Maine Medical Center, Medical Education, Maine Medical Center Research Institute
Plaque, Atherosclerotic, NOTCH2 protein, human, Receptor, Notch2, Myocytes, Smooth Muscle
Background: Vascular occlusive diseases, such as atherosclerosis, underlie ischemic heart disease and stroke, the leading causes of death worldwide. We are interested in vascular smooth muscle cells (SMC) in the pathogenesis of disease, as they contribute to plaque formation and may determine susceptibility to rupture upon switching from a quiescent/contractile phenotype to a proliferative/migratory one. Notch signaling is implicated in vascular disease progression, and we previously identified a Notch receptor-specific regulatory role in SMC proliferation and contractile phenotype. We thus hypothesize that Notch signaling within vascular SMC can regulate plaque morphology.
Methods: To study this in vivo, we developed a mouse model that is Notch2 null in SMC for mice that are susceptible to atherosclerosis. Recombination in Notch2 flox mice causes deletion of exon 3 and a premature truncation of Notch2 protein, so these mice were crossed to the smooth muscle myosin heavy chain-CreERT2 to specifically delete Notch2 in vascular SMC in apolipoprotein E deficient mice. Following induction of atherosclerosis with atherogenic diet for 6 or 14 weeks, aortas, brachiocephalic arteries, and aortic roots were harvested and examined for plaque burden and composition by tissue staining.
Results: We validated genomic recombination in our model by PCR and qPCR of aorta denuded of adventitia and endothelium and found a 90% genomic knockdown efficiency with no detectable Notch2 protein in SMC. Loss of SMC Notch2 has no significant effect on enface aortic plaque burden assessed by Oil Red O staining nor on morphometric measurements of hematoxylin and eosin stained brachiocephalic arteries in mice fed atherogenic diet for 14 weeks. Loss of SMC Notch2 results in aortic root plaques with a greater inflammatory cell content after 6 weeks of atherogenic diet and that are larger after 14 weeks of atherogenic diet. Conclusion: SMC Notch2 may have an athero-protective role for some blood vessels.
Davis-Knowlton, Jess; Turner, Jackie; Harrington, Anne; and Liaw, Lucy, "The Role of Smooth Muscle Cell Notch2 in Atherosclerotic Plaque Burden and Composition" (2020). Costas T. Lambrew Research Retreat 2020. 36.