Usually i'm reading that cryosections should be stored at -80 or -20? Although if tissue was fixed with paraformaldehyde before processing for cryosection, the slides might be stored at 4 degres. Any idea about that?
I think it will depend on what you plan to do with your sections. In theory, if the tissue was well fixed, I would think it would be ok, but I have never tried it for cryosections attached to slides. I usually only store thick cryosections (30 um or greater) that I have collected in liquid buffer at 4, and I try to react them soon after I cut them. Thinner sections (10 um) that I have cut and collected onto cold slides only thaw enough to attach to the slides, and I don't let them thaw again until I am ready to react them. Some antibodies seem to work well with either storage method.
I am not sure that there would be any benefit for 4 C storage of slides for my experiments, but I have plenty of freezer space. Personally, my worry with the thinner sections stored at 4 C would be that they would dry out, since the water content of the section is liquid, rather than frozen.