Mesenchymal stem cell-derived conditioned medium protects vascular grafts of brain-dead rats against in vitro ischemia/reperfusion injury.

Background: Brain death (BD) has been suggested to induce coronary endothelial dysfunction. Ischemia/reperfusion (IR) injury during heart transplantation may lead to further damage of the endothelium. Previous studies have shown protective effects of conditioned medium (CM) from bone marrow-derived mesenchymal stem cells (MSCs) against IR injury. We hypothesized that physiological saline-supplemented CM protects BD rats' vascular grafts from IR injury.

Methods: The CM from rat MSCs, used for conservation purposes, indicates the presence of 23 factors involved in apoptosis, inflammation, and oxidative stress. BD was induced by an intracranial-balloon. Controls were subjected to a sham operation. After 5.5 h, arterial pressures were measured in vivo. Aortic rings from BD rats were harvested and immediately mounted in organ bath chambers (BD group, n = 7) or preserved for 24 h in 4 °C saline-supplemented either with a vehicle (BD-IR group, n = 8) or CM (BD-IR+CM group, n = 8), prior to mounting. Vascular function was measured in vitro. Furthermore, immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR) have been performed.

Results: BD in donors was associated with significantly impaired hemodynamic parameters and higher immunoreactivity of aortic myeloperoxidase (MPO), nitrotyrosine, caspase-3, caspase-8, caspase-9, and caspase-12 compared to sham-operated rats. In organ bath experiments, impaired endothelium-dependent vasorelaxation to acetylcholine in the BD-IR group compared to BD rats was significantly improved by CM (maximum relaxation to acetylcholine: BD 81 ± 2% vs. BD-IR 50 ± 3% vs. BD-IR + CM 72 ± 2%, p < 0.05). Additionally, the preservation of BD-IR aortic rings with CM significantly lowered MPO, caspase-3, caspase-8, and caspase-9 immunoreactivity compared with the BD-IR group. Furthermore, increased mRNA expression of vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1 in the aortas from the BD-IR rats compared to BD group were significantly decreased by CM.

Conclusions: The preservation of BD rats' vascular grafts with CM alleviates endothelial dysfunction following IR injury, in part, by reducing levels of inflammatory response and caspase-mediated apoptosis.