Tissue microdissection.

Procurement of pure populations of cells from heterogeneous histological sections can be accomplished utilizing tissue microdissection. At present, a variety of different manual and laser-based dissection tools are available and each method has particular strengths and weaknesses. The types of biomolecular analyses that can be performed on microdissected cells depend not only on the method of cell procurement, but also on the effects of upstream tissue handling and processing. Tissue preparation protocols include two major approaches; snap-freezing, or, fixation and embedding. Snap-freezing generally provides the best quality tissue for subsequent study, including proteomic analyses such as two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Tissue fixatives include either precipitating reagents or biomolecular cross-linkers. The fixed samples are then further processed and embedded in a wax medium. In general, the biomolecules recovered from fixed and embedded tissue specimens are lower in both quantity and quality than those from snap-frozen specimens, although they are useful for certain types of analyses. The protocols provided here for tissue handling and processing, preparation of tissue sections, and microdissection are derived from our experience at the Pathogenetics Unit of the National Cancer Institute.