IFPA senior award lecture: Energy metabolism of human placental tissue studied by ex vivo perfusion of an isolated cotyledon.

BACKGROUND: This is a historical review of the method of "Ex vivo dual perfusion of a human placental cotyledon", which was first described by M. Panigel in 1967. The subsequent evolution of this method is described with particular emphasis on energy metabolism of human placental tissue under ex vivo conditions.

METHOD: For perfusion of the foetal compartment a pair of a chorionic arterial and venous vessel is cannulated. In the original method a remnant of the spiral artery of that cotyledon was catheterized to provide access to the maternal compartment. To simplify the procedure access to the intervillous space later was achieved by penetration of the decidual plate with 3 to 5 cannulae.

RESULTS: Due to a remarkable tolerance of ischaemia energy dependent transport of amino acids and de novo synthesis of proteins remain functional in spite of a delay of 20 to 30 min. until start of the two ex vivo circuits. With medium containing only physically dissolved oxygen the high demand of oxygen of the tissue can only partially be met. Chronic hypoxia leads to metabolic reprogramming with reduction in mitochondrial oxygen consumption and an increase in anaerobic glycolysis. Addition of erythrocytes to the medium is highly effective in increasing oxygen supply at physiological partial pressure with stimulation of aerobic glycolysis and de novo synthesis of proteins. Increasing the number of maternal cannulae leads to a better distribution of haemoglobin free medium with physiological partial pressure of oxygen giving median values of oxygen content inside the intervillous space close to target values.

CONCLUSION: Ex vivo dual perfusion of a human placental cotyledon allows to study functional aspects of this organ under close to in vivo conditions. A remarkable tolerance of ischaemia permits a start of dual perfusion ex vivo with a delay of 20 to 30 min. after delivery without significant tissue damage.