APOPTOSIS, NUTRITION, AND METABOLISM OF TRANSPLANTED INTERVERTEBRAL DISC CELLS

ABSTRACT Introduction: Apoptosis is a contributing factor to degenerating intervertebral disc (IVD). Disc regeneration has been attempted by transplanting cells into the disc, with some gains in disc height achieved in animal models. Here, we study whether the apoptotic microenvironment affects the transplanted disc cells. Methods: Human annulus fibrosus (AF) and nucleus pulposus (NP) cells were grown in media then starved for 5 days in vitro by not changing the media. Three aspects of apoptotic cell influence on the transplanted cells were tested in a total of 32 samples: 1) the effect of apoptotic cytokines in the media, 2) reduced glucose in the media, and 3) apoptotic cell bodies in the flask. The Trypan Blue, AlamarBlue®, and 1,9-Dimethyl-Methylene Blue assays for sulfated glycosaminoglycan (sGAG) content were performed (n=4). Results: There were significant decreases in cell viability between the control, 25% conditioned media (CM) and starved control group. There were no significant differences in cell number, metabolic activity or sGAG production in cells grown in different conditioned media compared to cells grown in complete media. The cells of the control decreased in viability and number over the 5 days without feeding, then improved dramatically when feeding was resumed. Flasks that received transplanted cells in addition to renewed feeding did not recover as much as the cells in the re-fed group. Conclusions: Cytokines from starved cells negatively impact on the viability of healthy cells. Starving cells that receive new sources of nutrition have even higher viability than transplanted cells. This indicates that altering and improving the nutrient supply problem in the IVD could be a valuable option. Level of Evidence III; Case control studyg