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Systemic and cerebral inflammation following antenatal infection (e.g. chorioamnionitis) and dysregulation of the blood brain barrier (BBB) are major risk factors for abnormal neonatal brain development. Administration of multipotent adult progenitor cells (MAPCs) represents an interesting pharmacological strategy as modulator of the peripheral and cerebral immune response and protector of BBB integrity. We studied the immunomodulatory and protective cerebrovascular potential of prenatally administered MAPCs in a preclinical ovine model for antenatal inflammation.Ovine fetuses were intra-amniotically (i.a.) exposed to lipopolysaccharide (LPS) or saline at gestational day 125, followed by the intravenous administration of 1*107 MAPCs or saline at gestational day 127. Circulating inflammation markers were measured. Fetal brains were examined immuno-histochemically post-mortem at gestational day 132.Fetal plasma IL-6 levels were elevated significantly 24 h after LPS administration. In utero systemic MAPC treatment after LPS exposure increased Annexin A1 (ANXA1) expression in the cerebrovascular endothelium, indicating enforcement of BBB integrity, and increased the number of leukocytes at brain barriers throughout the brain. Further characterisation of brain barrier-associated leukocytes showed that monocyte/choroid plexus macrophage (IBA-1+/CD206+) and neutrophil (MPO+) populations predominantly contributed to the LPS-MAPC-induced increase of CD45+cells. In the choroid plexus, the percentage of leukocytes expressing the proresolving mediator ANXA1 tended to be decreased after LPS-induced antenatal inflammation, an effect reversed by systemic MAPC treatment. Accordingly, expression levels of ANXA1 per leukocyte were decreased after LPS and restored after subsequent MAPC treatment.Increased expression of ANXA1 by the cerebrovasculature and immune cells at brain barriers following MAPC treatment in an infectious setting indicate a MAPC driven early defence mechanism to protect the neonatal brain against infection-driven inflammation and potential additional pro-inflammatory insults in the neonatal period.

Angiogenic, that is, newly formed, blood vessels play an important role in tumor growth and metastasis and are a potential target for tumor treatment. In previous studies, the αvβ3 integrin, which is strongly expressed in angiogenic vessels, has been used as a target for Arg-Gly-Asp (RGD)-functionalized nanoparticulate contrast agents for magnetic resonance imaging-based visualization of angiogenesis. In the present study, the target-to-background ratio was increased by diminishing the nonspecific contrast enhancement originating from contrast material present in the blood pool. This was accomplished by the use of a so-called avidin chase, which allowed rapid clearance of non-bound paramagnetic RGD-biotin-liposomes from the blood circulation. C57BL/6 mice, bearing a B16F10 mouse melanoma, received RGD-functionalized or untargeted biotin-liposomes, which was followed by avidin infusion or no infusion. Precontrast, postcontrast, and postavidin T1-weighted magnetic resonance images were acquired at 6.3 T. Postcontrast images showed similar percentages of contrast-enhanced pixels in the tumors of mice that received RGD-biotin-liposomes and biotin-liposomes. Post avidin infusion this percentage rapidly decreased to precontrast levels for biotin-liposomes, whereas a significant amount of contrast-enhanced pixels remained present for RGD-biotin-liposomes. These results showed that besides target-associated contrast agent, the circulating contrast agent contributed significantly to the contrast enhancement as well. Ex vivo fluorescence microscopy confirmed association of the RGD-biotin-liposomes to tumor endothelial cells both with and without avidin infusion, whereas biotin-liposomes were predominantly found within the vessel lumen. The clearance methodology presented in this study successfully enhanced the specificity of molecular magnetic resonance imaging and opens exciting possibilities for studying detection limits and targeting kinetics of site-directed contrast agents in vivo.