Hematopoietic Stem Cells Are the Major Source of Multilineage Hematopoiesis in Adult Animals

“The fraction of labeled Tom+ cells in myeloid progenitors and granulocytes (Grans) from Pdzk1ip1-CreER R26Tom/Tom reporter mice analyzed by serial BM biopsy.”

“Continuous blood development (hematopoiesis) is particularly important for the immune system, in which myeloid cells such as granulocytes, monocytes, and dendritic cells (DCs) are very short lived (Geering et al., 2013; Geissmann et al., 2010).”

“Whereas the original definition of long-term HSCs reflected their capacity to reconstitute primary recipients (Morrison and Weissman, 1994; Spangrude et al., 1988), only a fraction of those HSCs were capable of reconstituting secondary recipients (Oguro et al., 2013; Yamamoto et al., 2013).”

“As in the case of Pdzk1ip1-GFP+ cells, the labeled Tom+ cells were significantly enriched among the CD34−/lo HSCs (Wilson et al., 2008) (Fig.”

“The only exceptions are cell types that develop primarily during embryogenesis, such as tissue macrophages (MF) (Ginhoux and Jung, 2014) and innate-like lymphocytes such as B-1a cells (Montecino-Rodriguez and Dorshkind, 2012).”

“Second, we found that type I interferon, a known inducer of HSC proliferation (Essers et al., 2009; Walter et al., 2015), accelerated multilineage HSC differentiation.”

“3H), consistent with recent observations (Acar et al., 2015; Ding and Morrison, 2013).”

“Given the broad distribution of sinusoids in the BM (Kunisaki et al., 2013), the identity of cell types and vessels adjacent to Tom+ HSCs still remains to be determined.”

“…activity in the BM of normal adult mice is contained in a small subset of Lineage marker (Lin)− Sca-1+ c-Kit+ (LSK) cells (Ikuta and Weissman, 1992; Morrison and Weissman, 1994) that express high levels of CD150 (Slamf1) and endothelial protein C receptor (EPCR) but low levels of CD135 (Flt3),…”

“This agrees with a relatively low but nevertheless considerable proliferation of all HSCs in the steady state (Cheshier et al., 1999; Kiel et al., 2007; Passegue et al., 2005; Wilson et al., 2008) and with the substantial label dilution observed in our experiments.”

“Thus, clonal cell analysis using transposon-mediated ‘‘barcoding’’ suggested that granulocyte development is completely uncoupled from theHSCactivity (Sun et al., 2014).”

“Peripheral T and B lymphocytes are relatively long-lived and may be sustained in part by homeostatic proliferation, yet they require the input of new cells to maintain a diverse polyclonal repertoire of antigen specificities (Montecino-Rodriguez et al., 2013).”

“If labeled cells represent a random sampling of the HSC population, their frequency would remain constant over time, as observed previously (Busch et al., 2015).”

“Whereas the original definition of long-term HSCs reflected their capacity to reconstitute primary recipients (Morrison and Weissman, 1994; Spangrude et al., 1988), only a fraction of those HSCs were capable of reconstituting secondary recipients (Oguro et al., 2013; Yamamoto et al., 2013).”

“3H), consistent with recent observations (Acar et al., 2015; Ding and Morrison, 2013).”

“Conversely, GFP+ cells expressed lower levels of CD34 and CD229 and higher levels of EPCR than the GFP− cells (Fig 1F).”

“Several genetic markers were recently developed to identify HSC subsets with a particular lineage bias (Vwf, (Sanjuan-Pla et al., 2013)) or a superior reconstitution capacity (Hoxb5, (Chen et al., 2016)) during primary transplantations.”

“Transplantation-competent HSCs are less proliferative than downstream progenitors (Cheshier et al., 1999; Passegué et al., 2005; Wilson et al., 2008) and are localized in specific BM microenvironment(s) termed the HSC niche (Boulais and Frenette, 2015).”

“The HSC activity in the BM of normal adult mice is contained in a small subset of Lineage marker (Lin)− Sca-1+ c-Kit+ (LSK) cells (Ikuta and Weissman, 1992; Morrison and Weissman, 1994) that express high levels of CD150 (Slamf1) and endothelial protein C receptor (EPCR) but low levels of CD135…”

“The transplantation of ESLAM cells was done essentially as described (Dykstra et al., 2007; Kent et al., 2009).”

“Second, we found that type I interferon, a known inducer of HSC proliferation (Essers et al., 2009; Walter et al., 2015), accelerated multilineage HSC differentiation.”

“…uthor M anuscript A uthor M anuscript The BM of adult mammals maintains a rare population of hematopoietic stem cells (HSCs) that can permanently reconstitute blood formation when transferred into lethally irradiated or otherwise myelosuppressed hosts (Eaves, 2015; Shizuru et al., 2005).”

“However, these phenotypically defined HSCs are heterogeneous in their differentiation potential and self-renewal capacity, as revealed by single-cell transplantation (Benz et al., 2012; Challen et al., 2010; Dykstra et al., 2007; Morita et al., 2010) and genetic reporters (Chen et al.”

“Transplantation-competent HSCs are less proliferative than downstream progenitors (Cheshier et al., 1999; Passegue et al., 2005; Wilson et al., 2008), and are localized in specific BM microenvironment(s) termed the HSC niche (Boulais and Frenette, 2015).”

“Pdzk1ip1 (also known as Map17) is expressed in the murine HSC population but is strongly reduced in more differentiated cells or in mobilized HSCs (Cabezas-Wallscheid et al., 2014; Forsberg et al., 2010; Wilson et al., 2015).”

“However, these phenotypically defined HSCs are heterogeneous in their differentiation potential and self-renewal capacity, as revealed by single-cell transplantation (Benz et al., 2012; Challen et al., 2010; Dykstra et al., 2007; Morita et al., 2010) and genetic reporters (Chen et al.”

“This agrees with a relatively lowbut nevertheless considerable proliferation of all HSCs in the steady state (Cheshier et al., 1999; Kiel et al., 2007; Passegué et al., 2005;Wilsonet al., 2008) andwith the substantial label dilution observed in our experiments.”

“The only exceptions are cell types that develop primarily during embryogenesis, such as tissue macrophages (MF) (Ginhoux and Jung, 2014) and innate-like lymphocytes such as B-1a cells (Montecino-Rodriguez and Dorshkind, 2012).”

“As in the case of Pdzk1ip1-GFP+ cells, the labeled Tom+ cells were significantly enriched among the CD34−/lo HSCs (Wilson et al., 2008) (Fig.”

“…uthor M anuscript A uthor M anuscript The BM of adult mammals maintains a rare population of hematopoietic stem cells (HSCs) that can permanently reconstitute blood formation when transferred into lethally irradiated or otherwise myelosuppressed hosts (Eaves, 2015; Shizuru et al., 2005).”

“Several genetic markers were recently developed to identify HSC subsets with a particular lineage bias (Vwf, (Sanjuan-Pla et al., 2013)) or a superior reconstitution capacity (Hoxb5, (Chen et al., 2016)) during primary transplantations.”

“As in the case of Pdzk1ip1-GFP+ cells, the labeled Tom+ cells were significantly enriched among the CD34−/lo HSCs (Wilson et al., 2008) (Fig.”

“Though the function of Pdzk1ip1 is not well studied, the gene, unlike in mice, is not expressed in human HSCs (Bagger et al., 2016), and consequently it is unlikely to have a major role in HSC function.”

“We treated tamoxifen-induced mice with the double-stranded RNA polymer poly-I:C, an inducer of type I IFN that increases HSC proliferation (Essers et al., 2009; Pietras et al., 2014).”

“However, these phenotypically defined HSCs are heterogeneous in their differentiation potential and self-renewal capacity, as revealed by single-cell transplantation (Benz et al., 2012; Challen et al., 2010; Dykstra et al., 2007; Morita et al., 2010) and genetic reporters (Chen et al.”

“As in the case of Pdzk1ip1-GFP+ cells, the labeled Tom+ cells were significantly enriched among the CD34−/lo HSCs (Wilson et al., 2008) (Fig.”

“These results further suggest that tissue MF represent a spectrum showing different degrees of self-renewal versus hematopoietic contribution (Gentek et al., 2014).”

“Continuous blood development (hematopoiesis) is particularly important for the immune system, in which myeloid cells such as granulocytes, monocytes, and dendritic cells (DCs) are very short lived (Geering et al., 2013; Geissmann et al., 2010).”

“Our data are consistent with the recent clonal analysis in humans following hematopoietic reconsititution, revealing a major sustained contribution of multipotent HSCs over many years (Biasco et al., 2016).”

“The full-length BAC clone recapitulated the expression of endogenous Pdzk1ip1 and targeted transgene expression to all HSCs and to some progenitors, similar to several other HSC-specific genes (Gazit et al., 2014; Kataoka et al., 2011).”

“The full-length BAC clone recapitulated the expression of endogenous Pdzk1ip1 and targeted transgene expression to all HSCs and to some progenitors, similar to several other HSC-specific genes (Gazit et al., 2014; Kataoka et al., 2011).”

“They also help explain the essential biology of HSCs, such as their active role in the aging of hematopoietic system (Adams et al., 2015) and the frequent origin of leukemogenic mutations in the HSC pool (Elias et al.”

“Pdzk1ip1 (also known as Map17) is expressed in the murine HSC population but is strongly reduced in more differentiated cells or in mobilized HSCs (Cabezas-Wallscheid et al., 2014; Forsberg et al., 2010; Wilson et al., 2015).”

“, 2015) and the frequent origin of leukemogenic mutations in the HSC pool (Elias et al., 2014).”

“In adult life, in many murine tissues the resident population of mononuclear phagocytes is a mix of cells originating during development and circulating monocytic precursors (2; 14), as illustrated by heart macrophages (15).”

“Furthermore, 89Sr-induced monocytopenia in animals did not affect normal tissue-resident macrophage compartments and macrophage cell numbers (Naito and Takahashi, 1991; Oghiso et al., 1988; Sawyer et al., 1982; Yamada et al., 1990).”