Divergent effects of canonical and non‐canonical TGF‐β signalling on mixed contractile‐synthetic smooth muscle cell phenotype in human Marfan syndrome aortic root aneurysms

Abstract

Aortic root aneurysm formation is a cardinal feature of Marfan syndrome (MFS) and likely TGF-β driven via Smad (canonical) and ERK (non-canonical) signalling. The current study assesses human MFS vascular smooth muscle cell (SMC) phenotype, focusing on individual contributions by Smad and ERK, with Notch3 signalling identified as a novel compensatory mechanism against TGF-β-driven pathology. Although significant ERK activation and mixed contractile gene expression patterns were observed by traditional analysis, this did not directly correlate with the anatomic site of the aneurysm. Smooth muscle cell phenotypic changes were TGF-β-dependent and opposed by ERK in vitro, implicating the canonical Smad pathway. Bulk SMC RNA sequencing after ERK inhibition showed that ERK modulates cell proliferation, apoptosis, inflammation, and Notch signalling via Notch3 in MFS. Reversing Notch3 overexpression with siRNA demonstrated that Notch3 promotes several protective remodelling pathways, including increased SMC proliferation, decreased apoptosis and reduced matrix metalloproteinase activity, in vitro. In conclusion, in human MFS aortic SMCs: (a) ERK activation is enhanced but not specific to the site of aneurysm formation; (b) ERK opposes TGF-β-dependent negative effects on SMC phenotype; (c) multiple distinct SMC subtypes contribute to a 'mixed' contractile-synthetic phenotype in MFS aortic aneurysm; and (d) ERK drives Notch3 overexpression, a potential pathway for tissue remodelling in response to aneurysm formation. K E Y W O R D S aortic aneurysm, Marfan syndrome, smooth muscle cell phenotype 1 | INTRODUC TI ON Marfan syndrome (MFS) is an inheritable connective tissue disorder resulting from fibrillin-1 (Fbn1) mutations with an incidence of 1 in 5000 individuals. 1,2 Aortic root aneurysm formation and ensuing dissection accounts for early mortality if not surgically repaired prophylactically. 3 Transforming growth factor-beta (TGF-β) signalling is central to MFS aortic aneurysm pathogenesis. 4 Despite enhanced S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section. How to cite this article: Pedroza AJ, Koyano T, Trojan J, et al. Divergent effects of canonical and non-canonical TGF-β signalling on mixed contractile-synthetic smooth muscle cell phenotype in human Marfan syndrome aortic root aneurysms.

Quantitative proteomics reveal lineage-specific protein profiles in iPSC-derived Marfan syndrome smooth muscle cells

“…Applying an iTRAQ proteomic strategy, iPSC derived SMCs from MFS patients are utilized to model and investigate human disease mechanisms and discover novel biological pathways that participate in early ECM degeneration. SMC modulation from contractile to the dedifferentiated, synthetic phenotype is known to contribute to aortic aneurysm development 3,35,40 . We recently reported on the "mixed SMC phenotype" in human MFS aortic tissue and primary vascular SMC lines, which overexpressed both contractile and synthetic genes 35 .…”

“…SMC modulation from contractile to the dedifferentiated, synthetic phenotype is known to contribute to aortic aneurysm development 3,35,40 . We recently reported on the "mixed SMC phenotype" in human MFS aortic tissue and primary vascular SMC lines, which overexpressed both contractile and synthetic genes 35 . Similarly, Crosas-Molist et al 36 observed an overexpression of both contractile markers and collagen I in human MFS specimens.…”

“…We next assessed COL1A1 and MMP2 expression in the iPSC SMC system. Enriched expression of these proteins has been identified in both murine models of MFS and human MFS aortic tissue samples 35,36 . In addition to www.nature.com/scientificreports/ the enriched LM:NC ratio identified by iTRAQ, western blot confirmed MFS patient lines overexpressed COL1A1 and MMP2 relative to the control line ( Fig.…”

Insulin‐like growth factor‐binding protein 3 inhibits angiotensin II‐induced aortic smooth muscle cell phenotypic switch and matrix metalloproteinase expression

“…TGF‐β signalling was demonstrated to regulate MSCs’ phenotypic switch and prevent the development of TAD (Milewicz & Ramirez, 2019; Pedroza et al., 2020). Here, we sought to study the molecular mechanism of IGFBP3 in TAD and examine whether the TGF‐β–Smad2 pathway was involved in IGFBP3‐mediated mAoSMCs’ phenotype transformation.…”

Reply From the Author: Respect Mother Nature—aortic Root Repair in Acute Type a Aortic Dissection

“…The human pericardium is composed of fibroblasts and collagen. If the majority of the media is resected as a dissection flap and replaced with pericardium, the elastic aortic root becomes a very stiff aortic root, which is likely more susceptible to aortic root aneurysm as seen in patients with Marfan disease, 8,9 who have significantly more collagen in the aortic root compared to normal people. Technically, it is much more complex to replace all the dissection flaps in 3 aortic sinuses 1 and have more needle holes causing bleeding than simply to obliterate the false lumen by closing the dissection at the sinotubular junction.…”