Thèse de doctorat en Neuroscience
Sous la direction de Marc Tadié.
Soutenue en 1998
à Rouen .
Pas de résumé disponible.
Spinal cord injury is still considered as a trauma beyond the surgical treatment in the clinical field. How to overcome this obstacle is therefore a main project of clinical and research workers. Reviewing the literatures and publications concerning these studies, we developed two experimental models in attemps to promote spinal axonal regeneration and reinnervation of the denervated peripheral target after spinal cord injury. In the model of brachial plexus injury, 54 adult rats (Sprague Dawley, male, 350-400 g) and 18 adult primates (marmosets, male or female,Callithrix jacchus, 300-400 g) underwent an avulsion of right cervical spinal roots C5, C6 and C7. In the three repaired groups (15 rats and 5 monkeys in each group), an implanted nerve autograft (Group C) or collagen tube containing (Group B) or not (Group A) a nerve segment were used to bridge the cervical spinal ventral horn to the right avulsed spinal roots C6. In the control animals (9 rats and 3 monkeys), no avulsed spinal root was repaired. Nine months in rats and five months in primates following surgery, all animals were assessed by clinical, electrophysiological and histological examinations. The functional recovery of the right lesionned forelimb was well established in the repaired rats and primates. The normal EMG, positive MAP and MEP were recorded in the right denervated/reinnervated biceps of all repaired animals. HRP retrograde labelling from this biceps showed a lot of HRP-labelled neurons ipsilaterally located in the cervical spinal ventral horn near the implantation site. Histological analysis by light and electronic microscopes confirmed that numerous regenerating axons were presented in the nerve autograft, collagen tube as well as distal denervated/repaired spinal nerve roots. Moreover, many newly formed endplates were also found in the denervatedlreinnervated biceps. Statistical analysis did not show significant différence among the three repaired groups. In the control animals, no evident positive result was observed. In the model of spinal cord injury, 15 adult rats (Sprague Dawley, male, 350-400 g) and 9 adult marmosets (Callithrixjacchus, male or female, 300-400 g) suffered from a hemisection of spinal cord (T12) and section of all ipsilateral lumbar ventral roots. In the repaired animals (9 rats and 5 monkeys), an implanted nerve autograft was used to establish a tissue continuity from thoracic spinal ventral horn (T 10), acrossing the hemisection, to the denervated lumbar ventral roots L3 and L4 that were identified by electrophysiology. In the control ones (6 rats and 4 monkeys), no repair procedure was performed. Nine months later, the clinical observation showed some signs of functional reinnervation of denervated quadriceps in the repaired animals. In these animals, the MAP and MEP were recorded from this quadriceps when the cortex and nerve autograft were respectively electrostimulated. HRP retrograde labelling from the denervated/repaired lumbar ventral roots traced that the thoracic spinal motoneurons nearby the implanted nerve graft tip elongated their axons into the denervated/repaired neuronal pathway and innervated the denervated quadriceps. Histological analysis furthermore confirmed numerous regenerating axons and newly formed endplates respectively presented in this neuronal pathway and the distal muscle. No positive result was obtained from the control animals. Reviewing the results obtained in the present studies, we conclude that the spinal motoneurons can be promoted to regrow into the denervated/repaired spinal roots via an implanted collagen tube or nerve autograft, inducing functional reinnervation of the target muscles. Although the further studies are still necessary, these data suggest a possible surgical repair application for treating brachial plexus or spinal cord injury.