Analysis Of Porcine Myostatin And Its Related Factors In Various Tissues Of Pigs

Myostatin, also known as growth differentiation factor-8 (GDF-8), is a member of the transforming growth factor-P superfamily and was identified in 1997. The major role of myostatin is to suppress skeletal muscle growth and development in various animal species and humans. Because of the biological function of myostatin, it has raised the possibility of using its regulators or soluble receptor to promote muscle growth and improve the disease phenotypes in a variety of myopathies, including the muscular dystrophies and degenerative and metabolic diseases. Endogenous inhibitors of mature myostatin including follistatin, Decorin, myostatin propeptide, as well as soluble activin receptor type IIB, show the accretion in muscle mass and the proliferation in myogenic cells number. Furthermore, blocking myostatin function may be useful for slowing or preventing the development of type II diabetes and obesity.However, myostatin is not a factor specifically expressed in the skeletal muscle. Many types of animal tissues and cells have been reported to express myostatin, and its expression influences their functions to some extent. Myostatin regulates the structure and function of tendons and infuleces metabolism of adipose tissue. Myostatin has been demonstrated to be expressed in the mouse mammary gland. In addition to the tendons and mammary gland, myostatin is also expressed in other animal tissues, such as the porcine anterior pituitary gland and rat uterus. Therefore, myostatin expression has a broad tissue distribution in pigs.In the present study, we assessed the myostatin, follistatin, decorin and activin receptor type IIB (ActRIIB) mRNA level in the skeletal muscle, adipose tissue, heart muscle, liver, spleen, lung and kidney of the healthy Large Whige pigs at 6-month of age and cultured porcine fibroblasts. And we also analysed the factors protein expression and presence in the various tissues of these pigs. Real-time PCR and western blot analysis demonstrated that myostatin, follistatin, decorin and ActRIIB mRNA and protein were expressed in all of the tissues detected. Although myostatin mRNA level was significantly higher in the skeletal muscle than in liver, spleen, lung, kidney, adipose, heart muscle and cultured fibroblasts, its protein was the contrary. Immunohistochemical analysis further demonstrated the presence of myostatin, follistatin and decorin in the skeletal muscle, adipose tissue, heart muscle, liver, spleen, lung and kidney of pigs. Furthermore, we studied the myostatin, follistatin, decorin and ActRIIB mRNA and protein in various tissues of the heterozygous myostatin pigs. Although myostatin mRNA was down-regulated, its protein amounts was up-regulated along with the increase of follistatin and decorin proteins expression, and Smad2/3 and P38 signal pathway are induced in the detected tissues of the heterozygous myostatin pigs. Otherwise, we transfected the human hepatic satellite cells that were over-expressing myostatin, and show that myostatin over-expressed cell had no effect on follistatin, decorin and ActRIIB mRNA and protein, although myostatin mRNA and protein was significantly higher in the over-expressed cell than in the contral.These results clearly show that myostatin is a factor broadly expressed in the internal oragans and muscles of pigs. And myasatin, follistatin, decorin and ActRIIB were closely interrelated, interacted with each other, and had a similar protein expression pattern, and its interacted place was the extracellular matrix. Myostatin also may play important roles in regulating the energy metabolism and fibrosis of tissues of pigs.