I was wondering if anyone could provide feedback/data on whether it is best in terms of preserving tissue quality to freeze tissue in OCT using dry ice versus liquid nitrogen?
3 Comments
Chris D. Pacheco, PhD
August 22, 2012
When I was in grad school at the University of Michigan, I worked in the hospital with a neuropathologist (Andy Lieberman) and we commonly used OCT. Our standard protocol was to add the tissue to an OCT aliquot, then freeze at -20 C on the benchtop while we procured other samples, then transfer all the samples to liquid nitrogen. I’m pretty sure long term storage in liquid nitrogen is safer.
Sorry I don’t have any data to support these techniques, but I don’t think you can go wrong with liquid nitrogen storage.
I agree this demonstrates the need for protocols for Biospecimen preservation.
But it goes back to the question, what is the purpose of the specimen? In such, the fit for purpose model will apply.
OCT frozen specimens are superior for cutting H&E and pathological findings, as well as IHC, Insitu, and LCM procedures. Although a LN2 frozen specimen can be achieved with these applications, you would then end up re-freezing the specimen in the OCT after the fact.
If the purpose is to extract RNA, DNA or protein from a homogenate , then the LN2 freezing method is superior.
When deciding on the method of choice for your specimens, look at the end results you want to achieve with that specimen, and if the study has not been fully designed or broken down, go with the LN2.
I fully agree with the arguments of Barb. Especially when future studies are not known or not fully developed, you should always consider the method of storing which allows for the most diverse research analysis applications. RNA and protein applications are known to be the most sensitive for contamination (e.g. RNase) and/or manipulation (e.g. freeze artifacts). So tissue storage in LN2 (and preferably applying snap-freezing) would be the most sensible thing to do.
3 Comments
Chris D. Pacheco, PhD
August 22, 2012When I was in grad school at the University of Michigan, I worked in the hospital with a neuropathologist (Andy Lieberman) and we commonly used OCT. Our standard protocol was to add the tissue to an OCT aliquot, then freeze at -20 C on the benchtop while we procured other samples, then transfer all the samples to liquid nitrogen. I’m pretty sure long term storage in liquid nitrogen is safer.
Sorry I don’t have any data to support these techniques, but I don’t think you can go wrong with liquid nitrogen storage.
Barb Pruetz, HTL (ASCP)
August 22, 2012I agree this demonstrates the need for protocols for Biospecimen preservation.
But it goes back to the question, what is the purpose of the specimen? In such, the fit for purpose model will apply.
OCT frozen specimens are superior for cutting H&E and pathological findings, as well as IHC, Insitu, and LCM procedures. Although a LN2 frozen specimen can be achieved with these applications, you would then end up re-freezing the specimen in the OCT after the fact.
If the purpose is to extract RNA, DNA or protein from a homogenate , then the LN2 freezing method is superior.
When deciding on the method of choice for your specimens, look at the end results you want to achieve with that specimen, and if the study has not been fully designed or broken down, go with the LN2.
B.W.D. de Jong PhD
August 22, 2012I fully agree with the arguments of Barb. Especially when future studies are not known or not fully developed, you should always consider the method of storing which allows for the most diverse research analysis applications. RNA and protein applications are known to be the most sensitive for contamination (e.g. RNase) and/or manipulation (e.g. freeze artifacts). So tissue storage in LN2 (and preferably applying snap-freezing) would be the most sensible thing to do.