Skeletal muscle intrinsic functional properties are preserved in a model of erythropoietin deficient mice exposed to hypoxia

Abstract

Erythropoietin (Epo)-induced polycythemia is the main factor of adaptation to hypoxia. In this study, we analysed the effects of Epo deficiency on intrinsic functional properties of slow and fast twitch muscles in a model of erythropoietin deficient mice (Epo-TAg(h)) exposed to hypoxia. We hypothesised that Epo deficiency would be deleterious for skeletal muscle structure and phenotype, which could change its functional properties and alters the adaptive response to ambient hypoxia. Wild-type (WT) and Epo-TAg(h) mice were left in hypobaric chamber at 420 mm Hg pressure for 14 days. Soleus (SOL) and extensor digitorum longus (EDL) were analysed in vitro by mechanical measurements, immunohistological and biochemical analyses. The results were compared to those obtained in corresponding muscles of age-matched normoxic groups. Our data did not show any difference between the groups whatever the Epo deficiency and/or hypoxic conditions for twitch force, tetanic force, fatigue, typology and myosin heavy chain composition. Normoxic Epo-TAg(h) mice exhibit improved capillary-to-fibre ratio compared to WT mice in both SOL and EDL whereas no angiogenic effects of hypoxia or combined Epo-deficiency/hypoxia were observed. These results suggest that skeletal muscles possess a great capacity of adaptation to Epo deficiency. Then Epo deficiency is not a sufficient factor to modify intrinsic functional properties of skeletal muscles.