Smooth Muscle Cell Notch2 Is Not Required for Atherosclerotic Plaque Formation in ApoE Null Mice.

Introduction: We previously identified Notch2 in smooth muscle cells (SMC) in human atherosclerosis and found that signaling via Notch2 suppressed human SMC proliferation. Thus, we tested whether loss of Notch2 in SMC would alter atherosclerotic plaque progression using a mouse model.

Methods: Atherogenesis was examined at the brachiocephalic artery and aortic root in a vascular SMC null (inducible smooth muscle myosin heavy chain Cre) Notch2 strain on the ApoE-/- background. We measured plaque morphology and size, as well as lipid, inflammation, and smooth muscle actin content after Western diet.

Results: We generated an inducible SMC Notch2 null on the ApoE-/- background. We observed ∼90% recombination efficiency with no detectable Notch2 in the SMC. Loss of SMC Notch2 did not significantly change plaque size, lipid content, necrotic core, or medial area. However, loss of SMC Notch2 reduced the contractile SMC in brachiocephalic artery lesions and increased inflammatory content in aortic root lesions after 6 weeks of Western diet. These changes were not present with loss of SMC Notch2 after 14 weeks of Western diet.

Conclusions: Our data show that loss of SMC Notch2 does not significantly reduce atherosclerotic lesion formation, although in early stages of plaque formation there are changes in SMC and inflammation.