Mechanosensor YAP cooperates with TGF-ß1 signaling to promote myofibroblast activation and matrix stiffening in a 3D model of human cardiac fibrosis.

Cardiac fibrosis is characterized by a maladaptive remodeling of the myocardium, which is controlled by various inflammatory pathways and cytokines. This remodeling is accompanied by a significant stiffening of the matrix, which may contribute to further activate collagen synthesis and scar formation. Evidence suggests that TGF-ß1 signaling, the main pro-fibrotic pathway in cardiac fibrosis, might cooperates with the Hippo transcriptional pathway by activating YAP. To directly test the cooperation of mechanical cues and paracrine signaling in cardiac fibrosis, we developed a 3D model of cardiac extracellular matrix remodeling by generating tissue blocks with Gelatin Methacrylate, a bioink with tunable stiffness, and human cardiosphere-derived stromal cells. Using this strategy, we assessed the cooperation of TGF-ß1 and YAP transcriptional factor to matrix compaction. Using mechanical compression tests, Masson's trichrome staining, immunofluorescence, and RT-qPCR, we demonstrate that pharmacological inhibition of YAP complex reverts almost completely the pro-compaction phenotype and the matrix-remodeling activity of cells treated with TGF-ß1. Our data show a direct connection between the classical pro-fibrotic signaling driven by TGF-ß1 and the mechanically activated pathways under the control of YAP in cardiac remodeling. Treatment with the elective drug targeting YAP is sufficient to override this cooperation with potential benefits for anti-fibrotic therapeutic applications. STATEMENT OF SIGNIFICANCE: Heart failure is a pathology in continuous growth worldwide, characterized by a progressive fibrosis, which decreases the pumping efficiency of the heart. Experimental evidences suggest that fibroblasts, normally responsible for the turnover of the cardiac matrix, are involved in myocardial fibrosis by differentiating into 'myofibroblasts'. These cells remodel extensively the cardiac extracellular matrix and deposit abundant collagen with a consequent increase in stiffness. In the present contribution, we propose a new 3D model of cell-mediated cardiac extracellular matrix stiffening to investigate the mechano-chemical mechanisms underlying the onset of the pathology. We also consolidate a pharmacological treatment able to prevent the pathological activation of fibroblasts with potential benefits for anti-fibrotic treatment of the failing heart.

Reduction of Cardiac Fibrosis by Interference With YAP-Dependent Transactivation.

BACKGROUND: Conversion of cardiac stromal cells into myofibroblasts is typically associated with hypoxia conditions, metabolic insults, and/or inflammation, all of which are predisposing factors to cardiac fibrosis and heart failure. We hypothesized that this conversion could be also mediated by response of these cells to mechanical cues through activation of the Hippo transcriptional pathway. The objective of the present study was to assess the role of cellular/nuclear straining forces acting in myofibroblast differentiation of cardiac stromal cells under the control of YAP (yes-associated protein) transcription factor and to validate this finding using a pharmacological agent that interferes with the interactions of the YAP/TAZ (transcriptional coactivator with PDZ-binding motif) complex with their cognate transcription factors TEADs (TEA domain transcription factors), under high-strain and profibrotic stimulation. METHODS: We employed high content imaging, 2-dimensional/3-dimensional culture, atomic force microscopy mapping, and molecular methods to prove the role of cell/nuclear straining in YAP-dependent fibrotic programming in a mouse model of ischemia-dependent cardiac fibrosis and in human-derived primitive cardiac stromal cells. We also tested treatment of cells with Verteporfin, a drug known to prevent the association of the YAP/TAZ complex with their cognate transcription factors TEADs. RESULTS: Our experiments suggested that pharmacologically targeting the YAP-dependent pathway overrides the profibrotic activation of cardiac stromal cells by mechanical cues in vitro, and that this occurs even in the presence of profibrotic signaling mediated by TGF-ß1 (transforming growth factor beta-1). In vivo administration of Verteporfin in mice with permanent cardiac ischemia reduced significantly fibrosis and morphometric remodeling but did not improve cardiac performance. CONCLUSIONS: Our study indicates that preventing molecular translation of mechanical cues in cardiac stromal cells reduces the impact of cardiac maladaptive remodeling with a positive effect on fibrosis.

Engineering Efforts to Refine Compatibility and Duration of Aortic Valve Replacements: An Overview of Previous Expectations and New Promises.

The absence of pharmacological treatments to reduce or retard the progression of cardiac valve diseases makes replacement with artificial prostheses (mechanical or bio-prosthetic) essential. Given the increasing incidence of cardiac valve pathologies, there is always a more stringent need for valve replacements that offer enhanced performance and durability. Unfortunately, surgical valve replacement with mechanical or biological substitutes still leads to disadvantages over time. In fact, mechanical valves require a lifetime anticoagulation therapy that leads to a rise in thromboembolic complications, while biological valves are still manufactured with non-living tissue, consisting of aldehyde-treated xenograft material (e.g., bovine pericardium) whose integration into the host fails in the mid- to long-term due to unresolved issues regarding immune-compatibility. While various solutions to these shortcomings are currently under scrutiny, the possibility to implant fully biologically compatible valve replacements remains elusive, at least for large-scale deployment. In this regard, the failure in translation of most of the designed tissue engineered heart valves (TEHVs) to a viable clinical solution has played a major role. In this review, we present a comprehensive overview of the TEHVs developed until now, and critically analyze their strengths and limitations emerging from basic research and clinical trials. Starting from these aspects, we will also discuss strategies currently under investigation to produce valve replacements endowed with a true ability to self-repair, remodel and regenerate. We will discuss these new developments not only considering the scientific/technical framework inherent to the design of novel valve prostheses, but also economical and regulatory aspects, which may be crucial for the success of these novel designs.

Work flow for the prosthetic rehabilitation of atrophic patients with a minimal-intervention CAD/CAM approach.

The implant-supported fixed rehabilitation of patients with an atrophic edentulous crest remains a challenge if bone augmentation is not planned. A minimal intervention approach for bone regeneration is necessary to minimize the flap overextension needed to close the defect over the augmented bone. Prosthetically guided bone regeneration can determine the amount of bone augmentation necessary for definitive prosthetic fixed rehabilitation. The positions of the implants and prosthetic restoration were planned; a 0.3 mm thick titanium mesh was customized for bone augmentation by using computer-aided design and computer-aided manufacturing and rapid prototyped by laser sintering, and the definitive prosthetic rehabilitation was carried out according to the initial treatment plan. This resulted in minimal bone augmentation relative to the functional needs of the definitive prosthetic rehabilitation.

Volume reduction of cystic lesions after surgical decompression: a computerised three-dimensional computed tomographic evaluation.

OBJECTIVES: This study was performed to evaluate the three-dimensional radiographic variation in mandibular odontogenic cystic lesions after decompression. MATERIALS AND METHODS: Pre- and post-decompression computed tomography (CT) evaluations in 20 patients affected by keratocysts (n = 10), dentigerous cysts (n = 9) and ameloblastoma (n = 1) were analysed using software designed for three-dimensional measurement of volumes; the results were correlated with treatment duration, age, sex and histological type. RESULTS: The mean (range) decompression time was 5.70 (3-12) months. The mean (SD) pre- and post-decompression volumes were 9.50 (7.74) and 4.65 (4.34) cm(3), respectively (P < 0.001), with a mean (SD) reduction of 49.86 % (19.34 %). The volume reduction was positively correlated with the duration of decompression (P < 0.001), whereas no correlations with other variables were found (P = 0.2357). The median monthly reduction in cyst volume was 11.34 % (mean, 13.52 %; range, 4.45-30.43 %) (P < 0.001). CONCLUSIONS: This three-dimensional CT investigation demonstrated the effectiveness of decompression in the treatment of mandibular odontogenic cystic lesions and showed a positive correlation between the duration of treatment and volume reduction. CLINICAL RELEVANCE: Decompression treatment, which is simple to perform and generally well-accepted by patients, is a reliable method to considerably reduce the volume of mandibular odontogenic cystic lesions before surgical removal. Extended decompression time seems to improve results of the reduction process.