BACKGROUND CONTEXT: Mesenchymal Stem Cells (MSCs) secretome or conditioned
medium (CM) is a complex cocktail of different molecules, some of which, particularly those con-
tained in extracellular vesicles, already have proven therapeutic applications.
PURPOSE: CM may well represent promising therapy for discogenic pain and the intention of this
work is to assess its therapeutic potential using an in vitro model of this condition.
STUDY DESIGN: This is an experimental study.
METHODS: Our in vitro model comprised Nucleus Pulposus (NP) and Annulus Fibrosus (AF)
cells inflamed with TNF. To assess the potential therapeutic value of CM and its components,
extracellular vesicles (EVs) and soluble culture fraction (SF), cell inflammation took place under 3
different conditions: either in the presence of whole CM, isolated EVs or SF, and concentrations of
pro-inflammatory cytokines, metalloproteinases (MMPs) and neurotrophic factors produced in all
3 cases were compared.
RESULTS: In the presence of whole CM, both in vitro gene expression by the NP and AF test cells
and analysis of their protein content showed high modulatory effects on inflammation and MMP
inhibition. The presence of EVs and SF showed similar but much smaller effects, and this was par-
ticularly marked in the case of NP cells.
CONCLUSIONS: Our results show that, compared to EVs and SF, the presence of whole CM has
the greatest positive effect on the modulation of pro-inflammatory and catabolic factors. These
observations suggest that CM could protect against inflammation and the resulting intervertebral
disc (IVD) degeneration that leads to discogenic pain.
CLINICAL SIGNIFICANCE: Many patients' expectations are not met by current non-operative
and surgical treatments for discogenic low back pain. We propose the use of the MSCs secretome
