Effects of IGF1 Knockdown and Overexpression on the Phenotype and Function of Equine Primary Skeletal Muscle Cells

Skeletal muscle serves as the direct executor of movement, and the proliferation and migration capacities of its constituent cells represent the key physiological foundation determining equine endurance and speed. Previous whole-transcriptome analysis has shown that Insulin-like Growth Factor 1 (IGF1) is significantly upregulated in Yili horses following racing and is involved in the PI3K-Akt signaling pathway; however, its specific regulatory mechanism in equine skeletal muscle cells remains unclear. This study utilized primary equine skeletal muscle cells as a model. By constructing an IGF1 overexpression plasmid and screening efficient siRNA interference sequences, we employed RT-qPCR and Western Blot techniques to verify gene expression and the activation level of the PI3K/Akt pathway. Cell Counting Kit-8 (CCK-8) assays were used to detect cell proliferation viability, and cell scratch assays were conducted to evaluate migration capacity, aiming to clarify the regulatory effect of IGF1 on the phenotype and function of equine skeletal muscle cells. Functional experiments demonstrated that IGF1 overexpression significantly promoted the proliferation viability (p < 0.0001) and migration rate (p < 0.0001) of equine skeletal muscle cells, whereas knockdown of IGF1 significantly inhibited these cellular capabilities. Mechanistic studies revealed that IGF1 overexpression significantly increased Akt phosphorylation. Notably, IGF1 exerted its biological functions in conjunction with the activation of the PI3K/Akt signaling pathway. In conclusion, IGF1 enhances cell proliferation and wound-healing capacity of primary equine skeletal muscle cells, which correlates with its ability to activate the PI3K/Akt signaling pathway. This study is the first to reveal the critical role of IGF1 in equine skeletal muscle biology at the cellular level, providing experimental evidence for a deeper understanding of the molecular mechanisms underlying the formation of athletic performance in Yili horses. It also offers novel potential targets for the molecular breeding of sport horses and interventions for injury repair.