Sex and Metabolic Fuel Preferences Impact Proliferative Capacity of Human Muscle Progenitor Cells

Abstract

IntroductionSkeletal muscle (SkM) stem cells, satellite cells (SC), are essential for muscle maintenance as well as repair and regeneration post injury. Successful SkM regeneration requires a well‐orchestrated series of events from activation of the quiescent SC, to proliferation [muscle progenitor cells (MPC)], differentiation, and formation of multinucleated cells. During the regenerative process, macronutrients provide energy and substrates for metabolic processes and cellular structures. Defects in macronutrient metabolism and metabolic inflexibility underlie metabolic disease and likely impact the regenerative process. The “phenotype” of human macronutrient utilization and sex specific differences throughout the initial stages of the regenerative process are largely unknown.ObjectiveThe objective was to characterize metabolic gene expression and signaling throughout human MPC proliferation and identify sex differences that might impact successful regeneration.MethodsPrimary human SC were obtained from the vastus lateralis SkM of healthy young males (male‐MPC, n=6) and young females (female‐MPC, n=6) and cultured. A high‐throughput imaging cytometer was used to determine the confluency, nuclei count, and % of dead cells every 24 hours throughout proliferation. Saturation density was defined as the # of nuclei at proliferation plateau/cm2. Real‐time qPCR was used to measure mRNA abundance of select genes associated with macronutrient uptake and metabolism, mitochondrial biogenesis, inflammation, and stress at the first and third day out of lag. The first day out of lag was defined as the first increase in % confluency of ≥ 5%.ResultsPercent confluency throughout proliferation and saturation density were lower in female‐MPC when compared to male‐MPC. Female‐MPC also had a higher % of dead cells throughout proliferation. PGC1‐α, CD36, and NFkB mRNA levels were higher and IL6, CAT1, and CAT2 mRNA levels were lower in female‐MPC compared to male‐MPC. PGC1‐α and CD36 mRNA levels increased over time while CAT1 mRNA levels decreased over time in both female‐MPC and male‐MPC. No differences in SLC7A5, GLUT1, or GLUT4 mRNA levels were observed between sexes at either time‐point.ConclusionsFemale MPCs proliferated at a slower rate, reached a lower saturation density, and experienced elevated cell death throughout proliferation when compared to males. These differences in markers of proliferative capacity were accompanied by up‐regulation of metabolic genes, CD36 and PGC1‐α. This suggests that female cells may rely more heavily on fatty acids and mitochondrial function during proliferation, which may impair female MPC proliferative capacity.Support or Funding InformationCornell University