Adenovirus-mediated gene transfer in olfactory epithelium and olfactory bulb: a long-term study

Olfactory Loss and Dysfunction in Ciliopathies: Molecular Mechanisms and Potential Therapies

BACKGROUND

Ciliopathies are a class of inherited pleiotropic genetic disorders in which alterations in cilia assembly, maintenance, and/or function exhibit penetrance in the multiple organ systems. Olfactory dysfunction is one such clinical manifestation that has been shown in both patients and model organisms. Existing therapies for ciliopathies are limited to the treatment or management of symptoms. The last decade has seen an increase in potential curative therapeutic options including small molecules and biologics. Recent work in multiciliated olfactory sensory neurons has demonstrated the capacity of targeted gene therapy to restore ciliation in terminally differentiated cells and rescue olfactory function. This review will discuss the current understanding of the penetrance of ciliopathies in the olfactory system. Importantly, it will highlight both pharmacological and biological approaches, and their potential therapeutic value in the olfactory system and other ciliated tissues.

METHODS

We undertook a structured and comprehensive search of peer-reviewed research literature encompassing in vitro, in vivo, model organism, and clinical studies. From these publications, we describe the olfactory system, and discuss the penetrance of ciliopathies and impact of cilia loss on olfactory function. In addition, we outlined the developing therapies for ciliopathies across different organ and cell culture systems, and discussed their potential therapeutic application to the mammalian olfactory system.

RESULTS

One-hundred sixty-one manuscripts were included in the review, centering on the understanding of olfactory penetrance of ciliopathies, and discussing the potential therapeutic options for ciliopathies in the context of the mammalian olfactory system. Forty-four manuscripts were used to generate a table listing the known congenital causes of olfactory dysfunction, with the first ten listed are linked to ciliopathies. Twenty-three manuscripts were used to outline the potential of small molecules for the olfactory system. Emphasis was placed on HDAC6 inhibitors and lithium, both of which were shown to stabilize microtubule structures, contributing to ciliogenesis and cilia lengthening. Seventy-five manuscripts were used to describe gene therapy and gene therapeutic strategies. Included were the implementation of adenoviral, adeno-associated virus (AAV), and lentiviral vectors to treat ciliopathies across different organ systems and application toward the olfactory system. Thus far, adenoviral and AAVmeditated ciliary restoration demonstrated successful proof-of-principle preclinical studies. In addition, gene editing, ex vivo gene therapy, and transplantation could serve as alternative therapeutic and long-term approaches. But for all approaches, additional assessment of vector immunogenicity, specificity, and efficacy need further investigation. Currently, ciliopathy treatments are limited to symptomatic management with no curative options. However, the accessibility and amenability of the olfactory system to treatment would facilitate development and advancement of a viable therapy.

CONCLUSION

The findings of this review highlight the contribution of ciliopathies to a growing list of congenial olfactory dysfunctions. Promising results from other organ systems imply the feasibility of biologics, with results from gene therapies proving to be a viable therapeutic option for ciliopathies and olfactory dysfunction.

Intranasal Delivery of Adenoviral and AAV Vectors for Transduction of the Mammalian Peripheral Olfactory System

Intranasal delivery of solutions is a straightforward methodology for viral vector transduction and gene transfer to the epithelia within the nasal cavity. Beyond the simplicity of the technique, intranasal delivery has demonstrated restricted transduction of the olfactory and respiratory epithelial tissues. Here we outline the procedure of viral vector intranasal delivery in early postnatal and adult mice, as well as adult rats. The procedure allows for robust transduction and ectopic gene delivery that can be used for the visualization of cellular structures, protein distribution, and assessment of viral vector-mediated therapies.

FGFR3-TACC3 is an oncogenic fusion protein in respiratory epithelium

Structural rearrangements of the genome can drive lung tumorigenesis through the generation of fusion genes with oncogenic properties. Advanced genomic approaches have identified the presence of a genetic fusion between fibroblast growth factor receptor 3 (FGFR3) and transforming acidic coiled-coil 3 (TACC3) in non-small cell lung cancer (NSCLC), providing a novel target for FGFR inhibition. To interrogate the functional consequences of the FGFR3-TACC3 fusion in the transformation of lung epithelial cells, we generated a novel transgenic mouse model that expresses FGFR3-TACC3 concomitant with loss of the p53 tumor suppressor gene. Intra-nasal delivery of an Ad5-CMV-Cre virus promoted seromucinous glandular transformation of olfactory cells lining the nasal cavities of FGFR3-TACC3 (LSL-F3T3) mice, which was further accelerated upon loss of p53 (LSL-F3T3/p53). Surprisingly, lung tumors failed to develop in intra-nasally infected LSL-F3T3 and LSL-F3T3/p53 mice. In line with these observations, we demonstrated that intra-nasal delivery of Ad5-CMV-Cre induces widespread Cre-mediated recombination in the olfactory epithelium. Intra-tracheal delivery of Ad5-CMV-Cre into the lungs of LSL-F3T3 and LSL-F3T3/p53 mice however, resulted in the development of lung adenocarcinomas. Taken together, these findings provide in vivo evidence for an oncogenic function of FGFR3-TACC3 in respiratory epithelium.

Engineered mitochondrial ferritin as a magnetic resonance imaging reporter in mouse olfactory epithelium

We report the design of a MRI reporter gene with applications to non-invasive molecular imaging. We modified mitochondrial ferritin to localize to the cell cytoplasm. We confirmed the efficient cellular processing of this engineered protein and demonstrated high iron loading in mammalian cells. The reporter’s intracellular localization appears as distinct clusters that deliver robust MRI contrast. We used this new reporter to image in vivo and ex vivo the gene expression in native olfactory sensory neurons in the mouse epithelium. This robust MRI reporter can facilitate the study of the molecular mechanisms of olfaction and to monitor intranasal gene therapy delivery, as well as a wide range of cell tracking and gene expression studies in living subjects.

A new approach with less damage: intranasal delivery of tetracycline-inducible replication-defective herpes simplex virus type-1 vector to brain

Gene therapy holds great potential for treating neurological disorders. However, delivering gene vectors to the brain has been either invasive or inefficacious in most studies to date. The aim of this study was to develop a safe and efficacious strategy for delivering gene vectors to the brain. A tetracycline-inducible replication-defective herpes simplex virus type-1 vector, QR9TO-LacZ, was administered to rats intranasally. QR9TO-LacZ could infect primary cortical neurons and express the reporter gene without detectable replication. QR9TO-LacZ was observed in the olfactory bulb, hippocampus, striatum, cortex, medulla, cerebellum, ventricles, and nasal septum after intranasal administration. Expression of the reporter gene could be controlled effectively by tetracycline. In vitro, introduction of QR9TO-LacZ did not change the structure of transfected neurons. In vivo, QR9TO-LacZ did not increase apoptosis in neurons and did not alter levels of interleukin 6 and tumor necrosis factor α in the brain after intranasal delivery. Our data suggest that intranasally applied QR9TO-LacZ has a wide distribution and expresses the reporter gene in the brain under the control of tetracycline with less cytotoxicity than intravenous or stereotactic delivery methods.

Intranasal delivery of therapeutic proteins for neurological diseases

INTRODUCTION

Among the range of therapeutic protein candidates for new generation treatments of neurological diseases, neurotrophic factors and recombinant antibodies hold the greatest potential. However, major difficulties in their safe and effective delivery to the brain severely limit these applications. The BBB restricts the exchange of proteins between the plasma and the CNS. Moreover, therapeutic proteins often need to be selectively targeted to the brain, while minimizing their biodistribution to systemic compartments, to avoid peripheral side effects. The intranasal delivery of proteins has recently emerged as a non-invasive, safe and effective method to target proteins to the CNS, bypassing the BBB and minimizing systemic exposure.

AREAS COVERED

We critically summarize the main experimental and mechanistic facts about the simple and non-invasive nasal delivery approach, which provides a promising strategy and a potential solution for the severe unmet medical need of safely and effectively delivering protein therapeutics to the brain.

EXPERT OPINION

The intranasal route for the effective delivery of recombinant therapeutic proteins represents an emerging and promising non-invasive strategy. Future studies will achieve a detailed understanding of pharmacokinetic and mechanisms of delivery to optimize formulations and fully exploit the nose-to-brain interface in order to deliver proteins for the treatment of neurological diseases. This expanding research area will most likely produce exciting results in the near future towards new therapeutical approaches for the CNS.

Lentivirus-mediated genetic manipulation and visualization of olfactory sensory neurons in vivo

Development of a precise olfactory circuit relies on accurate projection of olfactory sensory neuron (OSN) axons to their synaptic targets in the olfactory bulb (OB). The molecular mechanisms of OSN axon growth and targeting are not well understood. Manipulating gene expression and subsequent visualizing of single OSN axons and their terminal arbor morphology have thus far been challenging. To study gene function at the single cell level within a specified time frame, we developed a lentiviral based technique to manipulate gene expression in OSNs in vivo. Lentiviral particles are delivered to OSNs by microinjection into the olfactory epithelium (OE). Expression cassettes are then permanently integrated into the genome of transduced OSNs. Green fluorescent protein expression identifies infected OSNs and outlines their entire morphology, including the axon terminal arbor. Due to the short turnaround time between microinjection and reporter detection, gene function studies can be focused within a very narrow period of development. With this method, we have detected GFP expression within as few as three days and as long as three months following injection. We have achieved both over-expression and shRNA mediated knock-down by lentiviral microinjection. This method provides detailed morphologies of OSN cell bodies and axons at the single cell level in vivo, and thus allows characterization of candidate gene function during olfactory development.

Effect of intranasal administration of basic fibroblast growth factor on olfactory epithelium

To further study the effects of basic fibroblast growth factor (bFGF) on the olfactory epithelium, bFGF was intranasally administered twice a day for 6 weeks to 2.5-month-old and 7-month-old mice. The effects were immunohistochemically examined by using antibodies against proliferating cell nuclear antigen, olfactory marker protein, and GAP43. The number of cells positive for proliferating cell nuclear antigen in the supporting cell layer increased dramatically, and that of GAP43-positive cells, or globose basal cells, increased significantly, especially in aging mice. However, no significant changes were observed in the number of olfactory marker protein-positive cells or mature olfactory receptor neurons. These results suggest that topical application of bFGF promotes proliferation of globose basal cells and supporting cells.

Strategies to overcome host immunity to adenovirus vectors in vaccine development

The first clinical evaluations of adenovirus (Ad)-based vectors for gene therapy were initiated in the mid-1990s and led to great anticipation for future utility. However, excitement surrounding gene therapy, particularly Ad-based therapy, was diminished upon the death of Jesse Gelsinger, and recent discouraging results from the HIV vaccine STEP trial have brought efficacy and safety issues to the forefront again. Even so, Ad vectors are still considered among the safest and most effective vaccine vectors. Innate and pre-existing immunity to Ad mediate much of the acute toxicities and reduced therapeutic efficacies observed following vaccination with this vector. Thus, innovative strategies must continue to be developed to reduce Ad-specific antigenicity and immune recognition. This review provides an overview and critique of the most promising strategies, including results from preclinical trials in mice and nonhuman primates, which aim to revive the future of Ad-based vaccines.

Cell tracing techniques in stem cell transplantation

Pluripotent stem cells have shown great therapeutic promise because of their natural capacity to regenerate damaged tissue. Likewise, autologous stem cells or genetically modified stem cells have already been successfully applied in animal or clinical experimental studies including cardiopathy, diabetic disease, system lupus erythema, pancreatic disease, and liver disease. In these studies regarding stem cell transplants in different diseases, identifying the location of implanted cells and distinguishing them from endogenous cells is the first and most important step. Moreover, different tracing techniques were applied in different studies for their different sensitivity, dynamic range, convenience and reliability of their assays. Therefore, we will here review different tracing techniques and their applications in stem cell transplants, including both experiment studies and preclinical trials.

Organ distribution of transgene expression following intranasal mucosal delivery of recombinant replication-defective adenovirus gene transfer vector

It is believed that respiratory mucosal immunization triggers more effective immune protection than parenteral immunization against respiratory infection caused by viruses and intracellular bacteria. Such understanding has led to the successful implementation of intranasal immunization in humans with a live cold-adapted flu virus vaccine. Furthermore there has been an interest in developing effective mucosal-deliverable genetic vaccines against other infectious diseases. However, there is a concern that intranasally delivered recombinant viral-based vaccines may disseminate to the CNS via the olfactory tissue. Initial experimental evidence suggests that intranasally delivered recombinant adenoviral gene transfer vector may transport to the olfactory bulb. However, there is a lack of quantitative studies to compare the relative amounts of transgene products in the respiratory tract, lung, olfactory bulb and brain after intranasal mucosal delivery of viral gene transfer vector. To address this issue, we have used fluorescence macroscopic imaging, luciferase quantification and PCR approaches to compare the relative distribution of transgene products or adenoviral gene sequences in the respiratory tract, lung, draining lymph nodes, olfactory bulb, brain and spleen. Intranasal mucosal delivery of replication-defective recombinant adenoviral vector results in gene transfer predominantly in the respiratory system including the lung while it does lead to a moderate level of gene transfer in the olfactory bulb. However, intranasal inoculation of adenoviral vector leads to little or no viral dissemination to the major region of the CNS, the brain. These experimental findings support the efficaciousness of intranasal adenoviral-mediated gene transfer for the purpose of mucosal immunization and suggest that it may not be of significant safety concern.

Retrograde infection of precerebellar nuclei neurons by injection of a recombinant adenovirus into the cerebellar cortex of normal and reeler mice

The reeler mouse is an autosomal recessive mutant mouse caused by mutation of the reelin gene and characterized by cerebellar ataxia. To determine whether the distribution pattern of precerebellar nuclei neurons in the brainstem of the reeler mouse changes, we injected a small volume of a replication-defective recombinant adenovirus carrying E. coli beta-galactosidase (lacZ) into the cerebellar cortex of normal and reeler mice. Five days later, the mice were transcardially perfused by a fixative solution. X-gal staining of coronal or sagittal sections of the brainstem revealed that many origins for reticulocerebellar, cuneocerebellar, trigeminocerebellar, and pontocerebellar projections were retrogradely labeled, but only a few olivocerebellar neurons were labeled. Retrogradely labeled neurons in the lateral reticular nucleus tended to locate more laterally and be more condensed into a small compartment in the reeler compared with their normal counterparts. Retrogradely labeled neurons in the external cuneate nucleus were more dorsally shifted in the reeler mice compared with their normal counterparts. We could not find any differences between the normal and reeler mice in the distribution patterns of their trigeminocerebellar projection neurons. Retrogradely labeled pontocerebellar neurons in the basilar pons of the reeler mouse were reduced in number compared with their normal counterparts in addition to being more ventrally and laterally shifted. These findings strongly suggest that the migration of some precerebellar nuclei neurons from the rhombic lip to their final loci may be obstructed in the reeler mice.

Bibliography. Current world literature. Nose and paranasal sinuses

PURPOSE OF REVIEW

Patients with advanced head and neck cancer are being treated with chemo-radiotherapy, and life is being prolonged, with or without persistent disease, for longer than was previously. Hypercalcaemia may present in patients with advanced or disseminated head and neck cancer, and, as such, these patients may present to a larger variety of clinicians for advice concerning their symptoms and illness. Modes of presentation of hypercalcaemia and treatment strategies are reviewed.

RECENT FINDINGS

There were previously few large series of head and neck cancer patients diagnosed with hypercalcaemia, which may or may not have been related to their cancer being treated. Investigations, by way of blood/serum calcium level, may identify such patients. Patients with cancer-related hypercalcaemia have a poor prognosis, but many may respond temporarily to treatment when offered, with an improvement of their quality of life and death.

SUMMARY

Hypercalcaemia should and must be considered in all patients who have or possibly have a diagnosis of a head and neck cancer and who present unwell with symptoms of fatigue, lethargy and somnolence. Investigation must include serum calcium (corrected for serum albumin binding) and parathyroid hormone level. Patients may be treated by a combination of rehydration and bisulphonate therapy until the serum calcium is reduced to a level below 3 mmol/l. The majority of patients diagnosed with hypercalcaemia due to head and neck malignancy die of their diseases in the short term, but some may enjoy a prolongation of life with reasonable quality if diagnosed and treated aggressively.

Expression of Coxsackie-Adenovirus receptor (CAR) in the developing mouse olfactory system

Interest in manipulating gene expression in olfactory sensory neurons (OSNs) has led to the use of adenoviruses (AdV) as gene delivery vectors. OSNs are the first order neurons in the olfactory system and the initial site of odor detection. They are highly susceptible to adenovirus infection although the mechanism is poorly understood. The Coxsackie-Adenovirus receptor (CAR) and members of the integrin family have been implicated in the process of AdV infection in various systems. Multiple serotypes of AdV efficiently bind to the CAR, leading to entry and infection of the host cell by a mechanism that can also involve integrins. Cell lines that do not express CAR are relatively resistant, but not completely immune to AdV infection, suggesting that other mechanisms participate in mediating AdV attachment and entry. Using in situ hybridization and western blot analyses, we show that OSNs and olfactory bulbs (OB) of mice express abundant CAR mRNA at embryonic and neonatal stages, with progressive diminution during postnatal development. By contrast to the olfactory epithelium (OE), CAR mRNA is still present in the adult mouse OB. Furthermore, despite a similar postnatal decline, CAR protein expression in the OE and OB of mice continues into adulthood. Our results suggest that the robust AdV infection observed in the postnatal olfactory system is mediated by CAR and that expression of even small amounts of CAR protein as seen in the adult rodent, permits efficient AdV infection and entry. CAR is an immunoglobulin domain-containing protein that bears homology to cell-adhesion molecules suggesting the possibility that it may participate in organization of the developing olfactory system.

Bcl-2 expression mediated by Cre/loxP system in olfactory epithelium

To study the Bcl-2 expression mediated by the Cre/loxP recombination system and its effect on prevention of apoptosis in olfactory epithelium. Adenoviral vectors with cassette for Bcl-2 (AxCALNLBcl-2) and Cre recombinase (AxCANCre) were applied to mouse olfactory epithelium by intranasal instillation. The effect of exogenous Bcl-2 expression on prevention of apoptosis of olfactory receptor neurons was investigated using an apoptosis model induced by bulbectomy. The Bcl-2 product was expressed not only in the olfactory receptor neurons but also in the supporting cells. Although statistical analysis did not show significant difference, the number of apoptotic cells in the infected olfactory epithelium on post-bulbectomy day 2 was lower than that of control and the number of survived mature olfactory receptor neurons in the infected olfactory epithelium on post-bulbectomy day 5 was higher than that of control. Although further studies are required for clinical application, the results of our study suggest that this strategy may be able to deliver exogenous Bcl-2 for the treatment of degeneration of olfactory receptor neurons.