Abstract
BackgroundEpidural fibrosis is a common complication after laminectomy. It is associated with intractable lower back pain and additional complications. To date, no study has evaluated whether the local application of rapamycin (RAPA) can inhibit fibroblast proliferation and reduce epidural scar adhesion after laminectomy. The results of the present study showed that the local application of RAPA reduces epidural fibrosis after laminectomy in rats.MethodsIn this study, 32 male Sprague-Dawley rats were randomly divided into four groups (0.2 mg/ml RAPA-treated group, 0.1 mg/ml RAPA-treated group, 0.05 mg/ml RAPA-treated group and physiological saline group). Laminectomy was performed at the level of lumbar segment 1 to 2, and different concentrations of RAPA or saline were applied to the laminectomy sites for 10 min. Four weeks after laminectomy, the rats were sacrificed, and the degrees of epidural adhesion in each group were evaluated. Macroscopic assessment, analysis of hydroxyproline content, and histological analysis were used to determine the therapeutic effect of the local application of RAPA on the inhibition of fibroblast proliferation and the reduction of epidural fibrosis after laminectomy. Next, we cultured fibroblasts from epidural scar tissues of rats that had undergone laminectomy. Fibroblasts were exposed to the indicated concentrations of RAPA, and western blotting and TUNEL assays were used to assess the effects of RAPA on inhibiting fibroblasts proliferation and promoting fibroblast apoptosis.ResultsThe results of macroscopic assessments, analysis of hydroxyproline content, and histological analyses indicated that RAPA significantly inhibited fibroblast proliferation and reduced epidural fibrosis in the treated groups in the rat model. The western blotting results indicated that the expression levels of the pro-apoptotic proteins cleaved-PARP and Bax were up-regulated, whereas those of Bcl-2 were reduced. TUNEL assay indicated that the apoptosis rates of fibroblasts were significantly increased after exposure to the indicated concentrations of RAPA.ConclusionsThe local application of RAPA reduced epidural fibrosis after laminectomy by inhibiting the proliferation of fibroblasts, stimulating their apoptosis, and decreasing collagen synthesis. This protocol may be used in new clinical treatment strategies to reduce epidural fibrosis after laminectomy.
Highlights
Epidural fibrosis is a common complication after laminectomy
Moderate scar adhesion was seen in the 0.1 mg/ml RAPA group; the tissues could be dissected by manual traction with less bleeding
In both the control group and the 0.05 mg/ml RAPA group, dense epidural scar tissue and compact collagen tissues were found in the laminectomy sites, and the scar tissues were widely adhered to the dura mater and dorsal muscle
Summary
Epidural fibrosis is a common complication after laminectomy. It is associated with intractable lower back pain and additional complications. Extensive epidural fibrosis is a troublesome complication after laminectomy It can cause various clinical conditions, such as failed back pain surgery syndrome (FBSS), which is characterized by chronic radicular nerve or lower back pain [1,2,3]. Many types of biological and synthetic materials, such as polymethyl methacrylate, polylactic acid, autologous leather, silastic silicone, and fat grafts, have shown anti-fibrotic effects [6,7,8,9,10] Pharmaceutical agents, such as mitomycin C, hydroxycamptothecine, colchicine, steroid hormone and anti-inflammatory agents, have been used to reduce epidural fibrosis [11,12,13,14]. It has been reported that macrolide antibiotics, such as azithromycin and tacrolimus (FK506), exhibit effectiveness in reducing the fibrosis of epidural scars [13, 15]
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