Rhizoma drynariae total flavonoids (RDTF) are extracted from Drynaria fortunei J. Sm (D. fortunei), which was a Chinese herb commonly used to treat fractures and bruises. Modern pharmacological studies indicate flavonoids have anti-inflammatory effect in clinical practice. However, its active ingredients and the mechanisms of action are far from clear. The present study aims to determine whether RDTF can protect against intervertebral disc degeneration in a rat cervical intervertebral disc model and investigate the associated molecular mechanisms. Sprague Dawley (SD) rats were randomized into five groups: control group (CG, n = 8), intervertebral disc degeneration group (NG, n = 8), low-dose RDTF-treated group (LG, n = 8), medium-dose RDTF-treated group (MG, n = 8), and high-dose RDTF-treated group (HG, n = 8). Hematoxylin and eosin (HE) staining, immunohistochemistry (IHC), immunofluorescence, ELISA, Western blot and quantitative real time PCR (qRT-PCR) assays were used to investigate inflammatory, catabolic factors and the latent regulatory mechanism of the effects of RDTF on intervertebral disc cells. HE staining showed disc degeneration in all groups except CG, and the function was restored after RDTF treatment. IHC, Western blot, qRT-PCR, immunofluorescence and ELISA results showed that RDTF prevented intervertebral disc degeneration by suppressing mitogen-activated protein kinase (MAPK) pathway, which reduced expression of intracellular matrix metalloproteinases (MMPs), such MMP3, MMP13, and inflammatory factors including interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α). Notably RDTF inhibited extracellular matrix (ECM) degeneration by increasing expression of aggrecan and collagen type II and preventing the upregulation of collagen type I and III. It suggests that RDTF has a potential therapeutic effect on cervical spondylosis.

This diagram illustrates highlights of the work that Rhizoma drynaria flavonoids may inhibit intervertebral disc degeneration. Rhizoma drynaria flavonoids through MAPK pathway regulated the expression of MMP-13, MMP-3 LI-1β, TNF-α, Collagen I, Collagen III, Collagen II and aggrecan. Experimental methods included Hematoxylin and Eosin (HE) staining, Immunohistochemistry (IHC), Immunofluorescence, Elisa, Western blot and Quantitative real time PCR (qRT-PCR).