Effects of hydroxyurea on skeletal muscle energetics and force production in a sickle cell disease murine model.

Hydroxyurea (HU) is commonly used as a treatment for patients with sickle cell disease (SCD) to enhance fetal hemoglobin production. This increased production is expected to reduce anemia (which depresses oxygen transport) and abnormal Hb content alleviating clinical symptoms such as vaso-occlusive crisis and acute chest syndrome. The effects of HU on skeletal muscle bioenergetics in vivo are still unknown. Due to the beneficial effects of HU upon oxygen delivery, improved skeletal muscle energetics and function in response to a HU treatment have been hypothesized. Muscle energetics and function were analyzed during a standardized rest-exercise-recovery protocol, using P-magnetic resonance spectroscopy in Townes SCD mice. Measurements were performed in three groups of mice: one group of 2-mo-old mice (SCD, = 8), another one of 4-mo-old mice (SCD, = 8), and a last group of 4-mo-old mice that have been treated from 2 mo of age with HU at 50 mg/kg/day (SCD, = 8). As compared with SCD mice, SCD mice were heavier and displayed a lower acidosis. As lower specific forces were developed by SCD compared with SCD, greater force-normalized phosphocreatine consumption and oxidative and nonoxidative costs of contraction were also reported. HU-treated mice (SCD) displayed a significantly higher specific force production as compared with untreated mice (SCD), whereas muscle energetics was unchanged. Overall, our results support a beneficial effect of HU on muscle function. Our results highlighted that force production decreases between 2 and 4 mo of age in SCD mice thereby indicating a decrease of muscle function during this period. Of interest, HU treatment seemed to blunt the observed age effect given that SCD mice displayed a higher specific force production as compared with SCD mice. In that respect, HU treatment would help to maintain a higher capacity of force production during aging in SCD.