Tissue-Tek O.C.T. is an embedding compound for cryosectioning, which is soluble in water. It mainly consists of glycols and synthetic resins. Tissue-Tek O.C.T. is used as matrix for cryosectioning of tissues. Using the O.C.T. the tissue samples can be positioned more easily in the microtome and have better qualities during sectioning.
Most cryosections are fixed using non-crosslinking agents. For isolation of RNA from tissue embedded in Tissue-Tek O.C.T. using non-crosslinking agents the RNeasy Plus Micro Kit or the RNeasy Micro Kit (Protocol: Total RNA Isolation from Microdissected Cryosections), or the RNeasy Mini Kit (RNeasy Mini Protocol for the isolation of Total RNA from Animal Tissue) give great results. We strongly recommend removing as much of the embedding compound as possible prior to RNA extraction from the sections. Please see QIAGEN News article, Issue 1 1998, 'Effects of malnutrition on expression of lactase in children' for successful RNA isolation from O.C.T.-embedded tissue using the RNeasy Mini Kit.
In case crosslinking agents (e.g. formaldehyde or glyoxal-containing) were used for fixation of the tissue for cryosectioning the RNeasy FFPE Kit is the perfect choice. The RNeasy FFPE Kit is especially designed for purifying total RNA from formalin-fixed tissue sections. Special lysis and incubation conditions reverse formaldehyde modification of RNA for improved results in downstream application. The crosslinking causes the RNA to break, resulting in overall smaller molecules, which look like a smear when analyzed on a formaldehyde gel.
In case DNA as well as RNA from precious samples is of interest from the identical sections, please have a look at the AllPrep DNA/RNA Kits for unfixed tissue or the AllPrep DNA/RNA FFPE Kit for fixed tissue.