TNF-α Coordinates Hematopoietic Stem Cell Survival and Myeloid Regeneration

Inflammation coordinates tissue regeneration via damaged cell removal and stem cell activation. Hematopoietic stem cells (HSCs) survive inflammatory stress that kills other blood cells, but the mechanisms underlying this effect remain poorly understood. Here, we find that tumor necrosis factor alpha (TNF-alpha) acts differently on HSCs and progenitors, thus facilitating hematopoietic clearance and promoting regeneration. We show that while inducing myeloid progenitor apoptosis, TNF-alpha promotes HSC survival and myeloid differentiation by activating a strong and specific p65-nuclear factor kappa B (NF-kappa B)-dependent gene program that primarily prevents necroptosis rather than apoptosis, induces immunomodulatory functions, and poises HSCs for myeloid cell production. These TNF-alpha-driven mechanisms are critical for HSC response to inflammatory stress but are also hijacked in aged and malignant HSCs. Our results reveal several TNF-alpha-mediated pro-survival mechanisms unique to HSCs, highlight an important role for necroptosis in HSC killing, and establish TNF-alpha as a major pro-survival and pro-regeneration factor for HSCs.