Extensibility and Distensibility of the Thoracic Aorta in Patients with Aneurysm.

OBJECTIVES: Reference values of aortic deformation during the cardiac cycle can be valuable for the pre-operative planning of thoracic endovascular aortic repair (TEVAR) and for facilitating computational fluid dynamics. This study aimed to quantify normal aortic extensibility (longitudinal extension) and distensibility (radial expansion), as well as pulsatile strain, in a group of 10 (>60 years) individuals with abdominal or thoracic aortic aneurysms. METHODS: ECG gated CT images of the thoracic aorta were reconstructed into virtual 3D models of aortic geometry. The centre lumen line length of the thoracic aorta and three longitudinal segments, and the aortic diameter and luminal areas of four radial intersections were extracted with a dedicated software script to calculate extensibility, longitudinal strain, distensibility, and circumferential area strain. RESULTS: Mean extensibility and longitudinal strain of the entire thoracic aorta were 3.5 [1.3-6.8] × 10-3 N-1, and 2.7 [1.0-4.5]%, respectively. Extensibility and longitudinal strain were most pronounced in the ascending aorta (20.6 [5.7-36.2] × 10-3 N-1 and 15.9 [6.6-31.9]%) and smallest in the descending aorta (4.4 [1.6-12.3] × 10-3 N-1 and 2.2 [0.7-4.7]%). Mean distensibility and circumferential area strain were most pronounced at the sinotubular junction (1.7 [0.5-2.9] × 10-3 mmHg-1 and 11.3 [3.3-18.5]%, respectively). Distensibility varied between 0.9 [0.3-2.5] × 10-3 mmHg-1 and 1.2 [0.3-3.3] × 10-3 mmHg-1 at the intersections in the aortic arch and descending aorta. CONCLUSIONS: Pulsatile deformations in both longitudinal and circumferential directions are considerable throughout the thoracic aorta. These findings may have implications for pre-operative TEVAR planning and highlight the need for devices that can mimic the significant aortic longitudinal and circumferential strains.

Experimental and computational analysis of a pharmaceutical-grade shape memory polymer applied to the development of gastroretentive drug delivery systems.

The present paper aims at developing an integrated experimental/computational approach towards the design of shape memory devices fabricated by hot-processing with potential for use as gastroretentive drug delivery systems (DDSs) and for personalized therapy if 4D printing is involved. The approach was tested on a plasticized poly(vinyl alcohol) (PVA) of pharmaceutical grade, with a glass transition temperature close to that of the human body (i.e., 37 °C). A comprehensive experimental analysis was conducted in order to fully characterize the PVA thermo-mechanical response as well as to provide the necessary data to calibrate and validate the numerical predictions, based on a thermo-viscoelastic constitutive model, implemented within a finite element framework. Particularly, a thorough thermal, mechanical, and shape memory characterization under different testing conditions and on different sample geometries was first performed. Then, a prototype consisting of an S-shaped device was fabricated, deformed in a temporary compact configuration and tested. Simulation results were compared with the results obtained from shape memory experiments carried out on the prototype. The proposed approach provided useful results and recommendations for the design of PVA-based shape memory DDSs.

Toward the improvement of 3D-printed vessels' anatomical models for robotic surgery training.

Multi-Detector Computed Tomography is nowadays the gold standard for the pre-operative imaging for several surgical interventions, thanks to its excellent morphological definition. As for vascular structures, only the blood flowing inside vessels can be highlighted, while vessels' wall remains mostly invisible. Image segmentation and three-dimensional-printing technology can be used to create physical replica of patient-specific anatomy, to be used for the training of novice surgeons in robotic surgery. To this aim, it is fundamental that the model correctly resembles the morphological properties of the structure of interest, especially concerning vessels on which crucial operations are performed during the intervention. To reach the goal, vessels' actual size must be restored, including information on their wall. Starting from the correlation between vessels' lumen diameter and their wall thickness, we developed a semi-automatic approach to compute the local vessels' wall, bringing the vascular structures as close as possible to their actual size. The optimized virtual models are suitable for manufacturing by means of three-dimensional-printing technology to build patient-specific phantoms for the surgical simulation of robotic abdominal interventions. The proposed approach can effectively lead to the generation of vascular models of optimized thickness wall. The feasibility of the approach is also tested on a selection of clinical cases in abdominal surgery, on which the robotic surgery is performed on the three-dimensional-printed replica before the actual intervention.

Inhibition of the SH3 domain-mediated binding of Src to the androgen receptor and its effect on tumor growth.

In human mammary and prostate cancer cells, steroid hormones or epidermal growth factor (EGF) trigger association of the androgen receptor (AR)-estradiol receptor (ER) (alpha or beta) complex with Src. This interaction activates Src and affects the G1 to S cell cycle progression. In this report, we identify the sequence responsible for the AR/Src interaction and describe a 10 amino-acid peptide that inhibits this interaction. Treatment of the human prostate or mammary cancer cells (LNCaP or MCF-7, respectively) with nanomolar concentrations of this peptide inhibits the androgen- or estradiol-induced association between the AR or the ER and Src the Src/Erk pathway activation, cyclin D1 expression and DNA synthesis, without interfering in the receptor-dependent transcriptional activity. Similarly, the peptide prevents the S phase entry of LNCaP and MCF-7 cells treated with EGF as well as mouse embryo fibroblasts stimulated with androgen or EGF. Interestingly, the peptide does not inhibit the S phase entry and cytoskeletal changes induced by EGF or serum treatment of AR-negative prostate cancer cell lines. The peptide is the first example of a specific inhibitor of steroid receptor-dependent signal transducing activity. The importance of these results is highlighted by the finding that the peptide strongly inhibits the growth of LNCaP xenografts established in nude mice.

New frontiers and emerging applications of 3D printing in ENT surgery: a systematic review of the literature.

3D printing systems have revolutionised prototyping in the industrial field by lowering production time from days to hours and costs from thousands to just a few dollars. Today, 3D printers are no more confined to prototyping, but are increasingly employed in medical disciplines with fascinating results, even in many aspects of otorhinolaryngology. All publications on ENT surgery, sourced through updated electronic databases (PubMed, MEDLINE, EMBASE) and published up to March 2017, were examined according to PRISMA guidelines. Overall, 121 studies fulfilled specific inclusion criteria and were included in our systematic review. Studies were classified according to the specific field of application (otologic, rhinologic, head and neck) and area of interest (surgical and preclinical education, customised surgical planning, tissue engineering and implantable prosthesis). Technological aspects, clinical implications and limits of 3D printing processes are discussed focusing on current benefits and future perspectives.

Computational simulation of TEVAR in the ascending aorta for optimal endograft selection: A patient-specific case study.

Thoracic endovascular aortic repair of the ascending aorta is becoming an option for patients considered unfit for open surgery. Such an endovascular procedure requires careful pre-operative planning and the customization of prosthesis design. The patient-specific tailoring of the procedure may call for dedicated tools to investigate virtual treatment scenarios. Given such considerations, the present study shows a computational framework for choosing and deploying stent-grafts via Finite Element Analysis, by supporting the device sizing and selection in a real case dealing with the endovascular treatment of a pseudoaneurysm. In particular, three devices with various lengths and materials were examined. Two off-the-shelf devices were computationally tested: one composed of Stainless Steel rings with a nominal length of 60 mm and another one with Nitinol rings and a distal free flow extension, with a nominal length of 70 mm. In third place, a custom-made stent-graft, also with Nitinol rings and containing both proximal and distal bare extensions with a nominal length of 75 mm, was deployed. The latter solution based on patient morphology and virtually benchmarked in this simulation framework, enhanced the apposition to the wall by reducing the distance between the skirt and the vessel from more than 6 mm to less than 2 mm in the distal sealing zone. Our experience shows that in-silico simulations can help choosing the right endograft for the ascending aorta as well as the right deployment sequence. This process may also encourage vendors to develop new devices for cases where open repair is unfeasible.

From CT scanning to 3D printing technology: a new method for the preoperative planning of a transcutaneous bone-conduction hearing device.

SUMMARY: The aim of the present study was to assess the feasibility and utility of 3D printing technology in surgical planning of a transcutaneous bone-conduction hearing device (Bonebridge®) (BB), focusing on the identification of the proper location and placement of the transducer. 3D printed (3DP) models of three human cadaveric temporal bones, previously submitted to CT scan, were created with the representation of a topographic bone thickness map and the sinus pathway on the outer surface. The 3DP model was used to detect the most suitable location for the BB. A 3DP transparent mask that faithfully reproduced the surface of both the temporal bone and the 3DP model was also developed to correctly transfer the designated BB area. The accuracy of the procedure was verified by CT scan: a radiological marker was used to evaluate the degree of correspondence of the transducer site between the 3DP model and the human temporal bone. The BB positioning was successfully performed on all human temporal bones, with no difficulties in finding the proper location of the transducer. A mean error of 0.13 mm was found when the transducer site of the 3DP model was compared to that of the human temporal bone. The employment of 3D printing technology in surgical planning of BB positioning showed feasible results. Further studies will be required to evaluate its clinical applicability.

Multi-objective optimization of nitinol stent design.

Nitinol stents continuously experience loadings due to pulsatile pressure, thus a given stent design should possess an adequate fatigue strength and, at the same time, it should guarantee a sufficient vessel scaffolding. The present study proposes an optimization framework aiming at increasing the fatigue life reducing the maximum strut strain along the structure through a local modification of the strut profile.The adopted computational framework relies on nonlinear structural finite element analysis combined with a Multi Objective Genetic Algorithm, based on Kriging response surfaces. In particular, such an approach is used to investigate the design optimization of planar stent cell.The results of the strut profile optimization confirm the key role of a tapered strut design to enhance the stent fatigue strength, suggesting that it is possible to achieve a marked improvement of both the fatigue safety factor and the scaffolding capability simultaneously. The present study underlines the value of advanced engineering tools to optimize the design of medical devices.

Estradiol activation of human colon carcinoma-derived Caco-2 cell growth.

This is the first report on estrogen-dependent growth of human-derived colon carcinoma cells. Under selected conditions, growth of subconfluent Caco-2 cells is triggered by estradiol. Cell growth is estradiol concentration dependent, with maximal effect occurring at about 0.4 nM. Growth is prevented by two different antiestrogens: the partial agonist, OH-Tamoxifen, and the pore antagonist, ICI 182,780. The growth effect is specific for estradiol since other hormonal steroids tested do not affect cell growth. The amount of estradiol receptor in subconfluent Caco-2 cells, detected by blot with monoclonal antibodies directed against the receptor as well as estradiol binding assays, is similar to that of the classical estradiol-responsive, human mammary cancer-derived MCF-7 cells. Estradiol treatment of subconfluent Caco-2 cells rapidly and reversibly stimulates four important intermediates in a signal transduction pathway that is known to trigger cell proliferation: two members of the large family of c-src-related tyrosine kinases, c-src and c-yes, and two serine/threonine kinases, the mitogen-activated protein (MAP) kinases, erk-1 and erk-2. Tyrosine kinases activated by estradiol are up-stream MAP kinases and Caco-2 cell proliferation. In fact, genistein, a specific tyrosine kinase inhibitor, abolishes the estradiol stimulatory effect on both erk-2 activity and cell proliferation. Our findings show that in subconfluent Caco-2 cells, the estradiol-receptor complex activates the c-src, c-yes/MAP kinase pathway and activates growth. This could have important implications for the understanding of human intestinal carcinogenesis.

Fatigue of Metallic Stents: From Clinical Evidence to Computational Analysis.

The great success of stents in treating cardiovascular disease is actually undermined by their long-term fatigue failure. The high variability of stent failure incidence suggests that it is due to several correlated aspects, such as loading conditions, material properties, component design, surgical procedure, and patient functional anatomy. Numerical and experimental non-clinical assessments are included in the recommendations and requirements of several regulatory bodies and they are thus exploited in the analysis of stent fatigue performance. Optimization-based simulation methodologies have been developed as well, to improve the fatigue endurance of novel designs. This paper presents a review on the fatigue issue in metallic stents, starting from a description of clinical evidence about stent fracture up to the analysis of computational approaches available from the literature. The reported discussion on both the experimental and numerical framework aims at providing a general insight into stent lifetime prediction as well as at understanding the factors which affect stent fatigue performance for the design of novel components.

Prediction of patient-specific post-operative outcomes of TAVI procedure: The impact of the positioning strategy on valve performance.

Prosthesis positioning in transcatheter aortic valve implantation procedures represents a crucial aspect for procedure success as demonstrated by many recent studies on this topic. Possible complications, device performance, and, consequently, also long-term durability are highly affected by the adopted prosthesis placement strategy. In the present work, we develop a computational finite element model able to predict device-specific and patient-specific replacement procedure outcomes, which may help medical operators to plan and choose the optimal implantation strategy. We focus in particular on the effects of prosthesis implantation depth and release angle. We start from a real clinical case undergoing Corevalve self-expanding device implantation. Our study confirms the crucial role of positioning in determining valve anchoring, replacement failure due to intra or para-valvular regurgitation, and post-operative device deformation.

An innovative strategy for the identification and 3D reconstruction of pancreatic cancer from CT images.

We propose an innovative tool for Pancreatic Ductal AdenoCarcinoma 3D reconstruction from Multi-Detector-Computed Tomography. The tumor mass is discriminated from health tissue, and the resulting segmentation labels are rendered preserving information on different hypodensity levels. The final 3D virtual model includes also pancreas and main peri-pancreatic vessels, and it is suitable for 3D printing. We performed a preliminary evaluation of the tool effectiveness presenting ten cases of Pancreatic Ductal AdenoCarcinoma processed with the tool to an expert radiologist who can correct the result of the discrimination. In seven of ten cases, the 3D reconstruction is accepted without any modification, while in three cases, only 1.88, 5.13, and 5.70 %, respectively, of the segmentation labels are modified, preliminary proving the high effectiveness of the tool.

Immediate and transient stimulation of protein tyrosine phosphorylation by estradiol in MCF-7 cells.

Estradiol stimulates protein phosphorylation on tyrosine in human breast cancer MCF-7 cells under conditions of estradiol-stimulated cell growth. The stimulatory effect of estradiol has been observed by 32P-labeling of cells followed by purification of proteins using antiphosphotyrosine antibody coupled to agarose and confirmed by immunoblotting analysis with antiphosphotyrosine antibody. This stimulation is immediate (maximal in 10 s) and transient. In addition, it is receptor-mediated since estradiol stimulation is prevented by two well-known antiestrogens, OH-Tamoxifen and ICI 164,384. Estradiol fails to stimulate tyrosine protein phosphorylation of Cos cells which do not express the estradiol receptor. Two substrates of the estrogen stimulated phosphorylation on tyrosine with approximate mol wt of 55 and 60 kDa interact with a polyclonal antibody raised against amino acids 527-533 of pp60c-src (anti-cst.1 antibody). Tyrosine kinase activity of immunoprecipitates made using either anti cst.1 antibody or the monoclonal 327 antibody specific for pp60c-src shows that kinase(s) strongly related to pp60c-src are immediately and transiently stimulated by estradiol treatment of cells. The present findings provide the first demonstration that a steroid hormone rapidly stimulates tyrosine phosphorylation of target cells and induces functional modifications of substrates of this phosphorylation. These modifications might initiate the estradiol action on cell growth.

In vitro interaction of estradiol receptor with Ca2+-calmodulin.

Estradiol receptor (ER) activity requires interaction with hormone and specific DNA sequence. We now report that this receptor also interacts with calmodulin (CaM), the major intracellular mediator of Ca2+ action in eucaryotic cells. This interaction has been observed using both CaM-Sepharose and [125I]CaM. Crude and purified [3H]ER complex show high affinity interaction with CaM-Sepharose [dissociation constant (Kd) 0.12 and 0.16 nM, respectively]. Unoccupied receptor shows a similar high affinity interaction. Tamoxifen-ER complex also binds to CaM-Sepharose. Several findings show that this CaM-ER interaction is very specific: lack of this interaction has been observed in the presence of trifluoperazine, an inhibitor of protein binding to CaM; the receptor binds neither Sepharose, nor parvalbumin-Sepharose; competition of interaction of [3H]ER complex with CaM-Sepharose is observed by cold ER complex; rat liver glucocorticoid receptor does not bind to CaM-Sepharose. The interaction of purified receptor with 125I-labeled CaM has been detected by various techniques: centrifugation through sucrose gradient of CaM incubated with receptor shows that CaM binds to a protein forming a complex sedimenting at 5 S. This complex is shifted to the 7.5 S region by a monoclonal antireceptor antibody. Incubation of CaM with receptor followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis fluorography of the immunoprecipitated receptor shows that [125I]CaM coprecipitates with the receptor. Competition of this interaction by an excess of cold CaM is observed. Interaction of the receptor with CaM is also observed by the overlay technique.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphorylation on tyrosine of in vitro synthesized human estrogen receptor activates its hormone binding.

Hormone binding controls the activity of estradiol receptor. The in vitro synthesized human receptor binds hormone with high affinity and low efficiency (1-4% of the maximal binding). We now report that phosphorylation on tyrosine of the synthetic receptor by an extensively purified calf uterus kinase increases hormone binding towards maximal levels without change in affinity. This is the first direct demonstration that a newly synthesized hormone receptor acquires ligand binding through phosphorylation. The use of in vitro synthesized proteins as substrates for enzymes which cause functional modifications of proteins is very promising because it is easy to identify the modified domains and residues by using deleted and point mutated proteins. Experiments with two estradiol receptor deletion mutants, one which lacks the N-terminal half of the receptor and binds hormone independently from the N-terminal half of the receptor, the other which lacks the C-terminal half of the receptor and contains the domain required to recognize the estradiol responsive elements, show that tyrosine phosphorylation occurs exclusively within or near the hormone binding domain of the receptor.

Serine phosphorylation of biosynthetic pro-urokinase from human tumor cells.

Phosphorylation is a potent mechanism regulating the activity of many intracellular enzymes. We have discovered that the product of the human urokinase plasminogen activator gene, pro-uPA, is phosphorylated in serine in at least two human cell lines. Phosphorylation occurs within the cell during biosynthesis, and phosphorylated intracellular pro-uPA is secreted into the medium. Of the secreted pro-uPA molecules, 20-50% are phosphorylated in serine, thus representing a meaningful fraction of the total biosynthetic pro-uPA. Although the sites of phosphorylation have not yet been determined, at least two such sites must exist; in fact plasmin cleavage of phosphorylated single chain pro-uPA yields a two chain uPA in which both chains are phosphorylated. A specific function for pro-uPA phosphorylation has not yet been identified; however, it is tempting to speculate that, as in many other cases, phosphorylation may affect the activity of the enzyme, its response to inhibitors or the conversion of pro-uPA zymogen to active two-chain uPA. This would represent an additional way of regulating extracellular proteolysis, an important pathway involved in both intra- and extravascular phenomena like fibrinolysis, cell migration and invasiveness.

Oestrogen receptor in mammary gland cytosol of virgin, pregnant and lactating mice.

A macromolecular component binding 3H-labelled 17 beta-oestradiol in a specific manner and sedimenting in the 8-10-S region on sucrose gradient has been detected in the mammary gland cytosol of ovariectomized adult virgin mice. The dissociation constant of the macromolecule-oestradiol complex is 4.2 times 10(-10)M at 4 degrees C. The binding sites for 17beta-oestradiol of cytosol are 3.7 times 10(-14) mole/mg of protein. Incubation of cytosol with different enzymes suggests that the oestrogen-binding cytosol component is proteinaceous. The binding activity is destroyed by incubation at high temperatures and by some but not all SH-reagents tested. Competition studies show a specificity for oestrogens relative to other steroid hormones. The conclusion is that mammary gland cytosol of virgin mice contains oestradiol receptor. The receptor content does not increase in a specific manner during pregnancy and lactation but rather proportionally to total mammary gland protein.

In vitro phosphorylation and hormone binding activation of the synthetic wild type human estradiol receptor.

A tyrosine kinase purified from calf uterus activates the hormone binding of endogenous estradiol receptor (ER) predephosphorylated and preinactivated by a nuclear phosphotyrosine phosphatase. The kinase also activates and phosphorylates the human estradiol receptor HEO synthesized in vitro, which differs from the wild type receptor HEGO because a glycine is replaced by a valine at position 400. Moreover, the kinase activates and phosphorylates a deletion mutant of HEO which consists almost exclusively of the hormone binding domain. Using HEGO and HEO in parallel and measuring both binding activation and phosphorylation of ER we now observe that the wild type receptor is a good kinase substrate, slightly better than HEO. Furthermore, HEGO like the calf uterus receptor in the presence of estradiol, stimulates the kinase. From present findings it appears that ER and uterus tyrosine kinase are functionally associated and that this association is abolished by glycine to valine substitution at position 400 of ER.

Sex steroid hormones act as growth factors.

We observed that sex steroid hormones, like growth factors, stimulate the Src/Ras/erk pathway of cell lines derived from human mammary or prostate cancers. In addition, hormone-dependent pathway activation can be induced in Cos cells, upon transfection of classic steroid receptors. Cross-talks between sex steroid receptors regulate their association with Src and consequent pathway activation. Oestradiol treatment of MCF-7 cells triggers simultaneous association of ER with Src and p85, the regulatory subunit of phosphatidylinositol-3-kinase (PI3-kinase) and activation of Src- and PI3-K-dependent pathways. Activation of the latter pathway triggers cyclin D1 transcription, that is unaffected by Mek-1 activation. This suggests that simultaneous activation of different signalling effectors is required to target different cell cycle components. Thus, a novel reciprocal cross-talk between the two pathways appears to be mediated by the ER. In all tested cells, activation of the signalling pathways has a proliferative role. Transcriptionally inactive ER expressed in NIH 3T3 cells responds to hormone causing Src/Ras/Erk pathway activation and DNA synthesis. This suggests that in these cells genomic activity is required for later events of cell growth.

Src is an initial target of sex steroid hormone action.

Recent observations that steroids use pathways universally known to be regulated by growth factors and interleukins highlight the following points: (1) Steroid stimulation of the canonical pathway Src/Ras/Erk signaling from membrane to nuclei or its single members has been observed in different cell types including human cancer-derived cells, neurons, osteoblasts, osteocytes, and endothelial cells. This stimulation has been reconstituted and analyzed in transiently transfected cells. (2) Cellular context and intracellular localization of receptors are crucial in determining the biological effects evoked by this hormonal stimulation: proliferation, protection from apoptosis, and vasorelaxation. (3) Classical steroid receptors localized in the extranuclear compartment directly and, in some cases, simultaneously interact with Src. They are capable of unexpected cross talks responsible for the observed effects. (4) Other signaling pathways including P13K/AKT are also stimulated by steroids. The aim of future work will be to arrive at an integrated general view of the different signaling pathways activated by steroids and to analyze the concert between these pathways and the hormonal transcriptional action. This general view should be simultaneously verified in different cell contexts, under different physiologic and pathologic conditions. We expect that the new technologies, above all gene and protein microarray, will make this goal feasible.