Identification of key pathways and RNAs associated with skeletal muscle atrophy after spinal cord injury

Objective:This study was performed to investigate the potential key molecules involved in the progression of skeletal muscle atrophy after SCI.Methods:Based on {"type":"entrez-geo","attrs":{"text":"GSE21497","term_id":"21497"}}GSE21497 dataset, the DEmRNAs and DElncRNAs were screened after differentially expressed analysis. Then the enrichment analyses were performed on DEmRNAs. Then the PPI network and ceRNA network were constructed. Finally, the DGIdb was utilized to predict drug-gene interactions.Results:A total of 412 DEmRNAs and 21 DElncRNAs were obtained. The DEmRNAs were significantly enriched in MAPK signaling pathway and FoxO signaling pathway. In addition, UBE2D1, JUN, and FBXO32 had higher node degrees in PPI network, and the top 20 genes with high degree were significantly enriched in FoxO signaling pathway and Endometrial cancer. Moreover, FOXO3 was regulated by hsa-miR-1207-5p and hsa-miR-1207-5p was regulated by lncRNA RP11-253E3.3 in ceRNA network. Finally, 37 drug-gene interactions were obtained based on the 26 genes in ceRNA network.Conclusion:UBE2D1, JUN, and FBXO32 are likely to be related to the progression of skeletal muscle atrophy after SCI, and activating of MAPK signaling pathway, Endometrial cancer and FoxO signaling pathway may induce skeletal muscle inflammation, apoptosis, autophagy and atrophy after SCI. Moreover, RP11-253E3.3-hsa-miR-1207-5p-FOXO3 axis may be a promising therapeutic target for skeletal muscle atrophy after SCI.     

Reactions of the rat musculoskeletal system to compressive spinal cord injury (SCI) and whole body vibration (WBV) therapy

Traumatic spinal cord injury (SCI) causes a loss of locomotor function with associated compromise of the musculo-skeletal system. Whole body vibration (WBV) is a potential therapy following SCI, but little is known about its effects on the musculo-skeletal system. Here, we examined locomotor recovery and the musculo-skeletal system after thoracic (T7-9) compression SCI in adult rats. Daily WBV was started at 1, 7, 14 and 28 days after injury (WBV1-WBV28 respectively) and continued over a 12-week post-injury period. Intact rats, rats with SCI but no WBV (sham-treated) and a group that received passive flexion and extension (PFE) of their hind limbs served as controls. Compared to sham-treated rats, neither WBV nor PFE improved motor function. Only WBV14 and PFE improved body support. In line with earlier studies we failed to detect signs of soleus muscle atrophy (weight, cross sectional diameter, total amount of fibers, mean fiber diameter) or bone loss in the femur (length, weight, bone mineral density). One possible explanation is that, despite of injury extent, the preservation of some axons in the white matter, in combination with quadripedal locomotion, may provide sufficient trophic and neuronal support for the musculoskeletal system.     

Sensory function above lesion level in spinal cord injury patients with and without pain

Patients with spinal cord injury (SCI) may or may not develop central neuropathic pain despite having cord lesions of apparently the same site, extension and nature. The consequences of the cord lesion in the central nervous system and the mechanisms underlying pain are unclear. In this study, we examined sensory detection and pain thresholds above injury level in 17 SCI patients with central neuropathic pain, in 18 SCI patients without neuropathic pain, and in 20 control subjects without injury and pain. The SCI pain group had significantly higher cold and warm detection thresholds compared with the SCI pain free group and controls and higher tactile detection thresholds compared with the SCI pain free group. No difference in pain or pain tolerance thresholds was seen among pain and pain free SCI patients. These data suggest changes in somatosensory function in dermatomes rostral to the segmental injury level linked to the presence of central neuropathic pain in SCI patients. The results are discussed in relation to current concepts of pain inhibitory and facilitating systems.     

Single session exercises and concurrent functional electrical stimulation are more effective on muscles’ force generation than only exercises in spinal cord injured persons: a feasibility study

Objectives:To evaluate impact of first therapy session, containing functional electrical stimulation (FES) and therapeutic exercises (TE) on erector spinae (ES) and rectus abdominis (RA) force generation in persons with spinal cord injury (SCI).Methods:Five men with SCI were divided in two groups - FES+TE received concurrent FES on ES and RA and TE, TE only TE. Participants performed exercises for improving sitting balance and posture. Muscles’ electrical activity was evaluated by electromyography; amplitude (AEMG) and median frequency (MF) were used for analysis.Results:AEMG of ES left (L) increased 292.9% (g=-0.92), right (R) 175% (g=-1.01), RA L 314.3% (g=-0,81, P<0.05), R 266.7% (g=-0.08) in FES+TE. AEMG of ES L increased 47.6% (g=-0.46), R 96.4% (g=-0.95); RA L 7.1% (g=-0.97), but R decreased 6.7% (g=0.12) in TE. MF of ES L increased 108.5% (g=-0.74), R 184% (g=-1.25); RA L 886.7% (g=3-05, P<0.05), R 817.6% (g=-2.55, P<0.05) in FES+TE. MF of ES L increased 95.2% (g=-1.02), R 161.4% (g=-1.64); RA L 3,2% (g=-0.06), R 30.8% (g=-0.46) in TE.Conclusions:In SCI persons, single session exercises and concurrent functional electrical stimulation may be more effective on muscles` force generation than only exercises. However, replication of the results is needed before clinical implementation.     

Between-day reliability of MyotonPRO for the non-invasive measurement of muscle material properties in the lower extremities of patients with a chronic spinal cord injury

Measuring the muscle properties of patients with spinal cord injuries (SCIs) is important to better understand their biomechanical features. In this study, we sought to evaluate the between-day reliability of MyotonPRO, a handheld device that can measure muscle mechanical properties, and assess whether it is reliable to measure muscle properties over time in patients with SCI. Thirteen men with complete SCIs (age 53.9 ± 6.3 years, height 171.0 ± 5.2 cm, weight 66.1 ± 5.8 kg), and injury levels ranging from L1 to T12, were enrolled. Oscillation frequency; logarithmic decrement; dynamic stiffness; mechanical stress relaxation time; and creep of the biceps femoris, medial and lateral gastrocnemius, rectus femoris, tibialis anterior, and Achilles tendon were measured on consecutive days using MyotonPRO. The intraclass coefficient for most muscles and the Achilles tendon ranged from 0.53 to 0.99 for all parameters. The percentage standard error of the measurement for many parameters in most muscles and the Achilles tendon was less than 10%. Bland-Altman analysis showed a high agreement for all mechanical properties. No significant differences were observed in any muscle or Achilles tendon properties between days (all p > 0.05). These results indicate that the MyotonPRO is reliable for between-day measurements of the mechanical properties of lower limb muscles and Achilles tendon in patients with SCI.     

Time course changes to structural,mechanical and material properties of bone in rats after complete spinal cord injury

Objective:Characterise the spatiotemporal trabecular and cortical bone responses to complete spinal cord injury (SCI) in young rats.Methods:8-week-old male Wistar rats received T9-transection SCI and were euthanised 2-, 6-, 10- or 16-weeks post-surgery. Outcome measures were assessed using micro-computed tomography, mechanical testing, serum markers and Fourier-transform infrared spectroscopy.Results:The trabecular and cortical bone responses to SCI are site-specific. Metaphyseal trabecular BV/TV was 59% lower, characterised by fewer and thinner trabeculae at 2-weeks post-SCI, while epiphyseal BV/TV was 23% lower with maintained connectivity. At later-time points, metaphyseal BV/TV remained unchanged, while epiphyseal BV/TV increased. The total area of metaphyseal and mid-diaphyseal cortical bone were lower from 2-weeks and between 6- and 10-weeks post-SCI, respectively. This suggested that SCI-induced bone changes observed in the rat model were not solely attributable to bone loss, but also to suppressed bone growth. No tissue mineral density differences were observed at any time-point, suggesting that decreased whole-bone mechanical properties were primarily the result of changes to the spatial distribution of bone.Conclusion:Young SCI rat trabecular bone changes resemble those observed clinically in adult and paediatric SCI, while cortical bone changes resemble paediatric SCI only.     

The connection between spinal cord and notochord in Amphioxus (Branchiostoma lanceolatum)

Summary Silver impregnation of nerves, histochemical reactions for acetylcholinesterase, and electron microscopy reveal an efferent innervation of the notochord in amphioxus. Extensions of the notochordal lamellae end in groups (the notochordal horns) just below the ventro-lateral surface of the spinal cord where they are opposed to large nerve terminals originating as short collaterals of axons running longitudinally in the nerve cord. This neurochordal junction resembles an ordinary neuro-muscular junction in several respects and is interpreted as a part of the muscular system found in the notochord itself. Acknowledgement. The author is indebted to the staffs at the Marine laboratory in Plymouth and the Biological station at Helgoland for supply of material. The expert advices and criticism of Q. Bone, Ph. D., Plymouth, and Dr. U. Welsch, Kiel, are also greatly appreciated.     

Spinal neuropeptide expression and neuropathic behavior in the acute and chronic phases after spinal cord injury: Effects of progesterone administration

Patients with spinal cord injury (SCI) develop chronic pain that severely compromises their quality of life. We have previously reported that progesterone (PG), a neuroprotective steroid, could offer a promising therapeutic strategy for neuropathic pain. In the present study, we explored temporal changes in the expression of the neuropeptides galanin and tyrosine (NPY) and their receptors (GalR1 and GalR2; Y1R and Y2R, respectively) in the injured spinal cord and evaluated the impact of PG administration on both neuropeptide systems and neuropathic behavior. Male rats were subjected to spinal cord hemisection at T13 level, received daily subcutaneous injections of PG or vehicle, and were evaluated for signs of mechanical and thermal allodynia. Real time PCR was used to determine relative mRNA levels of neuropeptides and receptors, both in the acute (1 day) and chronic (28 days) phases after injury. A significant increase in Y1R and Y2R expression, as well as a significant downregulation in GalR2 mRNA levels, was observed 1 day after SCI. Interestingly, PG early treatment prevented Y1R upregulation and resulted in lower NPY, Y2R and GalR1 mRNA levels. In the chronic phase, injured rats showed well-established mechanical and cold allodynia and significant increases in galanin, NPY, GalR1 and Y1R mRNAs, while maintaining reduced GalR2 expression. Animals receiving PG treatment showed basal expression levels of galanin, NPY, GalR1 and Y1R, and reduced Y2R mRNA levels. Also, and in line with previously published observations, PG-treated animals did not develop mechanical allodynia and showed reduced sensitivity to cold stimulation. Altogether, we show that SCI leads to considerable changes in the spinal expression of galanin, NPY and their associated receptors, and that early and sustained PG administration prevents them. Moreover, our data suggest the participation of galaninergic and NPYergic systems in the plastic changes associated with SCI-induced neuropathic pain, and further supports the therapeutic potential of PG- or neuropeptide-based therapies to prevent and/or treat chronic pain after central injuries.     

Transplantation of mature adipocyte-derived dedifferentiated fat cells promotes locomotor functional recovery by remyelination and glial scar reduction after spinal cord injury in mice

Mature adipocyte-derived dedifferentiated fat cells (DFAT) have a potential to be useful as new cell-source for cell-based therapy for spinal cord injury (SCI), but the mechanisms remain unclear. The objective of this study was to examine whether DFAT-induced functional recovery is achieved through remyelination and/or glial scar reduction in a mice model of SCI. To accomplish this we subjected adult female mice (n = 22) to SCI. On the 8th day post-injury locomotor tests were performed, and the mice were randomly divided into two groups (control and DFAT). The DFAT group received stereotaxic injection of DFAT, while the controls received DMEM medium. Functional tests were conducted at repeated intervals, until the 36th day, and immunohistochemistry or staining was performed on the spinal cord sections. DFAT transplantation significantly improved locomotor function of their hindlimbs, and promoted remyelination and glial scar reduction, when compared to the controls. There were significant and positive correlations between promotion of remyelination or/and reduction of glial scar, and recovery of locomotor function. Furthermore, transplanted DFAT expressed markers for neuron, astrocyte, and oligodendrocyte, along with neurotrophic factors, within the injured spinal cord. In conclusion, DFAT-induced functional recovery in mice after SCI is probably mediated by both cell-autonomous and cell-non-autonomous effects on remyelination of the injured spinal cord.     

Transplanted neural progenitor cells expressing mutant NT3 promote myelination and partial hindlimb recovery in the chronic phase after spinal cord injury

Neutrotrophin-3 (NT3) plays a protective role in injured central nervous system tissues through interaction with trk receptors. To enhance the regeneration of damaged tissue, a combination therapy with cell transplantation and neurotrophins has been under development. We examined whether the transplantation of neural progenitor cells (NPCs) secreting NT3/D15A, a multi-neurotrophin with the capacity to bind both trkB and trkC, would enhance the repair of damaged tissues and the functional recovery in a chronic phase of spinal cord injury. The cultured NPCs with lentiviral vector containing either GFP or NT3/D15A were transplanted into the contused spinal cord at 6 weeks after the initial thoracic injury. Eight weeks after the transplantation, the NT3/D15A transplants displayed better survival than the GFP transplants, and they exhibited enhanced myelin formation and partial improvement of hindlimb function. Our study revealed that NT3/D15A produced positive effects in injured spinal cords even in the chronic phase. These effects suggest an enhanced neurotrophin-trk signaling by NT3/D15A.     

Variability of the fatigue response of paralyzed skeletal muscle in relation to the time after spinal cord injury: mechanical and electrophysiological characteristics

The aim of this study was to determine the effect of the time after spinal cord injury (less than and greater than 10 months) on the mechanical and electrophysiological characteristics of muscle fatigue of the paralyzed electrically stimulated quadriceps muscle. Morphologically and histochemically, a relationship was observed between muscle fatigue and the delay from injury, revealing a critical period of enzymatic turning and a maximum peak of atrophy around the 10th month after the injury, followed by a long-term stabilization. Knee-torque output and M-wave variables (amplitude, latency, duration, and root mean square, RMS) of two muscular heads of the quadriceps were recorded in 19 paraplegic patients during a 120-s isometric contraction. The fatiguing muscle contraction was elicited by supramaximal continuous 20-Hz electrical stimulation. Compared to the chronic group, the acutely paralyzed group showed a greater resistance to fatigue (amount and rate of force decline, P < or = 0.01), smaller alterations of the M-wave amplitude and RMS, and a limited decrease of the muscle fiber conduction velocity (P < 0.05). Mechanical and electrophysiological changes during fatigue provided a clear functional support of the transformation of skeletal muscle under the lesion and of the existence of a critical period of muscular turn. In conclusion, when considering the artificial restoration of motor function, the evolution of the endurance and force-generating capabilities of the muscle actuator must be taken into account, particularly when tasks require important safety conditions (e.g., standing and walking).     

More attention on glial cells to have better recovery after spinal cord injury

Functional improvement after spinal cord injury remains an unsolved difficulty. Glial scars, a major component of SCI lesions, are very effective in improving the rate of this recovery. Such scars are a result of complex interaction mechanisms involving three major cells, namely, astrocytes, oligodendrocytes, and microglia. In recent years, scientists have identified two subtypes of reactive astrocytes, namely, A1 astrocytes that induce the rapid death of neurons and oligodendrocytes, and A2 astrocytes that promote neuronal survival. Moreover, recent studies have suggested that the macrophage polarization state is more of a continuum between M1 and M2 macrophages. M1 macrophages that encourage the inflammation process kill their surrounding cells and inhibit cellular proliferation. In contrast, M2 macrophages promote cell proliferation, tissue growth, and regeneration. Furthermore, the ability of oligodendrocyte precursor cells to differentiate into adult oligodendrocytes or even neurons has been reviewed. Here, we first scrutinize recent findings on glial cell subtypes and their beneficial or detrimental effects after spinal cord injury. Second, we discuss how we may be able to help the functional recovery process after injury.     

CSPGs在大鼠脊髓损伤后的表达及其与GFAP的关系

目的:观察脊髓损伤后CSPGs的表达及其与GFAP的关系。方法:成年雄性SD大鼠25只,随机分为对照组和损伤组,损伤组分脊髓挤压损伤后0h、72h、1w、4w组,运用免疫荧光双重染色方法观察CSPGs与GFAP的表达。结果:挤压伤后损伤部位的CSPGs和GFAP的表达均增高,但二者的变化趋势并不一样。其中CSPGs从损伤后表达开始增高,此后一直增加,并在1w至4w时逐渐稳定,主要分布逐渐集中于损伤部位;星形胶质细胞的免疫反应也逐渐增加,其分布逐渐集中于损伤区域的边缘,逐渐形成胶质瘢痕界膜。损伤1w至4w,损伤区域内几乎没有了星形胶质细胞表达,但仍留有大量的CSPGs。结论:早期抑制星形胶质细胞分泌CSPGs,可以防止在损伤部位沉积大量的CSPGs,从而减小其对再生纤维的抑制作用。     

Role of IL‐15 in spinal cord and sciatic nerve after chronic constriction injury: regulation of macrophage and T‐cell infiltration

The release of inflammatory mediators from immune and glial cells either in the peripheral or CNS may have an important role in the development of physiopathological processes such as neuropathic pain. Microglial, then astrocytic activation in the spinal cord, lead to chronic inflammation, alteration of neuronal physiology and neuropathic pain. Standard experimental models of neuropathic pain include an important peripheral inflammatory component, which involves prominent immune cell activation and infiltration. Among potential immunomodulators, the T‐cell cytokine interleukin‐15 (IL‐15) has a key role in regulating immune cell activation and glial reactivity after CNS injury. Here we show, using the model of chronic constriction of the sciatic nerve (CCI), that IL‐15 is essential for the development of the early inflammatory events in the spinal cord after a peripheral lesion that generates neuropathic pain. IL‐15 expression in the spinal cord was identified in both astroglial and microglial cells and was present during the initial gliotic and inflammatory (NFκB) response to injury. The expression of IL‐15 was also identified as a cue for macrophage and T‐cell activation and infiltration in the sciatic nerve, as shown by intraneural injection of the cytokine and activity blockage approaches. We conclude that the regulation of IL‐15 and hence the initial events following its expression after peripheral nerve injury could have a future therapeutic potential in the reduction of neuroinflammation.     

Repeated topical application of growth hormone attenuates blood-spinal cord barrier permeability and edema formation following spinal cord injury: an experimental study in the rat using Evans blue, ([125])I-sodium and lanthanum tracers

Summary.  The neuroprotective efficacy of growth hormone on a focal spinal cord trauma induced alteration in the blood-spinal cord barrier (BSCB) and edema formation was examined in a rat model. Under Equithesin anaesthesia, one segment laminectomy was done over the T10–11 segments. Spinal cord injury was produced by making an incision into the right dorsal horn of the T10–11 segments (2 mm deep and 4 mm long). The animals were allowed to survive 5 h after injury. Highly purified rat growth hormone [rGH, 25 μl of a 1 μg/ml solution) was applied over 10 sec topically on the exposed surface of the spinal cord 30 min before injury. The identical doses of the rGH were repeated 0 min, 30 min, 60 min, 120 min, 180 min and 240 min following injury. Saline (0.9% NaCl) treated traumatised rats at identical intervals served as controls. Traumatised rats treated with saline exhibited marked edema formation and extravasation of Evans blue and ^[125]Iodine tracers in the spinal cord. At the ultrastructural level, perivascular edema and exudation of lanthanum across the endothelial cells was quite frequent in the spinal cord. Pretreatment with rGH significantly attenuated the edema formation and the extravasation of tracers in the spinal cord. In these rats, perivascular edema and infiltration of lanthanum across the endothelial cells was not much evident. These observations show that the rGH has the capacity to reduce the early manifestations of microvascular permeability disturbances and edema formation following trauma and further suggest a possible therapeutic potential of the hormone for the treatment of spinal cord injuries. Received July 3, 2001 Accepted August 6, 2001 Published online July 31, 2002