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Cardiovasc Res. 2019 May 7. pii: cvz118. doi: 10.1093/cvr/cvz118. [Epub ahead of print]

Imaging the injured beating heart intravitally and the vasculoprotection afforded by haematopoietic stem cells.

Author information

1
Institute of Cardiovascular Sciences, College of Medical and Dental Sciences, University of Birmingham, B15 2TT, UK.

Abstract

RATIONALE:

Adequate microcirculatory perfusion, and not just opening of occluded arteries, is critical to salvage heart tissue following myocardial infarction (MI). However, the degree of microvascular perfusion taking place is not known, limited primarily by an inability to directly image coronary microcirculation in a beating heart in vivo. Haematopoietic stem/progenitor cells (HSPCs) offer a potential therapy but little is known about their homing dynamics at a cellular level and whether they protect coronary microvessels. This study used intravital microscopy (IVM) to image the anaesthetised mouse beating heart microcirculation following stabilisation.

METHODS/RESULTS:

A 3D-printed stabiliser was attached to the ischaemia-reperfusion injured (IRI) beating heart. The kinetics of neutrophil, platelet and HSPC recruitment, as well as functional capillary density (FCD), was imaged post-reperfusion. Laser speckle contrast imaging (LSCI) was used for the first time to monitor ventricular blood flow in beating hearts. Sustained hyperaemic responses were measured throughout reperfusion, initially indicating adequate flow resumption. IVM confirmed large vessel perfusion but demonstrated poor transmission of flow to downstream coronary microvessels. Significant neutrophil adhesion and microthrombus formation occurred within capillaries with the latter occluding them, resulting in patchy perfusion and reduced FCD. Interestingly, 'patrolling' neutrophils were also observed in capillaries. HSPCs readily trafficked through the heart but local retention was poor. Despite this, remarkable anti-thromboinflammatory effects were observed, consequently improving microvascular perfusion.

CONCLUSION:

We present a novel approach for imaging multiple microcirculatory perturbations in the beating heart with LSCI assessment of blood flow. Despite deceptive hyperaemic responses, increased microcirculatory flow heterogeneity was seen, with non-perfused areas interspersed with perfused areas. Microthrombi, rather than neutrophils, appeared to be the major causative factor. We further applied this technique to demonstrate local stem cell presence is not a pre-requisite to confer vasculoprotection. This is the first detailed in vivo characterisation of coronary microcirculatory responses post-reperfusion injury.

KEYWORDS:

coronary microcirculation; intravital microscopy; ischaemia-reperfusion injury

PMID:
31062860
DOI:
10.1093/cvr/cvz118

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