Fig. 2

Confocal microscopy images from brains of TgBAC(pdgfrb:EGFP/Tg(fli 1 a:Myr-mCherry) transgenic zebrafish embryos that have had vehicle (uninfected controls, A–C) or S. pneumoniae (meningitis, D–F) injected into their hindbrain ventricles (three representative examples each). The embryos express eGFP in mural cells (namely, pericytes) and mCherry in endothelial cells. White bold arrows: compared to controls, infected embryos showed a marked reduction in mCherry-positive cells indicating meningitis-associated endothelial cell destruction (D–F). Thin double-headed arrows: a strong decrease in eGFP-positive cells was seen in some infected embryos, suggesting pericyte loss (E, F). Thin arrows: in others, there was predominantly a loss of contact between eGFP-positive and mCherry-positive cells (D, E). The scale bar indicates 100 μm length. (A–F). Effect of pharmacological pericyte depletion on the survival of wild-type (on the left) and TgBAC(pdgfrb:EGFP/Tg(flila:Myr-mCherry; on the right side) zebrafish embryos (G, H). Wild-type embryos were injected with 1900 cfu of live S. pneumoniae (= meningitis; or phenol red solution = controls; G); TgBAC(pdgfrb:EGFP/Tg(flila:Myr-mCherry embryos received 2200 cfu of live S. pneumoniae (= meningitis; or phenol red solution = controls, H). Embryos were treated either with DMSO as a placebo or the PDGFRβ inhibitor AG1296. Data are given as means ± SEM. Histopathological analysis of non-infected and Streptococcus pneumonia-infected wild-type zebrafish embryos treated either with DMSO as placebo (I–L) or the PDGFRβ inhibitor AG1296 (M–P) at 32 h post-injection (hpi). White arrows in M: embryos treated with AG1296 showed multiple cystic abnormalities in their eyes, compared to placebo-treated embryos (I). After S. pneumoniae infection, placebo- and AG1296-treated embroys showed signs of meningitis with presence of polymorphonuclear leukocytes in the ventricles (black asterisks) (K, O). White arrow heads in O: the brain parenchyma of AG1296-treated, infected embryos showed distinct edema, while the parenchyma of placebo-treated, infected embryos remained compact (K). Black arrows in L, P: the perivascular space was broadened in AG1296-treated embryos, compared to placebo-treated embryos