Inflammatory memory of stem cells: implications for hematologic diseases

Immunological memory in adaptive and innate immune cells is well characterized, enabling enhanced responses upon secondary challenges. However, it has only been recently appreciated that the nonimmune target cells of inflammation, particularly organ-specific stem cells (SCs), also exhibit memory of previous inflammatory exposures. Previous inflammation experience imprints on the SCs and influences their regenerative potential and responses to subsequent inflammatory insults. This phenomenon has been observed in hematopoietic, intestinal, and skin epithelial SCs, with profound implications for tissue homeostasis, disease progression, and therapeutic strategies. Herein, we expand and develop the notion of inflammatory memory of SCs and explore recent insights in the field. We discuss the emerging understanding of the molecular underpinnings and their potential clinical and biological implications. Inflammatory memory is driven by spatiotemporal changes in gene loci and transcription regulated by DNA and histones' epigenetic modifications, metabolic reprogramming, and chromatin accessibility changes. Understanding these mechanisms is critical for improving the outcomes of hematologic diseases, hematopoietic SC transplantation, and cellular immunotherapies.