Promoters to Study Vascular Smooth Muscle

Abstract

Smooth muscle cells (SMCs) are a critical component of blood vessel walls that provide structural support, regulate vascular tone, and allow for vascular remodeling. These cells also exhibit a remarkable plasticity that contributes to vascular growth and repair but also to cardiovascular pathologies, including atherosclerosis, intimal hyperplasia and restenosis, aneurysm, and transplant vasculopathy. Mouse models have been an important tool for the study of SMC functions. The development of smooth muscle-expressing Cre -driver lines has allowed for exciting discoveries, including recent advances revealing the diversity of phenotypes derived from mature SMC transdifferentiation in vivo using inducible CreER T2 lines. We review SMC-targeting Cre lines driven by the Myh11, Tagln , and Acta2 promoters, including important technical considerations associated with these models. Limitations that can complicate study of the vasculature include expression in visceral SMCs leading to confounding phenotypes, and expression in multiple nonsmooth muscle cell types, such as Acta2-Cre expression in myofibroblasts. Notably, the frequently employed Tagln / SM22 α- Cre driver expresses in the embryonic heart but can also confer expression in nonmuscular cells including perivascular adipocytes and their precursors, myeloid cells, and platelets, with important implications for interpretation of cardiovascular phenotypes. With new Cre -driver lines under development and the increasing use of fate mapping methods, we are entering an exciting new era in SMC research.

Disease-relevant single cell photonic signatures identify S100β stem cells and their myogenic progeny in vascular lesions

“…Although the Myh11-CreERT2 transgene was originally deemed specific for vascular SMC 71 , data indicating expression of this and other SMC differentiation genes in non-SMC populations has recently emerged raising the possibility that other resident cells may contribute to lesion formation [72][73][74] .…”

“…Despite extensive research, their origin remains controversial. Although the Myh11-CreERT2 transgene was originally deemed specific for vascular SMC cell fate mapping studies [44], data indicating expression of this and other SMC differentiation genes in non-SMC populations has recently emerged [45][46][47] raising the possibility that other resident cells may contribute to lesion formation. In this study, we provide compelling genetic evidence using lineage tracing analysis that vascular lesions contain an abundance of S100β + cells that originate from a non-SMC perivascular S100β + parent population in support of other studies demonstrating a stem cell origin for lesional cells [9,12,13] .…”

Primed smooth muscle cells acting as first responder cells in disease

“…Animal experiments were approved by the local ethics committee and performed according to UK Home Office regulation under project license P452C4595. All alleles have been described previously; Myh11-CreERt2 (Myh11) confers expression of a tamoxifen-inducible Cre recombinase in smooth muscle cells 18,19 , Rosa26-Confetti (Confetti) 20 and Rosa26-EYFP (EYFP) 21 are Cre-recombination reporter alleles, Ki67/RFP is an insertion in the Mki67 locus resulting in expression of a KI67/RFP fusion protein 22 and the mutant Apoe allele sensitizes mice to high fat diet (HFD)-induced atherosclerosis development 23 . VSMC lineage labeling was achieved by intraperitoneal tamoxifen injections (10x 0.1 mg tamoxifen over 2 weeks) followed by at least 1 week rest period for tamoxifen metabolism.…”

The calcium binding protein S100β marks hedgehog-responsive resident vascular stem cells within vascular lesions

“…Single cell RNA sequence analysis (scRNA-seq) further identified a Sca1 + Myh11-Cre marked SMC subpopulation that give rise to functionally distinct neointimal cells during lesion progression in mice (Chappell et al, 2016;Dobnikar et al, 2018). However, although the Myh11-CreERT2 transgene was originally deemed specific for vascular SMC (Owens, 2007), data indicating expression of this and other 'SMC differentiation genes' in non-SMC populations has recently emerged raising the possibility that other resident cells may contribute to lesion formation (Chakraborty et al, 2019;Murgai et al, 2017;Sheikh et al, 2014).…”