Single-cell RNA-seq of human head and neck squamous cell carcinoma (HNSCC) to compare different tissue dissociation methods

Tissue dissociation, mechanical and/or enzymatic, is a method of disaggregating 3D connective tissue to release cells for downstream single cell analysis. Without proper controls for tissue dissociation experiments, potential artifacts can be mistaken for baseline tissue data. We hypothesized that enzymatic (collagenase/hyaluronidase) compared to mechanical dissociation leads to dissociated related artifacts not found in endogenous tumor tissue. To distinguish artifacts between enzymatic and mechanical dissociation, we compared separate enzymatic and mechanical dissociated samples with baseline samples from healthy and tumor patient whole blood, melanoma and head and neck squamous cell carcinoma (HNSCC) tumor tissues in flow cytometry, RNA sequencing and CODEX experiments. In bulk sorted tumor tissue, there is a significant difference between enzymatic and mechanical digested samples in cell stress, heat shock proteins and cell death related genes. These genes were also significantly upregulated in enzymatic over mechanical samples in the single cell RNA sequencing HNSCC tissue data. Fibroblasts and CD39+CD103+ CD8 T cells from tumor tissue, appear to require enzymatic digestion for efficient release from tissue compared to the mechanical digested samples. CD39+CD103+ CD8 tumor infiltrating lymphocytes (TILs) show different phenotypes depending on dissociation technique and tumor tissue. In tumor tissue, CD3+CD8+CD69+ T cells and gene expression were elevated in the enzymatic samples over the mechanical and baseline frozen tissue. Tissue dissociation techniques and tissue analysis from downstream applications have the potential for dissociation related artifacts that can mislead both protein and RNA sequencing data analysis in cancer research. Overall design: Two samples from the same human HNSCC patient with mechanical and enzymatic digestions respectively