Long-term delivery of brain-derived neurotrophic factor (BDNF) from nanoporous silica nanoparticles improves the survival of spiral ganglion neurons in vitro

Gene therapy for hearing loss: Current status and future prospects of non-viral vector delivery systems

Current therapeutic options for hearing loss rely on hearing aids, ossiculoplasty or cochlear implants. These devices have limitations, particularly in noisy acoustic environments. Therefore, interest in exploring aetiological treatments to improve not only auditory perception but also the quality of life of those affected is increasing. Gene therapy is a promising aetiological treatment that can fully restore auditory function. The success of gene therapy relies on the efficient delivery of therapeutic genes or genetic modifications to the cells of the inner ear that are designed to repair or replace defective genes and restore normal hearing function. Two main strategies for gene therapy involve the use of recombinant viral vectors and nonviral delivery vehicles. Owing to their excellent diffusion properties and compatibility with sensory cells, recombinant viral vectors, particularly adeno-associated viruses (AAVs), have dominated gene therapy in the cochlea. However, recombinant viral vectors have several drawbacks, such as limited transgene size, immunogenicity (particularly in neonates), and potential need for repeat administration. Nonviral vectors, such as cationic lipids and polymeric nanoparticles, are potential attractive alternatives. Nonviral vectors have several advantages, including low immunogenicity and unlimited transgene size. Recent studies have demonstrated significant auditory recovery in vivo using nonviral vectors in murine models. However, nonviral vectors are not as efficient as viral vectors in transferring genetic material. An alternative to nanoparticles is the use of other methods, such as electroporation. The main advantage of electroporation is that it can be used in combination with cochlear implantation and can target surface cells, but this method has a risk of cell damage. The goal of this review is to provide valuable insights into the current state of research on nonviral vectors for inner ear gene therapy and propose the exploration of innovative and effective gene therapy strategies for the treatment of hearing loss.

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.

Biomaterials as a new option for treating sensorineural hearing loss

Sensorineural hearing loss (SNHL) usually involves damage to complex auditory pathways such as inner ear cells and auditory nerves. The highly intricate and nuanced characteristics of these cells render their repair and regeneration extremely challenging, making it difficult to restore hearing to normal levels once it has been compromised. The effectiveness of traditional drugs is so minimal that they provide little help with the treatment. Fortunately, extensive experiments have demonstrated that combining biomaterials with conventional techniques significantly enhances drug effectiveness. This article reviews the research progress of biomaterials in protecting hair cells and the auditory nerve, repairing genes related to hearing, and developing artificial cochlear materials. By organizing the knowledge presented in this article, perhaps new insights can be provided for the clinical management of SNHL.

Exposure of quantum dots in the nervous system: Central nervous system risks and the blood-brain barrier interface

Quantum dots currently possess significant importance in the field of biomedical science. Upon introduction into the body, quantum dots exhibit a tendency to accumulate in diverse tissues including the central nervous system (CNS). Consequently, it becomes imperative to devote specific attention to their potential toxic effects. Moreover, the preservation of optimal CNS function relies heavily on blood-brain barrier (BBB) integrity, thereby necessitating its prioritization in neurotoxicological investigations. A more comprehensive understanding of the BBB and CNS characteristics, along with the underlying mechanisms that may contribute to neurotoxicity, will greatly aid researchers in the development of effective design strategies. This article offers an in-depth look at the methods used to reduce the harmful effects of quantum dots on the nervous system, alongside the progression of effective treatments for brain-related conditions. The focal point of this discussion is the BBB and its intricate association with the CNS and neurotoxicology. The discourse commences by recent advancements in the medical application of quantum dots are examined. Subsequently, elucidating the mechanisms through which quantum dots infiltrate the human body and traverse into the brain. Additionally, the discourse delves into the factors that facilitate the passage of quantum dots across the BBB, primarily encompassing the physicochemical properties of quantum dots and the BBB's inherent capacity for self-permeability alteration. Furthermore, a concluding summary is presented, emphasizing existing research deficiencies and identifying promising avenues for further investigation within this field.

Protection from cisplatin-induced hearing loss with lentiviral vector-mediated ectopic expression of the anti-apoptotic protein BCL-XL

Cisplatin is a highly effective chemotherapeutic agent, but it can cause sensorineural hearing loss (SNHL) in patients. Cisplatin-induced ototoxicity is closely related to the accumulation of reactive oxygen species (ROS) and subsequent death of hair cells (HCs) and spiral ganglion neurons (SGNs). Despite various strategies to combat ototoxicity, only one therapeutic agent has thus far been clinically approved. Therefore, we have developed a gene therapy concept to protect cochlear cells from cisplatin-induced toxicity. Self-inactivating lentiviral (LV) vectors were used to ectopically express various antioxidant enzymes or anti-apoptotic proteins to enhance the cellular ROS scavenging or prevent apoptosis in affected cell types. In direct comparison, anti-apoptotic proteins mediated a stronger reduction in cytotoxicity than antioxidant enzymes. Importantly, overexpression of the most promising candidate, Bcl-xl, achieved an up to 2.5-fold reduction in cisplatin-induced cytotoxicity in HEI-OC1 cells, phoenix auditory neurons, and primary SGN cultures. BCL-XL protected against cisplatin-mediated tissue destruction in cochlear explants. Strikingly, in vivo application of the LV BCL-XL vector improved hearing and increased HC survival in cisplatin-treated mice. In conclusion, we have established a preclinical gene therapy approach to protect mice from cisplatin-induced ototoxicity that has the potential to be translated to clinical use in cancer patients.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Brain-derived neurotrophic factor in degenerative retinal diseases: Update and novel perspective

Dysfunction and death of neuronal cells are cardinal features of degenerative retinal diseases that are known to arise as the disease progresses. Increasingly evidence suggests that abnormal expression of brain-derived neurotrophic factor (BDNF) may serve as an obligatory relay of the dysfunction and death of neuronal cells in degenerative retinal diseases. Although disorder of BDNF, whether depletion or augmentation, has been connected with neuronal apoptosis and neuroinflammation, the exact mechanisms underlying the effect of impaired BDNF expression on degenerative retinal diseases remain unclear. Here, we present an overview of how BDNF is linked to pathological mechanism of retinal degenerative diseases, summarize BDNF-based treatment strategies, and discuss possible research perspectives in the future.

Whole transcriptome sequencing analysis of blood plasma-derived exosomes from immune-related hearing loss

BACKGROUND

Early diagnosis of immune-related hearing loss and timely treatment can prevent structural damage to the inner ear and contribute to hearing retention. Exosomal miRNAs, lncRNAs and proteins have great prospects as novel biomarkers for clinical diagnosis. Our study aimed to investigate the molecular mechanisms of exosomes or exosomal ceRNA regulatory networks in immune-related hearing loss.

METHODS

An immune-related hearing loss mice model was constructed by injection with inner ear antigen, and then the blood plasma samples of the mice were collected for exosomes isolation by ultra-centrifugation. Subsequently, the different exosomes were sent for whole transcriptome sequencing using Illumina platform. Finally, a ceRNA pair was chosen for validation by RT-qPCR and dual luciferase reporter gene assay.

RESULTS

The exosomes were successfully extracted from the blood samples of the control and the immune-related hearing loss mice. After sequencing, 94 differentially expressed (DE) lncRNAs, 612 DEmRNAs, and 100 DEmiRNAs were found in the immune-related hearing loss-associated exosomes. Afterwards, ceRNA regulatory networks consisting of 74 lncRNAs, 28 miRNAs and 256 mRNAs were proposed, and the genes in the ceRNA regulatory networks were significantly enriched in 34 GO terms of biological processes and 9 KEGG pathways. Finally, Gm9866 and Dusp7 were significantly up-regulated, while miR-185-5p level was declined in the exosomes from immune-related hearing loss, and Gm9866, miR-185-5p and Dusp7 interacted with each other.

CONCLUSIONS

Gm9866-miR-185-5p-Dusp7 was confirmed to be closely correlated with the occurrence and progression of immune-related hearing loss.

Mesoporous silica nanoparticles: Their potential as drug delivery carriers and nanoscavengers in Alzheimer's and Parkinson's diseases

Worldwide, populations face significant burdens from neurodegenerative disorders (NDDs), especially Alzheimer's and Parkinson's diseases. Although there are many proposed etiologies for neurodegenerative disorders, including genetic and environmental factors, the exact pathogenesis for these disorders is not fully understood. Most patients with NDDs are given lifelong treatment to improve their quality of life. There are myriad treatments for NDDs; however, these agents are limited by their side effects and difficulty in passing the blood-brain barrier (BBB). Furthermore, the central nervous system (CNS) active pharmaceuticals could offer symptomatic relief for the patient's condition without providing a complete cure or prevention by targeting the disease's cause. Recently, Mesoporous silica nanoparticles (MSNs) have gained interest in treating NDDs since their physicochemical properties and inherent ability to pass BBB make them possible drug carriers for several drugs for NDDs treatment. This paper provides insight into the pathogenesis and treatment of NDDs, along with the recent advances in applying MSNs as fibril scavengers. Moreover, the application of MSNs-based formulations in enhancing or sustaining drug release rate, and brain targeting via their responsive release properties, besides the neurotoxicity of MSNs, have been reviewed.

Closing the Gap between the Auditory Nerve and Cochlear Implant Electrodes: Which Neurotrophin Cocktail Performs Best for Axonal Outgrowth and Is Electrical Stimulation Beneficial?

Neurotrophins promote neurite outgrowth of auditory neurons and may help closing the gap to cochlear implant (CI) electrodes to enhance electrical hearing. The best concentrations and mix of neurotrophins for this nerve regrowth are unknown. Whether electrical stimulation (ES) during outgrowth is beneficial or may direct axons is another open question. Auditory neuron explant cultures of distinct cochlear turns of 6-7 days old mice were cultured for four days. We tested different concentrations and combinations of BDNF and NT-3 and quantified the numbers and lengths of neurites with an advanced automated analysis. A custom-made 24-well electrical stimulator based on two bulk CIs served to test different ES strategies. Quantification of receptors trkB, trkC, p75^NTR, and histological analysis helped to analyze effects. We found 25 ng/mL BDNF to perform best, especially in basal neurons, a negative influence of NT-3 in combined BDNF/NT-3 scenarios, and tonotopic changes in trk and p75^NTR receptor stainings. ES largely impeded neurite outgrowth and glia ensheathment in an amplitude-dependent way. Apical neurons showed slight benefits in neurite numbers and length with ES at 10 and 500 µA. We recommend BDNF as a potent drug to enhance the man-machine interface, but CIs should be better activated after nerve regrowth.

Neuro-nanotechnology: diagnostic and therapeutic nano-based strategies in applied neuroscience

Artificial, de-novo manufactured materials (with controlled nano-sized characteristics) have been progressively used by neuroscientists during the last several decades. The introduction of novel implantable bioelectronics interfaces that are better suited to their biological targets is one example of an innovation that has emerged as a result of advanced nanostructures and implantable bioelectronics interfaces, which has increased the potential of prostheses and neural interfaces. The unique physical-chemical properties of nanoparticles have also facilitated the development of novel imaging instruments for advanced laboratory systems, as well as intelligently manufactured scaffolds and microelectrodes and other technologies designed to increase our understanding of neural tissue processes. The incorporation of nanotechnology into physiology and cell biology enables the tailoring of molecular interactions. This involves unique interactions with neurons and glial cells in neuroscience. Technology solutions intended to effectively interact with neuronal cells, improved molecular-based diagnostic techniques, biomaterials and hybridized compounds utilized for neural regeneration, neuroprotection, and targeted delivery of medicines as well as small chemicals across the blood-brain barrier are all purposes of the present article.

Effect of Immunophilin Inhibitors on Cochlear Fibroblasts and Spiral Ganglion Cells

INTRODUCTION

Loss of hair cells and degeneration of spiral ganglion neurons (SGN) lead to severe hearing loss or deafness. The successful use of a cochlear implant (CI) depends among other factors on the number of surviving SGN. Postoperative formation of fibrous tissue around the electrode array causes an increase in electrical impedances at the stimulating contacts. The use of immunophilin inhibitors may reduce the inflammatory processes without suppressing the immune response. Here, we report on in vitro experiments with different concentrations of immunophilin inhibitors MM284 and compound V20 regarding a possible application of these substances in the inner ear.

METHODS

Standard cell lines (NIH/3T3 fibroblasts), freshly isolated SGN, and fibroblasts from neonatal rat cochleae (p3-5) were incubated with different concentrations of immunophilin inhibitors for 48 h. Metabolic activity of fibroblasts was investigated by MTT assay and cell survival by counting of immunochemically stained neurons and compared to controls.

RESULTS

MM284 did not affect SGN numbers and neurite growth at concentrations of 4 × 10-5 mol/L and below, whereas V20 had no effect at 8 × 10-6 mol/L and below. Metabolic activity of fibroblasts was unchanged at these concentrations.

CONCLUSION

Especially MM284 might be considered as a possible candidate for application within the cochlea.

Association of dietary factors with noise-induced hearing loss in Korean population: A 3-year national cohort study

Noise-induced hearing loss (NIHL) is a hearing impairment (HI) caused by various clinical factors. Identifying the relationship between NIHL and nutrient consumption could help in reducing the prevalence of hearing loss. The aim of this study was to analyze the relationship between NIHL and dietary factors using data of the Korea National Health and Nutrition Examination survey (KNHANES). The data were collected from The Fifth KNHANES 2010-2012. The survey was taken by a total of 10,850 participants aged 20-65 years. Air conduction audiometry was measured at 500, 1000, 2000, and 4000 Hz in both ears. Metabolic syndrome, noise exposure, alcohol consumption, smoking, income level, marital status, and nutritional intake were evaluated. The differences between non-HI and HI participants in the noise-exposed group showed statistically significant differences in age, sex, marital and smoking status, alcohol consumption, and fasting glucose and triglyceride levels (p<0.05). In a multiple regression analysis of the noise-exposed group, age showed a significant association with HI (OR: 0.604; 95% CI: 0.538-0.678) after adjusting for confounders. In multivariate analysis for dietary factors affecting HI in noise-exposed groups, retinol (OR: 1.356; 95% CI: 1.068-1.722), niacin (OR: 1.5; 95% CI: 1.022-2.201), and carbohydrates (OR: 0.692; 95% CI: 0.486-0.985) showed a significant association with NIHL. Age was identified as the only factor significantly affecting NIHL. When the dietary factors of the noise-exposed group were analyzed, high intake of niacin and retinol and low intake of carbohydrates appeared to reduce the risk of hearing loss.

Potential nanotechnology-based diagnostic and therapeutic approaches for Meniere's disease

Meniere's disease (MD) is a progressive inner ear disorder involving recurrent and prolonged episodes or attacks of vertigo with associated symptoms, resulting in a significantly reduced quality of life for sufferers. In most cases, MD starts in one ear; however, in one-third of patients, the disorder progresses to the other ear. Unfortunately, the etiology of the disease is unknown, making the development of effective treatments difficult. Nanomaterials, including nanoparticles (NPs) and nanocarriers, offer an array of novel diagnostic and therapeutic applications related to MD. NPs have specific features such as biocompatibility, biochemical stability, targetability, and enhanced visualization using imaging tools. This paper provides a comprehensive and critical review of recent advancements in nanotechnology-based diagnostic and therapeutic approaches for MD. Furthermore, the crucial challenges adversely affecting the use of nanoparticles to treat middle ear disorders are investigated. Finally, this paper provides recommendations and future directions for improving the performances of nanomaterials on theragnostic applications of MD.

Molecular and Functional Characterization of BDNF-Overexpressing Human Retinal Pigment Epithelial Cells Established by Sleeping Beauty Transposon-Mediated Gene Transfer

More and more patients suffer from multifactorial neurodegenerative diseases, such as age-related macular degeneration (AMD). However, their pathological mechanisms are still poorly understood, which complicates the development of effective therapies. To improve treatment of multifactorial diseases, cell-based gene therapy can be used to increase the expression of therapeutic factors. To date, there is no approved therapy for dry AMD, including late-stage geographic atrophy. We present a treatment option for dry AMD that transfers the brain-derived neurotrophic factor (BDNF) gene into retinal pigment epithelial (RPE) cells by electroporation using the plasmid-based Sleeping Beauty (SB) transposon system. ARPE-19 cells and primary human RPE cells were co-transfected with two plasmids encoding the SB100X transposase and the transposon carrying a BDNF transcription cassette. We demonstrated efficient expression and secretion of BDNF in both RPE cell types, which were further increased in ARPE-19 cell cultures exposed to hydrogen peroxide. BDNF-transfected cells exhibited lower apoptosis rates and stimulated neurite outgrowth in human SH-SY5Y cells. This study is an important step in the development of a cell-based BDNF gene therapy that could be applied as an advanced therapy medicinal product to treat dry AMD or other degenerative retinal diseases.

Mesoporous silica nanoparticle-modified electrode arrays of cochlear implants for delivery of siRNA-TGFβ1 into the inner ear

Cochlear implants (CI) are widely used in patients to restore hearing function. Uncontrolled fibrosis in the cochleae induced by excess secretion of TGFβ1 seriously affects the effectiveness of CIs. siRNA is a potential therapeutic strategy to downregulate TGFβ1 specifically. However, treatment with siRNA in cochleae is difficult due to the poor penetration capability and instability of siRNA and the inaccessibility and vulnerability of cochleae. To address these challenges, we developed amino-functionalized mesoporous silica nanoparticle (MSN-NH2)-modified electrode arrays to deliver siRNA-TGFβ1 into the inner ear. The shape, diameter, pore diameter, and zeta potential of MSN-NH2 were investigated. siRNA loading capability and protective effect of MSN-NH2 were determined by agarose gel electrophoresis assay. The cytotoxicity, cellular uptake assay, and TGFβ1 knockdown efficiency of MSN-NH2 were studied by CCK-8 assay, flow cytometry, and real-time PCR, respectively. MSN-NH2-siTGFβ1 nanoparticles were absorbed into the electrode arrays and worked in the cochleae. MSN-NH2-siTGFβ1-modified CI electrode arrays may be an attractive therapeutic clinical intervention strategy to inhibit cochlear implantation fibrosis.

Application progress of nanotechnology in regenerative medicine of diabetes mellitus

In recent years, the development of diabetic regenerative medicine has led to new developments and progress for the clinical treatment of diabetes mellitus and its various complications. Besides, the emergence of nanotechnology has injected new vitality into diabetic regenerative medicine. Nano-stent provides an appropriate direction for the regeneration of islet β cells, retinal tissue, nerve tissue, and wound tissue cells. Conductive nanomaterials promote various tissues' growth. Many nanoparticles also promote wound healing and present other advantages that have solved many potential problems in the practical application of regenerative medicine. In this review, we will summarize the application of nanotechnology in diabetic regenerative medicine.

Self-Assembled Nanoscale Materials for Neuronal Regeneration: A Focus on BDNF Protein and Nucleic Acid Biotherapeutic Delivery

Enabling challenging applications of nanomedicine and precision medicine in the treatment of neurodegenerative disorders requires deeper investigations of nanocarrier-mediated biomolecular delivery for neuronal targeting and recovery. The successful use of macromolecular biotherapeutics (recombinant growth factors, antibodies, enzymes, synthetic peptides, cell-penetrating peptide–drug conjugates, and RNAi sequences) in clinical developments for neuronal regeneration should benefit from the recent strategies for enhancement of their bioavailability. We highlight the advances in the development of nanoscale materials for drug delivery in neurodegenerative disorders. The emphasis is placed on nanoformulations for the delivery of brain-derived neurotrophic factor (BDNF) using different types of lipidic nanocarriers (liposomes, liquid crystalline or solid lipid nanoparticles) and polymer-based scaffolds, nanofibers and hydrogels. Self-assembled soft-matter nanoscale materials show favorable neuroprotective characteristics, safety, and efficacy profiles in drug delivery to the central and peripheral nervous systems. The advances summarized here indicate that neuroprotective biomolecule-loaded nanoparticles and injectable hydrogels can improve neuronal survival and reduce tissue injury. Certain recently reported neuronal dysfunctions in long-COVID-19 survivors represent early manifestations of neurodegenerative pathologies. Therefore, BDNF delivery systems may also help in prospective studies on recovery from long-term COVID-19 neurological complications and be considered as promising systems for personalized treatment of neuronal dysfunctions and prevention or retarding of neurodegenerative disorders.

Nanomaterials for Inner Ear Diseases: Challenges, Limitations and Opportunities

The inner ear is located deep in the temporal bone and has a complex anatomy. It is difficult to observe and obtain pathological tissues directly. Therefore, the diagnosis and treatment of inner ear diseases have always been a major clinical problem. The onset of inner ear disease can be accompanied by symptoms such as hearing loss, dizziness and tinnitus, which seriously affect people's lives. Nanoparticles have the characteristics of small size, high bioavailability and strong plasticity. With the development of related research on nanoparticles in inner ear diseases, nanoparticles have gradually become a research hotspot in inner ear diseases. This review briefly summarizes the research progress, opportunities and challenges of the application of nanoparticles in inner ear diseases.

Inner Ear Drug Delivery for Sensorineural Hearing Loss: Current Challenges and Opportunities

Most therapies for treating sensorineural hearing loss are challenged by the delivery across multiple tissue barriers to the hard-to-access anatomical location of the inner ear. In this review, we will provide a recent update on various pharmacotherapy, gene therapy, and cell therapy approaches used in clinical and preclinical studies for the treatment of sensorineural hearing loss and approaches taken to overcome the drug delivery barriers in the ear. Small-molecule drugs for pharmacotherapy can be delivered via systemic or local delivery, where the blood-labyrinth barrier hinders the former and tissue barriers including the tympanic membrane, the round window membrane, and/or the oval window hinder the latter. Meanwhile, gene and cell therapies often require targeted delivery to the cochlea, which is currently achieved via intra-cochlear or intra-labyrinthine injection. To improve the stability of the biomacromolecules during treatment, e.g., RNAs, DNAs, proteins, additional packing vehicles are often required. To address the diverse range of biological barriers involved in inner ear drug delivery, each class of therapy and the intended therapeutic cargoes will be discussed in this review, in the context of delivery routes commonly used, delivery vehicles if required (e.g., viral and non-viral nanocarriers), and other strategies to improve drug permeation and sustained release (e.g., hydrogel, nanocarriers, permeation enhancers, and microfluidic systems). Overall, this review aims to capture the important advancements and key steps in the development of inner ear therapies and delivery strategies over the past two decades for the treatment and prophylaxis of sensorineural hearing loss.

Brain-Derived Neurotrophic Factor-Mediated Neuroprotection in Glaucoma: A Review of Current State of the Art

Retinal ganglion cells (RGCs) are neurons of the visual system that are responsible for transmitting signals from the retina to the brain via the optic nerve. Glaucoma is an optic neuropathy characterized by apoptotic loss of RGCs and degeneration of optic nerve fibers. Risk factors such as elevated intraocular pressure and vascular dysregulation trigger the injury that culminates in RGC apoptosis. In the event of injury, the survival of RGCs is facilitated by neurotrophic factors (NTFs), the most widely studied of which is brain-derived neurotrophic factor (BDNF). Its production is regulated locally in the retina, but transport of BDNF retrogradely from the brain to retina is also crucial. Not only that the interruption of this retrograde transport has been detected in the early stages of glaucoma, but significantly low levels of BDNF have also been detected in the sera and ocular fluids of glaucoma patients, supporting the notion that neurotrophic deprivation is a likely mechanism of glaucomatous optic neuropathy. Moreover, exogenous NTF including BDNF administration was shown reduce neuronal loss in animal models of various neurodegenerative diseases, indicating the possibility that exogenous BDNF may be a treatment option in glaucoma. Current literature provides an extensive insight not only into the sources, transport, and target sites of BDNF but also the intracellular signaling pathways, other pathways that influence BDNF signaling and a wide range of its functions. In this review, the authors discuss the neuroprotective role of BDNF in promoting the survival of RGCs and its possible application as a therapeutic tool to meet the challenges in glaucoma management. We also highlight the possibility of using BDNF as a biomarker in neurodegenerative disease such as glaucoma. Further we discuss the challenges and future strategies to explore the utility of BDNF in the management of glaucoma.

Development of Neuronal Guidance Fibers for Stimulating Electrodes: Basic Construction and Delivery of a Growth Factor

State-of-the-art treatment for sensorineural hearing loss is based on electrical stimulation of residual spiral ganglion neurons (SGNs) with cochlear implants (CIs). Due to the anatomical gap between the electrode contacts of the CI and the residual afferent fibers of the SGNs, spatial spreading of the stimulation signal hampers focused neuronal stimulation. Also, the efficiency of a CI is limited because SGNs degenerate over time due to loss of trophic support. A promising option to close the anatomical gap is to install fibers as artificial nerve guidance structures on the surface of the implant and install on these fibers drug delivery systems releasing neuroprotective agents. Here, we describe the first steps in this direction. In the present study, suture yarns made of biodegradable polymers (polyglycolide/poly-ε-caprolactone) serve as the basic fiber material. In addition to the unmodified fiber, also fibers modified with amine groups were employed. Cell culture investigations with NIH 3T3 fibroblasts attested good cytocompatibility to both types of fibers. The fibers were then coated with the extracellular matrix component heparan sulfate (HS) as a biomimetic of the extracellular matrix. HS is known to bind, stabilize, modulate, and sustainably release growth factors. Here, we loaded the HS-carrying fibers with the brain-derived neurotrophic factor (BDNF) which is known to act neuroprotectively. Release of this neurotrophic factor from the fibers was followed over a period of 110 days. Cell culture investigations with spiral ganglion cells, using the supernatants from the release studies, showed that the BDNF delivered from the fibers drastically increased the survival rate of SGNs in vitro. Thus, biodegradable polymer fibers with attached HS and loaded with BDNF are suitable for the protection and support of SGNs. Moreover, they present a promising base material for the further development towards a future neuronal guiding scaffold.

A Window of Opportunity: Perilymph Sampling from the Round Window Membrane Can Advance Inner Ear Diagnostics and Therapeutics

In the clinical setting, the pathophysiology of sensorineural hearing loss is poorly defined and there are currently no diagnostic tests available to differentiate between subtypes. This often leaves patients with generalized treatment options such as steroids, hearing aids, or cochlear implantation. The gold standard for localizing disease is direct biopsy or imaging of the affected tissue; however, the inaccessibility and fragility of the cochlea make these techniques difficult. Thus, the establishment of an indirect biopsy, a sampling of inner fluids, is needed to advance inner ear diagnostics and allow for the development of novel therapeutics for inner ear disease. A promising source is perilymph, an inner ear liquid that bathes multiple structures critical to sound transduction. Intraoperative perilymph sampling via the round window membrane of the cochlea has been successfully used to profile the proteome, metabolome, and transcriptome of the inner ear and is a potential source of biomarker discovery. Despite its potential to provide insight into inner ear pathologies, human perilymph sampling continues to be controversial and is currently performed only in conjunction with a planned procedure where the inner ear is opened. Here, we review the safety of procedures in which the inner ear is opened, highlight studies where perilymph analysis has advanced our knowledge of inner ear diseases, and finally propose that perilymph sampling could be done as a stand-alone procedure, thereby advancing our ability to accurately classify sensorineural hearing loss.

Pharmacokinetics and biodistribution of supraparticle-delivered neurotrophin 3 in the guinea pig cochlea

Hearing loss is the most prevalent sensory disorder affecting nearly half a billion people worldwide. Aside from devices to assist hearing, such as hearing aids and cochlear implants, a drug treatment for hearing loss has yet to be developed. The neurotrophin family of growth factors has long been established as a potential therapy, however delivery of these factors into the inner ear at therapeutic levels over a sustained period of time has remained a challenge restricting clinical translation. We previously demonstrated that direct delivery of exogenous neurotrophin-3 (NT3) in the guinea pig cochleae via a bolus injection was rapidly cleared from the inner ear, with almost complete elimination 3 days post-treatment. Here, we explored the potential of suprapaticles (SPs) for NT3 delivery to the inner ear to achieve sustained delivery over time. SPs are porous spheroid structures comprised of smaller colloidal silica nanoparticles that provide a platform for long-term controlled release of therapeutics. This study aimed to assess the pharmacokinetics and biodistribution of SP-delivered NT3. We used a radioactive tracer (iodine 125: ¹²⁵I) to label the NT3 to determine the loading, retention and distribution of NT3 delivered via SPs. Gamma measurements taken from ¹²⁵I NT3 loaded SPs revealed high drug loading (an average of 5.3 μg of NT3 loaded per SP weighing 50 μg) and elution capacities in vitro (67% cumulative release over one month). Whole cochlear gamma measurements from SP-implanted cochleae harvested at various time points revealed detection of ¹²⁵I NT3 in the guinea pig cochlea after one month, with 3.6 and 10% of the loaded drug remaining in the intracochlear and round window-implanted cochleae respectively. Autoradiography analysis of cochlear micro-sections revealed widespread ¹²⁵I NT3 distribution after intracochlear SP delivery, but more restricted distribution with the round window delivery approach. Collectively, drug delivery into the inner ear using SPs support sustained, long-term availability and release of neurotrophins in the inner ear.

Neurovascular Impairment and Therapeutic Strategies in Diabetic Retinopathy

Diabetic retinopathy has recently been defined as a highly specific neurovascular complication of diabetes. The chronic progression of the impairment of the interdependence of neurovascular units (NVUs) is associated with the pathogenesis of diabetic retinopathy. The NVUs consist of neurons, glial cells, and vascular cells, and the interdependent relationships between these cells are disturbed under diabetic conditions. Clinicians should understand and update the current knowledge of the neurovascular impairments in diabetic retinopathy. Above all, neuronal cell death is an irreversible change, and it is directly related to vision loss in patients with diabetic retinopathy. Thus, neuroprotective and vasoprotective therapies for diabetic retinopathy must be established. Understanding the physiological and pathological interdependence of the NVUs is helpful in establishing neuroprotective and vasoprotective therapies for diabetic retinopathy. This review focuses on the pathogenesis of the neurovascular impairments and introduces possible neurovascular protective therapies for diabetic retinopathy.

Nanocarriers for Inner Ear Disease Therapy

Hearing loss is a common disease due to sensory loss caused by the diseases in the inner ear. The development of delivery systems for inner ear disease therapy is important to achieve high efficiency and reduce side effects. Currently, traditional drug delivery systems exhibit the potential to be used for inner ear disease therapy, but there are still some drawbacks. As nanotechnology is developing these years, one of the solutions is to develop nanoparticle-based delivery systems for inner ear disease therapy. Various nanoparticles, such as soft material and inorganic-based nanoparticles, have been designed, tested, and showed controlled delivery of drugs, improved targeting property to specific cells, and reduced systemic side effects. In this review, we summarized recent progress in nanocarriers for inner ear disease therapy. This review provides useful information on developing promising nanocarriers for the efficient treatment of inner ear diseases and for further clinical applications for inner ear disease therapy.

Simultaneous treatment with pentoxifylline does not adversely affect the neurotrophic effects of brain-derived neurotrophic factor on spiral ganglion neurons

The hemorheologic drug pentoxifylline is applied for the treatment of sudden sensorineural hearing loss and tinnitus to improve cochlear microcirculation. Recent studies also suggest protective and trophic effects on neuronal cells. Because the preservation of sensorineural structures of the inner ear is fundamental for normal hearing and hearing restoration with auditory prostheses, pentoxifylline and neurotrophic factors such as brain-derived neurotrophic factor (BDNF) are promising candidates to treat degenerative disorders of the inner ear. We used an in-vitro model to determine the neurotrophic effects of these factors on spiral ganglion cells from postnatal rats. Pentoxifylline, alone and in combination with BDNF, was added at various concentrations to the cultured cells. Cells were immunolabeled and analyzed to determine neuronal survival, neurite length, neuronal branching and morphology. Pentoxifylline did not significantly increase or decrease neuronal survival, neurite length and neuronal branching compared to control cultures. Analysis of cellular morphology showed that diverse neuronal subtypes developed in the presence of pentoxifylline. Our data revealed that pentoxifylline did not interfere with the robust neurotrophic effects of BDNF on spiral ganglion neurons when cultured cells were treated with pentoxifylline and BDNF simultaneously. The results of our study do not suggest major neurotrophic effects of pentoxifylline on cultured spiral ganglion neurons. Because pentoxifylline has no detrimental effects on spiral ganglion neurons and does not reduce the effects of BDNF, both agents could be combined to treat diseases of the inner ear provided that future in vivo experiments and clinical studies support these findings.

Approaches for ear-targeted delivery systems in neurosensory disorders to avoid chronic hearing loss mediated neurological diseases

BACKGROUND & OBJECTIVE

Hearing loss is a common audio-vestibular-related neurosensory disability of inner ears, in which patients exhibit clinical symptoms of dizziness, gait unsteadiness, and oscillopsia, at an initial stage. While, if such disorders are untreated for a prolonged duration then the progression of disease into a chronic state significantly decreases GABA level as well as an alteration in the neurotransmission of CNS systems. Hence, to control the progression of disease into a chronic state, timely and targeted delivery of the drug into the site of action in the ear is now attracting the interest of neurologists for effective and safe treatment of such disorders. Among delivery systems, owing to small dimension, better penetration, rate-controlled release, higher bioavailability; nanocarriers are preferred to overcome delivery barriers, improvement in residence time, and enhanced the performance of loaded drugs. Subsequently, these carriers also stabilize encapsulated drugs while the opportunity to modify the surface of carriers favors guided direction for site-specific targeting. Conventional routes of drug delivery such as oral. intravenous, and intramuscular are poorer in performance because of inadequate blood supply to the inner ear and limited penetration of blood-inner ear barrier.

CONCLUSION

This review summarized novel aspects of non-invasive and biocompatible nanoparticles-based approaches for targeted delivery of drugs into the cochlea of the ear to reduce the rate, and extent of the emergence of any hearing loss mediated neurological disorders.

Chemically induced hypoxia by dimethyloxalylglycine (DMOG)-loaded nanoporous silica nanoparticles supports endothelial tube formation by sustained VEGF release from adipose tissue-derived stem cells

Inadequate vascularization leading to insufficient oxygen and nutrient supply in deeper layers of bioartificial tissues remains a limitation in current tissue engineering approaches to which pre-vascularization offers a promising solution. Hypoxia triggering pre-vascularization by enhanced vascular endothelial growth factor (VEGF) expression can be induced chemically by dimethyloxalylglycine (DMOG). Nanoporous silica nanoparticles (NPSNPs, or mesoporous silica nanoparticles, MSNs) enable sustained delivery of molecules and potentially release DMOG allowing a durable capillarization of a construct. Here we evaluated the effects of soluble DMOG and DMOG-loaded NPSNPs on VEGF secretion of adipose tissue-derived stem cells (ASC) and on tube formation by human umbilical vein endothelial cells (HUVEC)-ASC co-cultures. Repeated doses of 100 µM and 500 µM soluble DMOG on ASC resulted in 3- to 7-fold increased VEGF levels on day 9 (P < 0.0001). Same doses of DMOG-NPSNPs enhanced VEGF secretion 7.7-fold (P < 0.0001) which could be maintained until day 12 with 500 µM DMOG-NPSNPs. In fibrin-based tube formation assays, 100 µM DMOG-NPSNPs had inhibitory effects whereas 50 µM significantly increased tube length, area and number of junctions transiently for 4 days. Thus, DMOG-NPSNPs supported endothelial tube formation by upregulated VEGF secretion from ASC and thus display a promising tool for pre-vascularization of tissue-engineered constructs. Further studies will evaluate their effect in hydrogels under perfusion.

Coating of cochlear implant electrodes with bioactive DNA-loaded calcium phosphate nanoparticles for the local transfection of stimulatory proteins

Calcium phosphate nanoparticles were loaded with nucleic acids to enhance the on-growth of tissue to a cochlear implant electrode. The nanoparticle deposition on a metallic electrode surface is possible by electrophoretic deposition (EPD) or layer-by-layer deposition (LbL). Impedance spectroscopy showed that the coating layer did not interrupt the electrical conductance at physiological frequencies and beyond (1-40,000 Hz). The transfection was demonstrated with the model cell lines HeLa and 3T3 as well as with primary explanted spiral ganglion neurons (rat) with the model protein enhanced green fluorescent protein (EGFP). The expression of the functional protein brain-derived neurotrophic factor (BDNF) was also shown. Thus, a coating of inner-ear cochlear implant electrodes with nanoparticles that carry nucleic acids will enhance the ongrowth of spiral ganglion cell axons for an improved transmission of electrical pulses.

Nanoformulations of Ursolic Acid: A Modern Natural Anticancer Molecule

Background: Ursolic acid (UA) is a natural pentacyclic triterpene derived from fruit, herb, and other plants. UA can act on molecular targets of various signaling pathways, inhibit the growth of cancer cells, promote cycle stagnation, and induce apoptosis, thereby exerting anticancer activity. However, its poor water-solubility, low intestinal mucosal absorption, and low bioavailability restrict its clinical application. In order to overcome these deficiencies, nanotechnology, has been applied to the pharmacological study of UA.

Objective: In this review, we focused on the absorption, distribution, and elimination pharmacokinetics of UA in vivo, as well as on the research progress in various UA nanoformulations, in the hope of providing reference information for the research on the anticancer activity of UA.

Methods: Relevant research articles on Pubmed and Web of Science in recent years were searched selectively by using the keywords and subheadings, and were summarized systematically.

Key finding: The improvement of the antitumor ability of the UA nanoformulations is mainly due to the improvement of the bioavailability and the enhancement of the targeting ability of the UA molecules. UA nanoformulations can even be combined with computational imaging technology for monitoring or diagnosis.

Conclusion: Currently, a variety of UA nanoformulations, such as micelles, liposomes, and nanoparticles, which can increase the solubility and bioactivity of UA, while promoting the accumulation of UA in tumor tissues, have been prepared. Although the research of UA in the nanofield has made great progress, there is still a long way to go before the clinical application of UA nanoformulations.

Nanoparticles for the Treatment of Inner Ear Infections

The inner ear is sensitive to various infections of viral, bacterial, or fungal origin, which, if left untreated, may lead to hearing loss or progress through the temporal bone and cause intracranial infectious complications. Due to its isolated location, the inner ear is difficult to treat, imposing an acute need for improving current therapeutic approaches. A solution for enhancing antimicrobial treatment performance is the use of nanoparticles. Different inorganic, lipidic, and polymeric-based such particles have been designed, tested, and proven successful in the controlled delivery of medication, improving drug internalization by the targeted cells while reducing the systemic side effects. This paper makes a general presentation of common inner ear infections and therapeutics administration routes, further focusing on newly developed nanoparticle-mediated treatments.

Expression of neurotrophic factor genes by human adipose stem cells post-induction by deprenyl

Human adipose stem cells (hASCs) were introduced as appropriate candidate due to advantages like ease of isolation, in vitro expansion and lack of immune response. Deprenyl (Dep) was used to induce bone marrow stem cells into neuron-like cells. We investigated the Dep effect on neurotrophin genes expression in hASCs and their differentiation into neuron-like cells. The cells were isolated from small pieces of abdominal adipose tissue and subjected to flow cytometry to confirm purification. The osteogenic and adipogenic differentiation were identified. The proliferation rate and neurotrophin genes expression of treated cells were evaluated by MTT, TH immunostaining and RT-PCR. hASCs had positive response to CD44, CD73, CD90, CD105 markers and negative response to CD34 and CD45 markers and differentiated into adipocytes and osteocytes. Exposure to 10–7 M of Dep for 24 hours caused a significant increase of viable cells and BDNF, NTF-3 genes expression as compared to cultured cells in serum free medium and had no effect on the expression of NGF and GDNF genes. Based on our results, Dep is able to induce BDNF, NTF-3 and NTF-4 genes expression and neroun-like morphology in hASCs.

Potentiation of Brain-Derived Neurotrophic Factor-Induced Protection of Spiral Ganglion Neurons by C3 Exoenzyme/Rho Inhibitor

Preservation of the excitability of spiral ganglion neurons (SGN) may contribute to an improved speech perception after cochlear implantation. Thus, the application of exogenous neurotrophic factors such as the neurotrophin brain-derived neurotrophic factor (BDNF) to increase SGN survival in vitro and in vivo is a promising pharmacological approach in cochlear implant (CI) research. Due to the difficult pharmacokinetic profile of proteins such as BDNF, there is a quest for small molecules to mediate the survival of SGN or to increase the efficacy of BDNF. The C3 exoenzyme from Clostridium botulinum could be a potential new candidate for the protection and regeneration of SGN. Inhibition of the RhoA GTPase pathway which can be mediated by C3 is described as a promising strategy to enhance axonal regeneration and to exert pro-survival signals in neurons. Nanomolar concentrations of C3, its enzymatically inactive form C3^E174Q, and a 26mer C-terminal peptide fragment covering amino acid 156–181 (C3^156-181) potentiated the neuroprotective effect on SGN mediated by BDNF in vitro. The neuroprotective effect of C3/BDNF was reduced to the neuroprotective effect of BDNF alone after the treatment with wortmannin, an inhibitor of the phosphatidylinositol-3-kinase (PI3K).The exoenzyme C3 (wild-type and enzyme-deficient) and the C3 peptide fragment C3^154–181 present novel biologically active compounds for the protection of the SGN. The exact underlying intracellular mechanisms that mediate the neuroprotective effect are not clarified yet, but the combination of BDNF (TrkB stimulation) and C3 exoenzyme (RhoA inhibition) can be used to protect SGN in vitro.

Brain-derived Neurotrophic Factor and Its Applications through Nanosystem Delivery

Brain-derived neurotrophic factor (BDNF) is a protein that performs a neurotrophic function. BDNF and its receptors are widely expressed in the nervous system and can promote the growth of neurons and the formation of neuronal synapses in the brain. Studies have shown that a lack of BDNF can lead to impairment of memory and cognitive functions, indicating that BDNF plays an important role in mental illness and neurodegenerative diseases. The combination of stem cells and BDNF-releasing nanomaterials holds great promise in regenerative medicine, especially in the treatment of neurological diseases. For example, Alzheimer's disease, depression, Parkinson's disease, spinal cord injury, etc. The combination of stem cell/pharmacologically active carrier and BDNF-nano/hydrogel provided a useful new type of local delivery tool for the treatment of the nervous system and other diseases. It can not only provide BDNF but also stem cells. These studies will provide a scientific basis for the development and application of BDNF in the future.

Lipid nanoparticles-encapsulated brain-derived neurotrophic factor mRNA delivered through the round window niche in the cochleae of guinea pigs

The treatment of sensorineural hearing loss (SNHL) may be achieved via the application of a cochlear implant (CI) that allows the electrical stimulation of spiral ganglion neurons (SGNs). Nevertheless, the efficacy of CIs is limited by the degeneration of SGNs following SNHL. Although the application of exogenous neurotrophic factors has been reported to decrease SGN degeneration, non-invasive targeted drug delivery systems are required to achieve effective results. In this study, an SS-cleavable proton-activated lipid-like material [ssPalm; a neutral lipid nanoparticle (LNP)], was loaded with mRNA, and the efficacy of this material as a delivery system was investigated. Our results showed that LNP_ssPalm carrying brain-derived neurotrophic factor (BDNF) mRNA was suitable for the treatment of inner ear diseases, preventing the degeneration of SGNs. In conclusion, this modern nanotechnology-based bioconjugation system, LNP_ssPalm, is a potential non-invasive targeted therapy allowing the delivering biomaterials to specific structures within the inner ear for the treatment of SHNL.

Challenges of BDNF-based therapies: From common to rare diseases

Neurotrophins are a well-known family of neurotrophic factors that play an important role both in the central and peripheral nervous systems, where they modulate neuronal survival, development, function and plasticity. Brain-derived neurotrophic factor (BDNF) possesses diverse biological functions which are mediated by the activation of two main classes of receptors, the tropomyosin-related kinase (Trk) B and the p75 neurotrophin receptor (p75^NTR). The therapeutic potential of BDNF has drawn attention since dysregulation of its signalling cascades has been suggested to underlie the pathogenesis of both common and rare diseases. Multiple strategies targeting this neurotrophin have been tested; most have found obstacles that ultimately hampered their effectiveness. This review focuses on the involvement of BDNF and its receptors in the pathophysiology of Alzheimer's disease (AD), Amyotrophic Lateral Sclerosis (ALS) and Rett Syndrome (RTT). We describe the known mechanisms leading to the impairment of BDNF/TrkB signalling in these disorders. Such mechanistic insight highlights how BDNF signalling compromise can take various shapes, nearly disease-specific. Therefore, BDNF-based therapeutic strategies must be specifically tailored and are more likely to succeed if a combination of resources is employed.

Cochlear implants and other inner ear prostheses: today and tomorrow

Cochlear implants (CIs) are implantable auditory prostheses designed to restore access to sound in deaf individuals via direct electrical stimulation of the auditory nerve. While CIs have been successful in restoring speech perception to many deaf patients, outcomes are variable and speech recognition in noise remains a problem. This chapter will review the factors underlying this variability, and discuss significant recent innovations to address these issues including neural health preservation, characterization, and regeneration, and other inner ear prostheses. The emerging role of central auditory plasticity will also be discussed. Together, these advances will point to the likely future directions for advancing the next generation of CIs and other inner ear prostheses.

Expression and Localization of BDNF/TrkB System in the Zebrafish Inner Ear

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, is involved in multiple and fundamental functions of the central and peripheral nervous systems including sensory organs. Despite recent advances in knowledge on the functional significance of BDNF and TrkB in the regulation of the acoustic system of mammals, the localization of BDNF/TrkB system in the inner ear of zebrafish during development, is not well known. Therefore, the goal of the present study is to analyze the age-dependent changes using RT-PCR, Western Blot and single and double immunofluorescence of the BDNF and its specific receptor in the zebrafish inner ear. The results showed the mRNA expression and the cell localization of BDNF and TrkB in the hair cells of the crista ampullaris and in the neuroepithelium of the utricle, saccule and macula lagena, analyzed at different ages. Our results demonstrate that the BDNF/TrkB system is present in the sensory cells of the inner ear, during whole life. Therefore, this system might play a key role in the development and maintenance of the hair cells in adults, suggesting that the zebrafish inner ear represents an interesting model to study the involvement of the neurotrophins in the biology of sensory cells

Diabetic Retinopathy and BDNF: A Review on Its Molecular Basis and Clinical Applications

Impairment of neuroprotection and vasculopathy are the main reasons for the progression of diabetic retinopathy. In this review, we decided to illustrate the molecular and clinical aspects of diabetic retinal neuro-vasculopathy. We searched the Web of Science, PubMed, and Scopus databases with these keywords: “brain-derived neurotrophic factor” and “vascular endothelial growth factor” and/or “diabetic retinopathy.” The most relevant in vitro and clinical trial studies were then extracted for final interpretation. Brain-derived neurotrophic factor and the vascular endothelial growth factor have pivotal roles in the pathogenesis of diabetic retinopathy. They have neuroprotective effects on the retina. However, there are controversial results on the relation between these two factors. Reviewing available articles, we have concluded that various concentrations of these molecules at different stages of retinopathy may exert different effects. Optimal doses of the brain-derived neurotrophic factor at the early stages of retinopathy may have a neuroprotective effect. In contrast, higher concentrations of brain-derived neurotrophic factor might induce inflammatory responses. Damage to the retinal cells due to metabolic alterations associated with diabetes and its consequence vasculopathy may also lead to changes in the ocular microenvironment and cytokines. Changes in cytokines result in the modification of neural cell receptors and the overproduction of vascular endothelial growth factor. It seems that controlling the optimal levels of neuroprotective molecules in the retinal tissue is the main step to halter diabetic retinopathy.

Inner ear delivery: Challenges and opportunities

OBJECTIVES

The treatment of inner ear disorders remains challenging due to anatomic barriers intrinsic to the bony labyrinth. The purpose of this review is to highlight recent advances and strategies for overcoming these barriers and to discuss promising future avenues for investigation.

DATA SOURCES

The databases used were PubMed, EMBASE, and Web of Science.

RESULTS

Although some studies aimed to improve systemic delivery using nanoparticle systems, the majority enhanced local delivery using hydrogels, nanoparticles, and microneedles. Developments in direct intracochlear delivery include intracochlear injection and intracochlear implants.

CONCLUSIONS

In the absence of a systemic drug that targets only the inner ear, the best alternative is local delivery that harnesses a combination of new strategies to overcome anatomic barriers. The combination of microneedle technology with hydrogel and nanoparticle delivery is a promising area for future investigation.

LEVEL OF EVIDENCE

NA.

Nose-to-brain co-delivery of repurposed simvastatin and BDNF synergistically attenuates LPS-induced neuroinflammation

A therapeutic strategy that can combat the multifaceted nature of neuroinflammation pathology was investigated. Thus, we fabricated PEG-PdLLA polymersomes and evaluated the efficacy in co-delivery of simvastatin (Sim, as a repurposed anti-inflammatory agent) with brain derived neurotrophic factor (BDNF, as an exogeneous trophic factor supplementation). Using LPS model of neuroinflammation, intranasal administration of combination drug-loaded polymersomes (containing both Sim and BDNF; Sim-BDNF-Ps) markedly down-regulated brain levels of cytokines compared to free drug and single-drug-loaded polymersomes. Further, Sim-BDNF-Ps effectively replenished brain level of BDNF that was depleted following neuroinflammation, resulting in a 2-fold BDNF increase versus untreated LPS control group. We found out that the efficiency of the combination drug-loaded polymersomes to suppress microglia activation in brain regions followed the order: frontal cortex > striatum > hippocampus. Our findings indicated that Sim-BDNF-Ps could effectively inhibit microglial-mediated inflammation as well as potentially resolve the neurotoxic microenvironment that is often associated with neuroinflammation.

Opportunities and challenging issues of nanomaterials in otological fields: an occupational health perspective

Nanotechnology may offer innovative solutions to overcome the physiological and anatomical barriers that make the diagnosis and treatment of ear diseases an extremely challenging issue. However, despite the solutions provided by nano-applications, the still little-known toxicological behavior of nanomaterials raised scientific concerns regarding their biosafety for treated patients and exposed workers. Therefore, this review provides an overview on recent developments and upcoming opportunities in nanoscale otological applications, and critically assesses possible adverse effects of nanosized compounds on ear structures and hearing functionality. Although such preliminary data do not allow to draw definite strategies for the evaluation of nanomaterial ototoxicity, they can still be useful to improve scientific community and workforce awareness regarding possible nanomaterial adverse effects on ear.

Superparamagnetic Nanoparticle Delivery to the Cochlea Through Round Window by External Magnetic Field: Feasibility and Toxicity

Introduction. The objective of this study was to evaluate the feasibility and toxicity of superparamagnetic iron oxide nanoparticles (SPIONs) administered into the cochlea through the round window (RW) by an external magnetic field. Materials and Methods. In 5 Wistar rats, the left RW was punctured. SPIONs suspended in hyaluronic gel (5 mg/mL) were applied in the RW niche and covered by a muscle graft. The nanoparticles were mobilized using a rare earth magnet (0.54 T) held in 4 consecutive positions around the head. The right ear served as control. Hearing function was monitored by auditory brainstem responses (4-32 kHz tone bursts). Results. The auditory thresholds remained unchanged 1 month after the administration. The histological study of the cochleae showed that SPIONs were driven into the scala tympani in the basal turn, the second turn, and the apex. Conclusion. Superparamagnetic nanoparticles can be driven inside the cochlea toward the apex with a preserved hearing up to 1 month in rats.

Nanoparticle technology and stem cell therapy team up against neurodegenerative disorders

The convergence of nanoparticles and stem cell therapy holds great promise for the study, diagnosis, and treatment of neurodegenerative disorders. Researchers aim to harness the power of nanoparticles to regulate cellular microenvironment, improve the efficiency of cell and drug delivery to the brain, and enhance the survival of stem cell transplants. Understanding the various properties of different nanoparticles is key to applying them to clinical therapies; the many distinct types of nanoparticles offer unique capacities for medical imaging, diagnosis, and treatment of neurodegeneration disorders. In this review we introduce the biology of Alzheimer's, Parkinson's Disease, and amyotrophic lateral sclerosis, and discuss the potentials and shortcomings of metal, silica, lipid-based, polymeric, and hydrogel nanoparticles for diagnosis and treatment of neurodegenerative disorders. We then provide an overview of current strategies in stem cell therapies and how they can be combined with nanotechnology to improve clinical outcomes.

Mesenchymal stem cell therapy assisted by nanotechnology: a possible combinational treatment for brain tumor and central nerve regeneration

Mesenchymal stem cells (MSCs) intrinsically possess unique features that not only help in their migration towards the tumor-rich environment but they also secrete versatile types of secretomes to induce nerve regeneration and analgesic effects at inflammatory sites. As a matter of course, engineering MSCs to enhance their intrinsic abilities is growing in interest in the oncology and regenerative field. However, the concern of possible tumorigenesis of genetically modified MSCs prompted the development of non-viral transfected MSCs armed with nanotechnology for more effective cancer and regenerative treatment. Despite the fact that a large number of successful studies have expanded our current knowledge in tumor-specific targeting, targeting damaged brain site remains enigmatic due to the presence of a blood–brain barrier (BBB). A BBB is a barrier that separates blood from brain, but MSCs with intrinsic features of transmigration across the BBB can efficiently deliver desired drugs to target sites. Importantly, MSCs, when mediated by nanoparticles, can further enhance tumor tropism and can regenerate the damaged neurons in the central nervous system through the promotion of axon growth. This review highlights the homing and nerve regenerative abilities of MSCs in order to provide a better understanding of potential cell therapeutic applications of non-genetically engineered MSCs with the aid of nanotechnology.