Optimal cutting temperature medium-embedding and cryostat sectioning is valid for cardiac myofilament function-assessment.

To maximize data obtainment from valuable cardiac tissue, we hypothesized that myocardium fixed in optimal cutting temperature (OCT) medium for histology could also be used to investigate function of myofilament proteins in situ. We compared tissue prepared via conventional liquid nitrogen (LN) snap freezing, to tissue fixed in OCT and then sectioned in fibre-parallel orientation. We found that actin-myosin Ca2+ sensitivity, activation rate by Ca2+, cooperativity along the thin filament, as well as cross-bridge cycling rate was unaffected by OCT storage, and could reliably by interpreted after sectioning. Absolute values in maximum force generation per cross sectional area, as well as passive strain, are difficult to investigate after sectioning, as myofibrillar continuity along the preparation cannot be guaranteed. We have shown that myocardial tissue stored in OCT and sectioned before analysis are available for functional analysis, a valuable means of maximizing usage of precious cardiac biopsies.