Tissue tablet method: an efficient tissue banking procedure applicable to both molecular analysis and frozen tissue microarray

Frozen human tissues are necessary for research purposes, but tissue banking methods have not changed for more than a decade. Many institutions use cryovial tubes or plastic molds with an optimal cutting temperature compound. However, these methods are associated with several problems, such as samples sticking to one another and the need for a larger storing space. We established an efficient tissue freezing and storing procedure ("tissue tablet method") applicable to both molecular analysis and frozen tissue microarray. Tissue samples were chopped into tiny fragments and embedded into tablet-shaped frozen optimal cutting temperature compound using our original tissue-freezing plate. These tablets can be sectioned and stored in cryovial tubes. We compared the tissue quality of tablet-shaped samples with that of conventional optimal cutting temperature blocks and found no significant difference between them. Tissue microarray is a key method to utilize tissue-banking specimens. However, most tissue microarrays require the coring out of cylindrically shaped tissues from formalin-fixed, paraffin-embedded tissue blocks. Antigenic changes and mRNA degradation are frequently observed with formalin-fixed, paraffin-embedded samples. Therefore, we have applied tablet-shaped samples to construct frozen tissue microarrays with our original mounting base. Constructed tissue microarray sections showed good morphology without obvious artifact and good immunohistochemistry and in situ hybridization results. These results suggest that the quality of arrayed samples was sufficiently appropriate for research purposes. In conclusion, the tissue tablet method and frozen tissue microarray procedure can save time, provides easy tissue handling and processing, and satisfies the demands of research methodologies and tissue banking.