RESUMO
BACKGROUND: The miR-21 has been implicated in the process of neuroinflammation as well as neuropathic pain. OBJECTIVES: To explore the relationship between the plasma and local expression of miR-21 with disease severity of lumbar disc herniation (LDH) patients with sciatic pain. MATERIAL AND METHODS: Ninety-two LDH patients with sciatic pain and 25 scoliosis patients as painless controls were enrolled in the current study. Samples from nucleus pulposus (NP), annulus fibrosus (AF) and soft tissues around nerve root (STANR) were obtained. The plasma and local expressions of miR-21 were detected with quantitative reverse transcription polymerase chain reaction (qRT-PCR). The visual analogue scale (VAS) for lumbar pain and leg pain, and Japanese Orthopedic Association (JOA) score were selected to evaluate the clinical severity. The degree of disc compression on nerve was evaluated using the Pfirrmann grade based on the magnetic resonance imaging (MRI) findings. For the convenience of analysis, LDH patients with sciatic pain were classified into a severe pain (SP) group (VAS ≥ 6) and a mild-moderate pain (MP) group (VAS < 6). Receiver operating characteristic (ROC) curve analysis was performed to detect the potential diagnostic power of miR-21 with regard to the Pfirrmann grade. RESULTS: There were no significant differences in serum miR-21 expressions among SP LDH patients, MP LDH patients and scoliosis painless controls. Local expressions of miR-21 in STANR, AF and NP were all drastically upregulated in the SP group in comparison with the MP group and scoliosis painless group. Local NP and STANR miR-21 expressions were positively associated with the Pfirrmann grade. Local miR-21 expressions in STANR and AF were positively associated with VAS score and negatively related to JOA score. The ROC curve analysis indicated that both STANR and AF miR-21 expressions may serve as significant diagnostic factors for the Pfirrmann grade. CONCLUSIONS: Increased local miR-21 expressions are linked with clinical severity of LDH in patients with sciatic pain.