RNA samples preserved at -80 temperature were lost due to the failure of the freezer and raised its temperature to +15, and that long period led to the destruction and loss of RNA, but we have tissue samples preserved in 10% formalin for the purposes of pathohistological study and are widely available,, My question Is it possible to take a part of each sample to extract RNA in high quantity and purity? What is the appropriate protocol to do this, whether by Triazole or other protocols
You can extract RNA but it won't be very high quality - formalin fixation results in crosslinking so when you do the RNA extraction, the crosslinks break apart, also breaking the RNA.
Hello Tareq Al-Omari
Additionally, I would like to mention the following.
The validity of molecular studies using RNA extracted from decades‐old formalin‐fixed and embedded tissue blocks is well documented. Formalin‐fixed samples are, however, known to be poor materials for molecular biological applications.
The aim of the study attached was to investigate the effect of formalin as a preservation agent on RNA quality and relevant molecular applications.
Methods: The quantity and quality of RNA from liver tissues are modified by the fixation time. Rat liver tissues were harvested and fixed for 4, 8, 12, and 24 h in 10% buffer formalin, and only 9% of RNA could be extracted from the formalin‐fixed tissue stored for 4 h.
Results: Agarose gel electrophoresis did not show the characteristic pattern of RNA with 18S and 28S in all lanes. Based on the results, it is thought that the RNA was damaged owing to one or more of the following reasons: 1) formalin directly degrades RNA, 2) formalin inactivates RNase, and/or 3) formalin destroys the reagent for extraction of RNA. In this study, it was shown by electrophoresis that very little RNA was extracted by Trizol with 1% formalin.
Conclusions: Formalin has direct and indirect ill effects on RNA during the extraction process.
Please refer to the article attached for more information.
Article Effect of formalin on extraction of mRNA from a formalin-fix...
Best.
I had the experience with paraffin samples for RNA extraction. I used the Qiagen RNeasy kit for the purification of total RNA from formalin-fixed, paraffin-embedded tissue sections. The kit has a step to remove the paraffin. It works with my samples. I hope it could work for you.
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