Radiation rescue: mesenchymal stromal cells protect from lethal irradiation.

BACKGROUND: Successful treatment of acute radiation syndromes relies on immediate supportive care. In patients with limited hematopoietic recovery potential, hematopoietic stem cell (HSC) transplantation is the only curative treatment option. Because of time consuming donor search and uncertain outcome we propose MSC treatment as an alternative treatment for severely radiation-affected individuals. METHODS AND FINDINGS: Mouse mesenchymal stromal cells (mMSCs) were expanded from bone marrow, retrovirally labeled with eGFP (bulk cultures) and cloned. Bulk and five selected clonal mMSCs populations were characterized in vitro for their multilineage differentiation potential and phenotype showing no contamination with hematopoietic cells. Lethally irradiated recipients were i.v. transplanted with bulk or clonal mMSCs. We found a long-term survival of recipients with fast hematopoietic recovery after the transplantation of MSCs exclusively without support by HSCs. Quantitative PCR based chimerism analysis detected eGFP-positive donor cells in peripheral blood immediately after injection and in lungs within 24 hours. However, no donor cells in any investigated tissue remained long-term. Despite the rapidly disappearing donor cells, microarray and quantitative RT-PCR gene expression analysis in the bone marrow of MSC-transplanted animals displayed enhanced regenerative features characterized by (i) decreased proinflammatory, ECM formation and adhesion properties and (ii) boosted anti-inflammation, detoxification, cell cycle and anti-oxidative stress control as compared to HSC-transplanted animals. CONCLUSIONS: Our data revealed that systemically administered MSCs provoke a protective mechanism counteracting the inflammatory events and also supporting detoxification and stress management after radiation exposure. Further our results suggest that MSCs, their release of trophic factors and their HSC-niche modulating activity rescue endogenous hematopoiesis thereby serving as fast and effective first-line treatment to combat radiation-induced hematopoietic failure.

Combined antiangiogenic therapy is superior to single inhibitors in a model of renal cell carcinoma.

PURPOSE: Similar to cytotoxic drugs, a combination of antiangiogenic factors may lead to an improved treatment response and minimize resistance by targeting different pathways. Therefore, we investigated the effects of a combination of endogenous inhibitors using endostatin, soluble neuropilin-1 and thrombospondin-2 in a renal cell carcinoma model. MATERIALS AND METHODS: Microencapsulated porcine aortic endothelial cells producing endostatin, soluble neuropilin-1 or thrombospondin-2 were tested in vitro and in a murine renal cell carcinoma alone or as a combination of the all 3 factors. Renca cells were applied subcutaneously for local therapy or injected intravenously in a metastatic model. RESULTS: Factors released from microbeads inhibited endothelial cell function but did not affect tumor cell proliferation in vitro. In vivo tumor growth was inhibited similarly by each angiogenic inhibitor alone (0.17, 0.18 and 0.18 gm in endostatin, soluble neuropilin-1 and thrombospondin-2 treated mice vs 1.3 gm in controls). The combination of all 3 inhibitors further decreased tumor weight (0.03 gm). In the metastatic model treatment with angiogenic inhibitors induced a significant reduction in the size and number of lung metastases with additive effects when factors were used in combination. CONCLUSIONS: The combination of angiogenic inhibitors was superior to single factors, suggesting additive activity. These data support the strategy of combining angiogenic inhibitors to accomplish a complete angiogenic blockade.