Glial cell line-derived neurotrophic factor added to a sciatic nerve fragment grafted in a spinal cord gap ameliorates motor impairments in rats and increases local axonal growth.

PURPOSE: The aversive nature of regenerative milieu is the main problem related to the failure of neuronal restoration in the injured spinal cord which however might be addressed with an adequate repair intervention. We evaluated whether glial cell line-derived neurotrophic factor (GDNF) may increase the ability of sciatic nerve graft, placed in a gap promoted by complete transections of the spinal cord, to enhance motor recovery and local fiber growth. METHODS: Rats received a 4 mm-long gap at low thoracic level and were repaired with a fragment of the sciatic nerve. GDNF was added (NERVE+/-GDNF) or not to the grafts (NERVE--GDNF). Motor behavior score (BBB) and sensorimotor tests-linked to the combined behavior score (CBS), which indicate the degree of the motor improvement and the percentage of functional deficit, respectively, and also the spontaneous motor behavior in an open field by means of an infrared motion sensor activity monitor were analyzed. At the end of the third month post surgery, the tissue composed by the graft and the adjacent regions of the spinal cord was removed and submitted to the immunohistochemistry of the neurofilament-200 (NF-200), growth associated protein-43 (GAP-43), microtubule associated protein-2 (MAP-2), 5-hidroxytryptamine (serotonin, 5-HT) and calcitonin gene related peptide (CGRP). The immunoreactive fibers were quantified at the epicenter of the graft by means of stereological procedures. RESULTS: Higher BBB and lower CBS levels (p < 0.001) were found in NERVE+/-GDNF rats. GDNF added to the graft increased the levels of individual sensorimotor tests mainly at the third month. Analysis of the spontaneous motor behavior showed decreases in the time and number of small movement events by the third month without changes in time and number of large movement events in the NERVE$+$GDNF rats. Immunoreactive fibers were encountered inside the grafts and higher amounts of NF-200, GAP-43 and MAP-2 fibers were found in the epicenter of the graft when GDNF was added. A small amount of descending 5-HT fibers was seen reentering in the adjacent caudal levels of the spinal cords which were grafted in the presence of GDNF, event that has not occurred without the neurotrophic factor. GDNF in the graft also led to a large amount of MAP-2 perikarya and fibers in the caudal levels of the cord gray matter, as determined by the microdensitometric image analysis. CONCLUSIONS: GDNF added to the nerve graft favored the motor recovery, local neuronal fiber growth and neuroplasticity in the adjacent spinal cord.

Responses of reactive astrocytes containing S100beta protein and fibroblast growth factor-2 in the border and in the adjacent preserved tissue after a contusion injury of the spinal cord in rats: implications for wound repair and neuroregeneration.

This paper demonstrates glial reaction and changes in the S100beta protein and basic fibroblast growth factor (bFGF, FGF-2) in the border and in the adjacent preserved tissue of the rat spinal cord after a contusion. In view of the expression of FGF-2 and S100beta in reactive glial cells and their ability to promote gliogenesis and neuronal trophism, the molecules have been considered to participate in the wound repair and regenerative events after nervous tissue injury. Adult rats were submitted to a moderate spinal cord (10th thoracic level) contusion induced by a New York University Impactor by dropping a 10 g rod from a distance of 25 mm onto the dorsal surface of the exposed dura spinal cord. Impactor curves and parameters were used to monitor the severity of the trauma. Control rats were submitted to sham operation. The motor behavioral spontaneous recovery was demonstrated by means of a BBB test and the combining behavior score up to 3 weeks after injury. Animals were killed 72 hours, 2, and 3 weeks after surgery and spinal cords were processed for immunohistochemistry to show glial fibrillary acidic protein positive astrocytes and OX-42-positive microglia/macrophages as well as changes in the S100beta and FGF-2 in the border and in the adjacent preserved tissue of the lesioned cords. The changes in the immunoreaction products were quantified by means of morphometric/microdensitometric image analysis, and the cell type expressing S100beta and FGF-2 was analyzed by means of two-color immunofluorescence procedures. Massive increases of S100beta and FGF-2 were found in reactive astrocytes, not in reactive microglia, in the border and in the white and gray matters of adjacent preserved tissue of the contused spinal cord in the periods studied. The results are discussed in view of possible paracrine trophic actions of the reactive astrocytes, mediated by S100beta and FGF-2, triggering wound repair events in the border of the trauma, and also leading to neurotrophism and neuronal plasticity in the adjacent regions. These cellular and molecular responses may interfere with the pattern of behavioral recovery after a contusion injury of the spinal cord.