Dose- and time-dependent effect of high glucose concentration on viability of notochordal cells and expression of matrix degrading and fibrotic enzymes

Diabetes mellitus is an important aetiological factor in intervertebral disc degeneration. The disappearance of notochordal cells in the nucleus pulposus is thought to be the starting point for intervertebral disc degeneration. A cellular effect of diabetes mellitus on apoptosis of notochordal cells and intervertebral disc degeneration has been recently reported. However, how the duration and severity of diabetes mellitus affects viability of notochordal cells and intervertebral disc degeneration is still unknown . Rat notochordal cells were isolated, cultured, and placed in either 10 % foetal bovine serum (FBS) (normal control) or 10 % FBS plus three different high glucose concentrations (0.1 M, 0.2 M, and 0.4 M) (experimental conditions) for one, three, five and seven days, respectively. We identified and quantified the degree of proliferation and apoptosis, caspase activities, and cleavages of Bid and cytochrome-c. In addition, we examined the cells for expression of matrix metalloproteinases (MMPs) and their tissue inhibitors of metalloproteinases (TIMPs). Each three high glucose concentrations significantly decreased proliferation and increased apoptosis of notochordal cells from culture days one to seven in a dose-dependent manner. Compared with those of 10 % FBS, caspase-9 and -3 activities and cleavage of Bid and cytochrome-c were significantly increased in each three high glucose concentrations, accompanied by increased expression of MMP-1, -2, -3, -7, -9, and -13 and TIMP-1 and -2. High glucose concentration significantly decreased proliferation and increased apoptosis of notochordal cells via the intrinsic pathway with dose- and time-dependent effects. We also found that expression of MMPs and TIMPs was increased with dose- and time-dependent effects. Therefore, these results suggest that aggressive glucose control from an early stage of diabetes mellitus should be recommended to prevent or limit intervertebral disc degeneration.