Force Generated by Pulmonary Arterial Smooth Muscle Cells: Spatially Distinct Cell Phenotypes from Normal and Hypertensive Arteries

Abstract

Porcine pulmonary arterial smooth muscle cells (smcs) from inner and outer medial layers have distinct structural phenotypes in both normal and hypertensive pulmonary arteries. We hypothesised that force generated by smcs of the inner and outer media would differ and increase in pulmonary hypertension. Smcs were cultured from the inner (I) 25% and outer (O) 75% of the pulmonary artery wall of 4 normal 14 day old piglets (N) and 4 animals exposed to chronic hypobaric hypoxia from 3 to 14 days (H). The cytoskeletal structure of each cell isolate was studied by immunofluorescence. The basal force/time profile and response to U46619 (thromboxane mimetic) and sodium nitroprusside (SNP) were measured using a Culture Force Monitor. Smcs from all 4 sites expressed smooth muscle actin specific actin and myosin isoforms. Hsmc had shorter actin stress fibres and were less well aligned than Nsmc. HOsmcs had more cell substrate adhesions than other isolates. In a 3D collagen matrix all cell types elongated parallel to the axis of strain. Normal Osmcs exerted a greater force then the NIsmcs (528±49.6 v 349±35 dynes, p<0.05). Rapid relaxation to SNP and increase in tension to U46619 was found in both I and O smcs. In smcs from hypertensive vessels Osmcs showed a striking reduction in contraction compared with NOsmcs (177±43dynes, p<0.05) and a slow rate of force development (p<0.05). Maximum force and rate of force development by HIsmcs were normal. HOsmcs had a stable, abnormal structural phenotype that was unexpectedly associated with decreased not increased force generation. Supported by the British Heart Foundation