Identification of a conserved set of upregulated genes in mouse skeletal muscle hypertrophy and regrowth

Abstract

The purpose of this study was to compare the gene expression profile of mouse skeletal muscle undergoing two forms of growth (hypertrophy and regrowth) with the goal of identifying a conserved set of differentially expressed genes. Expression profiling by microarray was performed on the plantaris muscle subjected to 1, 3, 5, 7, 10, and 14 days of hypertrophy or regrowth following 2 wk of hind-limb suspension. We identified 97 differentially expressed genes (≥2-fold increase or ≥50% decrease compared with control muscle) that were conserved during the two forms of muscle growth. The vast majority (∼90%) of the differentially expressed genes was upregulated and occurred at a single time point (64 out of 86 genes), which most often was on the first day of the time course. Microarray analysis from the conserved upregulated genes showed a set of genes related to contractile apparatus and stress response at day 1, including three genes involved in mechanotransduction and four genes encoding heat shock proteins. Our analysis further identified three cell cycle-related genes at day and several genes associated with extracellular matrix (ECM) at both days 3 and 10. In conclusion, we have identified a core set of genes commonly upregulated in two forms of muscle growth that could play a role in the maintenance of sarcomere stability, ECM remodeling, cell proliferation, fast-to-slow fiber type transition, and the regulation of skeletal muscle growth. These findings suggest conserved regulatory mechanisms involved in the adaptation of skeletal muscle to increased mechanical loading.

Keywords: extracellular matrix; hind-limb suspension; mechanotransduction; stress response; transcriptome.

Fig. 1.

Design of the experiments hypertrophy induced by synergist ablation (A) and regrowth following muscle atrophy (B).

Fig. 2.

Plantaris muscle mass (A) and total RNA concentration (B) during hypertrophy and regrowth following muscle atrophy. All results are expressed as the means ± SE. *Significantly different from day 0 during hypertrophy. #Significantly different from day 0 during regrowth.

Fig. 3.

Number of genes differentially expressed during hypertrophy (A) and regrowth (B) and number of conserved genes differentially expressed during hypertrophy and regrowth (C). The genes were initially selected by Partek Genomics Suite from a 2-fold increase or a 50% decrease in gene expression between 1) the overloaded muscle and nonoverloaded muscle (hypertrophy) and 2) the reloaded muscle and 14-day unloaded muscle by hind-limb suspension (regrowth). These genes were then uploaded in Ingenuity Pathway Analysis software to identify from the mapped genes 1) the number of upregulated and downregulated during hypertrophy (A) and regrowth (B) and 2) the number of genes commonly upregulated and downregulated during hypertrophy and regrowth (C).

Fig. 4.

Analysis by qPCR of the expression of ankyrin repeat domain 1 (Ankrd1) (A), Ankrd2 (B), and cysteine and glycine-rich protein 3 (Csrp3) (C), 3 contractile apparatus-related genes involved in mechanotransduction. The results indicate the fold change relative to day 0 (i.e., relative to the nonoverloaded muscle during hypertrophy and relative to the 14-day unloaded muscle by hind-limb suspension during regrowth). All results are expressed as the means ± SE (n = 4–6 per group at each time point). *Significantly different from day 0 during hypertrophy. #Significantly different from day 0 during regrowth.

Fig. 5.

Analysis by qPCR of the expression of secreted phosphoprotein 1 (Spp1) (A) and periostin (Postn) (B), 2 genes associated with extracellular matrix remodeling. The results indicate the fold change relative to day 0 (i.e., relative to the nonoverloaded muscle during hypertrophy and relative to the 14-day unloaded muscle by hind-limb suspension during regrowth). All results are expressed as the means ± SE (n = 4–6 per group at each time point). *Significantly different from day 0 during hypertrophy. #Significantly different from day 0 during regrowth.

Fig. 6.

Analysis by qPCR of the expression of the cell-cycle-related gene cyclin D1 (Ccnd1). The results indicate the fold change relative to day 0 (i.e., relative to the nonoverloaded muscle during hypertrophy and relative to the 14-day unloaded muscle by hind-limb suspension during regrowth). All results are expressed as the means ± SE (n = 4–6 per group at each time point). *Significantly different from day 0 during hypertrophy. #Significantly different from day 0 during regrowth.