Evaluation of Long-Term Cryostorage of Brain Tissue Sections for Quantitative Histochemistry

Storage of tissue sections for long periods allows multiple samples, acquired over months or years, to be processed together, in the same reagents, for quantitative histochemical studies. Protocols for freezer storage of free-floating frozen sections using sucrose with different additives have been reported and assert that storage has no effect on histochemistry, but no quantitative support has been provided. The present study analyzed the efficacy of long-term storage of brain tissue sections at -80C in buffered 15% glycerol. To determine whether histochemical reactivity is affected, we analyzed 11 datasets from 80 monkey brains that had sections stored for up to 10 years. For processing, sections from multiple cases were removed from storage, thawed, and batch-processed at the same time for different histochemical measures, including IHC for neuronal nuclear antigen, parvalbumin, orexin-A, doublecortin, bromodeoxyuridine, the pro-form of brain-derived neurotrophic factor, and damaged myelin basic protein as well as a histochemical assay for hyaluronic acid. Results were quantified using stereology, optical densitometry, fluorescence intensity, or percent area stained. Multiple regression analyses controlling for age and sex demonstrated the general stability of these antigens for up to a decade when stored in 15% glycerol at -80C.