Abstract

Dendritic Cells Are Specialized Antigen Presenting Cells to Control Antigen Specific Foxp3⁺ Regulatory T Cells

Sayuri Yamazaki

Regulatory T cells (T reg) belong to a subpopulation of CD4⁺ lymphocytes that express the Foxp3 transcription factor, high affinity IL-2R (CD25) and suppress the development of autoimmunity, allergy and transplantation rejection. T reg can be divided into at least 2 types; i) Natural T reg: thymic-derived naturally occurring Foxp3⁺CD25⁺CD4⁺ T reg and ii) Induced T reg: Foxp3⁺CD25⁺CD4⁺ T reg derived from Foxp3^-CD25^-CD4⁺ T cells in the periphery through TGF-β. To treat unwanted immune responses without global immune suppression, it is crucial to understand how to control the antigen specificity of these 2 types of T reg. Natural T reg are usually anergic and non-proliferative upon T cell receptor stimulation ex vivo, however, we found that these natural T reg can be expanded when they are cultured with mature antigen presenting dendritic cells (DC). The DC-expanded T reg suppress type 1 diabetes in non-obese diabetic mice and graft versus host disease in an antigen specific manner. Recently, we have identified a subset of DC (CD8⁺, DEC205⁺) that has a critical role in inducing antigen-specific Foxp3⁺ T reg from a non-regulatory Foxp3^-CD25^-CD4⁺ population in vitro and in vivo. I will further investigate the mechanism, by which these specialized DC regulate the generation of induced T reg. This finding may contribute to the development of a novel immune therapies using antigen-specific T reg educated by DC.

Gene Therapy and Cell Replacement Therapy

Sho Kanzaki

The most common type of hearing loss in humans results from damage to the inner ear, including hair cells (HCs) damages and auditory neurons degeneration. In mammals, cochlear HC loss causes irreversible hearing impairment because this type of sensory cell cannot regenerate. The regeneration or protection of SGN has implications for cochlear implant to alleviate deafness. We provided the two types of injection approaches into inner ear using viral vectors. Sendai virus vectors (SeV) or RNA virus, has less genotoxicity and can be transfected with HCs and supporting cells (SCs) or progenitors, suggesting that SeV meditated Atoh 1 transgene overexpression may regenerate new HCs. Gene therapy into inner ear would be another implication for genetic hearing loss. We reported that adeno-associate virus vectors (AAV) can transduce HCs, SCs in immature mice inner ear (postnasal day1) with atraumatic approach. We also demonstrated that bone marrow mesenchymal stem cells derived neural stem cells can survive, migrate and differentiate in guinea pigs inner ear. In addition, we successfully established that in vivo magnetic resonance image (MRI) system in detection of stem cells labeled with superparamagnetic iron oxide nanoparticles. These results suggest that gene and cell therapy could provide the future treatment alternative for hearing loss or inner ear diseases.

How Do Specializations of Vestibular Hair Cells
and Primary Afferent Neurons Shape Vestibular Signals?

Ruth Anne Eatock

Head movements deflect the mechanosensitive hair bundles of vestibular hair cells, evoking electrical signals. The hair cells transmit the signals across synaptic contacts with fibers of the eighth nerve, which carry the signals to the brain. The signals contribute to our sense of orientation in space and drive reflexes that move the eyes, head and body to compensate for head movements. Without such compensatory reflexes, the visual world would move with every step you take. Indeed, damage to vestibular hair cells and afferents may be a significant cause of balance and mobility defects in patients, especially the elderly. Understanding vestibular dysfunction requires analysis of the mechanisms underlying normal function of the vestibular hair cells and neurons.
Vestibular organs of higher vertebrates - mammals, birds and reptiles - have several special properties that make them interesting from a neurobiological perspective. First, they have central and peripheral zones that are anatomically and physiologically distinct. (In the otolith organs, the analogous zones are called the striola and extrastriola.) In response to sinusoidal head movements, vestibular afferents from central/striolar zones have gains that rise with frequency and phases that lead the stimulus, whereas afferents from peripheral/extrastriolar zones tend to show less filtering. Other measures such as mutual information density reveal other differences in stimulus processing between the two zones. These differences may reflect between-zone differences at all levels of stimulus processing, including differences in: otoconial and gel layers of the accessory structures; hair bundles; electrical properties of hair cells; synaptic transmission; morphology of the afferent terminals; and intrinsic electrical properties and calcium binding proteins of the afferent neurons. Central/striolar afferent neurons also have the largest diameters and therefore the fastest conduction velocities.
A second special property of the vestibular organs of higher vertebrates is the presence of a unique receptor: the type I hair cell. Type I hair cells were first recognized anatomically by the form of the afferent ending. For most hair cells, eighth-nerve fibers contact hair cells with small, button-shaped (bouton) nerve endings. For the type I hair cell, in contrast, the nerve ending is an elaborate, cup-shaped structure (calyx) that wraps much of the cell. More recently it has become clear that type I hair cells also have a distinctive set of ion channels which shape their receptor potentials. In birds and reptiles, type I cells and calyx endings are confined to central zones; in mammals, type I cells and calyx endings are found everywhere in the sensory epithelium, but differ anatomically between zones. The restriction of type I hair cells to higher vertebrates suggests that they serve specific roles in compensating the head movements of reptiles and their descendants. Unlike fish and amphibians, these animals have necks that permit independent head movements, which may be as a result relatively large and/or fast.
A third special property of the vestibular system in all species, but especially mammals, is the wide range in regularity of firing of vestibular afferent neurons. Vestibular afferents from the central/striolar zones tend to have highly irregular inter-spike intervals; in this property, they resemble auditory afferents. Vestibular afferents from the periphery/extrastriola, in contrast, have highly regular inter-spike intervals. This difference may influence the encoding properties of neurons innervating the two zones. Regularity differences may reflect the detailed morphology of synaptic endings and terminal branches and the intrinsic ion channel properties of the afferent fibers.
In summary, the vestibular organs of higher vertebrates, including humans, have distinct zones. Afferents emanating from the central/striolar zones favor higher frequency head motions, have more irregular inter-spike intervals, and convey signals at greater speeds than peripheral/extrastriolar afferents. Such properties may specialize the central and striolar zones for fast motion signals and may arise through multiple specializations of accessory structures, hair cells and afferent neurons. Understanding the separate roles of central and peripheral zones has clinical relevance, given evidence that afferent signals from central and striolar zones are the most vulnerable to ototoxic insult and deterioration with aging.

Initiating Treatment in Parkinson's Disease: the Challenges

Anthony E. Lang

There are many controversies in the management of Parkinson's disease (PD). The questions of when and how to start treatment are particularly challenging. A number of different treatment- and patient-related factors must be taken into account when making these decisions. Ideally, neuroprotective therapy would be started at the time of diagnosis. However, no treatment has been unequivocally shown to modify disease progression, and those that have some evidence for this effect all provide confounding symptomatic benefits, which may also be important to supplement faltering compensatory mechanisms within the basal ganglia. The delayed start design, as utilized in the rasagiline ADAGIO trial, potentially could eliminate or minimize this confound however this remains unproven and it is unclear how to best explain the outcome of this trial with 1 mg meeting the necessary endpoints but 2 mg not. Dopamine agonists have been convincingly shown to be associated with a reduction in the incidence of dyskinesias in the first five years of treatment, however, this is at a time when dyskinesias are typically not terribly bothersome or disabling and it is uncertain that this early advantage translates into long-term benefits. In addition, a number of non-motor side effects are more frequently associated with dopamine agonists than with levodopa. This lecture will review the issues that impact on treatment decisions in early Parkinson's disease highlighting the various outstanding controversies or uncertainties that vex this challenging field.

The Fate of Gastric Epithelial Cells during Infection with Helicobacter pylori: From Birth to Death and Back

Peter B. Ernst, Keiran A. Ryan, Alice H. Berger, Daeho Park, James E. Casanova, Kodi Ravichandran, Phil D. Smith, Lesley Smythies, Diane Bimczok and Soumita Das

The gastrointestinal epithelium is renewed every 7-10 days. In response to infection or inflammation, epithelial cell turnover is increased. Apoptosis of gastric epithelial cells is induced byH. pylori alone, pro-inflammatory cytokines or the combination of both. Phagocytosis of infected, apoptotic epithelial cells could be a mechanism for their clearance and may provide antigenic sampling that contributes to gastritis. The presence of phosphatidyl serine on the surface of apoptotic cells is a signal that initiates phagocytosis. To study the process of apoptotic cell engulfment, apoptosis was induced in a gastric epithelial cell line (AGS) by H. pylori infection or chemically using camptothecin. Macrophages preferentially recognized and bound apoptotic AGS cells leading to their engulfment. Diminished binding and engulfment by macrophages after Annexin V pretreatment underscored the requirement of phosphatidyl serine exposure on GECs during recognition. We investigated the role of specific phosphatidyl serine recognition structures on macrophages in the clearance of apoptotic AGS cells. These data identify phosphatidyl serine recognition and the BAI1 receptor as key components for the engulfment of human epithelial cells rendered apoptotic by H. pylori infection. As part of the contribution to epithelial cell turnover, it has been shown that bone marrow derived stem cells provide an epithelial cell stem cell that expands during inflammation. Epithelial cells that transform to become malignant appear to be derived from this pool of bone marrow-derived stem cells. This review will discuss the fate of epithelial cells in response to H. pylori infection and the local gastric inflammatory milieu.

What Are the Limits of Endoscopic Sinus Surgery?:
The Expanded Endonasal Approach to the Skull Base

Carl H. Snyderman, Ricardo L. Carrau, Daniel Prevedello, Paul Gardner
and Amin B. Kassam

The advent of endoscopic technologies and techniques has expanded the limits of conventional endoscopic sinus surgery. The expanded endonasal approach describes a series of surgical modules in the sagittal and coronal planes that allow surgical access to the entire ventral skull base. The sagittal plane extends from the frontal sinus to the second cervical vertebra. The coronal plane extends from the midline to the roof of the orbit, the floor of the middle cranial fossa, and the jugular foramen. Key principles of endonasal skull base surgery are choosing a surgical corridor that minimizes the need for neural and vascular manipulation, team surgery, use of the endoscope to enhance visualization, and bimanual tumor dissection under direct visualization. Particular challenges of the expanded endonasal approach are identification of anatomical structures using unfamiliar landmarks, hemostasis, and dural reconstruction. Over the last decade with more than 1000 completely endonasal skull base surgeries, we have demonstrated that endoscopic endonasal surgery of the skull base can be performed with minimal morbidity and mortality. The introduction of the septal mucosal flap for dural reconstruction has decreased the incidence of postoperative cerebrospinal fluid leaks to less than 5%. Early data suggests that oncological outcomes for malignant sinonasal tumors with skull base involvement are comparable to conventional techniques. Proper training in endonasal surgical techniques is essential to prevent unnecessary morbidity and achieve good outcomes.