Comparison of Primary Human Osteoblast-like Cells and hFOB 1.19 Cells: Contrasting Effects of Proinflammatory Cytokines.

Proinflammatory cytokines such as IL-1β, IL-6, and TNF-α are key mediators of inflammatory bone loss and are commonly described as inhibitors of osteoblast function. However, their effects on osteogenesis remain controversial, likely due to the differences in the cell models and experimental settings in in vitro studies. We recently showed that these cytokines significantly enhanced the mineralization of primary human osteoblast-like cells (OBs). Here, we provide the first analysis of cytokine effects on the osteogenesis of the widely used human osteoblastic cell line hFOB 1.19 and compare them to primary OBs. Unexpectedly, all three cytokines significantly inhibited mineralization in hFOB 1.19 cells without affecting the proliferation. IL-1β and TNF-α also suppressed ALP activity, whereas IL-6 acted ALP-independent but increased the osteogenic marker expression despite the reduced mineralization, indicating a possible uncoupled differentiation and mineralization. Morphological and transcriptional analyses indicated that hFOB 1.19 cells represent an earlier osteogenic differentiation stage, while primary OBs show phenotypic heterogeneity and donor-dependent expression profiles. These data demonstrate that proinflammatory cytokines can have severely different effects on the osteogenesis of different cell models, supported by the highly contradictory findings reported in the literature. Nevertheless, elucidating the mechanisms underlying the inhibition of osteogenesis in hFOB 1.19 cells may provide important insights into the cell model and differentiation-stage-specific cytokine effects.