Cerebellar slice cultures derived from P0-2 mice (Figure 1A) were used to study myelination and assess the effects of the addition of various factors from 0–12 DIV (Figure 1B). To study remyelination, slice cultures at 14 DIV were first demyelinated with lysolecithin and allowed to remyelinate for 14 additional days in culture with the tested factors (Figure 1C), after which remyelination was quantified. The effect of hypoxia on myelination was also studied by placing slice cultures in a 2% FiO2 hypoxic incubator for 24 h, from 2–3 DIV (Figure 1D). Lastly, slice cultures derived from transgenic mice were used to study the effect of gene knockouts on myelination. In this system, Cre recombination was induced by the addition of tamoxifen or Ad-Cre adenovirus at 1 DIV and 3 DIV, and slice cultures fixed for analysis at 12 DIV (Figure 1E). After fixation of tissues, quantification of demyelination and remyelination was carried out by immunostaining (Figure 2, Figure 3) and electron microscopy11,12,13.
Representative data shown (Figure 2, Figure 3) illustrate the dynamic range of myelination and remyelination in slice cultures. The myelination index was quantified by the ratio of Caspr, a paranodal marker that is an indirect readout of compact myelin, to neurofilament protein H (NFH), which stains axons. This myelination index has been validated to represent formation of compact myelin by electron microscopy and sodium channel staining12. Lysolecithin-induced demyelination9,10 led to complete disappearance of Caspr-positive paranodes (myelination index = 0, Figure 3A) and loss of compact myelin, which was restored during remyelination11,12.
To demonstrate a positive result on myelination, slices were cultured with Activin A following the timeline in Figure 1B. Activin A engages activin receptors on oligodendrocytes and drives oligodendrocyte differentiation and myelin compaction15. The representative data show that treating slices with 100 ng/mL of Activin A during myelination resulted in a higher myelination index (Figures 2A,B). Consistent with this, Activin A treatment accelerated OPC differentiation, as quantified by the ratio of CC1-positive mature oligodendrocytes to Olig2+ oligodendrocyte lineage cells11,13 (Figures 2C,D).
A small molecule inhibitor of Tankyrase, XAV939, has been shown to promote myelination and remyelination by stabilization of Axin2 levels in oligodendrocytes11. Following lysolecithin treatment, demyelination was visualized and quantified in slice cultures by fragmented myelin basic protein (MBP) staining and lack of Caspr-positive paranodes (Figures 3A). Treatment with 0.1 μM XAV939 during remyelination (15-28 DIV) significantly increased the myelination index compared to vehicle controls, as quantified by the ratio of Caspr to NFH staining (Figures 3B, C). The slice culture model can thus be used to examine and quantify effects on OPC differentiation, myelination, and remyelination in intact tissue.

Figure 1: Schematic of cerebellar slice cultures showing key steps in the dissection process and timelines for different slice culture protocols. (A) Depiction of steps to generate slice cultures: dissection of brains from P0–2 mouse pups, trimming the brain (as shown), cutting the brain with a tissue chopper to generate 350 µm sagittal slices, placing slices on organotypic culture inserts in a 6 well dish, and incubating at 37 °C and 7.5% CO2. * denotes cerebellum. (B) Timeline for myelinating slice cultures. Slice cultures were incubated for 12 days before fixation for analysis. (C) Timeline for remyelinating slice cultures. Slices were treated with lysolecithin at 14 DIV for 16–18 h to induce complete demyelination and allowed to remyelinate until 28 DIV before fixation for analysis. (D) Timeline for myelination following hypoxic insult. Slices were exposed to an acute hypoxic insult for 24 h between 2–3 DIV, which caused hypomyelination. (E) Timeline for CSC from genetically modified mice. Tamoxifen (Tam, 100nM) or Ad-Cre virus was added at 1 DIV and 3 DIV to induce genetic modification, and slices were analyzed at 12 DIV. Timeline diagrams adapted from previous publications11,13. Please click here to view a larger version of this figure.

Figure 2: Representative data showing Activin A promotes myelination and OPC differentiation. (A) Increase in myelination (MBP) and paranodes (Caspr) with 100 ng/mL Activin A treatment, shown by immunostaining of slice cultures. (B) Quantification of myelination index (ratio of area stained for Caspr+ paranodes to area stained for NFH+ axons). (C) Quantification of OPC differentiation (ratio of CC1+ oligodendrocytes to Olig2+ oligodendrocyte lineage cells). (D) Representative images of CC1/Olig2 staining. Values shown are mean + standard deviation. ****P < 0.0001; unpaired T-test. Scale bars: A = 25 µm, D = 50 µm. Please click here to view a larger version of this figure.

Figure 3: Representative data showing XAV939 promotes remyelination. (A) Images showing demyelination by fragmented MBP staining and lack of Caspr paranodes in slice cultures treated with lysolecithin. (B) Increase in remyelination (MBP) and paranodes (Caspr) with 0.1 µM XAV939 treatment following lysolecithin-induced demyelination shown by immunostaining of slice cultures. (C) Quantification of myelination index (ratio of area stained for Caspr+ paranodes to area stained for NFH+ axons). Values shown are mean + standard deviation. ****P < 0.0001; unpaired T-test. Scale bars = 25 μm. Please click here to view a larger version of this figure.
| Slice culture media (SCM) | |
| Volume | Reagent |
| 100 mL | Minimum Essential Media (MEM), HEPES, no glutamine |
| 50 mL | Heat-inactivated horse serum |
| 50 mL | Earle’s balanced salt solution |
| 2 mL | Penicillin-streptomycin 10,000 U/mL |
| 2 mL | GlutaMAX supplement |
| 2888 μL | 45% glucose solution |
| 1 mL | Fungizone |
| Sterile filter through a 0.22 µm filter and store in 4 °C fridge for up to 2 weeks. |
| Dissection media (DM) | |
| Volume | Reagent |
| 100 mL | MEM, HEPES, with Earle’s salts |
| 1 mL | Penicillin-streptomycin 10,000 U/mL |
| Sterile filter through a 0.22 µm filter and store in 4 °C fridge for up to 2 months. |
| Lysolecithin stock (125 mg/mL) | |
| Amount | Reagent |
| 100 mg | Lysolecithin |
| 0.8 mL | Sterile PBS |
| Dissolve 100 mg of lysolecithin in 0.8 mL of sterile PBS. Store 80 µL aliquots of stock solution at -20 °C. |
| Before use, thaw 80 µL aliquot and dissolve in 20 mL of SCM (0.5% lysolecithin in SCM), warmed in 37 °C, 7.5% CO2 incubator. If needed, vortex to dissolve lysolecithin into SCM. |
Table 1: List of components and protocol to make slice culture medium (SCM), dissection medium (DM), and lysolecithin solution.