Rapamycin-Induced Autophagy Promotes the Chondrogenic Differentiation of Synovium-Derived Mesenchymal Stem Cells in the Temporomandibular Joint in Response to IL-1β.

Wenjing Liu,Guodong Chen,Wenting Liao,Longquan Shao,Yiyuan Kang,Haiyun Luo,Yangpeng Sun,Ruolan Wang,Yu Sheng Li

doi:10.1155/2020/4035306

Abstract

Cartilage defects in temporomandibular disorders (TMD) lead to chronic pain and seldom heal. Synovium-derived mesenchymal stem cells (SMSCs) exhibit superior chondrogenesis and have become promising seed cells for cartilage tissue engineering. However, local inflammatory conditions that affect the repair of articular cartilage by SMSCs present a challenge, and the specific mechanism through which the function remains unclear. Thus, it is important to explore the chondrogenesis of SMSCs under inflammatory conditions of TMD such that they can be used more effectively in clinical treatment. In this study, we obtained SMSCs from TMD patients with severe cartilage injuries. In response to stimulation with IL-1β, which is well known as one of the most prevalent cytokines in TMD, MMP13 expression increased, while that of SOX9, aggrecan, and collagen II decreased during chondrogenic differentiation. At the same time, IL-1β upregulated the expression of mTOR and decreased the ratio of LC3-II/LC3-I and the formation of autophagosomes. Further study revealed that rapamycin pretreatment promoted the migration of SMSCs and the expression of chondrogenesis-related markers in the presence of IL-1β by inducing autophagy. 3-Benzyl-5-((2-nitrophenoxy)methyl)-dihydrofuran-2(3H)-one (3BDO), a new activator of mTOR, inhibited autophagy and increased the expression of p-GSK3βser9 and β-catenin, simulating the effect of IL-1β stimulation. Furthermore, rapamycin reduced the expression of mTOR, whereas the promotion of LC3-II/LC3-I was blocked by the GSK3β inhibitor TWS119. Taken together, these results indicate that rapamycin enhances the chondrogenesis of SMSCs by inducing autophagy, and GSK3β may be an important regulator in the process of rapamycin-induced autophagy. Thus, inducing autophagy may be a useful approach in the chondrogenic differentiation of SMSCs in the inflammatory microenvironment and may represent a novel TMD treatment.

Highlights

Temporomandibular disorder (TMD) is a common disease in the maxillofacial region
To study the effect of Glycogen synthase kinase 3β (GSK3β) inhibition in autophagy in chondrogenesis, we examined the changes of GSK3β, β-catenin, and light chain 3 (LC3) expression in inflammatory synovium-derived mesenchymal stem cells (MSCs) (SMSCs) by western blot assays
The activation of GSK3β participates in the ubiquitination of β-catenin and the degradation of the proteasome. β-catenin, a key protein of Wnt signaling, affects the differentiation and maturation of chondrocytes and promotes the degradation of the cartilage matrix [34]. Consistent with these findings, our results demonstrated that the activity of GSK3β was inhibited and the β-catenin expression was increased in SMSCs in response to IL-1β, having an unfavourable effect on chondrogenesis

Summary

Introduction

Temporomandibular disorder (TMD) is a common disease in the maxillofacial region. Damaged cartilage in TMD leads to severe pain and mandibular movement disorders. The primary TMD treatments, including occlusal plates, drugs, physical or psychological treatments, joint irrigation, or surgical intervention, can alleviate symptoms but cannot repair damaged cartilage. With the development of regenerative medicine, stem cell-based tissue engineering technology provides a new opportunity for cartilage reconstruction. Mesenchymal stem cells (MSCs) from different sources exhibit different characteristics. In vitro assays have shown that synovium-derived MSCs (SMSCs) exhibit stronger proliferation abilities, slower cell senescence, and better chondrogenic abilities than MSCs from other sources in vitro, such as bone marrow MSCs and adipose MSCs [1]

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Conclusion