Abstract: Objective To investigate the effects of different cyclic tensile strains on the proliferation and expression of bone marrow stromal cells (BMSCs)- cocultured human degenerated anulus fibrosus (AF) cells. Methods AF cells were isolated from a patient with degenerated intervertebral disc degeneration (IVD), which were co-cultured with BMSCs. The solely cultured AF cells were used as control group. The two groups of cells were expanded in monolayer, and cyclically strained for 3 hours, which were applied 0, 5%, 10%, 15% and 20% strains at a frequency of 0.25 Hz using BioDynamic test instrument. A flow cytometry method was used to examine the AF cell proliferation at 24 hours followed the application of cyclic tensile strains. After the total RNA was extracted, real-time PCR technology was used to detect the gene expression of collagen Ⅰ and aggrecan. Results Under the same appropriate stress, the proliferative index (PI), the proportion of cells in the period of DNA synthesis, the expression of collagen Ⅰ and aggrecan were significantly higher in the co-cultured group than those of control group (P＜0.05). However, the best mechanical stimulation was different in the two groups. For the AF cells, the peaks of PI, the proportion of cells in the period of S period, the expression of collagen Ⅰ and aggrecan were found in the 10% strain group, while for the co- cultured cells, they were found in the 15% strain group. Conclusion Coculturing with BMSCs has a positive effect on the proliferation and expression of human degenerative fibrous ring cells, which can protect AF cells from bad stress stimulation.

Key words: intervertebral disk displacement, cells, cultured, cell proliferation, intervertebral disc degeneration, cyclic tensile strain, anulus fibrosus cells, co-culture, BMSCs