Inflammatory licensing alters MSC metabolism of exogenous fatty acids and preserves immunomodulatory potency in lipid-rich environments

L Boland; J.A Ankrum

doi:10.1016/j.jcyt.2020.03.106

MSC immunomodulation has been central to the expanded use of MSCs within clinical trials. Inflammatory cytokine licensing of an anti-inflammatory MSC phenotype has emerged as a promising driver of enhanced MSC immunosuppressive capacity, however, the mechanism(s) that facilitate this enhancement, as well as critical modifiers of this licensing process are only beginning to emerge. Recent research has demonstrated that metabolic adaptations displayed by MSCs in response to inflammatory licensing are critical to the enhanced immunomodulatory profile of MSCs after licensing. In our previous work, we found that naïve, non-licensed MSCs became pro-inflammatory within lipid-rich environments. However, inflammatory licensing allowed MSCs to remain immunosuppressive and non-inflammatory within these same environments. In our current study, we hypothesize that alterations in the underlying metabolic programs elicited by inflammatory licensing are critical to the preservation of MSC immunomodulatory potency within lipid-rich environments. To test our central hypothesis, we performed a metabolomic screen using gas chromatography-mass spectroscopy to identify metabolic programs through relative abundance analyses within four MSC groups: naïve MSCs, naïve MSCs exposed to the fatty acid palmitate, licensed MSCs, and licensed MSCs exposed to palmitate. Palmitate alone was used as a representative fatty acid because it is the fatty acid in highest abundance within human serum and elevated serum levels are associated with the development of metabolic pathologies including type 2 diabetes. Six umbilical cord MSC donors were used and a total of 80 metabolites covering several critical nodes of central metabolism were assayed. Each treatment condition elicited a unique metabolic profile, with at least 5 or more metabolites showing significant differences in between-group comparisons. Interestingly, in response to palmitate exposure, naïve MSCs show less adaptation than their paired licensed counterparts, suggesting that licensing may enhance metabolic adaptability (A). Additionally, metabolites within the distal aspect of the TCA cycle [Aspartate (B), Malate (C), Fumarate (D), and Succinate (E)] showed differential regulation between naïve and licensed groups, indicating that this may be a critical pathway elicited by licensing that aids in the preservation of MSC immunomodulation within lipid-rich environments.

Inflammatory licensing alters MSC metabolism of exogenous fatty acids and preserves immunomodulatory potency in lipid-rich environments

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