Allelic Complexity in Long QT Syndrome: A Family-Case Study.

Congenital long QT syndrome (LQTS) is associated with high genetic and allelic heterogeneity. In some cases, more than one genetic variant is identified in the same (compound heterozygosity) or different (digenic heterozygosity) genes, and subjects with multiple pathogenic mutations may have a more severe disease. Standard-of-care clinical genetic testing for this and other arrhythmia susceptibility syndromes improves the identification of complex genotypes. Therefore, it is important to distinguish between pathogenic mutations and benign rare variants. We identified four genetic variants (KCNQ1-p.R583H, KCNH2-p.C108Y, KCNH2-p.K897T, and KCNE1-p.G38S) in an LQTS family. On the basis of in silico analysis, clinical data from our family, and the evidence from previous studies, we analyzed two mutated channels, KCNQ1-p.R583H and KCNH2-p.C108Y, using the whole-cell patch clamp technique. We found that KCNQ1-p.R583H was not associated with a severe functional impairment, whereas KCNH2-p.C108Y, a novel variant, encoded a non-functional channel that exerts dominant-negative effects on the wild-type. Notably, the common variants KCNH2-p.K897T and KCNE1-p.G38S were previously reported to produce more severe phenotypes when combined with disease-causing alleles. Our results indicate that the novel KCNH2-C108Y variant can be a pathogenic LQTS mutation, whereas KCNQ1-p.R583H, KCNH2-p.K897T, and KCNE1-p.G38S could be LQTS modifiers.

The multi-faceted aspects of the complex cardiac Nav1.5 protein in membrane function and pathophysiology.

The aim of this mini-review is to draw together the main concepts and findings that have emerged from recent studies of the cardiac channel protein Nav1.5. This complex protein is encoded by the SCN5A gene that, in its mutated form, is implicated in various diseases, particularly channelopathies, specifically at cardiac tissue level. Here we describe the structural, and functional aspects of Nav1.5 including post-translational modifications in normal conditions, and the main human channelopathies in which this protein may be the cause or trigger. Lastly, we also briefly discuss interacting proteins that are relevant for these channel functions in normal and disease conditions.

Functional characterization of novel ABCB6 mutations and their clinical implications in familial pseudohyperkalemia.

Isolated familial pseudohyperkalemia is a dominant red cell trait characterized by cold-induced 'passive leak' of red cell potassium ions into plasma. The causative gene of this condition is ABCB6, which encodes an erythrocyte membrane ABC transporter protein bearing the Langereis blood group antigen system. In this study analyzing three new families, we report the first functional characterization of ABCB6 mutants, including the homozygous mutation V454A, heterozygous mutation R276W, and compound heterozygous mutations R276W and R723Q (in trans). All these mutations are annotated in public databases, suggesting that familial pseudohyperkalemia could be common in the general population. Indeed, we identified variant R276W in one of 327 random blood donors (0.3%). Four weeks' storage of heterozygous R276W blood cells resulted in massive loss of potassium compared to that from healthy control red blood cells. Moreover, measurement of cation flux demonstrated greater loss of potassium or rubidium ions from HEK-293 cells expressing ABCB6 mutants than from cells expressing wild-type ABCB6. The R276W/R723Q mutations elicited greater cellular potassium ion efflux than did the other mutants tested. In conclusion, ABCB6 missense mutations in red blood cells from subjects with familial pseudohyperkalemia show elevated potassium ion efflux. The prevalence of such individuals in the blood donor population is moderate. The fact that storage of blood from these subjects leads to significantly increased levels of potassium in the plasma could have serious clinical implications for neonates and infants receiving large-volume transfusions of whole blood. Genetic tests for familial pseudohyperkalemia could be added to blood donor pre-screening. Further study of ABCB6 function and trafficking could be informative for the study of other pathologies of red blood cell hydration.

Functional Studies and In Silico Analyses to Evaluate Non-Coding Variants in Inherited Cardiomyopathies.

Point mutations are the most common cause of inherited diseases. Bioinformatics tools can help to predict the pathogenicity of mutations found during genetic screening, but they may work less well in determining the effect of point mutations in non-coding regions. In silico analysis of intronic variants can reveal their impact on the splicing process, but the consequence of a given substitution is generally not predictable. The aim of this study was to functionally test five intronic variants (MYBPC3-c.506-2A>C, MYBPC3-c.906-7G>T, MYBPC3-c.2308+3G>C, SCN5A-c.393-5C>A, and ACTC1-c.617-7T>C) found in five patients affected by inherited cardiomyopathies in the attempt to verify their pathogenic role. Analysis of the MYBPC3-c.506-2A>C mutation in mRNA from the peripheral blood of one of the patients affected by hypertrophic cardiac myopathy revealed the loss of the canonical splice site and the use of an alternative splicing site, which caused the loss of the first seven nucleotides of exon 5 (MYBPC3-G169AfsX14). In the other four patients, we generated minigene constructs and transfected them in HEK-293 cells. This minigene approach showed that MYBPC3-c.2308+3G>C and SCN5A-c.393-5C>A altered pre-mRNA processing, thus resulting in the skipping of one exon. No alterations were found in either MYBPC3-c.906-7G>T or ACTC1-c.617-7T>C. In conclusion, functional in vitro analysis of the effects of potential splicing mutations can confirm or otherwise the putative pathogenicity of non-coding mutations, and thus help to guide the patient's clinical management and improve genetic counseling in affected families.

Physiochemical Characterization of Lipidic Nanoformulations Encapsulating the Antifungal Drug Natamycin.

Natamycin is a tetraene polyene that exploits its antifungal properties by irreversibly binding components of fungal cell walls, blocking the growth of infections. However, topical ocular treatments with natamycin require frequent application due to the low ability of this molecule to permeate the ocular membrane. This limitation has limited the use of natamycin as an antimycotic drug, despite it being one of the most powerful known antimycotic agents. In this work, different lipidic nanoformulations consisting of transethosomes or lipid nanoparticles containing natamycin are proposed as carriers for optical topical administration. Size, stability and zeta potential were characterized via dynamic light scattering, the supramolecular structure was investigated via small- and wide-angle X-ray scattering and 1H-NMR, and the encapsulation efficiencies of the four proposed formulations were determined via HPLC-DAD.

Early transtympanic administration of rhBDNF exerts a multifaceted neuroprotective effect against cisplatin-induced hearing loss.

BACKGROUND AND PURPOSE: Cisplatin-induced sensorineural hearing loss is a significant clinical challenge. Although the potential effects of brain-derived neurotrophic factor (BDNF) have previously been investigated in some ototoxicity models, its efficacy in cisplatin-induced hearing loss remains uncertain. This study aimed to investigate the therapeutic potential of recombinant human BDNF (rhBDNF) in protecting cells against cisplatin-induced ototoxicity. EXPERIMENTAL APPROACH: Using an in vivo model of cisplatin-induced hearing loss, we investigated the beneficial effects of transtympanic administration of rhBDNF in a thermogel solution on hearing function and cochlear injury, using electrophysiological, morphological, immunofluorescence and molecular analyses. KEY RESULTS: Our data showed that local rhBDNF treatment counteracted hearing loss in rats receiving cisplatin by preserving synaptic connections in the cochlear epithelium and protecting hair cells (HCs) and spiral ganglion neurons (SGNs) against cisplatin-induced cell death. Specifically, rhBDNF maintains the balance of its receptor levels (pTrkB and p75), boosting TrkB-CREB pro-survival signalling and reducing caspase 3-dependent apoptosis in the cochlea. Additionally, it activates antioxidant mechanisms while inhibiting inflammation and promoting vascular repair. CONCLUSION AND IMPLICATIONS: Collectively, we demonstrated that early transtympanic treatment with rhBDNF plays a multifaceted protective role against cisplatin-induced ototoxicity, thus holding promise as a novel potential approach to preserve hearing in adult and paediatric patients undergoing cisplatin-based chemotherapy.

Adsorption of the rhNGF Protein on Polypropylene with Different Grades of Copolymerization.

The surface properties of drug containers should reduce the adsorption of the drug and avoid packaging surface/drug interactions, especially in the case of biologically-derived products. Here, we developed a multi-technique approach that combined Differential Scanning Calorimetry (DSC), Atomic Force Microscopy (AFM), Contact Angle (CA), Quartz Crystal Microbalance with Dissipation monitoring (QCM-D), and X-ray Photoemission Spectroscopy (XPS) to investigate the interactions of rhNGF on different pharma grade polymeric materials. Polypropylene (PP)/polyethylene (PE) copolymers and PP homopolymers, both as spin-coated films and injected molded samples, were evaluated for their degree of crystallinity and adsorption of protein. Our analyses showed that copolymers are characterized by a lower degree of crystallinity and lower roughness compared to PP homopolymers. In line with this, PP/PE copolymers also show higher contact angle values, indicating a lower surface wettability for the rhNGF solution on copolymers than PP homopolymers. Thus, we demonstrated that the chemical composition of the polymeric material and, in turn, its surface roughness determine the interaction with the protein and identified that copolymers may offer an advantage in terms of protein interaction/adsorption. The combined QCM-D and XPS data indicated that protein adsorption is a self-limiting process that passivates the surface after the deposition of roughly one molecular layer, preventing any further protein adsorption in the long term.

Bioengineered Human Stromal Lenticule for Recombinant Human Nerve Growth Factor Release: A Potential Biocompatible Ocular Drug Delivery System.

Small incision lenticule extraction (SMILE), is a surgical procedure for the myopia correction, during which a corneal stromal lenticule is extracted. Given that we have previously demonstrated how this discarded tissue could be repurposed as a bio-scaffold for stromal engineering, this study aimed to explore its use as an ocular drug delivery system of active molecules, using neurotrophic factor Nerve Growth Factor (NGF). We employed human stromal lenticules directly collected from healthy donors undergoing SMILE. Following a sodium dodecylsulfate (SDS) treatment, decellularized lenticules were incubated with a suspension of polylactic-co-glycolic-acid (PLGA) microparticles (MPs) loaded with recombinant human NGF (rhNGF-MPs). Fluorescent MPs (Fluo-MPs) were used as control. Data demonstrated the feasibility to engineer decellularized lenticules with PLGA-MPs which remain incorporated both on the lenticules surface and in its stromal. Following their production, the in vitro release kinetic showed a sustained release for up to 1 month of rhNGF from MPs loaded to the lenticule. Interestingly, rhNGF was rapidly released in the first 24 h, but it was sustained up to the end of the experiment (1 month), with preservation of rhNGF activity (around 80%). Our results indicated that decellularized human stromal lenticules could represent a biocompatible, non-immunogenic natural scaffold potential useful for ocular drug delivery. Therefore, combining the advantages of tissue engineering and pharmaceutical approaches, this in vitro proof-of-concept study suggests the feasibility to use this scaffold to allow target release of rhNGF in vivo or other pharmaceutically active molecules that have potential to treat ocular diseases.

Novel electrospun polyurethane/gelatin composite meshes for vascular grafts.

Novel polymeric micro-nanostructure meshes as blood vessels substitute have been developed and investigated as a potential solution to the lack of functional synthetic small diameter vascular prosthesis. A commercial elastomeric polyurethane (Tecoflex EG-80A) and a natural biopolymer (gelatin) were successfully co-electrospun from different spinnerets on a rotating mandrel to obtain composite meshes benefiting from the mechanical characteristics of the polyurethane and the natural biopolymer cytocompatibility. Morphological analysis showed a uniform integration of micrometric (Tecoflex) and nanometric (gelatin) fibers. Exposure of the composite meshes to vapors of aqueous glutaraldehyde solution was carried out, to stabilize the gelatin fibers in an aqueous environment. Uniaxial tensile testing in wet conditions demonstrated that the analyzed Tecoflex-Gelatin specimens possessed higher extensibility and lower elastic modulus than conventional synthetic grafts, providing a closer matching to native vessels. Biological evaluation highlighted that, as compared with meshes spun from Tecoflex alone, the electrospun composite constructs enhanced endothelial cells adhesion and proliferation, both in terms of cell number and morphology. Results suggest that composite Tecoflex-Gelatin meshes could be promising alternatives to conventional vascular grafts, deserving of further studies on both their mechanical behaviour and smooth muscle cell compatibility.

Melt electrospinning of poly(ε-caprolactone) scaffolds: phenomenological observations associated with collection and direct writing.

Melt electrospinning and its additive manufacturing analogue, melt electrospinning writing (MEW), are two processes which can produce porous materials for applications where solvent toxicity and accumulation in solution electrospinning are problematic. This study explores the melt electrospinning of poly(ε-caprolactone) (PCL) scaffolds, specifically for applications in tissue engineering. The research described here aims to inform researchers interested in melt electrospinning about technical aspects of the process. This includes rapid fiber characterization using glass microscope slides, allowing influential processing parameters on fiber morphology to be assessed, as well as observed fiber collection phenomena on different collector substrates. The distribution and alignment of melt electrospun PCL fibers can be controlled to a certain degree using patterned collectors to create large numbers of scaffolds with shaped macroporous architectures. However, the buildup of residual charge in the collected fibers limits the achievable thickness of the porous template through such scaffolds. One challenge identified for MEW is the ability to control charge buildup so that fibers can be placed accurately in close proximity, and in many centimeter heights. The scale and size of scaffolds produced using MEW, however, indicate that this emerging process will fill a technological niche in biofabrication.

Poly(lactic-co-glycolic acid) electrospun fibrous meshes for the controlled release of retinoic acid.

Poly(lactic-co-glycolic acid) (PLGA) meshes loaded with retinoic acid (RA) were prepared by applying the electrospinning technique. The purpose of the present work was to combine the biological effects of RA and the advantages of electrospun meshes to enhancing the mass transfer features of controlled release systems and cell interaction with polymeric scaffolds. The processing conditions for the fabrication of three-dimensional meshes were optimized by studying their influence on mesh morphology. Tensile testing showed that RA loading influenced the meshes' mechanical properties by increasing their strength and rigidity. Moreover, the drug release and degradation profiles of the electrospun systems were compared to analogous RA-loaded PLGA films prepared by solvent casting. The results of this study highlight that the electrospun meshes preserved their fibrous structure after 4 months under in vitro physiological conditions and showed a sustained controlled release of the loaded agent in comparison to that observed for cast films. The bioactivity of the loaded RA was investigated on murine preosteoblasts cells by evaluating its influence on cell proliferation and morphology.

Development of electrospun three-arm star poly(ε-caprolactone) meshes for tissue engineering applications.

We have developed three-dimensional electrospun microfibrous meshes of a novel star branched three-arm poly(ε-caprolactone) (*PCL) as potential scaffolds for tissue engineering applications. The processing conditions required to obtain uniform fibers were optimized by studying their influence on fiber morphology and size. Polymer molecular weight and solution feed rate influenced both the mesh microstructure and the tensile properties of the developed mats. Electrospun samples were also tested for their mechanical properties in wet conditions, showing higher yield strength and strain in comparison to that observed in dry conditions. Cell culture experiments employing MC3T3-E1 osteoblast like cells showed good cell viability adhesion and collagen production on the *PCL scaffolds.