Resolving the bone - optimizing decalcification in spatial transcriptomics and molecular pathology

Bone tissue poses critical roadblocks for spatial transcriptomics and molecular pathology due to a combination of its dense, calcified matrix and inadequate preservation of biomolecules in conventional decalcification. Decalcification is a complex and nuanced histological process to concomitantly preserve nucleic acids, proteins, and tissue architecture, ensuring molecular integrity for downstream assays. However, commonly used agents like formic and hydrochloric acids, while efficient, can degrade biomolecules to varying extents, complicating assays such as PCR, sequencing, immunohistochemistry, and in situ hybridization. Advances in spatial transcriptomics, both sequencing- and imaging-based, emphasize the importance of optimizing decalcification protocols to improve research outcomes. This synoptic and perspective article explores traditional and modern decalcification methods, offering recommendations on technical and methodological refinements for achieving molecularly robust processing of bone and calcified tissues in spatial transcriptomics and molecular pathology.