Rapid-stretch injury to peripheral nerves: implications from an animal model.

OBJECTIVE: Rapid-stretch nerve injuries are among the most devastating lesions to peripheral nerves, yielding unsatisfactory functional outcomes. No animal model has yet been developed that uses only stretch injury for investigation of the pathophysiology of clinical traction injuries. The authors' objective was to define the behavioral and histopathological recovery after graded rapid-stretch nerve injury. METHODS: Four groups of male B6.Cg-Tg(Thy1-YFP)HJrs/J mice were tested: sham injury (n = 11); stretch within elastic limits (elastic group, n = 14); stretch beyond elastic limits but before nerve rupture (inelastic group, n = 14); and stretch-ruptured nerves placed in continuity (rupture group, n = 16). Mice were injured at 8 weeks of age, comparable with human late adolescence. Behavioral outcomes were assessed using the sciatic functional index (SFI), tapered-beam dexterity, Von Frey monofilament testing, and the Hargreaves method. Nerve regeneration outcomes were assessed by wet muscle weight and detailed nerve histology after 48 days. RESULTS: Post hoc biomechanical assessment of strain and deformation confirmed that the differences between the elastic and inelastic cohorts were statistically significant. After elastic injury, there was a temporary increase in foot faults on the tapered beam (p < 0.01) and mild reduction in monofilament sensitivity, but no meaningful change in SFI, muscle weight, or nerve histology. For inelastic injuries, there was a profound and maintained decrease in SFI (p < 0.001), but recovery of impairment was observed in tapered-beam and monofilament testing by days 15 and 9, respectively. Histologically, axon counts were reduced (p = 0.04), muscle atrophy was present (p < 0.01), and there was moderate neuroma formation on trichrome and immunofluorescent imaging. Stretch-ruptured nerves healed in continuity but without evidence of regeneration. Substantial and continuous impairment was observed in SFI (p < 0.001), tapered beam (p < 0.01), and monofilament (p < 0.01 until day 48). Axon counts (p < 0.001) and muscle weight (p < 0.0001) were significantly reduced, with little evidence of axonal or myelin regeneration concurrent with neuroma formation on immunofluorescent imaging. CONCLUSIONS: The 3 biomechanical grades of rapid-stretch nerve injuries displayed consistent and distinct behavioral and histopathological outcomes. Stretch within elastic limits resembled neurapraxic injuries, whereas injuries beyond elastic limits demonstrated axonotmesis coupled with impoverished regeneration and recovery. Rupture injuries uniquely failed to regenerate, despite physical continuity of the nerve. This is the first experimental evidence to correlate stretch severity with functional and histological outcomes. Future studies should focus on the pathophysiological mechanisms that reduce regenerative capacity after stretch injury.

Impaired functional recovery of endothelial colony-forming cells from moyamoya disease in a chronic cerebral hypoperfusion rat model.

OBJECTIVEEndothelial colony-forming cells (ECFCs) isolated from pediatric patients with moyamoya disease (MMD) have demonstrated decreased numbers and defective functioning in in vitro experiments. However, the function of ECFCs has not been evaluated using in vivo animal models. In this study, the authors compared normal and MMD ECFCs using a chronic cerebral hypoperfusion (CCH) rat model.METHODSA CCH rat model was made via ligation of the bilateral common carotid arteries (2-vessel occlusion [2-VO]). The rats were divided into three experimental groups: vehicle-treated (n = 8), normal ECFC-treated (n = 8), and MMD ECFC-treated (n = 8). ECFCs were injected into the cisterna magna. A laser Doppler flowmeter was used to evaluate cerebral blood flow, and a radial arm maze test was used to examine cognitive function. Neuropathological examinations of the hippocampus and agranular cortex were performed using hematoxylin and eosin and Luxol fast blue staining in addition to immunofluorescence with CD31, von Willebrand factor, NeuN, myelin basic protein, glial fibrillary acidic protein, and cleaved caspase-3 antibodies.RESULTSThe normal ECFC-treated group exhibited improvement in the restoration of cerebral perfusion and in behavior compared with the vehicle-treated and MMD ECFC-treated groups at the 12-week follow-up after the 2-VO surgery. The normal ECFC-treated group showed a greater amount of neovasculogenesis and neurogenesis, with less apoptosis, than the other groups.CONCLUSIONSThese results support the impaired functional recovery of MMD ECFCs compared with normal ECFCs in a CCH rat model. This in vivo study suggests the functional role of ECFCs in the pathogenesis of MMD.

Detection of glioblastoma in biofluids.

The detection of glioblastoma (GBM) in biofluids offers potential advantages over existing paradigms for the diagnosis and therapeutic monitoring of glial tumors. Biofluid-based detection of GBM focuses on detecting tumor-specific biomarkers in the blood and CSF. Current clinical research concentrates on studying 3 distinct tumor-related elements: extracellular macromolecules, extracellular vesicles, and circulating tumor cells. Investigations into these 3 biological classifications span the range of locales for tumor-specific biomarker discovery, and combined, have the potential to significantly impact GBM diagnosis, monitoring for treatment response, and surveillance for recurrence. This review highlights the recent advancements in the development of biomarkers and their efficacy for the detection of GBM.

Effectiveness of minocycline in acute white matter injury after intracerebral hemorrhage.

OBJECTIVE Intracerebral hemorrhage (ICH) is a fatal disease with high morbidity and mortality, which may be followed by white matter injury (WMI) due to the local oxidizing reaction induced by iron (Fe). In this study, the authors examined the effect of the tetracycline antibiotic minocycline on Fe-induced WMI and c-Jun N-terminal kinase (JNK) activation in rats. METHODS Thirty-six male Sprague-Dawley rats underwent an intracaudate injection of saline, Fe, or Fe + minocycline. Another 36 rats had an intracaudate injection of autologous blood and were treated with minocycline or vehicle (saline). Biomarkers of both WMI and JNK activation were examined. RESULTS In the Fe-injection group, minocycline suppressed WMI labeled by ß-amyloid precursor protein (ß-APP) and degraded myelin basic protein (dMBP)/MBP ratio. Protein levels of phosphorylated-JNK were increased after Fe injection, and could be suppressed by minocycline treatment. In the autologous blood-injection group, ß-APP and dMBP/MBP levels increased in the ipsilateral site compared with the contralateral site, which could be suppressed by 7 days of minocycline intervention. CONCLUSIONS Iron plays a critical role in WMI after ICH, which can be suppressed by minocycline through reducing the damage induced by Fe.

Possible role of antioxidative capacity of (-)-epigallocatechin-3-gallate treatment in morphological and neurobehavioral recovery after sciatic nerve crush injury.

OBJECTIVE This study examined the capacity of the major polyphenolic green tea extract (-)-epigallocatechin-3-gallate (EGCG) to suppress oxidative stress and stimulate the recovery and prompt the regeneration of sciatic nerve after crush injury. METHODS Adult male Wistar rats were randomly assigned to one of 4 groups: 1) Naïve, 2) Sham (sham injury, surgical control group), 3) Crush (sciatic nerve crush injury treated with saline), and 4) Crush+EGCG (sciatic nerve crush injury treated with intraperitoneally administered EGCG, 50 mg/kg). All animals were tested for motor and sensory neurobehavioral parameters throughout the study. Sciatic nerve and spinal cord tissues were harvested and processed for morphometric and stereological analysis. For the biochemical assays, the time points were Day 1, Day 7, Day 14, and Day 28 after nerve injury. RESULTS After sciatic nerve crush injury, the EGCG-treated animals (Crush+EGCG group) showed significantly better recovery of foot position and toe spread and 50% greater improvement in motor recovery than the saline-treated animals (Crush group). The Crush+EGCG group displayed an early hopping response at the beginning of the 3rd week postinjury. Animals in the Crush+EGCG group also showed a significant reduction in mechanical allodynia and hyperalgesia latencies and significant improvement in recovery from nociception deficits in both heat withdrawal and tail flick withdrawal latencies compared with the Crush group. In both the Crush+EGCG and Crush groups, quantitative evaluation revealed significant morphological evidence of neuroregeneration according to the following parameters: mean cross-sectional area of axons, myelin thickness in the sciatic nerve (from Week 4 to Week 8), increase of myelin basic protein concentration and gene expression in both the injured sciatic nerve and spinal cord, and fiber diameter to axon diameter ratio and myelin thickness to axon diameter ratio at Week 2 after sciatic nerve injury. However, the axon area remained much smaller in both the Crush+EGCG and Crush groups compared with the Sham and Naïve groups. The number of axons per unit area was significantly decreased in the Crush+EGCG and Crush groups compared with controls. Sciatic nerve injury produced generalized oxidative stress manifested as a significant increase of isoprostanes in the urine and decrease of the total antioxidant capacity (TAC) of the blood from Day 7 until Day 14. EGCG-treated rats showed significantly less increase of isoprostanes than saline-treated animals and also showed full recovery of TAC levels by Day 14 after nerve injury. In spinal cord tissue analysis, EGCG-treated animals showed induced glutathione reductase and suppressed induction of heme oxygenase 1 gene expression compared with nontreated animals. CONCLUSIONS EGCG treatment suppressed the crush-induced production of isoprostanes and stimulated the recovery of the TAC and was associated with remarkable alleviation of motor and sensory impairment and significant histomorphological evidence of neuronal regeneration following sciatic nerve crush injury in rats. The findings of this study suggest that EGCG can be used as an adjunctive therapeutic remedy for nerve injury. However, further investigations are needed to establish the antioxidative mechanism involved in the regenerative process after nerve injury. Only upregulation of glutathione reductase supports the idea that EGCG is acting indirectly via induction of enzymes or transcription factors.

Activation of peroxisome proliferator-activated receptor-γ by a 12/15-lipoxygenase product of arachidonic acid: a possible neuroprotective effect in the brain after experimental intracerebral hemorrhage.

OBJECTIVE In this study, the authors investigated the involvement of 15( S)-hydroxyeicosatetraenoic acid (15(S)-HETE) in the regulation of peroxisome proliferator-activated receptor-γ (PPARγ) after intracerebral hemorrhage (ICH) and its effects on hemorrhage-induced inflammatory response and oxidative stress in an experimental rodent model. METHODS To simulate ICH in a rat model, the authors injected autologous whole blood into the right striatum of male Sprague-Dawley rats. The distribution and expression of 12/15-lipoxygenase (12/15-LOX) were determined by immunohistochemistry and Western blot analysis, respectively. Immunofluorescent double labeling was used to study the cellular localization of 12/15-LOX, and 15(S)-HETE was measured with a 15(S)-HETE enzyme immunoassay kit. Neurological deficits in the animals were assessed through behavioral testing, and apoptotic cell death was determined with terminal deoxynucleotidyl transferase-mediated biotinylated dUTP nick-end labeling. RESULTS Rats with ICH had increased expression of 12/15-LOX predominantly in neurons and also in oligodendrocytes, astrocytes, and microglia. Moreover, ICH elevated production of 15(S)-HETE in the brain area ipsilateral to the blood injection. The PPARγ agonist, exogenous 15(S)-HETE, significantly increased PPARγ protein levels and increased PPARγ-regulated gene (i.e., catalase) expression in the ICH rats. Reduced expression of the gene for the proinflammatory protein nuclear factor κB coincided with decreased neuron damage and improved functional recovery from ICH. A PPARγ antagonist, GW9662, reversed the effects of exogenous 15(S)-HETE on the PPARγ-regulated genes. CONCLUSIONS The induction of 15(S)-HETE during simulated ICH suggests generation of endogenous signals of neuroprotection. The effects of exogenous 15(S)-HETE on brain hemorrhage-induced inflammatory responses and oxidative stress might be mediated via PPARγ.

Irreversible changes occurring in long-term denervated Schwann cells affect delayed nerve repair.

OBJECTIVE Multiple factors may affect functional recovery after peripheral nerve injury, among them the lesion site and the interval between the injury and the surgical repair. When the nerve segment distal to the lesion site undergoes chronic degeneration, the ensuing regeneration (when allowed) is often poor. The aims of the current study were as follows: 1) to examine the expression changes of the neuregulin 1/ErbB system during long-term nerve degeneration; and 2) to investigate whether a chronically denervated distal nerve stump can sustain nerve regeneration of freshly axotomized axons. METHODS This study used a rat surgical model of delayed nerve repair consisting of a cross suture between the chronically degenerated median nerve distal stump and the freshly axotomized ulnar proximal stump. Before the suture, a segment of long-term degenerated median nerve stump was harvested for analysis. Functional, morphological, morphometric, and biomolecular analyses were performed. RESULTS The results showed that neuregulin 1 is highly downregulated after chronic degeneration, as well as some Schwann cell markers, demonstrating that these cells undergo atrophy, which was also confirmed by ultrastructural analysis. After delayed nerve repair, it was observed that chronic degeneration of the distal nerve stump compromises nerve regeneration in terms of functional recovery, as well as the number and size of regenerated myelinated fibers. Moreover, neuregulin 1 is still downregulated after delayed regeneration. CONCLUSIONS The poor outcome after delayed nerve regeneration might be explained by Schwann cell impairment and the consequent ineffective support for nerve regeneration. Understanding the molecular and biological changes occurring both in the chronically degenerating nerve and in the delayed nerve repair may be useful to the development of new strategies to promote nerve regeneration. The results suggest that neuregulin 1 has an important role in Schwann cell activity after denervation, indicating that its manipulation might be a good strategy for improving outcome after delayed nerve repair.