Fig 2: FMT from healthy human controls rescued the pericyte survival reduced by MPTP. Representative immunofluorescence staining images of CD13 (green) and CD31 (red) in the striatum (A). Quantification of CD13+ cells in the striatum (B). Representative immunofluorescence staining images of CD13 (green) and CD31 (red) in the SNc (C). Quantification of CD13+ cells in the SNc (D). Representative immunofluorescence staining images of CD13 (green) and PDGFRβ (red) in the SNc (E). Quantification of both CD13+ and PDGFRβ+ cells in the SNc (F). White arrow heads indicate pericytes. Scale bars are 50 µm. Statistical analysis was performed using one-way ANOVA followed by Tukey test for multiple comparisons, with n = 4, and error bars indicate the mean ± SEM. Statistical significance was denoted by * P < 0.05, ** P < 0.01, *** P < 0.001, and **** P < 0.0001 (P values were adjusted with 6 tests). Abbreviation includes ns for no significance.

Fig 3: CD38 is predominantly expressed in the choroid plexus and localizes to pericytes.a, Coronal brain sections showing CD38 immunofluorescence staining in wild-type (WT, top) and CD38 knockout (CD38KO, bottom) mice. Red dashed boxes indicate choroid plexus regions with robust CD38 expression in lateral ventricles (boxes 1, 5) and third ventricle (box 3) in WT mice, with complete absence of signal in CD38KO mice (boxes 2, 4, 6). Scale bar, 500 μm. b, Higher magnification images of choroid plexus regions corresponding to numbered boxes in panel a, comparing CD38 immunoreactivity between WT and CD38KO mice. A strong CD38 signal is observed in WT choroid plexus structures across different ventricular locations, whereas CD38KO mice show no detectable signal, confirming antibody specificity. Scale bar, 100 μm. c, Left: Western blot analysis of CD38 expression across different brain regions (cortex, choroid plexus (ChP), hippocampus) showing the highest expression in choroid plexus, compared to cortex and hippocampus. TTR (transthyretin) serves as a choroid plexus marker, NeuN confirms neuronal tissue presence, and GAPDH serves as a loading control. Right: Quantification of CD38 protein expression intensity across brain regions, demonstrating significantly higher CD38 levels in the choroid plexus than cortex and hippocampus. Data represent mean ± s.e.m. **P<0.01 by one-way ANOVA with post-hoc analysis. d, Left: CD38 hydrolase enzymatic activity assay showing differential activity over time in different brain tissues, including ChP, hippocampus (Hippo), and cortex. Right: Relative NAD+ hydrolase activity quantification. Data represent mean ± s.e.m. (n=5–6). ****P<0.0001 by one-way ANOVA. e, Co-immunofluorescence staining of choroid plexus showing CD38 (red) expression with different cellular markers. Top: CD38 and TTR (epithelial marker, cyan); middle: CD38 and CD13 (pericyte marker, green); bottom: CD38 and CD31 (endothelial marker, purple). Merged images demonstrate CD38 predominantly localizes to pericytes (CD13-positive) rather than epithelial or endothelial cells. Scale bar, 10 μm. f, Quantification of colocalization between CD38 and different cellular markers by Pearson’s correlation coefficients, confirming the highest colocalization with CD13 (pericyte marker). n=5, Data represent mean ± s.e.m.