Chronic Alcohol Consumption Enhances the Differentiation Capacity of Hematopoietic Stem and Progenitor Cells into Osteoclast Precursors

Chronic alcohol consumption (CAC) is associated with an enhanced risk of bone fracture, reduced bone density, and osteoporosis. In a rhesus macaque model of voluntary ethanol consumption, CAC induces functional, transcriptomic, and epigenomic changes in hematopoietic stem and progenitor cells (HSPCs) and their resultant monocytes/macrophages, skewing them toward a hyper-inflammatory response. In the present study, those studies were extended to investigate alterations in osteoclast development, which, in postnatal life, differentiate from HSPCs and play a critical role in maintaining bone homeostasis. Spectral flow cytometry revealed a skewing of HSPCs toward granulocyte-monocyte progenitors in the CAC group, consistent with an increased number of colony-forming unit-granulocyte/macrophage colonies. In addition, HSPCs from animals in the CAC group incubated with macrophage colony-stimulating factor and receptor activator of NF-κB ligand were more likely to differentiate into osteoclasts, as evidenced by increased tartrate-resistant acid phosphatase staining and bone resorption activity. Moreover, single-cell RNA sequencing of differentiated HSPCs identified osteoclast-related clusters in the CAC group, characterized by up-regulated gene expression in pathways associated with cellular response to stimuli, membrane trafficking, and vesicle-mediated transport. Collectively, these data demonstrate that CAC enhances the capacity of HSPCs to differentiate into osteoclast precursors. They provide critical insights into the mechanisms by which alcohol consumption contributes to reduced bone density and skeletal fragility.