Dental pulp stem cell-derived intracellular vesicles prevent orthodontic relapse by inhibiting PI3K/Akt/NF-κB-mediated osteoclast activity

Abstract

Background Orthodontic relapse, the undesired deviation of teeth from their corrected positions, remains a significant challenge in clinical orthodontics. Incomplete periodontal bone remodeling has been identified as a key factor in this process. Despite decades of research, currently there are no effective strategies to prevent relapse. Methods We isolated and identified dental pulp stem cell-derived intracellular vesicles (DPSC-IV) from human dental pulp tissue. To investigate its effect, DPSC-IV was added to osteoblast or osteoclast differentiation medium. During the orthodontic retention period, DPSC-IV was administrated to rats by subgingival injection. Relapse distance and relapse rate were calculated to evaluate DPSC-IV's ability to prevent relapse. Additionally, Western blot analysis were used to examine DPSC-IV's inhibitory effect on osteoclast differentiation. Results DPSC-IV significantly promoted osteoblast differentiation and inhibited osteoclast differentiation. Application of DPSC-IV during retention resulted in a significant reduction in both relapse distance and relapse rate, with improved periodontal structure and decreased osteoclast activity. This effect was mediated by the PI3K/Akt/NF-κB signaling pathway and could be reversed by the PI3K activator insulin-like growth factor-1 (IGF-1). Conclusion This study highlights the potential of DPSC-IV as a novel preventive approach against orthodontic relapse, offering a novel strategy for maintaining long-term orthodontic stability.

1. Introduction

Successful orthodontic treatment aims to maintain long-term dental health and aesthetics. However, upon the completion of active orthodontic treatment, teeth tend to deviate from their new locations, moving back towards their pre-treatment locations, which is termed as orthodontic relapse [1]. Orthodontic relapse occurs in over 70% of cases, yet no effective prevention methods are currently available [2, 3]. Recent research suggests that ongoing periodontal bone remodeling and active osteoclast activity contribute to relapse [4].

Osteoclasts are multinucleated cells responsible for bone resorption and play a crucial role in periodontal bone remodeling [5]. Receptor activator of nuclear factor-κB ligand (RANKL) is a key cytokine that regulates osteoclast differentiation and activation. The binding of RANKL to receptor activator of nuclear factor-κB (RANK) on osteoclast precursor cells initiates intracellular signaling cascades, including phosphatidylinositol 3 kinase (PI3K)/Akt, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and mitogen-activated protein kinase (MAPK) [6, 7]. These cascades ultimately trigger the expression of nuclear factor of activated T-cells (NFATc1), which promotes osteoclast differentiation by up-regulating the expression of osteoclast-specific markers, such as cathepsin K (CTSK) and tartrate-resistant acid phosphatase (TRAP) [7]. Recent studies have highlighted the essential role of PI3K/Akt as an upstream signal in NF-κB activation during osteoclast differentiation [8, 9]. Thus, we speculated that the PI3K/Akt/NF-κB signaling pathway is involved in osteoclast activity during orthodontic relapse.

Over the decades, researchers have sought methods to prevent relapse. Multiple drugs have demonstrated efficacy in reducing relapse through regulating bone remodeling [10–12]. However, due to the uncertainty of drug action and side effects, finding a safe and effective medication has become the current research trend. Regenerative medicine utilizing mesenchymal stem cells (MSCs) or their exosomes has demonstrated significant potential for wound healing and bone regeneration. These nanovesicles, once taken up by recipient cells, release carried signaling molecules to orchestrate intercellular communication and fine-tune physiological and pathological processes such as cell proliferation, differentiation, and inflammation [13]. Being the most widely studied, exosomes derived from bone marrow have shown promise in various therapeutic applications.