ABSTRACT
BACKGROUND: Compressive stress can change the morphology and activity of cells, but whether the morphology and activity of nucleus pulposus cells change under hydrostatic pressure still needs further study. OBJECTIVE: To study the morphology and activity of human nucleus pulposus cells in vitro. METHODS: The human nucleus pulposus cells were separated, cultured and passed on for three generations, and pressurized for 2, 4 and 6 hours under the hydrostatic pressure of 0.3, 1, and 3 MPa. Then, the morphological changes and growth of the cells before and after pressurization were observed by inverted phase contrast microscope. Transmission electron microscope was used to observe the ultrastructural changes and differences of the cells. Cell counting kit-8 was used to detect the proliferation activity, morphology and activity of the cells under different hydrostatic pressures. RESULTS AND CONCLUSION: (1) Cell culture and passage: The growth curves of the first, second and third generations of human nucleus pulposus cells were S-shaped, and the cells proliferated fastest in a straight line from 3 to 7 days. The protuberances of the 5th and 6th generation cells were long shuttle shaped, grew slowly and degenerated. (2) Cell morphology: the human nucleus pulposus cells were shrunk under hydrostatic pressures of 0.3, 1, 3 MPa. At 0.3 and 1 MPa, the cells became slightly smaller and the morphology was basically complete; at 3 MPa, the cells were most obviously shrunk and the morphology was incomplete. The results showed that when the human nucleus pulposus cells were pressurized for 2, 4 and 6 hours under 0.3, 1 and 3 MPa hydrostatic pressures, the change of cell morphology was the most obvious under 3 MPa hydrostatic pressure, but there was no obvious change under the same hydrostatic pressure for different time. (3) Cell viability: Under 0.3 MPa hydrostatic pressure, the proliferation rate of human nucleus pulposus cells first increased and then decreased with the increase of time, and the cell proliferation rate reached the peak at 4 hours. Under 1 and 3MPa hydrostatic pressures, the proliferation rate of the cells gradually decreased with the increase of time, and the cell proliferation rate under 1 MPa hydrostatic pressure was significantly higher than that under 3 MPa hydrostatic pressure at the same action time (P < 0.05). These findings indicate that proper hydrostatic pressure stimulation helps to promote the proliferation of human nucleus pulposus cells, and long-term improperly high hydrostatic pressure stimulation can reduce the proliferation rate of human nucleus pulposus cells, leading to the occurrence of intervertebral disc degeneration.