Osteogenic Differentiation of Renal Interstitial Fibroblasts Promoted by lncRNA MALAT1 May Partially Contribute to Randall's Plaque Formation.

Zewu Zhu,Huimin Zeng,Yongchao Li,Cheng He,Jinbo Chen,Hequn Chen,Fang Huang,Yu Cui,Feng Zeng,Yang Li,Weiping Xia,Zhiyong Chen,Meng Gao

doi:10.3389/fcell.2020.596363

Abstract

BackgroundThe current belief is that Randall’s plaques (RP) constitute a nidus for the formation of idiopathic calcium oxalate stones, but the upstream events in RP formation remain unclear. The present study aimed to investigate whether RP formation shares similarities with biomineralization and to illustrate the potential role played by the lncRNA MALAT1 in osteogenic differentiation of human renal interstitial fibroblasts (hRIFs).Materials and MethodsBiomineralization and MALAT1 expression were assessed in RP, and hRIFs were isolated and induced under osteogenic conditions for further experiments. The transcription initiation and termination sites in MALAT1 were identified by 5′ and 3′ RACE. RNA immunoprecipitation assays and luciferase assays were used to validate the interactions among MALAT1, Runx2 and miRNAs.ResultsUpregulated expression of osteogenic markers and MALAT1 was observed in RP and hRIFs induced with osteogenic medium. Biomineralization in RP and calcium phosphate (CaP) deposits in induced hRIFs were further verified by electron microscopy. Furthermore, overexpression of MALAT1 promoted the osteogenic phenotype of hRIFs, while treatment with a miR-320a-5p mimic and knockdown of Runx2 significantly suppressed the osteogenic phenotype. Further analysis showed that MALAT1 functioned as a competing endogenous RNA to sponge miR-320a-5p, leading to upregulation of Runx2 and thus promoting osteogenic differentiation of hRIFs.ConclusionEctopic calcification and MALAT1 partially contributed to the formation of RP, in which MALAT1 might promote Runx2 expression to regulate osteogenic differentiation of hRIFs by sponging miRNA-320a-5p. The current study sheds new light on the lncRNA-directed mechanism of RP formation via a process driven by osteogenic-like cells.

Highlights

Nephrolithiasis remains a global public health problem with increasing prevalence (Khan et al, 2016); calcium oxalate (CaOx) is the most common chemical component in renal calculi and is mostly idiopathic in nature (Canales and Hatch, 2014)
To further elucidate the molecular mechanisms of interstitial biomineralization in renal papillae, we focused on the osteogenic phenotype of human renal interstitial fibroblasts, since renal interstitial fibroblasts (RIFs) play an important role in the pathophysiology of renal interstitial diseases (Sharpe and Dockrell, 2012), and many fibroblasts have been proven to have the potential for osteoblast differentiation seen elsewhere, such as periodontal ligament fibroblasts and bronchial fibroblasts (Sabatini et al, 2005)
The results consistently showed significantly increased expression of osteogenic markers in Randall’s plaques (RP) compared to normal renal papillae (NRP) (Figures 1B–E,G and Supplementary Figures 1d–f)

Summary

Introduction

Nephrolithiasis remains a global public health problem with increasing prevalence (Khan et al, 2016); calcium oxalate (CaOx) is the most common chemical component in renal calculi and is mostly idiopathic in nature (Canales and Hatch, 2014). The progression of CaP deposition in the renal interstitium to RP formation was found to be similar to pathological biomineralization (Evan et al, 2015b; Hsi et al, 2017), and previous studies advanced the hypothesis that the formation of RP involves a process driven by osteogenic-like cells (Gambaro et al, 2004; Khan and Canales, 2015). The present study aimed to investigate whether RP formation shares similarities with biomineralization and to illustrate the potential role played by the lncRNA MALAT1 in osteogenic differentiation of human renal interstitial fibroblasts (hRIFs)

Methods

Results

Conclusion