Date of Award
Master of Science (MS)
Animal and Veterinary Sciences
Dr. Susan Duckett
Dr. Jeryl Jones
Dr. Ahmed Ali
Texel sheep are known for their double-muscling phenotype and extraordinary meat production (Miar et al., 2014). Satellite cells are essential for this desired muscle growth. MicroRNAs can silence target genes by binding to the target messenger RNA (mRNA) (Horak et alk., 2016). Antagomirs are miRNA inhibitors and are used for loss of function studies. MiR-22-3p is known for inhibiting skeletal muscle growth and directly targets HDAC4, TGFBR1, PAX7 mRNA expression. Computed Tomography (CT) imaging is now growing in popularity in the animal science field to record changes in muscle characteristics.
Materials and Methods
Texel x Suffolk lambs (n=4) were given an antagomiR-22-3p intramuscular injection for 3 consecutive days in the longissimus muscle compared to sham. The lambs were CT scanned pre-treatment and then for 4 weeks. Samples were obtained from LM and used to isolate cells, measure miRNA and mRNA expression, and proximate composition. A standardized CT image analysis protocol was used to determine the transverse sectional area and mean density (Hounsfield units, HU) for the antagomiR (left) and sham (right) sides of the LM.
AntagomiR-22-3p treatment down-regulated miR-22-3p compared to sham. HDAC4 and TGFBR1, both mRNA targets of miR-22-3p, were up-regulated compared to the sham. PAX7 did not differ in this study between sham and trt sides (p=0.9094). For the CT imaging, the ribeye area (REA) size was not found to be statistically significant between miR and sham. In the CT measurements for intra-observer repeatability, there were no Coefficient of Variation (CV) values outside the “good” range. For inter-observer repeatability, 80% of the observers did not statistically differ from each other for the left area, 73.34% for the left corrected density, 66.67% for the right area, and 73.34% for the right corrected density measurement.
AntagomiR-22-3p seemed to silence miR-22-3p, and the effect appeared to be the greatest at two weeks instead of four weeks. Muscle growth was not shown over time using the CT images, but the methodology is deemed repeatable.
Brewer, Anna, "Effects of AntagomiR-22-3p on Muscle Size in Older Lambs using Computed Tomography Imaging" (2023). All Theses. 4111.
Available for download on Saturday, August 31, 2024