Desarrollo neuromuscular en la atrofia muscular espinal
BACKGROUND: Spinal muscular atrophy (SMA) is a neuromuscular disease characterized by degeneration and loss of spinal cord motor neurons leading to denervation and muscular atrophy. It is caused by defects in the Survival Motor Neuron 1 gene (SMN1) and it is classified by age of onset and motor mile...
| Autor: | |
|---|---|
| Formato: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2012 |
| País: | España |
| Recursos: | Universidad de Barcelona |
| Repositorio: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/34744 |
| Acesso em linha: | https://hdl.handle.net/2445/34744 http://hdl.handle.net/10803/97097 |
| Access Level: | acceso abierto |
| Palavra-chave: | Malalties neuromusculars Atròfia muscular Biologia del desenvolupament Medul·la espinal Neuromuscular diseases Muscular atrophy Developmental biology Spinal cord |
| id |
ES_2ff7baa6480d8b04bb4e629957eac9fb |
|---|---|
| oai_identifier_str |
oai:diposit.ub.edu:2445/34744 |
| network_acronym_str |
ES |
| network_name_str |
España |
| repository_id_str |
|
| dc.title.none.fl_str_mv |
Desarrollo neuromuscular en la atrofia muscular espinal |
| title |
Desarrollo neuromuscular en la atrofia muscular espinal |
| spellingShingle |
Desarrollo neuromuscular en la atrofia muscular espinal Martínez Hernàndez, Rebeca Malalties neuromusculars Atròfia muscular Biologia del desenvolupament Medul·la espinal Neuromuscular diseases Muscular atrophy Developmental biology Spinal cord |
| title_short |
Desarrollo neuromuscular en la atrofia muscular espinal |
| title_full |
Desarrollo neuromuscular en la atrofia muscular espinal |
| title_fullStr |
Desarrollo neuromuscular en la atrofia muscular espinal |
| title_full_unstemmed |
Desarrollo neuromuscular en la atrofia muscular espinal |
| title_sort |
Desarrollo neuromuscular en la atrofia muscular espinal |
| dc.creator.none.fl_str_mv |
Martínez Hernàndez, Rebeca |
| author |
Martínez Hernàndez, Rebeca |
| author_facet |
Martínez Hernàndez, Rebeca |
| author_role |
author |
| dc.contributor.none.fl_str_mv |
Tizzano Ferrari, Eduardo Ferrer, Isidro (Ferrer Abizanda) Universitat de Barcelona. Facultat de Medicina |
| dc.subject.none.fl_str_mv |
Malalties neuromusculars Atròfia muscular Biologia del desenvolupament Medul·la espinal Neuromuscular diseases Muscular atrophy Developmental biology Spinal cord |
| topic |
Malalties neuromusculars Atròfia muscular Biologia del desenvolupament Medul·la espinal Neuromuscular diseases Muscular atrophy Developmental biology Spinal cord |
| description |
BACKGROUND: Spinal muscular atrophy (SMA) is a neuromuscular disease characterized by degeneration and loss of spinal cord motor neurons leading to denervation and muscular atrophy. It is caused by defects in the Survival Motor Neuron 1 gene (SMN1) and it is classified by age of onset and motor milestones into three main types which strongly correlate with the copy number of its homologous gene, SMN2. SMN2 expresses markedly less full‐length protein than SMN1, provoking disease manifestations. The essential neuropathological feature in SMA is motor neuron death. Previous studies in SMA foetal samples showed early pathological changes in spinal cord suggesting that the disease is a developmental disorder. Studies in mouse SMA models support that neuromuscular junctions (NMJs) may play a significant role in the disease, although this implication has not yet been addressed in humans. AIMS AND METHODOLOGIES: To better understand the mechanisms of SMA disease, a comprehensive histologic, immunohistochemical and ultrastructural analysis of the muscle and neuromuscular junctions in prenatal and postnatal SMA samples was carried out. To further correlate neuropathological findings with early developmental manifestations of the disease, foetal motility between 11‐14 gestational weeks was recorded and analyzed by 2D ultrasound in pregnancies predicted to develop SMA. RESULTS: At 12 weeks, most SMA myotubes were smaller than controls, indicating a delay in muscle maturation. At this stage, the presence of early acetylcholine receptor (AChR) clusters in developing SMA muscles suggested that pre‐patterned and nerve‐independent AChR clustering would not be affected by the disease. However, as development proceeded in the following weeks, early degeneration of nerve terminals was present associated with a dispersion of AChRs and abnormal preterminal accumulation of vesicles. These findings pointed towards a defect in maintenance of the initial innervation in developmental SMA muscle. Furthermore, postnatal muscle of type I SMA patients showed persistence of the foetal subunit of acetylcholine receptors, suggesting a continuous delay in maturation of neuromuscular junctions. Therefore, if nerve terminals are unable to efficiently maintain functional NMJs, a dying‐back process leading to motor neuron degeneration and loss may appear, with the consequent increase in programmed cell death. Despite all these early neuropathological findings, we did not observe qualitative differences in foetal movements between unaffected and SMA prenatal cases. The synaptic defects in SMA at this stage of development, therefore, might be compensated by several mechanisms. During perinatal and postnatal periods compensation would no longer be present, resulting in the drastic SMA pathology and clinical manifestations. CONCLUSIONS: These developmental studies open new possibilities to improve our knowledge of presymptomatic SMA stages. Early therapeutic strategies should be investigated to reverse the process of denervation, maintain activity of the NMJ, and improve maturity of the motor endplates. |
| publishDate |
2012 |
| dc.date.none.fl_str_mv |
2012 |
| dc.type.none.fl_str_mv |
info:eu-repo/semantics/doctoralThesis info:eu-repo/semantics/publishedVersion |
| format |
doctoralThesis |
| status_str |
publishedVersion |
| dc.identifier.none.fl_str_mv |
https://hdl.handle.net/2445/34744 http://hdl.handle.net/10803/97097 |
| url |
https://hdl.handle.net/2445/34744 http://hdl.handle.net/10803/97097 |
| dc.language.none.fl_str_mv |
Español |
| language_invalid_str_mv |
Español |
| dc.rights.none.fl_str_mv |
(c) Martínez Hernàndez, 2012 info:eu-repo/semantics/openAccess |
| rights_invalid_str_mv |
(c) Martínez Hernàndez, 2012 |
| eu_rights_str_mv |
openAccess |
| dc.format.none.fl_str_mv |
application/pdf |
| dc.publisher.none.fl_str_mv |
Universitat de Barcelona |
| publisher.none.fl_str_mv |
Universitat de Barcelona |
| dc.source.none.fl_str_mv |
Tesis Doctorals - Facultat - Medicina reponame:Dipòsit Digital de la UB instname:Universidad de Barcelona |
| instname_str |
Universidad de Barcelona |
| reponame_str |
Dipòsit Digital de la UB |
| collection |
Dipòsit Digital de la UB |
| repository.name.fl_str_mv |
|
| repository.mail.fl_str_mv |
|
| _version_ |
1869405513257582592 |
| spelling |
Desarrollo neuromuscular en la atrofia muscular espinalMartínez Hernàndez, RebecaMalalties neuromuscularsAtròfia muscularBiologia del desenvolupamentMedul·la espinalNeuromuscular diseasesMuscular atrophyDevelopmental biologySpinal cordBACKGROUND: Spinal muscular atrophy (SMA) is a neuromuscular disease characterized by degeneration and loss of spinal cord motor neurons leading to denervation and muscular atrophy. It is caused by defects in the Survival Motor Neuron 1 gene (SMN1) and it is classified by age of onset and motor milestones into three main types which strongly correlate with the copy number of its homologous gene, SMN2. SMN2 expresses markedly less full‐length protein than SMN1, provoking disease manifestations. The essential neuropathological feature in SMA is motor neuron death. Previous studies in SMA foetal samples showed early pathological changes in spinal cord suggesting that the disease is a developmental disorder. Studies in mouse SMA models support that neuromuscular junctions (NMJs) may play a significant role in the disease, although this implication has not yet been addressed in humans. AIMS AND METHODOLOGIES: To better understand the mechanisms of SMA disease, a comprehensive histologic, immunohistochemical and ultrastructural analysis of the muscle and neuromuscular junctions in prenatal and postnatal SMA samples was carried out. To further correlate neuropathological findings with early developmental manifestations of the disease, foetal motility between 11‐14 gestational weeks was recorded and analyzed by 2D ultrasound in pregnancies predicted to develop SMA. RESULTS: At 12 weeks, most SMA myotubes were smaller than controls, indicating a delay in muscle maturation. At this stage, the presence of early acetylcholine receptor (AChR) clusters in developing SMA muscles suggested that pre‐patterned and nerve‐independent AChR clustering would not be affected by the disease. However, as development proceeded in the following weeks, early degeneration of nerve terminals was present associated with a dispersion of AChRs and abnormal preterminal accumulation of vesicles. These findings pointed towards a defect in maintenance of the initial innervation in developmental SMA muscle. Furthermore, postnatal muscle of type I SMA patients showed persistence of the foetal subunit of acetylcholine receptors, suggesting a continuous delay in maturation of neuromuscular junctions. Therefore, if nerve terminals are unable to efficiently maintain functional NMJs, a dying‐back process leading to motor neuron degeneration and loss may appear, with the consequent increase in programmed cell death. Despite all these early neuropathological findings, we did not observe qualitative differences in foetal movements between unaffected and SMA prenatal cases. The synaptic defects in SMA at this stage of development, therefore, might be compensated by several mechanisms. During perinatal and postnatal periods compensation would no longer be present, resulting in the drastic SMA pathology and clinical manifestations. CONCLUSIONS: These developmental studies open new possibilities to improve our knowledge of presymptomatic SMA stages. Early therapeutic strategies should be investigated to reverse the process of denervation, maintain activity of the NMJ, and improve maturity of the motor endplates.INTRODUCCIÓN: La atrofia muscular espinal (AME) es una enfermedad neuromuscular infantil caracterizada por la muerte de las neuronas motoras del asta anterior de la médula espinal. Como consecuencia de ello hay una degeneración y atrofia muscular, por lo que los pacientes mueren a menudo de insuficiencias respiratorias graves. La AME se clasifica en tres tipos principales según el grado de gravedad, la edad de aparición y las pautas motoras. Se trata de una enfermedad con patrón de herencia autosómico recesivo causada por ausencia o mutaciones en el gen Survival Motor Neuron 1 (SMN1). Existe un gen homólogo, SMN2, que está presente en todos los pacientes aunque a diferencia del SMN1, produce mucha menor proteína SMN completa y, por lo tanto, no evita la aparición de la enfermedad. Sin embargo se ha demostrado una importante correlación con el tipo de AME y el número de copias de SMN2. El rasgo patológico esencial de la AME es la muerte de las neuronas motoras. Estudios hechos en muestras fetales indican que ya existen hallazgos patológicos en el estadio prenatal lo que sugiere que la AME sería un trastorno del desarrollo. Además en modelos de ratón AME se ha determinado que la unión neuromuscular tendría un papel importante en la patogenia de la enfermedad aunque en humanos todavía no existen investigaciones al respecto. OBJETIVOS Y METODOLOGÍA: Con el fin de profundizar en los conocimientos de la patogenia de la AME, en esta tesis se ha realizado un análisis histológico, inmunohistoquímico y utraestructural del músculo y la unión neuromuscular en muestras prenatales y postnatales de controles y AME. Paralelamente, se han correlacionado los resultados neuropatológicos obtenidos con el estudio de la motilidad fetal por ecografía 2D entre las 11 y 14 semanas de gestación en embarazos diagnosticados genéticamente como AME. RESULTADOS: A partir de las 12 semanas, los miotubos AME son más pequeños que los controles lo que es compatible con un retraso en la maduración muscular. En esta etapa, la presencia de receptores de acetilcolina agrupados en músculo AME sugiere que éste es capaz de formar la placa neuromuscular. Sin embargo en semanas posteriores se observa una degeneración temprana de los terminales nerviosos asociados a una dispersión de los receptores de acetilcolina y acumulación anormal de vesículas presinápticas. Esto indica que en este período uno de los principales defectos sería la falta de mantenimiento de la unión neuromuscular. El músculo postnatal AME muestra persistencia de la expresión del receptor fetal de acetilcolina que refuerza la idea de una maduración retardada de la unión neuromuscular que persiste durante todo el desarrollo. La falta de mantenimiento de las uniones neuromusculares justificaría el inicio de un proceso de muerte retrograda (“dying back process”) dando lugar a una excesiva pérdida de neuronas motoras en la médula espinal. El estudio de los movimientos fetales, sin embargo, no demostró diferencias cualitativas entre los fetos normales y los AME. La falta de correlación entre la neuropatología descubierta en los fetos con AME tipo I y la presencia de movimientos fetales normales en ese mismo grupo indica que deben existir mecanismos compensatorios en el feto AME que enmascaran las posibles consecuencias funcionales de los defectos sinápticos hallados. Estos mecanismos compensatorios desaparecerían más tarde dando lugar a las graves manifestaciones de la enfermedad en las etapas perinatal y neonatal. CONCLUSIONES: Los resultados obtenidos contribuyen al mejor conocimiento de esta enfermedad en etapas presintomáticas, y abre nuevas perspectivas para investigar estrategias terapéuticas a fin de revertir los procesos de denervación, mantener la actividad de las uniones neuromusculares y mejorar la maduración de las placas motoras.Universitat de BarcelonaTizzano Ferrari, EduardoFerrer, Isidro (Ferrer Abizanda)Universitat de Barcelona. Facultat de Medicina2012info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersionapplication/pdfhttps://hdl.handle.net/2445/34744http://hdl.handle.net/10803/97097Tesis Doctorals - Facultat - Medicinareponame:Dipòsit Digital de la UBinstname:Universidad de BarcelonaEspañol(c) Martínez Hernàndez, 2012info:eu-repo/semantics/openAccessoai:diposit.ub.edu:2445/347442026-05-27T06:46:51Z |
| score |
15,301603 |