Experimental study on inhibitory effect of niacinamide on tumor necrosis factor-alpha-induced matrix degradation of annulus fibrous tissue in vitro.

The inhibitory effect of niacinamide on tumor necrosis factor-alpha (TNF-alpha) induced annulus fibrous (AF) degradation was assessed, and the mechanism of the inhibition was investigated. Chiba's intervertebral disc (IVD) culture model was established. Forty-eight IVDs from 12 adult Japanese white rabbits were randomly divided into 4 groups (12 IVDs in each group), and various concentrations of niacinamide and TNF-alpha were added to the medium for intervention: negative control group, niacinamide control group (0.5 mg/mL niacinamide), degeneration group (10 ng/mL TNF-alpha), and treatment group (0.5 mg/mL niacinamide and 10 ng/mL TNF-alpha). After one week's culture, AFs were collected for glycosaminoglycan (GS) content measurement, safranin O-fast green staining, and immunohistochemical staining for type I, II collagen and cysteine containing aspartate specific protease-3 (Caspase-3). It was found that the GS content in treatment group was increased by about 48% as compared with degeneration group (t=16.93, P<0.001), and close to that in niacinamide control group (t=0.71, P=0.667). Safranine O-fast green staining exhibited higher staining density and better histological structure of AF in the treatment group as compared with the degeneration group. Immunohistochemical staining for both Type I and II collagen demonstrated that lamellar structure and continuity of collagen in treatment group were better reserved than in degeneration group. Positive staining rate of Caspase-3 in AFs of negative control group, niacinamide control group, degeneration group and treatment group was 3.4%, 4.3%, 17.9% and 10.3% respectively. The positive rate in treatment group was significantly lower than in degeneration group (P<0.01). It was concluded that niacinamide could effectively alleviate TNF-alpha induced destruction and synthesis inhibition of matrix ingredients in AFs. The inhibition may be related with reduction of expression of Caspase-3. Thus, niacinamide is of potential for IVD degeneration clinical treatment.