Blood Transcriptions in Clinical Islet Cell Transplantation with T Cell Depletion and Antiinflammatory Protocol

Abstract

Introduction: Allogeneic islet cell transplantation (ICT) is a promising treatment for patients with brittle type 1 diabetes. Recent reports have demonstrated that T cell depletiing immunosuppression protocol could improve islet engraftment as well as prolong graft function. We have implemented the T cell depletion plus antiinflammatory (TCD-AI) protocol using antithymocyte globulin (ATG) and double blockage of IL-1β and TNF-α. Global investigation of peripheral blood transcriptions is helpful for understanding systemic responses as well as discovering diagnostic biomarkers. Modular level analysis for cDNA microarray allows effective interpretation on the background determination with multiple immunologic disease populations (1). In this study, peripheral blood transcriptions were measured to explore systemic biological response for early phase of ICT with TCD-AI protocol. Methods: Five islet recipients received TCD-AI protocol with ATG for induction, along with anakinra and etanercept. Peripheral blood samples were collected on the screening day (baseline), post-transplant days 4, 7, 14, 28 and 42. Isolated RNA were hybridized on to Illumina HumanHT-12 v4 BeadChip. Probe-level differential gene expression analysis was conducted using mixed model adjusting for correlation for longitudinal data to compare between baseline and post-transplant samples. A false discovery rate of 0.1 was used to account for multiple testing. Modular analysis of gene expressions were employed with previously determined sets of genes (1). Results: Four patients (80%) achieved insulin independence after single islet infusion and the median duration of insulin independence is 17.5 months (range: 4-36 months) as of the analysis. The number of genes that were expressed with significant difference (p< 0.05) are 866, 465, 492, 160, 353 and 80 on day 4, 7, 14, 21, 28 and 42 after transplant when compare to baseline. Modular analysis of cDNA microarray on day 4 revealed upregulated modules annotated as interferon responses (M3.4), inflammation (M4.2), myeloid lineage (M4.6) and cell cycle (M6.13), and downregulated modules as coagulation cascade (M3.6), T-cells (M4.1 and M6.15), lymphoid lineage (M4.7 and M6.9) and cytotoxicity (M4.15) (Figure 1). Among these modules, T-cells (M4.1 and M6.19) and cytotoxicity (M4.15) modules were downregulated throughout the study period.[Figure 1]Figure 1. Blood transcriptional fingerprints with islet recipients receiving TCD-AI protocol. Relative changes in whole blood gene expressions with islet recipients for day 4 to 42, compared to baseline. Colored spots represent the percentage of significantly upregulated (red) or downregulated (blue) transcripts (p< 0.002). Conclusion: Gene expression modules annotated as T-cells and cytotoxicity were downregulated in early phase of ICT, suggesting that effective control of cellular immune response as the background mechanism of improved outcome of TCD-AI protocol. (1) Chaussabel D, et al. Immunity 2008;29:150-164.