Effect of short‐term organoid culture on the pharmaco‐mechanical properties of rat extra‐ and intrapulmonary arteries

Organoid cultured explants from differentiated tissues have gained renewed interest in the undertaking of physiological and pharmacological studies. In the work herein, we examined the pharmaco‐mechanical properties of an in vitro model consisting of organoid cultured rings derived from rat extra‐ and intrapulmonary arteries, over a period of 4 days in culture. Mechanical changes were quantified using isometric tension measurements on both fresh and cultured pulmonary arterial tissues, with experiments performed in the presence or absence of 10% foetal calf serum. Conventional histochemical and immunofluorescent stainings were also performed to assess tissue structure integrity and apoptosis. The explants developed spontaneous rhythmic contractions (SRC) in approximately half of the vessels. SRC amplitude and time course were modified by conditions and agents acting on membrane potential (high‐potassium solutions – levcromakalim, a potassium channel opener), while nitrendipine, an L‐type calcium channel blocker, suppressed SRC. Cultured explants also developed a hyper‐reactivity to high potassium challenges (10–40 m M ). Whereas contraction to serotonin (5‐HT) was enhanced in intrapulmonary arteries, contraction to endothelin‐1 remained unchanged after 4 days of culture. Serum did not alter contractile properties during the culture period. Endothelial‐dependent relaxation was maintained in response to A23187 500  μ M , but was abolished in response to 10  μ M carbamylcholine. Histological and immuno‐histological analyses revealed the absence of hypertrophied vascular wall or apoptosis. In conclusion, the contractile phenotype as well as tissue structure integrity of organoid explants remain essentially intact during short‐term culture, making this model suitable for pharmaco‐genomic studies.British Journal of Pharmacology (2005) 146 , 692–701. doi: 10.1038/sj.bjp.0706379