<i>Tcf21</i> lineage traced cells in <i>Ldlr</i>^<i>-/-</i> lesions give rise to smooth muscle cells in the fibrous cap.

<p><i>Tcf21</i>^{<i>iCre/+</i>}, <i>Ldlr</i>^<i>-/-</i> mice were administered tamoxifen to activate expression of an inducible MerCreMer construct knocked into the <i>Tcf21</i> locus to produce recombination and thus expression of a floxed STOP tandem dimer tomato (tdT) reporter gene. Animals received tamoxifen chow at 3–5 weeks of age and were subsequently fed HFD for 16–20 weeks before sacrifice. A) tdT positive cells are seen throughout the lesion and in the adventitia with Tagln staining cells identified in the media and fibrous cap. B) A number of tdT lineage traced cells in the fibrous cap express the SMC marker Acta2 as shown by colocalization of fluorescent markers (yellow arrows). tdT positive cells within the lesion did not express Tagln, as shown by red color (red arrow). C) Some cells in the adventitia stain for periostin expression and colocalize with tdT staining in this location (yellow arrows). Staining for periostin and colocalization with <i>Tcf21</i> lineage cells was also observed in the fibrous cap and subcap (yellow arrows). D) Extensive colocalization was noted for Pdgfra antibody staining and tdT fluorescence in the adventitia and fibrous cap. In, intima; M, media; Ad, adventitia; FC, fibrous cap, Lu, lumen.