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A transmigratory cup in leukocyte diapedesis both through individual vascular endothelial cells and between them.

Carman CV, Springer TA - J. Cell Biol. (2004)

Bottom Line: We provide definitive evidence for transcellular (i.e., through individual endothelial cells) diapedesis in vitro and demonstrate that virtually all, both para- and transcellular, diapedesis occurs in the context of a novel "cuplike" transmigratory structure.Disruption of projections was highly correlated with inhibition of transmigration.These findings suggest a novel mechanism, the "transmigratory cup", by which the endothelium provides directional guidance to leukocytes for extravasation.

View Article: PubMed Central - PubMed

Affiliation: The CBR Institute for Biomedical Research, Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.

ABSTRACT
The basic route and mechanisms for leukocyte migration across the endothelium remain poorly defined. We provide definitive evidence for transcellular (i.e., through individual endothelial cells) diapedesis in vitro and demonstrate that virtually all, both para- and transcellular, diapedesis occurs in the context of a novel "cuplike" transmigratory structure. This endothelial structure was comprised of highly intercellular adhesion molecule-1- and vascular cell adhesion molecule-1-enriched vertical microvilli-like projections that surrounded transmigrating leukocytes and drove redistribution of their integrins into linear tracks oriented parallel to the direction of diapedesis. Disruption of projections was highly correlated with inhibition of transmigration. These findings suggest a novel mechanism, the "transmigratory cup", by which the endothelium provides directional guidance to leukocytes for extravasation.

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ICAM-1 and VCAM-1, but not VE-cadherin, are highly enriched in projections surrounding sites of transmigration. (A) Top view of 0.2-μm-thick confocal sections of a monocyte in TEM-1 at 0 μm (top) and 3 μm (bottom) above the apical surface of the endothelium. ICAM-1 (IC1, green), VCAM-1 (VC1, red), and β2 integrin (β2, blue) are shown either separately (left three) or merged (right). (B) Top view of confocal sections of a monocyte in TEM-1 at 0 μm (top) and 3 μm (bottom) above the apical endothelial surface. ICAM-1 (IC1, green), VE-cadherin (VE-CAD, red), and β2 integrin (β2, blue) are shown either separately (left three) or merged (right). Note that VE-cadherin staining at 0 μm is continuous at the TEM passage in contrast to Fig. S4 C. (C) Serial confocal sections of a monocyte in TEM-2 projected as top (0o, top) or side (90°, bottom) views. ICAM-1 (IC1, green), VCAM-1 (VC1, red), and β2 integrins (β2, blue) are shown either separately (left three) or merged (right). Three-dimensional rotation of these projections is shown in Video 1. (D) Serial confocal sections of a lymphocyte in TEM-2 projected as top (0o, left) or side (90°, right three) views. α4 integrin (α4, green) and VCAM-1 (VC1, red) are shown either separately (middle) or merged (left and right). Bars, 5 μm.
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fig6: ICAM-1 and VCAM-1, but not VE-cadherin, are highly enriched in projections surrounding sites of transmigration. (A) Top view of 0.2-μm-thick confocal sections of a monocyte in TEM-1 at 0 μm (top) and 3 μm (bottom) above the apical surface of the endothelium. ICAM-1 (IC1, green), VCAM-1 (VC1, red), and β2 integrin (β2, blue) are shown either separately (left three) or merged (right). (B) Top view of confocal sections of a monocyte in TEM-1 at 0 μm (top) and 3 μm (bottom) above the apical endothelial surface. ICAM-1 (IC1, green), VE-cadherin (VE-CAD, red), and β2 integrin (β2, blue) are shown either separately (left three) or merged (right). Note that VE-cadherin staining at 0 μm is continuous at the TEM passage in contrast to Fig. S4 C. (C) Serial confocal sections of a monocyte in TEM-2 projected as top (0o, top) or side (90°, bottom) views. ICAM-1 (IC1, green), VCAM-1 (VC1, red), and β2 integrins (β2, blue) are shown either separately (left three) or merged (right). Three-dimensional rotation of these projections is shown in Video 1. (D) Serial confocal sections of a lymphocyte in TEM-2 projected as top (0o, left) or side (90°, right three) views. α4 integrin (α4, green) and VCAM-1 (VC1, red) are shown either separately (middle) or merged (left and right). Bars, 5 μm.

Mentions: Close investigation of leukocyte β2 integrin, the common subunit of the ICAM-1 receptors LFA-1 and Mac-1, revealed regions of increased density that formed linear clusters oriented parallel to the direction of diapedesis, which colocalized with the ICAM-1 projections (Fig. 1 E; Fig. 2 E; and Fig. 6 C, bottom). Separate analysis of αL and αM subunits revealed similar results (unpublished data). As demonstrated previously (Carman et al., 2003), leukocytes not associated with projections failed to exhibit linear integrin clusters (unpublished data).


A transmigratory cup in leukocyte diapedesis both through individual vascular endothelial cells and between them.

Carman CV, Springer TA - J. Cell Biol. (2004)

ICAM-1 and VCAM-1, but not VE-cadherin, are highly enriched in projections surrounding sites of transmigration. (A) Top view of 0.2-μm-thick confocal sections of a monocyte in TEM-1 at 0 μm (top) and 3 μm (bottom) above the apical surface of the endothelium. ICAM-1 (IC1, green), VCAM-1 (VC1, red), and β2 integrin (β2, blue) are shown either separately (left three) or merged (right). (B) Top view of confocal sections of a monocyte in TEM-1 at 0 μm (top) and 3 μm (bottom) above the apical endothelial surface. ICAM-1 (IC1, green), VE-cadherin (VE-CAD, red), and β2 integrin (β2, blue) are shown either separately (left three) or merged (right). Note that VE-cadherin staining at 0 μm is continuous at the TEM passage in contrast to Fig. S4 C. (C) Serial confocal sections of a monocyte in TEM-2 projected as top (0o, top) or side (90°, bottom) views. ICAM-1 (IC1, green), VCAM-1 (VC1, red), and β2 integrins (β2, blue) are shown either separately (left three) or merged (right). Three-dimensional rotation of these projections is shown in Video 1. (D) Serial confocal sections of a lymphocyte in TEM-2 projected as top (0o, left) or side (90°, right three) views. α4 integrin (α4, green) and VCAM-1 (VC1, red) are shown either separately (middle) or merged (left and right). Bars, 5 μm.
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fig6: ICAM-1 and VCAM-1, but not VE-cadherin, are highly enriched in projections surrounding sites of transmigration. (A) Top view of 0.2-μm-thick confocal sections of a monocyte in TEM-1 at 0 μm (top) and 3 μm (bottom) above the apical surface of the endothelium. ICAM-1 (IC1, green), VCAM-1 (VC1, red), and β2 integrin (β2, blue) are shown either separately (left three) or merged (right). (B) Top view of confocal sections of a monocyte in TEM-1 at 0 μm (top) and 3 μm (bottom) above the apical endothelial surface. ICAM-1 (IC1, green), VE-cadherin (VE-CAD, red), and β2 integrin (β2, blue) are shown either separately (left three) or merged (right). Note that VE-cadherin staining at 0 μm is continuous at the TEM passage in contrast to Fig. S4 C. (C) Serial confocal sections of a monocyte in TEM-2 projected as top (0o, top) or side (90°, bottom) views. ICAM-1 (IC1, green), VCAM-1 (VC1, red), and β2 integrins (β2, blue) are shown either separately (left three) or merged (right). Three-dimensional rotation of these projections is shown in Video 1. (D) Serial confocal sections of a lymphocyte in TEM-2 projected as top (0o, left) or side (90°, right three) views. α4 integrin (α4, green) and VCAM-1 (VC1, red) are shown either separately (middle) or merged (left and right). Bars, 5 μm.
Mentions: Close investigation of leukocyte β2 integrin, the common subunit of the ICAM-1 receptors LFA-1 and Mac-1, revealed regions of increased density that formed linear clusters oriented parallel to the direction of diapedesis, which colocalized with the ICAM-1 projections (Fig. 1 E; Fig. 2 E; and Fig. 6 C, bottom). Separate analysis of αL and αM subunits revealed similar results (unpublished data). As demonstrated previously (Carman et al., 2003), leukocytes not associated with projections failed to exhibit linear integrin clusters (unpublished data).

Bottom Line: We provide definitive evidence for transcellular (i.e., through individual endothelial cells) diapedesis in vitro and demonstrate that virtually all, both para- and transcellular, diapedesis occurs in the context of a novel "cuplike" transmigratory structure.Disruption of projections was highly correlated with inhibition of transmigration.These findings suggest a novel mechanism, the "transmigratory cup", by which the endothelium provides directional guidance to leukocytes for extravasation.

View Article: PubMed Central - PubMed

Affiliation: The CBR Institute for Biomedical Research, Department of Pathology, Harvard Medical School, Boston, MA 02115, USA.

ABSTRACT
The basic route and mechanisms for leukocyte migration across the endothelium remain poorly defined. We provide definitive evidence for transcellular (i.e., through individual endothelial cells) diapedesis in vitro and demonstrate that virtually all, both para- and transcellular, diapedesis occurs in the context of a novel "cuplike" transmigratory structure. This endothelial structure was comprised of highly intercellular adhesion molecule-1- and vascular cell adhesion molecule-1-enriched vertical microvilli-like projections that surrounded transmigrating leukocytes and drove redistribution of their integrins into linear tracks oriented parallel to the direction of diapedesis. Disruption of projections was highly correlated with inhibition of transmigration. These findings suggest a novel mechanism, the "transmigratory cup", by which the endothelium provides directional guidance to leukocytes for extravasation.

Show MeSH
Related in: MedlinePlus