Roles of cholesterol in the proliferation and differentiation of bovine myoblasts

The objective of this study was to assess the potential role of extracellular, cytosolic, and membrane cholesterol in the proliferation and differentiation of bovine myoblasts. In the first experiment, myoblasts isolated from Angus or Angus crossbred steers were cultured with 2% lipoprotein deficient fetal calf serum (LPDS) or normal fetal calf serum. Culturing with LPDS did not alter the cytosolic or membrane cholesterol content, or myoblast differentiation, but inhibited myoblast proliferation, compared to culturing with normal fetal calf serum. In the second experiment, myoblasts were cultured with or without lovastatin, a selective inhibitor of cholesterol synthesis. Culturing with 5 μM lovastatin did not affect medium concentration of cholesterol, but reduced cytosolic and membrane cholesterol contents, compared to culturing with vehicle control. Culturing with 5 μM lovastatin inhibited both myoblast proliferation and differentiation. In the third experiment, myoblasts were cultured with or without methyl-βcyclodextrin (MβCD), a chemical that depletes cholesterol from cell membranes. Treating myoblasts with 10 mM MβCD for 30 minutes reduced membrane and cytosolic cholesterol contents while increasing medium cholesterol concentration. Treating with MβCD inhibited both myoblast proliferation and differentiation compared to treating with vehicle control. Overall, this study showed that lovastatin- or MβCD-induced reductions in cytosolic and membrane cholesterol contents were associated with reduced proliferation and differentiation in bovine myoblasts. These associations suggest that cytosolic cholesterol, membrane cholesterol, or both may play a role in bovine myoblast proliferation and differentiation.