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Comparison of Oxygen Consumption Rates of Nondegenerate and Degenerate Human IVD Cells

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Abstract

Study Design.

In vitro measurements of the oxygen consumption rates (OCR) of human intervertebral disc (IVD) cells.

Objective.

To determine the differences in the OCR of nondegenerate and degenerate human annulus fibrosus (AF), nucleus pulposus (NP), and cartilage endplate (CEP) cells at different glucose concentrations.

Summary of Background Data.

The avascular nature of the IVD creates a delicate balance between rate of nutrient transport through the matrix and rate of disc cell consumption necessary to maintain tissue health. Previous studies have shown a dependence of OCR for animal (e.g. bovine and porcine) IVD cells on oxygen level and glucose concentration. However, the OCR of nondegenerate human IVD cells compared to degenerate human IVD cells at different glucose concentrations has not been investigated.

Methods.

IVD cells were isolated from the AF, NP, and CEP regions of human cadaver spines and surgical samples. The changes in oxygen concentration were recorded when cells were sealed in a metabolic chamber. The OCR of cells was determined by curve fitting using the Michaelis-Menton equation.

Results.

Under identical cell culture conditions, the OCR of degenerate human IVD cells was 3–5 times greater than that of nondegenerate human IVD cells. The degenerate IVD cells cultured in low glucose medium (1 mM) exhibited the highest OCR compared to degenerate cells cultured at higher glucose levels (i.e., 5 mM, 25 mM), while no significant differences in OCR was found among the nondegenerate IVD cells for all glucose levels.

Conclusions.

Considering the significantly higher OCR and unique response to glucose of degenerate human IVD cells, the degeneration of the IVD is associated with a cell phenotypic change related to OCR. The OCR of IVD cells reported in this study will be valuable for understanding human IVD cellular behavior and tissue nutrition in response to disc degeneration.

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