Purpose: Early islet loss post-infusion remains a significant problem in islet transplantation, despite the use of heparinised media to abrogate the effects of Tissue Factor (TF) initiated Instant Blood-Mediated Inflammatory Reaction (IBMIR). We hypothesised that islet exposure to hypoxic conditions post-infusion results in upregulation of TF expression, thereby contributing to further injury and islet loss post transplantation. In this context, we examined the adherence of cytotopic peptides in cell preparations to allow future targeted therapy to protect islets in the early transplant period.

Methods: Human islets were isolated from normoglycaemic donors at transplantation facilities in Pisa, Milan and Edmonton, with the relevant local and national ethical permissions. Isolated human islets in culture medium were exposed to hypoxic conditions in a modular hypoxia chamber (6 hours, 8% oxygen). RNA was extracted from islets both at baseline and immediately post hypoxia exposure (each condition performed in triplicate). Comparisons of TF expression, normalised to GAPDH, were made within individual donor preparations to account for known differences in TF expression from different donors. Islet preparations were incubated with a fluorescent peptide (PTL-071), consisting of a membrane-localising agent attached to Fluorescein by a non-reducible linker. Imaging of islets was performed using Brightfield microscopy.

Results: Islet exposure to hypoxia resulted in a significant upregulation of TF expression within individual donor preparations (p=0.03). The fluorescent cytotopic peptide bound successfully to intact islets and remained adherent after washing of islets and replacement with fresh media.

Discussion: Islet exposure to hypoxic conditions induces Tissue Factor upregulation, potentially contributing to the high early islet loss post-infusion. Localised, islet adherent therapy as demonstrated here may prove beneficial in improving islet viability post-transplantation by providing targeted treatment during this early injurious period. This sets the ground for future studies examining the use of Thrombalexins (cytotopic, direct thrombin inhibitor peptides), in islet transplantation.

CITATION INFORMATION: Sandhu B, Prendecki M, Rutter G, Martinez-Sanchez A, Kanda N, Galloway-Phillips N, Smith R, Pusey C, Papalois V. Hypoxia Induces Tissue Factor Upregulation in Isolated Human Islets. Am J Transplant. 2017;17 (suppl 3).

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