Transcriptome landscape of the adrenal gland and superior cervical ganglion from hypertension-induced left ventricular hypertrophy rat model

Abstract

Background: Hypertension-induced left ventricular hypertrophy (LVH) is a cardiac structural remodeling and dysfunction resulting from chronic hypertension and is an independent risk factor for cardiovascular morbidity and mortality. Studies have implicated the involvement of the adrenal gland (AG) and superior cervical ganglion (SCG) in hypertension regulation. However, the molecular mechanisms of AG and SCG during hypertension-induced LVH remain unclear. In this study, we investigated the transcriptome characteristics of the left ventricle, AG, and SCG in 24-week-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats using transcriptome sequencing (RNA-seq) technology.

Results: We identified 671 differentially expressed genes (DEGs) in the left ventricle, 1596 DEGs in the AG, and 343 DEGs in the SCG between SHR and WKY rats. Functional analysis revealed that these DEGs were involved in pathways related to immune inflammation, cellular senescence, metabolic responses, and synaptic transmission. We also identified the top 20 hub genes specific to each of the three organs. PPI network analysis showed that these hub genes were highly interconnected and clustered into three functional modules. KEGG pathway analysis revealed that the hub genes in the left ventricle and AG were mainly enriched in inflammation-related pathways, while the hub genes in the SCG were primarily enriched in synapse-related pathways. Venn diagram analysis identified 63 overlapping DEGs across the three organs, with 59 DEGs exhibiting consistent expression changes.

Conclusions: In summary, our study elucidates the transcriptome features of AG and SCG during hypertension-induced LVH in SHR.

Keywords: Adrenal gland; Hypertension; Left ventricular hypertrophy; RNA-seq; Superior cervical ganglion.

Fig. 1

Cardiac hypertrophy and dysfunction of SHR. A Representative images and measurement parameters of M-mode echocardiography from SHR and WKY rats. Scale bar = 0.5 cm. B Sirius Red staining of myocardial fibrosis (left); Scale bar = 50 μm. Quantification of myocardial fibrosis area (right). C FITC-labelled WGA staining of SHR and WKY rats (left); Scale bar = 50 μm. Quantification of cardiomyocyte cross-sectional area in sections of hearts (right). Except for the LVPWd data, which are presented as median and interquartile range, all other data are expressed as mean ± SD. The bar chart's numbers represent the number of animals. BPM: beat per minute; EF: ejection fraction; FS: fractional shortening; LVIDs: left ventricular internal dimension in systole; LVIDd: left ventricular internal dimension in diastole; LV mass: left ventricular mass; LVAWs: left ventricular anterior wall thickness at end-systole; LVAWd: left ventricular anterior wall thickness at end-diastole; LVPWs: left ventricular posterior wall thickness at end-systole; LVPWd: left ventricular posterior wall thickness at end-diastole. ESV: end systolic volume; EDV: end diastolic volume. ****P < 0.001; ***P < 0.005; **P < 0.01

Fig. 2

GO enrichment and KEGG analysis of DEGs in the left ventricle, AG and SCG between SHR and WKY rats. A Cluster heatmap of the top 20 up- and down-regulated DEGs in the left ventricle, AG and SCG. Red represents up-regulated genes, blue represents down-regulated genes. B, C, D Ten GO enrichment terms (CC, MF and BP) of DEGs in the left ventricle (B), AG (C) and SCG (D). E Ten significantly enriched KEGG pathways of DEGs in the left ventricle, AG, and SCG between SHR and WKY rats. The size of the dots represents the number of DEGs enriched to the pathway, while the color of the dots from red to blue represents the change of Q value from small to large. The “heart” represents left ventricle. AG: adrenal gland; BP: biological process; CC: cellular component; DEGs: differentially expressed genes; GO: Gene Ontology; KEGG: Kyoto Encyclopedia of Genes and Genomes; MF: molecular function; SCG: superior cervical ganglion

Fig. 3

Network analysis and enriched KEGG pathways of hub genes of the left ventricle, AG and SCG between SHR and WKY rats. A The top 20 hub genes in the left ventricle, AG and SCG between SHR and WKY rats. The color changed from red to yellow represents the rank of degree from high to low. B The significantly enriched KEGG terms of these hub genes in the left ventricle, AG, and SCG. The size of the dots represents the number of DEGs enriched to the pathway, while the color of the dots from red to blue represents the change of Q value from small to large. C The network analysis between hub gens and enriched KEGG pathways. D The PPI network of total hub genes of left ventricle, AG and SCG after K-means clustering. The bubbles of the same color represent a cluster of co-genes. The “heart” represents left ventricle. AG: adrenal gland; DEGs: differentially expressed genes; KEGG: Kyoto Encyclopedia of Genes and Genomes; SCG: superior cervical ganglion

Fig. 4

Screening for the overlapping genes of DEGs of the left ventricle, AG and SCG. A A Venn diagram of DEGs (upregulated and downregulated) of left ventricle, AG and SCG. Venn diagram (top): This diagram illustrates the overlap of upregulated and downregulated DEGs among the three organs (e.g., “HeartUp” represents the upregulated DEGs in the left ventricular). The color indicates the corresponding DEG list. The numbers inside the diagram show the count of overlapping DEGs at each intersection. Bar chart (middle): A bar chart of DEGs in different lists. The horizontal axis shows the list names, and the vertical axis represents the number of DEGs in each list. Bottom: The numbers below the chart (1, 2, 3) correspond to the number of organs, while the other numbers (1961, 230, 63) represent the number of DEGs specific to one organ or shared by two or three organs. B Cluster heatmap of the overlapping genes in the left ventricle, AG, and SCG between SHR and WKY rats. Red represents up-regulated genes, blue represents down-regulated genes. C KEGG pathway enrichment analysis of the overlapping DEGs in the left ventricle, AG, and SCG between SHR and WKY rats. The size of the dots represents the number of DEGs enriched to the pathway, while the color of the dots from red to blue represents the change of Q value from small to large. D The PPI network of total hub genes of left ventricle, AG and SCG after K-means clustering. The bubbles of the same color represent a cluster of co-genes. The “heart” represents left ventricle. AG: adrenal gland; DEGs: differentially expressed genes; KEGG: Kyoto Encyclopedia of Genes and Genomes; SCG: superior cervical ganglion

Fig. 5

Gene expression levels of overlapping DEGs of the left ventricle, AG and SCG between SHR and WKY rats. RT-qPCR analysis of overlapping genes mRNA expression in the left ventricle (A1 and A2), AG (B1 and B2) and SCG (C1 and C2) organs. The data in A1, B1 and C1 are expressed as mean ± SD, while the remaining data are presented as median and interquartile range. The “heart” represents left ventricle. AG: adrenal gland; DEGs: differentially expressed genes; SCG: superior cervical ganglion. n = 4, ****P < 0.001; ***P < 0.005; **P < 0.01; *P < 0.05; ns: not significant