Vascular smooth muscle-specific YAP/TAZ deletion triggers aneurysm development in mouse aorta

Inadequate adaption to mechanical forces, including blood pressure, contributes to development of arterial aneurysms. Recent studies have pointed to a mechanoprotective role of YAP and TAZ in vascular smooth muscle cells (SMCs). Here, we identified reduced expression of YAP1 in human aortic aneurysms. Vascular SMC-specific knockouts (KOs) of YAP/TAZ were thus generated using the integrin α8-Cre (Itga8-Cre) mouse model (i8-YT-KO). i8-YT-KO mice spontaneously developed aneurysms in the abdominal aorta within 2 weeks of KO induction and in smaller arteries at later times. The vascular specificity of Itga8-Cre circumvented gastrointestinal effects. Aortic aneurysms were characterized by elastin disarray, SMC apoptosis, and accumulation of proteoglycans and immune cell populations. RNA sequencing, proteomics, and myography demonstrated decreased contractile differentiation of SMCs and impaired vascular contractility. This associated with partial loss of myocardin expression, reduced blood pressure, and edema. Mediators in the inflammatory cGAS/STING pathway were increased. A sizeable increase in SOX9, along with several direct target genes, including aggrecan (Acan), contributed to proteoglycan accumulation. This was the earliest detectable change, occurring 3 days after KO induction and before the proinflammatory transition. In conclusion, Itga8-Cre deletion of YAP and TAZ represents a rapid and spontaneous aneurysm model that recapitulates features of human abdominal aortic aneurysms.

Transcription factor GATA6 promotes migration of human coronary artery smooth muscle cells in vitro

Vascular smooth muscle cell plasticity plays a pivotal role in the pathophysiology of vascular diseases. Despite compelling evidence demonstrating the importance of transcription factor GATA6 in vascular smooth muscle, the functional role of GATA6 remains poorly understood. The aim of this study was to elucidate the role of GATA6 on cell migration and to gain insight into GATA6-sensitive genes in smooth muscle. We found that overexpression of GATA6 promotes migration of human coronary artery smooth muscle cells in vitro, and that silencing of GATA6 in smooth muscle cells resulted in reduced cellular motility. Furthermore, a complete microarray screen of GATA6-sensitive gene transcription resulted in 739 upregulated and 248 downregulated genes. Pathways enrichment analysis showed involvement of transforming growth factor beta (TGF-β) signaling which was validated by measuring mRNA expression level of several members. Furthermore, master regulators prediction based on microarray data revealed several members of (mitogen activated protein kinase) MAPK pathway as a master regulators, reflecting involvement of MAPK pathway also. Our findings provide further insights into the functional role of GATA6 in vascular smooth muscle and suggest that targeting GATA6 may constitute as a new approach to inhibit vascular smooth muscle migration.

YAP and TAZ in Vascular Smooth Muscle Confer Protection Against Hypertensive Vasculopathy

BACKGROUND

Hypertension remains a major risk factor for cardiovascular diseases, but the underlying mechanisms are not well understood. We hypothesize that appropriate mechanotransduction and contractile function in vascular smooth muscle cells are crucial to maintain vascular wall integrity. The Hippo pathway effectors YAP (yes-associated protein 1) and TAZ (WW domain containing transcription regulator 1) have been identified as mechanosensitive transcriptional coactivators. However, their role in vascular smooth muscle cell mechanotransduction has not been investigated in vivo.

METHODS

We performed physiological and molecular analyses utilizing an inducible smooth muscle-specific YAP/TAZ knockout mouse model.

RESULTS

Arteries lacking YAP/TAZ have reduced agonist-mediated contraction, decreased myogenic response, and attenuated stretch-induced transcriptional regulation of smooth muscle markers. Moreover, in established hypertension, YAP/TAZ knockout results in severe vascular lesions in small mesenteric arteries characterized by neointimal hyperplasia, elastin degradation, and adventitial thickening.

CONCLUSIONS

This study demonstrates a protective role of YAP/TAZ against hypertensive vasculopathy.

MRTFA overexpression promotes conversion of human coronary artery smooth muscle cells into lipid-laden foam cells

OBJECTIVE

Smooth muscle cells contribute significantly to lipid-laden foam cells in atherosclerotic plaques. However, the underlying mechanisms transforming smooth muscle cells into foam cells are poorly understood. The purpose of this study was to gain insight into the molecular mechanisms regulating smooth muscle foam cell formation.

APPROACH AND RESULTS

Using human coronary artery smooth muscle cells we found that the transcriptional co-activator MRTFA promotes lipid accumulation via several mechanisms, including direct transcriptional control of LDL receptor, enhanced fluid-phase pinocytosis and reduced lipid efflux. Inhibition of MRTF activity with CCG1423 and CCG203971 significantly reduced lipid accumulation. Furthermore, we demonstrate enhanced MRTFA expression in vascular remodeling of human vessels.

CONCLUSIONS

This study demonstrates a novel role for MRTFA as an important regulator of lipid homeostasis in vascular smooth muscle cells. Thus, MRTFA could potentially be a new therapeutic target for inhibition of vascular lipid accumulation.

Extracellular-Matrix-Reinforced Bioinks for 3D Bioprinting Human Tissue

Recent advances in 3D bioprinting allow for generating intricate structures with dimensions relevant for human tissue, but suitable bioinks for producing translationally relevant tissue with complex geometries remain unidentified. Here, a tissue-specific hybrid bioink is described, composed of a natural polymer, alginate, reinforced with extracellular matrix derived from decellularized tissue (rECM). rECM has rheological and gelation properties beneficial for 3D bioprinting while retaining biologically inductive properties supporting tissue maturation ex vivo and in vivo. These bioinks are shear thinning, resist cell sedimentation, improve viability of multiple cell types, and enhance mechanical stability in hydrogels derived from them. 3D printed constructs generated from rECM bioinks suppress the foreign body response, are pro-angiogenic and support recipient-derived de novo blood vessel formation across the entire graft thickness in a murine model of transplant immunosuppression. Their proof-of-principle for generating human tissue is demonstrated by 3D bioprinting human airways composed of regionally specified primary human airway epithelial progenitor and smooth muscle cells. Airway lumens remained patent with viable cells for one month in vitro with evidence of differentiation into mature epithelial cell types found in native human airways. rECM bioinks are a promising new approach for generating functional human tissue using 3D bioprinting.

Inducible Deletion of YAP and TAZ in Adult Mouse Smooth Muscle Causes Rapid and Lethal Colonic Pseudo-Obstruction

BACKGROUND & AIMS

YAP (Yap1) and TAZ (Wwtr1) are transcriptional co-activators and downstream effectors of the Hippo pathway, which play crucial roles in organ size control and cancer pathogenesis. Genetic deletion of YAP/TAZ has shown their critical importance for embryonic development of the heart, vasculature, and gastrointestinal mesenchyme. The aim of this study was to determine the functional role of YAP/TAZ in adult smooth muscle cells in vivo.

METHODS

Because YAP and TAZ are mutually redundant, we used YAP/TAZ double-floxed mice crossed with mice that express tamoxifen-inducible CreER^T2 recombinase driven by the smooth muscle-specific myosin heavy chain promoter.

RESULTS

Double-knockout of YAP/TAZ in adult smooth muscle causes lethality within 2 weeks, mainly owing to colonic pseudo-obstruction, characterized by severe distension and fecal impaction. RNA sequencing in colon and urinary bladder showed that smooth muscle markers and muscarinic receptors were down-regulated in the YAP/TAZ knockout. The same transcripts also correlated with YAP/TAZ in the human colon. Myograph experiments showed reduced contractility to depolarization by potassium chloride and a nearly abolished muscarinic contraction and spontaneous activity in colon rings of YAP/TAZ knockout.

CONCLUSIONS

YAP and TAZ in smooth muscle are guardians of colonic contractility and control expression of contractile proteins and muscarinic receptors. The knockout model has features of human chronic intestinal pseudo-obstruction and may be useful for studying this disease.

[A perimyocarditis revealing eosinophilic granulomatosis with polyangiitis]

Churg-Strauss syndrome (CSS) or eosinophilic granulomatosis with polyangiitis is a systemic vasculitis characterized by necrotizing arteritis, eosinophilic infiltration and extravascular granuloma; that may involve several organs. Cardiac involvement is the first cause of death in this vasculitis. These include myocarditis, pericarditis, coronary heart disease, dysrhythmias, and rarely valvular involvement. We report the observation of CSS revealed by acute perimyocarditis.

Antagonistic relationship between the unfolded protein response and myocardin-driven transcription in smooth muscle

Smooth muscle cells (SMCs) are characterized by a high degree of phenotypic plasticity. Contractile differentiation is governed by myocardin-related transcription factors (MRTFs), in particular myocardin (MYOCD), and when their drive is lost, the cells become proliferative and synthetic with an expanded endoplasmic reticulum (ER). ER is responsible for assembly and folding of secreted proteins. When the load on the ER surpasses its capacity, three stress sensors (activating transcription factor 6 [ATF6], inositol-requiring enzyme 1α [IRE1α]/X-box binding protein 1 [XBP1], and PERK/ATF4) are activated to expand the ER and increase its folding capacity. This is referred to as the unfolded protein response (UPR). Here, we hypothesized that there is a reciprocal relationship between SMC differentiation and the UPR. Tight negative correlations between SMC markers (MYH11, MYOCD, KCNMB1, SYNPO2) and UPR markers (SDF2L1, CALR, MANF, PDIA4) were seen in microarray data sets from carotid arterial injury, partial bladder outlet obstruction, and bladder denervation, respectively. The UPR activators dithiothreitol (DTT) and tunicamycin (TN) activated the UPR and reduced MYOCD along with SMC markers in vitro. The IRE1α inhibitor 4μ8C counteracted the effect of DTT and TN on SMC markers and MYOCD expression. Transfection of active XBP1s was sufficient to reduce both MYOCD and the SMC markers. MRTFs also antagonized the UPR as indicated by reduced TN and DTT-mediated induction of CRELD2, MANF, PDIA4, and SDF2L1 following overexpression of MRTFs. The latter effect did not involve the newly identified MYOCD/SRF target MSRB3, or reduced production of either XBP1s or cleaved ATF6. The UPR thus counteracts SMC differentiation via the IRE1α/XBP1 arm of the UPR and MYOCD repression.

Pulmonary hypertension on systemic sclerosis-lupus erythematosus overlap syndrome

PURPOSE

There are authentic observations of combination of systemic lupus erythematosus (SLE) with systemic sclerosis (SS) and with polymyositis defined as overlap syndromes. The prevalence of pulmonary hypertension is unknown in SS-SLE overlap syndrome because of its rarity. The aim of our study was to precise clinical, paraclinical and evolutive features of pulmonary hypertension in patients with systemic sclerosis-systemic lupus erythematosus (SS-SLE) overlap syndrome.

METHODS

Sixteen cases of SS-SLE overlap syndrome were retrospectively studied in a period of 16 years (2000-2015). SS-SLE overlap syndrome was diagnosed in the presence of at least 4 criteria of the American College of Rheumatology (ACR) for the diagnosis of SLE and a major criterion or 2 minor criteria of ACR of SS classification. Pulmonary arterial pressure (PAP) was estimated with doppler echocardiography. Pulmonary hypertension (PAH) was defined by a PAP superior than 30mmHg. We distributed groups according to the existence (Group 1) or not (Group 2) of a PAH. Epidemiological, clinical and evolutive features were compared between the two groups with bilateral fisher test (P significant if inferior at 0.05) RESULTS: Sixteen cases of female patients with SS-SLE overlap syndrome with a middle-age of 39 years, extreme (29-58 years) were studied. PAH complicated the evolution of SS-SLE overlap syndrome in six cases with a middle-age of 41 years. Ten patients of the group 2 had an average age of 40 years. The average age of the beginning of the disease was 28 years in the group 1 and 31 years in the group 2. SS preceded SLE in 6 among 16 cases (Group 1: 2/6, Group 2: 4/10). SS was revealed most frequently by Raynauw's Syndrome in both groups (Group 1: 4/6, Group 2: 7/10). Cutaneous and articular involvements were the most frequent observed manifestations of SLE (Group 1: 5/6, Group 2: 6/10). In the group 1, the PAH was discovered approximatively11 years after the beginning of the SS-SLE overlap syndrome. The average PAP was 52mmHg, extreme (32-80mmHg). A right cardiac insufficiency complicated the evolution of the PAH in 3 cases. The PAH was primitive in 3 cases. There was no significant difference concerning the SS-SLE overlap syndrome onset disease symptoms, the frequency of lung involvement and esophageal, neurological, articular and trophic manifestations. PAH was not associated with lupic proliferative renal disease, neither with cutaneous proximal sclerosis nor with anti-Scl70 positivity. Patients were treated with vasodilator treatment in eleven cases: prostacyclin derivates in five cases and endothelin receptor antagonist in six cases. Two patients received corticosteroids and boli of cyclophosphamide for renal involvement and neurologic involvement in each case. Stabilization of PAP was observed in these two cases. Mean follow-up disease was 67 months, extreme (4-124 months) Cutaneous sclerosis evolution was not significantly different between both groups. Global cardiac insufficiency secondary to PAH caused death in one case.

CONCLUSION

According to the results of our study, SS-SLE overlap syndrome complicated with PAH seems to be associated more frequently with limited and distal cutaneous manifestations. Patients that have developed lupus nephropathy and/or had positive anti-Scl70 seem to be protected from appearance of PAH during the SS-SLE overlap syndrome.

Travel medicine consultation: An opportunity to improve coverage for routine vaccinations

BACKGROUND

Travelers may be responsible for the spread of vaccine-preventable diseases upon return. Travel physicians and family physicians may play a role in checking and updating vaccinations before traveling. Our aim was to evaluate the vaccine coverage for mandatory and recommended vaccination in travelers attending a travel medicine clinic (TMC).

METHODS

Vaccine coverage was measured using the current French immunization schedule as reference for correct immunization, in travelers providing a vaccination certificate during the TMC visit (university hospital of Saint-Étienne), between August 1, 2013 and July 31, 2014.

RESULTS

In total, 2336 travelers came to the TMC during the study period. Among the 2019 study participants, only 1216 (60.3%) provided a vaccination certificate. Travelers who provided a vaccination certificate were significantly younger than travelers who did not (mean age: 34.8±17.8 vs. 46±18.4 years, P<0.005) and were less likely to be Hajj pilgrims. Vaccine coverage against Tetanus, Diphtheria, and Poliomyelitis (Td/IPV vaccine) was 91.8%, 78.6% against Measles, Mumps, and Rubella (MMR), and 59.4% against Viral Hepatitis B (HBV). BCG vaccine coverage was 71.9%. Older travelers were less likely to be correctly vaccinated, except against HBV as vaccinated travelers were significantly older than unvaccinated travelers.

CONCLUSION

Obtaining information about immunization in travelers is difficult. Coverage for routine vaccines should be improved in this population. Travel medicine consultations could be the opportunity to vaccinate against MMR, HBV, and Td/IPV.