Imaging of Human Insulin Secreting Cells with Gd-DOTA-P88, a Paramagnetic Contrast Agent Targeting the Beta Cell Biomarker FXYD2γa.

Stéphane Demine,Isabelle Millard,Raphaël Scharfmann,Dominique Egrise,Serge Goldman,Maïté Fereau,Martin Gotthardt,Carmen Burtea,Alexander Balhuizen,Lieke Joosten,Vinciane Debaille,Decio Eizirik,Satya Chilla,Piero Marchetti,Sophie Laurent

doi:10.3390/molecules23092100

Abstract

Non-invasive imaging and quantification of human beta cell mass remains a major challenge. We performed pre-clinical in vivo validation of a peptide previously discovered by our group, namely, P88 that targets a beta cell specific biomarker, FXYD2γa. We conjugated P88 with DOTA and then complexed it with GdCl3 to obtain the MRI (magnetic resonance imaging) contrast agent (CA) Gd-DOTA-P88. A scrambled peptide was used as a negative control CA, namely Gd-DOTA-Scramble. The CAs were injected in immunodeficient mice implanted with EndoC-βH1 cells, a human beta cell line that expresses FXYD2γa similarly to primary human beta cells. The xenograft-bearing mice were analyzed by MRI. At the end, the mice were euthanized and the CA biodistribution was evaluated on the excised tissues by measuring the Gd concentration with inductively coupled plasma mass spectrometry (ICP-MS). The MRI and biodistribution studies indicated that Gd-DOTA-P88 accumulates in EndoC-βH1 xenografts above the level observed in the background tissue, and that its uptake is significantly higher than that observed for Gd-DOTA-Scramble. In addition, the Gd-DOTA-P88 showed good xenograft-to-muscle and xenograft-to-liver uptake ratios, two potential sites of human islets transplantation. The CA shows good potential for future use to non-invasively image implanted human beta cells.

Highlights

Type 1 diabetes (T1D) is an autoimmune disease leading to the progressive loss of insulin-producing pancreatic beta cells [1,2]
After the contrast agent (CA) synthesis (Figure 1), the in vivo imaging properties of Gd-DOTA-P88 were first evaluated in a mouse model bearing both wild type Chinese hamster ovary (CHO) cells and CHO-FXYD2γa+ -cells
Gd-DOTA-P88 accumulation in the transplanted pseudo-islets (TPI) was clearly visualized by MRI (Figure 4A,B), where it produced a positive contrast originating from the EndoC-βH1 xenografts

Summary

Introduction

Type 1 diabetes (T1D) is an autoimmune disease leading to the progressive loss of insulin-producing pancreatic beta cells [1,2]. The pathogenesis of T1D and the rate of beta cell mass (BCM) loss in the pre- and early-diabetes period remain unknown, hampering attempts to prevent or cure the disease [4]. T1D patients have to either rely on regular insulin injections or, in special cases, on human islet transplantation. To date, these grafts can only be followed for a short-time post-transplantation (by using pre-labelling with radioisotopes [5] (or superparamagnetic particles) and/or functionally evaluated by measuring C-peptide secretion [6], usually several weeks after transplantation in order to allow sufficient vascularization.

Methods

Results

Conclusion