Calcification of surgical aortic bioprostheses and its impact on clinical outcome

AIMS

Aortic valve calcification (AVC) of surgical valve bioprostheses (BP) has been poorly explored. We aimed to evaluate in-vivo and ex-vivo BP AVC and its prognosis value.

METHODS AND RESULTS

Between 2011 and 2019, AVC was assessed using in-vivo computed tomography (CT) in 361 patients who had undergone surgical valve replacement 6.4±4.3 years earlier. Ex-vivo CT scans were performed for 37 explanted BP. The in-vivo CT scans were interpretable for 342 patients (19 patients [5.2%], were excluded). These patients were 77.2±9.1 years old and 64.3% were male. Mean in-vivo AVC was 307±500 Agatston unit (AU). The AVC was 562±570 AU for the 183 (53.5%) patients with structural valve degeneration (SVD) and 13±43 AU for those without SVD (p<0.0001). In-vivo and ex-vivo AVC were strongly correlated (r=0.88, p<0.0001). An in-vivo AVC>100 AU (n=147, 43%) had a specificity of 96% for diagnosing Stage 2-3 SVD (area under the curve=0.92). Patients with AVC>100 AU had a worse outcome compared with those with AVC≤100 AU (n=195). In multivariable analysis, AVC was a predictor of overall mortality (hazard ratio [HR] and 95% confidence interval=1.16[1.04-1.29]; p=0.006), cardiovascular mortality (HR=1.22[1.04-1.43]; p=0.013), cardiovascular events (HR=1.28 [1.16-1.41]; p<0.0001), and re-intervention (HR=1.15 [1.06-1.25]; p<0.0001). After adjustment for Stage 2-3 SVD diagnosis, AVC remained a predictor of overall mortality (HR=1.20 [1.04-1.39]; p=0.015) and cardiovascular events (HR=1.25 [1.09-1.43]; p=0.001).

CONCLUSION

CT scan is a reliable tool to assess BP leaflet calcification. An AVC>100 AU is tightly associated with SVD and it is a strong predictor of overall mortality and cardiovascular events.

Calcium Phosphate Cements Combined with Blood as a Promising Tool for the Treatment of Bone Marrow Lesions

The solid phase of a commercial calcium phosphate (Graftys^® HBS) was combined with ovine or human blood stabilized either with sodium citrate or sodium heparin. The presence of blood delayed the setting reaction of the cement by ca. 7-15 h, depending on the nature of the blood and blood stabilizer. This phenomenon was found to be directly related to the particle size of the HBS solid phase, since prolonged grinding of the latter resulted in a shortened setting time (10-30 min). Even though ca. 10 h were necessary for the HBS blood composite to harden, its cohesion right after injection was improved when compared to the HBS reference as well as its injectability. A fibrin-based material was gradually formed in the HBS blood composite to end-up, after ca. 100 h, with a dense 3D organic network present in the intergranular space, thus affecting the microstructure of the composite. Indeed, SEM analyses of polished cross-sections showed areas of low mineral density (over 10-20 µm) spread in the whole volume of the HBS blood composite. Most importantly, when the two cement formulations were injected in the tibial subchondral cancellous bone in a bone marrow lesion ovine model, quantitative SEM analyses showed a highly significant difference between the HBS reference versus its analogue combined with blood. After a 4-month implantation, histological analyses clearly showed that the HBS blood composite underwent high resorption (remaining cement: ca. 13.1 ± 7.3%) and new bone formation (newly formed bone: 41.8 ± 14.7%). This was in sharp contrast with the case of the HBS reference for which a low resorption rate was observed (remaining cement: 79.0 ± 6.9%; newly formed bone: 8.6 ± 4.8%). This study suggested that the particular microstructure, induced by the use of blood as the HBS liquid phase, favored quicker colonization of the implant and acceleration of its replacement by newly formed bone. For this reason, the HBS blood composite might be worth considering as a potentially suitable material for subchondroplasty.

Micromolding-based encapsulation of mesenchymal stromal cells in alginate for intraarticular injection in osteoarthritis

Osteoarthritis (OA) is an inflammatory joint disease that affects cartilage, subchondral bone, and joint tissues. Undifferentiated Mesenchymal Stromal Cells are a promising therapeutic option for OA due to their ability to release anti-inflammatory, immuno-modulatory, and pro-regenerative factors. They can be embedded in hydrogels to prevent their tissue engraftment and subsequent differentiation. In this study, human adipose stromal cells are successfully encapsulated in alginate microgels via a micromolding method. Microencapsulated cells retain their in vitro metabolic activity and bioactivity and can sense and respond to inflammatory stimuli, including synovial fluids from OA patients. After intra-articular injection in a rabbit model of post-traumatic OA, a single dose of microencapsulated human cells exhibit properties matching those of non-encapsulated cells. At 6 and 12 weeks post-injection, we evidenced a tendency toward a decreased OA severity, an increased expression of aggrecan, and a reduced expression of aggrecanase-generated catabolic neoepitope. Thus, these findings establish the feasibility, safety, and efficacy of injecting cells encapsulated in microgels, opening the door to a long-term follow-up in canine OA patients.

Functional, structural and molecular characterization of a new mitral valve prolapse animal model: the FLNA-P637Q KI rat

Introduction

Mitral Valve Prolapse (MVP) affects 3% of the population and is characterized by a heterogeneous mitral leaflet remodeling. The pathophysiological mechanisms involved in MVP development are not fully understood, the only therapeutic option remains the surgical valve replacement. We previously identified FLNA as the first gene causing MVP and recently generated a unique knock-in rat model for the FLNA-P637Q mutation that now paves the road to study the molecular mechanisms involved in MVP development.

Purpose

The aim of our study was to characterize the morphological, functional and molecular expression of the valvular disease in our unique KI rat model.

Methods

5 wild-type (WT) and 10 KI rats were evaluated at 3, 6 and 13 weeks. Comprehensive 2D echocardiography was performed to determine valve function and morphology. 3D quantitative analysis of the mitral valve (MV) remodelling was done using micro computed tomography (microCT). MV tissue composition was analysed based on histological and immunohistochemistry. Transcriptomic comparison was performed using RNA-sequencing approach.

Results

Based on the qualitative echocardiographic assessment of the valve, a high genotype-phenotype concordance was established for WT and KI animals (100%, 93% and 100% matching for each time points). The anterior leaflet was longer in KI comparatively to WT rats (+12 to +14% increase at all time points (p&lt;0.01)). Increased lengths corroborated the increased leaflets volume assessed by microCT analysis (+20 to +58% in KI compared to WT all time points (p&lt;0.05)). Histological and immunohistological analyses (leaflet's thickening, hypercellularity, proteoglycans accumulation without calcification) pointed out towards a myxomatous valve disease. The differential gene expression profile established by RNAseq analysis revealed that inflammation, epithelial cell migration or mechanical transduction pathways were specifically activated in KI valves. Genes such as Itgb2 (+1.30x), Ccl12 (+2.44x), Ccl2 (+1.79x), Ccl28 (+1.53x), Ccl7 (+2.95x), S100a8 (+8.40x) or S100a9 (+2.67x) were significantly upregulated in the GO:0060326 “cell chemotaxis”, p=2.31x10–5. In the GO:0043542 “endothelial cell migration”, p=1.59x10–6, Klf4 (+1.31x) and Tgfbr1 (+1.21x) were upregulated. Genes part of the GO:0048771 “tissue remodelling” (p=5.52x10–5) were also found upregulated.

Conclusion

These results establish that our unique KI FLNA-P637Q rat develops a myxomatous MV dystrophy comparable to the one described in MVP patients and thus constitutes a pertinent model to study the pathophysiological molecular mechanisms associated with MVP development. Our results point to molecular pathways including inflammation and epithelial activation, which constitute potential therapeutic targets.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Connect Talent

Standardized fractal bench test evaluation of coronary stents: Performances in bifurcation lesions treated by the re-proximal optimization technique

BACKGROUND

Bifurcation lesions in coronary arteries are complex to treat with coronary stents, which are not designed for that purpose and can be unproperly deployed. Moreover, devices are constantly evolving, and so are angioplasty techniques.

OBJECTIVES

The aim of this study was to determine the performances of different stents in the treatment of bifurcation lesions using the re-proximal optimization technique (rePOT).

METHODS

Eleven stent platforms were evaluated: Xience Sierra (Abbott), Xience Alpine (Abbott), Synergy (Boston), Coroflex Isar (Bbraun), Cobra PzF (Celonova), Ultimaster (Terumo), Resolute Integrity (Medtronic), Resolute Onyx (Medtronic), Optimax (Hexacath), Orsiro (Biotronik), and Absorb (Abbott). Stents were deployed in a silicone fractal bifurcation model using the rePOT. Micro-computed tomography was performed to assess side branch ostium coverage and strut malapposition, as well as the effect of rePOT on stent cell area.

RESULTS

Our study showed significant differences between stent platforms regarding side branch ostium coverage (p = .002). The Synergy and Cobra PzF stents were the most performant devices to avoid ostium coverage. Strut malapposition varied significantly between devices (p = .008) but the percentage of malapposed struts was relatively low. Significant differences were observed between stents regarding the cell area before (p = .002) and also after rePOT (p = .003), and the increase in cell area caused by rePOT varied considerably between devices (p = .08).

CONCLUSION

This study highlighted significant differences in the performances of stent platforms deployed in a fractal bifurcation model using rePOT, with a variable impact of the procedure on stent cell area.

An Fgfr3-activating mutation in immature murine osteoblasts affects the appendicular and craniofacial skeleton

Achondroplasia (ACH), the most common form of dwarfism, is caused by a missense mutation in the gene coding for fibroblast growth factor receptor 3 (FGFR3). The resulting increase in FGFR3 signaling perturbs the proliferation and differentiation of chondrocytes (CCs), alters the process of endochondral ossification and thus reduces bone elongation. Increased FGFR3 signaling in osteoblasts (OBs) might also contribute to bone anomalies in ACH. In the present study of a mouse model of ACH, we sought to determine whether FGFR3 overactivation in OBs leads to bone modifications. The model carries an Fgfr3-activating mutation (Fgfr3Y367C/+) that accurately mimics ACH; we targeted the mutation to either immature OBs and hypertrophic CCs or to mature OBs by using the Osx-cre and collagen 1α1 (2.3 kb Col1a1)-cre mouse strains, respectively. We observed that Fgfr3 activation in immature OBs and hypertrophic CCs (Osx-Fgfr3) not only perturbed the hypertrophic cells of the growth plate (thus affecting long bone growth) but also led to osteopenia and low cortical thickness in long bones in adult (3-month-old) mice but not growing (3-week-old) mice. Importantly, craniofacial membranous bone defects were present in the adult mice. In contrast, activation of Fgfr3 in mature OBs (Col1-Fgfr3) had very limited effects on skeletal shape, size and micro-architecture. In vitro, we observed that Fgfr3 activation in immature OBs was associated with low mineralization activity. In conclusion, immature OBs appear to be affected by Fgfr3 overactivation, which might contribute to the bone modifications observed in ACH independently of CCs.

Bioactivity of Biphasic Calcium Phosphate Granules, the Control of a Needle-Like Apatite Layer Formation for Further Medical Device Developments

Biphasic calcium phosphate (BCP) bioceramics (hydroxyapatite/tricalcium phosphate, or HA/TCP) for tissue engineering and drug delivery systems is a unique know-how. A mechanical mixture of HA and TCP does not lead to such bioactive ceramics. The wet elaboration conditions of calcium-deficient apatite (CDA) or CDHA, followed by sintering, converts it into TCP and HA. The dissolution precipitation of nano-sized needle-like crystals at the surface of BCP occurs on time at body temperature. Combining several technics of characterization [scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive x-ray spectroscopy (EDX), Brunauer-Emmett-Teller method (BET), chemical analysis, x-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR)], we demonstrated an evolution on time of the HA/β-TCP. The current paper describes the crystallographic evolution of initial β-TCP rhombohedral crystallographic structure to microsized needle-like layer corresponding to apatitic TCP form. This phenomenon leads to an increase of the HA/TCP ratio, since hexagonal apatitic TCP is similar to hexagonal HA. However, the Ca/P ratio (reflecting the chemical composition HA/TCP) remains unchanged. Thus, the high reactivity of BCP involves dynamic evolution from rhombohedral to hexagonal structure, but not a chemical change. The dynamic process is reversible by calcination. These events are absolutely necessary for smart scaffolds in bone regeneration and orthobiology.

P3697A reappraisal of bioprosthetic aortic valve failure related to structural valve degeneration

Background

Structural valve degeneration (SVD) remains a major complication of aortic bioprostheses.

Purpose

We aimed to assess the mode of SVD leading to bioprosthetic aortic valve failure (BVF) in a large series of patients.

Methods

Between 2010 and 2017, we prospectively enrolled 261 consecutive patients with BVF related to SVD. All patients underwent a clinical work-up. Explanted bioprostheses were analysed for assessing the mechanism of SVD.

Results

The delay from surgery to SVD diagnosis was 8.5±3.3 (1.7 to 21.4) years, 10 years after exclusion of a specific type of bioprosthesis. Of the 261 SVD patients, 150 (57%) had mainly a stenotic type, and 111 (43%) a regurgitant type. In regurgitant SVD bioprosthesis was more frequently porcine (19 vs 7%, P=0.002), prosthesis diameter was larger (23.2±2.5 vs 21.6±1.9 mm; P<0.0001), severe mismatch was less frequent (6 vs 17%, P=0.005), cardiovascular risk factors and especially diabetes, obesity and hypertension were less frequent, patients were more often in NYHA class 3–4 (64 vs 49%; p=0.015), Nt-pro BNP was significantly higher (P<0.0001), and diuretic treatment was more frequent (73 vs 61%, P=0.04). Bioprostheses were explanted during redo surgery in 112 (43%) patients. Of these 112 bioprostheses, moderate to severe calcifications were present in 94 (83.9%) and was the main cause of either stenotic (n=64, 57.1%) or regurgitant SVD. A cusp tear (n=46) accounted for 41.1% of the explanted SVD. A perforation, a recent thrombus or a delamination process were occasionally identified. Structural degeneration developed with minimal calcification in 18 (16.1%) bioprostheses.

Conclusion

Structural valve degeneration remains a matter of concern in current practice with a mean delay of 8 to 10 years after surgery. Beside classical SVD with extensive calcification process other types of SVD can be observed with minimal calcification.

Serial evolution of TCR beta chain transcript mobilization in HIV type-1-infected patients following vaccine immune stimulation and HAART interruption

In this article, we studied the T cell receptor (TCR)beta chain transcript mobilization in peripheral blood lymphocytes harvested from HIV-1-infected patients before and after vaccination with a mixture of six lipopeptides and at the moment and serially after highly active antiretroviral therapy (HAART) interruption. This study was performed by using a combined qualitative and quantitative assessment of Vbeta mRNA alterations at the level of complementary determining region 3 length distribution (CDR3-LD) of the TCR. Whereas healthy individuals displayed both stable CDR3-LD profiles and Vbeta transcript accumulations over time, the four HIV-1-infected patients in a quiescent disease phase under HAART have a highly significantly biased CDR3-LD. In addition, they displayed a significant further increase of alterations of their beta CDR3-LD profile after vaccination and both a more altered CDR3-LD (p < 0.05) and an increased transcript accumulation of some Vbeta families after HAART interruption. These modifications mostly concerned the CD8(+ve) T cells. Such a global approach of TCR alterations may help to follow the immune response of these patients and allow targeting of more complex in vivo studies by identifying the T cells with a selected repertoire.

Analysis of brain biocompatibility of drug-releasing biodegradable microspheres by scanning and transmission electron microscopy

OBJECT

Stereotactically guided implantation of biodegradable microspheres is a promising strategy for delivery of neurotrophic factors in a precise and spatially defined brain area. The goal in this study was to show the biocompatibility of poly(D,L,lactide-co-glycolide) microspheres with brain tissue at the ultrastructural level and to analyze the three-dimensional (3D) ultrastructure after intrastriatal implantation of these microparticles.

METHODS

Scanning and transmission electron microscopy were used to study the microspheres and their environment after implantation in an inert material (gelatin) and in the rat striatum. Observations were made at different time periods, ranging from 24 hours to 2 months postimplantation.

CONCLUSIONS

The progressive degradation of the microspheres, with vacuolization, deformation, and shrinkage, was well visualized. This degradation was identical in microspheres implanted in the inert material and in the rat brain tissue, independent of the presence of macrophages. The studies preformed in the striatum permitted the authors to demonstrate the structural integrity of axons in contact with microspheres, confirming the biocompatibility of the polymer. Furthermore, scanning electron microscopy showed the preservation of the 3D ultrastructure of the striatum around the microparticles. These microparticles, which can be stereotactically implanted in functional areas of the brain and can release neurotrophic factors, could represent, for some indications, an alternative to gene therapy.

Signaling of type II oncostatin M receptor

Oncostatin M (OSM) mediates its bioactivities through two different heterodimer receptors. They both involve the gp130-transducing receptor, which dimerizes with either leukemia inhibitory receptor beta or with OSM receptor beta (OSMRbeta) to generate, respectively, type I and type II OSM receptors. Co-precipitation of gp130-associated proteins, flow cytometry, polymerase chain reaction, and tyrosine phosphorylation analyses allowed the characterization of both types of OSM receptors expressed on the surface of different cell lines. It also allowed the detection of a large size protein, p250, that specifically associates to the type II OSM receptor components and that is tyrosine-phosphorylated after the activation peak of the gp130.OSMRbeta heterocomplex. The restricted expression of type I OSM receptor by the JAR choriocarcinoma cell line, and type II receptor by the A375 melanoma cell line, permitted the characterization of their signaling machineries. Both type I and type II OSM receptors activated Jak1, Jak2, and Tyk2 receptor-associated tyrosine kinases. The information is next relayed to the nucleus by the STAT3 transcriptional activator, which is recruited by both types of OSM receptors. In addition, STAT5b was specifically activated through the gp130.OSMRbeta type II heterocomplex. The signaling pathway differences observed between the common type I LIF/OSM receptor and the specific type II OSM receptor might explain some of the bioactivities specifically displayed by OSM.