Long- and short-term outcomes in renal allografts with deceased donors: A large recipient and donor genome-wide association study.

Improvements in immunosuppression have modified short-term survival of deceased-donor allografts, but not their rate of long-term failure. Mismatches between donor and recipient HLA play an important role in the acute and chronic allogeneic immune response against the graft. Perfect matching at clinically relevant HLA loci does not obviate the need for immunosuppression, suggesting that additional genetic variation plays a critical role in both short- and long-term graft outcomes. By combining patient data and samples from supranational cohorts across the United Kingdom and European Union, we performed the first large-scale genome-wide association study analyzing both donor and recipient DNA in 2094 complete renal transplant-pairs with replication in 5866 complete pairs. We studied deceased-donor grafts allocated on the basis of preferential HLA matching, which provided some control for HLA genetic effects. No strong donor or recipient genetic effects contributing to long- or short-term allograft survival were found outside the HLA region. We discuss the implications for future research and clinical application.

Phospholipase A2 receptor (PLA2R1) sequence variants in idiopathic membranous nephropathy.

The M-type receptor for phospholipase A2 (PLA2R1) is the major target antigen in idiopathic membranous nephropathy (iMN). Our recent genome-wide association study showed that genetic variants in an HLA-DQA1 and phospholipase A2 receptor (PLA2R1) allele associate most significantly with biopsy-proven iMN, suggesting that rare genetic variants within the coding region of the PLA2R1 gene may contribute to antibody formation. Here, we sequenced PLA2R1 in a cohort of 95 white patients with biopsy-proven iMN and assessed all 30 exons of PLA2R1, including canonical (GT-AG) splice sites, by Sanger sequencing. Sixty patients had anti-PLA2R1 in serum or detectable PLA2R1 antigen in kidney tissue. We identified 18 sequence variants, comprising 2 not previously described, 7 reported as rare variants (<1%) in the Single Nucleotide Polymorphism Database or the 1000 Genomes project, and 9 known to be common polymorphisms. Although we confirmed significant associations among 6 of the identified common variants and iMN, only 9 patients had the private or rare variants, and only 4 of these patients were among the 60 who were PLA2R positive. In conclusion, rare variants in the coding sequence of PLA2R1, including splice sites, are unlikely to explain the pathogenesis of iMN.

A meta-analysis of the impact of the two-layer method of preservation on human pancreatic islet transplantation.

There are conflicting reports about the effectiveness of perfluorocarbons used in the two-layer method (TLM) of pancreas preservation for human islet transplantation. The mechanism of action is unclear and the optimal role of this method uncertain. The study design was a meta-analysis of the evidence that TLM improves islet isolation outcomes. Pubmed, CENTRAL, EMBASE, Science Citation Index, and BIOSIS were searched electronically in January 2008. After selecting the relevant human trials for meta-analysis data relating to donor variables, study design, primary and secondary islet isolation outcomes were extracted. Electronic searches identified eight unique citations, describing 11 human studies that were eligible for the meta-analysis. When comparing TLM with preservation in University of Wisconsin (UW) solution, there was a statistically significant higher islet yield [WMD 711.55, 95% confidence interval (CI) 140.03-1283.07] in the TLM group. The proportion of transplantable preparations obtained was not significantly different (OR 1.30, 95% CI 0.89-1.88) between the two groups. The rate of successful islet isolations for marginal organs was higher in the TLM group (OR 6.69, 95% CI 1.80-24.87). Improved oxygenation and preservation of cellular bioengertics is thought to be the main underlying mechanism, although no single mechanism has yet been confirmed. There is currently no clear evidence that the TLM is beneficial in human islet transplantation. It may improve the preservation of marginal organs.

Limited penetration of perfluorocarbon in porcine pancreas preserved by two-layer method with (19)fluorine magnetic resonance spectroscopy and headspace gas chromatography.

The mechanism of the two-layer method (TLM) of pancreas preservation is unclear. Facilitating oxygen diffusion into preserved pancreas has been suggested, but direct measurements of tissue pO(2) have yielded conflicting results. The degree of penetration of perfluorocarbon (PFC) into the pancreas during TLM storage is unknown. Segments of porcine pancreas (7.5 cm in length) were preserved either in University of Wisconsin solution (UW) alone (n = 6) or in TLM for 24 h (n = 6). Pancreatic samples were analyzed using Varian INOVA 9.4 T MR scanner. External PFC standard was introduced for quantification. Four consecutive transverse images of 4 mm thickness were obtained using a spin-echo sequence. (19)Fluorine magnetic resonance spectroscopy ((19)F MRS) was performed with the same parameters except with more averages. MR data were confirmed by headspace chromatography. PFC standard was readily detected in (19)F MR images. There was no signal from pancreas in (19)F MR images following either UW or TLM storage. (19)F MR spectra typical of PFC were not obtained from either UW- or TLM-preserved pancreas with nonlocalized (19)F MRS. Mean concentration of PFC in TLM pancreas measured by head space chromatography was 0.011 nl/g (SD ± 0.006), not significantly different from background concentration (0.012 nl/g, SD ± 0.006) in UW pancreas (p = 0.42). There was no evidence of penetration of PFC into pancreas tissues investigated either by MR or chromatography in organs preserved at hypothermia by TLM, and mechanisms of TLM remain speculative.

Time course of islet loss after intraportal transplantation.

A high percentage of islets fail to survive intraportal transplantation, but the absolute amount and time course of this loss are uncertain. We have devised a technique to directly quantitate the number of surviving islets using simultaneous selective transplantation of islets and inert beads into the posterior lobes of the liver. Islet:bead ratio did not change significantly within the first 2 hours, but fell progressively thereafter, giving calculated islet survival rates of 89, 43, and 66% at days 1, 7 and 28, respectively. This technique provides a baseline from which to develop strategies to improve the survival of intraportally transplanted islets.