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Purpose:To compare whole blood viscosity and erythrocyte aggregation in humans, pigs, and sheep, before and after adding water-soluble iodinated contrast medium (CM). Methods:Two CMs were studied: iopromide (nonionic) and ioxaglate (ionic). The blood-CM viscosity was measured with a Couette viscometer. Erythrocyte aggregation was measured with an erythroaggregometer. Results:The blood-CM viscosity was increased up to +20% (relative to pure blood) with a CM concentration of 0%–10%. At CM concentrations from 10% to 50%, the viscosity decreased. The disaggregation shear stress was increased (relative to pure blood) at low CM concentration (0%–10%). When the CM concentration increased from 10% to 20%, the disaggregation shear stress was decreased, except with the pig blood–ioxaglate mixture. Conclusion:At low CM concentration the blood viscosity was increased in pig, sheep, and humans and the disaggregation shear stress was increased in pig and humans. The aggregation of sheep blood was too low to be detected by the erythroaggregometer. This rise can be explained by the formation of poorly deformable echinocytes. At higher CM concentration, the viscosity and the disaggregation shear stress decreased in relation to the blood dilution. We conclude that pig blood and sheep blood can both be used to study the effect of CM injection on blood viscosity. Nevertheless, the rheologic behavior of pig blood in terms of erythrocyte aggregation is closer to that of human blood than is sheep blood when mixed with CM. Pigs could thus be more suitable than sheep for in vivo studies of CM miscibility with blood during selective cannulation procedures.

In the bone marrow, CXCL12 and IL-7 are essential for B cell differentiation, whereas hematopoietic stem cell (HSC) maintenance requires SCF and CXCL12. Peri-sinusoidal stromal (PSS) cells are the main source of IL-7, but their characterization as a pro-B cell niche remains limited. Here, we characterize pro-B cell supporting stromal cells and decipher the interaction network allowing pro-B cell retention. Preferential contacts are found between pro-B cells and PSS cells, which homogeneously express HSC and B cell niche genes. Furthermore, pro-B cells are frequently located in the vicinity of HSCs in the same niche. Using an interactome bioinformatics pipeline, we identify Nidogen-1 as essential for pro-B cell retention in the peri-sinusoidal niche as confirmed in Nidogen-1−/−mice. Finally, human pro-B cells and hematopoietic progenitors are observed close to similar IL-7+stromal cells. Thus, a multispecific niche exists in mouse and human supporting both early progenitors and committed hematopoietic lineages.