TNFR2 upregulation-caused loss of cell polarity prevents differentiation of myeloid-derived suppressor cells with ageing

Differentiation blockage can cause expansion of myeloid-derived suppressor cells (MDSCs) with ageing. Cell polarity loss (apolarity) in old stem or progenitor cells prevents their differentiation; but whether and how cell polarity is lost in old MDSCs, subsequently affecting their mature differentiation remains elusive. Here, we show that TNFR2 upregulation in old MDSCs triggers JNK over-activation, resulting in apolarity, differentiation blockage, and expansion of MDSCs with ageing. We find that TNFR2 expression in MDSCs can be induced by pro-inflammatory factors of senescence-associated secretory phenotype (SASP) and Tnfr2 deficiency in old mice significantly attenuates MDSCs’ differentiation blockage. Elevating TNFR2 expression in young MDSCs can induce apolarity and impair their differentiation; whereas suppressing JNK activity in old MDSCs can partially reverse their polarity and restore their differentiation capability. Therefore, TNFR2 aberrant upregulation represents a general mechanism by which extrinsic SASP signals dysregulate intrinsic cell polarity behaviors to arrest MDSCs’ mature differentiation during ageing. To detect the gene expression of ageing MDSC, the splenic MDSCs were isolated from ageing mice of the WT, Tnfr1-/-, and Tnfr2-/- strains for further RNA-seq analysis.