Limits...
Characterization of Proliferating Lesion ‐ Resident Cells During All Stages of Atherosclerotic Growth

View Article: PubMed Central - PubMed

ABSTRACT

Background: Monocyte recruitment leads to accumulation of macrophage foam cells and contributes to atherosclerotic lesion growth. Recent studies have reported that lesion‐resident macrophages can proliferate and represent a major cellular component during lesion development. This study was designed to assess whether the rate of macrophage proliferation changes during well‐established stages of lesion growth and to characterize other populations of proliferating cells within these lesions.

Methods and results: Using murine models of atherosclerosis (Apoe−/− and LDLr−/− mice) and human coronary artery lesions, in situ proliferation of lesion‐resident cells at different stages of growth was assessed by staining for Ki67 and bromodeoxyuridine (BrdU). In early lesions, close to half of all actively growing macrophages were proliferating in situ. BrdU pulse labeling allowed for accurate identification of in situ proliferating macrophages compared to those derived from monocyte recruitment. Local macrophage proliferation declined as lesions advanced. Interestingly, intimal inflammatory cell infiltrates containing proliferating T lymphocytes were identified during the active phase of lesion growth and correlated with apoptotic cell death. Inflammatory cell infiltrates were completely resolved in advanced lesions and replaced with the necrotic core.

Conclusions: Our findings indicate that atherosclerotic lesions contain locally proliferating macrophages primarily during early and intermediate stages of lesion growth. Furthermore, T‐lymphocyte‐enriched inflammatory cell infiltrates represent a novel subset of proliferating cells within the atherosclerotic lesion that correlate with apoptosis and precede the necrotic core. These findings have novel implications in understanding the pathogenesis of atherosclerosis and may implicate proliferating T lymphocytes as a contributing factor to lesion progression and stability.

No MeSH data available.


T‐cell recruitment into inflammatory cell infiltrates. Double immunofluorescence for CD3 (green) and BrdU (red). Two hours post‐BrdU injection, CD3‐positive lymphocytes in the intimal inflammatory cell infiltrate (ICI) were BrdU negative (A). BrdU‐positive nuclei were present in the adventitial ICI, some in T lymphocytes (arrow, A), and others in macrophages (arrowhead, A). At 24 hours p.i., some of the single‐file T lymphocytes lining the endothelium were BrdU positive (arrow, inset, B). Few CD3‐positive cells were observed in the media; 1 was BrdU positive (arrow, inset, B). L, lumen; M, media; A, adventitia. Bar=100 μm. BrdU indicates bromodeoxyuridine; p.i., postinjection.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5015311&req=5

jah31705-fig-0006: T‐cell recruitment into inflammatory cell infiltrates. Double immunofluorescence for CD3 (green) and BrdU (red). Two hours post‐BrdU injection, CD3‐positive lymphocytes in the intimal inflammatory cell infiltrate (ICI) were BrdU negative (A). BrdU‐positive nuclei were present in the adventitial ICI, some in T lymphocytes (arrow, A), and others in macrophages (arrowhead, A). At 24 hours p.i., some of the single‐file T lymphocytes lining the endothelium were BrdU positive (arrow, inset, B). Few CD3‐positive cells were observed in the media; 1 was BrdU positive (arrow, inset, B). L, lumen; M, media; A, adventitia. Bar=100 μm. BrdU indicates bromodeoxyuridine; p.i., postinjection.

Mentions: BrdU pulse‐labeling and CD3 immunostaining was used to assess T‐lymphocyte recruitment into the ICIs. At 2 hours post‐BrdU pulse, CD3‐positive T lymphocytes in the intimal ICI lacked BrdU staining (Figure 6A), implying that the majority of these cells were derived from the circulation. Unlike the intima, BrdU‐positive T lymphocytes were observed in the underlying adventitial ICIs (Figure 6A, arrow). Other BrdU‐positive cells contained large nuclei and were negative for CD3 (Figure 6A, arrowhead). This suggests that T lymphocytes in intimal ICIs do not proliferate in situ, whereas some T lymphocytes in adventitial ICIs do. At 24 hours p.i., BrdU/CD3‐positive T lymphocytes were identified in the intima (Figure 6B, inset, arrow). The location of the BrdU/CD3‐positive cells that lie in a single‐file pattern along the intimal side of endothelium is suggestive of their recruitment from the aorta. A few BrdU/CD3‐positive cells were also observed in the media, suggesting that some of the proliferating T lymphocytes may cross the medial layer, most likely from the adventitia, into the internal part of the lesion (Figure 6B, lower inset, arrow). Overall, these data suggest that T lymphocytes proliferate locally in the adventitial space, whereas intimal ICI resident T lymphocytes accumulate from both the circulation and the adventitia before their active growth cycle.


Characterization of Proliferating Lesion ‐ Resident Cells During All Stages of Atherosclerotic Growth
T‐cell recruitment into inflammatory cell infiltrates. Double immunofluorescence for CD3 (green) and BrdU (red). Two hours post‐BrdU injection, CD3‐positive lymphocytes in the intimal inflammatory cell infiltrate (ICI) were BrdU negative (A). BrdU‐positive nuclei were present in the adventitial ICI, some in T lymphocytes (arrow, A), and others in macrophages (arrowhead, A). At 24 hours p.i., some of the single‐file T lymphocytes lining the endothelium were BrdU positive (arrow, inset, B). Few CD3‐positive cells were observed in the media; 1 was BrdU positive (arrow, inset, B). L, lumen; M, media; A, adventitia. Bar=100 μm. BrdU indicates bromodeoxyuridine; p.i., postinjection.
© Copyright Policy - creativeCommonsBy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015311&req=5

jah31705-fig-0006: T‐cell recruitment into inflammatory cell infiltrates. Double immunofluorescence for CD3 (green) and BrdU (red). Two hours post‐BrdU injection, CD3‐positive lymphocytes in the intimal inflammatory cell infiltrate (ICI) were BrdU negative (A). BrdU‐positive nuclei were present in the adventitial ICI, some in T lymphocytes (arrow, A), and others in macrophages (arrowhead, A). At 24 hours p.i., some of the single‐file T lymphocytes lining the endothelium were BrdU positive (arrow, inset, B). Few CD3‐positive cells were observed in the media; 1 was BrdU positive (arrow, inset, B). L, lumen; M, media; A, adventitia. Bar=100 μm. BrdU indicates bromodeoxyuridine; p.i., postinjection.
Mentions: BrdU pulse‐labeling and CD3 immunostaining was used to assess T‐lymphocyte recruitment into the ICIs. At 2 hours post‐BrdU pulse, CD3‐positive T lymphocytes in the intimal ICI lacked BrdU staining (Figure 6A), implying that the majority of these cells were derived from the circulation. Unlike the intima, BrdU‐positive T lymphocytes were observed in the underlying adventitial ICIs (Figure 6A, arrow). Other BrdU‐positive cells contained large nuclei and were negative for CD3 (Figure 6A, arrowhead). This suggests that T lymphocytes in intimal ICIs do not proliferate in situ, whereas some T lymphocytes in adventitial ICIs do. At 24 hours p.i., BrdU/CD3‐positive T lymphocytes were identified in the intima (Figure 6B, inset, arrow). The location of the BrdU/CD3‐positive cells that lie in a single‐file pattern along the intimal side of endothelium is suggestive of their recruitment from the aorta. A few BrdU/CD3‐positive cells were also observed in the media, suggesting that some of the proliferating T lymphocytes may cross the medial layer, most likely from the adventitia, into the internal part of the lesion (Figure 6B, lower inset, arrow). Overall, these data suggest that T lymphocytes proliferate locally in the adventitial space, whereas intimal ICI resident T lymphocytes accumulate from both the circulation and the adventitia before their active growth cycle.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Monocyte recruitment leads to accumulation of macrophage foam cells and contributes to atherosclerotic lesion growth. Recent studies have reported that lesion‐resident macrophages can proliferate and represent a major cellular component during lesion development. This study was designed to assess whether the rate of macrophage proliferation changes during well‐established stages of lesion growth and to characterize other populations of proliferating cells within these lesions.

Methods and results: Using murine models of atherosclerosis (Apoe−/− and LDLr−/− mice) and human coronary artery lesions, in situ proliferation of lesion‐resident cells at different stages of growth was assessed by staining for Ki67 and bromodeoxyuridine (BrdU). In early lesions, close to half of all actively growing macrophages were proliferating in situ. BrdU pulse labeling allowed for accurate identification of in situ proliferating macrophages compared to those derived from monocyte recruitment. Local macrophage proliferation declined as lesions advanced. Interestingly, intimal inflammatory cell infiltrates containing proliferating T lymphocytes were identified during the active phase of lesion growth and correlated with apoptotic cell death. Inflammatory cell infiltrates were completely resolved in advanced lesions and replaced with the necrotic core.

Conclusions: Our findings indicate that atherosclerotic lesions contain locally proliferating macrophages primarily during early and intermediate stages of lesion growth. Furthermore, T‐lymphocyte‐enriched inflammatory cell infiltrates represent a novel subset of proliferating cells within the atherosclerotic lesion that correlate with apoptosis and precede the necrotic core. These findings have novel implications in understanding the pathogenesis of atherosclerosis and may implicate proliferating T lymphocytes as a contributing factor to lesion progression and stability.

No MeSH data available.