Mouse hearts in OCT - freeze/thaw: damage? - (Aug/21/2012 )

Hi,

I've got whole mice hearts in oct (frozen at -80). I'm planning to do cross-sections of the heart from bottom to top. (middle parts should like a bit like "rings" because of the lumen, if you know what i mean).
The problem: some hearts have shifted position during the freezing process and are not upright in the OCT. therefore I don't know the exact orientation and may risk to not get a 90degree angle in order to obtain good sections (there is a risk i'm cutting in a weird angle because the orientation of the heart has shifted).

My question: would you have any solution to this problem?
-is there a "trick" to determine the orientation of the heart (apex/top)
-could i just thaw the section, cut the heart in half (cut hearts apparently dont change orientation during the freezing process) and refreeze? Would that considerably damage the tissue?

Thanks for your info! please specify if your info is "reliable first hand experience" or if you "just think" this might be a solution.

Regards,
batmann

Thawing will damage the structure considerably unless they have been perfused with a cryoprotectant. You may be able to melt the OCT and re-position the heart without thawing the heart, but it may take some experimentation.