Tissue was collected and fixed, and sections were prepared as previously described [12 (link)]. The following antibodies were used: CC1 1: 250 (Millipore OP80), CNPase 1: 200 (Sternberger SMI91) (Covance, Princeton, NJ, USA), GFAP 1: 200 (Dako Z0334), Iba1 1: 150 (Wako 019-19741), MBP 1: 500 (Sternberger SMI99), Olig1 1: 600 (Chemicon AB5540) (EMD Millipore, Billerica, MA, USA), Olig2 1: 400 (Chemicon AB9610), O4 1: 250 (EMD Millipore MAB345), PDGFRA 1: 200 (Fitzgerald CD140a) (Fitzgerald, North Acton, MA, USA), pSMAD1/5/8 1: 50 (Cell Signaling 9511) (Cell Signaling Technology, Danvers, MA, USA), Alexa Fluor 488 goat anti-rabbit 1: 500, Alexa Fluor 594 goat anti-mouse IgG1 1: 500, Alexa Fluor 594 goat anti-mouse IgG2b 1: 500, Alexa Fluor 594 goat anti-mouse IgM 1: 500, and Alexa Fluor 647 goat anti-mouse IgM 1: 500 (Invitrogen) (Life Technologies, Grand Island, NY, USA). Confocal images were obtained using the Zeiss LSM 880 microscope at the Stanley Manne Children’s Research Institute.