The appearance of phagocytic microglia in the postnatal brain of Niemann Pick type C mice is developmentally regulated and underscores shortfalls in fine odor discrimination.

The loss of NPC1 or NPC2 function results in cholesterol and sphingolipid dyshomeostasis that impairs developmental trajectories, predisposing the postnatal brain to the appearance of pathological signs, including progressive and stereotyped Purkinje cell loss and microgliosis. Despite increasing evidence reporting the activation of pro-inflammatory microglia as a cardinal event of NPC1 disease progression at symptomatic stages both in patients and preclinical models, how microglia cells respond to altered neurodevelopmental dynamics remains not completely understood. To gain an insight on this issue, we have characterized patterns of microglia activation in the early postnatal cerebellum and young adult olfactory bulb of the hypomorphic Npc1nmf164 mouse model. Previous evidence has shown that both these areas display a number of anomalies affecting neuron and glial cell proliferation and differentiation, which largely anticipate cellular changes and clinical signs, raising our interest on how microglia interplay to these changes. Even so, to separate the contribution of cues provided by the dysfunctional microenvironment we have also studied microglia isolated from mice of increasing ages and cultured in vitro for 1 week. Our findings show that microglia of both cerebellum and olfactory bulb of Npc1nmf164 mice adopt an activated phenotype, characterized by increased cell proliferation, enlarged soma size and de-ramified processes, as well as a robust phagocytic activity, in a time- and space-specific manner. Enhanced phagocytosis associates with a profound remodeling of gene expression signatures towards gene products involved in chemotaxis, cell recognition and engulfment, including Cd68 and Trem2. These early changes in microglia morphology and activities are induced by region-specific developmental anomalies that likely anticipate alterations in neuronal connectivity. As a proof of concept, we show that microglia activation within the granule cell layer and glomerular layer of the olfactory bulb of Npc1nmf164 mice is associated with shortfalls in fine odor discrimination.

Cell phenotypic plasticity requires autophagic flux driven by YAP/TAZ mechanotransduction.

Autophagy, besides ensuring energy metabolism and organelle renewal, is crucial for the biology of adult normal and cancer stem cells. However, it remains incompletely understood how autophagy connects to stemness factors and the nature of the microenvironmental signals that pattern autophagy in different cell types. Here we advance in these directions by reporting that YAP/TAZ transcriptionally control autophagy, being critical for autophagosomal degradation into autolysosomes. YAP/TAZ are downstream effectors of cellular mechanotransduction and indeed we found that cell mechanics, dictated by the physical property of the ECM and cytoskeletal tension, profoundly impact on autophagic flux in a YAP/TAZ-mediated manner. Functionally, by using pancreatic and mammary organoid cultures, we found that YAP/TAZ-regulated autophagy is essential in normal cells for YAP/TAZ-mediated dedifferentiation and acquisition of self-renewing properties. In tumor cells, the YAP/TAZ-autophagy connection is key to sustain transformed traits and for acquisition of a cancer stem cell state by otherwise more benign cells. Mechanistically, YAP/TAZ promote autophagic flux by directly promoting the expression of Armus, a RAB7-GAP required for autophagosome turnover and whose add-back rescues autophagy in YAP/TAZ-depleted cells. These findings expand the influence of YAP/TAZ mechanotransduction to the control of autophagy and, vice versa, the role of autophagy in YAP/TAZ biology, and suggest a mechanism to coordinate transcriptional rewiring with cytoplasmic restructuring during cell reprogramming.

Outcome of permanent pacemaker implantation in transcatheter or surgical aortic valve replacement: A still unsolved problem.

Despite advances in technologies and clinical experience, conduction disorders, after transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (SAVR), represent the weak point of these procedures, requiring permanent pacemaker implantation (PPI) till 37.7% of patients in TAVR recipients. The role of PPI in TAVR and SAVR remains controversial in mid- and long-term outcomes. Indeed, many studies have been published with contradictory results, leaving doubts rather than certainties.

A morphofunctional analysis of the regurgitant mitral valve as a guide to repair: Another point of view.

Based on Carpentier's classification and principles, the techniques for mitral valve repair continue to evolve. We herein report our experience with the morphofunctional echocardiographic analysis of single mitral leaflets, as different anatomic features, even if conflicting, may coexist not only in the two leaflets but in the same leaflet as well. A classification is proposed, based on the length (normal, short, or long) and mobility (normal, restricted, or excessive) of mitral leaflets. The surgical techniques adopted for mitral valve repair are the direct consequence of this analysis.

Cutting the second order chords during mitral valve repair.

The chordae tendinae connect the papillary muscles (PMs) to the mitral valve. While the first-order chordae serve to secure the leaflets to maintain valve closure and prevent mitral valve prolapse, the second-order chordae are believed to play a role in maintaining normal left ventricle size and geometry. The PMs, from where the chordae tendinae originate, function as shock absorbers that compensate for the geometric changes of the left ventricular wall. The second-order chordae connect the PMs to both trigons under tension. The tension distributed towards the second-order chordae has been demonstrate to be more than threefold that in their first-order counterpart. Cutting the second-order chordae puts all the tension on the first-order chordae, which are then closer to their rupture point. However, it has been experimentally demonstrated that the tension at which the first-order chordae break is 6.8 newtons (N), by far higher than the maximal tension reached, that is 0.4 N. Even if the clinical reports have been favorable, the importance of cutting the second-order chordae to recover curvature of the anterior leaflet and increase the coaptation length between the mitral valve leaflets has been slowly absorbed by the surgical world. Nevertheless, there are progressive demonstrations that chordal tethering affects the anterior leaflet not only in secondary, but also in primary mitral regurgitation, having a not negligible role in the long-term outcome of mitral repair.

Neutrophil to lymphocyte ratio predicts permanent pacemaker implantation in TAVR patients.

INTRODUCTION: In this prospective multicenter analysis, we aimed to investigate the predictive role of neutrophil/lymphocyte ratio (NLR) in permanent pacemaker implantation (PPI) in patients undergoing transcatheter aortic valve replacement (TAVR). MATERIALS AND METHODS: One hundred and seventy-nine consecutive patients without previous PPI underwent TAVR from February 2017 to September 2021. Patients were further divided based on presence (n = 48) and absence of conduction abnormalities (CAs) at hospital admission (n = 131). RESULTS: In patients with previous CAs, NLR values did not differ significantly between patients requiring PPI (n = 16, 33%) and those not requiring it. In contrast, in patients with no CAs at hospital admission, NLR values measured at admission and on TAVR day were significantly higher in patients requiring PPI (n = 17, 13%) (4.07 ± 3.22 vs. 3.01 ± 1.47, p = .025, and 10.81 ± 7.81 vs. 5.84 ± 3.78, p = .000, respectively). Multivariable analysis showed that NLR at TAVR day was an independent predictor of PPI in patients without CAs (OR 1.294; 95% CI 1.028-1.630; p = .028), but not in those with previous CAs. ROC curve analysis showed that the cut point was a NLR value of >7.25. Time to PPI was delayed till 21 days in patients without CAs. CONCLUSIONS: In this prospective study, higher NLR values on the day of TAVR day were associated with an increased PPI rate in patients undergoing TAVR with no previous CAs. It is advisable, being inflammation part of the process, to prolong the time of observation for all patients without CAs till at least 21 days not to miss any new CA necessitating PPI.

A historical appraisal of the techniques of left ventricular volume reduction in ischemic cardiomyopathy: Who did what?

Resection or exclusion of scars following a myocardial infarction on the left anterior descending artery territory started even before the beginning of the modern era of cardiac surgery. Many techniques were developed, but there is still confusion on who did what. The original techniques underwent modifications that brought to a variety of apparently new procedures that, however, were only a "revisitation" of what described before. In some case, old techniques were reproposed and renamed, without giving credit to the surgeon that was the original designer. Herein we try to describe which are the seminal procedures and some of the most important modifications, respecting however the merit of who first communicated the procedure to the scientific world.

Reprogramming normal cells into tumour precursors requires ECM stiffness and oncogene-mediated changes of cell mechanical properties.

Defining the interplay between the genetic events and microenvironmental contexts necessary to initiate tumorigenesis in normal cells is a central endeavour in cancer biology. We found that receptor tyrosine kinase (RTK)-Ras oncogenes reprogram normal, freshly explanted primary mouse and human cells into tumour precursors, in a process requiring increased force transmission between oncogene-expressing cells and their surrounding extracellular matrix. Microenvironments approximating the normal softness of healthy tissues, or blunting cellular mechanotransduction, prevent oncogene-mediated cell reprogramming and tumour emergence. However, RTK-Ras oncogenes empower a disproportional cellular response to the mechanical properties of the cell's environment, such that when cells experience even subtle supra-physiological extracellular-matrix rigidity they are converted into tumour-initiating cells. These regulations rely on YAP/TAZ mechanotransduction, and YAP/TAZ target genes account for a large fraction of the transcriptional responses downstream of oncogenic signalling. This work lays the groundwork for exploiting oncogenic mechanosignalling as a vulnerability at the onset of tumorigenesis, including tumour prevention strategies.

Publisher Correction: Reprogramming normal cells into tumour precursors requires ECM stiffness and oncogene-mediated changes of cell mechanical properties.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The secret life of the mitral valve.

In secondary mitral regurgitation, the concept that the mitral valve (MV) is an innocent bystander, has been challenged by many studies in the last decades. The MV is a living structure with intrinsic plasticity that reacts to changes in stretch or in mechanical stress activating biohumoral mechanisms that have, as purpose, the adaptation of the valve to the new environment. If the adaptation is balanced, the leaflets increase both surface and length and the chordae tendineae lengthen: the result is a valve with different characteristics, but able to avoid or to limit the regurgitation. However, if the adaptation is unbalanced, the leaflets and the chords do not change their size, but become stiffer and rigid, with moderate or severe regurgitation. These changes are mediated mainly by a cytokine, the transforming growth factor-ß (TGF-ß), which is able to promote the changes that the MV needs to adapt to a new hemodynamic environment. In general, mild TGF-ß activation facilitates leaflet growth, excessive TGF-ß activation, as after myocardial infarction, results in profibrotic changes in the leaflets, with increased thickness and stiffness. The MV is then a plastic organism, that reacts to the external stimuli, trying to maintain its physiologic integrity. This review has the goal to unveil the secret life of the MV, to understand which stimuli can trigger its plasticity, and to explain why the equation "large heart = moderate/severe mitral regurgitation" and "small heart = no/mild mitral regurgitation" does not work into the clinical practice.

Association of tethering of the second-order chords and prolapse of the first-order chords of the anterior leaflet: A risk factor for early and late repair failure.

BACKGROUND AND AIM: Second-order chord tethering of the anterior leaflet is a risk factor for failure of posterior leaflet prolapse repair. MATERIALS AND METHODS: We describe two cases of second-order chord tethering of the anterior leaflet associated with severe mitral regurgitation due to prolapse or chordal rupture of the anterior leaflet, causing early and late failure of repair. RESULTS: We described two cases where this phenomenon happened. CONCLUSIONS: Our cases demonstrate that the second-order chords of the prolapsing AL can be tethered and that this aspect should be carefully evaluated before surgery, as it can progress over time, affecting the results of surgical repair.

Surgical mitral plasticity for chronic ischemic mitral regurgitation.

BACKGROUND AND AIM OF THE STUDY: The outcome of mitral valve (MV) repair for chronic ischemic mitral regurgitation (IMR) is suboptimal, due to the high recurrence rate of moderate or severe mitral regurgitation (MR) during follow-up. The MV adapts to new MR increasing its area to cover the enlarged annular area (mitral plasticity). As this process is often incomplete, we aimed to evaluate if augmenting the anterior leaflet (AL) and cutting the second-order chords (CC) together with restrictive mitral annuloplasty, a strategy we call "surgical mitral plasticity," could improve the midterm results of MV repair for IMR. MATERIALS AND METHODS: From November 2017 to October 2019, 22 patients with chronic IMR underwent surgical mitral plasticity. Mean age was 73 ± 7 years and six were female. Mean ejection fraction was 32% ± 11%, IMR grade was moderate in 10 and severe in 12. Mean clinical and echocardiographic follow-up was 12 ± 6 months. RESULTS: There was no early death, and one patient died 6 months after surgery. Ejection fraction improved from 32% ± 15% to 40% ± 6% (P = .031). IMR was absent or mild in all patients, and none showed recurrent moderate or more IMR. Tenting area decreased significantly from 2.5 ± 0.5 to 0.5 ± 0.3 cm² and coaptation length increased from 1.9 ± 0.7 to 7.8 ± 1.6 mm. All patients were in New York Heart Association class I or II. CONCLUSIONS: Mitral plasticity, if uncomplete, is ineffective in preventing IMR to become significant. Surgical mitral plasticity, by completing incomplete process of MV adaptation, has a strong rationale, which however needs to be validated with longer follow-up.

The endocannabinoid system is affected by cholesterol dyshomeostasis: Insights from a murine model of Niemann Pick type C disease.

The dyshomeostasis of intracellular cholesterol trafficking is typical of the Niemann-Pick type C (NPC) disease, a fatal inherited lysosomal storage disorder presenting with progressive neurodegeneration and visceral organ involvement. In light of the well-established relevance of cholesterol in regulating the endocannabinoid (eCB) system expression and activity, this study was aimed at elucidating whether NPC disease-related cholesterol dyshomeostasis affects the functional status of the brain eCB system. To this end, we exploited a murine model of NPC deficiency for determining changes in the expression and activity of the major molecular components of the eCB signaling, including cannabinoid type-1 and type-2 (CB1 and CB2) receptors, their ligands, N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), along with their main synthesizing/inactivating enzymes. We found a robust alteration of distinct components of the eCB system in various brain regions, including the cortex, hippocampus, striatum and cerebellum, of Npc1-deficient compared to wild-type pre-symptomatic mice. Changes of the eCB component expression and activity differ from one brain structure to another, although 2-AG and AEA are consistently found to decrease and increase in each structure, respectively. The thorough biochemical characterization of the eCB system was accompanied by a behavioral characterization of Npc1-deficient mice using a number of paradigms evaluating anxiety, locomotor activity, spatial learning/memory abilities, and coping response to stressful experience. Our findings provide the first description of an early and region-specific alteration of the brain eCB system in NPC and suggest that defective eCB signaling could contribute at producing and/or worsening the neurological symptoms of this disorder.

Early alteration of distribution and activity of hippocampal type-1 cannabinoid receptor in Alzheimer's disease-like mice overexpressing the human mutant amyloid precursor protein.

Besides its involvement in Alzheimer's disease (AD) as precursor of the neurotoxic amyloid peptides, the pathophysiological impact of brain accumulation of amyloid precursor protein (APP) is not yet well understood. Recent studies reported that APP interacts with other membrane proteins, including G protein coupled receptors, affecting their biological functions. Here, we focused on the study of the potential impact of human mutant APP on expression, distribution and activity of type-1 cannabinoid (CB1) receptor in the hippocampus of Tg2576 mice, an AD-like mice model. By using biochemical and electrophysiological measures, we found that in a presymptomatic phase, when amyloid plaques have not yet formed and there is no sign of cognitive deficits, the over-expression of full-length APP in the hippocampus of Tg2576 mice altered membrane localization and inhibitory signalling activity of CB1 receptor, possibly by binding to the receptor and reducing its specific interaction with caveolin-1 and G proteins.

Role of palmitoylation of cysteine 415 in functional coupling CB1 receptor to Gαi2 protein.

In this study, we investigated the role of CB1 palmitoylation in modulating the functional interaction with G proteins both in the absence and presence of agonist binding. Our data show that the nonpalmitoylated CB1 receptor significantly reduced its association with Gαi2 . The agonist stimulation induced a partial dissociation of Gαi2 proteins from the wild-type receptor, while on the C415A mutant the agonist binding was not able to induce a significant dissociation of Gαi2 from the receptor. The lack of palmitoyl chain seems to hamper the ability of the receptor to functionally interact with the Gαi2 and indicate that the palmitoyl chain is responsible for the functional transmission of the agonist-induced conformational change in the receptor of the G protein. These data were further corroborated by molecular dynamics simulations. Overall these results suggest that palmitoylation of the CB1 receptor finely tunes its interaction with G proteins and serves as a targeting signal for its functional regulation. Of note, the possibility to reversibly modulate the palmitoylation of CB1 receptor may offer a coordinated process of regulation and could open new therapeutic approaches.

Full Orifice Patching without Annuloplasty for Severe Functional Tricuspid Valve Regurgitation.

Surgical treatment of severe functional tricuspid regurgitation associated with dilated right ventricle and increased chordal tethering (>8 mm) is challenging. We designed a technique where the anterior and posterior leaflets are detached from 50% of the annulus and a patch as large as the tricuspid orifice is sewn to augment the leaflets' tissue to force the coaptation with the septal leaflet. Annuloplasty is not performed, as it can only increase the chordal tethering, reducing the benefit of tissue augmentation. Early and midterm results in a subgroup of patients with unfavorable anatomical aspects are encouraging.

Palmitoylation of cysteine 415 of CB1 receptor affects ligand-stimulated internalization and selective interaction with membrane cholesterol and caveolin 1.

We previously demonstrated that CB1 receptor is palmitoylated at cysteine 415, and that such a post-translational modification affects its biological activity. To assess the molecular mechanisms responsible for modulation of CB1 receptor function by S-palmitoylation, in this study biochemical and morphological approaches were paralleled with computational analyses. Molecular dynamics simulations suggested that this acyl chain stabilizes helix 8 as well as the interaction of CB1 receptor with membrane cholesterol. In keeping with these in silico data, experimental results showed that the non-palmitoylated CB1 receptor was unable to interact efficaciously with caveolin 1, independently of its activation state. Moreover, in contrast with the wild-type receptor, the lack of S-palmitoylation in the helix 8 made the mutant CB1 receptor completely irresponsive to agonist-induced effects in terms of both lipid raft partitioning and receptor internalization. Overall, our results support the notion that palmitoylation of cysteine 415 modulates the conformational state of helix 8 and influences the interactions of CB1 receptor with cholesterol and caveolin 1, suggesting that the palmitoyl chain may serve as a functional interface for CB1 receptor localization and function.

Prolonged QT and myocardium recovery after primary PCI: a cMRI study.

BACKGROUND: The presence of viable stunned myocardium recovering after primary angioplasty is not easy to identify in the early phase of acute myocardial infarction (AMI) by noninvasive bed-side methods. We therefore aimed to assess whether a simple electrocardiogram parameter may be of help in identifying the presence of stunned viable myocardium recovering after reperfusion with primary angioplasty. MATERIALS AND METHODS: A total of 14 consecutive patients with ST-elevation AMI (STEMI) were enrolled in the study and underwent QT duration assessment after admission: the difference between QT corrected (QTc) in the ischaemic areas and QTc values in nonischaemic areas was therefore calculated and compared with the presence and the extension of viable stunned myocardium, assessed by comparing akinetic/dyskinetic areas at admission echocardiography with akinetic/dyskinetic areas and extension of scar at 6-month cardiac magnetic resonance imaging (cMRI). RESULTS: In subjects with viable recovering myocardium, 75% had a QTc max > 440 ms (vs. 17%, P = 0·03); higher differential QTc values and smaller scar areas were found (33 ms vs. -17 ms, 14% vs. 27%, P = 0·03, 0·06 respectively). Differential QTc values > 0 were able to identify the presence of viable myocardium with an odds ratio of 35 (P < 0·05, sensitivity 88%, specificity 83%, positive predictive power 88%, negative predictive power of 83%). Differential QTc values were related to the extension of viable recovering myocardium (P < 0·001). CONCLUSION: Viable myocardium recovering after primary angioplasty in STEMI may be predicted by the presence of increased QTc values in ischaemic areas in comparison with nonischaemic areas.