Mesenchymal Stem Cells Enhance Chemotaxis of Activated T Cells through the CCL2-CCR2 Axis In Vitro

Activation and migration of donor T cells to the host target organs are critical mechanisms in the pathogenesis of graft-versus-host disease (GVHD). The role of monocyte chemoattractant protein-1 (MCP-1/CCL2) and its receptor CCR2 in the recruitment of T cells during immune or inflammatory response is also well known. For elucidation of the mechanism of the therapeutic effect of human bone marrow derived-mesenchymal stem cells (MSC) in GVHD, we studied the effect of these cells on migration of activated donor T cells through the CCL2-CCR2 axis in vitro. MSC were expanded from donors' bone marrow mononuclear cells. After co-culturing of IL-2-activated T cells with allogeneic MSC at different ratios, the levels of CCL2 in supernatants were measured by ELISA, and CCR2 expression in CD4⁺/CD8⁺ T cells subsets were detected by flow cytometry. The effect of MSC on the migration of activated T cells in the Transwell system was studied in the absence or presence of CCL2. Our results show that CCL2 levels in supernatants of co-cultures were significantly higher than in MSC monoculture and this increase depended on the number of MSC. MSC inhibited proliferation of T cells, but did not change the percentages of CD4⁺ and CD8⁺ T cells subsets. MSC can up-regulate the CCR2 expression in CD8⁺ subsets rather than in CD4⁺ subsets; MSC enhanced migration of IL-2-activated T cells to CCL2 by increasing the expression of CCR2. The data demonstrate that MSC can enhance chemotaxis of cytokine-activated T cells through the CCL2-CCR2 axis in vitro.

Effects of VEGF suppression by small hairpin RNA interference combined with radiotherapy on the growth of cervical cancer

This study aimed to investigate the inhibition of vascular endothelial growth factor (VEGF) by small hairpin RNA (shRNA) interference combined with radiotherapy on the growth of cervical cancer SiHa cell xenografts in nude mice. The effective pVEGF-shRNA plasmid was screened by reverse transcription-polymerase chain reaction (RT-PCR), and the cell apoptosis rate was estimated by flow cytometry. A nude mouse cervical xenograft model was established and all models were divided into four groups: blank control, VEGF shRNA, radiotherapy, and combined treatment. We calculated the tumor growth curve and the inhibitory rate. The histopathological changes of the microvascular density and VEGF protein expression were observed by immunohistochemistry. The expressions of VEGF and hypoxia inducible factor-1α (HIF-1α) proteins in the tumor tissue were analyzed via Western blot. VEGF shRNA interference inhibited the expression of radiation-induced VEGF (P < 0.05), induced apoptosis (P < 0.05), downregulated the HIF-1α protein, and reduced angiogenesis. Compared with the other three groups, the combined treatment group showed the most significant effects (P < 0.01). VEGF shRNA interference combined with radiotherapy promotes the radiosensitivity of tumors via improvement of the hypoxic microenvironment.