Oil Red O Staining of Cryosections and Cells

Fixed zebrafish larvae were dehydrated in 30% sucrose at 4°C for 3 days, embedded in optimal cutting tissue (OCT) compound (Leica, Germany), and sliced into 14 μM sections. Cryosections were washed with water to remove OCT, incubated in 100% 1,2-propylene glycol for 5 min, and stained with 0.7% Oil Red O at 60°C for 10 min in the dark. Excess dye was rinsed off with 85% 1,2-propylene glycol and PBS to keep the background clean. Sections were imaged using a Nikon Eclipse Ni-U light microscope (Nikon, Tokyo, Japan).

The Oil Red O staining procedure for cells was the same as that of cryosections. The fixed cells were washed with PBS, incubated with 100% 1,2-propylene glycol, stained with 0.7% Oil Red O, and decontaminated in 85% 1,2-propylene glycol and PBS. The staining results were imaged using a Nikon Eclipse Ni-U optical microscope (Nikon, Tokyo, Japan).