Comprehensive bioinformatics analysis and experimental validation reveal the role of circadian rhythm-related genes in the crosstalk between osteoporosis and atherosclerosis.

Osteoporosis (OP) and atherosclerosis (AS) are increasingly prevalent in aging populations and frequently coexist, sharing pathological features such as abnormal vascular calcification. However, the common marker genes underlying the crosstalk between OP and AS remain poorly understood. This study aimed to identify shared marker genes and cellular mechanisms contributing to the coexistence of OP and AS. Single-cell RNA sequencing (scRNA-seq) dataset and mRNA expression profiles related to OP and AS were obtained from the Gene Expression Omnibus (GEO) database. Bioinformatics analyses were performed using the R packages Seurat, AUCell, and hdWGCNA to identify circadian rhythm-related genes (CRGs) and associated cell populations. Naturally aged mice and a 0.25% adenine (AD)-induced mouse model were established. Micro-computed tomography (µCT), immunohistochemistry (IHC), immunofluorescence, Von Kossa staining, and RT-qPCR were conducted to experimentally validate the identified common genes. In human bone marrow samples, nine cell lineages comprising 17 subpopulations were identified, while six cell lineages comprising 18 subpopulations were identified in carotid artery samples. Circadian rhythm activity was significantly enriched in bone marrow stromal cells (BMSCs) in OP and vascular smooth muscle cells (VSMCs) in AS. By integrating scRNA-seq and bulk RNA-seq analyses, 69 common genes were identified, of which 15 hub genes were further selected through protein-protein interaction (PPI) network analysis. Experimental validation demonstrated that AEBP1 was markedly upregulated in both naturally aged and AD-induced mice, accompanied by increased PLIN1 expression, reduced osteocalcin (OCN) expression, and enhanced vascular calcification. This study reveals that circadian rhythm-related regulation of BMSCs in OP and VSMCs in AS plays a critical role in their coexistence. Furthermore, we identify shared marker genes, particularly AEBP1, which may serve as potential biomarkers and therapeutic targets for the concurrent development of OP and AS.