S100ß and fibroblast growth factor-2 are present in cultured Schwann cells and may exert paracrine actions on the peripheral nerve injury / S100ß e fator de crescimento de fibroblasto-2 estão presentes nas células de Schwann cultivadas e exercem ações parácrinas na lesão do nervo

PURPOSE: The neurotrophic factor fibroblast growth factor-2 (FGF-2, bFGF) and Ca++ binding protein S100ß are expressed by the Schwann cells of the peripheral nerves and by the satellite cells of the dorsal root ganglia (DRG). Recent studies have pointed out the importance of the molecules in the paracrine mechanisms related to neuronal maintenance and plasticity of lesioned motor and sensory peripheral neurons. Moreover, cultured Schwann cells have been employed experimentally in the treatment of central nervous system lesions, in special the spinal cord injury, a procedure that triggers an enhanced sensorymotor function. Those cells have been proposed to repair long gap nerve injury. METHODS: Here we used double labeling immunohistochemistry and Western blot to better characterize in vitro and in vivo the presence of the proteins in the Schwann cells and in the satellite cells of the DRG as well as their regulation in those cells after a crush of the rat sciatic nerve. RESULTS: FGF-2 and S100ß are present in the Schwann cells of the sciatic nerve and in the satellite cells of the DRG. S100ß positive satellite cells showed increased size of the axotomized DRG and possessed elevated amount of FGF-2 immunoreactivity. Reactive satellite cells with increased FGF-2 labeling formed a ring-like structure surrounding DRG neuronal cell bodies.Reactive S100ß positive Schwann cells of proximal stump of axotomized sciatic nerve also expressed higher amounts of FGF-2. CONCLUSION: Reactive peripheral glial cells synthesizing FGF-2 and S100ß may be important in wound repair and restorative events in the lesioned peripheral nerves.

OBJETIVO: O fator neurotrófico fator de crescimento de fibroblastos-2 (FGF-2, bFGF) e a proteína ligante de Ca++ S100ß são expressos pelas células de Schwann dos nervos e por células satélites do gânglio da raiz dorsal (GRD). Estudos recentes indicam a importância das moléculas nos mecanismos parácrinos relacionados à manutenção neuronal e à plasticidade de neurônios periféricos motores e sensoriais. Além disso, células de Schwann cultivadas têm sido empregadas experimentalmente no tratamento de lesões no sistema nervo central, especialmente na lesão da medula espinal, a qual mostrou uma melhora da função sensoriomotora. Estas células são ainda propostas no reparo do nervo lesado com perda de tecido. MÉTODOS: Usamos a dupla marcação imunohistoquímica e o Western blot para caracterizar melhor in vitro e in vivo a presença das proteínas nas células de Schwann e nas células satélites do GRD assim como sua regulação nessas células após a compressão do nervo ciático de ratos. RESULTADOS: FGF-2 e S100ß estão presentes nas células de Schwann do nervo ciático e nas células satélites do GRD. Células satélites do GRD axotomizado positivas para S100ß possuíam quantidade aumentada de imurreatividade da FGF-2. Células satélites reativas apresentando maior quantidade de FGF-2 formaram um anel ao redor dos corpos neuronais do GRD. Células de Schwann do coto proximal à axotomia do nervo ciático e positivas para S100ß também expressaram quantidades aumentadas de FGF-2. CONCLUSÃO: As células gliais periféricas ao sintetizar FGF-2 e S100ß podem ser importantes no reparo de cicatrização e em eventos restaurativos nas lesões do nervo.

Studies on the changes of c-fos protein in spinal cord and neurotransmitter in dorsal root ganglion of the rat with an experimental peripheral neuropathy

Animal models for human chronic pain syndromes have been developed and widely used for pain research. One of these neuropathic pain models by Kim and Chung (1992) has many advantages for operation and pain elicitation. In this neuropathic model we have examined the c-fos protein, substance P, CGRP immunoreactivity in dorsal root ganglia and dorsal horn. 50 Sprague-Dawley rats were used for this study. L5 and L6 spinal nerves were ligated tightly to produce the neuropathic pain model. After 2, 4, 8, 16, and 24 hours and 1 week of surgery, rats were anesthetized and sacrificed by perfusion. After confirmation of the roots transected by the surgery, the L5 and L6 dorsal root ganglions and spinal cord were removed and processed for immunohistochemistry. All tissue sections were immunohistochemically stained for substance P, CGRP and c-fos using the peroxidase-antiperoxidase (PAP) method. The number of immunostained substance P and CGRP dorsal root ganglion cells and c-fos immunoreactive dorsal horn cells were counted and analyzed statistically with Mann-Whitney U test. The results are as follows. The number of c-fos protein immunoreactive neurons in the superficial layer of dorsal horn were increased markedly 2 hours after operation, and gradually decreased to normal level 1 week after operation. The number of c-fos protein immunoreactive neurons in the deep layer of the dorsal horn gradually increased to a peak 24 hours after operation, then decreased to the normal level 1 week after operation. The number of substance P and CGRP immunoreactive L5 and L6 dorsal root ganglion neurons were decreased markedly 1 week after the pain model operation. In conclusion, after neuropathic pain model operation, c-fos proteins were immediately expressed in the superficial layer of spinal dorsal horn, thereafter c-fos proteins in the deep layer of spinal dorsal horn were expressed. CGRP and substance P immunoreactive neurons in DRG were decreased markedly 1 week after neuropathic pain model operation. These decrements do not coincide with the other chronic pain models, which show great increases in these pain transmitting substances. Therefore, the relationship between pain and c-fos, SP and CGRP should be investigated further.

Subpoblaciones neuronales presentes en el ganglio de la raíz dorsal / Neuronal subpopulations present in the dorsal root ganglion

La función principal de las neuronas del ganglio de la raíz dorsal (GRD) es transmitir la información sensorial desde la periferia hasta el sistema nervioso central. Dos clases de la célula están presentes en el ganglio: las células no neuronales y las neuronales. La heterogeneidad morfológica, fisiológica y bioquímica de la población neuronal permite diferenciarla en subpoblaciones. Morfológicamente, se distinguen tres tipos neuronales (A, B y C) según el tamaño y las características ulraestructurales. Fisiológicamente, hay una relación directa entre el tamaño, el diámetro de las fibras nerviosas y la velocidad con que conducen el impulso nervioso. Finalmente, el uso de marcadores (neuropéptidos, enzimas, receptores, etc.) permite realizar una clasificación bioquímica, que es la más utilizada para estudiar la función neuronal. Este artículo revisa la evidencia experimental sobre el tema de la heterogeneidad neural del GRD y presenta una correlación desde el punto de vista bioquímico y fisiológico en los casos en donde hay información disponible. El estudio de subpoblaciones en este ganglio resulta de bastante interés para investigaciones en neurociencias principalmente en infecciones por virus neurotrópicos, traumatismos del nervio periférico y el estudio de factores neurotróficos, entre otros