In heart transplant and lung transplant recipients, nitric oxide and prostacyclin similarly reduce pulmonary artery pressures and central venous pressure, and improve cardiac index and mixed venous oxygen saturation. Inhaled prostacyclin may offer an alternative to nitric oxide in the treatment of pulmonary hypertension in thoracic transplantation.
Prophylactic-inhaled NO does not prevent RI in human lung transplantation. However, inhaled NO, started at reperfusion, improves gas exchange and reduces pulmonary artery pressure in those patients who develop RI.
Objective
Although anoxia/reoxygenation of cultured cells has been employed to model lung ischemia-reperfusion injury (IRI), this does not accurately mimic events experienced by lung cells while a lung is retrieved from a donor, stored, and transplanted. We developed an in vitro model of non-hypoxic IRI to simulate these events.
Methods
Human umbilical vein endothelial cells (HUVECs) underwent simulated cold ischemia by replacing 37°C culture media with 4°C Perfadex™ solution for 5 hours in 100% O2. Culture dishes were allowed to warm to room temperature for 1 hour (implantation), then Perfadex™ was replaced with 37°C culture media (reperfusion).
Results
During cold ischemia, HUVEC filamentous actin cytoskeleton quickly became rearranged, and gaps developed in the previously confluent monolayer occupying 20% of the surface area. Simulated reperfusion resulted in reorganization to a confluent monolayer. Development of gaps was not due to enhanced necrosis based on LDH retention assay. Endothelial cytoskeletal rearrangement could account for early edema due to IRI with reperfusion. MAPK and NF-κB activation occurred with simulated reperfusion despite normoxia. Pro-inflammatory cytokines IL-6 and IL-8 were significantly elevated in media at the end of reperfusion.
Conclusions
Exposing HUVECs to simulated cold ischemia without hypoxia causes reversible cytoskeletal alterations, activation of inflammatory pathways, and elaboration of cytokines. Because this model accurately depicts events occurring during lung transplantation, it will be useful to explore mechanisms regulating lung cell response to this unique form of IRI.
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