Thymosin Beta-4 Suppresses Osteoclastic Differentiation and Inflammatory Responses in Human Periodontal Ligament Cells

Background Recent reports suggest that thymosin beta-4 (T beta 4) is a key regulator for wound healing and anti-inflammation. However, the role of T beta 4 in osteoclast differentiation remains unclear. Purpose The purpose of this study was to evaluate T beta 4 expression in H2O2-stimulated human periodontal ligament cells (PDLCs), the effects of T beta 4 activation on inflammatory response in PDLCs and osteoclastic differentiation in mouse bone marrow-derived macrophages (BMMs), and identify the underlying mechanism. Methods Reverse transcription-polymerase chain reactions and Western blot analyses were used to measure mRNA and protein levels, respectively. Osteoclastic differentiation was assessed in mouse bone marrow-derived macrophages (BMMs) using conditioned medium (CM) from H2O2-treated PDLCs. Results T beta 4 was down-regulated in H2O2-exposed PDLCs in dose-and time-dependent manners. T beta 4 activation with a T beta 4 peptide attenuated the H2O2-induced production of NO and PGE(2) and up-regulated iNOS, COX-2, and osteoclastogenic cytokines (TNF-alpha, IL-1 beta, IL-6, IL-8, and IL-17) as well as reversed the effect on RANKL and OPG in PDLCs. T beta 4 peptide inhibited the effects of H2O2 on the activation of ERK and JNK MAPK, and NF-kappa B in PDLCs. Furthermore, T beta 4 peptide inhibited osteoclast differentiation, osteoclast-specific gene expression, and p38, ERK, and JNK phosphorylation and NF-kappa B activation in RANKL-stimulated BMMs. In addition, H2O2 up-regulated Wnt5a and its cell surface receptors, Frizzled and Ror2 in PDLCs. Wnt5a inhibition by Wnt5a siRNA enhanced the effects of T beta 4 on H2O2-mediated induction of pro-inflammatory cytokines and osteoclastogenic cytokines as well as helping osteoclastic differentiation whereas Wnt5a activation by Wnt5a peptide reversed it. Conclusion In conclusion, this study demonstrated, for the first time, that T beta 4 was down-regulated in ROS-stimulated PDLCs as well as T beta 4 activation exhibited anti-inflammatory effects and anti-osteoclastogenesis in vitro. Thus, T beta 4 activation might be a therapeutic target for inflammatory osteolytic disease, such as periodontitis.