FIGURE 3.

General muscle tissue processing steps for histology and molecular analyses. Muscle tissue procurement from human and animal studies involves either a biopsy (humans) or dissections (rodents; not pictured). It is advised that the removal of visible blood, fat, and connective tissue, tissue triage, and liquid nitrogen (LN₂) tissue preservation occur as rapidly as possible (e.g., between 1 and 3 min). Noted in the diagram are different preservation methods when sampling tissue for histology vs. nucleic acid or protein work. Researchers are advised to consult with published literature based on the assays desired to be performed to ensure that tissues are placed in adequate buffers (if needed) before cold storage and/or LN₂ freezing and deep freeze storage. Upon tissue removal from deep freeze storage, care should be taken in most circumstances to ensure that the tissue is kept in a frozen state. As illustrated in the schematic, tissue processing for nucleic acid and protein work involves keeping tissue on dry ice, LN₂-cooled stages, and/or ice throughout several of the processing steps to prevent macromolecule degradation. Tissue processing for immunohistochemistry or histology on nonfixed tissue typically involves sectioning in a cryostat at approximately −20°C. Again, researchers are encouraged to consult with published literature to obtain the desired conditions based on the assay(s) desired to be performed. This schematic was constructed with BioRender.com, with permission.