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

Research Overview

• This study investigates how manipulating the levels of Insulin-like Growth Factor 1 (IGF1) affects the growth and movement abilities of horse skeletal muscle cells.
• The research reveals that IGF1 promotes muscle cell proliferation and migration by activating a specific cellular signaling pathway (PI3K/Akt), which may help explain mechanisms behind equine athletic performance and muscle repair.

Background and Importance

• Skeletal muscle is essential for movement and directly influences a horse’s endurance and speed.
• The ability of muscle cells to proliferate (multiply) and migrate (move) is foundational for muscle function and performance.
• Previous studies showed that IGF1 expression increases in horse muscle after racing and is linked to the PI3K-Akt pathway, a key signaling route for cell survival and growth.
• The precise way IGF1 controls horse muscle cell behavior was not well understood prior to this study.

Study Design and Methods

• Primary equine skeletal muscle cells were cultured and used as an experimental model.
• An IGF1 overexpression plasmid was constructed to artificially increase IGF1 levels within the cells.
• Small interfering RNAs (siRNAs) were screened and used to knock down (reduce) IGF1 gene expression.
• Gene expression changes were measured using RT-qPCR (quantitative reverse transcription PCR) to detect RNA levels and Western Blot to measure protein levels, particularly focusing on total and phosphorylated Akt protein.
• Cell proliferation was assessed via Cell Counting Kit-8 (CCK-8) assays, measuring cell viability and growth.
• Cell migration ability was measured using scratch assays, which mimic wound healing by creating a “scratch” and observing how quickly cells move to fill the gap.

Key Findings

• IGF1 overexpression significantly enhanced muscle cell proliferation viability with extremely strong statistical significance (p < 0.0001).
• IGF1 also significantly increased cell migration rate (p < 0.0001), improving the cells' wound-healing capacities.
• Conversely, silencing IGF1 via siRNA markedly inhibited these proliferation and migration abilities, indicating its pivotal role.
• Mechanistically, IGF1 overexpression led to increased phosphorylation of Akt, a key indicator of activation of the PI3K/Akt pathway.
• The biological effects of IGF1 on muscle cells were closely associated with activation of this signaling pathway.

Conclusions and Implications

• This is the first study to show at the cellular level that IGF1 is a critical regulator of equine skeletal muscle cell proliferation and migration.
• IGF1’s enhancement of muscle cell growth and movement capabilities operates through the key PI3K/Akt signaling cascade.
• Understanding this molecular mechanism advances knowledge of how athletic performance traits develop in horses after exercise or injury.
• These findings suggest IGF1 and the PI3K/Akt pathway could be promising targets for improving horse muscle recovery, performance, and breeding strategies aimed at sport horses.
• Potential applications include molecular breeding for better athletic traits and new treatments or therapies to accelerate muscle injury repair.