Comparison of static versus pulsatile preservation of matched-paired kidneys

Maximizing kidneys for transplantation using machine perfusion: from the past to the future: A comprehensive systematic review and meta-analysis

BACKGROUND

The two main options for renal allograft preservation are static cold storage (CS) and machine perfusion (MP). There has been considerably increased interest in MP preservation of kidneys, however conflicting evidence regarding its efficacy and associated costs have impacted its scale of clinical uptake. Additionally, there is no clear consensus regarding oxygenation, and hypo- or normothermia, in conjunction with MP, and its mechanisms of action are also debated. The primary aims of this article were to elucidate the benefits of MP preservation with and without oxygenation, and/or under normothermic conditions, when compared with CS prior to deceased donor kidney transplantation.

METHODS

Clinical (observational studies and prospective trials) and animal (experimental) articles exploring the use of renal MP were assessed (EMBASE, Medline, and Cochrane databases). Meta-analyses were conducted for the comparisons between hypothermic MP (hypothermic machine perfusion [HMP]) and CS (human studies) and normothermic MP (warm (normothermic) perfusion [WP]) compared with CS or HMP (animal studies). The primary outcome was allograft function. Secondary outcomes included graft and patient survival, acute rejection and parameters of tubular, glomerular and endothelial function. Subgroup analyses were conducted in expanded criteria (ECD) and donation after circulatory (DCD) death donors.

RESULTS

A total of 101 studies (63 human and 38 animal) were included. There was a lower rate of delayed graft function in recipients with HMP donor grafts compared with CS kidneys (RR 0.77; 95% CI 0.69-0.87). Primary nonfunction (PNF) was reduced in ECD kidneys preserved by HMP (RR 0.28; 95% CI 0.09-0.89). Renal function in animal studies was significantly better in WP kidneys compared with both HMP (standardized mean difference [SMD] of peak creatinine 1.66; 95% CI 3.19 to 0.14) and CS (SMD of peak creatinine 1.72; 95% CI 3.09 to 0.34). MP improves renal preservation through the better maintenance of tubular, glomerular, and endothelial function and integrity.

CONCLUSIONS

HMP improves short-term outcomes after renal transplantation, with a less clear effect in the longer-term. There is considerable room for modification of the process to assess whether superior outcomes can be achieved through oxygenation, perfusion fluid manipulation, and alteration of perfusion temperature. In particular, correlative experimental (animal) data provides strong support for more clinical trials investigating normothermic MP.

Hypothermic machine perfusion of kidneys retrieved from standard and high-risk donors

Hypothermic machine perfusion (HMP) of kidneys is a long-established alternative to static cold storage and has been suggested to be a better preservation method. Today, as our deceased donor profile continues to change towards higher-risk kidneys of lower quality, we are confronted with the limits of cold storage. Interest in HMP as a preservation technique is on the rise. Furthermore, HMP also creates a window of opportunity during which to assess the viability and quality of the graft before transplantation. The technology might also provide a platform during which the graft could be actively repaired, making it particularly attractive for higher-risk kidneys. We review the current evidence on HMP in kidney transplantation and provide an outlook for the use of the technology in the years to come.

Perfusion storage reduces apoptosis in a porcine kidney model of donation after cardiac death

BACKGROUND

Donation after cardiac death (DCD) kidneys suffer a high incidence of delayed graft function attributable to warm ischemia and cold ischemia (CI). Neither the mechanism of injury nor type of cell death has been described. Clinical studies suggest that perfusion storage (PS) of DCD kidneys may reduce injury although the mechanism of protection is unknown. In a porcine model of DCD, we hypothesized that DCD kidneys have increased caspase-1 due to warm ischemia (WI) and increased caspase-3 and apoptosis due to CI.

METHODS

Male Yorkshire pigs subjected to cardiac death were perfused with cold University of Wisconsin solution. The perfused kidneys were removed and stored in cold University of Wisconsin solution for 24 hr. Kidney biopsies were obtained before cardiac death and at 0 and 24 hr of CI.

RESULTS

There was an increase in caspase-1 activity due to WI before cold preservation. CI was associated with a massive increase in apoptosis, caspase-3/7 activity, and caspase-3 protein expression. Next, we hypothesized that PS would protect against apoptosis. We compared DCD kidneys subjected to static versus PS for 24 hr. PS significantly reduced proximal tubular apoptosis and was associated with increased B-cell lymphoma-extra large, and hypoxia-inducible transcription factor-1α.

CONCLUSIONS

These findings suggest that in DCD kidneys, WI preferentially activates caspase-1, whereas CI activates caspase-3 and causes apoptosis. PS may protect DCD kidneys through activation of antiapoptotic pathways involving B-cell lymphoma-extra large and hypoxia-inducible transcription factor-1α.

Machine perfusion or cold storage in organ transplantation: indication, mechanisms, and future perspectives

Most organs are currently preserved by cold storage (CS) prior to transplantation. However, as more so called marginal donor organs are utilized, machine perfusion has regained clinical interest. Recent studies have demonstrated advantages of pulsatile perfusion over CS preservation for kidney transplantation. However, it remains unclear whether there is a significant benefit of one preservation method over the other in general, or, whether the utilization of particular preservation approaches needs to be linked to organ characteristics. Proposed protective mechanisms of pulsatile perfusion remain largely obscure. It can be speculated that pulsatile perfusion may not only provide nutrition and facilitate the elimination of toxins but also trigger protective mechanisms leading to the amelioration of innate immune responses. Those aspects may be of particular relevance when utilizing grafts with suboptimal quality which may have an increased vulnerability to ischemia/reperfusion injury and compromised repair mechanisms. This review aims to enunciate the principles of organ perfusion and preservation as they relate to indication, aspects of organ protection and to highlight future developments.

Preliminary findings on the use of pulsatile machine reperfusion of a placenta to improve the cord blood collection yield including primitive hematopoietic stem cell fractions

BACKGROUND

Umbilical cord blood (CB) use is limited in most adults since the mean amount of hematopoietic stem cells (HSCs) collected is generally insufficient to engraft successfully. This study demonstrates for the first time the feasibility of pulsatile machine placenta reperfusion (PMPR), which significantly improves CB collection quantity and quality compared to standard collection methods.

STUDY DESIGN AND METHODS

PMPR was performed on eight delivered placentas up to 39 hours after venipuncture-based collection. PMPR was performed on average for 26 (20-30) minutes, 17 hours after delivery (6.25-39), using perfusate approved for donated organ reperfusion. Both PMPR and conventional collection-derived CB cells were analyzed using immunophenotyping and colony assays.

RESULTS

The combination of PMPR and the conventional venipuncture method yielded a mean of 1.5-, 4.9-, 11-, 7.5-, 7.5-, and 7.7-fold increased number of total mononuclear, CD34+, CD34+/CD38-, CD133+, CD133+/CD34+, and CD133+/CD34- cells, respectively, compared to conventional venipuncture alone. CB cells obtained by PMPR alone generally demonstrated a significant increase in percentages of primitive HSC phenotype with equivalent cell viability between PMPR and venipuncture.

CONCLUSION

This article demonstrates for the first time that CB can be collected up to 39 hours after delivery with PMPR while maximizing CB collection including HSCs with primitive phenotypes.

Assessment of cadaveric organ viability during pulsatile perfusion using infrared imaging

Assessment of pulsatile perfusion (PP) is limited to measurements of flow (V) and resistance (R). We investigated infrared (IR) imaging during PP as a means for precise organ assessment. IR was used to monitor 10 porcine kidneys during 18 hr of PP in an uncontrolled Donation after Cardiac Death model. An IR camera (Lockheed Martin) was focused on the anterior surfaces of the kidneys. The degree of temperature homogeneity was compared with standard measurements of V and R. IR thermal images correlated with V and R (R=0.92, P<0.001). IR detected an increase in homogeneity during PP by comparing standard deviation differences before and after PP (P=0.002), which was not evident by standard measurements of V and R. Finally, IR assessment allowed for measurement of dynamic changes in perfusion.

Machine perfusion preservation improves renal allograft survival

Machine perfusion (MP) has been used as the kidney preservation method in our center for over 10 years. The first, small (n = 74) prospective, single-blinded randomized study comparing MP and Cold Storage (CS) showed that the incidence of delayed graft function was higher after CS. There have been no reports in the literature on the effect of storage modality on long-term function of renal allografts. This paper presents an analysis of long-term results of renal transplantation in 415 patients operated on between 1994 and 1999. Of those, 227 kidneys were MP-stored prior to KTx. The control group consisted of 188 CS kidney transplants. Kidneys were not randomized to MP or to CS. Donor demographics, medical and biochemical data, cold ischemia time, HLA match and recipient data were collected. Standard triple-drug immunosuppression was administered to both groups. Mortality, graft survival and incidence of return to hemodialysis treatment were analyzed. Despite longer cold ischemia time and poorer donor hemodynamics in MP group, 5-year Kaplan-Meier graft survival was better in MP-stored than in CS-stored kidneys (68.2% vs. 54.2%, p = 0.02).

CONCLUSION

In this nonrandomized analysis, kidney storage by MP improved graft survival and reduced the number of patients who returned to dialysis.

Pulsatile machine perfusion vs. cold storage of kidneys for transplantation: a rapid and systematic review

OBJECTIVE

To identify and prioritize key areas for further research in kidney preservation systems.

MATERIALS AND METHODS

We conducted a systematic review and meta-analysis of the effectiveness of machine perfusion and cold storage techniques in reducing delayed graft function (DGF) and improving graft survival in recipients of kidneys from beating and non-heart-beating donors. Literature quantifying the link between DGF and graft survival was used to evaluate the potential long-term impact of machine perfusion and cold storage systems. Cox proportional hazards modelling was used to predict graft survival and graft years gained over 10 yr. Monte Carlo sensitivity analysis was conducted to evaluate stochastic uncertainties within the model.

RESULTS

Machine perfusion leads to a relative risk of DGF of approximately 80% (67%, 96%) compared with cold storage, although the evidence base is limited in quality and study size. Direct evidence on graft survival at 1 yr demonstrates no statistically significant difference between machine perfusion and cold storage. Predictions based upon quantifying the link between DGF and graft survival suggest potential improvements of between 0 and 6% at 10 yr.

DISCUSSION

Studies of high methodological quality and sufficient size are required to determine whether machine preservation leads to reduce rates of DGF. Predicted impact on graft survival implies that direct evidence would require a large population followed up over a long period of time. Registry database analysis supported by validation of the link between DGF and graft survival may be preferable and more feasible than randomized controlled trials.

The use of expanded criteria cadaver and live donor kidneys for transplantation

The use of expanded criteria donors (non-traditional donors) can help lessen the current shortage of kidneys available for transplantation. The use of older donors has accounted for a large measure of the increase in the organ donation rate; however, the most significant factors found to impact on transplant success negatively traditionally have been shown to be extremes of donor age and last-hour urine output. Less significant variables affecting success rates are average systolic blood pressure, terminal serum creatinine, and days of hospitalization. With the appropriate selection of organs from expanded donors, acceptable outcomes can be obtained. When living donors are selected properly, kidneys with anatomic variants without pathologic significance can be used safely. Kidneys with a heightened potential for the development of progressive disease should not be transplanted. Efforts to decrease the cold ischemia time by increasing the use of kidneys from expanded criteria donors may improve the outcome of transplantation further. Advances in surgical techniques, preservation solutions, and methods for predicting eventual long-term renal function in kidneys from expanded donors will be critical in allowing precise selection criteria for kidneys for transplantation, resulting in the optimum use of a scarce and precious resource. Until options such as xenotransplantation become clinically feasible, the challenge will be to identify which donor organs previously considered suboptimal can be used safely to expand the organ donor pool.