Spatially resolved transcriptomics has revolutionised the study of the gene expression within tissues, allowing researchers to maintain the spatial context. Accompanying these spatial transcriptomics datasets are often histology images, providing rich information on tissue architecture, organisation and pathology, complementing the spatial gene expression. However, in traditional pipelines, histological information is typically discarded during tasks such as dimensionality reduction of the spatial transcriptomics data.
To address this limitation, we propose Cellpie, a novel approach based on fast, joint non-negative matrix factorisation (NMF). Cellpie simultaneously decomposes spatial gene expression and histology image features into interpretable components. Through joint NMF, CellPie generates non-negative factor matrices representing parts-based representation (factors) of the data, facilitating the identification of biologically relevant patterns of variation. In addition, CellPie extracts the corresponding leading genes and image features that are strongly associated with each factor. These genes and features serve as marker genes and morphological characteristics, respectively, providing insights into the biological processes underlying the observed patterns in the spatial gene expression data. Furthermore, they enable the discoverer of links between molecular signalling and tissue morphology.
We demonstrated CellPie on two distinct tissue types, showcasing its improved accuracy in downstream analysis tasks compared to published dimensionality reduction methods.