Type 1 diabetes is associated with reduced vascular repair, as indicated by impaired wound healing and reduced collateral formation in ischemia. Recently, endothelial progenitor cells (EPCs) have been identified as important regulators of these processes. We therefore explored the concept that EPCs are dysfunctional in diabetes. The number of EPCs obtained from type 1 diabetic patients in culture was 44% lower compared with age-and sex-matched control subjects (P < 0.001). This reduction was inversely related to levels of HbA 1c (R ‫؍‬ ؊0.68, P ‫؍‬ 0.01). In addition, we demonstrated that patient EPCs were also impaired in function using an in vitro angiogenesis assay. Conditioned media from patient EPCs were significantly reduced in their capacity to support endothelial tube formation in comparison to control EPCs. Therefore, despite culturing the EPCs under normoglycemic conditions, functional differences between patient and control EPCs were maintained. Our findings demonstrate that adverse metabolic stress factors in type 1 diabetes are associated with reduced EPC numbers and angiogenicity. We hypothesize that EPC dysfunction contributes to the pathogenesis of vascular complications in type 1 diabetes. Diabetes 53: 195

Lgr5 marks adult stem cells in multiple adult organs and is a receptor for the Wnt-agonistic R-spondins (RSPOs). Intestinal, stomach and liver Lgr5+ stem cells grow in 3D cultures to form ever-expanding organoids, which resemble the tissues of origin. Wnt signalling is inactive and Lgr5 is not expressed under physiological conditions in the adult pancreas. However, we now report that the Wnt pathway is robustly activated upon injury by partial duct ligation (PDL), concomitant with the appearance of Lgr5 expression in regenerating pancreatic ducts. In vitro, duct fragments from mouse pancreas initiate Lgr5 expression in RSPO1-based cultures, and develop into budding cyst-like structures (organoids) that expand five-fold weekly for >40 weeks. Single isolated duct cells can also be cultured into pancreatic organoids, containing Lgr5 stem/progenitor cells that can be clonally expanded. Clonal pancreas organoids can be induced to differentiate into duct as well as endocrine cells upon transplantation, thus proving their bi-potentiality.

Activation of mitogen-activated protein kinase (MAPK) pathways leads to cellular differentiation and/or proliferation in a wide variety of cell types, including developing thymocytes. The basic helix-loop-helix (bHLH) proteins E12 and E47 and an inhibitor HLH protein, Id3, play key roles in thymocyte differentiation. We show here that E2A DNA binding is lowered in primary immature thymocytes consequent to T cell receptor (TCR)-mediated ligation. Whereas expression of E2A mRNA and protein are unaltered, Id3 transcripts are rapidly induced upon signaling from the TCR. Activation of Id3 transcription is regulated in a dose-dependent manner by the extracellular signal-regulated kinase (ERK) MAPK module. These observations directly connect the ERK MAPK cascade and HLH proteins in a linear pathway.

The estrogen receptor (ER) is an important regulator of growth and differentiation of breast epithelium. Transactivation by ER depends on a leucine-rich motif, which constitutes a ligand-regulated binding site for steroid receptor coactivators (SRCs). Cyclin D1 is frequently amplified in breast cancer and can activate ER through direct binding. We show here that cyclin D1 also interacts in a ligand-independent fashion with coactivators of the SRC-1 family through a motif that resembles the leucine-rich coactivator binding motif of nuclear receptors. By acting as a bridging factor between ER and SRCs, cyclin D1 can recruit SRC-family coactivators to ER in the absence of ligand. A cyclin D1 mutant that binds to ER but fails to recruit coactivators preferentially interferes with ER activation in breast cancer cells that have high levels of cyclin D1. These data support that cyclin D1 contributes significantly to ER activation in breast cancers in which the protein is overexpressed. Our present results reveal a novel route of coactivator recruitment to ER and establish a direct role for cyclin D1 in regulation of transcription.