Hi Airton

you can store samples in RNAlater solution, but the best way for omics studies is far away to extract RNA from fresh tissues, avoiding degradations.

all the best

fred

You probably want to cut the hearts into smaller pieces before dropping them into the RNAlater (the suggested size is somehwere in the RNAlater protocol), the important bit here is to follow the storage protocol, allowing permeation of the tissue before storing in freezer - I've done this with mouse livers and had excellent and reproducable RNA integrity after several months, though I didn't do RNASeq with those samples... but RIN of >8 wasn't an issue.

Petra Disterer Thank you for your answer, I learned the hard way to not put tissues in RNA Later and immediately snap freeze!

Airton Pereira e Silva Doing a test-run with samples that aren't worth much and minimizing risk wherever you can is always a good idea. In one of my experiments 12 mouse livers were worth £30k - so I put each of my samples in two separate RNAlater containers stored in two separate freezers... I extracted and analysed each sample twice independently...

Re good RNA integrity - many researchers blame the kit/storage when most likely it is their lab technique that leads to RNA degradation. Again, test-runs will help there...

Immediate submersion in RNAlater is important - I've seen people extract organs from all their mice, carry them to their lab and then put them all into RNAlater there, and also have done tests on how long it takes for degradation to set in if you delay submersion... 5 min was ok (= RIN>9), >30 min was borderline (= RIN~8), >1h was unusable. So I took prepared containers with RNAlater into the mouse unit and extracted each liver, cut them into pieces and immediately added them to the containers. At this stage there's no need to be RNase free as the RNases within the cells are much more likely to be the issue.

The time issue could partly explain how some people get RIN of >9 all the time and others don't... but apparently you also have to really avoid cutting the mouse gall bladder!

I also discussed the time issue with one of the human tissue bank coordinators - apparently they had consistently bad RNA... turns out a theatre nurse would just put the tissue sample or extracted organ from transplant patients on ice and then give it to the tissue bank collector AFTER the surgery finished to not to break sterility of the operating theatre and herself... we solved it by making the collector scrub in to wait for the sample.

Random mouse hearts shouldn't be hard to come by - just ask the Animal technichian/other researchers if they have any that will be culled or are superfluous to breeding.

Petra Disterer Sure, I will run some tests, but I won´t wait until I get back to the lab to put sampels in RNAlater. I take some eppis or cryo vials with me to the animal facility, so I can immediately put sampels in RNAlater.