Full original research code of Integrative Analysis Coupled with In Vitro Validation Reveals KAZN and SUPT3H as Shared Negative Regulators in Osteosarcopenia

Osteosarcopenia, defined by the coexistence of sarcopenia and osteoporosis, is increasingly recognized as a systemic musculoskeletal aging syndrome, but shared molecular regulators of bone–muscle deterioration remain incompletely understood. Here, we integrated bulk transcriptomic datasets from sarcopenic skeletal muscle and osteoporosis peripheral blood mononuclear cells to identify shared differentially expressed genes, followed by two-sample Mendelian randomization using osteoporosis GWAS summary statistics to prioritize genes with potential causal relevance. Diagnostic performance, functional enrichment, immune infiltration, single-cell RNA sequencing, regulatory network reconstruction, compound prediction, and siRNA-mediated validation in C2C12 and MC3T3-E1 cells were performed. We preliminarily screened 122 shared differentially expressed genes and tentatively proposed KAZN and SUPT3H as candidate genes genetically associated with osteoporosis risk. Both genes were upregulated in disease groups and showed modest-to-moderate diagnostic performance. Knockdown of Kazn or Supt3h promoted myogenic differentiation in C2C12 cells and osteogenic differentiation and mineralization in MC3T3-E1 cells, supporting their roles as negative regulators of lineage differentiation. Functional analyses linked KAZN mainly to mitochondrial-related programs and SUPT3H to immune signaling, while single-cell analyses localized these genes to stromal, progenitor, and immune-related compartments. These hypothesis-generating findings suggest that KAZN and SUPT3H may participate in shared bone–muscle dysfunction and generate candidate genes and mechanistic hypotheses for subsequent functional validation and translational research.