Human Platelet Lysate Supports Mouse Skeletal Myoblast Growth but Suppresses Cell Fusion on Nanogrooves.

The fusion of skeletal myoblasts is a critical step in myotube formation and muscle maturation. Previously, we demonstrated that nanogrooves improved myoblast fusion via end-to-end fusion, which in turn generated parallel myotubes. However, the effect of serum components on the end-to-end fusion mechanism is unclear. In the current study, the synergistic effect of nanogrooves and human platelet lysate (hPL) on the growth and fusion of skeletal myoblasts was studied. Four types of nanogrooves (400 and 800 nm width; 100 and 400 nm depth) were used. Cell spreading, growth, and differentiation were screened on these nanogrooves in media formulated with hPL or fetal bovine serum (FBS), along with the flat substrate as a control group. The results showed that the deeper nanogrooves induced better alignment of myoblasts. hPL-adapted skeletal myoblasts (i.e., myoblasts@hPL) showed a smaller cell size with a more elongated morphology than myoblasts@FBS. During cell growth, the expression of myogenic genes (Myf5, MyoD, and MyoG) in myoblasts@hPL was lower than in myoblasts@FBS. During cell differentiation, myoblasts@hPL also expressed a lower level of myogenic and myosin heavy chain (MHC) genes. MHC-positive myoblasts@hPL without myotubes were found on all surfaces. Myomaker, an essential myoblast fusion gene, was upregulated during growth but downregulated during differentiation in myoblasts@hPL. Fibronectin-coated surfaces facilitate cell spreading and growth but still cannot support myoblast@hPL fusion. The results implied that hPL either lacks promotor factors or contains inhibitors on mouse skeletal myoblast fusion. This study reveals the effect of biophysical and biochemical cues on myoblast fusion and their potential for muscle tissue engineering.