CTHRC1 Knockdown Promotes Inflammatory Responses Partially by p38 MAPK Activation in Human Periodontal Ligament Cells

Collagen triple helix repeat containing 1 (CTHRC1), a secreted glycoprotein, is widely expressed in many tissues. It has been recently defined as a novel marker for rheumatoid arthritis (RA), a systemic inflammatory disorder. However, the precise role of CTHRC1 in other chronic inflammatory diseases, like periodontal disease, remains unclear. This research aimed to explore the presence of CTHRC1 in periodontal inflammation, determine the precise role in inflammatory response modulation in periodontal ligament cells (PDLCs), and explore its underlying mechanisms. In vivo gingival crevicular fluid (GCF) and gingivae were obtained from healthy people and chronic periodontitis patients. Maxillary tissues of mice with or without ligature-induced periodontitis were immunostained for CTHRC1. In vitro human PDLCs were treated with tumor necrosis factor alpha (TNF-α) to mimic the inflammatory environment. Small interfering RNA (siRNA) was used to silence CTHRC1. SB203580 was used to inhibit the p38 mitogen-activated protein kinase (MAPK) pathway. CTHRC1 was highly expressed in GCF and gingival tissues of periodontitis patients. Animal models also revealed the same tendency. CTHRC1 knockdown promoted inflammatory cytokine production and activated the p38 MAPK signaling pathway in PDLCs. Inhibiting the p38 MAPK signaling pathway partially attenuated the inflammatory responses. This study revealed that CTHRC1 was highly expressed in periodontitis and suggested that CTHRC1 might play an important role in modulating periodontal inflammation.