Transplantation of bone marrow mesenchymal stem cells reduces GluR1 expression in the hippocampus and amygdala and affects secretion of stress-related hormones in rats with spinal cord injuries: a potential anti-chronic stress mechanism

There have been many studies about bone marrow mesenchymal stem cell (BMSCs) transplantation therapy for spinal cord injuries (SCI), achieving positive results both in laboratory and clinical applications. However, its exact repair mechanisms are still under investigation. The authors of this present study hypothesized that chronic stress plays an important role in SCI and investigated a potential anti-chronic stress mechanism of transplantation of BMSCs into rat SCI. A total of 48 adult male SD rats were randomly and equally allocated into three groups (control, model, and treatment). Lower thoracic partial SCI was induced in both the model and treatment group, while the control group received only laminectomy. The control and treatment group were injected with 100 mu l of Hank's buffered saline solution containing 1 million rat BMSCs into the L4-5 intervertebral space. The model group received the same amount of Hank's buffered saline solution via injection. Hind limb motor function was evaluated by Basso, Beattie, and Bresnahan (BBB) scale while enzyme-linked immunosorbent assay (ELISA) detection was performed for these stress-related hormones: plasma adrenocorticotropic hormone (ACTH), norepinephrine (NE), epinephrine (E), and serum corticosterone (CORT). Immunohistochemistry staining was performed for Glutamate (Glu) receptor 1 (GluR1) in the hippocampus and amygdala of rat brains. Following BMSCs transplantation, motor function of hind limbs of rats in the treatment group achieved sustained restoration. Additionally, 14 days and 28 days after transplantation, levels of plasma ACTH, NE, E, and serum CORT in the treatment group were significantly decreased compared with that in the model group (P<0.05). Positive rates of GluR1 in the hippocampus and amygdala of the treatment group were also dramatically reduced compared with that in the model group (P<0.05). Results showed that BMSCs transplantation is beneficial for motor function recovery of hind limbs in rats with SCI. Furthermore, it may exert a preventive role on chronic stress by downregulating GluR1 expression in the central nervous alpha-amino hydroxymethyl-oxazole propionic acid (AMPA) channel and inhibiting secretion of stress-related hormones, implying a potential anti-chronic mechanism.