279 PERV (Porcine Endogenous Retrovirus) integration and expression in pancreatic islets and other tissues in neonatal and adult pigs
Monday November 16, 2015 from 11:00 to 12:30
Room 109

Nizar I. Mourad, Belgium

Post-doctoral fellow

Chirurgie Expérimentale et Transplantation

Université Catholique de Louvain


PERV (Porcine Endogenous Retrovirus) integration and expression in pancreatic islets and other tissues in neonatal and adult pigs

Nizar Mourad1, Claire Crossan2, Victoria Cruikshank2, Pierre Gianello1, Linda Scobie2.

1Laboratoire de Chirurgie Expérimentale et Transplantation, Université Catholique de Louvain, Brussels, Belgium; 2Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Glasgow, United Kingdom

Background & aims: Pig islets represent an alternative to the current treatment of diabetic patients. However, the risk of PERV transmission limits their immediate, widespread usage in humans. PERVs are integrated in the porcine genome. However, copy number per cell and particularly expression levels can vary considerably between individuals and within different tissues of a single animal. It has been reported that copy number and expression levels are particularly low in the pancreas compared to other porcine tissues. However, data regarding this crucial aspect remain limited. More importantly, little is known about PERV status of islets themselves which represent the final product to be transplanted. In addition comparative analysis of the PERV status of neonatal piglets with adults is important since they are increasingly considered as potential islet donors for xenotransplantation.
Material & methods: Tissue samples from 56 neonatal piglets (age between 4 and 21 days) and 24 adult pigs were collected from Belgian landrace pigs used for pancreas procurement and islet isolation. Tissue biopsies were used to extract DNA for PERV copy number quantification by qPCR and RNA for PERV expression by qRT-PCR. Results are presented as means ± SEM. Statistical significance was assessed by one-way ANOVA Student-Newman-Keuls test.
Results: As shown in figure 1, PERV genome copy number presents slight non-significant variations between tested tissues. PERV expression however, shows greater variations and is significantly lower in pancreas compared to other tissues. Most importantly, PERV expression was found to be specifically enriched in pancreatic islets reaching values similar to those found in other tissues. Finally, comparison of neonatal to adult values shows that PERV genome copy number does not vary significantly from birth to adulthood and that PERV expression tends to be lower in adult tissues except for islets and PBMC where it is lower in neonatal piglets. However, these differences failed to reach statistical significance.
Conclusion: Our study confirms previous data regarding PERV expression in pancreas in a large population of animals. Most importantly, we report that PERV expression is enriched in pancreatic endocrine cells. This is of great importance since pancreatic islets are used for transplantation. PERV status of donor pancreas cannot then be used as the sole criterion and PERV expression should thus be assessed specifically in porcine islets. We hypothesize that different embryonic origins of endocrine and exocrine pancreatic tissues could explain PERV enrichment in islets which represent only 1-2% of pancreatic cells. Further analysis to determine PERV status of different islet cell populations and assessment of islet PERV infection-competence are currently underway.

European Commission FP7 funded project XENOISLET.

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