FAK-mTOR Pathway Mediated Different Proliferation, Migration and Differentiation Abilities of Satellite Cells in Lantang and Landrace Piglets

Compared with Landrace pig, Lantang is an indigenous Chinese pig breed that possesses excellent meat quality but low rates of lean meat deposition. The different muscle characteristics may be related to the different features of skeletal muscle satellite cells (SCs). Therefore, three experiments were conducted to explore SC proliferation, migration and differentiation abilities in Lantang and Landrace piglets, as well as focal adhesion kinase (FAK) and mammalian target of rapamycin (mTOR) pathways to preliminary explore the molecular mechanisms. In experiment 1, the different proliferation capacity of these SCs was determined. Cell count assay showed that there was a greater (P<0.05) number of Lantang SCs compared with Landrace at 72 h. Higher percentage of Lantang SCs in S phase and G2/M phases were found (P<0.05), while G0/G1 phase was lower (P<0.05) in comparison with the Landrace. The mRNA abundances of myogenic differentiation antigen, myogenic factor 5, myogenin, and paired box 7 in SCs from Lantang were higher (P<0.05), while those of myostatin, sekelsky mothers against dpp family member 3, protein kinase B (Akt), tuberous sclerosis complex 1, mTOR, ribosomal protein S6 kinase 1 (S6K1), and ribosomal protein S6 (S6) were lower than those in Landrace SCs (P<0.05). In experiment 2, for the migration study, we found that Lantang SCs had greater ability of migration and adhesion (P<0.05) than Landrace SCs. Meanwhile, the levels of p-FAK and p-paxillin were higher (P<0.05) in Lantang SCs than Landrace SCs at 24 h after migration. Similarly, treatment with the FAK inhibitor PF-573228 restrained Lantang SCs migration (P<0.05), decreased p-paxillin and p-Akt levels (P<0.05). In experiment 3, for the differentiation study, the creatine kinase activity and fusion index in Lantang SCs was higher than that in Landrace SCs at 72 h during differentiation (P<0.05). Meanwhile, the levels of differentiation markers like myogenin and myosin heavy chain I in Lantang SCs were higher compared with Landrace SCs at 72 h during differentiation (P<0.05). However, the levels of p-Akt, p-mTOR, p-S6K1, and p-S6 in Lantang SCs were lower than those in Landrace SCs (P<0.05). In conclusion, these findings showed that SCs in Lantang piglet had higher proliferation, migration and differentiation abilities than those in Landrace piglet. It is interesting for us to find that mTOR pathway was positive to cell proliferation, while it was negative to differentiation; nevertheless, FAK pathway plays a key role in the regulation of SCs migration.