Single-cell RNA sequencing profiles drug activity within spatially engineered 3D cultures

Spatial transcriptomic techniques provide a wealth of information useful in guiding drug development, while three-dimensional (3D) cell cultures have demonstrated power in accelerating drug approvals. However, techniques for robust spatial analysis of 3D cultures are limited. Here, we present a transfection-based method for constructing cellular spheroids through a layer-by-layer approach, in which DNA barcodes encode the spatial positioning of cells. Our technique facilitates multiplex single-cell RNA sequencing, providing spatial maps of gene expression and drug response, while correlative imaging reveals the locations of barcoded cell populations and quantifies local tissue elasticity. We show that model HeLa 3D spheroids display heterogeneous responses to drugs, which may arise through diffusion gradients of the drug, or from differences in metabolism, nutrient supply, and cellular stressors. The ability to create spatially encoded cellular assemblies may help to reveal spatial variation in gene expression within 3D culture models.