Gelatinase MMP Expression Is Correlated with Muscle Fiber Growth in Maiwa Yak Gluteus Maximus

Yak (Bos grunniens) is the only large mammal species in the Qinghai-Tibet Plateau. The most of the studies in yak remain confined for the main contributor of meat, which requires a good understanding of muscle growth. Matrix metalloproteinases-2 (MMP-2) and MMP-9 are widely expressed in mammal tissues they mainly degrade collagen in the extracellular matrix for muscle development. However, the influence of MMPs on yak muscle remains unclear. Hence, we assessed the expression of MMP-2, MMP-9, and related factors with ages in Maiwa yak for study the correlation between MMPs expression and yak muscle growth. The mRNA expression of MMP-2, MMP-9, MMP-14, and collagen III increased with age, except collagen I by quantitative real-time PCR. Moreover, muscle fiber diameter increased with age, whereas the density decreased, which showed that fiber grew thicker with age using hematoxylin-eosin staining. Interestingly, MMP and collagen expression significantly decreased with age using western blotting. Pearson correlation method showed that both mRNA and protein expression of MMP-14 and collagen were strongly correlated with muscle fiber growth, but MMP-2 protein and MMP-9 mRNA expression were moderately correlated with muscle fiber growth. Overall, the expression of MMPs and collagen significantly changed with age, which means that MMPs and their function related genes could correlate with Maiwa yak muscle fiber growth.