Sensory root demyelination: Transforming touch into pain.

The normal feeling of touch is vital for nearly every aspect of our daily life. However, touching is not always felt as touch, but also abnormally as pain under numerous diseased conditions. For either mechanistic understanding of the faithful feeling of touch or clinical management of chronic pain, there is an essential need to thoroughly dissect the neuropathological changes that lead to painful touch or tactile allodynia and their corresponding cellular and molecular underpinnings. In recent years, we have seen remarkable progress in our understanding of the neural circuits for painful touch, with an increasing emphasis on the upstream roles of non-neuronal cells. As a highly specialized form of axon ensheathment by glial cells in jawed vertebrates, myelin sheaths not only mediate their outstanding neural functions via saltatory impulse propagation of temporal and spatial precision, but also support long-term neuronal/axonal integrity via metabolic and neurotrophic coupling. Therefore, myelinopathies have been implicated in diverse neuropsychiatric diseases, which are traditionally recognized as a result of the dysfunctions of neural circuits. However, whether myelinopathies can transform touch into pain remains a long-standing question. By summarizing and reframing the fragmentary but accumulating evidence so far, the present review indicates that sensory root demyelination represents a hitherto underappreciated neuropathological change for most neuropathic conditions of painful touch and offers an insightful window into faithful tactile sensation as well as a potential therapeutic target for intractable painful touch.

MHCII-restricted T helper cells: an emerging trigger for chronic tactile allodynia after nerve injuries.

Nerve injury-induced chronic pain has been an urgent problem for both public health and clinical practice. While transition to chronic pain is not an inevitable consequence of nerve injuries, the susceptibility/resilience factors and mechanisms for chronic neuropathic pain after nerve injuries still remain unknown. Current preclinical and clinical studies, with certain notable limitations, have shown that major histocompatibility complex class II-restricted T helper (Th) cells is an important trigger for nerve injury-induced chronic tactile allodynia, one of the most prevalent and intractable clinical symptoms of neuropathic pain. Moreover, the precise pathogenic neuroimmune interfaces for Th cells remain controversial, not to mention the detailed pathogenic mechanisms. In this review, depending on the biology of Th cells in a neuroimmunological perspective, we summarize what is currently known about Th cells as a trigger for chronic tactile allodynia after nerve injuries, with a focus on identifying what inconsistencies are evident. Then, we discuss how an interdisciplinary perspective would improve the understanding of Th cells as a trigger for chronic tactile allodynia after nerve injuries. Finally, we hope that the expected new findings in the near future would translate into new therapeutic strategies via targeting Th cells in the context of precision medicine to either prevent or reverse chronic neuropathic tactile allodynia.

CD4+ αß T cell infiltration into the leptomeninges of lumbar dorsal roots contributes to the transition from acute to chronic mechanical allodynia after adult rat tibial nerve injuries.

BACKGROUND: Antigen-specific and MHCII-restricted CD4+ αß T cells have been shown or suggested to play an important role in the transition from acute to chronic mechanical allodynia after peripheral nerve injuries. However, it is still largely unknown where these T cells infiltrate along the somatosensory pathways transmitting mechanical allodynia to initiate the development of chronic mechanical allodynia after nerve injuries. Therefore, the purpose of this study was to ascertain the definite neuroimmune interface for these T cells to initiate the development of chronic mechanical allodynia after peripheral nerve injuries. METHODS: First, we utilized both chromogenic and fluorescent immunohistochemistry (IHC) to map αß T cells along the somatosensory pathways for the transmission of mechanical allodynia after modified spared nerve injuries (mSNIs), i.e., tibial nerve injuries, in adult male Sprague-Dawley rats. We further characterized the molecular identity of these αß T cells selectively infiltrating into the leptomeninges of L4 dorsal roots (DRs). Second, we identified the specific origins in lumbar lymph nodes (LLNs) for CD4+ αß T cells selectively present in the leptomeninges of L4 DRs by two experiments: (1) chromogenic IHC in these lymph nodes for CD4+ αß T cell responses after mSNIs and (2) fluorescent IHC for temporal dynamics of CD4+ αß T cell infiltration into the L4 DR leptomeninges after mSNIs in prior lymphadenectomized or sham-operated animals to LLNs. Finally, following mSNIs, we evaluated the effects of region-specific targeting of these T cells through prior lymphadenectomy to LLNs and chronic intrathecal application of the suppressive anti-αßTCR antibodies on the development of mechanical allodynia by von Frey hair test and spinal glial or neuronal activation by fluorescent IHC. RESULTS: Our results showed that during the sub-acute phase after mSNIs, αß T cells selectively infiltrate into the leptomeninges of the lumbar DRs along the somatosensory pathways responsible for transmitting mechanical allodynia. Almost all these αß T cells are CD4 positive. Moreover, the temporal dynamics of CD4+ αß T cell infiltration into the lumbar DR leptomeninges are specifically determined by LLNs after mSNIs. Prior lymphadenectomy to LLNs specifically reduces the development of mSNI-induced chronic mechanical allodynia. More importantly, intrathecal application of the suppressive anti-αßTCR antibodies reduces the development of mSNI-induced chronic mechanical allodynia. In addition, prior lymphadenectomy to LLNs attenuates mSNI-induced spinal activation of glial cells and PKCγ+ excitatory interneurons. CONCLUSIONS: The noteworthy results here provide the first evidence that CD4+ αß T cells selectively infiltrate into the DR leptomeninges of the somatosensory pathways transmitting mechanical allodynia and contribute to the transition from acute to chronic mechanical allodynia after peripheral nerve injuries.

[Helminth derived Immunomodulatory Glycan LNFP3 Impairs Pathogenesis of Peripheral Neuropathic Pain and Spinal Glial Activation].

OBJECTIVES: To investigate the effect of helminth-derived immunomodulatory glycan lacto-N-fucopentaose3(LNFP3) on the pathogenesis of neuropathic pain and spinal glial activation in the corresponding time windows after adult rat tibial nerve permanent transection (modified spared nerve injury, mSNI). METHODS: Ten weeks old male adult Sprague-Dawley (SD) rats weighing 250-300 g were randomly grouped into four groups: sham-operated group (n =6), mSNI group (n =6), mSNI plus bovine serum albumin (BSA) group (n =12) and mSNI plus LNFP3 group (n=12). Rats were subjected to surgical operation or sham operation on the right tibial nerves and were intraperitoneal injected BSA or LNEP3-BSA conjugates by the group design. Animals from each group (n=6 per group) were subjected to the plantar test,von Frey hairs test, pinprick test and acetone test for critical evaluation of region-specific pain responses on the plantar sural and saphenous skin territories of ipsilateral and contralateral hindpaws after injuries. Transverse frozen sections of L3-4 spinal cords from the remaining animals of mSNI plus BSA group and mSNI plus LNFP3 group 7 and 14 d after injury (n=3 for each time point per group)were prepared and subjected to immunofluorescent staining of microglia/macrophage marker [cluster of differentiation molecule 11b (CD11b)] and astrocyte marker [glial fibrillary acidic protein (GFAP)], for analysis of spinal glial activation. RESULTS: After adult rat mSNI, early systematic administration of LNFP3 significantly but not completely attenuated region-specific pathological pain evoked by mechanical and thermal stimuli on the sural and saphenous skin territories of rat hindpaw plantar surfaces in acute (4/5 d after injuries) and subacute (7/8 d and 14/15 d after injuries) phases. Meanwhile, in the ipsilateral spinal cord dorsal horns, this early systematic treatment inhibited microglia/macrophage activation 7 d after injury and astrocyte activation 7 and 14 d after injury. CONCLUSIONS: Early systematic administration of LNFP3 impairs the pathogenesis (acute induction and chronic transition) of neuropathic pain and spinal glial activation in the corresponding time windows after adult rat mSNI.

[Early Systemic Administration of IL-10 Inhibits Neuropathic Pain in Adult Rats with Tibial Nerve Injury].

OBJECTIVES: To determine the effect of early systemic administration of IL-10 on peripheral neuropathic pain induced by tibial nerve permanent transection [modified spared nerve injury (mSNI)]in adult rats. METHODS: Male adult Sprague-Dawley (SD) rats (ten-week old, 250-300 g) with mSNI were randomly divided into mSNI, sham-operated, IL-10 intervention (intraperitoneal injection), PBS intervention (intraperitoneal injection) groups, each containing six rats. Intraperitoneally injections (IL-10 or PBS) were given immediately after surgeries for a single regime with a dosage of 500 uL (0.1 mg/mL). Plantar test, von Frey hairs test, pinprick test and acetone test were performed before and after tibial nerve injuries (0 d, 4/5 d, 7/8 d, 14/15 d) to evaluate region-specific pain responses of the rats on the plantar sural and saphenous skin territories of ipsilateral and contralateral hindpaws. The hindpaw position (on 8 d) of six additional rats with standard SNI was compared with those with mSNI. RESULTS: The rats with standard SNI showed an eversion posture of hindpaws, more prominent than those with mSNI. Region-specific pathological pain evoked by mechanical and thermal stimuli on the sural and saphenous skin territories of the plantar surfaces of rat hindpaws was demonstrated on the ipsilateral rather than contralateral hindpaws. This effect was shown in the rats with mSNI but not in those with sham operations. Compared with PBS, early intraperitoneal injection of IL-10 significantly and persistently attenuated either allodynia or hyperalgesia in the rats with mSNI. CONCLUSIONS: Tibial nerve permanent transection models of adult rats can be used as a simple but useful rodent model of peripheral neuropathic pain. Early systemic administration of IL-10 impairs the pathogenesis of neuropathic pain induced by tibial nerve injuries.

[Senescence-associated Beta Galactosidase Expression in Rat Schwann Cells after Chronic Denervation].

OBJECTIVE: To investigate the effect of prolonged axon depletion on senescence-associated beta galactosidase (SA-ß-gal) expression in Schwann cells (SCs) of adult rats. METHODS: Male adult Sprague-Dawley (SD) rats were randomize grouped into sham-operated group and denervation groups for 1 week, 2 weeks, 4 weeks, 5 weeks, 6 weeks, 7 weeks and 8 weeks. Rats were subjected to right sciatic nerve transection. After particular denervation duration for the distal stumps, animals were anesthetized and perfused. Proximal stumps of 5 mm and distal stumps of 10 mm from injured nerves, and the corresponding segments from the sham groups and contralateral nerves were harvested and prepared for SA-ß-gal staining to detect SA-ß-gal expression. Then, additional injured distal stumps denervated for 8 weeks were employed for determining cellular distribution of SA-ß-gal expression by co-labeling of SA-ß-gal and SC-specific protein (S100ß). RESULTS: SA-ß-gal expression transiently increased in distal tips of proximal stumps 2 weeks after adult rat sciatic nerve transection without suture. In contrast, in the distal stumps of transected adult rat sciatic nerves, axon depletion for 2 weeks increased SA-ß-gal expression, and the increased expression of SA-ß-gal remained constant after prolonged denervation durations. Furthermore, combination of SA-ß-gal staining with S100ß immunofluorescence staining showed that SA-ß-gal expression. was exclusively present in denervated SCs. CONCLUSION: Prolonged axon depletion increased SA-ß-gal expression in adult rat SCs.

Transplantation of olfactory ensheathing cells promotes the recovery of neurological functions in rats with traumatic brain injury associated with downregulation of Bad.

BACKGROUND AIMS: The neuroprotective effects of olfactory ensheathing cells (OECs) after transplantation have largely been known in the injured nervous system. However, the underlying mechanisms still must be further elucidated. We explored the effects of OEC transplantation on the recovery of neurophysiologic function and the related anti-apoptosis mechanism in acute traumatic brain injury. METHODS: The OECs from neonatal Sprague-Dawley rats were isolated, identified and labeled and then were immediately transplanted into the regions surrounding the injured brain site that is resulted from free-weight drop injury. RESULTS: Nerve growth factor and it's recepor, p75 was expressed in cultured OECs. Transplanted OECs survived, migrated around the injury site and significantly improved the neurological severe scores compared with the control group (P < 0.05). OEC transplantation significantly increased the number of GAP-43-immunopositive fibers and synaptophysin-positive vesicles (P < 0.05) but significantly decreased the number of apoptotic cells (P < 0.05). On the molecular level, the expression of Bad in the OEC transplantation group was significantly downregulated (P < 0.05). CONCLUSIONS: OEC transplantation could effectively improve neurological deficits in TBI rats; the underlying mechanism may be related with their effects on neuroprotection and regeneration induction, which is associated with the downregulation of the apoptotic molecule Bad.

Neural stem cells grafts decrease neural apoptosis associated with caspase-7 downregulation and BDNF upregulation in rats following spinal cord hemisection.

Transplantation of neural stem cells (NSCs) into lesioned spinal cord demonstrated a beneficial effect for neural repair, the underlying mechanism, however, remains to be elusive. Here, we showed that NSCs, possessing the capacity to differentiate toward into neurons and astrocytes, exhibit a neuroprotective effect by anti-apoptosis mechanism in spinal cord hemi-transected rats despite it did not improve behavior. Intravenous NSCs injection substantially upregulated the level of BDNF mRNA but not its receptor TrkB in hemisected spinal cord, while caspase-7, a downstream apoptosis gene of caspase-3, has been largely down-regulated. TUNEL staining showed that the number of apoptosis cells in injured spinal cord decreased significantly, compared with seen in rats with no NSCs administration. The present finding therefore provided crucial evidence to explain neuroprotective effect of NSCs grafts in hemisected spinal cord, which is associated with BDNF upregulation and caspase-7 downregulation.

Huntingtin associated protein 1 regulates trafficking of the amyloid precursor protein and modulates amyloid beta levels in neurons.

Amyloid precursor protein (APP) is involved in the pathogenesis of Alzheimer's disease. It is axonally transported, endocytosed and sorted to different cellular compartments where amyloid beta (Aß) is produced. However, the mechanism of APP trafficking remains unclear. We present evidence that huntingtin associated protein 1 (HAP1) may reduce Aß production by regulating APP trafficking to the non-amyloidogenic pathway. HAP1 and APP are highly colocalized in a number of brain regions, with similar distribution patterns in both mouse and human brains. They are associated with each other, the interacting site is the 371-599 of HAP1. APP is more retained in cis-Golgi, trans-Golgi complex, early endosome and ER-Golgi intermediate compartment in HAP1-/- neurons. HAP1 deletion significantly alters APP endocytosis and reduces the re-insertion of APP into the cytoplasmic membrane. Amyloid precursor protein-YFP(APP-YFP) vesicles in HAP1-/- neurons reveal a decreased trafficking rate and an increased number of motionless vesicles. Knock-down of HAP1 protein in cultured cortical neurons of Alzheimer's disease mouse model increases Aß levels. Our data suggest that HAP1 regulates APP subcellular trafficking to the non-amyloidogenic pathway and may negatively regulate Aß production in neurons.

Temporal changes in the expression of TGF-beta 1 and EGF in the ventral horn of the spinal cord and associated precentral gyrus in adult Rhesus monkeys subjected to cord hemisection.

It is well known that some growth factors can not only rescue neurons from death, but also improve motor functions following spinal cord injury. However, their cellular distribution in situ and temporal expressions following spinal cord injury have not been determined, especially in primates. This study investigated the temporal changes in the expression of two growth factors--epidermal growth factor (EGF) and transforming growth factor-beta 1 (TGF-beta1) in the injured motoneurons of the spinal cord and the associated precentral gyrus in adult Rhesus monkeys subjected to spinal cord hemisection. Animals were allowed to survive 7, 14, 30 and 90 days post operation (dpo). Functional recovery of the hindlimbs was assessed using Tarlov scale. The immunohistological expressions of EGF and TGF-beta1 in the ventral horn motoneurons decreased sharply at 7 dpo in the cord segments caudal to the lesion site, which was followed by an increase and a peak between 14 and 30 dpo for EGF and at 90 dpo for TGF-beta1. Changes in the expression of EGF in the precentral gyrus were similar to that in the spinal cord. No TGF-beta1 immunoreactive neurons were detected in the precentral gyrus. In the spinal segments rostral to the lesion, the expressions of EGF and TGF-beta1 peaked at 30 dpo. The mRNA of EGF was detected in both spinal motoneurons and the precentral gyrus, while that of TGF-beta1, only in the spinal motoneuons, suggesting that the spinal motoneurons themselves could synthesize both the growth factors. Partial locomotor recovery in hindlimbs was seen, especially after 14 dpo. It was concluded that a possible association existed between the modulation of EGF and TGF-beta1 and the recovery of locomotor function, and their roles differed somewhat in the neuroplasticity observed after spinal cord injury in primates.

Electro-acupuncture induced NGF, BDNF and NT-3 expression in spared L6 dorsal root ganglion in cats subjected to removal of adjacent ganglia.

This study evaluated the effect of electro-acupuncture (EA) on the NGF, BDNF and NT-3 expression in spared L6 dorsal root ganglion (DRG) in cats subjected to bilateral removal of L1-L5 and L7-S2 DRG, using immunostaining, in situ hybridization and RT-PCR. The positive products of NGF, NT-3 protein and mRNA in the small and large neurons of spared L6 DRG in EA side increased greatly more than that of control side, while the increased BDNF was only noted in small and medium-sized neurons. RT-PCR demonstrated that the mRNA level for three factors was not influenced by EA in intact DRG, when a significant increase was seen in the spared L6 DRG of EA side. As it has been well known that DRG neurons project to the spinal cord wherein morphological plasticity has been present after DRG removal, the present results might have some bearing to the observed phenomenon.

[Changes in number of EGF positive neurons in ventral horn and contralateral cortex motor area of rhesus after hemisection spinal cord injury].

OBJECTIVE: To observe the changes in the amount of epidermal growth factor (EGF) immunopositive neurons in ventral horn and contralateral cortex motor area of rhesus following hemisection spinal cord injury (hSCI). METHODS: Eighteen adult healthy rhesus were randomly divided into six groups: Sham-operation group; Day 7, Day 14, Month 1. Month 2 and Month 3 hemisection spinal cord injury groups. In the hSCI groups, the monkeys were subjected to left hemisection of T11 spinal cord, and then were put to death at the corresponding time after operation. The rostral part 5 mm proximal to the lesioned point of spinal cord and the caudal part 5 mm distal to the lesioned point were taken from each monkey. The contralateral cortex motor area was taken out, too. Frozen sections were incubated in specific polyclonal anti-EGF antibody; the immunohistochemical SP method was adopted in the study. RESULTS: In 3 months after hSCI, the number of EGF immunopositive neurons in the ventral horn of spinal cord near the lesion and in the contralateral cortex motor area of brain decreased as compared with those of the sham-operation group (P<0.05). The number of positive neurons decreased first, then came back, and later after hSCI, decreased again (P<0.05). Besides this, the number of positive neurons varied in different parts at the same time point. CONCLUSION: The EGF immunopositive neurons decreased apparently in the ventral horn of spinal cord near the lesion and in the contralateral cortex motor area in 3 months after hSCI. Hemisection spinal cord injury affected the expression of EGF for motor neurons in ventral horn on the lesioned side as well as on the intact side. Early after hSCI the number of positive neurons decreased sharply and then came back spontaneously in the ventral horn of spinal cord near the lesion and in the contralateral cortex of brain.

Regenerative peripheral neuropathic pain: novel pathological pain, new therapeutic dimension.

After peripheral nerve damage, injured or stressed primary sensory neurons (PSNs) transmitting pathological pain (pathopain) sensitize central nervous system (CNS) neural circuits and determine behavioral phenotypes of peripheral neuropathic pain (PNP). Therefore, phenotypic profiling of pathopain-transmitting PSNs is vital for probing and discovering PNP conditions. Following peripheral nerve injuries (PNIs), PNP might be potentially transmitted by distinct classes of damaged or stressed PSNs, such as axotomized PSNs without regeneration (axotomy-non-regenerative neurons), axotomized PSNs with accurate regeneration (axotomy-regenerative neurons), and spared intact PSNs adjacent to axotomized neurons (axotomy-spared neurons). Both axotomy-non-regenerative neurons and axotomy-spared neurons have been definitely shown to participate in specific PNP transmission. However, whether axotomy-regenerative neurons could transmit PNP with unique features has remained unclear. Recent studies in rodent models of axonotmesis have clearly demonstrated that axotomy-regenerative neurons alone transmit persistent pathological pain with unique behavioral phenotypes. In this review, we exclusively review this novel category of PNP, reasonably term it 'regenerative peripheral neuropathic pain', and finally discuss its potential clinical significance as a new therapeutic dimension for PNIs beyond nerve regeneration.

Antibody incubation at 37°C improves fluorescent immunolabeling in free-floating thick tissue sections.

Fluorescent immunolabeling and imaging in free-floating thick (50-60 µm) tissue sections is relatively simple in practice and enables design-based non-biased stereology, or 3-D reconstruction and analysis. This method is widely used for 3-D in situ quantitative biology in many areas of biological research. However, the labeling quality and efficiency of standard protocols for fluorescent immunolabeling of these tissue sections are not always satisfactory. Here, we systematically evaluate the effects of raising the conventional antibody incubation temperatures (4°C or 21°C) to mammalian body temperature (37°C) in these protocols. Our modification significantly enhances the quality (labeling sensitivity, specificity, and homogeneity) and efficiency (antibody concentration and antibody incubation duration) of fluorescent immunolabeling of free-floating thick tissue sections.

Involvement of SMAD4, but not of SMAD2, in transforming growth factor-beta1-induced trophoblast expression of matrix metalloproteinase-2.

Matrix metalloproteinases (MMPs) play crucial roles in extravillous trophoblast invasion. In the present study, we examined the possible role of Smad4 and Smad2 in transforming growth factor (TGF)-beta1-induced MMP-2 expression, using the well-established invasive extravillous trophoblast cell line HTR-8/SVneo. Recombinant sense Smad4 or Smad2 retroviral vectors were constructed by inserting full-length Smad4 or Smad2 cDNA into pLXSN retroviral vector. Stable PT67 packaging cell clones were isolated and viral supernatants were used to infect HTR-8/SVneo cells. Effects of retroviral expression of Smad4 and Smad2 on TGF-beta1-regulated MMP-2 expression were assessed by semi-quantitative reverse transcription-polymerase chain reaction and gelatin zymography. The results showed that over-expression of Smad4 augmented MMP-2 mRNA abundance and the secretion of pro-MMP-2, and mimicked the inductive effect of TGF-beta1 on the production of MMP-2. However, retrovirus-mediated sense Smad2 gene transfer had no effect. These findings suggest that Smad4, but not Smad2, mediates TGF-beta1-induced MMP-2 expression in invasive extravillous trophoblasts.

Behavioral characterization of neuropathic pain on the glabrous skin areas reinnervated solely by axotomy-regenerative axons after adult rat sciatic nerve crush.

In cranial and spinal nerve ganglia, both axotomized primary sensory neurons without regeneration (axotomy-nonregenerative neurons) and spared intact primary sensory neurons adjacent to axotomized neurons (axotomy-spared neurons) have been definitely shown to participate in pain transmission in peripheral neuropathic pain states. However, whether axotomized primary sensory neurons with regeneration (axotomy-regenerative neurons) would be integral components of neural circuits underlying peripheral neuropathic pain states remains controversial. In the present study, we utilized an adult rat sciatic nerve crush model to systematically analyze pain behaviors on the glabrous plantar surface of the hindpaw sural nerve skin territories. To the best of our knowledge, our results for the first time showed that heat hyperalgesia, cold allodynia, mechanical allodynia, and mechanical hyperalgesia emerged and persisted on the glabrous sural nerve skin areas after adult rat sciatic nerve crush. Interestingly, mechanical hyperalgesia was sexually dimorphic. Moreover, with our optimized immunofluorescence staining protocol of free-floating thick skin sections for wide-field epifluorescence microscopic imaging, changes in purely regenerative reinnervation on the same skin areas by axotomized primary sensory afferents were shown to be paralleled by those pathological pain behaviors. To our surprise, Protein Gene Product 9.5-immunoreactive nerve fibers with regular and large varicosities ectopically emigrated into the upper dermis of the glabrous sural nerve skin territories after adult rat sciatic nerve crush. Our results indicated that axotomy-regenerative primary sensory neurons could be critical elements in neural circuits underlying peripheral neuropathic pain states. Besides, our results implied that peripheral neuropathic pain transmitted by axotomy-regenerative primary sensory neurons alone might be a new dimension in the clinical therapy of peripheral nerve trauma beyond regeneration.

ProBDNF inhibits collective migration and chemotaxis of rat Schwann cells.

Schwann cell migration, including collective migration and chemotaxis, is essential for the formation of coordinate interactions between Schwann cells and axons during peripheral nerve development and regeneration. Moreover, limited migration of Schwann cells imposed a serious obstacle on Schwann cell-astrocytes intermingling and spinal cord repair after Schwann cell transplantation into injured spinal cords. Recent studies have shown that mature brain-derived neurotrophic factor, a member of the neurotrophin family, inhibits Schwann cell migration. The precursor form of brain-derived neurotrophic factor, proBDNF, was expressed in the developing or degenerating peripheral nerves and the injured spinal cords. Since "the yin and yang of neurotrophin action" has been established as a common sense, proBDNF would be expected to promote Schwann cell migration. However, we found, in the present study, that exogenous proBDNF also inhibited in vitro collective migration and chemotaxis of RSC 96 cells, a spontaneously immortalized rat Schwann cell line. Moreover, proBDNF suppressed adhesion and spreading of those cells. At molecular level, proBDNF inhibits F-actin polymerization and focal adhesion dynamics in cultured RSC 96 cells. Therefore, our results suggested a special case against the classical opinion of "the yin and yang of neurotrophin action" and implied that proBDNF might modulate peripheral nerve development or regeneration and spinal cord repair through perturbing native or transplanted Schwann cell migration.

[Distribution of epidermal growth factor in central nervous system of adult rhesus monkey].

OBJECTIVE: To investigate the distribution of epidermal growth factor (EGF) in the CNS of adult rhesus monkey. METHODS: Frozen sections were incubated in specific polyclonal anti-EGF antibody by the immunohistochemical SP method. RESULTS: The EGF immunopositive reaction was observed in the plasma of neurons. The neurons with strong positive immuno-reaction signals were detected in cerebral cortex, cerebellar Purkinje cells, cerebellar nuclei, pyramidal neurons of hippocampus, caudate nucleus, lentiform nucleus, claustrum, nuclei in diencephalons, substantia nigra, cranial nerve nuclei, reticular formation in brain stem, pontine nuclei, red nucleus, superior and inferior olivary nucleus, gracile nucleus, cuneate nucleus, also the ventral horn, lateral horn, dorsal horn and the central gray matter in spinal cord. Furthermore, a few EGF immunopositive glias and fibres were observed in some white matter of central nervous system. CONCLUSION: EGF immunoreactive material was extensively distributed in the CNS of the adult rhesus monkey. The results suggest that EGF may be concerned with various types of neurons and other cells.

Differential motor and sensory functional recovery in male but not female adult rats is associated with remyelination rather than axon regeneration after sciatic nerve crush.

Peripheral nerve functional recovery after injuries relies on both axon regeneration and remyelination. Both axon regeneration and remyelination require intimate interactions between regenerating neurons and their accompanying Schwann cells. Previous studies have shown that motor and sensory neurons are intrinsically different in their regeneration potentials. Moreover, denervated Schwann cells accompanying myelinated motor and sensory axons have distinct gene expression profiles for regeneration-associated growth factors. However, it is unknown whether differential motor and sensory functional recovery exists. If so, the particular one among axon regeneration and remyelination responsible for this difference remains unclear. Here, we aimed to establish an adult rat sciatic nerve crush model with the nonserrated microneedle holders and measured rat motor and sensory functions during regeneration. Furthermore, axon regeneration and remyelination was evaluated by morphometric analysis of electron microscopic images on the basis of nerve fiber classification. Our results showed that Aα fiber-mediated motor function was successfully recovered in both male and female rats. Aδ fiber-mediated sensory function was partially restored in male rats, but completely recovered in female littermates. For both male and female rats, the numbers of regenerated motor and sensory axons were quite comparable. However, remyelination was diverse among myelinated motor and sensory nerve fibers. In detail, Aß and Aδ fibers incompletely remyelinated in male, but not female rats, whereas Aα fibers fully remyelinated in both sexes. Our result indicated that differential motor and sensory functional recovery in male but not female adult rats is associated with remyelination rather than axon regeneration after sciatic nerve crush.

NT-3 expression in spared DRG and the associated spinal laminae as well as its anterograde transport in sensory neurons following removal of adjacent DRG in cats.

Neurotrophin-3 plays an important role in survival and differentiation of sensory and sympathetic neurons, sprouting of neurites, synaptic reorganization, and axonal growth. The present study evaluated changes in expression of NT-3 in the spinal cord and L6 dorsal root ganglion (DRG), after ganglionectomy of adjacent dorsal roots in cats. NT-3 immunoreactivity increased at 3 days post-operation (dpo), but decreased at 10 dpo in spinal lamina II after ganglionectomy of L1-L5 and L7-S2 (leaving L6 DRG intact). Conversely, NT-3 immunoreactivity decreased on 3 dpo, but increased on 10 dpo in the nucleus dorsalis. Very little NT-3 mRNA signal was detected in the spinal cord, despite the changes in NT-3 expression. The above changes may be related to changes in NT-3 expression in the DRG. Ganglionectomy of L1-L5 and L7-S2 resulted in increase in NT-3 immunoreactivity and mRNA in small and medium-sized neurons, but decreased expression in large neurons of L6 DRG at 3 dpo. It is possible that increased NT-3 in spinal lamina II is derived from anterograde transport from small- and medium-sized neurons of L6 DRG, whereas decreased NT-3 immunoreactivity in the nucleus dorsalis is due to decreased transport of NT-3 from large neurons in the DRG at this time. This notion is supported by observations on NT-3 distribution in the dorsal root of L6 after ligation of the nerve root. The above results indicate that DRG may be a source of neurotrophic factors such as NT-3 to the spinal cord, and may contribute to plasticity in the spinal cord after injury.