GDF15 modulates aging-associated adaptions in the mechanoresponse of periodontal ligament fibroblasts.

Abstract

Purpose: This in vitro study aimed to examine aging-associated adaptations in the mechanoresponse of periodontal ligament fibroblasts (PdLFs) and explore a potential regulatory role of growth differentiation factor 15 (GDF15).

Methods: Replicative senescence was induced in cultured human PdLFs (hPdLFs) by repeated enzymatic subcultivation as a valid in vitro aging model. The senescent phenotype was assessed by analyzing cellular morphology, proliferative capacity, and senescence marker expression. Furthermore, GDF15 levels were measured and subsequently modulated by small interfering RNA(siRNA)-mediated knockdown and by ponsegromab, a novel GDF15-neutralizing antibody. Tensile and compressive forces were applied using BioFlex® Culture Plates (FLEXCELL®, Dunn Labortechnik, Asbach, Germany) and sterile glass plates, respectively. The mechanoresponses of hPdLFs were characterized by analyzing pro-inflammatory cytokine levels and the activation of immune cells as well as of bone-remodeling osteoblasts and osteoclasts.

Results: Aged hPdLFs exhibited decreased proliferation, increased β‑galactosidase activity, and morphological changes indicative of cellular senescence. Elevated baseline and force-induced intra- and extracellular GDF15 levels were observed in aged hPdLFs correlating with enhanced pro-inflammatory cytokine expression and immune cell activation. While aged hPdLFs showed reduced activation of osteoblasts in response to tensile forces, compressive forces led to increased osteoclast activation. Remarkably, modulating intra- and extracellular GDF15 levels partially restored the deregulated activation of bone-remodeling cells.

Conclusion: Aging altered the mechanobiological response of PdL fibroblasts by promoting a hyperinflammatory microenvironment and shifting bone remodeling towards degenerative processes. Senescence-associated increases in GDF15 contributed to these changes by force-dependent intra- and extracellular signaling pathways. Targeting GDF15 could offer a therapeutic potential to optimize bone remodeling and improve orthodontic care for the elderly.