Abstract 11527: Depletion of Pro-angiogenic Progenitor Cells in Bone Marrow of Diabetic Patients Involves the Deregulation of Micro-RNA-155/FOXO3a/p27kip1 Signaling Pathway
Background:Diabetes mellitus reduces the availability and function of circulating progenitor cells (PCs). This study investigates the effect of diabetes on BM composition, focusing on the microRNA-155 (miR-155)/FOXO3a/p27kip1 signaling pathway as a mechanism underlying the shortage of CD34pos-PCs.
Methods:BM was obtained from age-matched non-diabetic (C) and type 2 diabetic (T2D) patients undergoing hip replacement, and from T2D patients undergoing amputation for critical limb ischemia (CLI) (7 to 10 patients/group). BM remodeling was assessed by histomorphometry, immunostaining, and flow cytometry analyses. Apoptotic BM mononuclear cells (MNCs) were identified in situ by TUNEL assay. Expressional studies were performed on MAC-sorted CD34pos-PCs.
Results: Diabetes causes a reduction of hematopoietic tissue, fat deposition, and microvascular rarefaction, especially when associated to CLI. Immunofluorescence microscopy documented a decrease of CD34posCD45pos-PCs in BM of both diabetic groups (T2D:-41%, and T2D+CLI:-72% vs. C, p<0.001). Likewise, flow cytometry showed a reduction of proangiogenic CD34posCD14posCD45dimKDRposCXCR4pos-PCs in T2D (0.014±0.01) and T2D+CLI (0.023±0.008) compared to C (0.05±0.01% of MNCs, p<0.05 for both comparisons). Apoptosis was activated in diabetic BM, especially in CLI patients. In line, CD34pos-PCs from diabetic subjects showed upregulation of the pro-apoptotic factor FOXO3a (T2D:72-fold, T2D+CLI:116-fold vs. C) and nuclear localization of FOXO3a, leading to transcriptional activation of downstream cyclin inhibitors p21 (T2D:237-fold, T2D+CLI:78-fold vs. C) and p27kip1 (T2D:29-fold, T2D+CLI:18-fold vs. C). FOXO3a is a validated target of miR-155. We found miR-155 to be downregulated in diabetic CD34pos-PCs (T2D:-3.5-fold, and T2D+CLI:-4-fold) and inversely correlated with FOXO3a levels (Spearman r=-0.5766, p=0.006).
Conclusions: Diabetes directly impinges upon human BM integrity causing microangiopathy, shortage of pro-angiogenic cells and activation of pro-apoptotic signaling pathway. These data offer a new key of interpretation for failure of diabetic BM to provide an adequate source of regenerative cells.
- © 2012 by American Heart Association, Inc.