Maximilian Polyak

The influence of pulsatile preservation on renal transplantation in the 1990s.

BACKGROUND Unlike simple cold storage (CS), pulsatile machine preservation (MP) of kidneys for transplantation permits pharmacologic manipulation of the perfusate and aids in the pretransplant assessment of the kidney graft. These characteristics of MP may have importance in the era of increasing use of extended criteria donor kidneys. The overall aim of this article is to critically assess practices at our preservation unit with respect to graft function. Specific aims are to (1) compare the influence of MP versus CS on graft function, (2) determine which pretransplant variables have significance in pretransplant assessment, and (3) determine whether pharmacologic manipulation during MP is advantageous. METHODS There were 650 consecutive kidneys preserved in our laboratory between January 1, 1993 and March 1, 999, by either MP or CS. All MP kidneys were preserved by continuous hypothermic pulsatile perfusion using Belzer-MPS or Belzer II solution. Perfusion parameters and electrolytes were measured serially during pulsatile perfusion. All CS kidneys were stored in University of Wisconsin solution. All kidneys obtained from donors exhibiting extended criteria features underwent pretransplant frozen section biopsies. Transmission electron microscopy (EM) was performed on a subset of kidneys undergoing pharmacologic manipulation. Four agents were assessed prospectively for their ability to influence MP characteristics when added to perfusate: PGE1, trifluoperazine, verapamil, and papaverine. RESULTS MP was associated with improved immediate, 1-, and 2-year graft function and reduced length of initial hospital stay when compared with CS grafts. Changes in the machine perfusion variables flow and resistance, and the [Ca++] in perfusate, were significantly associated with delayed graft function (DGF) after the transplant. Biopsy information was not predictive of DGF. The addition of PGE1 to perfusate improved MP characteristics, reduced the release of [Ca++] into perfusate, and ameliorated mitochondrial ischemic injury in transmission EM images. Early graft function was improved in the presence of PGE1+MP, compared with function in the presence of other pharmacologic agents or CS alone. CONCLUSIONS MP is associated with improved early and long term renal function. Moreover, PGE1 augments MP in improving graft function. The combination of MP+PGE1 may be important in optimizing the ability to use extended donor criteria kidneys and, thereby, improve the overall efficiency of cadaveric renal transplantation.

Cold Pulsatile Perfusion of Pediatric Kidney Allografts

both structurally and functionally to PECAM-1 and is resolved to 2.0 Å. Multiple models of PECAM-1 structure, incorporating the two PECAM-1 polymorphisms (125L/V) were generated using the Modeler 6v2 modeling program and the best predictions were selected based on Modeler’s objective function (5). The stereochemical quality of the resulting structures was validated using the WHAT_ CHECK and PROCHECK programs (6, 7). Three dimensional comparisons of the protein structures were achieved by structural superimposition using the program YASARA (8). When the protein structure models (containing leucine or valine at sequence position 125) were superimposed (Root Mean Square Deviation of 3.13 Å over 281 C atoms), the orientation of domain-1 relative to the axis of domains-2 and -3 differed markedly between the two molecules (Fig. 1A, B). These differences are attributable to the effect of the 125L/V substitution. The difference in side chain size and orientation between valine and leucine affect the conformation of neighboring residues and “force” domain-1 into a different orientation (Fig. 1C, D). These observations based on molecular modeling of PECAM-1 suggest that the leucine/valine polymorphism at sequence position 125 confers an important structural change in the orientation of the membrane distal domain-1. Steric alteration to the PECAM-1 protein conformation is likely to affect homodimer formation and may offer a molecular explanation for the differential influence of PECAM-1 genotype on monocyte adhesion.