Controlled-release mitomycin C-polylactic acid film prevents epidural scar hyperplasia after laminectomy by inducing fibroblast autophagy and regulating the expression of miRNAs.

OBJECTIVE: To design a new controlled-release MMC-PLA film and explore whether and how this film could prevent epidural scar hyperplasia and adhesion in a post-laminectomy rat model.

MATERIALS AND METHODS: All procedures were performed under the approval and supervision of the Institutional Animal Care and Use Committee (IACUC) of Nanjing Medical University. A total of 120 Sprague-Dawley (SD) rats were randomly placed into four groups after laminectomy (each group=30 rats). In Group I, the laminectomy area was flushed with saline as a control; in Group II, 25 mg of PLA film was applied to the dura mater in the laminectomy area; in Group III, a cotton pad soaked with 0.01% MMC solution was kept on the laminectomy area; and in Group IV, 25 mg of PLA film containing 0.01% MMC was implanted on the laminectomy area. Magnetic resonance imaging (MRI), hematoxylin-eosin (HE) staining and Masson staining were used to evaluate scar adhesion and collagen deposition one month after the operation. Autophagy-related proteins, including autophagy-related gene 5 (ATG5), beclin 1, light chain-3B-2/1 (LC3B-2/1) and protein 53 (p53), were detected by Western blotting. A microRNA microarray analysis was performed to screen for scar tissue miRNAs, especially those associated with autophagy, and changes in expression were confirmed by reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS: A total of 112 rats recovered uneventfully from the surgery. MRI showed that the scar adhesion and scar area of the MMC-PLA group were significantly reduced compared with those of the PLA, MMC, and saline groups. Accordingly, scar adhesion and the deposition of collagen in the rats treated with MMC-PLA were also significantly reduced, as indicated by HE and Masson staining. In the scar tissue, the levels of autophagy-related proteins (ATG5, beclin 1, LC3B-2/1 and p53) were significantly elevated in the MMC-PLA group. Additionally, in the MMC-PLA group, the expression levels of miR-34a, miR-146a and miR-200 were significantly increased, while the levels of miR-16, miR-221 and miR-378a were significantly decreased.

CONCLUSIONS: The controlled-release MMC-PLA film could alleviate epidural scar hyperplasia after laminectomy; this outcome might be associated with increased autophagy and altered expression of miRNAs in the scar tissue.