Increased Apoptosis, Expression of Matrix Degrading Enzymes and Inflammatory Cytokines of Annulus Fibrosus Cells in Genetically Engineered Diabetic Rats: Implication for Intervertebral Disc Degeneration

IntroductionDiabetes mellitus is thought to be an important etiologic factor in intervertebral disc degeneration. However, what is little known is whether diabetes has an effect on annulus fibrosus (AF) cells. The purpose of our study was to investigate the effect of diabetes mellitus on apoptosis, expression of matrix degrading enzymes and inflammatory cytokines of AF cells in age-matched genetically engineered OLETF (diabetic) and LETO (control) rats. Material and MethodsLumbar disc tissues (L1–2 through L5–6) were obtained from 6-month old OLETF and LETO rats (10 each). We examined the AF cells and tissues using Masson trichrome stain, TUNEL, Western blotting, and reverse transcription polymerase chain reaction. The apoptosis index and the degree of expression of matrix degrading enzymes and inflammatory cytokines of AF cells were evaluated by semiquantitative method. ResultsOLETF rats showed increased body weight and abnormal 2-hour glucose tolerance tests compared with LETO rats. The apoptosis index and the degree of expression of Fas of AF cells were statistically higher in the OLETF rats. The degree of expression of matrix metalloproteinase-1, -2, -3 and -13 and tissue inhibitor of metalloproteinase-1 and -2 was statistically higher in the OLETF rats. The expression of interleukin-1 and -6 and tumor necrosis factor-α was statistically higher in the OLETF rats. Finally, histological analysis showed more severe fibrosis and loss of lamellar pattern in AF tissues of OLETF rats. ConclusionOur results suggest that diabetes mellitus is associated with increased apoptosis and expression of matrix degrading enzymes and inflammatory cytokines in AF cells. This results in more severe fibrosis and loss of lamellar pattern of AF, which leads to intervertebral disc degeneration. Strict DM control might be important to delay or prevent early intervertebral disc degeneration in patients with DM.