biostudies-literatureUnknown25(1)Koide SVetenskapsradetCancerfondenIsolation of long-term hematopoietic stem cell (HSC) is possible by utilizing flow cytometry with multiple cell surface markers. However, those cell surface phenotypes do not represent functional HSCs after <i>in vitro</i> culture. Here we show that cultured HSCs express mast cell-related genes including <i>Cd244</i>. After <i>in vitro</i> culture, phenotypic HSCs were divided into CD244^- and CD244⁺ subpopulations, and only CD244^- cells that have low mast cell gene expression and maintain HSC-related genes sustain reconstitution potential. The result was same when HSCs were cultured in an efficient expansion medium containing polyvinyl alcohol. Chemically induced endoplasmic reticulum (ER) stress signal increased the CD244⁺ subpopulation, whereasiScience103603https://www.ebi.ac.uk/biostudies/studies/S-EPMC8718822biostudies-literatureCD244 expression represents functional decline of murine hematopoietic stem cells after <i>in vitro</i> culture.PMC8718822Zheng ZMiharada KRadulovic VSaito KIwama AKoide SLang SSoneji SSigurdsson VfalseCD244 expression represents functional decline of murine hematopoietic stem cells after <i>in vitro</i> culture.Isolation of long-term hematopoietic stem cell (HSC) is possible by utilizing flow cytometry with multiple cell surface markers. However, those cell surface phenotypes do not represent functional HSCs after <i>in vitro</i> culture. Here we show that cultured HSCs express mast cell-related genes including <i>Cd244</i>. After <i>in vitro</i> culture, phenotypic HSCs were divided into CD244^- and CD244⁺ subpopulations, and only CD244^- cells that have low mast cell gene expression and maintain HSC-related genes sustain reconstitution potential. The result was same when HSCs were cultured in an efficient expansion medium containing polyvinyl alcohol. Chemically induced endoplasmic reticulum (ER) stress signal increased the CD244⁺ subpopulation, whereas2022-01-01T00:00:00Z2022 Jan2026-05-09T14:06:12.239Z2025-04-04T08:53:02.848ZS-EPMC87188223500554810.1016/j.isci.2021.103603