Hepatic ischemia-reperfusion increases circulating bone marrow-derived progenitor cells and tumor growth in a mouse model of colorectal liver metastases.

BACKGROUND: Hepatic pedicle clamping is often required to reduce blood loss and transfusion during liver resection. However, the question remains whether use of hepatic pedicle clamping promotes tumor growth. Endothelial progenitor cells (EPCs) are mobilized from bone marrow in response to tissue ischemia, which allows neovascularization of ischemic tissue. It has been suggested that EPCs are involved in tumor progression. We hypothesized that hepatic ischemia reperfusion (I/R)-induced mobilization of EPCs could enhance growth of microscopic tumor, therefore promoting liver metastasis in a mouse model of colorectal cancer. MATERIALS AND METHODS: We used mouse models of hepatic I/R and hind limb ischemia. For comparison, we studied mice that underwent limb ischemia as positive controls of EPC mobilization. At day 0, we divided 40 mice into four groups: hepatic I/R, hind limb ischemia, combined hepatic I/R and hind limb ischemia, and control (sham midline incision laparotomy). At day 2, we induced liver metastasis in all mice by injecting CT-26 cells into the spleen. Time-dependent circulating EPCs were determined by flow cytometry. We evaluated liver metastasis and microvascular density on day 21. RESULTS: The number of circulating progenitor cells increased rapidly in the ischemic groups compared with the control group. Hepatic I/R significantly increased tumor outgrowth compared with the control group. Increased tumor growth was associated with enhanced CD31-positive microvascular density in liver tissue. CONCLUSIONS: Hepatic I/R leads to mobilization of bone marrow-derived EPCs and enhanced intra-hepatic angiogenesis, which is associated with increased tumor burden in an animal model of colorectal liver metastasis.

Diabetic Ephrin-B2-Stimulated Peripheral Blood Mononuclear Cells Enhance Poststroke Recovery in Mice.

Clinical trials of cell therapy in stroke favor autologous cell transplantation. To date, feasibility studies have used bone marrow-derived mononuclear cells, but harvesting bone marrow cells is invasive thus complicating bedside treatment. We investigated the therapeutic potential of peripheral blood-derived mononuclear cells (PB-MNC) harvested from diabetic patients and stimulated by ephrin-B2 (PB-MNC+) (500,000 cells), injected intravenously 18-24 hours after induced cerebral ischemia in mice. Infarct volume, neurological deficit, neurogenesis, angiogenesis, and inflammation were investigated as were the potential mechanisms of PB-MNC+ cells in poststroke neurorepair. At D3, infarct volume was reduced by 60% and 49% compared to unstimulated PB-MNC and PBS-treated mice, respectively. Compared to PBS, injection of PB-MNC+ increased cell proliferation in the peri-infarct area and the subventricular zone, decreased microglia/macrophage cell density, and upregulated TGF-ß expression. At D14, microvessel density was decreased and functional recovery was enhanced compared to PBS-treated mice, whereas plasma levels of BDNF, a major regulator of neuroplasticity, were increased in mice treated with PB-MNC+ compared to the other two groups. Cell transcriptional analysis showed that ephrin-B2 induced phenotype switching of PB-MNC by upregulating genes controlling cell proliferation, inflammation, and angiogenesis, as confirmed by adhesion and Matrigel assays. Conclusions. This feasibility study suggests that PB-MNC+ transplantation poststroke could be a promising approach but warrants further investigation. If confirmed, this rapid, noninvasive bedside cell therapy strategy could be applied to stroke patients at the acute phase.

Smooth muscle cell phenotypic switching in stroke.

Disruption of cerebral blood flow after stroke induces cerebral tissue injury through multiple mechanisms that are not yet fully understood. Smooth muscle cells (SMCs) in blood vessel walls play a key role in cerebral blood flow control. Cerebral ischemia triggers these cells to switch to a phenotype that will be either detrimental or beneficial to brain repair. Moreover, SMC can be primarily affected genetically or by toxic metabolic molecules. After stroke, this pathological phenotype has an impact on the incidence, pattern, severity, and outcome of the cerebral ischemic disease. Although little research has been conducted on the pathological role and molecular mechanisms of SMC in cerebrovascular ischemic diseases, some therapeutic targets have already been identified and could be considered for further pharmacological development. We examine these different aspects in this review.