Dental pulp injuries caused by trauma or deep cavities often result in inflammation, tissue death, and loss of tooth vitality. Severe cases may involve bacterial invasion and prolonged immune responses, which further disrupt the pulp’s natural healing environment. While regenerative endodontic therapies aim to restore living tissue, achieving predictable biological repair has remained challenging. A key factor in successful regeneration is the precise control of stem cell signaling pathways that govern cell proliferation, differentiation, and matrix remodeling. Among these, Wnt/β-catenin signaling plays a central role. Yet, the upstream molecular mechanisms controlling this pathway in human dental pulp stem cells have remained largely unclear.
To investigate, researchers focused on SMAD7, a protein previously known as a negative regulator of transforming growth factor-beta (TGF-β) signaling. Using human dental pulp stem cells (hDPSCs), the team employed immunofluorescent staining, gene silencing, nuclear protein quantification, and western blot analysis to track intracellular signaling dynamics.
Their experiments revealed that SMAD7 directly interacts with β-catenin in the nucleus, forming a transcriptional complex that activates the Wnt pathway.
Mechanistically, phosphorylated SMAD2/3 (P-SMAD2/3), activated by TGF-β signaling, can bind and sequester β-catenin, reducing its nuclear availability and suppressing Wnt/β-catenin activity. SMAD7 counteracts this effect, preserving β-catenin activity and maintaining Wnt signaling. When SMAD7 is lost, P-SMAD2/3 accumulates, captures β-catenin, and weakens pathway output. These findings were published on January 6, 2026, in the International Journal of Oral Science.
The study was led by Dr. Tian Chen, a postdoctoral researcher in the Department of Orthodontics at West China Hospital of Stomatology, Sichuan University, Chengdu, China.
This research challenges the long-held belief that SMAD7 functions only as an inhibitory molecule. Instead, the study shows that SMAD7 acts as a direct transcriptional mediator of Wnt/β-catenin signaling. By forming a nuclear complex with β-catenin, SMAD7 promotes activation of genes involved in stem cell proliferation and regenerative differentiation. “We were surprised to see SMAD7 functioning as a positive regulator within the nucleus,” said Dr. Chen. “This direct partnership with β-catenin explains how Wnt signaling is amplified during dental pulp regeneration.”
Beyond elucidating a molecular mechanism, the study points to practical applications. Targeting the SMAD7–β-catenin interaction could enhance regenerative endodontic procedures by promoting natural pulp healing. Biomaterials or small molecules that optimize this signaling pathway may help preserve tooth vitality and reduce dependence on conventional root canal treatments, improving patient outcomes through biological repair rather than artificial replacement.
The implications extend beyond dentistry. Wnt/β-catenin signaling is essential in bone biology, craniofacial development, and tissue engineering. Recognizing SMAD7 as a direct transcriptional partner of β-catenin opens new possibilities for regenerative medicine and stem cell–based therapies. Over the coming decade, refined control of this pathway may enable precision strategies to guide tissue repair in both oral and skeletal systems.