The overlapping biological behaviors between some cell penetrating peptides (CPPs) and antimicrobial peptides (AMPs) suggest both common and different membrane interaction mechanisms. We thus explore the capacity of selected CPPs and AMPs to reorganize the planar distribution of binary lipid mixtures by means of differential scanning calorimetry (DSC). Additionally, membrane integrity assays and circular dichroism (CD) experiments were performed. Two CPPs (Penetratin and RL16) and AMPs belonging to the dermaseptin superfamily (Drs B2 and C-terminal truncated analog [1-23]-Drs B2 and two plasticins DRP-PBN2 and DRP-PD36KF) were selected. Herein we probed the impact of headgroup charges and acyl chain composition (length and unsaturation) on the peptide/lipid interaction by using binary lipid mixtures. All peptides were shown to be alpha-helical in all the lipid mixtures investigated, except for the two CPPs and [1-23]-Drs B2 in the presence of zwitterionic lipid mixtures where they were rather unstructured. Depending on the lipid composition and peptide sequence, simple binding to the lipid surface that occur without affecting the lipid distribution is observed in particular in the case of AMPs. Recruitments and segregation of lipids were observed, essentially for CPPs, without a clear relationship between peptide conformation and their effect in the lipid lateral organization. Nonetheless, in most cases after initial electrostatic recognition between the peptide charged amino acids and the lipid headgroups, the lipids with the lowest phase transition temperature were selectively recruited by cationic peptides while those with the highest phase transition were segregated. Membrane activities of CPPs and AMPs could be thus related to their preferential interactions with membrane defects that correspond to areas with marked fluidity. Moreover, due to the distinct membrane composition of prokaryotes and eukaryotes, lateral heterogeneity may be differently affected by cationic peptides leading to either uptake or/and antimicrobial activities.

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A fibrin scaffold loaded with ESC-derived cardiac progenitors resulted in sustained improvement in contractility and attenuation of remodeling without sustained donor cell engraftment. A paracrine effect, possibly on innate reparative responses, is a possible mechanism for this enduring effect.

Limited data are available on the effects of stem cells in non-ischemic dilated cardiomyopathy (DCM). Since the diffuse nature of the disease calls for a broad distribution of cells, this study investigated the scaffold-based delivery of human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CM) in a mouse model of DCM. Nanofibrous scaffolds were produced using a clinical grade atelocollagen which was electrospun and cross-linked under different conditions. As assessed by scanning electron microscopy and shearwave elastography, the optimum crosslinking conditions for hiPS-CM colonization proved to be a 10% concentration of citric acid crosslinking agent and 150 min of post-electrospinning baking. Acellular collagen scaffolds were first implanted in both healthy mice and those with induced DCM by a cardiac-specific invalidation of serum response factor (SRF). Seven and fourteen days after implantation, the safety of the scaffold was demonstrated by echocardiography and histological assessments. The subsequent step of implantation of the scaffolds seeded with hiPS-CM in DCM induced mice, using cell-free scaffolds as controls, revealed that after fourteen days heart function decreased in controls while it remained stable in the treated mice. This pattern was associated with an increased number of endothelial cells, in line with the greater vascularity of the scaffold. Moreover, a lesser degree of fibrosis consistent with the upregulation of several genes involved in extracellular matrix remodeling was observed. These results support the interest of the proposed hiPS-CM seeded electrospun scaffold for the stabilization of the DCM outcome with potential for its clinical use in the future.

Dystrophin contributes to force transmission and has a protein-scaffolding role for a variety of signaling complexes in skeletal muscle. In the present study, we tested the hypothesis that the muscle adaptive response following mechanical overloading (ML) would be decreased in MDX dystrophic muscle lacking dystrophin. We found that the gains in muscle maximal force production and fatigue resistance in response to ML were both reduced in MDX mice as compared to healthy mice. MDX muscle also exhibited decreased cellular and molecular muscle remodeling (hypertrophy and promotion of slower/oxidative fiber type) in response to ML, and altered intracellular signalings involved in muscle growth and maintenance (mTOR, myostatin, follistatin, AMPKα1, REDD1, atrogin-1, Bnip3). Moreover, dystrophin rescue via exon skipping restored the adaptive response to ML. Therefore our results demonstrate that the adaptive response in response to ML is impaired in dystrophic MDX muscle, most likely because of the dystrophin crucial role.

Rationale: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare disease, manifested by syncope or sudden death in children or young adults under stress conditions. Mutations in the Ca 2+ release channel/ryanodine receptor (RyR2) gene account for about 60% of the identified mutations. Recently, we found and described a mutation in RyR2 N-terminal domain, RyR2 R420Q . Objective: To determine the arrhythmogenic mechanisms of this mutation. Methods and Results: Ventricular tachycardias under stress conditions were observed in both CPVT patients and KI mice. During action potential recording (by patch-clamp in KI mouse cardiomyocytes and by microelectrodes in mutant hiPSC-CM) we observed an increased occurrence of delayed after-depolarizations (DADs) under isoproterenol stimulation, associated with increased Ca 2+ waves during confocal Ca 2+ recording in both mouse and human RyR2 R420Q cardiomyocytes. In addition, Ca 2+ -induced Ca 2+ -release, as well as a rough indicator of fractional Ca 2+ release, were higher and Ca 2+ sparks longer in the RyR2 R420Q expressing cells. At the ultrastructural nanodomain level, we observed smaller RyR2 clusters and widened junctional sarcoplasmic reticulum (jSR) measured by g-STED super-resolution and electronic microscopy, respectively. The increase in jSR width might be due to the impairment of RyR2 R420Q binding to junctophilin-2, as there were less junctophilin-2 co-immunoprecipitated with RyR2 R420Q . At the single current level, the RyR2R420Q channel dwells longer in the open state at low [Ca 2+ ] i , but there is predominance of a subconductance state. The latter might be correlated with an enhanced interaction between the N-terminus and the core solenoid, a RyR2 inter-domain association that has not been previously implicated in the pathogenesis of arrhythmias and sudden cardiac death. Conclusions: The RyR2 R420Q CPVT mutation modifies the interdomain interaction of the channel and weaken its association with junctophillin-2. These defects may underlie both nanoscale disarrangement of the dyad and channel dysfunction.

These results strongly suggest the functional relevance of epicardially delivered cell-seeded biomaterials to non-ischaemic heart failure.

International audienceSynergy between micro-nanotechnology and regenerative medicine can lead to new tools for health improvement. In this study, we investigate the efficacy of electrospun scaffolds-fabricated using clinically approved collagen – as supports for cardiomyoblast culture. The scaffolds were prepared using non-toxic solvents and crosslinking agents and characterized by scanning electron microscopy and contact angle measurements. Among different types of collagen samples, we found that atelocollagen can produce better quality of electrospun fibers than acid and basic fibrous collagen. Our results also show that the cell culture performance can be improved by adjusting the crosslinking conditions. Typically, increasing the concentration of citric acid of the cross-link agents from 5% to 10% w/w and the post-crosslink baking time from 1.5 to 2.5 h led to significant increases of the cellular colonization of the scaffold, showing three-dimensional growth of cardiac cells due to the specific morphology of the fibrous scaffolds. Finally, in vivo tests of the biocompatibility of the fabricated scaffolds have been done using a mouse model of dilated cardiomyopathy. As expected, the biocompatibility of the scaffold was found excellent and no visible inflammation was observed after the implantation up to two weeks. However, 5% citric acid electrospun collagen scaffolds was less resistant in vivo, proving again the importance of the processing parameter optimization of the electrospun scaffolds