What is Formalin Fixed Paraffin Embedded (FFPE)?
Formalin Fixed Paraffin Embedded (FFPE) is a widely used method for the preservation of biological tissues. The process involves fixing the tissue in formalin, a solution of formaldehyde in water, and then embedding it in paraffin wax. This technique preserves the tissue morphology and allows for long-term storage.
Why is Formalin Used for Fixation?
Formalin is a highly effective fixative because it creates cross-links between proteins, effectively "locking" cellular structures in place. This prevents degradation and preserves the tissue in a state that is very similar to its natural condition. Formalin fixation also inactivates infectious agents, making the tissue safer to handle.
How is Tissue Embedded in Paraffin?
After fixation in formalin, the tissue undergoes a series of dehydration steps using increasing concentrations of alcohol to remove water. It is then cleared with xylene or a similar reagent to make the tissue compatible with paraffin. Finally, the tissue is infiltrated with liquid paraffin wax and allowed to harden, creating a solid block that can be easily sectioned.
Molecular damage: The fixation process can cause cross-linking and modifications of nucleic acids and proteins, potentially affecting downstream molecular analyses.
Antigen masking: Some antigens may be masked due to cross-linking, requiring antigen retrieval techniques for immunohistochemistry.
Labor-intensive: The process involves multiple steps and requires specialized equipment and expertise.
How is FFPE Used in Research and Diagnosis?
FFPE tissues are invaluable in both research and clinical settings. In research, they provide a stable source of biological material for studies in pathology, toxicology, and molecular biology. Clinically, FFPE tissues are routinely used for the diagnosis of diseases, including cancers. Pathologists examine stained FFPE sections to identify morphological changes indicative of disease.
What is the Future of FFPE?
Advances in
molecular techniques and
digital pathology are expanding the applications of FFPE tissues. Methods such as next-generation sequencing and proteomics are being adapted to work with FFPE samples, despite the challenges posed by fixation-induced modifications. Digital imaging and machine learning are also being integrated for more precise and automated analysis of FFPE sections.
Conclusion
Formalin Fixed Paraffin Embedded (FFPE) remains a cornerstone in histology due to its ability to preserve tissue morphology and enable long-term storage. While it has some limitations, ongoing advancements in technology continue to enhance its utility in both research and clinical diagnostics.
