Proliferative Activity of Healthy and Degenerated Intervertebral Disc Cells in vitro under Bone Morphogenetic Proteins’ Influence: Implications for Cell Therapy

The aim of the study was to evaluate the effect of bone morphogenetic proteins (BMP) on the proliferative activity of healthy and degenerated cells of the intervertebral disc (IVD) in vitro.

Materials and Methods. Cells obtained from the human annulus fibrosus and the nucleus pulposus of healthy and degenerated intervertebral discs were cultured in the absence and presence of BMP-2, BMP-7, and BMP-14. A daily cell count was performed using micrographs obtained by phase contrast microscopy and the Fiji program. On day 4, cells were fixed and stained with Alexa Fluor 633 phalloidin (for F-actin) and DAPI (for nuclear DNA), and imaged using laser confocal microscopy. The rate of cell growth was calculated at their exponential growth phase by mathematical modeling.

Results. In the presence of BMP-2, 7, and 14, insignificant changes in the growth rates of cells from the annulus fibrosus and the nucleus pulposus of the IVD (both healthy and degenerated) were noted. Changes in the proliferative activity were found in healthy cells of the annulus fibrosus supplemented with BMP-2, 7, and 14 (p<0.01), and also in degenerated cells of the nucleus pulposus in the presence of BMP-14 (p<0.01). Proliferative activity of degenerated cells from the nucleus pulposus was reduced in comparison with healthy cells (p=0.03), while in annulus fibrosus cells there was no significant difference between the two compared groups. The addition of BMP did not restore proliferative activity of cells from the degenerated nucleus pulposus to the level of healthy cells. Morphological characteristics of the cells were similar: both, the nucleus pulposus cells and the annulus fibrosus cells resembled fibroblasts by having spread-eagle, stellate, spindle-like shapes with long protrusions.

Conclusion. Minor changes in the proliferative activity of IVD cells co-incubated with BMP-2, 7, and 14 were observed. Bone morphogenetic proteins had no significant effect on proliferation of IVD cells, which can be regarded as a positive factor under conditions of nutrient deficiency and reduced nutrient transport in the disc. The observed differences in growth rate between the nucleus pulposus cells and the annulus fibrosus cells may be due to different degrees of tolerance to degeneration or reflect the predominant role of the nucleus pulposus‎ in the cellular degeneration of the IVD.

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Bardonova L.A., Belykh E.G., Giers M.B., Preul M.C., Byvaltsev V.A. Proliferative Activity of Healthy and Degenerated Intervertebral Disc Cells in vitro under Bone Morphogenetic Proteins’ Influence: Implications for Cell Therapy. Sovremennye tehnologii v medicine 2018; 10(2): 76, https://doi.org/10.17691/stm2018.10.2.08