Circular RNA CircCOL5A1 Sponges the MiR-7-5p/Epac1 Axis to Promote the Progression of Keloids Through Regulating PI3K/Akt Signaling Pathway.

Wenchang Lv,Shengxuan Liu,Yiping Wu,Qi Zhang,Weijie Hu,Yuping Ren

doi:10.3389/fcell.2021.626027

Abstract

Keloids, as a result of abnormal wound healing in susceptible individuals, are characterized by the hyper-proliferation of fibroblasts and exaggerated deposition of extracellular matrix. Current surgical and therapeutic modalities provide limited satisfactory results. Growing evidence has highlighted the roles of circRNAs in acting as miRNA sponges. However, up to date, the regulatory mechanism of circRNAs in the pathological process of keloids has rarely been reported. In this study, cell proliferation, cell migration, flow cytometry, western blotting, fluorescence in situ hybridization, dual-luciferase activity, and immunohistochemistry assays were applied to explore the roles and mechanisms of the circCOL5A1/miR-7-5p/Epac1 axis in the keloid. The therapeutic potential of circCOL5A1 was investigated by establishing keloid implantation models. The RT-qPCR result revealed that circCOL5A1 expression was obviously higher in keloid tissues and keloid fibroblasts. Subsequent cellular experiments demonstrated that circCOL5A1 knockdown repressed the proliferation, migration, extracellular matrix (ECM) deposition, whereas promoted cell apoptosis, through the PI3K/Akt signaling pathway. Furthermore, RNA-fluorescence in situ hybridization (RNA-FISH) illustrated that both circCOL5A1 and miR-7-5p were located in the cytoplasm. The luciferase reporter gene assay confirmed that exact binding sites were present between circCOL5A1 and miR-7-5p, as well as between miR-7-5p and Epac1. Collectively, the present study revealed that circCOL5A1 functioned as competing endogenous RNA (ceRNA) by adsorbing miR-7-5p to release Epac1, which contributed to pathological hyperplasia of keloids through activating the PI3K/Akt signaling pathway. Our data indicated that circCOL5A1 might serve as a novel promising therapeutic target and represent a new avenue to understand underlying pathogenesis for keloids.

Highlights

Keloids are a benign skin fibroproliferative tumor that generally serves as a result of abnormal wound healing in susceptible individuals and are unique to humans (Limandjaja et al, 2020)
The results revealed that circCOL5A1 acted as a sponge of miR-7-5p to affect the expression of Epac1, and eventually modulated the human keloid fibroblasts (HKFs) functions including proliferation, migration, and apoptosis through PI3K/Akt signaling pathway
The results demonstrated that miR-7-5p inhibitor reversed the proliferation, migration, and apoptosis regulation effects induced by circCOL5A1 knockdown in HKFs through cell counting kit-8 (CCK-8) and EdU assay, wound healing and transwell assay, apoptosis analysis, and western blot analysis (Figures 5A–F)

Summary

Introduction

Keloids are a benign skin fibroproliferative tumor that generally serves as a result of abnormal wound healing in susceptible individuals and are unique to humans (Limandjaja et al, 2020). Keloids are characterized pathologically by the hyperproliferation of cells (e.g., fibroblasts) and excessive deposition of extracellular matrix (ECM) (e.g., type I and type III collagen) (Rippa et al, 2019). Keloid-derived fibroblasts, served as the main cellular components in keloid tissues, play a pivotal role in modulating the synthesis and re-modeling of ECM, indicating an association between the continuous aggressive growth and collagen production (Arjunan et al, 2020). In keloid patients, the systemic balance between fibroblast proliferation and apoptosis is distorted, resulting in the continuous hyperplasia of keloids. An in-depth understanding of the molecular mechanisms of aggressive progression of keloid and exploring novel efficient therapeutic strategies is an urgent need

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Conclusion