Embryonic aortic and gizzard smooth muscle cells maintain their contractile phenotypes in culture

Investigations into the determinants of the tonic and phasic contractile properties of smooth muscle (sm) have been hampered by the de-differentiation of sm cells in vitro. We have developed an in vitro system in which sm cells maintain their contractile phenotypes. SM cells derived from ED 10-15 chick aortic (tonic) or gizzard (phasic) tissue expiants were plated at 3 x 10 cells/cm2 for up to three passages in DMEM/F-12+0.5% PCS on simple (0.5% gelatin) or complex (Matrigel™) extra-cellular matrices. KC1 depolarization (90 mM) resulted in single cultured gizzard cells developing 3.0+0.7 (IN of force in 8+2 sec, while single cultured aortic cells developed 0.76+.01 |iN of force in 20+0.7 sec. Cells demonstrated similar contractile characteristics in response to stimulation with phenylephrine, angiotensin n and endothelin-l. Western blotting and RT-PCR was used to show that these cells express a number of the markers of the contractile smooth muscle phenotype. Conclusions: 1) Phasic and tonic sm phenotypes are determined early in development, 2) the phasic and tonic patterns reside at least in part within the single cell, 3) the determinants are inherited through the cell cycle, and 4) an in vitro system can be used to study determinants of sm contractile patterns. Support: NIH K08HL03275 (SAP), HL44181 (FVB), and an AHA El (FVB).