Fig. 2: Distinct microenvironment signalling in the metastatic leptomeninges.
a, UMAP plot of cells from Ptch-WT control leptomeninges denoted as LPT-WT (ME only) and Ptch-SB leptomeninges with metastasis denoted as LPT-MET (tumour + TME). b,c, UMAP plots of annotated cell populations from LPT-WT (ME only) (b) and LPT-MET (tumour + TME) (c). d, Interaction plot of LPT-MET samples (the edge width represents the number of significant ligand–receptor pairs between any two cell populations, and the circle sizes represent the number of cells in each population). e, Detailed pie charts showing the proportion of interactions from the metastatic cells to the TME (left) and from the TME to the metastatic cells (right). f,g, Whole-mount Ptch-SB spinal leptomeninges with metastasis (LPT-MET) fluorescently labelled with GFP+ tumour and CD31+ endothelium (scale bar, 1,500 µm) (f) and GFP+ tumour, CD31+ endothelium and laminin with tumour cells associating with larger meningeal blood vessels (left) and a smaller network of vessels (right) (n = 47 images) (g). h, Representative whole-mount spinal leptomeninges from a Pdgfra-H2BeGFP reporter mouse fluorescently labelled with GFP+ meningeal fibroblasts, collagen IV (ColIV) basement membrane and DAPI. Fibroblasts are found in the extracellular space and surround blood vessels (left). At a higher magnification, fibroblasts are shown to closely associate with blood vessels (right) (n = 15 images). i, Spinal cord cross-sections of Ptch-WT LPT-WT and Ptch-SB LPT-MET fluorescently labelled with collagen I (Col1), PDGFRα+ fibroblasts, GFP+ tumour and DAPI. The left panels show the merge, and the right panels show the GFP and PDGFRα channels (yellow arrows highlight PDGFRα+ GFP− fibroblasts). j, The proportion of PDGFRα+ fibroblasts (PDGFRα+ GFP− cells) per field of view (n = 10 and n = 12 images for LPT-WT and LPT-MET, respectively). k, Phospho-histone H3 (PH3) and PDGFRα double-positive fibroblasts normalized to PDGFRα volume quantified per field of view (n = 15 and n = 28 images for LPT-WT and LPT-MET, respectively). P values were generated from two-tailed unpaired t-test with Welch’s correction, the centre line represents the mean and error bars represent the standard deviation for j and k. Scale bars, 120 µm (g–i).
