Spinal Cord Transection Research Articles

Neurological recovery after traumatic spinal cord injury: prognostic value of magnetic resonance.

Retrospective observational study. Assess the relationship between Magnetic Resonance (MR) image patterns and neurological recovery in patients with Traumatic Spinal Cord Injury (TSCI). Spinal cord injury unit in Spain. Patients admitted for acute TSCI between January 2010 and December 2018 with a MR exam performed in the acute phase were selected. Five patterns were established: normal, single-level edema, multilevel edema, hemorrhage, and spinal cord transection. Comparisons between the ASIA Injury Severity (AIS) score and Motor Index (MI) at admission and at discharge were made. Collected 296 patients. Normal and cord transection patterns were excluded due to the low number of cases. Single-level edema pattern was primarily observed in cases with incomplete injuries, hemorrhage pattern in complete injuries, and multilevel edema pattern at similar percentages in complete and incomplete lesions. Improvement of the AIS score was found in 40.9% of single-level edema, 20.2% of multilevel edema, and 19.0% of hemorrhage (p = 0.042) patterns. By excluding the AIS grade D from the analyses, the figures increased to 70.3%, 52.2%, and 19.4% respectively (p < 0.001). This significant relationship was confirmed by multivariate analysis, although it was not as relevant as the examination according to ASIA-ISCoS performed at admission (p = 0.005 vs p < 0.001). Mean variation of the MI was also significantly different (p < 0.001) between the three groups: 22.6 ± 21.4 for single-level edema, 16.9 ± 21.1 for multilevel edema, and 4.5 ± 8.4 for hemorrhage. MR injury patterns observed at the acute phase are associated with the possibility of improvement of the AIS score and MI.

Rewired glycosylation activity promotes scarless regeneration and functional recovery in spiny mice after complete spinal cord transection.

Regeneration of adult mammalian central nervous system (CNS) axons is abortive, resulting in inability to recover function after CNS lesion, including spinal cord injury (SCI). Here, we show that the spiny mouse (Acomys) is an exception to other mammals, being capable of spontaneous and fast restoration of function after severe SCI, re-establishing hind limb coordination. Remarkably, Acomys assembles a scarless pro-regenerative tissue at the injury site, providing a unique structural continuity of the initial spinal cord geometry. The Acomys SCI site shows robust axon regeneration of multiple tracts, synapse formation, and electrophysiological signal propagation. Transcriptomic analysis of the spinal cord following transcriptome reconstruction revealed that Acomys rewires glycosylation biosynthetic pathways, culminating in a specific pro-regenerative proteoglycan signature at SCI site. Our work uncovers that a glycosylation switch is critical for axon regeneration after SCI and identifies β3gnt7, a crucial enzyme of keratan sulfate biosynthesis, as an enhancer of axon growth.

Bioengineered Zinc Oxide Nanoparticle-Loaded Hydrogel for Combinative Treatment of Spinal Cord Transection.

Spinal cord injury (SCI) is one of the most destructive diseases. The neuroinflammation microenvironment needs comprehensive mitigation of damages. Thus, regulation of local, microenvironment drugs could be a potential effective treatment. However, clinical studies on SCI with common treatment have reported it to cause systemic toxicity and side effects. Zinc oxide nanoparticles (ZnONPs) have been widely reported to have satisfying anti-inflammation function. Furthermore, green synthesis procedures can improve the capability and possible utilization of ZnONPs. However, the efficient administration and underlying mechanism of ZnONPs in SCI treatment remain unclear. Herein, an innovative approach was built by utilizing ZnONPs loaded in a skeletal muscle-derived adhesive hydrogel (ZnONPs-Gel). Different from the systemic application of ZnONPs, the local administration of ZnONPs-Gel offered the ZnONPs-loaded extracellular matrix with beneficial biocompatibility to the injured spinal cord, thereby promoting effective function recovery. Mechanistically, the ZnONPs-Gel treatment not only markedly reduced ROS production but also decreased apoptosis in the injured spinal cord. Therefore, the strategy based on local administration of the ZnONPs-Gel in the early stage of SCI may be an effective therapeutic treatment.

Complete traumatic transection of thoracic spinal cord in a pediatric patient

With pediatric spinal cord injuries themselves being an infrequent event worldwide, complete transection of the spinal cord forms an extremely small subset of the same. Moreover, complete transection of spinal cord without the concurrent presence of vertebral compression fractures has rarely been reported in the pediatric age group. We hereby present a pediatric case with traumatic brain injury as well as complete thoracic spinal cord transection and probe the possible mechanisms that contribute to these injuries in the pediatric age group. We also discuss the challenges faced in the diagnostic evaluation as well as the therapeutic dilemmas in the given scenario due to the multiple ongoing issues.

Inhibition of central axon regeneration: perspective from chondroitin sulfate proteoglycans in lamprey spinal cord injury.

Inhibition of central axon regeneration: perspective from chondroitin sulfate proteoglycans in lamprey spinal cord injury.

A decellularized spinal cord extracellular matrix-gel/GelMA hydrogel three-dimensional composite scaffold promotes recovery from spinal cord injury via synergism with human menstrual blood-derived stem cells.

Spinal cord injury (SCI), as a serious disabling disease, is still haunted by lacking of effective treatments. We previously found that transplantation of menstrual blood-derived mesenchymal stem cells (MenSCs) promoted axon regeneration in rats with SCI, while the abominable microenvironment after the SCI inhibited the survival of stem cells after transplantation. Biomaterials can support the activity of stem cells and accelerate the functional reconstruction of the injured spinal cord. In this study, we constructed a novel composite scaffold consisting of the decellularized spinal cord extracellular matrix-gel (DSCG) and the GelMA hydrogel, which harbored high water retention, wettability, degradability and soft mechanical property. In vitro, the DSCG/GelMA composite scaffold provided a dual bionic microenvironment with optimized bioactive components and favorable microstructures for the adhesion, proliferation and differentiation of MenSCs. After that, we prepared MenSC-encapsulated DSCG/GelMA composite scaffolds to bridge the 2 mm gap in rats with completely transected SCI. The in vivo results showed that the combined use of the DSCG/GelMA composite scaffold with MenSCs improved the motor function, reduced the inflammatory response, promoted neuronal differentiation, and inhibited the proliferation of reactive astrocytes after spinal cord injury. Altogether, our study provided a promising novel therapeutic option of using bioactive materials synergistic with stem cells for the treatment of SCI.

Post Traumatic Spinal Cord Transsection – A Case Series

Post Traumatic Spinal Cord Transsection – A Case Series

Spinal Cord Transection In Xenopus laevis Tadpoles.

Spinal cord injury (SCI) is a permanent affliction, which affects the central nervous system (CNS) motor and sensory nerves, resulting in paralysis beneath the injury site. To date, there is no functional recovery therapy for SCI, and there is a lack of clarity regarding the many complexes and dynamic events occurring after SCI. Many non-mammalian organisms can regenerate after severe SCI, such as teleost fishes, urodele amphibians, and larval stages of anuran amphibians, including Xenopus laevis tadpoles. These are bona fide model organisms to study and understand the response to SCI and the mechanisms underlying successful regenerative processes. This type of research can lead to the identification of potential targets for SCI therapeutic intervention. This article describes how to perform Xenopus laevis tadpole spinal cord transection, including husbandry, surgery, postsurgery care, and functional test evaluation. This injury method can be applied for elucidating the different steps of spinal cord regeneration by studying the cellular, molecular, and genetic mechanisms, as well as histological and functional evolution after SCI and during spinal cord regeneration.

Cervical Spinal Cord Transection (SCT) Increases Gastric Compliance in Anesthetized Rats

Abstract Spinal cord injury (SCI) can markedly alter the autonomic nervous system’s functions. It immediately causes autonomic and somatic hypo- or arreflexia, a state known as spinal shock. SCI determines the enhancement of two gastric reflexes that appear in normal conditions: the receptive and adaptative reflexes. Furthermore, this study also tried to evaluate the causes that led to such modifications: either vagal control, nitric oxide (NO)-pathways or intestine-intestinal reflexes. Male Wistar rats (N=25) were subjected to laminectomy (Sham group) or laminectomy + complete Spinal Cord Transection (SCT), between C7 and T1 vertebrae under anesthesia (SCT group). Before the surgery, the rats had water and food ad libitum; after the surgery, rats were fasted for 24 hours, still having access to water. The next day, all animals were subjected to a catheterism of their right carotid artery, a tracheostomy and a flexible balloon introduction down to the stomach’s fundix region, also under anesthesia. Rats were connected to a Power-Lab® system, via a pressure transducer (in order to measure the arterial pressure – MAP - and the heart rate - HR), and to a modified Plethysmometer (in order to measure the fundical gastric volume - GV variation). Vagal control was studied via cervical vagotomy; NO-mediation - via NO synthesis inhibitors (L-NAME); intestinointestinal reflexes - by using laxatives (Lactulone). Statistical analysis revealed, in some cases, that GV is significantly (p&lt;0.05) augmented in SCT rats (2,4±0,09; 3,1±0,05; 3,7±0,06 ml) than in Sham (2,2±0,12; 2,9±0,12; 3,3±0,15 ml). Nevertheless, MAP and HR, were subsequently lower (p&lt;0.05) in SCT (63,5±21,1mm Hg; 227,1±25,2 BPM) than in the control group (88,2±14,4mm Hg; 427,0±19,2 BPM). In summary, the increase of GV in SCT, seems to involve vagal pathways and/or NO-mediation, but still not neglecting the colic-gastric reflexes.

Dual-Pseudorabies Viral Tracing for Spinal Tyrosine Hydroxylase Interneurons Involved in Segmental Micturition Reflex Circuitry in Spinal Cord Injured Rats.

Traumatic spinal cord injury (SCI) often leads to urinary dysfunction. Although an involuntary micturition reflex can be established to elicit voiding with time, complications arise in the form of bladder hyper-reflexia and detrusor-sphincter dyssynergia that cause incontinence and inefficient expulsion of urine. To date, the neuronal mechanisms that underlie regulation of micturition after SCI are not well understood. We recently observed an increase of a population of tyrosine hydroxylase (TH)+ cells in the rat lumbosacral cord post-SCI, which contribute to the sustention of a low level of dopamine that modulates the recovered bladder reflex. To identify whether spinal TH+ cells are involved in the micturition reflex pathway post-SCI, two isoforms of the trans-synaptic retrograde tracer, pseudorabies virus encoding green fluorescent protein (GFP; PRV-152) or red fluorescent protein (RFP; PRV-614), were injected into the bladder detrusor or the external urethral sphincter (EUS), respectively, 3 weeks after a spinal cord transection at the 10th thoracic level (T10) in rats. Immunohistochemistry was performed to examine infected TH+ cells in the caudal cord at both 48 and 72 h post-injection. As a result, double-labeled TH+/GFP+ and TH+/RFP+ cells could be found in the superficial dorsal horn, parasympathetic nuclei, and dorsal gray commissure (lamina X) at both time points. More importantly, a shared population of TH+ interneurons (TH+/GFP+/RFP+) exists between bladder and EUS circuitry. These results suggest that spinal TH+ interneurons may coordinate activity of the bladder and EUS that occurs during micturition reflexes post-SCI.

Administration of High-Dose Methylprednisolone Worsens Bone Loss after Acute Spinal Cord Injury in Rats.

The administration of high-dose methylprednisolone (MP) for 24–48 h after traumatic spinal cord injury (SCI) has been shown to improve functional recovery. The known adverse effects of MP on skeletal muscle and the immune system, though, have raised clinically relevant safety concerns. However, the effect of MP administration on SCI-induced bone loss has not been evaluated to date. This study examined the adverse effects of high-dose MP administration on skeletal bone after acute SCI in rodents. Male rats underwent spinal cord transection at T3–T4, which was followed by an intravenous injection of MP and subsequent infusion of MP for 24 h. At 2 days, animals were euthanized and hindlimb bone samples were collected. MP significantly reduced bone mineral density (−6.7%) and induced deterioration of bone microstructure (trabecular bone volume/tissue volume, −18.4%; trabecular number, −19.4%) in the distal femur of SCI rats. MP significantly increased expression in the hindlimb bones of osteoclastic genes receptor activator of nuclear factor-κB ligand (RANKL; +402%), triiodothyronine receptor auxiliary protein (+32%), calcitonin receptor (+41%), and reduced osteoprotegerin/RANKL ratio (−72%) compared to those of SCI-vehicle animals. Collectively, 1 day of high-dose MP at a dose comparable to the dosing regimen prescribed to patients who qualify to receive this treatment approach with acute SCI increased loss of bone mass and integrity below the level of lesion than that of animals that had SCI alone, and was associated with further elevation in the expression of genes involved in pathways associated with osteoclastic bone resorption than that observed in SCI animals.

Slow development of bladder malfunction parallels spinal cord fiber sprouting and interneurons' loss after spinal cord transection

Neurogenic lower urinary tract dysfunction typically develops after spinal cord injury. We investigated the time course and the anatomical changes in the spinal cord that may be causing lower urinary tract symptoms following injury. Rats were implanted with a bladder catheter and external urethral sphincter electromyography electrodes. Animals underwent a large, incomplete spinal transection at the T8/9 spinal level. At 1, 2–3, and 4 weeks after injury, the animals underwent urodynamic investigations. Urodynamic investigations showed detrusor overactivity and detrusor-sphincter-dyssynergia appearing over time at 3–4 weeks after injury. Lower urinary tract dysfunction was accompanied by an increase in density of C-fiber afferents in the lumbosacral dorsal horn. CRF-positive Barrington's and 5-HT-positive bulbospinal projections drastically decreased after injury, with partial compensation for the CRF fibers at 3–4 weeks. Interestingly, a decrease over time was observed in the number of GABAergic neurons in the lumbosacral dorsal horn and lamina X, and a decrease of glutamatergic cells in the dorsal horn. Detrusor overactivity and detrusor-sphincter-dyssynergia might therefore arise from a discrepancy in inhibitory/excitatory interneuron activity in the lumbosacral cord as well as input changes which develop over time after injury. The processes point to spinal plastic changes leading to malfunction of the important physiological pathway of lower urinary tract control.

In vivo monitoring of calcium ions in rat cerebrospinal fluid using an all-solid-state acupuncture needle based potentiometric microelectrode

Acupuncture needles are regarded as ideal materiel for the development of microelectrodes for in vivo sensing. In this work, an all-solid-state ion-selective microelectrode (ISμE) has been developed by coating a calcium ion-selective membrane on an acupuncture needle tip with a diameter of less than 80 μm, which is modified with poly(3,4-ethylenedioxythiophene)-poly(sodium 4-styrenesulfonate) as solid contact. The proposed Ca2+-ISμE shows a Nernstian response toward Ca2+ in the range from 1.0 × 10−6 to 3.1 × 10−3 M with a slope of 30.8 ± 0.9 mV/decade (R2 = 0.999), and the detection limit is 1.2 × 10−7 M. The Ca2+-ISμE has been used for in vivo monitoring of the calcium changes in rat cerebrospinal fluid (CSF) under the injury of spinal cord transection. The results demonstrate that the calcium concentration in CSF increases sharply from the normal level of 20.6 ± 1.72 μM (n = 3) to 133.2 ± 7.63 μM (n = 3) with a severe fluctuation after spinal cord damage. Thus, the proposed Ca2+-ISμE is available for in vivo monitoring of calcium ions with high temporal resolution and flexibility. The detection system can be extended to measure other ions in CSF by changing different ion-selective membranes.

Controlled Semi-Automated Lased-Induced Injuries for Studying Spinal Cord Regeneration in Zebrafish Larvae.

Zebrafish larvae possess a fully functional central nervous system (CNS) with a high regenerative capacity only a few days after fertilization. This makes this animal model very useful for studying spinal cord injury and regeneration. The standard protocol for inducing such lesions is to transect the dorsal part of the trunk manually. However, this technique requires extensive training and damages additional tissues. A protocol was developed for laser-induced lesions to circumvent these limitations, allowing for high reproducibility and completeness of spinal cord transection over many animals and between different sessions, even for an untrained operator. Furthermore, tissue damage is mainly limited to the spinal cord itself, reducing confounding effects from injuring different tissues, e.g., skin, muscle, and CNS. Moreover, hemi-lesions of the spinal cord are possible. Improved preservation of tissue integrity after laser injury facilitates further dissections needed for additional analyses, such as electrophysiology. Hence, this method offers precise control of the injury extent that is unachievable manually. This allows for new experimental paradigms in this powerful model in the future.

Assessment of Swim Endurance and Swim Behavior in Adult Zebrafish.

Due to their renowned regenerative capacity, adult zebrafish are a premier vertebrate model to interrogate mechanisms of innate spinal cord regeneration. Following complete transection of their spinal cord, zebrafish extend glial and axonal bridges across severed tissue, regenerate neurons proximal to the lesion, and regain their swim capacities within 8 weeks of injury. Recovery of swim function is thus a central readout for functional spinal cord repair. Here, we describe a set of behavioral assays to quantify zebrafish motor capacity inside an enclosed swim tunnel. The goal of these methods is to provide quantifiable measurements of swim endurance and swim behavior in adult zebrafish. For swim endurance, zebrafish are subjected to a constantly increasing water current velocity until exhaustion, and time at exhaustion is reported. For swim behavior assessment, zebrafish are subjected to low current velocities and swim videos are captured with a dorsal view of the fish. Percent activity, burst frequency, and time spent against the water current provide quantifiable readouts of swim behavior. We quantified swim endurance and swim behavior in wild-type zebrafish before injury and after spinal cord transection. We found that zebrafish lose swim function after spinal cord transection and gradually regain that capacity between 2 and 6 weeks post-injury. The methods described in this study could be applied to neurobehavioral, musculoskeletal, skeletal muscle regeneration, and neural regeneration studies in adult zebrafish.

Swimming kinematics and performance of spinal transected lampreys with different levels of axon regeneration.

ABSTRACTAxon regeneration is critical for restoring neural function after spinal cord injury. This has prompted a series of studies on the neural and functional recovery of lampreys after spinal cord transection. Despite this, there are still many basic questions remaining about how much functional recovery depends on axon regeneration. Our goal was to examine how swimming performance is related to degree of axon regeneration in lampreys recovering from spinal cord transection by quantifying the relationship between swimming performance and percent axon regeneration of transected lampreys after 11 weeks of recovery. We found that while swimming speeds varied, they did not relate to percent axon regeneration. In fact, swimming speeds were highly variable within individuals, meaning that most individuals could swim at both moderate and slow speeds, regardless of percent axon regeneration. However, none of the transected individuals were able to swim as fast as the control lampreys. To swim fast, control lampreys generated high amplitude body waves with long wavelengths. Transected lampreys generated body waves with lower amplitude and shorter wavelengths than controls, and to compensate, transected lampreys increased their wave frequencies to swim faster. As a result, transected lampreys had significantly higher frequencies than control lampreys at comparable swimming velocities. These data suggest that the control lampreys swam more efficiently than transected lampreys. In conclusion, there appears to be a minimal recovery threshold in terms of percent axon regeneration required for lampreys to be capable of swimming; however, there also seems to be a limit to how much they can behaviorally recover.

Pyrrole Plasma Polymer-Coated Fibrillar Scaffold Implant: Pilot Study in Rat Spinal Cord Transection with MRI.

Despite extensive research on spinal cord injury (SCI) therapies for the recovery of motor, sensory and autonomic function, currently there are no effective treatments to completely restore tissue structure and function. In this work, a polylactic acid (PLA) fibrillar scaffold coated with pyrrole plasma polymer doped with iodine (pPPy/I), was studied as therapeutic strategy in a SCI transection model. Magnetic resonance imaging (MRI) was used to evaluate tissue response to the implant. Behavioral analysis using the BBB open-field testing was conducted to evaluate functional response. MRI analysis showed the SCI model completely disrupted tissue continuity, and diffusion indices were altered at the injury site. The animals had completely paralyzed hindlimbs and bladder control loss after injury. After 8 weeks of treatment, in contrast to control and PLA-implanted animals, PLA+pPPy/I-implanted animal had regained bladder control autonomy and frequent to consistent weight supported plantar steps and occasional coordination between forelimbs and hindlimbs. These results suggest fibrillar scaffolds coated with pPPy/I constitute a promising therapy for SCI.

Cell-adaptable dynamic hydrogel reinforced with stem cells improves the functional repair of spinal cord injury by alleviating neuroinflammation

Spinal cord injury (SCI) is one of the most challenging clinical issues. It is characterized by the disruption of neural circuitry and connectivity, resulting in neurological disability. Adipose-derived stem cells (ADSCs) serve as a promising source of therapeutic cells for SCI treatment. However, the therapeutic outcomes of direct ADSCs transplantation are limited in the presence of an inflammatory microenvironment. Herein, a cell-adaptable neurogenic (CaNeu) hydrogel was developed as a delivery vehicle for ADSCs to promote neuronal regeneration after SCI. The dynamic network of CaNeu hydrogel loaded with ADSCs provides a cell-infiltratable matrix that enhances axonal growth and eventually leads to improved motor evoked potential, hindlimb strength, and coordination of complete spinal cord transection in rats. Furthermore, the CaNeu hydrogel also establishes an anti-inflammatory microenvironment by inducing a shift in the polarization of the recruited macrophages toward the pro-regeneration (M2) phenotype. Our study showed that the CaNeu-hydrogel‒mediated ADSCs delivery resulted in significantly suppressed neuroinflammation and apoptosis, and that this phenomenon involved the PI3K/Akt signaling pathway. Our findings indicate that the CaNeu hydrogel is a valuable delivery vehicle to assist stem cell therapy for SCI, providing a promising strategy for central nervous system diseases.

Effect of electroacupuncture on urodynamics of neurogenic bladder and PACAP/cAMP/PKA signaling pathway in detrusor tissue of rats after suprasacral spinal cord injury

To observe the effect of electroacupuncture (EA) on urodynamics of neurogenic bladder and pituitary adenylate cyclase activating peptide(PACAP)/cyclic adenosine monophosphate (cAMP)/protein kinase A(PKA) signaling pathway in detrusor tissue of rats after suprasacral spinal cord injury (SCI), so as to explore its possible mechanism in improving detrusor hyperreflexia bladder function after shock stage of suprasacral SCI. Female SD rats were randomly divided into control, sham operation, model and EA groups, with 12 rats in each group. T10 spinal cord transection (SCT) was performed by surgery. Rats in the EA group were given EA (10 Hz/50 Hz, 20 min) at "Ciliao" (BL32), "Zhongji" (CV3) and "Sanyinjiao" (SP6) once daily for 7 days. After the intervention, urodynamics testing was detected in each group. HE staining was used to observe the morphological changes of bladder detrusor. The protein and mRNA expression of PACAP38 in detrusor was detected by immunohistochemistry, Western blot and real-time quantitive PCR, respectively. The contents of cAMP and PKA were determined by ELISA. Compared with the control and sham operation groups, the maximum bladder capacity and bladder com-pliance, and the protein and mRNA expression of PACAP38, and the contents of cAMP and PKA of the model group were significantly decreased (P<0.01, P<0.05), while the base pressure and leakage point pressure of bladder were significantly increased (P<0.01). After EA intervention, the above indexes were all reversed in the EA group relevant to those of the model group (P<0.01, P<0.05). EA at BL32, CV3 and SP6 can improve the bladder function in rats with bladder detrusor hyperreflexia after SCI, which may be related to its effect in activating the PACAP/cAMP/PKA signaling pathway in detrusor tissue.

Growth associated protein 43 and neurofilament immunolabeling in the transected lumbar spinal cord of lizard indicates limited axonal regeneration

Previous cytological studies on the transected lumbar spinal cord of lizards have shown the presence of differentiating glial cells, few neurons and axons in the bridge region between the proximal and distal stumps of the spinal cord in some cases. A limited number of axons (20-50) can cross the bridge and re-connect the caudal stump of the spinal cord with small neurons located in the rostral stump of the spinal cord. This axonal regeneration appears to be related to the recovery of hind-limb movements after initial paralysis. The present study extends previous studies and shows that after transection of the lumbar spinal cord in lizards, a glial-connective tissue bridge that reconnects the rostral and caudal stumps of the interrupted spinal cord is formed at 11-34 days post-injury. Following an initial paralysis some recovery of hindlimb movements occurs within 1-3 months post-injury. Immunohistochemical and ultrastructural analysis for a growth associated protein 43 (GAP-43) of 48-50 kDa shows that sparse GAP-43 positive axons are present in the proximal stump of the spinal cord but their number decreased in the bridge at 11-34 days post-transection. Few immunolabeled axons with a neurofilament protein of 200-220 kDa were seen in the bridge at 11-22 days post-transection but their number increased at 34 days and 3 months post-amputation in lizards that have recovered some hindlimb movements. Numerous neurons in the rostral and caudal stumps of the spinal cord were also labeled for GAP43, a cytoplasmic protein that is trans-located into their axonal growth cones. This indicates that GAP-43 biosynthesis is related to axonal regeneration and sprouting from neurons that were damaged by the transection. Taken together, previous studies that utilized tract-tracing technique to label the present observations confirm that a limited axonal re-connection of the transected spinal cord occurs 1-3 months post-injury in lizards. The few regenerating-sprouting axons within the bridge reconnect the caudal with the rostral stumps of the spinal cord, and likely contribute to activate the neural circuits that sustain the limited but important recovery of hind-limb movements after initial paralysis. The surgical procedures utilized in the study followed the regulations on animal care and experimental procedures under the Italian Guidelines (art. 5, DL 116/92).