Combination Therapy With Hyperbaric Oxygen and Erythropoietin Inhibits Neuronal Apoptosis and Improves Recovery in Rats With Spinal Cord Injury

Abstract

Background: Apoptosis plays an important role in various diseases, including spinal cord injury (SCI). Hyperbaric oxygen (HBO) and erythropoietin (EPO) promote the recovery from SCI, but the relationship between apoptosis and the combination therapeutic effect is not completely clear.

Objective: The purpose of this study was to investigate the effects of HBO and EPO on SCI and the mechanisms that underlie their therapeutic benefits.

Design: The study was designed to explore the effects of HBO and EPO on SCI through a randomized controlled trial.

Methods: Sixty young developing female Sprague-Dawley rats were randomly divided into groups of 12 rats receiving sham, SCI, HBO, EPO, or HBO plus EPO. The SCI model was modified with the Allen method to better control consistency. HBO was performed for 1 hour per day for a total of 21 days, and EPO was given once per week for a total of 3 weeks. Both methods were performed 2 hours after SCI. Locomotor function was evaluated with the 21-point Basso-Beattie-Bresnahan Locomotor Rating Scale, an inclined-plane test, and a footprint analysis. All genes were detected by Western blotting and immunohistochemistry. The level of cell apoptosis was determined by Hoechst staining.

Results: The results showed that HBO and EPO promoted the recovery of locomotor function in the hind limbs of rats by inhibiting the apoptosis of neurons. During this period, the expression of B-cell lymphoma/leukemia 2 protein (Bcl-2) increased significantly, whereas the expression of Bcl-2-associated X protein (Bax) and cleaved caspase 3 decreased significantly, indicating the inhibition of apoptosis. Meanwhile, the expression of G protein-coupled receptor 17 decreased, and that of myelin basic protein increased, suggesting that there may be a potential connection between demyelination and neuronal apoptosis.

Limitations: The limitations of the study include deviations in the preparation of SCI models; lack of reverse validation of molecular mechanisms; absence of in vitro cell experiments; and only one time point after SCI was studied.

Conclusions: HBO and EPO treatments are beneficial for SCI, especially when the 2 therapies are combined.