Smooth muscle cell phenotypic diversity between dissected and unaffected thoracic aortic media. 
Smooth muscle cell (SMC) phenotypic switching in the aortic media may play a critical role in the pathogenesis of thoracic aortic dissection (TAD).  However, few investigations are available and most of the observations are based on histological examinations without in vitro evidence.  This study, which was performed both in vivo and in vitro, was designed to investigate SMC phenotypic diversity between dissected and unaffected aortic media.  Using optimized explant technique, aortic medial SMCs were obtained from patients with TAD and controls.  In vivo and in vitro expression of α-smooth muscle actin (α-SMA), smooth muscle-myosin heavy chain 2 (SM-MHC-2), smooth muscle-calponin (SM-Calponin), Vimentin, osteopontin (OPN) and non-muscle myosin heavy chain B (SMemb) were evaluated by immunostaining and immunoblotting.  SMC proliferation was also analyzed.  Although the majority of SMCs from the dissected media displayed an elongated, spindle- or triangle-like shape as control SMCs, there were some oval or flat, quadrate cells in the dissection cultures.  In contrast with controls, SMCs derived from the dissected media uniformly showed the negative staining for the contractile proteins and the intense staining for the synthetic markers.  Similarly, in vitro protein levels of α-SMA, SM-MHC-2, SM-Calponin and Vimentin were significantly decreased to 60.1% (P<0.05), 12.0% (P<0.01), 23.1% (P<0.01) and 32.5% (P<0.01) respectively, whereas those of OPN and SMemb were markedly elevated by5.7- and 10.3-fold respectively (P<0.01 for both).  In vivo expression of the phenotypic markers showed the parallel results.  Furthermore, SMCs derived from the dissected media exhibited the enhanced proliferation (P<0.05).  We have established a simple and potent method to acquire SMCs from the dissected and unaffected aortic media.  Compared to the contractile SMCs in the unaffected media, those in the dissected media manifest phenotypic switching from the contractile to the synthetic type.  The primary cultures can be subsequently used as in vitro models and contribute to further elucidating the etiopathogenesis of TAD.