Effects of antagomir-22-3p treatment on skeletal muscle growth in intrauterine growth-restricted lambs

Authors: DUCKETT, SUSAN - Clemson University; GREENE, MASLYN - Clemson University; UDOKA, ALIUTE - Clemson University; POWELL, RHONDA - Clemson University; BRUCE, TERRI - Clemson University; Klotz, James

Submitted to: Frontiers in Molecular Biosciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2025
Publication Date: 5/16/2025
Citation: Duckett, S.K., Greene, M.A., Udoka, A.N., Powell, R.R., Bruce, T.F., Klotz, J.L. 2025. Effects of antagomir-22-3p treatment on skeletal muscle growth in intrauterine growth-restricted lambs. Frontiers in Molecular Biosciences. 12. Article 1547182. https://doi.org/10.3389/fmolb.2025.1547182.
DOI: https://doi.org/10.3389/fmolb.2025.1547182

Interpretive Summary: Muscle growth is an important aspect in many food animal production systems. Ewes that are underfed during pregnancy can produce growth-restricted lambs that are not only smaller at birth, but also exhibit hindered growth as they continue to grow into adulthood. The objective of this experiment was to evaluate an injectable technology that has the potential to enhance postnatal muscle growth in control and nutrient restricted lambs. The injectable treatment did result in a shift in muscle fiber type in the nutrient restricted treatment group, and at slaughter the muscle weights and lamb body weights did not differ across treatment groups. This suggests a mitigation of lasting impact of nutrient restriction encountered during pregnancy. Future work will evaluate this technology in longer term studies. This current application only lasted 14 days. The finding of this research will be of most interest to other researchers looking to improve meat animal productivity.

Technical Abstract: MicroRNAs (miRNA) are involved in regulating gene expression and muscle development. Previous research identified miR-22-3p as differentially regulated during muscle hypertrophy and in vitro experiments found that antagomir-22-3p enhanced satellite cell proliferation. The objective of this study was to test in vivo vascular injection of antagomir-22-3p in lateral saphenous vein on miRNA and HDAC family mRNA expression in intrauterine growth restricted (IUGR) lambs. Pregnant ewes (n = 18) with twins were either fed at 100% of NRC (CON) or nutrient restricted (60% NRC; NR) from gestational d 85 to parturition. On d 12 of age, NR lambs (n = 8) were randomly selected and given a systemic injection of antagomir-22-3p in the lateral saphenous vein of the right leg (MIR-NR). CON lambs (n = 8) were also randomly selected and given a sham injection of PBS in the lateral saphenous vein of the right leg (SHAM-CON). Blood samples were collected from each lamb weekly to monitor circulating miR-22-3p expression. Muscle samples were removed for miR-22-3p and mRNA expression of potential miRNA targets. Cell-free circulating miR-22-3p expression was downregulated (P < 0.05) for MIR-NR compared to SHAM-CON on d 14 after injection and tended (P = 0.08) to be down-regulated in MIR-NR compared to SHAM-CON 21 d after injection. Lamb body weight and muscle weights at harvest were similar between MIR-NR and SHAM-CON treatments. In heart and semimembranosus (SM) muscles, expression of miR-22-3p was down-regulated (P < 0.05) in MIR-NR compared to SHAM-CON. In the gastrocnemius and semitendinosus muscle, miR-22-3p expression was unchanged (P > 0.05). The number of type I and IIa muscle fibers were greater (P < 0.05) for MIR-NR than SHAM-CON. The number of type IIx fibers did not differ (P > 0.05). MIR-NR treatment appears to shift muscle fibers towards more oxidative metabolism. The systemic injection of antagomir-22-3p down-regulated miR-22-3p expression in circulation and in muscle tissues, which altered expression of HDAC/SIRT genes involved in muscle fiber type conversion and hypertrophy.