Cell simulation as cell segmentation.

Single-cell spatial transcriptomics promises a highly detailed view of a cell's transcriptional state and microenvironment, yet inaccurate cell segmentation can render these data murky by misattributing large numbers of transcripts to nearby cells or conjuring nonexistent cells. We adopt methods from ab initio cell simulation, in a method called Proseg (probabilistic segmentation), to rapidly infer morphologically plausible cell boundaries. Benchmarking applied to datasets generated by three commercial platforms shows superior performance and computational efficiency of Proseg when compared to existing methods. We show that improved accuracy in cell segmentation aids greatly in detection of difficult-to-segment tumor-infiltrating immune cells such as neutrophils and T cells. Last, through improvements in our ability to delineate subsets of tumor-infiltrating T cells, we show that CXCL13-expressing CD8⁺ T cells tend to be more closely associated with tumor cells than their CXCL13-negative counterparts in data generated from samples from patients with renal cell carcinoma.