Intimomedial tears of the aorta heal by smooth muscle cell–mediated fibrosis without atherosclerosis
Abdulrahman H.M. Hassab, … , George Tellides, Roland Assi
Abdulrahman H.M. Hassab, … , George Tellides, Roland Assi
Published April 9, 2024
Citation Information: JCI Insight. 2024;9(9):e172437. https://doi.org/10.1172/jci.insight.172437.
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Clinical Research and Public Health Vascular biology

Intimomedial tears of the aorta heal by smooth muscle cell–mediated fibrosis without atherosclerosis

Abstract

BACKGROUND Disease of the aorta varies from atherosclerosis to aneurysms, with complications including rupture, dissection, and poorly characterized limited tears. We studied limited tears without any mural hematoma, termed intimomedial tears, to gain insight into aortic vulnerability to excessive wall stresses. Our premise is that minimal injuries in aortas with sufficient medial resilience to prevent tear progression correspond to initial mechanisms leading to complete structural failure in aortas with significantly compromised medial resilience.METHODS Intimomedial tears were macroscopically identified in 9 of 108 ascending aortas after surgery and analyzed by histology and immunofluorescence confocal microscopy.RESULTS Nonhemorrhagic, nonatheromatous tears correlated with advanced aneurysmal disease and most lacked distinctive symptoms or radiological signs. Tears traversed the intima and part of the subjacent media, while the resultant defects were partially or completely filled with neointima characterized by differentiated smooth muscle cells, scattered leukocytes, dense fibrosis, and absent elastic laminae despite tropoelastin synthesis. Healed lesions contained organized fibrin at tear edges without evidence of plasma and erythrocyte extravasation or lipid accumulation.CONCLUSION These findings suggest a multiphasic model of aortic wall failure in which primary lesions of intimomedial tears either heal if the media is sufficiently resilient or progress as dissection or rupture by medial delamination and tear completion, respectively. Moreover, mural incorporation of thrombus and cellular responses to injury, two historically important concepts in atheroma pathogenesis, contribute to vessel wall repair with adequate conduit function, but even together are not sufficient to induce atherosclerosis.FUNDING NIH (R01-HL146723, R01-HL168473) and Yale Department of Surgery.

Authors

Abdulrahman H.M. Hassab, David J. Hur, Prashanth Vallabhajosyula, George Tellides, Roland Assi

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Figure 8

Multiphasic model of aortic wall failure.

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Multiphasic model of aortic wall failure. Mismatch between wall stress a...
Mismatch between wall stress and wall strength may lead to tears of the aorta involving the intima and part of the subjacent media (intimomedial tear). The lesions may heal without complication (healed intimomedial tear) or extend, suddenly or gradually, by separating the layers of the media in axial and circumferential planes as dissection or completion of tears through the media in a radial direction as rupture. Medial delamination may uncommonly be circumscribed (focal dissection) or typically extensive (classic dissection, or simply dissection). Bleeding through transmedial tears may be restricted by adventitia and fibrotic perivascular tissue (contained rupture) or result in exsanguination through transmural extension (free rupture). Each phase of wall failure (labeled 1–9) likely requires distinct biomechanical forces or cellular and ECM vulnerabilities, implying multiple mechanisms and therapeutic targets. Thus, a continuum of aortic injury is created by varying combinations of defects.