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. 2021 Jun;47(6):119.
doi: 10.3892/ijmm.2021.4952. Epub 2021 May 6.

MicroRNA‑101 inhibits renal tubular epithelial‑to‑mesenchymal transition by targeting TGF‑β1 type I receptor

Affiliations

MicroRNA‑101 inhibits renal tubular epithelial‑to‑mesenchymal transition by targeting TGF‑β1 type I receptor

Qinglan Wang et al. Int J Mol Med. 2021 Jun.

Abstract

MicroRNAs (miRNAs/miRs) are key regulators of renal interstitial fibrosis (RIF). The present study was designed to identify miRNAs associated with the development of RIF, and to explore the ability of these identified miRNAs to modulate the renal tubular epithelial‑to‑mesenchymal transition (EMT) process. To this end, miRNAs that were differentially expressed between normal and fibrotic kidneys in a rat model of mercury chloride (HgCl2)‑induced RIF were detected via an array‑based approach. Bioinformatics analyses revealed that miR‑101 was the miRNA that was most significantly downregulated in the fibrotic renal tissue samples, and this was confirmed by RT‑qPCR, which also demonstrated that this miRNA was downregulated in transforming growth factor (TGF)‑β1‑treated human proximal tubular epithelial (HK‑2) cells. When miR‑101 was overexpressed, this was sufficient to reverse TGF‑β1‑induced EMT in HK‑2 cells, leading to the upregulation of the epithelial marker, E‑cadherin, and the downregulation of the mesenchymal marker, α‑smooth muscle actin. By contrast, the downregulation of miR‑101 using an inhibitor exerted the opposite effect. The overexpression of miR‑101 also suppressed the expression of the miR‑101 target gene, TGF‑β1 type I receptor (TβR‑I), and thereby impaired TGF‑β1/Smad3 signaling, while the opposite was observed upon miR‑101 inhibition. To further confirm the ability of miR‑101 to modulate EMT, the HK‑2 cells were treated with the TβR‑I inhibitor, SB‑431542, which significantly suppressed TGF‑β1‑induced EMT in these cells. Notably, miR‑101 inhibition exerted a less pronounced effect upon EMT‑related phenotypes in these TβR‑I inhibitor‑treated HK‑2 cells, supporting a model wherein miR‑101 inhibits TGF‑β1‑induced EMT by suppressing TβR‑I expression. On the whole, the present study demonstrates that miR‑101 is capable of inhibiting TGF‑β1‑induced tubular EMT by targeting TβR‑I, suggesting that it may be an important regulator of RIF.

Keywords: TGF‑β1 type I receptor; microRNA‑101; renal interstitial fibrosis; tubular epithelial‑to‑mesenchymal transition.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
HgCl2 induces renal inflammation and interstitial fibrosis in rats. (A) Representative H&E-stained renal tissues. (B) Representative Masson's trichrome-stained tissues used to analyze RIF. (C) Quantification of Masson's trichrome positive staining area in renal tissue samples. (D) Renal hydroxyproline levels were measured using the method by Jamall et al (23). (E) Renal α-SMA levels were assessed via western blot analysis. (F) α-SMA levels in western blots were quantified via densitometry and were normalized to GAPDH. (G) Renal α-SMA mRNA expression was assessed by RT-qPCR. HgCl2, mercury chloride; RIF, renal interstitial fibrosis; α-SMA, α-smooth muscle actin; Hyp, hydroxyproline.
Figure 2
Figure 2
Identification of key differentially expressed miRNAs associated with HgCl2-induced renal interstitial fibrosis. (A) Data from a miRNA microarray comparing expression levels between control and RIF model rats were arranged in a heatmap. The color scale indicates the expression level of the miRNA, with green and red colors indicating low and high expression, respectively. (B) A miRNA-gene network was constructed, with squares and circles corresponding to miRNAs and genes, respectively. Associations between these network elements are represented by edges, with network centrality corresponding to degree values. (C) The degree values for the 10 top miRNAs within this network, with miR-101 being identified as the most significant downregulated miRNA in this disease context. The red square represents miRNA and the green circle represents mRNA. HgCl2, mercury chloride.
Figure 3
Figure 3
miR-101 downregulation is evident in both the RIF model renal tissue and TGF-β1 treated HK-2 cells. (A) RT-qPCR was used to assess miR-101 expression in renal tissues. (B) RT-qPCR was used to assess miR-101 expression in TGF-β1-treated HK-2 cells. (C) RT-qPCR was used to assess E-cadherin and α-SMA expression in TGF-β1-treated HK-2 cells. (D) Western blot analysis was used to assess E-cadherin and α-SMA protein. (E) Densitometric quantification of the results in (D), with GAPDH used for normalization. RIF, renal interstitial fibrosis; α-SMA, α-smooth muscle actin; TGF-β1, transforming growth factor-β1.
Figure 4
Figure 4
miR-101 inhibits TGF-β1-induced EMT in HK-2 cells. (A) miR-101 expression was quantified in HK-2 cells. (B) Levels of E-cadherin and α-SMA in HK-2 cells were measured by western blot analysis. (C) Densitometric quantification of data in (B), with GAPDH used for normalization. (D) E-cadherin and α-SMA expression as assessed by immunofluorescence. (E) E-cadherin and α-SMA staining intensity was quantified using the Thermo HCS StudioTM 2.0 Cell Analysis Program. (F) RT-qPCR was used to assess E-cadherin and α-SMA mRNA expression. NC, negative control; T, TGF-β1; mimic, miR-101 mimic; EMT, epithelial-to-mesenchymal transition; α-SMA, α-smooth muscle actin; TGF-β1, transforming growth factor-β1.
Figure 5
Figure 5
miR-101 inhibition enhances TGF-β1-induced EMT in HK-2 cells. A miR-101 inhibitor was transfected into HK-2 cells, which were then treated with TGF-β1, (A) and miR-101 expression was quantified. (B) E-cadherin and α-SMA expression as assessed by immunofluorescence. (C) E-cadherin and α-SMA staining intensity as quantified using the Thermo HCS StudioTM 2.0 Cell Analysis Program. (D) RT-qPCR was used to assess E-cadherin and α-SMA mRNA expression. (E) E-cadherin, and α-SMA levels in HK-2 cells were assessed by western blot analysis. (F) Densitometric quantification of the data in (D), with GAPDH used for normalization; NC, negative control; T, TGF-β1; inhibitor, miR-101 inhibitor; α-SMA, α-smooth muscle actin; TGF-β1, transforming growth factor-β1.
Figure 6
Figure 6
Effect of miR-101 on TβR-I and Smad3 in HK-2 cells. (A) TβR-I, Smad3 and p-Smad3 levels were assessed by western blot analysis in HK-2 cells following miR-101 mimic transfection. (B) Densitometric quantification of TβR-I and Smad3, with GAPDH being used for normalization. (C) Ratio of p-Smad3 vs. Smad3. (D) TβR-I, Smad3 and p-Smad3 levels were assessed by western blot analysis in HK-2 cells following miR-101 inhibitor transfection. (E) Densitometric quantification of TβR-I and Smad3, with GAPDH being used for normalization. (F) Ratio of p-Smad3 vs. Smad3. NC, negative control; T, TGF-β1; mimic, miR-101 mimic; inhibitor, miR-101 inhibitor; α-SMA, α-smooth muscle actin; TGF-β1, transforming growth factor-β1.
Figure 7
Figure 7
Effect of miR-101 inhibition on TβR-I inhibitor-treated HK-2 cells. (A) E-cadherin and α-SMA expression were assessed by immunofluorescence staining. (B) data in (A) were quantified using the Thermo HCS StudioTM 2.0 Cell Analysis Program. (C) TβR-I expression in HK-2 cells was assessed by western blot analysis. (D) Densitometric quantification of the data in (C), with GAPDH used for normalization. NC, negative control; T, TGF-β1; inhibitor, miR-101 inhibitor; α-SMA, α-smooth muscle actin; TGF-β1, transforming growth factor-β1.

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Grants and funding

The present study was supported by the National Natural Science Foundation of China (grant nos. 81573810 and 30901943), the China Postdoctoral Science Foundation (grant no. 2015T80445) and the National Science and Technology Major Project 'Key New Drug Creation and Manufacturing Program' of China (grant no. 2019ZX09201001).