Hypoxia regulated expression of erythropoietin in cultured myoblasts and myotubes (1102.35)

abstract

Erythropoietin (EPO) is responsible for supporting the growth and development of red blood cells. EPO is produced mainly by the kidney and its expression is regulated by hypoxia. Several studies have assessed the ability of skeletal muscle to produce EPO, using whole muscle biopsies, and have observed conflicting results. Here, cell culture, RT‐PCR, and flow cytometry were used. The objective was to determine if myoblasts and myotubes were capable of expressing EPO, how its expression might be regulated, and if skeletal muscle was capable of supporting erythropoiesis in vitro. qPCR analysis demonstrated positive expression of EPO in myoblasts and myotubes. EPO expression was not modulated by physiological variables common to working muscle such as mechanical stimulation, pH, or temperature. Hypoxia, however, increased EPO expression in myoblasts by 2.2 fold (p < 0.05) and myotubes by 1.5 fold (p < 0.05). When myoblasts were conditioned with hypoxia, media taken from them was able to support erythropoiesis in bone marrow cultures. 72 hours after treatment with hypoxic myoblast conditioned media, Ter‐119 positive cells in bone marrow culture were increased by 20% (p < 0.05). These results suggest that both myoblasts and myotubes are capable of expressing EPO and do so in a hypoxia dependent manner. As well, these results lend support to studies that have observed increases in circulating levels of EPO following endurance exercise interventions, where skeletal muscle oxygen saturation is known to drop to hypoxic levels.