1. Introduction
Glaucoma is a progressive optic neuropathy with loss of retinal ganglion cells and characteristic visual field and optic nerve changes [
1]. Glaucoma affects over 60 million people worldwide and the prevalence is projected to increase to over 118 million people by 2040 [
2]. Primary open-angle glaucoma (POAG) forms the most prevalent subtype of glaucoma and has a complex, multifactorial aetiology. Raised intraocular pressure (IOP) is the most important clinically modifiable risk factor for POAG. IOP is generated by the conventional aqueous humour outflow pathway via the trabecular meshwork and all current pharmacological agents target aqueous humour dynamics to lower IOP [
3,
4].
However, some patients with POAG show a limited therapeutic response or are refractory to these pharmacological agents (Scherer, 2002; Ang, 2004; Cai et al., 2021), while others have clinically significant adverse physiological impacts, such as bradycardia or bronchospasm [
8]. Until the development of Rho kinase (ROCK) inhibitors, none of the topical drug treatments for POAG targeted the underlying cellular pathophysiology in the trabecular meshwork [
9,
10]. ROCK inhibitors pharmacologically manipulate the cytoskeleton of trabecular meshwork and Schlemm’s canal cells reducing outflow resistance and lowering IOP [
9,
10]. Relatively common ocular side effects like conjunctival hyperaemia have limited tolerability of ROCK inhibitors in the pharmacological management of POAG [
3,
4,
10]. Therefore, there is a clinical need to develop novel therapies for POAG specifically targeting the molecular pathology in the trabecular meshwork to lower IOP [
3,
4,
11].
Elevated IOP in POAG results from cellular and molecular changes in the trabecular meshwork (TM) driven by increased levels of transforming growth factor β (TGFβ) in the anterior segment of the eye [
12]. TGF-β1 and -β2 result in pathogenic changes in the human trabecular meshwork (TM) cell population and phenotype, which contribute to increased IOP [
13]. Various studies have identified elevated TGFβ2 levels in the aqueous humour of POAG patients [
14,
15,
16,
17,
18], but the cause of these elevated levels is unclear. Elevated TGFβ2 levels have also been reported in the glaucomatous TM, indicating that increased levels of total and mature TGFβ may play an important role in the pathogenesis of POAG [
19]. TGFβ2 perfusion in an anterior eye segment organ culture model resulted in elevated intra-ocular pressure (IOP) and fibrillary material accumulation in the trabecular meshwork [
15,
20]. In pseudoexfoliation glaucoma (XFG), an aggressive form of secondary open-angle glaucoma, both the latent and active forms of TGFβ1 are increased in the aqueous humour and extracellular matrix (ECM) [
21,
22,
23].
The TGFβ receptor complex transmits signals via both canonical and non-canonical pathways [
24,
25,
26]. Canonical TGFβ signalling results in Smad2/3 - Smad4 complexes translocating to the nucleus where they function as transcription factors that can regulate gene expression including microRNAs (miRNAs) [
27,
28,
29,
30]. MiRNAs are small, single-stranded, noncoding RNAs which are important regulators of eukaryotic gene expression in health and disease [
31]. Normally, miRNAs bind to the 3′ untranslated region (UTR) of their target mRNAs resulting in mRNA degradation or translation repression [
32]. Most TGFβ signalling pathway components are known to be targeted by one or more miRNAs, and miRNA regulation of TGFβ signalling molecules influences the pathogenesis of fibrotic diseases [
33]. TGFβ signalling can also regulate miRNA expression at transcriptional and post-transcriptional levels [
25]. TGFβ is both cell and context-specific in terms of its functionality. Therefore, research must focus on building our understanding of how TGFβ affects both the structural and functional changes in the outflow pathway and therefore IOP to develop new glaucoma therapies that target the molecular pathology in the TM.
Identifying the expression profiles of miRNAs in POAG and XFG could help us to better understand the changes in gene expression in the TM as well as gain insight into potential pathways that may be involved in the pathogenesis of the disease. The ability of miRNA manipulations to alter gene expression has raised the possibility of miRNA-based therapeutics [
34,
35,
36,
37]. Using miRNA-Seq the miRNA expression profile in the normal human trabecular meshwork has been established [
38]. However, no previous studies have looked at miRNA expression changes in the TM following TGFβ treatment. Therefore, our study is the first miRNA-Seq study to evaluate the effects of TGFβ1 and -β2 treatment on miRNA expression in normal human primary TM cells. Evaluating TGFβ-responsive miRNA expression in the TM will further our understanding of the important pathways and changes involved in the pathogenesis of POAG and XFG and could lead to the development of miRNAs as new therapeutic modalities in glaucoma.
4. Discussion
Understanding the role of the TGFβ-induced microRNAome in the trabecular meshwork (TM) provides insight into the molecular pathology of primary open-angle glaucoma (POAG) and pseudo-exfoliation glaucoma (XFG). Determining the specific genes and pathways impacted by dysregulated miRNA expression will support the development of miRNA-based therapeutics for glaucoma [
68,
69,
70]. In this study, we have treated human primary TM cells with either TGFβ1 or TGFβ2, as cellular models of POAG (TGFβ2) and XFG (TGFβ1), and using small RNA sequencing, we identified 186 TGFβ1-regulated miRNAs in TM cells and 72 TGFβ2-regulated miRNAs suggesting TGFβ1 stimulation had a stronger effect on the miRNA expression profile in TM cells. Increased levels of TGFβ in the anterior segment of the eye induce fibrotic changes in the TM in glaucoma (POAG and XFG) including altered turnover of extracellular matrix (ECM) components, formation of cross-linked actin networks (CLANS), upregulation of alpha-smooth muscle actin (αSMA), aberrant formation of actin stress fibres and epithelial to mesenchymal transition (EMT) (Keller et al., 2009; Fuchshofer and Ernst R Tamm, 2012; Mark A. Prendes et al., 2013; Takahashi et al., 2014; Wordinger, Sharma and Clark, 2014)
miR-122-5p was one of the highest upregulated miRNAs in response to TGFβ1 in the TM in our study. This response was also previously reported in the TM and miR-122 was associated with the regulation of the TGFβ/Smad pathway [
75]. Within the TGFβ signalling pathway, miR-122-5p has predicted target interactions with TGFβR1, TGFβR2, LTBP1 and SMAD2. The levels of miR-122-5p are significantly elevated in the aqueous humour in XFG [
76] in addition to TGFβ1 [
21,
22,
23]. miR-122 is one of the most abundant miRNAs in the liver, playing an important role in liver fibrosis [
77] and other organ fibrosis targeting the TGFβ signalling pathway [
78].
There was significant upregulation of miR-182-5p in TGFβ1-treated primary human TM cells. Elevated expression of miR-182-5p was reported during stress-induced premature senescence in cultured TM cells [
79]. The absolute expression of miR-182-5p in the aqueous humour samples from glaucoma patients was elevated 2-fold [
80]. A SNP (rs76481776) in the
MIR182 gene was associated with POAG in the NEIGHBORHOOD GWAS dataset although the mechanism linking this SNP with POAG has not been elucidated [
80]. Originally described as a sensory organ-specific miRNA, miR-182 is also involved in immunity, cancer and regulation of TGFβ signalling [
81,
82,
83]. By targeting SMAD7, a negative regulator of the TGFβ signalling pathway, miR-182-5p amplifies TGFβ induced epithelial to mesenchymal transition (EMT) and metastasis of cancer cells while inhibition of miR-182-5p reduces pulmonary fibrosis [
84,
85].
miR-145-5p is abundantly expressed in the TM and smooth muscle in the eye and is highly expressed in the aqueous humour in POAG patients [
69,
86,
87]. It is a member of the miR-143/145 cluster which play a role in the regulation of IOP [
69]. miR-143/145 double knockout mice resulted in 19% decrease in IOP [
69]. miR-143/145 increases IOP by modulating actin dynamics enhancing the contractility of TM cells [
69]. Manipulation of miR-143/145 levels in the TM may offer therapeutic potential in glaucoma [
69].
The expression of miR-146b-5p was downregulated with TGFβ treatment. miR-146b-5p is a member of the miR-146 family of miRNAs, consisting of miR-146a-5p and miR-146b-5p. These two miRNAs only differ by two nucleotides on the 3′ end of their mature strand, sharing the same seed region [
88]. During replicative senescence in human TM cells, miR-146a upregulation limited inflammatory responses [
89]. miR-146a regulates the pro-inflammatory NF-κB signalling pathway by inhibiting interleukin-1 receptor-associated kinase 1 (IRAK1) to inhibit inflammation [
90]. Following lentiviral delivery intracamerally of miR-146a in rats there was a sustained reduction of IOP of 4.4 ± 2.9 mmHg over 8 months [
68]. The mechanism of IOP lowering was postulated as likely complex and potentially involving alterations in TGFβ signalling, ROCK inhibition and/or NF-κB signalling [
68]. While miR-146b-5p has not been studied in the TM, it also inhibited NF-κB-induced interleukin 6 (IL-6) expression in breast cancer cells [
91]. This suggests that miR-146b-5p may play a similar role to miR-146a-5p in the TM.
miRNA clusters and families
The action of miRNAs can be synergistic and this is exemplified by miRNA clusters which consist of multiple miRNAs with a common promoter resulting in co-expression and coordinated action [
92,
93,
94]. The miR-17-92 cluster was enriched in both the TGFβ1 and TGFβ2 datasets. This cluster consists of six mature miRNAs: miR-17, miR-18a, miR-19a, miR-19b, miR-20a and miR-92a [
95]. Through gene duplication, this cluster has evolved to form two paralogs: the miR-106a-363 cluster and the miR-106b-25 cluster, shown in
Figure 9 [
55]. As some of the miRNAs share a seed sequence, they have been divided into four main miRNA families: the miR-17, miR-18, miR-19, and miR-92 families [
55]. An important pathway targeted by members of the miR-17-92 family is the TGFβ signalling pathway [
96,
97]. miR-17-5p is down-regulated in response to TGFβ1 treatment in TM cells. TM cells under oxidative stress down-regulate miR-17-5p which may regulate the proliferation and apoptosis of TM cells through its direct targeting of tumour suppressor PTEN [
98], which is up-regulated in TM cells following TGFβ treatment [
99]. Previous research from our group has shown miR-18a-5p expression increased in TM cells following TGFβ2, consistent with our miRNA-Seq results [
100]. miR-18a-5p targets connective tissue growth factor (CTGF), which is a fibrotic gene elevated in the TM of glaucoma patients [
101]. CTGF induces actin stress fibres and increases TM cell contractility by activating RhoA [
102]. Lentiviral-mediated overexpression of miR-18a reduced TGFβ2-induced CTGF expression in TM cells and showed a reduction in TGFβ2-induced contraction of collagen gels [
100]. miR-18a-5p is a potential miRNA therapeutic in glaucoma because of its ability to inhibit CTGF-associated increased TM cell contractility [
100].
The synergistic action of miRNAs is also supported by miRNA families [
94,
103]. A miRNA family consists of two or more miRNAs with high sequence similarity and can be located in one or more distinct clusters [
94]. The miR-29 family regulates a plethora of fibrosis associated genes in various cell types including lungs, liver, heart, eye and other organs (Cushing, Kuang and Lü, 2015; Deng et al., 2017; Smyth, Callaghan, Colin E Willoughby, et al., 2022). The family is a known downstream target in the TGFβ/Smad pathway, and the phosphorylation of Smad3 by TGFβ causes miR-29 to be downregulated [
61]. Our study detected down-regulation of miR-29b-3p in both TGFβ1 and TGFβ2 treated TM cells, as seen in previous reported [
105,
106]. Transfection of human TM cells with miR-29b-3p mimic down-regulated ECM proteins including collagens, laminin subunit gamma 1 (LAMC1), and fibrillin 1 (FBN1), and secreted protein acidic rich in cysteine (SPARC), a gene involved in ECM remodelling [
107]. Alterations in SPARC, and collagens I and IV, cause significant changes in IOP in transgenic mice [
108]. Our KEGG analysis identified the PI3K-Akt signalling pathway to be over-represented with miR-29b-3p expression. Overexpression of miR-29b-3p represses the PI3K-Akt pathway reducing collagen I expression in human Tenon’s ocular fibroblasts [
109]. miR-29b-3p down-regulation in the TM may contribute to increased TGFβ-induced ECM components. miR-29 plays a critical role in regulating ECM production and is an anti-fibrotic miRNA [
110] and miRNA-29b mimics attenuate pulmonary fibrosis
in vivo [
111].
miRNA strands
The miRNA biogenesis pathway involves sequential processing of the pri-miRNA into pre-miRNA and finally into a mature miRNA [
112]. Following Drosha processing of pri-miRNAs in the nucleus, pre-miRNAs are exported into the cytoplasm and cleaved by Dicer, resulting in the miRNA duplex [
65]. Transcription produces equal amounts of both strands of miRNA duplexes; however, their accumulation is mostly asymmetric at steady state [
113]. As proposed in the oncology field [
114], the results from our study highlight that both 3p- and 5p-arms from a miRNA warrant independent study.
miR-21-5p is known to be one of the most overexpressed miRNAs in response to tissue injury and to play an important role in fibrosis [
115,
116]. During miRNA biogenesis, pre-miR-21 is exported by Exportin 5 and processed by Dicer to release mature hsa-miR-21 (also known as hsa-miR-21-5p, the biologically dominant arm) and hsa-miR-21-3p (formerly named hsa-miR-21*), previously considered the less abundant or active miRNA strand [
117,
118,
119,
120]. Pro-fibrotic miR-21-5p binds to Smad7, an inhibitory Smad, and thus amplifies the TGFβ signalling pathway, causing fibrotic responses [
121,
122]. There is crosstalk between miR-21-5p and a variety of signalling pathways: TGFβ/SMAD, PI3K/AKT and ERK/MAPK signalling pathways, in the regulation of fibrotic processes [
123]. A role of miR-21-5p in regulating IOP and outflow facility has been reported [
124]. Topical administration of a synthetic miR-21-5p mimic increased miR-21-5p expression in the TM while reducing IOP by 17% [
124]. Using RNA-sequencing and pathway analysis, with the predicted downstream target genes of miR-21-5p identified, they found a pathway involving FGF18, SMAD7 and MMP9 based on protein-protein interaction networks [
124]. RT-qPCR confirmed the downregulation of SMAD7 and FGF18 by a miR-21-5p mimic suggesting that miR-21-5p targets SMAD7 and FGF18 to encourage ECM degradation by MMP9 in the TM [
124]. In our data miR-21-5p expression was unaltered by TGFβ2 treatment in the TM but significantly downregulated with TGFβ1 treatment. Unexpectedly, our data shows an upregulation of miR-21-3p with both TGFβ1 and -β2 treatment. There is emerging evidence for a biological role for miR-21-3p in malignancy [
114,
125], vascular biology [
126,
127] and in the regulation of TGFβ signalling [
117]. In hepatocellular carcinoma, miR-21-3p regulates both TGFβ and Hippo signalling via SMAD7 and YAP1 [
117]. Overexpression of miR-21-3p directly silences SMAD7 expression and reduces the stability of the SMAD7/YAP1 complex allowing YAP1 translocation to the nucleus and resultant profibrotic gene expression [
117]. Further work is required to understand the role of the -5p and -3p miR-21 strands in TM pathophysiology.
miR-708 is not a widely studied miRNA in ocular tissues, however its expression has been reported in retinal ganglion cells [
128]. miR-708-5p is the more abundant strand and is involved in oncogenesis [
129,
130]. miR-708-5p was upregulated in the TM in response to TGFβ2 but the passenger strand (miR-708-3p) was significantly upregulated in response to TGFβ1 and -β2. A disintegrin and metalloproteinase 17 (ADAM17), which is overexpressed in fibrotic disorders [
131,
132,
133] and is expressed in TM cells [
134,
135], is a direct target of miR-708-3p. By targeting ADAM17, miR-708-3p represses the GATA/STAT3 signalling pathway in idiopathic pulmonary fibrosis (IPF) reducing fibrosis [
136]. GATA6 promotes fibroblast differentiation into myofibroblasts in IPF by mediating the α-SMA-inducing signal of TGFβ1 [
137,
138], and STAT3, is abundantly expressed in multiple fibrotic disorders [
139]. In breast cancer cells miR-708-3p inhibits EMT by directly targeting ZEB1, cadherin 2 and vimentin [
140]. Therefore, miR-708-3p could present a new therapeutic target for TM fibrosis by targeting the ADAM17-GATA/STAT pathway and EMT.
miRNA regulation of signalling pathways
A cell can simultaneously express multiple miRNAs to regulate gene expression in a holistic, intricate network with a single miRNA targeting multiple mRNAs and a single mRNA targeted by multiple miRNAs [
92,
93,
141]. Our data can be considered in terms of specific miRNAs (miRNA-centric) but miRNAs work in networks to control cellular pathways and processes and a pathway-centric view of miRNA action is also required [
142]. Several of the DEmiRs altered by TGFβ in the TM have been implicated in the regulation of the TGFβ signalling pathway [
96,
97,
143]. Interestingly, the TGFβ signalling pathway was only significantly enriched in TGFβ1 down-regulated miRNAs in the TM. The transforming growth factor beta receptor 2 (TGFβR2) is targeted by miR-18a-5p [
144], miR-20a-5p, miR-29b-3p and miR-204-5p which were all significantly downregulated in the TM in response to TGFβ1. Smad2/3, the regulatory Smads in the canonical TGFβ signalling pathway, are also targeted by miR-18a-5p [
145,
146,
147,
148]. Lentiviral expression of miR-18a-5p in bleomycin mice presented lowered levels of phosphorylated Smad2/3 and a reduction in pulmonary fibrosis [
144]. There are several overlapping miRNAs involved in the regulation of both the TGFβ signalling pathway and the Hippo signalling pathway.
The Hippo signalling pathway is considered a tumour suppressor pathway, playing important roles in cell differentiation and cell proliferation [
149,
150]. Our pathway enrichment analysis identified the Hippo signalling pathway as significantly enriched in both TGFβ1 and -β2 miRNA-Seq datasets in the TM, associated with both up- and down-regulated miRNAs. TGFβ2 upregulated the expression of miR-181c-5p in TM cells and miR-181c-5p inhibits Hippo signalling through its target large tumour suppressor 2 (LATS2) and Salvador Family WW Domain Containing Protein 1 (SAV1) [
151,
152,
153]. SAV1 bind to the Macrophage Stimulating 1/2 (MST1/2) kinases forming an enzyme complex which phosphorylates LATS1/2 [
154,
155]. The LATS1/2 kinases phosphorylate Yes-Associated Protein 1 (YAP) which in turn prevents nuclear translocation and signals its proteasomal degradation [
156]. Therefore, miR-181c-5p disrupts the negative regulation of Hippo signalling and promotes the activation of YAP by targeting LATS2 and SAV1 [
151,
152]. YAP/TAZ also stimulates the nuclear accumulation of SMAD complexes to increase their transcriptional activity [
157,
158,
159]. YAP/TAZ nuclear levels are elevated by TGFβ2 in both normal and glaucomatous human TM cells while inhibition of YAP/TAZ resulted in reduced focal adhesions, ECM remodelling and cell contractility [
160]. When Hippo signalling is inhibited the nuclear translocation of YAP/TAZ induces the transcriptional activity of TEA domain (TEAD) family members which increases the expression of CTGF which is associated with glaucoma and TM fibrosis [
100,
161,
162].
MAPK signalling pathway and PI3K-Akt signalling pathway were two of the most enriched pathways targeted by DEmiRs in both TGFβ1 and -β2-treated TM cells. AKT1/2/3, MAPK1, PTEN, RAC1 and PIK3CG were associated with multiple DEmiRs. Rac family small GTPase 1 (RAC1), targeted by miR-146a-5p [
163,
164] and miR-574-3p [
165], activates p38-MAPK signalling [
166], increases ECM production in TM cells and elevates SPARC and proinflammatory IL-6 in TM cells [
167,
168]. SPARC binds to ECM proteins and regulates the expression of matrix metalloproteinases (MMPs) [
169]. SPARC expression is up-regulated by TGFβ2 in TM cells and is inhibited by the miR-29 family in the TM [
106,
170]. Up-regulation of IL-6 by TGFβ1 and TGFβ2 through p38-MAPK signalling, affects mechanical stress in TM cells [
171,
172]. RAF1, targeted by miR-125a-5p [
173], leads to MAP ERK kinase [
174] and ERK1/2 activation [
166]. ERK1/2 can elevate PAI-1 expression in the TM, ultimately leading to increased ECM production [
175].
The PI3K-Akt signalling pathway can promote cell survival and suppress apoptosis [
176]. As there is a decline in TM cellularity in glaucoma due to apoptosis and ECM remodelling [
177,
178], AKT activation may play an important role in the protection of TM cellularity. In our datasets, up-regulated miRNAs including miR-29b-1-5p [
179], miR-122-5p [
180,
181], miR-143-3p [
182], miR-182-5p [
183,
184], miR-214-3p [
185] and miR-708-5p [
186,
187] are all putative targets of AKT. PTEN indirectly influences cellular proliferation and apoptosis as a major negative regulator of the Akt signalling pathway [
188,
189]. Interestingly, six down-regulated miRNAs in our dataset target PTEN [
190,
191,
192,
193,
194,
195,
196,
197,
198,
199,
200]. Specifically studied in the TM, the down-regulation of miR-17-5p increases PTEN expression leading to increased apoptosis and decreased proliferation of TM cells under oxidative stress conditions [
98].
Inhibition of Wnt signalling has previously been shown in glaucomatous TM cells and is associated with TM cell stiffening (Mao et al., 2012; Morgan et al., 2015). Secreted frizzled-related protein-1 (SFRP1), targeted by miR-582-3p (Wang et al., 2020) which was down-regulated in TGFβ2-treated TM cells, inhibits the Wnt signalling pathway and is associated with increased IOP [
207]. Activating Wnt signalling through miRNA targets could restore the normal phenotype caused by Wnt inactivation, through repression of ECM genes (SPARC and CTGF), cross-linking genes (LOX) and inhibitors of MMPs (TIMP1 and PAI-1) [
208,
209].
Figure 1.
Significant differential expression of miRNAs in response to TGFβ1 treatment (5 ng/mL 24 hours). Volcano plot identifying differentially expressed miRNAs in response to TGFβ1 treatment in TM cells. A threshold was applied using a statistical significance of p < 0.05 and log2FC > 1. Grey and green dots represent miRNAs failing to meet the significance cut-off. Blue dots represent miRNAs that have met the p-value but are below the log2FC criteria. Red dots represent those miRNAs that have met the threshold with a p < 0.05 and log2FC > 1. Those on the left corner of the plot are down-regulated whilst those on the right area of the plot are the up-regulated miRNAs. Grey dots = Not Significant (NS), Red dots = p-value < 0.05 & Log2FC ≥ 1, Blue dots = p-value < 0.05. P-value is represented by the dashed horizontal line and Log2FC is represented by the vertical dashed lines.
Figure 1.
Significant differential expression of miRNAs in response to TGFβ1 treatment (5 ng/mL 24 hours). Volcano plot identifying differentially expressed miRNAs in response to TGFβ1 treatment in TM cells. A threshold was applied using a statistical significance of p < 0.05 and log2FC > 1. Grey and green dots represent miRNAs failing to meet the significance cut-off. Blue dots represent miRNAs that have met the p-value but are below the log2FC criteria. Red dots represent those miRNAs that have met the threshold with a p < 0.05 and log2FC > 1. Those on the left corner of the plot are down-regulated whilst those on the right area of the plot are the up-regulated miRNAs. Grey dots = Not Significant (NS), Red dots = p-value < 0.05 & Log2FC ≥ 1, Blue dots = p-value < 0.05. P-value is represented by the dashed horizontal line and Log2FC is represented by the vertical dashed lines.
Figure 2.
KEGG pathway analysis of significantly up-regulated TGFβ1-responsive miRNAs in TM cells. KEGG pathway analysis of the significant differentially expressed miRNAs (p < 0.05) was performed. The enrichment plot presents the top 30 KEGG pathway enrichment terms for differentially expressed miRNAs up-regulated in response to TGFβ1 in TM cells. The X-axis label represents Enrichment Score, the amount of differentially expressed genes enriched in the pathway, and Y-axis label represents the enriched pathway. The size and colour of the bubble represent the amount of differentially expressed genes enriched in the pathway and the enrichment significance respectively.
Figure 2.
KEGG pathway analysis of significantly up-regulated TGFβ1-responsive miRNAs in TM cells. KEGG pathway analysis of the significant differentially expressed miRNAs (p < 0.05) was performed. The enrichment plot presents the top 30 KEGG pathway enrichment terms for differentially expressed miRNAs up-regulated in response to TGFβ1 in TM cells. The X-axis label represents Enrichment Score, the amount of differentially expressed genes enriched in the pathway, and Y-axis label represents the enriched pathway. The size and colour of the bubble represent the amount of differentially expressed genes enriched in the pathway and the enrichment significance respectively.
Figure 3.
KEGG pathway analysis of significantly down-regulated TGFβ1-responsive miRNAs in TM cells. KEGG pathway analysis of the significant differentially expressed miRNAs (p < 0.05) was performed. The enrichment plot presents the top 30 KEGG pathway enrichment terms for differentially expressed miRNAs down-regulated in response to TGFβ1 in TM cells. The X-axis label represents Enrichment Score, the amount of differentially expressed genes enriched in the pathway, and Y-axis label represents the enriched pathway. The size and colour of the bubble represent the amount of differentially expressed genes enriched in the pathway and the enrichment significance respectively.
Figure 3.
KEGG pathway analysis of significantly down-regulated TGFβ1-responsive miRNAs in TM cells. KEGG pathway analysis of the significant differentially expressed miRNAs (p < 0.05) was performed. The enrichment plot presents the top 30 KEGG pathway enrichment terms for differentially expressed miRNAs down-regulated in response to TGFβ1 in TM cells. The X-axis label represents Enrichment Score, the amount of differentially expressed genes enriched in the pathway, and Y-axis label represents the enriched pathway. The size and colour of the bubble represent the amount of differentially expressed genes enriched in the pathway and the enrichment significance respectively.
Figure 4.
Expression levels of four candidate miRNAs in TGFβ1-stimulated TM cells. Candidate miRNAs were identified as significantly differentially expressed through miRNA-Seq. (A) hsa-miR-122-5p (B) hsa-miR-146b-5p (C) hsa-miR-182-5p (D) hsa-miR-204-5p. Vehicle controls are denoted as “Control” on graphs and TGFβ1 treated cells as “TGFβ1”. Individual values for donors 1, 2 and 3 are shown. Data was normalised to U6 control and analysed using the ΔΔCt method. Circles represent individual donor gene without TGFβ1 treatment and squares represent donors with TGFβ1 treatment. An asterisk denotes significant differential gene expression after treatment (* = p < 0.05, ** = p < 0.005).
Figure 4.
Expression levels of four candidate miRNAs in TGFβ1-stimulated TM cells. Candidate miRNAs were identified as significantly differentially expressed through miRNA-Seq. (A) hsa-miR-122-5p (B) hsa-miR-146b-5p (C) hsa-miR-182-5p (D) hsa-miR-204-5p. Vehicle controls are denoted as “Control” on graphs and TGFβ1 treated cells as “TGFβ1”. Individual values for donors 1, 2 and 3 are shown. Data was normalised to U6 control and analysed using the ΔΔCt method. Circles represent individual donor gene without TGFβ1 treatment and squares represent donors with TGFβ1 treatment. An asterisk denotes significant differential gene expression after treatment (* = p < 0.05, ** = p < 0.005).
Figure 5.
Significant differential expression of miRNAs in response to TGFβ2 treatment (5 ng/mL 24 hours). Volcano Plot identifying differentially expressed miRNAs in response to TGFβ2 treatment in TM cells. A threshold was applied using a statistical significance of p < 0.05 and log2FC > 1. Grey and green dots represent miRNAs failing to meet the significance cut-off. Blue dots represent miRNAs that have met the p-value but are below the log2FC criteria. Red dots represent those miRNAs that have met the threshold with a p < 0.05 and log2FC > 1. Those on the left corner of the plot are down-regulated whilst those on the right area of the plot are the up-regulated miRNAs. Grey dots - Not Significant (NS), Red dots = p-value < 0.05 & Log2FC ≥ 1, Blue dots = p-value < 0.05. P-value is represented by the dashed horizontal line and Log2FC is represented by the vertical dashed lines.
Figure 5.
Significant differential expression of miRNAs in response to TGFβ2 treatment (5 ng/mL 24 hours). Volcano Plot identifying differentially expressed miRNAs in response to TGFβ2 treatment in TM cells. A threshold was applied using a statistical significance of p < 0.05 and log2FC > 1. Grey and green dots represent miRNAs failing to meet the significance cut-off. Blue dots represent miRNAs that have met the p-value but are below the log2FC criteria. Red dots represent those miRNAs that have met the threshold with a p < 0.05 and log2FC > 1. Those on the left corner of the plot are down-regulated whilst those on the right area of the plot are the up-regulated miRNAs. Grey dots - Not Significant (NS), Red dots = p-value < 0.05 & Log2FC ≥ 1, Blue dots = p-value < 0.05. P-value is represented by the dashed horizontal line and Log2FC is represented by the vertical dashed lines.
Figure 6.
KEGG pathway analysis of significantly up-regulated TGFβ2-responsive miRNAs in TM cells. KEGG pathway analysis of the significant differentially expressed miRNAs (p < 0.05) was performed. The enrichment plot presents the top 30 KEGG pathway enrichment terms for differentially expressed miRNAs up-regulated in response to TGFβ2 in TM cells. The X-axis label represents Enrichment Score, the amount of differentially expressed genes enriched in the pathway, and Y-axis label represents the enriched pathway. The size and colour of the bubble represents the amount of differentially expressed genes enriched in the pathway and the enrichment significance.
Figure 6.
KEGG pathway analysis of significantly up-regulated TGFβ2-responsive miRNAs in TM cells. KEGG pathway analysis of the significant differentially expressed miRNAs (p < 0.05) was performed. The enrichment plot presents the top 30 KEGG pathway enrichment terms for differentially expressed miRNAs up-regulated in response to TGFβ2 in TM cells. The X-axis label represents Enrichment Score, the amount of differentially expressed genes enriched in the pathway, and Y-axis label represents the enriched pathway. The size and colour of the bubble represents the amount of differentially expressed genes enriched in the pathway and the enrichment significance.
Figure 7.
KEGG pathway analysis of significantly down-regulated TGFβ2-responsive miRNAs in TM cells. KEGG pathway analysis of the significant differentially expressed miRNAs (p < 0.05) was performed. The enrichment plot presents the top 30 KEGG pathway enrichment terms for differentially expressed miRNAs down-regulated in response to TGFβ2 in TM cells. The X-axis label represents Enrichment Score, the amount of differentially expressed genes enriched in the pathway, and Y-axis label represents the enriched pathway. The size and colour of the bubble represents the amount of differentially expressed genes enriched in the pathway and the enrichment significance.
Figure 7.
KEGG pathway analysis of significantly down-regulated TGFβ2-responsive miRNAs in TM cells. KEGG pathway analysis of the significant differentially expressed miRNAs (p < 0.05) was performed. The enrichment plot presents the top 30 KEGG pathway enrichment terms for differentially expressed miRNAs down-regulated in response to TGFβ2 in TM cells. The X-axis label represents Enrichment Score, the amount of differentially expressed genes enriched in the pathway, and Y-axis label represents the enriched pathway. The size and colour of the bubble represents the amount of differentially expressed genes enriched in the pathway and the enrichment significance.
Figure 8.
Expression levels of five candidate miRNAs in TGFβ2-stimulated TM cells. Candidate miRNAs were identified as significantly differentially expressed through miRNA-Seq. (A) hsa-miR-21-3p (B) hsa-miR-29b-3p (C) hsa-miR-145-5p (D) hsa-miR-204-5p. Vehicle controls are denoted as “Control” on graphs and TGFβ2 treated cells as “TGFβ2”. Individual values for donors 1, 2 and 3 are shown. Data was normalised to U6 control and analysed using the ΔΔCt method. Circles represent individual donor gene without TGFβ2 treatment and squares represent donors with TGFβ2 treatment. An asterisk denotes significant differential gene expression after treatment (* = p < 0.05, ** = p < 0.005).
Figure 8.
Expression levels of five candidate miRNAs in TGFβ2-stimulated TM cells. Candidate miRNAs were identified as significantly differentially expressed through miRNA-Seq. (A) hsa-miR-21-3p (B) hsa-miR-29b-3p (C) hsa-miR-145-5p (D) hsa-miR-204-5p. Vehicle controls are denoted as “Control” on graphs and TGFβ2 treated cells as “TGFβ2”. Individual values for donors 1, 2 and 3 are shown. Data was normalised to U6 control and analysed using the ΔΔCt method. Circles represent individual donor gene without TGFβ2 treatment and squares represent donors with TGFβ2 treatment. An asterisk denotes significant differential gene expression after treatment (* = p < 0.05, ** = p < 0.005).
Figure 14.
Expression levels of miR-708-5p and miR-708-3p in TGFβ1 and β2-stimulated TM cells. (A) hsa-miR-708-3p (B) hsa-miR-708-5p. Individual values for donors 1, 2 and 3 are shown. Data was normalised to U6 control and analysed using the ΔΔCt method. Circles represent individual donor gene without TGFβ treatment and squares represent donors with TGFβ treatment. An asterisk denotes significant differential gene expression after treatment (* = p < 0.05, *** = p < 0.0005).
Figure 14.
Expression levels of miR-708-5p and miR-708-3p in TGFβ1 and β2-stimulated TM cells. (A) hsa-miR-708-3p (B) hsa-miR-708-5p. Individual values for donors 1, 2 and 3 are shown. Data was normalised to U6 control and analysed using the ΔΔCt method. Circles represent individual donor gene without TGFβ treatment and squares represent donors with TGFβ treatment. An asterisk denotes significant differential gene expression after treatment (* = p < 0.05, *** = p < 0.0005).
Figure 15.
Expression levels of miR-21-3p and miR-21-5p in TGFβ1 and β2-stimulated TM cells. (A) hsa-miR-21-3p (B) hsa-miR-21-5p. Individual values for donors 1, 2 and 3 are shown. Data was normalised to U6 control and analysed using the ΔΔCt method. Circles represent individual donor gene without TGFβ1 treatment and squares represent donors with TGFβ1 treatment. An asterisk denotes significant differential gene expression after treatment (** = p < 0.005).
Figure 15.
Expression levels of miR-21-3p and miR-21-5p in TGFβ1 and β2-stimulated TM cells. (A) hsa-miR-21-3p (B) hsa-miR-21-5p. Individual values for donors 1, 2 and 3 are shown. Data was normalised to U6 control and analysed using the ΔΔCt method. Circles represent individual donor gene without TGFβ1 treatment and squares represent donors with TGFβ1 treatment. An asterisk denotes significant differential gene expression after treatment (** = p < 0.005).
Table 1.
Top 30 significantly up-regulated miRNAs in response to TGFβ1 (5 ng/mL) treatment for 24 hours. MiRNAs are ranked by Fold Change. Significance defined as p-value < 0.05. log2FC = Log2 Fold Change.
Table 1.
Top 30 significantly up-regulated miRNAs in response to TGFβ1 (5 ng/mL) treatment for 24 hours. MiRNAs are ranked by Fold Change. Significance defined as p-value < 0.05. log2FC = Log2 Fold Change.
miRNAs |
Fold Change |
Log2FC |
P-value |
hsa-miR-122-5p |
9.13380754 |
3.19121639 |
6.15E-11 |
hsa-miR-139-5p |
3.25102103 |
1.70089289 |
1.38E-05 |
hsa-miR-3065-5p |
2.89575179 |
1.53393795 |
4.57E-05 |
hsa-miR-6724-5p |
2.86974573 |
1.52092291 |
8.51E-06 |
hsa-miR-3065-3p |
2.8198025 |
1.49559412 |
0.00020201 |
hsa-miR-1275 |
2.74691918 |
1.45781447 |
3.19E-05 |
hsa-miR-122b-5p |
2.53489937 |
1.34192848 |
0.01283611 |
hsa-miR-10395-5p |
2.4233795 |
1.27702035 |
0.00046603 |
hsa-miR-10395-3p |
2.42334707 |
1.27700104 |
0.00048254 |
hsa-miR-183-5p |
2.25763024 |
1.17480922 |
0.00134539 |
hsa-miR-424-3p |
2.22458455 |
1.15353593 |
0.00616844 |
hsa-miR-10401-5p |
2.19097642 |
1.13157396 |
0.00394718 |
hsa-miR-23a-5p |
2.04351302 |
1.03105144 |
3.24E-05 |
hsa-miR-6716-3p |
1.96658773 |
0.97569454 |
0.00379127 |
hsa-miR-503-3p |
1.92984739 |
0.94848677 |
0.03910098 |
hsa-miR-146a-5p |
1.89191456 |
0.91984694 |
0.00017454 |
hsa-miR-181b-5p |
1.79978193 |
0.84782212 |
4.79E-06 |
hsa-miR-708-5p |
1.79528708 |
0.84421456 |
0.0001733 |
hsa-miR-182-5p |
1.75251953 |
0.80943052 |
0.01995341 |
hsa-miR-543 |
1.73760333 |
0.79709877 |
0.00498442 |
hsa-miR-3679-5p |
1.70656765 |
0.77109761 |
0.01196514 |
hsa-miR-210-3p |
1.6996398 |
0.76522903 |
0.00029772 |
hsa-miR-216a-5p |
1.64469194 |
0.71781738 |
0.01385089 |
hsa-miR-365a-5p |
1.63395301 |
0.7083665 |
0.01578449 |
hsa-miR-129-5p |
1.61816529 |
0.69435898 |
0.0061433 |
hsa-miR-10401-3p |
1.61801867 |
0.69422826 |
0.00669733 |
hsa-miR-10527-5p |
1.59469424 |
0.67327984 |
0.0141122 |
hsa-miR-181b-3p |
1.59404885 |
0.67269584 |
0.04147052 |
hsa-miR-24-2-5p |
1.57231126 |
0.65288685 |
0.00099304 |
hsa-miR-495-3p |
1.54712784 |
0.62959242 |
0.02393389 |
Table 2.
Top 30 significantly down-regulated miRNAs in response to TGFβ1 (5 ng/mL) treatment for 24 hours. MiRNAs are ranked by Fold Change. Significance defined as p-value < 0.05. log2FC = Log2 Fold Change.
Table 2.
Top 30 significantly down-regulated miRNAs in response to TGFβ1 (5 ng/mL) treatment for 24 hours. MiRNAs are ranked by Fold Change. Significance defined as p-value < 0.05. log2FC = Log2 Fold Change.
miRNAs |
Fold Change |
Log2FC |
P-value |
hsa-miR-146b-5p |
0.4822713 |
-1.0520831 |
1.96E-06 |
hsa-miR-146b-3p |
0.48914069 |
-1.0316786 |
0.00766537 |
hsa-miR-651-5p |
0.50861592 |
-0.9753515 |
0.00545332 |
hsa-miR-204-5p |
0.52483108 |
-0.9300749 |
9.46E-05 |
hsa-miR-99a-5p |
0.53341448 |
-0.9066711 |
0.00011864 |
hsa-miR-218-1-3p |
0.55523124 |
-0.8488393 |
0.00496279 |
hsa-miR-660-5p |
0.56382312 |
-0.8266855 |
0.00028811 |
hsa-miR-549a-3p |
0.57752493 |
-0.7920449 |
0.01521947 |
hsa-miR-26a-1-3p |
0.58078639 |
-0.7839205 |
0.00053314 |
hsa-miR-500b-3p |
0.58162831 |
-0.7818306 |
0.03273988 |
hsa-miR-15a-5p |
0.58925697 |
-0.7630312 |
2.90E-05 |
hsa-miR-452-3p |
0.59020601 |
-0.7607095 |
0.00077017 |
hsa-miR-218-5p |
0.59343236 |
-0.7528445 |
1.37E-05 |
hsa-miR-26a-2-3p |
0.60264724 |
-0.7306143 |
0.03565943 |
hsa-miR-1255a |
0.61107737 |
-0.710573 |
0.0361198 |
hsa-miR-502-5p |
0.61558839 |
-0.6999621 |
0.03998012 |
hsa-miR-99a-3p |
0.61886292 |
-0.6923082 |
0.03455279 |
hsa-miR-20b-5p |
0.61932422 |
-0.6912332 |
0.04897627 |
hsa-miR-9985 |
0.62109457 |
-0.6871151 |
0.00625545 |
hsa-miR-195-5p |
0.62558473 |
-0.6767228 |
0.00080717 |
hsa-let-7c-3p |
0.63013432 |
-0.6662687 |
0.03065585 |
hsa-miR-19a-3p |
0.63378238 |
-0.6579405 |
0.00243884 |
hsa-miR-335-3p |
0.63422802 |
-0.6569265 |
0.02491361 |
hsa-miR-19b-3p |
0.6385444 |
-0.6471412 |
0.00104799 |
hsa-miR-335-5p |
0.64169946 |
-0.6400303 |
0.00237981 |
hsa-miR-29b-3p |
0.64655536 |
-0.6291542 |
0.00472803 |
hsa-miR-497-5p |
0.6492189 |
-0.6232231 |
0.00294707 |
hsa-miR-20a-3p |
0.65002719 |
-0.621428 |
0.04420571 |
hsa-miR-454-5p |
0.65124762 |
-0.6187219 |
0.03029567 |
hsa-miR-101-3p |
0.65134387 |
-0.6185087 |
0.00085122 |
Table 3.
Top 30 significantly up-regulated miRNAs in response to TGFβ2 (5 ng/mL) treatment for 24 hours. MiRNAs are ranked by Fold Change. Significance defined as p-value < 0.05. log2FC = Log2 Fold Change.
Table 3.
Top 30 significantly up-regulated miRNAs in response to TGFβ2 (5 ng/mL) treatment for 24 hours. MiRNAs are ranked by Fold Change. Significance defined as p-value < 0.05. log2FC = Log2 Fold Change.
miRNA Name |
Fold Change |
Log2FC |
P-value |
hsa-miR-181b-2-3p |
3.53991903 |
1.82371636 |
1.27E-06 |
hsa-miR-503-3p |
3.18394765 |
1.67081662 |
3.60E-18 |
hsa-miR-424-3p |
2.85950834 |
1.51576711 |
1.05E-06 |
hsa-miR-21-3p |
2.00735084 |
1.00529279 |
1.26E-16 |
hsa-miR-708-3p |
1.99270313 |
0.99472679 |
5.17E-06 |
hsa-miR-6716-3p |
1.99202337 |
0.99423458 |
0.00072026 |
hsa-miR-503-5p |
1.98194499 |
0.98691692 |
1.18E-06 |
hsa-miR-27a-5p |
1.93586762 |
0.9529803 |
4.55E-12 |
hsa-miR-6724-5p |
1.89734963 |
0.92398555 |
0.00050886 |
hsa-miR-145-3p |
1.88867966 |
0.91737802 |
2.71E-07 |
hsa-miR-181a-2-3p |
1.88789033 |
0.91677496 |
9.80E-08 |
hsa-miR-3187-3p |
1.85686868 |
0.89287179 |
0.00135669 |
hsa-miR-24-2-5p |
1.8166234 |
0.86125937 |
5.52E-06 |
hsa-miR-143-5p |
1.81551189 |
0.86037638 |
8.45E-09 |
hsa-miR-708-5p |
1.81499426 |
0.85996499 |
2.20E-05 |
hsa-miR-3179 |
1.80771879 |
0.85417027 |
0.01538545 |
hsa-miR-3065-3p |
1.76608959 |
0.82055853 |
0.00122102 |
hsa-miR-10401-5p |
1.70851951 |
0.77274672 |
0.02374628 |
hsa-miR-5701 |
1.67320751 |
0.74261638 |
0.01320843 |
hsa-miR-216a-5p |
1.66610529 |
0.73647958 |
0.00576722 |
hsa-miR-135a-5p |
1.65188519 |
0.72411342 |
0.01440031 |
hsa-miR-214-5p |
1.62635075 |
0.70163843 |
0.00031568 |
hsa-miR-23a-5p |
1.58158263 |
0.66136893 |
0.0171346 |
hsa-miR-3065-5p |
1.56823909 |
0.64914552 |
0.00064297 |
hsa-miR-145-5p |
1.51098725 |
0.59549148 |
4.34E-08 |
hsa-miR-181b-5p |
1.49487096 |
0.58002095 |
0.00019705 |
hsa-miR-199b-5p |
1.41320621 |
0.49897199 |
0.0083763 |
hsa-miR-424-5p |
1.41198062 |
0.49772029 |
0.00883417 |
hsa-miR-210-3p |
1.39737981 |
0.4827242 |
6.48E-05 |
hsa-miR-6511a-3p |
1.39588043 |
0.48117537 |
0.01910117 |
Table 4.
Top 30 significantly down-regulated miRNAs in response to TGFβ2 (5 ng/mL) treatment for 24 hours. MiRNAs are ranked by Fold Change. Significance defined as p-value < 0.05. log2FC = Log2 Fold Change.
Table 4.
Top 30 significantly down-regulated miRNAs in response to TGFβ2 (5 ng/mL) treatment for 24 hours. MiRNAs are ranked by Fold Change. Significance defined as p-value < 0.05. log2FC = Log2 Fold Change.
miRNA Name |
Fold Change |
Log2FC |
P-value |
hsa-miR-6859-5p |
0.47775733 |
-1.0656501 |
0.01471161 |
hsa-miR-218-1-3p |
0.5838476 |
-0.7763363 |
3.56E-08 |
hsa-miR-20b-5p |
0.5851248 |
-0.7731837 |
0.04888215 |
hsa-miR-15a-3p |
0.58819277 |
-0.765639 |
0.01533516 |
hsa-miR-26a-1-3p |
0.60051027 |
-0.7357392 |
4.51E-07 |
hsa-miR-744-3p |
0.61105129 |
-0.7106346 |
0.00203953 |
hsa-miR-760 |
0.61267545 |
-0.7068051 |
0.00696877 |
hsa-miR-3613-5p |
0.62166996 |
-0.6857792 |
0.00247998 |
hsa-miR-485-5p |
0.64873167 |
-0.6243062 |
0.00044685 |
hsa-miR-3618 |
0.6551584 |
-0.6100843 |
0.00031305 |
hsa-miR-96-5p |
0.66784058 |
-0.5824243 |
0.04879471 |
hsa-let-7c-3p |
0.66958237 |
-0.5786666 |
0.00046092 |
hsa-miR-26a-2-3p |
0.70516762 |
-0.5039619 |
0.00985704 |
hsa-miR-454-5p |
0.70792943 |
-0.4983225 |
0.01136527 |
hsa-miR-452-3p |
0.73641685 |
-0.4414055 |
0.01341871 |
hsa-miR-302b-3p |
0.74394926 |
-0.4267239 |
0.03858273 |
hsa-miR-379-3p |
0.74729697 |
-0.4202464 |
0.02575367 |
hsa-miR-200a-3p |
0.75177354 |
-0.41163 |
0.03409936 |
hsa-miR-330-3p |
0.75655443 |
-0.4024842 |
0.00629521 |
hsa-miR-652-3p |
0.76101822 |
-0.3939971 |
0.04107676 |
hsa-miR-330-5p |
0.76266111 |
-0.390886 |
0.0358708 |
hsa-miR-582-3p |
0.7793746 |
-0.3596112 |
0.03470739 |
hsa-miR-218-5p |
0.80206106 |
-0.318216 |
0.00150533 |
hsa-miR-324-3p |
0.81716595 |
-0.291299 |
0.0171506 |
hsa-miR-29b-3p |
0.8178589 |
-0.2900761 |
0.03715585 |
hsa-miR-204-5p |
0.82376963 |
-0.2796872 |
0.01111315 |
hsa-miR-887-3p |
0.84285826 |
-0.2466381 |
0.03219643 |
hsa-miR-138-5p |
0.86349689 |
-0.2117371 |
0.03055703 |