PSI-3 Effects of a Retinoid X Receptor agonist on primary ovine satellite cells

Abstract Sheep producers are typically paid based on body weight, so understanding the mechanisms of postnatal skeletal muscle growth is vital. Satellite cells are responsible for the capacity for postnatal skeletal muscle growth. Satellite cells proliferate and then differentiate into myoblasts before fusing with existing myotubes. The retinoid X receptor (RXR) is a transcription factor that enhances myogenic differentiation 1 (MyoD) expression, which increases differentiation and fusion of myoblasts in sheep. LG 100268 is an RXR agonist, which activates the RXR. The objective of this project is to measure the effect of LG 100268 on primary ovine satellite cell (OSC) proliferation and protein synthesis rates. Primary OSC were isolated from the hind legs of 9-mo old commercial hair sheep wethers (n = 3). For proliferation, cultures were grown to approximately 70% confluency, followed by treatment with 5% fetal bovine serum (FBS) or 300 nM of LG 100268 in 5% FBS. For protein synthesis, cultures were grown to approximately 80% confluency, at which point cultures were induced to differentiate and treated 48-h later with serum free media (SFM) or 300 nM LG 100268 in SFM. Proliferation rates were measured at 24-h post-treatment, and protein synthesis rates were measured at 6-h post-treatment. Treatment with 300 nM LG 100268 increased (P = 0.004) OSC proliferation rates compared with control cultures. Preliminary protein synthesis results suggest that LG 100268 does not alter (P = 0.22) protein synthesis rates of fused OSC. However, more research is warranted to clarify the role of the RXR in sheep skeletal muscle growth.