Tetramethylpyrazine Facilitates Functional Recovery after Spinal Cord Injury by Inhibiting MMP2, MMP9, and Vascular Endothelial Cell Apoptosis

Background: Spinal cord injury (SCI) is a major public health issue that leads to neurological dysfunctions and morbidities in patients. Tetramethylpyrazine (TMP) plays a neuroprotective role in SCI; however, the underlying mechanism has not been fully elucidated. Objective: In the present study, we aimed to investigate the mechanisms and therapeutic effects of TMP on SCI. Methods: A contusion SCI model was established that used a modified Allen's method. In the TMP group, TMP (200 mg/kg) was injected daily for 5 days post-injury, while in the Negative Control (NC) group, an equal volume of normal saline was injected. Hindlimb motor function was evaluated using the Basso, Beattie, Bresnahan (BBB) scale. The effects of TMP on protein levels of the matrix metalloproteinases 2 (MMP2) and 9 (MMP9), Bax and cleaved caspase-3 were determined by western blotting. Apoptotic changes in vascular endothelial cells were evaluated using immunofluorescence and TUNEL staining. Alterations in 3D vessel morphology after treatment with TMP were assessed by synchrotron radiation micro-CT (SR mu CT). Results: TMP treatment significantly improved recovery in hindlimb motor function and attenuated vascular endothelial cell apoptosis in rats with SCI. Additionally, TMP treatment markedly decreased the protein levels of MMP2 and MMP9, pro-apoptotic bax and cleaved caspase-3 while promoting angiogenesis, as evidenced by vessel visualization using SR mu CT. Conclusion: These results indicate that TMP attenuated SCI-induced neurological impairments by the down-regulation of the expression of MMP2 and MMP9 proteins, the inhibition of vascular endothelial cell apoptosis, and the promotion of angiogenesis.