Decoding Cellular Communication Networks and Signaling Pathways in Bone, Skeletal Muscle, and Bone-Muscle Crosstalk Through Spatial Transcriptomics.

Bone and skeletal muscle are essential components of the musculoskeletal system, enabling movement, load-bearing, and systemic regulation. 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 to maintaining tissue integrity, and disruptions contribute to diseases such as osteoporosis, sarcopenia, and metabolic syndrome. Despite the importance of spatial context, studies using spatial transcriptomics (ST) to investigate bone-muscle interactions remain limited. Here, we applied 10X Genomics Visium ST profiling and advanced computational tools to 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, each exhibiting distinct spatial gene expression profiles. Signaling pathway analysis revealed 13 key pathways mediating intra- and inter-tissue communication, including COLLAGEN, THBS, VEGF, FN1, and TENASCIN. Notable L-R pairs involved in bone, muscle, and bone-muscle crosstalk include Col1a2-Sdc4 (osteoblast-ECM interactions), Tnxb-Sdc4 (muscle-to-endothelial signaling), Vegfa-Vegfr1 and Vegfa-Vegfr2 (muscle-to-endothelial/myeloid signaling), and Comp-Sdc4 (monocyte/macrophage-to-osteoblast signaling). This study presents the first spatially resolved map of cell-cell communication across bone and skeletal muscle, providing novel insights into their molecular crosstalk. These findings offer a critical foundation for future therapeutic strategies targeting musculoskeletal disorders.