Differential expression of extracellular matrix and integrin genes in the longissimus thoracis between bulls and steers and their association with intramuscular fat contents

This study was performed to compare expression of genes for extracellular matrix (ECM) components, ECM degrading factors, and integrin subunits in the longissimus thoracis (LT) between bulls and steers. Steers had lower (P < 0.05) ECM component collagen type 1 alpha 1 and collagen type 3 alpha 1 mRNA levels than did bulls, but they had higher (P < 0.05) thrombospondin 1 mRNA and protein levels. Steers had higher (P < 0.01) matrix metalloproteinase (MMP) 9 mRNA levels than did bulls. Steers had higher (P < 0.05) integrin alpha 5 mRNA levels but lower (P < 0.05) integrin beta 6 mRNA and protein levels; however, expression levels of several other integrin subunits were not different between steers and bulls. MMP9 mRNA levels were positively correlated (P < 0.05) with intramuscular fat content in bull group. In conclusion, these results demonstrate that castration has moderate effects on expression of ECM components, ECM degrading factors, and integrin subunit genes in the LT.