Fig. 3

Regional changes in the immunoreactivity for PDGFRβ (A) and CD13 (B) in murine parietal cortices during PM. Brain sections were obtained from healthy controls (upper images) as well as infected mice at 18 and 42 h (h) after intracisternal application of S. pneumoniae (p.i. = post-infection; 3 mice per group, #1, #2, and #3; middle and lower images, respectively). The sections were stained either with anti-murine PDGFRβ or anti-murine CD13 antibodies and counterstained with hematoxylin–eosin. The scale bars on the lower middle images indicates 100 µm in length. PDGFRβ immunoreactivity appeared regionally disrupted (grey asterisks) and was missing at some vascular segments (black arrow), whereas in other vascular segments, PDGFRβ staining appears unchanged or even enhanced (red arrows). The determination of the disease phenotype 42 h after infection (C–E) showed a clear worsening of clinical symptoms in tamoxifen (TAM)-treated PDGFRB::creER2-iDTA mice (PDGFRβ-iDTA) which were largely missing pericytes, compared to corn oil (CO)-treated PDGFRB::creER2-iDTA mice (controls), as evidenced by significantly increased clinical score values (E), more restricted motor activities in the open-field test (OFT) (D), and lower body temperatures (E). The worsening of disease was associated with increased brain edema formation, as evidenced by increased brain albumin concentrations 42 h after infection (F) and enhanced Evans blue extravasation 24 h after infection (G, H) in TAM-treated PDGFRB::creER2-iDTA mice compared to controls. G Representative brain images taken immediately after perfusion and removal from one control mouse, one TAM- and one CO-treated PDGFRB::creER2-iDTA mouse (upper images) as well as the associated Evans blue extracts. Data are given as individual values as well as means ± SD. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001, using ANOVA with Tukey’s multiple comparisons test