Combined implantation of CD34+ and CD14+ cells increases neovascularization through amplified paracrine signalling.

Cell therapy strategies that use adult peripheral blood-derived CD34⁺ progenitor cells are hampered by low cell numbers and the infrequent cellular incorporation into the neovasculature. Hence, the use of CD34⁺ cells to treat ischaemic diseases is under debate. Interaction between CD34⁺ cells and CD14⁺ cells results in superior endothelial differentiation of CD14⁺ cells in vitro, indicating that cell therapy approaches utilizing both CD34⁺ and CD14⁺ cells may be advantageous in therapeutic neovascularization. Here, human CD34⁺ and CD14⁺ cells were isolated from adult peripheral blood and implanted subcutaneously into nude mice, using matrigel as the carrier. Combined implantation of human CD34⁺ and CD14⁺ cells resulted in superior neovascularization, compared to either cell type alone, albeit incorporation of human cells into the murine vasculature was not observed. Human CD34⁺ and CD14⁺ cells produced and secreted a pentad of pro-angiogenic mediators, such as HGF, MCP-1 and IL-8, bFGF and VEGFa in monoculture. The production and secretion of pro-angiogenic mediators by CD14⁺ cells was highly amplified upon incubation with conditioned medium from CD34⁺ cells. In vivo, neovascularization of matrigel implants did not rely on the endothelial differentiation and incorporation of CD34⁺ or CD14⁺ cells, but depended on the paracrine effects of IL-8, MCP-1, HGF, bFGF and VEGFa secreted by implanted cells. Administration of this growth factor/cytokine pentad using matrigel as a carrier results in cell recruitment and microvessel formation equal to progenitor cell-induced neovascularization. These data provide new insights on neovascularization by cell therapy and may contribute to new strategies for the treatment of ischaemic diseases.

Circulating human CD34+ progenitor cells modulate neovascularization and inflammation in a nude mouse model.

CD34+ progenitor cells hold promise for therapeutic neovascularization in various settings. In this study, the role of human peripheral blood CD34+ cells in neovascularization and inflammatory cell recruitment was longitudinally studied in vivo. Human CD34+ cells were incorporated in Matrigel, implanted subcutaneously in nude mice, and explanted after 2, 4, 7, or 14 days. Cell-free Matrigels served as controls. Histochemical analyses demonstrated that neovascularization occurred almost exclusively in CD34+ implants. Cellular and capillary density were increased in cell-loaded Matrigels after 2 days and further increased at 14 days. Human CD34+ cells did not incorporate in neovessels, but formed vWF+/CD31+/VEGF+ cell clusters that were present up to day 14. However, CD34+ cells induced host neovascularization, as demonstrated by increased presence of murine CD31+ and vWF+ vasculature from day 7 to 14. Moreover, recruitment of murine monocytes/macrophages was significantly enhanced in CD34+ implants at all time points. Gene expression of chemotactic cytokines MCP-1 and IL-8 was detected on CD34+ cells in vitro and confirmed immunohistochemically in cell-loaded explants at all time points. Our data indicate that human CD34+ cells, implanted in a hypoxic environment, generate an angiogenic niche by secreting chemotactic and angiogenic factors, enabling rapid neovascularization, possibly via recruitment of monocytes/macrophages.

Female mice are more susceptible to the development of allergic airway inflammation than male mice.

BACKGROUND: In humans the prevalence of asthma is higher among females than among males after puberty. The reason for this phenomenon is not clear. OBJECTIVE: We tested the hypothesis that female mice are more susceptible to the development of allergic asthma than male mice and studied allergic immune responses in the lung. METHODS: We compared allergic airway inflammation, i.e. methacholine (MCh) responsiveness, serum IgE, and cytokines, and the number of the different leucocytes in lungs of male and female BALB/c mice, twice-sensitized to ovalbumin (OVA) and subsequently challenged with OVA (OVA-mice) or phosphate-buffered saline (PBS-mice) aerosols on days 24-26, 30, and 31. RESULTS: OVA challenge significantly increased MCh responsiveness, numbers of eosinophils, CD4(+) T cells, CD4(+)/CD25(+) T cells, B cells, and levels of Thelper (Th)2 cytokines, total, and OVA-specific IgE. There was, however, also an effect of gender, with female mice responding to OVA challenges with higher numbers of eosinophils, CD4(+) T cells, B cells, and levels of IL-4, IL-13, IFN-gamma, total, and OVA-specific IgE than male mice. In contrast, female PBS-mice had significantly lower percentages of regulatory CD4(+)/CD25(+) T cells than males (females 4.2+/-0.2% vs. males 5.3+/-0.1% of CD4(+) T cells, P<0.05). CONCLUSION: Female mice develop a more pronounced type of allergic airway inflammation than male mice after OVA challenge. The reduced percentage of regulatory T cells in the lungs of female PBS-mice may indicate that the level of these cells in the lung during the sensitization phase is important for the development and/or progression of an allergic immune response after multiple OVA challenges.

Dissemination of rat cytomegalovirus through infected granulocytes and monocytes in vitro and in vivo.

The role of leukocytes in the in vivo dissemination of cytomegalovirus was studied in this experiment. Rat cytomegalovirus (RCMV) could be transferred to rat granulocytes and monocytes by cocultivation with RCMV-infected fibroblasts in vitro. Intravenous injection of purified infected granulocytes or monocytes resulted in a systemic infection in rats, indicating that our model is a powerful tool to gain further insight into CMV dissemination and the development of new antivirals.