Standardisation of basal medium for reproducible culture of human annulus fibrosus and nucleus pulposus cells

BACKGROUND: The lifetime prevalence of degenerative disc disease is dramatically high. Numerous investigations on disc degeneration have been performed on cells from annulus fibrosus (AF) and nucleus pulposus (NP) of the intervertebral disc (IVD) in cell culture experiments utilising a broad variety of basal culture media. Although the basal media differ in nutrient formulation, it is not known whether the choice of the basal media itself has an impact on the cell’s behaviour in vitro. In this study, we evaluated the most common media used for monolayer expansion of AF and NP cells to set standards for disc cell culture. METHODS: Human AF and NP cells were isolated from cervical discs. Cells were expanded in monolayer until passage P2 using six different common culture media containing alpha-Minimal Essential Medium (alpha-MEM), Dulbecco’s Modified Eagle’s Medium (DMEM) or Ham’s F-12 medium (Ham’s F-12) as single medium or in a mixture of two media (alpha/F-12, DMEM/alpha, DMEM/F-12). Cell morphology, cell growth, glycosaminoglycan production and quantitative gene expression of cartilage- and IVD-related markers aggrecan, collagen type II, forkhead box F1 and keratin 18 were analysed. Statistical analysis was performed with two-way ANOVA testing and Bonferroni compensation. RESULTS: AF and NP cells were expandable in all tested media. Both cell types showed similar cell morphology and characteristics of dedifferentiation known for cultured disc cells independently from the media. However, proceeding culture in Ham’s F-12 impeded cell growth of both AF and NP cells. Furthermore, the keratin 18 gene expression profile of NP cells was changed in alpha-MEM and Ham’s F-12. CONCLUSION: The impact of the different media itself on disc cell’s behaviour in vitro was low. However, AF and NP cells were only robust, when DMEM was used as single medium or in a mixture (DMEM/alpha, DMEM/F-12). Therefore, we recommend using these media as standard medium for disc cell culture. Our findings are valuable for the harmonisation of preclinical study results and thereby push the development of cell therapies for clinical treatment of disc degeneration.