Interaction of potato-derived RG-I with galectin-3 and gene regulation in human mesenchymal stem cells
Background: Mesenchymal stem cells (MSC) play a vital role in bone regeneration. Poly-(l-lactide-co-e-caprolactone) scaffolds functionalised with modified rhamnogalacturonan-I (RG-I) potato pectin, can modulate inflammation and promote bone regeneration in-vitro and in-vivo by modulating the action of the galactoside-binding galectin-3. In this study, we determined the binding affinity to galectin-3 of potato unmodified RG-I (PU) and its arabinose-deficient form (PA) and investigated their in-silico effect on MSC gene expression in relation to galectin-3. Methods: The binding affinity of RG-I (PU and PA) to galectin-3 was assessed by tryptophan fluorescence spectroscopy. Human MSC (hMSC) isolated from the bone marrow of elderly patients (>60yrs), were analysed by transcriptomic profiling. The effect of PA on gene expression was assessed in-silico by the ingenuity pathway analysis (IPA). Results: RG-I binds to galectin-3 with a binding affinity of 8.66x10-6 M. Galactose sidechains of PA resulted in ~10-fold increased binding of RG-I to galectin-3 compared with PU. Forty-two genes were found to be differentially expressed (DE) in hMSCs treated with PU and PA with a false-discovery rate (FDR)<0.1. IPA of these DE genes including LGALS3, encoding for galectin-3, showed enrichment for organismal disorders-abnormalities, connective tissue and skeletal muscular disorders, immunological and inflammatory diseases, and identified three gene networks: infectious diseases, immune & inflammatory response and cell cycle control.  Conclusions: This study indicates that modified potato pectin can regulate the expression of a broad range of genes, including galectin-3, that are involved in cellular, inflammatory, and immunological functions of MSCs and may potentially be used to promote bone regeneration via modulation of inflammation.