Decoding cellular communication networks and signaling pathways in bone, skeletal muscle, and bone-muscle crosstalk...

Bone and skeletal muscle are essential components of musculoskeletal system, enabling movement, load-bearing, and systemic homeostasis. These tissues communicate through dynamic bone-muscle crosstalk mediated by cytokines, growth factors, and extracellular-matrix (ECM) proteins. The spatial organization of these mediators is critical for maintaining tissue integrity, and its disruption contributes to diseases, such as osteoporosis, sarcopenia, and metabolic syndrome. Despite this importance, spatial transcriptomics (ST) studies of bone-muscle interactions remain limited. Here, we applied 10x Genomics Visium ST with computational tools, e.g., SMART and CellChat, to deconvolute cell-type composition and characterize cell-cell communication networks and ligand-receptor (L-R) interactions in mouse femur and adjacent skeletal muscle. We identified eight major cell types (erythroid cells, endothelial cells, skeletal muscle cells, osteoblasts, myeloid cells, monocytes/macrophages, mesenchymal stem cells, and adipocytes) with distinct spatial transcriptional profiles and thirteen CellChat-inferred pathways, such as ECM-receptor related (e.g., COLLAGEN, TENASCIN, THBS) and secreted-signaling involved (e.g., VEGF) pathways. Representative L-R pairs include Col1a1/Col1a2-Sdc4, mediating osteoblast-to-muscle interactions, and Col4a1-Sdc4, facilitating muscle-to-osteoblast interactions in COLLAGEN, Tnxb-Sdc4 in TENASCIN, supporting muscle-to-osteoblast/muscle/myeloid/endothelial communication, Comp-Sdc4 in THBS, driving monocyte/macrophage-to-osteoblast/muscle signaling, and Vegfa-Vegfr1/Vegfr2 in VEGF, mediating muscle-to-endothelial/myeloid signaling. Immunostaining validated colocalization of several representative L-R pairs with their corresponding cells. Additionally, independent mouse and human bone scRNA-seq datasets reproduced most of the pathways and L-R pairs identified in ST, underscoring the robustness and cross-species relevance of our findings. Together, we present an initial spatially resolved transcriptome-wide map of bone-muscle intercellular communication, providing novel insights into molecular crosstalk and establishing groundwork for future studies in musculoskeletal disorders.