First description and validation of a new method for estimating aortic stenosis burden and predicting the functional response to TAVI.

Background: Up to one-fifth of patients continue to have poor quality of life after transcatheter aortic valve implantation (TAVI), with an additional similar proportion not surviving 1 year after the procedure. We aimed to assess the value of a new method based on an integrated analysis of left ventricular outflow tract flow velocity and aortic pressure to predict objective functional improvement and prognosis after TAVI. Methods: In a cohort of consecutive patients undergoing TAVI, flow velocity-pressure integrated analysis was obtained from simultaneous pressure recordings in the ascending aorta and flow velocity recordings in the left ventricular outflow tract by echocardiography. Objective functional improvement 6 months after TAVI was assessed through changes in a 6-min walk test and NT-proBNP levels. A clinical follow-up was conducted at 2 years. Results: Of the 102 patients studied, 82 (80.4%) showed objective functional improvement. The 2-year mortality of these patients was significantly lower (9% vs. 44%, p = 0.001). In multivariate analysis, parameter "(Pressure at Vmax - Pressure at Vo)/Vmax" was found to be an independent predictor for objective improvement. The C-statistic was 0.70 in the overall population and 0.78 in the low-gradient subgroup. All echocardiographic parameters and the valvuloarterial impedance showed a C-statistic of <0.6 for the overall and low-gradient patients. In a validation cohort of 119 patients, the C-statistic was 0.67 for the total cohort and 0.76 for the low-gradient subgroup. Conclusion: This new method allows predicting objective functional improvement after TAVI more precisely than the conventional parameters used to assess the severity of aortic stenosis, particularly in low-gradient patients.

Intraprocedural delayed reassessment of paravalvular regurgitation in TAVR significantly reduces the use of postdilatation.

OBJECTIVES: We sought to investigate the effect of a 15-min delayed intraprocedural reassessment of paravalvular aortic regurgitation (PVR) after an immediate evaluation of posttranscatheter aortic valve replacement (TAVR) on the regurgitation grading and usage of postdilatation. BACKGROUND: PVR after TAVR is associated with poor prognosis, but postdilatation may increase the risk of other complications. METHODS: In a prospective cohort of consecutive patients treated with balloon-expandable valve ES-3 ultra, the degree of PVR was assessed immediately and 15 min after that first evaluation (excluded severe cases), with the indication of postdilatation based on the delayed assessment. As a control group, the previous consecutive series of patients also treated with the same model of valve prosthesis was used. RESULTS: A total of 180 patients were included in the prospective study cohort and 152 in the retrospective control group. In the study group, the immediate PVR assessment showed none-trace 27.5%, mild 52%, moderate 19%, and severe 1.5%, and the delayed re-evaluation graded PVR as none-trace 83%, mild 15.6%, and moderate 1.2% (p < 0.001 as compared to immediate). In the control group, the immediate PVR assessment showed none-trace 33.5%, mild 52%, moderate 13%, and severe 1.5%. The rate of postdilatation was 2.8% in the study group versus 10.5% in the control group (p = 0.006). At discharge, no differences were observed between groups in PVR echocardiographic grading. CONCLUSIONS: A post-TAVR delayed intraprocedural reassessment of the PVR shows a clearly lower degree of regurgitation as compared to immediate evaluation, which significantly decreased the indication of postdilatation.

A new integrative approach to assess aortic stenosis burden and predict objective functional improvement after TAVR.

Background: A non-negligible rate of patients undergoing transcatheter aortic valve replacement (TAVR) do not report symptomatic improvement or even die in the short-midterm. We sought to assess the degree of objective functional recovery after TAVR and its prognostic implications and to develop a predictive model. Methods: In a cohort of patients undergoing TAVR, a prospective evaluation of clinical, anatomical, and physiological parameters was conducted before and after the procedure. These parameters were derived from echocardiography, non-invasive analysis of arterial pulse waves, and cardiac tomography. Objective functional improvement 6 months after TAVR was assessed using a 6-min walk test and nitro-terminal pro-brain natriuretic peptide (NT-proBNP) levels. The derived predictive model was prospectively validated in a different cohort. A clinical follow-up was conducted at 2 years. Results: Among the 212 patients included, objective functional improvement was observed in 169 patients (80%) and subjective improvement in 187 (88%). Patients with objective functional improvement showed a much lower death rate at 2 years (9% vs. 31% p = 0.0002). Independent predictors of improvement were as follows: mean aortic gradient of ≥40 mmHg, augmentation index75 of ≥45%, the posterior wall thickness of ≤12 mm, and absence of atrial fibrillation. A simple integer-based point score was developed (GAPA score), which showed an area under the curve of 0.81 for the overall cohort and 0.78 for the low-gradient subgroup. In a validation cohort of 216 patients, these values were 0.75 and 0.76, respectively. Conclusion: A total of 80% of patients experienced objective functional improvement after TAVR, showing a significantly lower 2-year mortality rate. A predictive score was built that showed a good discriminative performance in overall and low-gradient populations.

Pro-apoptotic signaling induced by Retinoic acid and dsRNA is under the control of Interferon Regulatory Factor-3 in breast cancer cells.

Breast cancer is one of the most lethal malignancies for women. Retinoic acid (RA) and double-stranded RNA (dsRNA) are considered signaling molecules with potential anticancer activity. RA, co-administered with the dsRNA mimic polyinosinic-polycytidylic acid (poly(I:C)), synergizes to induce a TRAIL (Tumor-Necrosis-Factor Related Apoptosis-Inducing Ligand)- dependent apoptotic program in breast cancer cells. Here, we report that RA/poly(I:C) co-treatment, synergically, induce the activation of Interferon Regulatory Factor-3 (IRF3) in breast cancer cells. IRF3 activation is mediated by a member of the pathogen recognition receptors, Toll-like receptor-3 (TLR3), since its depletion abrogates IRF3 activation by RA/poly(I:C) co-treatment. Besides induction of TRAIL, apoptosis induced by RA/poly(I:C) correlates with the increased expression of pro-apoptotic TRAIL receptors, TRAIL-R1/2, and the inhibition of the antagonistic receptors TRAIL-R3/4. IRF3 plays an important role in RA/poly(I:C)-induced apoptosis since IRF3 depletion suppresses caspase-8 and caspase-3 activation, TRAIL expression upregulation and apoptosis. Interestingly, RA/poly(I:C) combination synergizes to induce a bioactive autocrine/paracrine loop of type-I Interferons (IFNs) which is ultimately responsible for TRAIL and TRAIL-R1/2 expression upregulation, while inhibition of TRAIL-R3/4 expression is type-I IFN-independent. Our results highlight the importance of IRF3 and type-I IFNs signaling for the pro-apoptotic effects induced by RA and synthetic dsRNA in breast cancer cells.

Anterograde transport and secretion of brain-derived neurotrophic factor along sensory axons promote Schwann cell myelination.

The neurotrophin brain-derived neurotrophic factor (BDNF) inhibits Schwann cell (SC) migration and promotes myelination via the p75 neurotrophin receptor (NTR). Despite these recent findings, the expression, localization, and mechanism of BDNF action has yet to be determined. Here we demonstrate that the sensory neurons of the dorsal root ganglion (DRG) are a major source of BDNF during postnatal development. The expression of BDNF is initially elevated before myelination and decreases dramatically after the onset of myelination. BDNF expression is controlled in part by transcriptional regulation and the increased expression of the truncated TrkB receptor on SCs. To investigate the possible mechanism of BDNF transport and release, multicompartment Campenot chambers were used. DRG neurons transported and secreted endogenous BDNF along the surface of axons in anterograde fashion. In an attempt to enhance myelination by SCs, DRG neurons were transduced with an adenovirus to overexpress BDNF. BDNF was transported and secreted along the axons and enhanced myelination when compared with control cocultures. Together, the events surrounding the expression, localization, and mechanism of BDNF action in DRG neurons may hint at potential therapeutic implications to efficiently promote remyelination.

Differential endocytic sorting of p75NTR and TrkA in response to NGF: a role for late endosomes in TrkA trafficking.

NGF binds to two receptors, p75NTR and TrkA. The endosomal trafficking of receptors is of emerging importance for the understanding of their signaling. We compared the endocytic trafficking of the two NGF receptors in PC12 cells. Both p75NTR and TrkA were internalized in response to NGF and colocalized with early endosomes. However, surprisingly, the subsequent endosomal trafficking paths of both NGF receptors diverged: whereas p75NTR recycled back to the surface, TrkA moved to late endosomes and underwent lysosomal degradation. By performing subcellular fractionations of NGF stimulated PC12 cells, tyrosine-phosphorylated TrkA was recovered in fractions corresponding to late endosomes. This implicates these organelles as novel endosomal NGF signaling platforms. Furthermore, the trafficking of NGF receptors could be manipulated by pharmacological means. Disrupting p75NTR recycling diminished TrkA activation in response to low concentrations of NGF, demonstrating a functional role for the recycling of p75NTR.

BDNF overexpression produces a long-term increase in myelin formation in the peripheral nervous system.

The neurotrophin brain-derived neurotrophic factor (BDNF) is an endogenous regulator of the myelination process during development in the peripheral nervous system. Enhancement of myelin formation by BDNF is mediated by the neurotrophin receptor p75(NTR). Although this neurotrophin is a positive modulator of myelination during early development, the final effects of BDNF on myelin sheaths after active myelination is completed are largely unknown. Using BDNF transgenic mice, we examined the long-term effects of BDNF on myelination of the peripheral nervous system in vivo. Elevation of BDNF levels in the transgenic mice produced an increase in both the rate and extent of the myelination process. BDNF enhanced and accelerated myelin formation during early development and this increase in myelin content and thickness was maintained in adulthood. Besides enhanced myelination, BDNF also influenced axon caliber size but to a lesser extent. This lagging increase in axon caliber compared to myelin suggests that the axon size is not the only determinant of myelin thickness.

NGF controls axonal receptivity to myelination by Schwann cells or oligodendrocytes.

Axons dictate whether or not they will become myelinated in both the central and peripheral nervous systems by providing signals that direct the development of myelinating glia. Here we identify the neurotrophin nerve growth factor (NGF) as a potent regulator of the axonal signals that control myelination of TrkA-expressing dorsal root ganglion neurons (DRGs). Unexpectedly, these NGF-regulated axonal signals have opposite effects on peripheral and central myelination, promoting myelination by Schwann cells but reducing myelination by oligodendrocytes. These findings indicate a novel role for growth factors in regulating the receptivity of axons to myelination and reveal that different axonal signals control central and peripheral myelination.

Differences in the surface binding and endocytosis of neurotrophins by p75NTR.

Neurotrophins transmit signals retrogradely from synapses to cell bodies by two different types of surface receptors, p75NTR and Trks. Compared to TrkA, the function of p75NTR in nerve growth factor (NGF) endocytosis is less clear, and it is unknown whether p75NTR by itself may internalize other neurotrophins besides NGF. We directly compared TrkA and p75NTR for their ability to internalize NGF, and we also examined the endocytosis of iodinated brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT3) by p75NTR. Cells expressing solely TrkA internalized NGF more efficiently than cells expressing p75NTR. Surprisingly, cells expressing only p75NTR internalized far more BDNF or NT3 than NGF. Moreover, p75NTR was more important for surface binding than for intracellular accumulation of each neurotrophin. Finally, we established a mechanistic role for the clathrin pathway in p75NTR endocytosis. Our results suggest that p75NTR may have multiple roles in different subcellular locations, functioning both at the cell surface and also within endocytic compartments.

The neurotrophin receptor p75NTR as a positive modulator of myelination.

Schwann cells in developing and regenerating peripheral nerves express elevated levels of the neurotrophin receptor p75NTR. Neurotrophins are key mediators of peripheral nervous system myelination. Our results show that myelin formation is inhibited in the absence of functional p75NTR and enhanced by blocking TrkC activity. Moreover, the enhancement of myelin formation by endogenous brain-derived neurotrophic factor is mediated by the p75NTR receptor, whereas TrkC receptors are responsible for neurotrophin-3 inhibition. Thus p75NTR and TrkC receptors have opposite effects on myelination.