Brief Report: Elastin Microfibril Interface 1 and Integrin-Linked Protein Kinase Are Novel Markers of Islet Regenerative Function in Human Multipotent Mesenchymal Stromal Cells.

Multipotent mesenchymal stromal cell (MSC) transplantation is proposed as a novel therapy for treating diabetes by promoting the regeneration of damaged islets. The clinical promise of such treatments may be hampered by a high degree of donor-related variability in MSC function and a lack of standards for comparing potency. Here, we set out to identify markers of cultured human MSCs directly associated with islet regenerative function. Stromal cultures from nine separate bone marrow donors were demonstrated to have differing capacities to reduce hyperglycemia in the NOD/SCID streptozotocin-induced diabetic model. Regenerative (R) and non-regenerative (NR) MSC cultures were directly compared using isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics. A total of 1,410 proteins were quantified resulting in the identification of 612 upregulated proteins and 275 downregulated proteins by ± 1.2-fold in R-MSC cultures. Elastin microfibril interface 1 (EMILIN-1), integrin-linked protein kinase (ILK), and hepatoma-derived growth factor (HDGF) were differentially expressed in R-MSCs, and Ingenuity Pathway Analyses revealed each candidate as known regulators of integrin signaling. Western blot validation of EMILIN-1, ILK, and HDGF not only showed significantly higher abundance levels in R-MSCs, as compared with NR-MSCs, but also correlated with passage-induced loss of islet-regenerative potential. Generalized estimating equation modeling was applied to examine the association between each marker and blood glucose reduction. Both EMILIN-1 and ILK were significantly associated with blood glucose lowering function in vivo. Our study is the first to identify EMILIN-1 and ILK as prospective markers of islet regenerative function in human MSCs. Stem Cells 2016;34:2249-2255.