hCSs were fixed in 4% paraformaldehyde (PFA) overnight. They were then washed in PBS, transferred in a 30% sucrose solution and kept at 4 °C for 48–72 h. Subsequently, they were transferred into embedding medium (Tissue-Tek OCT Compound 4583, Sakura Finetek), snap-frozen on dry ice and stored at −80 °C. For immunohistochemistry, 10 μm thick sections were obtained using a cryostat.
