Elsevier

The Spine Journal

Volume 14, Issue 1, 1 January 2014, Pages 119-127
The Spine Journal

Basic Science
Effect of VEGF and CX43 on the promotion of neurological recovery by hyperbaric oxygen treatment in spinal cord–injured rats

https://doi.org/10.1016/j.spinee.2013.06.084Get rights and content

Abstract

Background context

Spinal cord injury (SCI) is a serious health issue that may result in high health care costs, with additional social and psychological burdens. Hyperbaric oxygen (HBO) treatment has been found to be beneficial for neurological recovery; however, the underlying mechanisms are yet to be characterized.

Purpose

The aim of this study was to investigate the mechanisms of HBO treatment in SCI by measuring the expression levels of vascular endothelial growth factor (VEGF) and Connexin43 (CX43) in the injured spinal cord tissue.

Study design/setting

An experiment animal study of rats undergoing SCI and HBO treatment.

Methods

The spinal cord injury model was established in rats, which were randomly divided into the following four groups: (1) the sham-operated group (SH), (2) the sham-operated and hyperbaric oxygen treatment group (SH+HBO), (3) the spinal cord injury group (SCI), and (4) the spinal cord injury and hyperbaric oxygen treatment group (SCI+HBO). For groups of SH+HBO and SCI+HBO, the animals received 1 hour of HBO at 2.0 ATA in 100% O2 twice per day for 3 days and then daily for the following days consecutively after surgery. After operation, neurological assessments were performed, the spinal cord tissue samples were harvested for histopathological evaluation, Western blot and real-time polymerase chain reaction analysis.

Results

The Basso-Bettie-Bresnahan scores were significantly improved in the SCI+HBO group compared with the SCI group on the postoperative 7th and 14th days. The histology scores were significantly decreased by HBO treatment compared with that in the SCI group on the postoperative 3rd, 7th, and 14th days. Western blot analysis and real-time polymerase chain reaction revealed that the expression level of vascular endothelial growth factor (VEGF) in the SCI+HBO group was significantly increased compared with the SCI group. The protein expression level of CX43 and its mRNA level in the SCI+HBO group were significantly decreased on the postoperative 3rd and 7th days, whereas its expression was significantly increased by HBO treatment on the postoperative 14th day compared with the SCI group.

Conclusions

HBO treatment improved neurological recovery when applied after SCI. The expression level changes of VEGF and CX43 may contribute to the further understanding on the molecular mechanisms of HBO treatment on SCI.

Introduction

Spinal cord injury (SCI) is a devastating condition for the individual patient and costly to society as a whole by requiring substantial long-term health-care expenditures. Trauma to the spinal cord causes both primary and secondary injury. Primary injury to the spinal cord immediately disrupts cell membranes, destroys myelin and axons, and damages microvessels, thereby triggering devastating secondary injuries [1]. Secondary injury refers to a complex array of pathophysiological processes, including ischemia, edema, local inflammation, production of free radicals, and hyperoxidation [2], [3]. The end result of SCI is that some of the neurons and glial cells die days or weeks after spinal cord injury as the result of the secondary injury, even though they survived from the initial injury [4], [5].

Numerous spinal cord protection methods, including distal aortic perfusion, reattachment of critical intercostal arteries, hypothermia, and administration of various pharmacologic agents, have been suggested to minimize the devastating complication of SCI. However, applications of these techniques had only decreased but not eliminated postoperative spinal cord dysfunction, thus further investigations are necessary to improve the treatment of SCI [6], [7]. Hyperbaric oxygen (HBO) therapy is a medical treatment that administers 100% oxygen at a controlled pressure (greater than sea level) for a prescribed period of time (60–90 minutes). Because of the capability of increasing tissue oxygenation, HBO treatment raises the tissues' tolerance to ischemia and corrects the metabolic disorders apparent in the ischemic tissue. Recent reports claimed that HBO treatment is beneficial for neurological recovery in acute and chronic SCI [8], [9], but the underlying mechanism needs to be further characterized.

In the central nervous system (CNS), vascular endothelial growth factor (VEGF) plays a pivotal role not only in vascularization, but also in neurotrophic, neuronal proliferation, and the growth of coordinated vascular and neuronal networks [10]. Gap junctions are intercellular channels that are integral for the functioning of the glial network. They allow the passage of ions, metabolites, and second messengers between neighboring cells [11]. The primary structural unit of a gap junction is a membrane protein termed connexin. Connexin43 (CX43) is the predominant protein for the formation of gap junctions in the CNS and is expressed primarily on astrocytes, activated microglia, developing neurons, the smooth muscle, and endothelial cells of blood vessels. CX43 is an important mediator of CNS injury [12]. In this study, we attempted to explore the possible mechanism of HBO treatment in SCI by measuring the expression levels of VEGF and CX43 in the injured spinal cord tissue.

Section snippets

Animal care

Healthy adult male Sprague-Dawley (SD) rats, weighing 250 to 300 g at the beginning of the study, were kept two per cage for at least 5 days after their arrival at our laboratory. The rats had access to food and water ad libitum and were housed within a room with a 12:12-hour light/dark cycle. This study was performed in accordance with the ethical guidelines laid down by the Committee for the Purpose of Control and Supervision of Experiments on Animals, Capital Medical University (Beijing,

Evaluation of motor function

To evaluate the extent of motor function recovery, we used the BBB locomotor scores. The BBB scores were significantly lower in SCI and SCI+HBO groups compared with SH and SH+HBO groups (p<.01). Meanwhile, a significant gradual recovery was observed in the rats of SCI and SCI+HBO groups over time, on the 7th and 14th days postoperatively, HBO treatment caused a significant change in BBB score as compared with the SCI group values (p<.05). There was no significant difference in BBB score between

Discussion

It has been recognized that HBO treatment is beneficial in acute and chronic SCI. Gelderd et al. [14] showed that HBO treatment following SCI led to less cavitation and better vascularized scars containing densely packed collagen fibers. Al-Waili et al. [15] reported that HBO application was beneficial in patients with vascular damage in the spinal cord. HBO also reduced apoptosis following SCI [16]. Topuz et al. [17] combined HBO treatment with hypothermia in rats with SCI and found a

Conclusion

In summary, HBO treatment is found to be beneficial for neurological recovery when applied after SCI. The rats that received HBO treatment after SCI showed higher BBB scores, lower histology scores, and significant changes in VEGF and CX43 levels. These results may help to understand, in part, some of the molecular mechanisms of HBO treatment on promoting neurological recovery in SCI rats and may be useful to improve the clinical application of HBO for SCI patients. However, detailed mechanisms

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  • Cited by (0)

    FDA device/drug status: Not applicable.

    Author disclosures: XL: Grant: Beijing Natural Science Foundation (7102062) (C, Paid directly to institution/employer). YZ: Grant: Beijing Natural Science Foundation (7102062) (C, Paid directly to institution/employer). ZW: Grant: Beijing Natural Science Foundation (7102062) (C, Paid directly to institution/employer). JY: Grant: Beijing Natural Science Foundation (7102062) (C, Paid directly to institution/employer). CG: Grant: Beijing Natural Science Foundation (7102062) (C, Paid directly to institution/employer). QS: Grant: Beijing Natural Science Foundation (7102062) (C, Paid directly to institution/employer).

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