Switching-on survival and repair response programs in islet transplants by bone marrow-derived vasculogenic cells.

OBJECTIVE: Vascular progenitors of bone marrow origin participate to neovascularization at sites of wound healing and transplantation. We hypothesized that the biological purpose of this bone marrow-derived vascular component is to contribute angiogenic and survival functions distinct from those provided by the local tissue-derived vasculature. RESEARCH DESIGN AND METHODS AND RESULTS: To address this hypothesis, we investigated the functional impact of bone marrow-derived vascular cells on pancreatic islets engraftment using bone marrow-reconstituted Id1(+/-)Id3(-/-) mice, a model of bone marrow-derived vasculogenesis. We show that, in this model, bone marrow-derived vasculogenic cells primarily contribute to the formation of new blood vessels within islet transplants. In contrast, graft revascularization in a wild-type background occurs by tissue-derived blood vessels only. Using these distinct transplant models in which bone marrow-and tissue-derived vasculature are virtually mutually exclusive, we demonstrate that bone marrow-derived vasculogenic cells exhibit enhanced angiogenic functions and support prompt activation of islets survival pathways, which significantly impact on islets engraftment and function. Moreover, gene profiling of vascular and inflammatory cells of the grafts demonstrate that neovascularization by bone marrow-derived cells is accompanied by the activation of a genetic program uniquely tuned to downregulate harmful inflammatory responses and to promote tissue repair. CONCLUSIONS: These studies uncover the biological significance of bone marrow-derived vasculogenic cells in the response to injury during transplantation. Enhancing the contribution of bone marrow-derived vasculogenic cells to transplantation sites may help to overcome both limited angiogenic responses of the adult tissue-derived vasculature and untoward effects of inflammation on transplant engraftment.

Creating prodynorphin-expressing stem cells alerted for a high-throughput of cardiogenic commitment.

BACKGROUND: The development of cell therapy for the rescue of damaged heart muscle is a major area of inquiry. Within this context, the establishment of a cardiogenic cell line may remarkably facilitate the molecular dissection of cardiac fate specification, a low-efficiency and still poorly understood process, paving the way for novel approaches in the use of stem cells for cardiac repair. METHODS & RESULTS: We used GTR1 cells, a derivative of mouse R1 embryonic stem cells bearing the puromycin-resistance gene driven by the cardiomyocyte-specific alpha-myosin heavy chain promoter, affording a gene trapping selection of a virtually pure population of embryonic stem cell-derived cardiomyocytes. Third-generation lentiviral vectors were used to overexpress the prodynorphin gene, previously shown to orchestrate a dynorphinergic system acting as a major conductor of embryonic stem cell cardiogenesis. Lentiviral prodynorphin transduction remarkably enhanced the transcription of GATA-4 and Nkx-2.5, two cardiac lineage-promoting genes, resulting in a dramatic increase in the number of spontaneously beating cardiomyocytes. Transduced cells also exhibited a subcellular redistribution patterning of protein kinase C-beta, -delta and -epsilon, a major requirement in cardiac lineage commitment. This activation resulted from a sustained increase in the transcription of targeted protein kinase C genes. Prodynorphin transduction was selective in nature and failed to activate genes responsible for skeletal myogenesis or neuronal specification. CONCLUSIONS: The cell line developed in this study provides a powerful in vitro model of cardiomyogenesis that may help clarify the cascade of transcriptional activation and signaling networks that push multipotent cells to take on the identity of a cardiac myocyte.