Limits...
Macrophages retain hematopoietic stem cells in the spleen via VCAM-1.

Dutta P, Hoyer FF, Grigoryeva LS, Sager HB, Leuschner F, Courties G, Borodovsky A, Novobrantseva T, Ruda VM, Fitzgerald K, Iwamoto Y, Wojtkiewicz G, Sun Y, Da Silva N, Libby P, Anderson DG, Swirski FK, Weissleder R, Nahrendorf M - J. Exp. Med. (2015)

Bottom Line: Yet regulation of hematopoietic stem cell (HSC) activity in the spleen is incompletely understood.Nanoparticle-enabled in vivo RNAi silencing of the receptor for macrophage colony stimulation factor (M-CSFR) blocked splenic macrophage maturation, reduced splenic VCAM-1 expression and compromised splenic HSC retention.When we silenced either VCAM-1 or M-CSFR in mice with myocardial infarction or in ApoE(-/-) mice with atherosclerosis, nanoparticle-enabled in vivo RNAi mitigated blood leukocytosis, limited inflammation in the ischemic heart, and reduced myeloid cell numbers in atherosclerotic plaques.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Systems Biology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 mnahrendorf@mgh.harvard.edu dutta.partha@mgh.harvard.edu.

Show MeSH

Related in: MedlinePlus

Splenic HSPCs reside near VCAM-1+ macrophages. (A) Gating for endothelial cells. CD45.2− CD31high ICAM-2high cells were considered as endothelial cells. (B) VCAM-1 expression on splenic endothelial cell and leukocytes by FACS. (C) Cluster of GFP+ cells in the splenic red pulp 3 d after GFP+ HSPC transfer into wild-type mouse. Bar, 15 µm. (D) Cluster of GFP+ cells (green) near VCAM-1+ macrophages (red). Bar, 20 µm. (E) GFP+ cells (green) in close contact with VCAM-1+ (red) macrophages (F4/80+, blue) in the spleen. Bar, 5 µm. (F) 3D image of interaction between a GFP+ cell and a VCAM-1+ macrophage. (G) Fraction of GFP+ cells within indicated distance from VCAM-1+ macrophages (n = 5). (H) We induced parabiosis of GFP+ and GFP− mice. After 6 wk of parabiosis, the spleens of GFP− wild-type mice were analyzed for chimerism (GFP+ cells) using flow cytometry (H) and immunofluorescence microscopy (I; n = 3). Bar, 10 µm. Data were pooled from two independent experiments. Data are mean ± SEM. Significance was determined by one-way ANOVA and Mann-Whitney test. *, P < 0.05; ***, P < 0.01.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4387283&req=5

fig5: Splenic HSPCs reside near VCAM-1+ macrophages. (A) Gating for endothelial cells. CD45.2− CD31high ICAM-2high cells were considered as endothelial cells. (B) VCAM-1 expression on splenic endothelial cell and leukocytes by FACS. (C) Cluster of GFP+ cells in the splenic red pulp 3 d after GFP+ HSPC transfer into wild-type mouse. Bar, 15 µm. (D) Cluster of GFP+ cells (green) near VCAM-1+ macrophages (red). Bar, 20 µm. (E) GFP+ cells (green) in close contact with VCAM-1+ (red) macrophages (F4/80+, blue) in the spleen. Bar, 5 µm. (F) 3D image of interaction between a GFP+ cell and a VCAM-1+ macrophage. (G) Fraction of GFP+ cells within indicated distance from VCAM-1+ macrophages (n = 5). (H) We induced parabiosis of GFP+ and GFP− mice. After 6 wk of parabiosis, the spleens of GFP− wild-type mice were analyzed for chimerism (GFP+ cells) using flow cytometry (H) and immunofluorescence microscopy (I; n = 3). Bar, 10 µm. Data were pooled from two independent experiments. Data are mean ± SEM. Significance was determined by one-way ANOVA and Mann-Whitney test. *, P < 0.05; ***, P < 0.01.

Mentions: Because VCAM-1 was the only retention factor that changed in the spleen after M-CSFR knockdown (Fig. 3 D), we investigated which splenocytes express VCAM-1. We found that splenic macrophages (Ulyanova et al., 2005) and endothelial cells express VCAM-1 at high levels (Fig. 5, A and B). We next tested whether splenic HSCs reside close to VCAM-1–expressing cells. Toward this end, we transferred GFP+ HSPCs (LSKs) into LPS-primed mice and imaged splenic sections 3 d later. Transferred GFP+ progenitors localized in numerous splenic locations and formed colonies in the red pulp, indicating their proliferation (Fig. 5 C). GFP+ colonies localized near VCAM-1+ macrophages (Fig. 5 D). Numerous GFP+ cells closely contacted VCAM-1–expressing macrophages in the splenic red pulp (Fig. 5, E and F; and Video 1). Indeed, 44.4 ± 3.7% of GFP+ cells lay in direct contact with or <1 µm distant from VCAM-1+ macrophages (Fig. 5 G). Another 49.4 ± 3.1% of the HSPCs resided within 1–10 µm of VCAM-1+ macrophages.


Macrophages retain hematopoietic stem cells in the spleen via VCAM-1.

Dutta P, Hoyer FF, Grigoryeva LS, Sager HB, Leuschner F, Courties G, Borodovsky A, Novobrantseva T, Ruda VM, Fitzgerald K, Iwamoto Y, Wojtkiewicz G, Sun Y, Da Silva N, Libby P, Anderson DG, Swirski FK, Weissleder R, Nahrendorf M - J. Exp. Med. (2015)

Splenic HSPCs reside near VCAM-1+ macrophages. (A) Gating for endothelial cells. CD45.2− CD31high ICAM-2high cells were considered as endothelial cells. (B) VCAM-1 expression on splenic endothelial cell and leukocytes by FACS. (C) Cluster of GFP+ cells in the splenic red pulp 3 d after GFP+ HSPC transfer into wild-type mouse. Bar, 15 µm. (D) Cluster of GFP+ cells (green) near VCAM-1+ macrophages (red). Bar, 20 µm. (E) GFP+ cells (green) in close contact with VCAM-1+ (red) macrophages (F4/80+, blue) in the spleen. Bar, 5 µm. (F) 3D image of interaction between a GFP+ cell and a VCAM-1+ macrophage. (G) Fraction of GFP+ cells within indicated distance from VCAM-1+ macrophages (n = 5). (H) We induced parabiosis of GFP+ and GFP− mice. After 6 wk of parabiosis, the spleens of GFP− wild-type mice were analyzed for chimerism (GFP+ cells) using flow cytometry (H) and immunofluorescence microscopy (I; n = 3). Bar, 10 µm. Data were pooled from two independent experiments. Data are mean ± SEM. Significance was determined by one-way ANOVA and Mann-Whitney test. *, P < 0.05; ***, P < 0.01.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4387283&req=5

fig5: Splenic HSPCs reside near VCAM-1+ macrophages. (A) Gating for endothelial cells. CD45.2− CD31high ICAM-2high cells were considered as endothelial cells. (B) VCAM-1 expression on splenic endothelial cell and leukocytes by FACS. (C) Cluster of GFP+ cells in the splenic red pulp 3 d after GFP+ HSPC transfer into wild-type mouse. Bar, 15 µm. (D) Cluster of GFP+ cells (green) near VCAM-1+ macrophages (red). Bar, 20 µm. (E) GFP+ cells (green) in close contact with VCAM-1+ (red) macrophages (F4/80+, blue) in the spleen. Bar, 5 µm. (F) 3D image of interaction between a GFP+ cell and a VCAM-1+ macrophage. (G) Fraction of GFP+ cells within indicated distance from VCAM-1+ macrophages (n = 5). (H) We induced parabiosis of GFP+ and GFP− mice. After 6 wk of parabiosis, the spleens of GFP− wild-type mice were analyzed for chimerism (GFP+ cells) using flow cytometry (H) and immunofluorescence microscopy (I; n = 3). Bar, 10 µm. Data were pooled from two independent experiments. Data are mean ± SEM. Significance was determined by one-way ANOVA and Mann-Whitney test. *, P < 0.05; ***, P < 0.01.
Mentions: Because VCAM-1 was the only retention factor that changed in the spleen after M-CSFR knockdown (Fig. 3 D), we investigated which splenocytes express VCAM-1. We found that splenic macrophages (Ulyanova et al., 2005) and endothelial cells express VCAM-1 at high levels (Fig. 5, A and B). We next tested whether splenic HSCs reside close to VCAM-1–expressing cells. Toward this end, we transferred GFP+ HSPCs (LSKs) into LPS-primed mice and imaged splenic sections 3 d later. Transferred GFP+ progenitors localized in numerous splenic locations and formed colonies in the red pulp, indicating their proliferation (Fig. 5 C). GFP+ colonies localized near VCAM-1+ macrophages (Fig. 5 D). Numerous GFP+ cells closely contacted VCAM-1–expressing macrophages in the splenic red pulp (Fig. 5, E and F; and Video 1). Indeed, 44.4 ± 3.7% of GFP+ cells lay in direct contact with or <1 µm distant from VCAM-1+ macrophages (Fig. 5 G). Another 49.4 ± 3.1% of the HSPCs resided within 1–10 µm of VCAM-1+ macrophages.

Bottom Line: Yet regulation of hematopoietic stem cell (HSC) activity in the spleen is incompletely understood.Nanoparticle-enabled in vivo RNAi silencing of the receptor for macrophage colony stimulation factor (M-CSFR) blocked splenic macrophage maturation, reduced splenic VCAM-1 expression and compromised splenic HSC retention.When we silenced either VCAM-1 or M-CSFR in mice with myocardial infarction or in ApoE(-/-) mice with atherosclerosis, nanoparticle-enabled in vivo RNAi mitigated blood leukocytosis, limited inflammation in the ischemic heart, and reduced myeloid cell numbers in atherosclerotic plaques.

View Article: PubMed Central - HTML - PubMed

Affiliation: Center for Systems Biology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114 mnahrendorf@mgh.harvard.edu dutta.partha@mgh.harvard.edu.

Show MeSH
Related in: MedlinePlus