Osteoblast secretome mediates periodontal ligament stem cells differentiation in response to orthodontic compressive forces: an in vitro study
Damien Brézulier, Solen Novello, Kim Boi Le Hyuen, Agnès Novella, Sylvie Tricot, Sylvie JeanneAbstract
Background/Objectives
Orthodontic tooth movement (OTM) relies on mechanobiological interactions between osteoblasts and human periodontal ligament stem cells (hPDLSCs). While mechanical compression alters osteoblast behavior—upregulating RANKL/OPG and inflammatory mediators—its paracrine effects on hPDLSCs remain poorly understood. This study investigated how osteoblast-derived secretomes, conditioned by compressive forces, modulate hPDLSC differentiation.
Materials/Methods
hPDLSCs were isolated from third molars and characterized via immunophenotyping (CD105, CD73, CD90), clonogenicity assays, and multipotent differentiation (osteogenic/adipogenic). Osteoblastic spheroids (hFOB 1.19) were subjected to 0, 1, or 4 g/cm2 compression for 24/72 hours, generating conditioned media. hPDLSCs were exposed to these media for 48 hours, and viability, gene expression (RT-qPCR), and mineralization (Alizarin Red) were assessed.
Results
Compressive stress attenuated osteoblast secretome-induced osteogenic marker expression in hPDLSCs (RunX2, ALP, Col1, OPN), with no effect on osteocalcin. Sox9 (chondrogenic) was downregulated, while adipogenic markers (PPARγ, Adipsin) remained unchanged. No mineralization occurred under any condition. Viability assays confirmed no adverse effects on proliferation.
Limitations
The in vitro monoculture model used here does not fully recapitulate the spatial and temporal complexity of cell-cell interactions in vivo, including bidirectional signaling and the influence of the extracellular matrix.
Conclusions/Implications
These findings suggest that mechanical compression disrupts osteoblast-secretome-mediated osteogenic priming of hPDLSCs, potentially explaining resorption-site dynamics during OTM. Future studies should isolate extracellular vesicles (EVs) from stressed osteoblasts to identify cargo (e.g. miRNAs) driving MSC fate. Understanding this paracrine axis may optimize orthodontic treatments and regenerative therapies.