CST1 and viral infectious disease: Among the panel of DEGs, CST1, a cysteine proteinase inhibitor that belongs to type 2 cystatin family and is implicated in immune defense against bacterial, parasitic and viral infections,50–52 attracted our attention and was extrapolated to be the potential IFN regulator as it was preferentially expressed in hEnSCs rather than other cell types including hMSCs (Fig. 5a, b).