LncRNA-H19 Modulates Wnt/β-catenin Signaling by Targeting Dkk4 in Hindlimb Unloaded Rat

OBJECTIVE

To investigate the biological functions of long noncoding RNA-H19 (H19) in the pathogenesis of disuse osteoporosis (DOP).

METHODS

Fifty-four male Sprague Dawley (SD) rats were randomly divided into three groups: baseline control (BC, 6), age-matched control (AC, 24), and hindlimb unloading (HLU, 24). The rats in the BC group were sacrificed at the beginning of the experiment, while the AC and HLU rats were sacrificed at different times (7, 14, 21 and 28 days after HLU). The DOP model was verified by micro-CT scan, and quantitative real-time polymerase chain reaction (qRT-PCR) was used to quantify the expression of osteogenic genes (OPG, RunX2 and OPG). Gene sequencing and bioinformatic analysis were performed to find H19 target genes and the associated signaling pathway, which were first verified on tissue samples. Further verification was performed by knocking down the H19 and related gene in rat osteoblast cell line (UMR106 cell). Then, the changes of associated signaling pathway and osteogenic function were examined to confirm the prediction of the bioinformatic analysis.

RESULTS

Micro-CT scans and quantitative real-time polymerase chain reaction (qRT-PCR) tests showed progressively deteriorated trabecular bone and decreased level of osteogenic genes in the metaphysis of distal femur during HLU, indicating the successful establishment of a DOP model. According to RNA sequencing, 1351 mRNA and 464 lncRNA were abnormally expressed in response to mechanical unloading, in which the H19 decreased 2.86 fold in HLU rats. There were 1426 mRNA predicted to be the target genes of H19, and KEGG pathway analysis suggested that Wnt signaling pathway (Wnt signaling) was the top pathway responsible for these target genes. In the Wnt-associated genes targeted by H19, 11 were differentially expressed between HLU and AC rats, among which Dkk4 increased 2.44 fold in HLU rats when compared to normal controls. These results of sequencing and bioinformatic analysis were confirmed by the low expression of H19, overexpression of Dkk4 and inhibited Wnt signaling observed in DOP rats. Subsequent in vitro cell assay further demonstrated that knockdown of H19 led to upregulation of Dkk4, and inhibition of Wnt signaling and osteogenic function in UMR106 cell. These effects can be greatly reversed after application of knocking down Dkk4.

CONCLUSION

Our findings demonstrated that low expression of H19, induced by mechanical unloading, leads to development of DOP through inhibition of Wnt signaling by promoting Dkk4 expression.

The Long Noncoding RNA-H19 Mediates the Progression of Fibrosis from Acute Kidney Injury to Chronic Kidney Disease by Regulating the miR-196a/Wnt/β-Catenin Signaling

INTRODUCTION

Long noncoding RNAs (lncRNAs) have been reported to be involved in the occurrence and development of various diseases. This study was to investigate the role of lncRNA-H19 in the transition from acute kidney injury (AKI) to chronic kidney disease (CKD) and its underlying mechanism.

METHODS

Bilateral renal pedicle ischemia-reperfusion injury (IRI) was used to establish the IRI-AKI model in C57BL/6 mice. The expression levels of lncRNA-H19, miR-196a-5p, α-SMA, collagen I, Wnt1, and β-catenin in mouse kidney tissues and fibroblasts were determined by quantitative real-time PCR and Western blotting. The degree of renal fibrosis was evaluated by hematoxylin and eosin staining. The interaction between lncRNA-H19 and miR-196a-5p was verified by bioinformatics analysis and luciferase reporter assay. Immunohistochemistry and immunofluorescence were used to evaluate the expression of α-SMA and collagen I in kidney tissues and fibroblasts of mice.

RESULTS

lncRNA-H19 is upregulated, and miR-196a-5p is downregulated in kidney tissues of IRI mice. Moreover, miR-196a-5p is a direct target of lncRNA-H19. lncRNA-H19 overexpression promotes kidney fibrosis and activates fibroblasts during AKI-CKD development, while miR-196a-5p overexpression reversed these effects in vitro. Furthermore, lncRNA-H19 overexpression significantly upregulates Wnt1 and β-catenin expression in kidney tissues and fibroblasts of IRI mice, while miR-196a-5p overexpression downregulates Wnt1 and β-catenin expression in kidney tissues and fibroblasts of IRI mice.

CONCLUSION

lncRNA-H19 induces kidney fibrosis during AKI-CKD by regulating the miR-196a-5p/Wnt/β-catenin signaling pathway.