Interstitial and vascular pancreas rejection in relation to graft survival

Current concepts in the simultaneous transplantation of kidney and pancreas

Diabetes mellitus (DM) represents an enormous health care concern for the United States and other countries. According to the American Diabetes Association in 2007, there were more than 23 million Americans living with diabetes. This is a 13.5% increase from 2005, likely representing increases in Type II DM (DMII). Diabetes mellitus results when the beta cells of the pancreas are unable to produce sufficient insulin to prevent hyperglycemia. Simultaneous pancreas and kidney transplantation, or SPK, may be indicated for patients that have experienced renal failure as a complication of DM (either type I or type II). Until recently, technical failure represented a significant impediment to the success of pancreas transplantation. At the turn of the century, however, both renal and pancreatic graft survival dramatically improved. Immunologic and nonimmunologic causes of graft failure continue to challenge inpatient and outpatient management. With vigilance in the ICU postoperatively and in the clinic, SPK can provide significant benefit both in patient survival and quality of life.

Interleukin-10 Gene Transfection of Donor Pancreas Grafts Protects against Rejection after Heterotopic Pancreas Transplantation in a Rat Model

OBJECTIVE

The aim of this study was to assess the effect of immunoregulatory cytokine interleukin-10 (IL-10) gene therapy on pancreas tissue rejection in a heterotopic pancreas transplantation model.

BACKGROUND

Modulation of inflammatory responses by anti-inflammatory cytokines (e.g., IL-10) has been suggested to minimize organ rejection. In this context, modulation of cytokines using gene therapy could be a new therapeutic modality in preventing organ rejection.

METHODS

The study was performed using male inbred Wistar rats as recipients and Sprague-Dawley rats as donors. 24 h before transplantation, groups of rats, named IL-10 (n = 20) and green fluorescent protein (GFP, n = 20), were injected with viral vectors Ad5CMVhIL10 or Ad5CMVGFP. Sham-operated rats (n = 20) underwent saline injection only before transplantation. The pancreatic tissue from each of these donor rats was subsequently transplanted into the corresponding groups of streptozotocin-induced diabetic recipient rats. Recipients were thus transfected with either IL-10 (n = 20), GFP-only carrying viral vectors (n = 20) or no viral vectors (normal saline, n = 20). A selected number of animals from each recipient group (n = 5) was sacrificed at weekly intervals for 3 weeks and some were further followed up to 12 weeks before sacrifice. Histological assessment of the pancreatic tissue was made based on rejection and GFP expression. Blood glucose levels were checked daily in all groups until sacrifice. Upon sacrifice, serum cytokine and insulin levels were measured. Histopathological correlations between blood glucose levels, serum insulin levels and serum IL-10 levels were made.

RESULTS

IL-10 gene therapy significantly attenuated pancreas rejection compared to controls, provided more normal blood glucose levels and elevated plasma insulin levels. Upon assumed natural deactivation of transferred viruses after 4 weeks, differences between groups in terms of rejection, blood glucose and insulin levels disappeared.

CONCLUSION

These findings suggest that IL-10 gene therapy significantly reduced pancreas rejection.

Banff schema for grading pancreas allograft rejection: working proposal by a multi-disciplinary international consensus panel

Accurate diagnosis and grading of rejection and other pathological processes are of paramount importance to guide therapeutic interventions in patients with pancreas allograft dysfunction. A multi-disciplinary panel of pathologists, surgeons and nephrologists was convened for the purpose of developing a consensus document delineating the histopathological features for diagnosis and grading of rejection in pancreas transplant biopsies. Based on the available published data and the collective experience, criteria for the diagnosis of acute cell-mediated allograft rejection (ACMR) were established. Three severity grades (I/mild, II/moderate and III/severe) were defined based on lesions known to be more or less responsive to treatment and associated with better- or worse-graft outcomes, respectively. The features of chronic rejection/graft sclerosis were reassessed, and three histological stages were established. Tentative criteria for the diagnosis of antibody-mediated rejection were also characterized, in anticipation of future studies that ought to provide more information on this process. Criteria for needle core biopsy adequacy and guidelines for pathology reporting were also defined. The availability of a simple, reproducible, clinically relevant and internationally accepted schema for grading rejection should improve the level of diagnostic accuracy and facilitate communication between all parties involved in the care of pancreas transplant recipients.

Histological grading of chronic pancreas allograft rejection/graft sclerosis

Chronic rejection (CR) of pancreas allografts needs to be accurately defined and diagnosed. We propose a grading scheme designed for percutaneous needle biopsies (C0-CIII). Grading is based on the semi-quantitative determination of fibrosis and corresponding proportional loss of exocrine parenchyma. Pancreas biopsies (n = 141) from 46 patients were studied. Twenty-six patients lost graft function after a mean time of 25.5 months, whereas 20 patients retained good graft function during a mean follow-up of 67.7 months. Sequential biopsies showed gradual progression of CR over time (p = 0.0001), and good correlation was found between the CR grade and the time elapsed from transplantation (p = 0.0001). The CR grade was predictive of the remaining time of graft function (54.3 months for C0, 24.6 months for CI, 9.7 months for CII and 1.6 months for CIII p = 0.00001). Preceding episodes of acute rejection (AR) were more frequent and more severe, and often occurred late in patients with graft loss due to CR (p = 0.04). Reproducibility among pathologists from different institutions was excellent for grades C0 (Kappa 0.9) and CIII (0.87), substantial for Grade CII (0.61) and moderate for Grade CI (0.59). The proposed grading scheme provides a reliable and reproducible tool for the assessment of CR in percutaneous needle biopsies, with definite prognostic significance.