Transforming Growth Factor-?1 Inhibits Pseudoaneurysm Formation After Aortic Patch Angioplasty.
ABSTRACT: OBJECTIVE:Pseudoaneurysms remain a significant complication after vascular procedures. We hypothesized that TGF-? (transforming growth factor-?) signaling plays a mechanistic role in the development of pseudoaneurysms. APPROACH AND RESULTS:Rat aortic pericardial patch angioplasty was associated with a high incidence (88%) of pseudoaneurysms at 30 days, with increased smad2 phosphorylation in small pseudoaneurysms but not in large pseudoaneurysms; TGF-?1 receptors were increased in small pseudoaneurysms and preserved in large pseudoaneurysms. Delivery of TGF-?1 via nanoparticles covalently bonded to the patch stimulated smad2 phosphorylation both in vitro and in vivo and significantly decreased pseudoaneurysm formation (6.7%). Inhibition of TGF-?1 signaling with SB431542 decreased smad2 phosphorylation both in vitro and in vivo and significantly induced pseudoaneurysm formation by day 7 (66.7%). CONCLUSIONS:Normal healing after aortic patch angioplasty is associated with increased TGF-?1 signaling, and recruitment of smad2 signaling may limit pseudoaneurysm formation; loss of TGF-?1 signaling is associated with the formation of large pseudoaneurysms. Enhancement of TGF-?1 signaling may be a potential mechanism to limit pseudoaneurysm formation after vascular intervention.
Project description:The high accuracy of multidetector-row computed tomography (MDCT) in evaluating prosthetic valve disorders has been confirmed. This, we believe, is the 1st report of the use of MDCT to detect and evaluate left ventricular outflow tract (LVOT) pseudoaneurysms in patients who have undergone aortic valve replacement with prosthetic valves. We used MDCT to scan 21 such patients, 3 of whom had a small pseudoaneurysm in the LVOT. Each pseudoaneurysm projected away from the LVOT and had a narrow neck that was located just below the sewing ring of the prosthetic aortic valve. One pseudoaneurysm was not thrombotic, 1 was partially thrombotic, and 1 was completely thrombotic. One of these had gone undetected earlier on transthoracic echocardiography.We consider MDCT to be superior to echocardiography in the detection of LVOT pseudoaneurysms in patients who have undergone aortic valve replacement with prosthetic valves. We publicize our results in the hope that larger studies will be undertaken in order to investigate the prevalence and clinical implications of our findings.
Project description:Loeys-Dietz syndrome (LDS) is a connective tissue disorder that is characterized by a high risk for aneurysm and dissection throughout the arterial tree and phenotypically resembles Marfan syndrome. LDS is caused by heterozygous missense mutations in either TGF-? receptor gene (TGFBR1 or TGFBR2), which are predicted to result in diminished TGF-? signaling; however, aortic surgical samples from patients show evidence of paradoxically increased TGF-? signaling. We generated 2 knockin mouse strains with LDS mutations in either Tgfbr1 or Tgfbr2 and a transgenic mouse overexpressing mutant Tgfbr2. Knockin and transgenic mice, but not haploinsufficient animals, recapitulated the LDS phenotype. While heterozygous mutant cells had diminished signaling in response to exogenous TGF-? in vitro, they maintained normal levels of Smad2 phosphorylation under steady-state culture conditions, suggesting a chronic compensation. Analysis of TGF-? signaling in the aortic wall in vivo revealed progressive upregulation of Smad2 phosphorylation and TGF-? target gene output, which paralleled worsening of aneurysm pathology and coincided with upregulation of TGF-?1 ligand expression. Importantly, suppression of Smad2 phosphorylation and TGF-?1 expression correlated with the therapeutic efficacy of the angiotensin II type 1 receptor antagonist losartan. Together, these data suggest that increased TGF-? signaling contributes to postnatal aneurysm progression in LDS.
Project description:The aortic root is the predominant site for development of aneurysm caused by heterozygous loss-of-function mutations in positive effectors of the transforming growth factor-? (TGF-?) pathway. Using a mouse model of Loeys-Dietz syndrome (LDS) that carries a heterozygous kinase-inactivating mutation in TGF-? receptor I, we found that the effects of this mutation depend on the lineage of origin of vascular smooth muscle cells (VSMCs). Secondary heart field-derived (SHF-derived), but not neighboring cardiac neural crest-derived (CNC-derived), VSMCs showed impaired Smad2/3 activation in response to TGF-?, increased expression of angiotensin II (AngII) type 1 receptor (Agtr1a), enhanced responsiveness to AngII, and higher expression of TGF-? ligands. The preserved TGF-? signaling potential in CNC-derived VSMCs associated, in vivo, with increased Smad2/3 phosphorylation. CNC-, but not SHF-specific, deletion of Smad2 preserved aortic wall architecture and reduced aortic dilation in this mouse model of LDS. Taken together, these data suggest that aortic root aneurysm predisposition in this LDS mouse model depends both on defective Smad signaling in SHF-derived VSMCs and excessive Smad signaling in CNC-derived VSMCs. This work highlights the importance of considering the regional microenvironment and specifically lineage-dependent variation in the vulnerability to mutations in the development and testing of pathogenic models for aortic aneurysm.
Project description:This case report represents a novel technique for the treatment of a pseudoaneurysm of the aorta. Pseudoaneurysm of the aorta has been reported in patients post heart surgery. This case report is about a patient who had a pseudoaneurysm most probably following tuberculosis. Traditionally, the treatment of choice is surgical correction; however, in the current era, there are case reports describing the use of either stent grafts or Amplatzer occluders for occlusion of the pseudoaneurysm in high-risk surgical cases. We performed successful closure of the aortic pseudoaneurysm using atrial septal occluder. <Learning objective: Tuberculous arteritis can result in pseudoaneurysm rarely. Our patient had a large aneurysm compressing adjoining vital structures and was very high surgical risk case. This is the first case report of closure of tuberculous pseudoaneurysm by using atrial septal occluder in a young patient. In this case we have demonstrated that large pseudoaneurysms with narrow neck can be closed very safely using atrial septal occluder with immediate symptom relief and thrombosis of pseudoaneurysm at follow-up of three months.>.
Project description:TGF?2 (transforming growth factor-?2) is a key growth factor regulating epithelial to mesenchymal transition (EMT). TGF?2 triggers cardiac progenitor cells to differentiate into mesenchymal cells and give rise to the cellular components of coronary vessels as well as cells of aortic and pulmonary valves. TGF? signaling is dependent on a dynamic on and off switch in Smad activity. Arsenite exposure of 1.34??M for 24-48?h has been reported to disrupt Smad phosphorylation leading to deficits in TGF?2-mediated cardiac precursor differentiation and transformation. In this study, the molecular mechanism of acute arsenite toxicity on TGF?2-induced Smad2/3 nuclear shuttling and TGF?2-mediated cardiac EMT was investigated. A 4-h exposure to 5??M arsenite blocks nuclear accumulation of Smad2/3 in response to TGF?2 without disrupting Smad phosphorylation or nuclear importation. The depletion of nuclear Smad is restored by knocking-down Smad-specific exportins, suggesting that arsenite augments Smad2/3 nuclear exportation. The blockage in TGF?2-Smad signaling is likely due to the loss of Zn(2+) cofactor in Smad proteins, as Zn(2+) supplementation reverses the disruption in Smad2/3 nuclear translocation and transcriptional activity by arsenite. This coincides with Zn(2+) supplementation rescuing arsenite-mediated deficits in cardiac EMT. Thus, zinc partially protects cardiac EMT from developmental toxicity by arsenite.
Project description:Impairment of transforming growth factor (TGF)-beta1 signaling accelerates atherosclerosis in experimental mice. However, it is uncertain whether increased TGF-beta1 expression would retard atherosclerosis. The role of TGF-beta1 in aneurysm formation is also controversial. We tested whether overexpression of active TGF-beta1 in hyperlipidemic mice affects atherogenesis and aortic dilation.We generated apolipoprotein E-null mice with transgenes that allow regulated overexpression of active TGF-beta1 in their hearts. Compared to littermate controls, these mice had elevated cardiac and plasma TGF-beta1, less aortic root atherosclerosis (P< or =0.002), fewer lesions in the thoracic and abdominal aortae (P< or =0.01), less aortic root dilation (P<0.001), and fewer pseudoaneurysms (P=0.02). Mechanistic studies revealed no effect of TGF-beta1 overexpression on plasma lipids or cytokines, or on peripheral lymphoid organ cells. However, aortae of TGF-beta1-overexpressing mice had fewer T-lymphocytes, more collagen, less lipid, lower expression of inflammatory cytokines and matrix metalloproteinase-13, and higher expression of tissue inhibitor of metalloproteinase-2.When overexpressed in the heart and plasma, TGF-beta1 is an antiatherogenic, vasculoprotective cytokine that limits atherosclerosis and prevents aortic dilation. These actions are associated with significant changes in cellularity, collagen and lipid accumulation, and gene expression in the artery wall.
Project description:To improve cartilage formation by bone marrow-derived mesenchymal stem cells (BMSCs), the signaling mechanism governing chondrogenic differentiation requires better understanding. We previously showed that the transforming growth factor-? (TGF?) receptor ALK5 is crucial for chondrogenesis induced by TGF?. ALK5 phosphorylates SMAD2 and SMAD3 proteins, which then form complexes with SMAD4 to regulate gene transcription. By modulating the expression of SMAD2, SMAD3 and SMAD4 in human BMSCs, we investigated their role in TGF?-induced chondrogenesis. Activation of TGF? signaling, represented by SMAD2 phosphorylation, was decreased by SMAD2 knockdown and highly increased by SMAD2 overexpression. Moreover, TGF? signaling via the alternative SMAD1/5/9 pathway was strongly decreased by SMAD4 knockdown. TGF?-induced chondrogenesis of human BMSCs was strongly inhibited by SMAD4 knockdown and only mildly inhibited by SMAD2 knockdown. Remarkably, both knockdown and overexpression of SMAD3 blocked chondrogenic differentiation. Chondrogenesis appears to rely on a delicate balance in the amount of SMAD3 and SMAD4 as it was not enhanced by SMAD4 overexpression and was inhibited by SMAD3 overexpression. Furthermore, this study reveals that TGF?-activated phosphorylation of SMAD2 and SMAD1/5/9 depends on the abundance of SMAD4. Overall, our findings suggest a more dominant role for SMAD3 and SMAD4 than SMAD2 in TGF?-induced chondrogenesis of human BMSCs.
Project description:PURPOSE:We present ultrasound-guided percutaneous low-dose thrombin (200-250 IU) injection for the treatment of iatrogenic femoral pseudoaneurysms. Second, we compared patient and procedure factors between subcutaneous hematoma and pseudoaneurysm groups. MATERIALS AND METHODS:From April 2012 to May 2018, 8425 patients underwent neurointervention. Among these patients, 18 had small subcutaneous hematomas and 6 had pseudoaneurysms. Pseudoaneurysms in the neck and entire sac were visualized, and low-dose thrombins were injected while visualizing a "whirlpool" hyperechoic core in the pseudoaneurysm sac. Subcutaneous hematomas were treated with simple compression. We compared the following parameters between the subcutaneous hematoma group and pseudoaneurysm group: sex, age, body mass index (BMI), type of procedure, heparin usage, sheath size, procedure time, and number of previous neurointervention procedures with the Mann-Whitney U test. RESULTS:Most of the pseudoaneurysms were successfully occluded with 200 IU of thrombin (n=5). Only 1 pseudoaneurysm required a slightly higher thrombin concentration (250 IU, n=1). During the short-term follow-up, no residual sac was observed and no surgical repair was necessary. Pain in the groin region was alleviated. During the 1-month follow-up, no evidence of pseudoaneurysm recurrence nor subcutaneous hematoma was noted. Patient factors (sex, age, and BMI) and procedure factors (heparin usage, sheath size, procedure time, number of previous procedures) were not statistically different between the subcutaneous hematoma and pseudoaneurysm groups. CONCLUSION:Ultrasound-guided percutaneous low-dose thrombin injection (200-250 IU) is safe, effective, and less invasive for treating iatrogenic femoral pseudoaneurysm in neurointervention.
Project description:Transforming growth factor-beta (TGF-beta) is an important regulator of physiological connective tissue biosynthesis and plays a central role in pathological tissue fibrosis. Previous studies have established that a biologically active lipid mediator, sphingosine 1-phosphate (S1P), mimics some of the profibrotic functions of TGF-beta through cross-activation of Smad signaling. Here we report that another product of sphingosine kinase, dihydrosphingosine 1-phosphate (dhS1P), has an opposite role in the regulation of TGF-beta signaling. In contrast to S1P, dhS1P inhibits TGF-beta-induced Smad2/3 phosphorylation and up-regulation of collagen synthesis. The effects of dhS1P require a lipid phosphatase, PTEN, a key modulator of cell growth and survival. dhS1P stimulates phosphorylation of the C-terminal domain of PTEN and its subsequent translocation into the nucleus. We demonstrate a novel function of nuclear PTEN as a co-factor of the Smad2/3 phosphatase, PPM1A. Complex formation of PTEN with PPM1A does not require the lipid phosphatase activity but depends on phosphorylation of the serine/threonine residues located in the C-terminal domain of PTEN. Upon complex formation with PTEN, PPM1A is protected from degradation induced by the TGF-beta signaling. Consequently, overexpression of PTEN abrogates TGF-beta-induced Smad2/3 phosphorylation. This study establishes a novel role for nuclear PTEN in the stabilization of PPM1A. PTEN-mediated cross-talk between the sphingolipid and TGF-beta signaling pathways may play an important role in physiological and pathological TGF-beta signaling.
Project description:KLF4 (Krüppel-like factor 4) has been implicated in vascular smooth muscle cell (VSMC) differentiation induced by transforming growth factor beta (TGF-beta). However, the role of KLF4 and mechanism of KLF4 actions in regulating TGF-beta signaling in VSMCs remain unclear. In this study, we showed that TGF-beta1 inhibited cell cycle progression and induced differentiation in cultured rat VSMCs. This activity of TGF-beta1 was accompanied by up-regulation of KLF4, with concomitant increase in TbetaRI (TGF-beta type I receptor) expression. KLF4 was found to transduce TGF-beta1 signals via phosphorylation-mediated activation of Smad2, Smad3, and p38 MAPK. The activation of both pathways, in turn, increased the phosphorylation of KLF4, which enabled the formation of KLF4-Smad2 complex in response to TGF-beta1. Chromatin immunoprecipitation studies and oligonucleotide pull-down assays showed the direct binding of KLF4 to the KLF4-binding sites 2 and 3 of the TbetaRI promoter and the recruitment of Smad2 to the Smad-responsive region. Formation of a stable KLF4-Smad2 complex in the promoter's Smad-responsive region mediated cooperative TbetaRI promoter transcription in response to TGF-beta1. These results suggest that KLF4-dependent regulation of Smad and p38 MAPK signaling via TbetaRI requires prior phosphorylation of KLF4 through Smad and p38 MAPK pathways. This study demonstrates a novel mechanism by which TGF-beta1 regulates VSMC differentiation.