From 5F hematopoietic progenitors to osteoclasts: a scalable human model of osteoclastogenesis

Human osteoclast models are essential for studying bone physiology and skeletal disease, yet existing systems are constrained by donor variability and the limited expansion capacity of hematopoietic progenitors.

Conditionally expandable 5F hematopoietic stem and progenitor cells generated by transcription factor reprogramming with HOXA9, ERG, RORA, SOX4, and MYB were differentiated into osteoclasts. Cells were driven through an intermediate monocyte stage using IL three and M CSF, followed by RANKL stimulation to induce osteoclastogenesis.

Differentiated cells formed large, multinucleated, TRAP positive osteoclasts displaying F actin ring structures, cathepsin K expression, and strong bone resorptive activity. Gene expression analysis demonstrated marked upregulation of key osteoclast markers including NFATC1, MMP9, CTSK, and CA2.

By enabling conditional self-renewal at a downstream hematopoietic stage, the 5F platform overcomes key limitations of donor dependent and iPSC derived osteoclast models. This scalable and cytokine driven system provides a reproducible and standardized human osteoclast model suitable for studies of osteoclast biology, bone remodeling, and biomaterial interactions.