Cross-clamping of the thoracic aorta. Influence of aortic shunts, laminectomy, papaverine, calcium channel blocker, allopurinol, and superoxide dismutase on spinal cord blood flow and paraplegia in baboons

Spinal cord protection in open and endovascular approaches to thoracoabdominal aortic aneurysms

Despite advancements in surgical and postoperative management, spinal cord injury has been a persistent complication of both open and endovascular repair of thoracoabdominal and descending thoracic aortic aneurysm. Spinal cord injury can be explained with an ischemia-infarction model which results in local edema of the spinal cord, damaging its structure and leading to reversible or irreversible loss of its function. Perfusion of the spinal cord during aortic procedures can be enhanced by several adjuncts which have been described with a broad variety of evidence in their support. These adjuncts include systemic hypothermia, cerebrospinal fluid drainage, extracorporeal circulation and distal aortic perfusion, segmental arteries reimplantation, left subclavian artery revascularization, and staged aortic repair. The Authors here reviewed and discussed the role of such adjuncts in preventing spinal cord injury from occurring, pinpointing current evidence and outlining future perspectives.

Thoracoabdominal Aortic Disease and Repair: JACC Focus Seminar, Part 3

Thoracoabdominal aortic disease is a rare but life-threatening condition that requires expert multidisciplinary collaborative management. Intervention is indicated in patients with symptomatic aneurysms or when an aneurysm reaches a certain threshold of diameter or rate of expansion. The strategies for spinal cord and end-organ protection have evolved over several decades, resulting in improved outcomes after repair. Open repair, although invasive, provides definitive and durable repair. Endovascular approaches are rapidly evolving, and the results with fenestrated and branched endografts are promising. Both open repair and endovascular repair require highly specialized expertise, and outcomes are best when repair is undertaken in an elective setting by a dedicated team. Patients with degenerative thoracoabdominal aortic aneurysms and chronic dissections should be followed up closely and referred for elective repair when indicated.

Spinal Stroke: Outcome Attenuation by Erythropoietin and Carbamylated Erythropoietin and Its Prediction by Sphingosine-1-Phosphate Serum Levels in Mice

Spinal strokes may be associated with tremendous spinal cord injury. Erythropoietin (EPO) improves the neurological outcome of animals after spinal cord ischemia (SCI) and its effects on ischemia-induced endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) are considered possible molecular mechanisms. Furthermore, sphingosin-1-phosphate (S1P) is suggested to correlate with SCI. In this study, the effect of recombinant human EPO (rhEPO) and carbamylated EPO (cEPO-Fc) on the outcome of mice after SCI and a prognostic value of S1P were investigated. SCI was induced in 12-month-old male mice by thoracic aortal cross-clamping after administration of rhEPO, cEPO-Fc, or a control. The locomotory behavior of mice was evaluated by the Basso mouse scale and S1P serum levels were measured by liquid chromatography-tandem mass spectrometry. The spinal cord was examined histologically and the expressions of key UPR proteins (ATF6, PERK, and IRE1a, caspase-12) were analyzed utilizing immunohistochemistry and real-time quantitative polymerase chain reaction. RhEPO and cEPO-Fc significantly improved outcomes after SCI. The expression of caspase-12 significantly increased in the control group within the first 24 h of reperfusion. Animals with better locomotory behavior had significantly higher serum levels of S1P. Our data indicate that rhEPO and cEPO-Fc have protective effects on the clinical outcome and neuronal tissue of mice after SCI and that the ER is involved in the molecular mechanisms. Moreover, serum S1P may predict the severity of impairment after SCI.

Our experience with 1000 recent thoracoabdominal aneurysm repairs, including endovascular stenting

OBJECTIVE

Managing patients with thoracoabdominal aneurysms is demanding yet fascinating, and requires a team effort. This invited talk presents lessons learned as our history with open and endovascular procedures evolved for 2578 descending and thoracoabdominal repairs over the past 20 years.

METHODS

Beginning in 1985 with an analysis of 596 traumatic aortic ruptures and the risk of spinal cord ischemia, the evolution of research and procedures for thoracoabdominal aneurysms progressed. The focus of these studies, medication trials, and procedure adjustments was on lowering the risk of spinal cord ischemia.

RESULTS

Between January 2002 and December 2021, 2578 aneurysm repairs were performed. The respective mortality rates were 6.8% and 4.0% for all patients treated. The permanent spinal cord ischemia rates were 1.3% for open descending thoracic aortas and 4.9% for open thoracoabdominal aneurysms. A detailed analysis of open and thoracoabdominal repairs showed better long-term outcomes with open repairs.

CONCLUSIONS

Through multiple randomized trials and innovations with procedures and techniques, the risk of death and spinal cord ischemia have been reduced. Long-term survival has also been improved. The pursuit of reducing the risks of descending and ascending thoracoabdominal repairs is a fascinating endeavor that has resulted in better patient outcomes. Nevertheless, this is a journey, and there will always be more room to achieve even better results.

Intravenous injection of adult human bone marrow mesenchymal stromal cells attenuates spinal cord ischemia/reperfusion injury in a murine aortic arch crossclamping model

OBJECTIVE

We sought to investigate the efficacy of human bone marrow mesenchymal stem/stromal cell (hBM-MSC) in a murine spinal cord ischemia/reperfusion (SCIR) model.

METHODS

C57BL/6J mice were subjected to SCIR by crossclamping the aortic arch and left subclavian artery for 5.5 minutes. Two hours after reperfusion, hBM-MSCs (hBM-MSC group) or phosphate-buffered saline (control group) were intravenously injected without immunosuppressant. Hindlimb motor function was assessed until day 28 after reperfusion using the Basso Mouse Scale (BMS). The lumbar spinal cord was harvested at hour 24 and day 28, and the histologic number of NeuN-positive motor neurons in 3 cross-sections of each lumbar spinal cord and the gene expression were evaluated.

RESULTS

BMS score was 0 throughout the study period in all control mice. BMS score was significantly greater in the hBM-MSC group than the control group from hour 8 (P < .05) to day 28 (P < .01). The numbers of motor neurons at hour 24 (P < .01) and day 28 (P < .05) were significantly preserved in the hBM-MSC group than the control group. mRNA expression levels of proinflammatory cytokines were significantly lower (P < .05), and those of insulin-like growth factor-1 (P < .01) and proangiogenic factors (P < .05) were significantly greater in the hBM-MSC group than the control group at hour 24.

CONCLUSIONS

hBM-MSC therapy may attenuate SCIR injury by preserving motor neurons, at least in part, through inhibition of proinflammatory cytokines and upregulation of proangiogenic factors in the reperfusion-injured spinal cord.

Effects of Ganoderma lucidum Polysaccharides on Different Pathways Involved in the Development of Spinal Cord Ischemia Reperfusion Injury: Biochemical, Histopathologic, and Ultrastructural Analysis in a Rat Model

OBJECTIVE

Inflammation and oxidative stress are 2 important factors in the emergence of paraplegia associated with spinal cord ischemia-reperfusion injury (SCIRI) after thoracoabdominal aortic surgery. Here it is aimed to investigate the effects of Ganoderma lucidum polysaccharide (GLPS) on SCIRI.

METHODS

Rats were randomly selected into 4 groups of 8 animals each: sham, ischemia, methylprednisolone, and GLPS. To research the impacts of various pathways that are efficacious in formation of SCIRI, tumor necrosis factor α, interleukin 1β, nitric oxide, superoxide dismutase levels, and catalase, glutathione peroxidase activities, malondialdehyde levels, and caspase-3 activity were measured in tissues taken from the spinal cord of rats in all groups killed 24 hours after ischemia reperfusion injury. The Basso, Beattie, and Bresnahan locomotor scale and inclined plane test were used for neurologic assessment before and after SCIRI. In addition, histologic and ultrastructural analyses of tissue samples in all groups were performed.

RESULTS

SCIRI also caused marked increase in tissue tumor necrosis factor α, interleukin 1β, nitric oxide, malondialdehyde levels, and caspase-3 activity, because of inflammation, increased free radical generation, lipid peroxidation, and apoptosis, respectively. On the other hand, SCIRI caused significant reduction in tissue superoxide dismutase, glutathione peroxidase, and catalase activities. Pretreatment with GLPS likewise diminished the level of the spinal cord edema, inflammation, and tissue injury shown by pathologic and ultrastructural examination. Pretreatment with GLPS reversed all these biochemical changes and improved the altered neurologic status.

CONCLUSIONS

These outcomes propose that pretreatment with GLPS prevents progression of SCIRI by alleviating inflammation, oxidation, and apoptosis.

New insights into spinal cord ischaemia after thoracic aortic procedures: the importance of the number of anterior radiculomedullary arteries for surgical outcome

OBJECTIVES

Anterior radiculomedullary arteries (ARMAs) link dorsal segmental arteries and the intraspinal compartment of the spinal collateral network. The number of thoracic ARMA is highly variable from one person to another. The impact of the number of ARMAs on spinal cord perfusion during thoracic aortic procedures is unknown. We investigated the influence of the number of thoracic ARMAs on spinal cord perfusion in an aortic surgical large animal model.

METHODS

Twenty-six pigs were included (20 treatment animals, 6 sham animals, weight 34 ± 3 kg). The animals underwent ligation of the left subclavian artery and the thoracic segmental arteries via a left lateral thoracotomy with normothermia. After sacrifice, complete body perfusion with coloured cast resin was performed and the number of thoracic ARMAs was documented at autopsy. End points were spinal cord perfusion pressure, cerebrospinal fluid pressure, spinal cord blood flow (microspheres) and neurological outcome. Observation time was 3 h post-ligation.

RESULTS

The numbers of thoracic ARMAs ranged between 3 (n = 1) and 13 (n = 1). The mean number was 8. Animals were grouped according to number of thoracic ARMA: 6-7 (5 animals), 8-10 (8 animals) and 11-13 (5 animals). A large number of thoracic ARMAs was linked to (i) a lower drop in spinal cord blood flow from baseline to post-clamp, (ii) the presence and increased magnitude of hyperaemia evident 3 h post-clamp (P < 0.001) and (iii) the presence of early hyperaemia starting immediately post-clamp in animals with 11 or more ARMA (P < 0.001).

CONCLUSIONS

We showed that a large number of thoracic ARMA protects against spinal cord injury during descending aortic surgical procedures.1.

Protecting the brain and spinal cord in aortic arch surgery

Protection of the central nervous system-either the brain or the spinal cord-during aortic surgery has been the subject of intense research over the past several decades. While it took some 30 years to prove that some of the techniques first practiced in animals are valuable, surgeons can now take courage from 50 years of research that has resulted in superb outcomes, particularly when compared with historical results. Complex total arch operations and descending aortic operations can now be performed with less than a 2% rate of stroke, spinal cord injury, or death. Thoracoabdominal aortic operations and endovascular procedures have also become considerably safer with excellent results reported. The following review will discuss some of the historical outcomes, innovations, iterations, current techniques, and outcomes.

Cerebrospinal fluid drainage and thoracic endovascular aneurysm repair

Spinal cord complications including paraplegia and partial neurologic deficits remain a frequent problem during repair of descending thoracic or thoracoabdominal aortic aneurysms. Effective prevention of this dreaded complication is of paramount importance. Among the many adjuncts that have been proposed to prevent spinal cord complications, spinal fluid drainage is one that has been used by numerous teams. The aim of this review is to answer the following question: does spinal fluid drainage afford spinal cord protection during both open and endovascular repair of thoracic or thoracoabdominal aortic aneurysms?

Spinal Ischemia in Thoracic Aortic Procedures: Impact of Radiculomedullary Artery Distribution

BACKGROUND

The aim of this study was to assess the influence of thoracic anterior radiculomedullary artery (tARMA) distribution on spinal cord perfusion in a thoracic aortic surgical model.

METHODS

Twenty-six pigs (34 ± 3 kg; study group, n = 20; sham group, n = 6) underwent ligation of the left subclavian artery and thoracic segmental arteries. End points were spinal cord perfusion pressure (SCPP), regional spinal cord blood flow (SCBF), and neurologic outcome with an observation time of 3 hours. tARMA distribution patterns tested for an effect on end points included (1) maximum distance between any 2 tARMAs within the treated aortic segment (0 or 1 segment = small-distance group; >1 segment = large-distance group) and (2) distance between the end of the treated aortic segment and the first distal tARMA (at the level of the distal simulated stent-graft end = group 0; gap of 1 or more segments = group ≥1).

RESULTS

The number of tARMA ranged from 3 to 13 (mean, 8). In the large-distance group, SCBF dropped from 0.48 ± 0.16 mL/g/min to 0.3 ± 0.08 mL/g/min (p < 0.001). We observed no detectable SCBF drop in the small-distance group: 0.2 ± 0.05 mL/g/min at baseline to 0.23 ± 0.05 mL/g/min immediately after clamping (p = 0.147). SCBF increased from 0.201 ± 0.055 mL/g/min at baseline to 0.443 ± 0.051 mL/g/min at 3 hours postoperatively (p < 0.001) only in the small-distance group.

CONCLUSIONS

We demonstrate experimental data showing that distribution patterns of tARMAs correlate with the degree of SCBF drop and insufficient reactive parenchymal hyperemia in aortic procedures. Individual ARMA distribution patterns along the treated aortic segment could help us predict the individual risk of spinal ischemia.

Anti-paralytic medicinal plants - Review

Paralysis is the loss of the ability of one or more muscles to move, due to disruption of signaling between the nervous system and muscles. The most common causes of paralysis are stroke, head injury, spinal cord injury (SCI) and multiple sclerosis. The search for cure of paralysis is yet to be found. Many ethnobotanical surveys have reported the use of medicinal plants by various ethnic communities in treating and curing paralysis. The present review discusses the use of medicinal plants in India for ameliorating and curing paralytic conditions, as well as discuses some of the important developments in future possible applications of medicinal plants in treatment of paralysis. This review reports the use of 37 medicinal plants for their application and cure of ailments related to paralysis. Out of the 37 plants documented, 11 plants have been reported for their ability to cure paralysis. However, the information on the documented plants were mostly found to be inadequate, requiring proper authentication with respect to their specificity, dosage, contradictions etc. It is found that despite the claims presented in many ethnobotanical surveys, the laboratory analysis of these plants remain untouched. It is believed that with deeper intervention on analysis of bioactive compounds present in these plants used by ethic traditional healers for paralysis, many potential therapeutic compounds can be isolated for this particular ailment in the near future.

Current and emerging treatment options for spinal cord ischemia

Spinal cord infarction (SCI) is a rare but disabling disorder caused by a wide spectrum of conditions. Given the lack of randomized-controlled trials, contemporary treatment concepts are adapted from guidelines for cerebral ischemia, atherosclerotic vascular disease, and acute traumatic spinal cord injury. In addition, patients with SCI are at risk for several potentially life-threatening but preventable systemic and neurologic complications. Notably, there is emerging evidence from preclinical studies for the use of neuroprotection in acute ischemic injury of the spinal cord. In this review, we discuss the current state of the art for the therapy and prevention of SCI and highlight potential emerging treatment concepts awaiting translational adoption.

Bosentan reduces neuronal apoptosis following spinal cord ischemic reperfusion injury

STUDY DESIGN

Experimental study.

OBJECTIVES

To investigate the effects of endothelin-receptor antagonist Bosentan on the spinal neural apoptosis in rats with ischemic reperfusion (IR) injury.

SETTING

Department of Neurosurgery, the Second Affiliated Hospital, Xi'an Jiaotong University School of Medcine, Xi'an, Shaanxi Province, China:

METHODS

Sprague-Dawley Rats were randomly divided into two groups, saline (IRS, n=48) and Bosentan (IRB, n=48) treatment, respectively, when reperfused in 6 h, 12 h, 24 h, 3 days, 5 days and 7 days. Immunohistochemical staining was used to assess endothelin-1 (ET-1), endothelin receptor type A (ETRA), endothelin receptor type B (ETRB), Bcl-2, Bax, Caspase-8, Caspase-9 and Caspase-3 expression. ET-1 and its receptor in spinal cord tissue were evaluated by real-time PCR. Plasma ET-1 concentration was also detected using radioimmunoassay.

RESULTS

Compared with the group IRS, plasma concentration of ET-1 in group IRB was significantly increased at each time point (P<0.05) and peaked at 24 h (P<0.01). ETRB expression in group IRB was significantly higher than group IRS at each time point (P<0.05) and peaked at day 3 (P<0.01). The difference in the expression of ETRA was not statistically significant in the group IRS and IRB (P>0.05). The apoptosis rate in group IRB was significantly decreased at each time point (P<0.05). The protein expressions of Bcl-2, Bax, Caspase-8, Caspase-9 and Caspase-3 were significantly increased in response to Bosentan treatment after IR.

CONCLUSION

These results suggest Bosentan decreases apoptosis rate after IR injury in the spinal cord, possibly through the ET-1-ETRB signaling pathway.

The role of allopurinol's timing in the ischemia reperfusion injury of small intestine

INTRODUCTION

Allopurinol acts protectively in the ischemia reperfusion injury of the small intestine. The aim of this experimental study is to define the ideal time of administration of allopurinol, in experimental models of ischemia/reperfusion.

MATERIALS AND METHODS

We used 46 rabbits that were divided into four groups. Group A was the control. In Group B allopurinol was administered 10 min before ischemia and in Group C 2 min before reperfusion. In Group D, allopurinol was administered before ischemia and before reperfusion in half doses. Blood samples were collected at three different moments: (t1) prior to ischemia, (t2) prior to reperfusion, and (t3) after the end of the reperfusion, in order to determine superoxide dismutase (SOD) and neopterin values. Specimens of the intestine were obtained for histological analysis and determination of malondialdehyde (MDA).

RESULTS

In Group A, mucosal lesions were more extensive compared to those of the other three groups. Similarly, MDA, SOD and neopterin values were significantly higher. On the contrary, Group D showed the mildest mucosal lesions, as well as the lowest MDA, SOD and neopterin values. Finally, the lesions and the above mentioned values were bigger in Group C than in Group D.

CONCLUSIONS

The administration of allopurinol attenuates the production and damage effect of free oxygen radicals during ischemia reperfusion of the small intestine, thus protecting the intestinal mucosa. Its maximum beneficial action is achieved when administered both before ischemia and before reperfusion of the small intestine.

Neuroprotective effects of gabapentin on spinal cord ischemia-reperfusion injury in rabbits

Object

Extensive research has been focused on neuroprotection after spinal cord trauma to alleviate the effects of secondary injury. This study aims to investigate the neuroprotective effects of gabapentin in an experimental spinal cord ischemia reperfusion injury.

Methods

Thirty-two adult male New Zealand white rabbits received spinal cord ischemic injury using the aortic occlusion model. Animals were divided into 4 groups (sham, control, low-dose, and high-dose treatment groups; 8 rabbits in each group). High (200 mg/kg) and low (30 mg/kg) doses of gabapentin were administered to the animals in the treatment groups after spinal cord ischemic injury. Neurological status of the animals, ultrastructural findings in injured tissue samples, and levels of tissue injury markers in these 2 groups were compared with findings in the animals that did not receive the ischemic procedure (sham-operated group) and those that received normal saline after administration of ischemia.

Results

Regarding levels of tissue injury marker levels after ischemic injury, animals in the gabapentin-treated groups demonstrated better results than animals in the other groups. The ultrastructural findings and caspase-3 activity were similar. The treatment groups demonstrated better results than the other groups.

Conclusions

Gabapentin demonstrated significant neuroprotection after early phases of ischemic injury. Further studies with different experimental settings including neurological outcome are required to achieve conclusive results.

Delayed paraplegia after spinal cord ischemic injury requires caspase-3 activation in mice

BACKGROUND AND PURPOSE

Delayed paraplegia remains a devastating complication after ischemic spinal cord injury associated with aortic surgery and trauma. Although apoptosis has been implicated in the pathogenesis of delayed neurodegeneration, mechanisms responsible for the delayed paraplegia remain incompletely understood. The aim of this study was to elucidate the role of apoptosis in delayed motor neuron degeneration after spinal cord ischemia.

METHODS

Mice were subjected to spinal cord ischemia induced by occlusion of the aortic arch and left subclavian artery for 5 or 9 minutes. Motor function in the hind limb was evaluated up to 72 hours after spinal cord ischemia. Histological studies were performed to detect caspase-3 activation, glial activation, and motor neuron survival in the serial spinal cord sections. To investigate the impact of caspase-3 activation on spinal cord ischemia, outcome of the spinal cord ischemia was examined in mice deficient for caspase-3.

RESULTS

In wild-type mice, 9 minutes of spinal cord ischemia caused immediate paraplegia, whereas 5 minutes of ischemia caused delayed paraplegia. Delayed paraplegia after 5 minutes of spinal cord ischemia was associated with histological evidence of caspase-3 activation, reactive astrogliosis, microglial activation, and motor neuron loss starting at approximately 24 to 48 hours after spinal cord ischemia. Caspase-3 deficiency prevented delayed paraplegia and motor neuron loss after 5 minutes of spinal cord ischemia, but not immediate paraplegia after 9 minutes of ischemia.

CONCLUSIONS

The present results suggest that caspase-3 activation is required for delayed paraplegia and motor neuron degeneration after spinal cord ischemia.

Hydroxysafflor Yellow A protects spinal cords from ischemia/reperfusion injury in rabbits

Background

Hydroxysafflor Yellow A (HSYA), which is one of the most important active ingredients of the Chinese herb Carthamus tinctorius L, is widely used in the treatment of cerebrovascular and cardiovascular diseases. However, the potential protective effect of HSYA in spinal cord ischemia/reperfusion (I/R) injury is still unknown.

Methods

Thirty-nine rabbits were randomly divided into three groups: sham group, I/R group and HSYA group. All animals were sacrificed after neurological evaluation with modified Tarlov criteria at the 48th hour after reperfusion, and the spinal cord segments (L4-6) were harvested for histopathological examination, biochemical analysis and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining.

Results

Neurological outcomes in HSYA group were slightly improved compared with those in I/R group. Histopathological analysis revealed that HSYA treatment attenuated I/R induced necrosis in spinal cords. Similarly, alleviated oxidative stress was indicated by decreased malondialdehyde (MDA) level and increased superoxide dismutase (SOD) activity after HSYA treatment. Moreover, as seen from TUNEL results, HSYA also protected neurons from I/R-induced apoptosis in rabbits.

Conclusions

These findings suggest that HSYA may protect spinal cords from I/R injury by alleviating oxidative stress and reducing neuronal apoptosis in rabbits.

Suppressive effects of intrathecal granulocyte colony-stimulating factor on excessive release of excitatory amino acids in the spinal cerebrospinal fluid of rats with cord ischemia: role of glutamate transporters

Recently, the hematopoietic factor, granulocyte colony-stimulating factor (G-CSF), has been shown to exhibit neuroprotective effects in CNS injuries. Our previous study demonstrated that intrathecal (i.t.) G-CSF significantly improved neurological defects in spinal cord ischemic rats. Considerable evidence indicates that the release of excessive amounts of excitatory amino acids (EAAs) plays a critical role in neuron injury induced by ischemic insult. In the present study, we used a spinal cord ischemia-microdialysis model to examine whether i.t. G-CSF exerted antiexcitotoxicity effects in a rat model of spinal cord ischemia. I.t. catheters and a microdialysis probe were implanted in male Wistar rats. The results revealed that spinal cord ischemia-induced neurological defects were accompanied by a significant increase in the concentration of EAAs (aspartate and glutamate) in the spinal dialysates from 30 min to 2 days after reperfusion. I.t administration of G-CSF immediately after the performance of surgery designed to induce ischemia led to a significant reduction in ischemia-induced increases in the levels of spinal EAAs. Moreover, i.t. G-CSF also brought about a significant reduction in the elevation of spinal EAA concentrations induced by exogenous i.t. administration of glutamate (10 microl of 500 mM). I.t. G-CSF attenuated spinal cord ischemia-induced downregulation of expression of three glutamate transporters (GTs), glial transporter Glu-Asp transporter (GLAST), Glu transporter-1 (GLT-1), and excitatory amino acid carrier 1 (EAAC1) protein 48 h after spinal cord ischemic surgery. Immunohistofluorescent staining showed that i.t. G-CSF significantly upregulated expression of the three GTs in the gray matter of the lumbar spinal cord from 3 to 24 h after injection. We propose that i.t. G-CSF possesses an ability to reduce the extent of spinal cord ischemia-induced excitotoxicity by inducing the expression of glutamate transporters.

Beneficial effect of the oxygen free radical scavenger amifostine (WR-2721) on spinal cord ischemia/reperfusion injury in rabbits

Background

Paraplegia is the most devastating complication of thoracic or thoraco-abdominal aortic surgery. During these operations, an ischemia-reperfusion process is inevitable and the produced radical oxygen species cause severe oxidative stress for the spinal cord. In this study we examined the influence of Amifostine, a triphosphate free oxygen scavenger, on oxidative stress of spinal cord ischemia-reperfusion in rabbits.

Methods

Eighteen male, New Zealand white rabbits were anesthetized and spinal cord ischemia was induced by temporary occlusion of the descending thoracic aorta by a coronary artery balloon catheter, advanced through the femoral artery. The animals were randomly divided in 3 groups. Group I functioned as control. In group II the descending aorta was occluded for 30 minutes and then reperfused for 75 min. In group III, 500 mg Amifostine was infused into the distal aorta during the second half-time of ischemia period. At the end of reperfusion all animals were sacrificed and spinal cord specimens were examined for superoxide radicals by an ultra sensitive fluorescent assay.

Results

Superoxide radical levels ranged, in group I between 1.52 and 1.76 (1.64 ± 0.10), in group II between 1.96 and 2.50 (2.10 ± 0.23), and in group III (amifostine) between 1.21 and 1.60 (1.40 ± 0.19) (p = 0.00), showing a decrease of 43% in the Group of Amifostine. A lipid peroxidation marker measurement ranged, in group I between 0.278 and 0.305 (0.296 ± 0.013), in group II between 0.427 and 0.497 (0.463 ± 0.025), and in group III (amifostine) between 0.343 and 0.357 (0.350 ± 0.007) (p < 0.00), showing a decrease of 38% after Amifostine administration.

Conclusion

By direct and indirect methods of measuring the oxidative stress of spinal cord after ischemia/reperfusion, it is suggested that intra-aortic Amifostine infusion during spinal cord ischemia phase, significantly attenuated the spinal cord oxidative injury in rabbits.

Regional distribution of blood flow during proximal aortic cross‐clamping: An experimental study using coloured microspheres

OBJECTIVE

To investigate the effect of thoracic aortic cross-clamping on blood perfusion of the brain, spinal cord, heart, muscular tissue and visceral organs.

MATERIAL AND METHODS

Nine pigs underwent 30 min cross-clamping of the descending thoracic aorta. Multiple coloured microspheres (15.0 microm +/- 0.1) were infused into the left ventricle before and during aortic cross-clamping (XC) and after declamping (DC). Tissue samples were analysed by spectrophotometry.

RESULTS

Blood perfusion of the middle and lower segments of the spinal cord was significantly reduced during aortic XC. Perfusion of the brain was not significantly altered by aortic XC, while perfusion of myocardium increased 3-fold. During XC, perfusion of the deltoid muscle and diaphragm increased 5-fold and 13-fold, respectively, while a decrease was found in the gluteus muscle. Renal blood flow was significantly reduced during XC. Finally, XC induced a significant decrease of perfusion in the bowel, spleen, liver and pancreas.

CONCLUSION

During XC of the thoracic aorta, the perfusion of the muscular tissue was significantly increased proximal to the level of XC. The circulation of the brain was unchanged, probably because of autoregulatory mechanisms. Blood perfusion of the myocardium increased 3-fold during XC.

Effect of Central Venous Pressure on Spinal Cord Oxygenation

To analyze the effect of central venous pressure on cerebrospinal fluid oxygen tension and intrathecal pressure, multiparameter sensors were introduced into the intrathecal space for continuous monitoring of cerebrospinal fluid PO2, PCO2, and intrathecal pressure in 15 pigs. After 20 min of aortic clamping, hypervolemia was established for 20 min, followed by normovolemia. The animals were divided into 3 groups: in group 1, cerebrospinal fluid PO2 = 0% at some time during crossclamping; in group 2, cerebrospinal fluid PO2 was <50%; and in group 3, cerebrospinal fluid PO2 remained ≥50%. Mean decreases in cerebrospinal fluid PO2 during the initial 20 min of crossclamping were 82%, 57%, and 15% in groups 1, 2, and 3, respectively. Following induction of hypervolemia, central venous and cerebrospinal fluid pressures increased simultaneously; this caused a significant decrease in cerebrospinal fluid PO2 in group 2 only. In this model, aortic clamping did not increase cerebrospinal fluid pressure if central venous pressure was not elevated. The detrimental effect of elevated intrathecal pressure on cerebrospinal fluid oxygenation was seen only in animals with an intermediate degree of spinal cord ischemia. This might have important implications for the prevention of paraplegia during thoracoabdominal aortic replacement.

Spinal cord ischemia after endovascular repair of the descending thoracic aorta in a sheep model

OBJECTIVES

Spinal cord ischemia remains a devastating complication after thoracic aortic surgery. The aim of this study was to investigate the pathophysiology of spinal cord ischemia after thoracic aortic endografting and the role of intercostal artery blood supply for the spinal cord in a standardized animal model.

METHODS

Female merino sheep were randomized to either I, open thoracotomy with cross-clamping of the descending aorta for 50 min (n=7), II, endograft implantation (TAG, WL Gore & Ass.), (n=6) or III open thoracotomy with clipping of all intercostal arteries (n=5) . CT-angiography was used to assess completion of surgical protocol and assess the fate of intercostal arteries. Tarloy score was used for daily neurological examination for up to 7 days post-operatively. Histological cross sections of the lumbar, thoracic and cervical spinal cords were scored for ischemic damage after stained with Hematoxylin-Eosin, Klüver-Barrrera and antibodies. Exact Kruskall-Wallis-Test was used for statistical assessment (p<0.05).

RESULTS

Incidence of paraplegia was 100% in group I and 0% in group II (p=0.0004). When compared to the endovascular group, there was a higher rate of histological changes associated with spinal cord ischemia in the animals of the control group (p=0.0096). Group III animals showed no permanent neurological deficit and only 20% infarction rate (p=0.0318 compared to group I).

CONCLUSIONS

In sheep, incidence of histological and clinical ischemic injury of the spinal cord following endografting was very low. Complete thoracic aortic stent-grafting was feasible without permanent neurologic deficit. Following endovascular coverage or clipping of their origins, there is retrograde filling of the intercostal arteries which remain patent.

Functional recovery in rats with ischemic paraplegia after spinal grafting of human spinal stem cells

Transient spinal cord ischemia in humans can lead to the development of permanent paraplegia with prominent spasticity and rigidity. Histopathological analyses of spinal cords in animals with ischemic spastic paraplegia show a selective loss of small inhibitory interneurons in previously ischemic segments but with a continuing presence of ventral alpha-motoneurons and descending cortico-spinal and rubro-spinal projections. The aim of the present study was to examine the effect of human spinal stem cells (hSSCs) implanted spinally in rats with fully developed ischemic paraplegia on the recovery of motor function and corresponding changes in motor evoked potentials. In addition the optimal time frame for cell grafting after ischemia and the optimal dosing of grafted cells were also studied. Spinal cord ischemia was induced for 10 min using aortic occlusion and systemic hypotension. In the functional recovery study, hSSCs (10,000-30,000 cells/0.5 mul/injection) were grafted into spinal central gray matter of L2-L5 segments at 21 days after ischemia. Animals were immunosuppressed with Prograf (1 mg/kg or 3 mg/kg) for the duration of the study. After cell grafting the recovery of motor function was assessed periodically using the Basso, Beattie and Bresnahan (BBB) scoring system and correlated with the recovery of motor evoked potentials. At predetermined times after grafting (2-12 weeks), animals were perfusion-fixed and the survival, and maturation of implanted cells were analyzed using antibodies recognizing human-specific antigens: nuclear protein (hNUMA), neural cell adhesion molecule (hMOC), neuron-specific enolase (hNSE) and synapthophysin (hSYN) as well as the non-human specific antibodies TUJ1, GFAP, GABA, GAD65 and GLYT2. After cell grafting a time-dependent improvement in motor function and suppression of spasticity and rigidity was seen and this improvement correlated with the recovery of motor evoked potentials. Immunohistochemical analysis of grafted lumbar segments at 8 and 12 weeks after grafting revealed intense hNSE immunoreactivity, an extensive axo-dendritic outgrowth as well as rostrocaudal and dorsoventral migration of implanted hNUMA-positive cells. An intense hSYN immunoreactivity was identified within the grafts and in the vicinity of persisting alpha-motoneurons. On average, 64% of hSYN terminals were GAD65 immunoreactive which corresponded to GABA immunoreactivity identified in 40-45% of hNUMA-positive grafted cells. The most robust survival of grafted cells was seen when cells were grafted 21 days after ischemia. As defined by cell survival and laminar distribution, the optimal dose of injected cells was 10,000-30,000 cells per injection. These data indicate that spinal grafting of hSSCs can represent an effective therapy for patients with spinal ischemic paraplegia.

Is subdiaphragmatic aortic cross-clamping a suitable model for spinal cord ischemia/reperfusion injury study in rats?

PURPOSE

To evaluate the efficacy of subdiaphragmatic aortic cross-clamping in an experimental model of ischemia/reperfusion injury of the spinal cord in albino rats.

METHODS

Thirty-six male Wistar rats were randomized in two groups (n=18): G-1 (Sham) and G-2 (Ischemia/Reperfusion, I/R). G-2 rats were submitted to 30 min subdiafragmatic aortic cross-clamping. G-1 rats served as controls and were submitted to surgical trauma (laparotomy) without ischemia. Samples (spinal cord and arterial blood) were collected at the end of ischemic period and 10 (T-10) and 20 (T-20) min later in G-2 rats. Sham rats (G-1) samples were collected at the same time-points. Blood and tissue metabolites concentrations of pyruvate, lactate, glucose and medullary adenosine triphosphate (ATP) were assayed.

RESULTS

Blood and tissue concentrations of pyruvate and glucose as well as lactate and medullary ATP were not different when comparing G1 to G2. Lactacemia was significantly elevated in G-2 compared with G-1 rats during reperfusion (T-10).

CONCLUSION

Subdiaphragmatic aortic cord cross-clamping is not a suitable rat model for spinal cord ischemia/reperfusion injury study as it does not ensure changes in in vivo tissue metabolites concentrations similar to those found in tissues subjected to ischemia/reperfusion.

Effects of a cantaloupe melon extract/wheat gliadin biopolymer during aortic cross-clamping

OBJECTIVE

We previously reported in healthy volunteers that a cantaloupe melon extract chemically combined with wheat gliadin (melon extract/gliadin) and containing SOD, catalase and residual glutathione peroxidase (GPx), protected against DNA strand-break damage induced by hyperbaric oxygen (HBO), a well-established model of DNA damage resulting from oxidative stress. Aortic cross-clamping is a typical example of ischemia/reperfusion injury-related oxidative stress, and therefore we investigated whether this melon extract/gliadin would also reduce DNA damage after aortic cross-clamping and reperfusion.

DESIGN

Prospective, randomized, controlled experimental study.

SETTING

Animal laboratory.

PATIENTS AND PARTICIPANTS

18 anesthetized, mechanically ventilated and instrumented pigs.

INTERVENTIONS

After 14 days of oral administration of 1250 mg of the melon extract/gliadin (n=9) or vehicle (n=9), animals underwent 30 min of thoracic aortic cross-clamping and 4 h of reperfusion.

MEASUREMENTS AND RESULTS

Before clamping, immediately before declamping, and at 2 and 4 h of reperfusion, we measured blood isoprostane (immunoassay) and malondialdehyde concentrations (fluorimetric thiobarbituric acid test), SOD, catalase and GPx activities (spectrophotometric kits), NO formation (nitrate+nitrite; chemoluminescence), DNA damage in whole blood samples and isolated lymphocytes exposed to hyperbaric oxygen (comet assay). Organ function was also evaluated. Kidney and spinal cord specimen were analysed for apoptosis (TUNEL assay). The melon extract/gliadin blunted the DNA damage, reduced spinal cord apoptosis and attenuated NO release, however, without any effect on lipid peroxidation and organ function.

CONCLUSIONS

Pre-treatment with the oral melon extract/gliadin may be a therapeutic option to reduce oxidative cell injury affiliated with aortic cross-clamping.

Anti-apoptotic and neuroprotective effects of Tetramethylpyrazine following spinal cord ischemia in rabbits

Background

Tetramethylpyrazine (TMP) is one of the most important active ingredients of a Chinese herb Ligusticum wallichii Franchat, which is widely used in many ischemia disorders treatments. However, the exact mechanism by which TMP protects the spinal cord ischemia/reperfusion (I/R) injury is still unknown. For this purpose, rabbits were randomly divided into sham group, control group and TMP group. After the evaluation of neurologic function, the spinal cords were immediately removed for biochemical and histopathological analysis. Apoptosis was measured quantitatively by the terminal transferase UTP nick end-labeling (TUNEL) method and confirmed by electron microscopic examination, the expression of Bax and Bcl-2 was immunohistochemically evaluated and quantified by Western blot analysis.

Results

Neurologic outcomes in the TMP-group were significantly better than those in the control group (P < 0.05). TMP decreased spinal cord malondialdehyde (MDA) levels and ameliorated the down regulation of spinal cord superoxide dismutase (SOD) activity. TMP significantly reduced the loss of motoneurons and TUNEL-positive rate. Greater Bcl-2 and attenuated Bax expression was found in the TMP treating rabbits.

Conclusion

These findings suggest that TMP has protective effects against spinal cord I/R injury by reducing apoptosis through regulating Bcl-2 and Bax expression.

Paralysis after aortic surgery: In search of lost cord function

During the early 1980s, the rate of paralysis after aortic surgery was as high as 41% in patients for the most complex thoracoabdominal aortic operations. After comparing human and chacma baboon (papio ursinus) spinal cord vascular anatomy, an animal model was established to study the pathophysiology of aortic cross-clamping and the aetiology of the paralysis. Techniques, including motor evoked responses for monitoring spinal cord function, were developed that were tried in humans and later culminated in prospective and randomized studies. These established that the following were protective: combining cerebrospinal fluid with intrathecal papaverine; cooling systemically to moderate or profound hypothermia; minimizing intercostal ischaemia time; using a sequential segmental repair approach; re-attaching all patent and segmental intercostal arteries below T8 for descending thoracic aortic repair and from T6 to L2 for thoracoabdominal repairs; continuing cerebrospinal fluid drainage for at least two days and maintaining patients hypertensive after surgery. The net result has been that, in two of our recent series, the risk of permanent paralysis has been reduced to between 3.1% and 3.8%.

Cerebrospinal fluid may mediate CNS ischemic injury

Background

The central nervous system (CNS) is extremely vulnerable to ischemic injury. The details underlying this susceptibility are not completely understood. Since the CNS is surrounded by cerebrospinal fluid (CSF) that contains a low concentration of plasma protein, we examined the effect of changing the CSF in the evolution of CNS injury during ischemic insult.

Methods

Lumbar spinal cord ischemia was induced in rabbits by cross-clamping the descending abdominal aorta for 1 h, 2 h or 3 h followed by 7 d of reperfusion. Prior to ischemia, rabbits were subjected to the following procedures; 1) CSF depletion, 2) CSF replenishment at 0 mmHg intracranial pressure (ICP), and 3) replacement of CSF with 8% albumin- or 1% gelatin-modified artificial CSF, respectively. Motor function of the hind limbs and histopathological changes of the spinal cord were scored. Post-ischemic microcirculation of the spinal cord was visualized by fluorescein isothiocyanate (FITC) albumin.

Results

The severity of histopathological damage paralleled the neurological deficit scores. Paraplegia and associated histopathological changes were accompanied by a clear post-ischemic deficit in blood perfusion.

Spinal cord ischemia for 1 h resulted in permanent paraplegia in the control group. Depletion of the CSF significantly prevented paraplegia. CSF replenishment with the ICP reduced to 0 mmHg, did not prevent paraplegia. Replacement of CSF with albumin- or gelatin-modified artificial CSF prevented paraplegia in rabbits even when the ICP was maintained at 10–15 mmHg.

Conclusion

We conclude that the presence of normal CSF may contribute to the vulnerability of the spinal cord to ischemic injury. Depletion of the CSF or replacement of the CSF with an albumin- or gelatin-modified artificial CSF can be neuroprotective.

Region-specific cell grafting into cervical and lumbar spinal cord in rat: a qualitative and quantitative stereological study

In the present study, we have characterized an atraumatic grafting technique which permits multiple, segmental, and lamina-specific injections into cervical or lumbar spinal cord. Cell injections were performed in spinally mounted rats of different ages and spinal cord size, using a micromanipulator and glass microcapillary connected to a digital microinjector. For grafting, we used human neuroteratoma (hNT) cells, BrdU-labeled rat spinal precursors or primary embryonic spinal cord neurons isolated from E14 spinal cord of the eGFP+ rat. Systematic quantification of grafted cells was performed using stereological principles of systematic random sampling and semi-automated optical Disector software. Volume reconstruction was performed using serial sections from grafted areas and custom-developed software (Ellipse) which permits "two reference points" semi-automated alignment of images, as well as volume reconstruction and calculation. By coupling these techniques, it is possible to achieve a relatively precise and atraumatic cell delivery into multiple spinal cord segments and specific spinal laminae. Consistency of the multiple grafts position in the targeted laminar areas was verified by a systematic volume reconstruction. Good survival of implanted cells for the three different cell lines used indicate that this grafting technique coupled with a systematic analysis of the individual grafting sites can represent a valuable implantation-analytical system.

Erdosteine ameliorates neurological outcome and oxidative stress due to ischemia/reperfusion injury in rabbit spinal cord

OBJECTIVE

Oxygen-derived free radicals have been suggested as important in degeneration after spinal cord ischemia. The aim of this study was to investigate whether erdosteine has a protective effect against spinal cord ischemia during aortic cross clamping.

MATERIALS AND METHODS

New Zealand White rabbits (n=21) were divided into three groups. In the ischemia/reperfusion group (I/R) (n=8), the infrarenal aorta of rabbits was cross clamped for 21 min and then reperfused. In erdosteine group, the administration of erdosteine solution (50 mg/kg) was started two days before aortic cross-clamping and rabbits (n=8) were subjected to ischemia and reperfusion. Animals in control group (n=5) underwent a surgical procedure similar to the other groups but the aorta was not clamped. The animals were sacrificed at 72 h and histopathological, and biochemical analyses were carried out on the lumbar spinal cords.

RESULTS

Erdosteine treatment was associated with improved neurological function in the postoperative period. Histopathological examination of spinal cord tissues in erdosteine group revealed changes consistent with mild ischemic injury, but rabbits in I/R group with paraplegia had total destruction of the motor neurons. Biochemical analyses of spinal cord tissues, in the I/R group, revealed a significant increase in the superoxide dismutase, xanthine oxidase, adenosine deaminase and myeloperoxidase activities, and a significant depletion in glutathione peroxidase activity when compared to that of control rabbits. Erdosteine treatment prevented the increase of all these enzymes except adenosine deaminase. Ischemia/reperfusion produced a significant increase in the tissue malondialdehyde levels. Ischemia/reperfusion-induced increments in malondialdehyde content of the spinal cord were significantly prevented by erdosteine treatment.

CONCLUSIONS

The present study demonstrated that erdosteine treatment before aortic cross clamping ameliorates neurological outcome, neuronal injury and oxidative stress in the rabbit spinal cord.

The protective effect of nebivolol on ischemia/reperfusion injury in rabbit spinal cord

The aim of this experimental study was to investigate whether nebivolol has protective effects against neuronal damage induced by spinal cord ischemia/reperfusion (I/R). Twenty-one rabbits were divided into three groups: group I (control, no I/R), group II (only I/R) and group III (I/R+nebivolol). Spinal cord ischemia was induced by clamping the aorta both below the left renal artery and above the aortic bifurcation. Seventy-two hours postoperatively, the motor function of the lower limbs was evaluated in each animal. The animals were sacrificed at 72 h, and histopathological and biochemical analyses were carried out in the lumbar spinal cords. The motor deficit scores in nebivolol group were different from I/R group at 72 h (3.25+/-0.70 vs. 1.75+/-1.28, p=0.01). I/R produced a significant increase in the superoxide dismutase (SOD), xanthine oxidase (XO), adenosine deaminase (ADA) and myeloperoxidase (MPO) activities in spinal cord tissue when compared with control group. Nebivolol treatment prevented the increase of all those enzymes activities produced by I/R. A significant decrease in spinal cord glutathione peroxidase (GSH-Px) level was seen in I/R group and nebivolol treatment prevented the decrement in the spinal cord tissue GSH-Px contents. On the other hand, I/R produced a significant increase in the spinal cord tissue malondialdehyde (MDA) and nitric oxide (NO) contents, this was prevented by nebivolol treatment. In conclusion, this study demonstrates a considerable neuroprotective effect of nebivolol on neurological, biochemical and histopathological status during periods of spinal cord I/R in rabbits.

Characterization of spinal HSP72 induction and development of ischemic tolerance after spinal ischemia in rats

Induction of heat shock protein (HSP72) has been implicated in the development of ischemic tolerance in several tissue organs including brain and spinal cord. In the present study, using an aortic balloon occlusion model in rats, we characterized the effect of transient noninjurious (3 or 6 min) or injurious intervals (10 min) of spinal ischemia followed by 4-72 h of reflow on spinal expression of HSP72 and GFAP protein. In a separate group of animals, the effect of ischemic preconditioning (3 or 6 min) on the recovery of function after injurious interval of spinal ischemia (10 min) was studied. After 3 min of ischemia, there was a modest increase in HSP72 protein immunoreactivity in the dorsal horn neurons at 12 h after reperfusion. After 6 min of ischemia, a more robust and wide spread HSP72 protein expression in both dorsal and ventral horn neurons was detected. The peak of the expression was seen at 24 h after ischemia. At the same time point, a significant increase in spinal tissue GFAP expression was measured with Western blots and corresponded morphologically with the presence of activated astrocytes in spinal segments that had been treated similarly. After 10 min of ischemia and 24 h of reflow, a significant increase in spinal neuronal HSP72 expression in perinecrotic regions was seen. Behaviorally, 3 min preconditioning ischemia led to the development of a biphasic ischemic tolerance (the first at 30 min and the second at 24 h after preconditioning) and was expressed as a significantly better recovery of motor function after exposure to a second 10-min interval of spinal ischemia. After 6 min ischemic preconditioning, a more robust ischemic tolerance at 24 h after preconditioning then seen after 3-min preconditioning was detected. These data indicate that 3 min of spinal ischemia represents a threshold for spinal neuronal HSP72 induction, however, a longer sublethal interval (6 min) of preconditioning ischemia is required for a potent neuronal HSP72 induction. More robust neurological protection, seen after 6 min of preconditioning ischemia, also indicates that HSP72 expression in spinal interneurons seen at 24 h after preconditioning may represent an important variable in modulating ischemic tolerance observed during this time frame.