Improving the Clinical Efficacy of Mesenchymal Stromal Cells

Mesenchymal Stromal Cells (MSCs) have been recognized for their prospective impact on regenerative medicine. MSCs possess a great clinical safety profile, ability to evade the immune system and capacity to differentiate into chondrogenic and osteogenic linages, as well as other valuable characteristics. Over one thousand clinical trials have utilized MSCs, however many have failed to reach clinical expectations. To improve MSCs clinical efficacy, glycoengineering is being explored to alter cell function safely and reversibly. This includes post-translational modification of N-linked glycans on the cell surface of which have previously been shown to impact cell function including migration, survival, and differentiation potential. Terminal sialic acid in hybrid or complex N-glycoforms has been shown to be relevant in various types of cancer, but its role in non-malignant cells remains poorly understood. The goal of this study is to determine the role of sialylated N-glycans in MSCs to improve therapeutics. We show that IFN-gamma and medium low in fetal bovine serum (FBS) increase sialylated N-glycans, while PDGF- BB reduces them. In addition, IFN-gamma, low FBS and PDGF affect mRNA and protein levels of sialyltransferases suggesting sialylation of N-glycans is regulated by transcriptional control of sialyltransferases. We show that 3F-Neu5Ac, a sialic acid analog, effectively inhibits sialyltransferases. As compared to controls, MSCs treated with 3F-NeuAc show an increase in adhesion as well as migration as assessed by videomicroscopy and wound/scratch assays, suggesting that reducing sialylations is an effective method to increase the migration potential of MSCs. However, we found that 3F-NeuAc pre- and continuous treatment show an inhibitor effect on osteogenic and adipogenic differentiation. These experiments suggest sialylations are highly regulated in MSCs and that the glycoengineering of MSCs to reduce sialylated N-glycans to improve migration could positively affect their therapeutic potential.