Amino acid excretion in NMR spectroscopy was higher in G3 (P < 0.05). Elevated levels of trimethylamine-N-oxide (TMAO) and lactate (Lac) were detected by proton NMR spectroscopy in G2 and particularly G3. A peak is present in G3 and related with poor glomerular and tubular functions and worse histological data. Malondialdehyde tissue level was higher in G3. This study shows that the IPK with proton NMR spectroscopy may be a useful method in the evaluation of kidneys after cold ischemia and transplantation. This model might be suitable for a variety of experimental protocols, particularly to improve functional performance after ischemia and reperfusion.