Beyond Engraftment: Real-Time Imaging of Mesenchymal Stem Cell-Mediated Vasculoprotection in Cardiac Injury

<jats:p>&lt;b&gt;Background and Purpose:&lt;/b&gt; Ischaemic heart disease drives microvascular obstruction despite epicardial reperfusion. Mesenchymal stem cells (MSCs) emerged to treat this, yet their exact functional mechanisms remain contested. This review synthesises how intravital microscopy reshapes our understanding of MSC-mediated cardiac repair. &lt;b&gt;Experimental Approach:&lt;/b&gt; We analysed recent preclinical investigations utilising multiphoton intravital imaging within murine myocardial ischaemia-reperfusion models. We evaluated real-time cellular tracking, microvascular perfusion mapping, and extracellular vesicle distribution kinetics. &lt;b&gt;Key Results:&lt;/b&gt; Real-time imaging proves long-term cellular engraftment rarely occurs. MSCs operate as transient pharmacological vectors. They immediately release localised extracellular vesicles and paracrine factors upon microvascular arrest. This rapid secretion limits endothelial permeability and blocks neutrophil extravasation. The cardiac microcirculation clears over 80% of administered MSCs within 48 hours. Resident host macrophages subsequently ingest this apoptotic cell debris. This efferocytosis initiates a secondary reparative cascade, reprogramming macrophages to sustain angiogenesis long after the initial MSCs vanish. &lt;b&gt;Conclusion and Implications:&lt;/b&gt; Acute vasculoprotection, rather than permanent cellular replacement, drives MSC efficacy. Clinical administration must shift to target the immediate ischaemic reperfusion window. Merging dynamic optical datasets with machine learning will eventually replace live cells with precision-engineered, cell-free therapeutics.</jats:p>