La vitamine D au secours du traumatisme médullaire: Un espoir à confirmer

In 2014, a phase II randomised, double blind clinical trial assessing the efficacy of cholecalciferol (vitamin D₃) in patients with a cervical trauma will be set up. This trial stems from previous studies showing that vitamin D supplementation improves functional recovery in rat models of peripheral or central nerve injury. In a first series of experiments, we used a rat model of peripheral nerve trauma to demonstrate the therapeutic efficiency of vitamin D. We first demonstrated that ergocalciferol (vitamin D₂) increases the number and the diameter of newly formed axons and improves the response of metabosensitive fibers from tibialis muscle, in a model of transected peroneal nerve. Then, we compared vitamin D₂ and vitamin D₃ and observed that the latter is more efficient. At the dose of 500 IU/kg/day, vitamin D₃ induces a dramatic functional recovery. We also demonstrated that vitamin D₃ increases the number of preserved or newly formed axons in the proximal end, the mean axon diameter in the distal end, neurite myelination in both the distal and proximal ends as well as the expression of genes involved in axogenesis and myelination. In parallel, we assessed the therapeutic role of vitamin D on the central nervous system. In a first study, using a rat model of spinal cord compression at the T10 thoracic level, we delivered vitamin D₃ (cholecalciferol) orally at the dose of 50 IU/kg/day or 200 IU/kg/day. When compared to control animals, vitamin D-treated rats displayed, three months after injury, a significant improvement of ventilatory frequency and a reduction of H reflex indicating functional improvements at three months post-injury. In a second study, we used a rat model of cervical hemisection (C2) with a higher dose of oral vitamin D₃ (500 IU/kg/day) delivered weekly, during 12 weeks. We observed an improved locomotor recovery, a reduced spasticity and a significantly higher rate of axons crossing the lesion site in treated animals. However, it must be pointed out that the functional improvement is reduced when vitamin D is provided one week after the trauma.