Fisiopatologia de lesión medular

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75Vet. Méx., 36 (1) 2005Fisiopatología de la lesión medular. Revisión de literaturaPathophysiology of spinal cord injury. A reviewSara Caballero Chacón* Manuel Nieto-Sampedro**Recibido el 17 de febrero de 2004 y aceptado el 18 de agosto de 2004.*Departamento de Fisiología y Farmacología,Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónomade México, México, D. F. Tel. 5622 5908 y 5622 5980; e-mail: saracachas@hotmail.com**Departamento de Plasticidad Neural, Instituto Ramón y Cajal de Neurobiología, Av. Dr. Arce 37, CP 28002, Madrid, España.AbstractHere is shown the description of the physiological phenomena that occurs in spinal cord after traumatic injury.Also are reviewed the molecular processes that are present in the developed of primary and secondary neuronal death. Likewise, cellular and molecular processes that inhibit axonal growth and regeneration of central nervous system are reviewed. The finality ofthis review is to approach the DVM to knowledge of the problem of spinal cord injury in order toattack it from its molecular bases and takeadvantage of the information that basic researchcan offer in our own benefit.Key words: SPINAL CORD INJURY, PRIMARY NEURONAL DEATH, SECONDARY NEU-RONAL DEATH, NERVE REGENERATION, ISCHEMIA, CELL TRANSPLANTS, REACTIVEASTROCYTES.ResumenSe presenta la descripción de los efectos fisiopatólogicos que ocurren en la lesión medular por trauma y que inciden en los procesos moleculares que desencadenan muerteneuronal primaria y secundaria. Se hace énfasis en los mecanismos moleculares y celulares que impiden la regeneración axonal en el sistema nervioso central. La finalidad de esta revisión es acercar al médico veterinario al conocimiento a fondo sobre las lesiones medulares, para atenderlasdesde sus bases moleculares y aprovechar la información que brinda la investigación básica.Palabras clave:LESIÓN MEDULAR, MUERTE NEURONAL PRIMARIA, MUERTENEURONAL SECUNDARIA, REGENERACIÓN NERVIOSA, ISQUEMIA, TRASPLANTESCELULARES, ASTROCITOS REACTIVOS.Artículos de revisión
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76IntroductionRecently the pathophysiologic study of spinalcord injury has been increased. This pathology,mainly traumatic, is very importantbecausethe central nervous system, unlike the peripheral ner-vous system, shows irreversible changes that obstruct nerve regeneration.When the peripheral nervous system (i.e. sciatic nerve, radial nerve, lumbar nerves) is injured, nerveregeneration is possible because the trophic factors produced by Schwann cells are up regulated. Those cells also improve axonal growth because ensheat and protect axonproximal stump, promoting growth andthe establishment of new connections in the targetthat recovers sensitivity and functionality.1 In the central nervous system the process is not likein the peripheral, because the primary injury (which is located in the epicenter) destroys neuronal bodies. Damage induces an ischemic process, inflammationand primary neuronal death due the presence of oxygen freeradicals. Later, the lesion is extended andsecondary neuronal cell death occurres, killing more neurons than the primary neuronal death.2There are many factors that obstruct the regeneration of the central nervous system; substanceslike proteoglycans and myelin derivatives are true barriers and an impediment of axonal growth.3,4In arealistic view, the study of these obstacles shows that thedamage in the central nervous system is much more complex than putting in contact two electriccables as before was believed in a simplistic way. Inthis review are described the events that ocurr during the lesion, but they do not occurr in a systematic way,some of they are present at the same or different times depending on the time or size of the injury, for an easycomprehension they are described...