Spatially Resolved Single Cell Transcriptomic Profiling in Formalin-Fixed Paraffin-Embedded (FFPE) Tissues

Formalin-fixed paraffin-embedded (FFPE) tissues are the most widely used clinical sample types in histology and molecular diagnosis, but these samples are often challenging for single-cell transcriptomic analysis due to RNA degradation and protein crosslinking. A spatial transcriptomics technique with high detection efficiency and single molecule resolution is required in order to accurately profile the gene expression in FFPE samples in situ. Vizgen’s MERSCOPE platform, built on multiplexed error robust in situ hybridization MERFISH technology, directly profiles intact tissue’s transcriptome with subcellular spatial resolution. Here, we demonstrate the FFPE MERSCOPE workflow in tissues from 10 mouse and human samples, including archival clinical samples. In each sample, hundreds of thousands of cells were captured with >100 million transcript counts, generating detailed spatial transcriptomic data for the profiled genes in each sample. A comparison of FFPE and matched fresh frozen samples indicated that the FFPE workflow performs similarly in detection efficiency as compared to the fresh frozen protocol. We further demonstrated the MERSCOPE FFPE workflow is compatible with protein imaging by performing simultaneous protein-based cell boundary staining with MERFISH to accurately profile gene expression and map cell types in archival clinical human samples. Finally, we constructed a spatially resolved single cell atlas across eight major tumor types, mapped and cataloged different cell types within the tumor microenvironment and systematically characterized the gene expression among cells. This study demonstrates the potential for spatially resolved transcriptomic profiling of FFPE samples at single cell level to contribute to a wide range of biomedical research areas, including many applications to study human diseases. Citation Format: Jiang He, Justin He, Timothy Wiggin, Rob Foreman, Renchao Chen, Nicolas Fernandez, George Emanuel. Spatially resolved single cell transcriptomic profiling in formalin-fixed paraffin-embedded (FFPE) tissues. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4195.