Parkinson's disease (PD) affects 1-2% of people over 65, causing significant morbidity across a progressive disease course. The classic PD motor deficits are caused by the degeneration of ...dopaminergic neurons in the substantia nigra pars compacta (SNpc), resulting in the loss of their long-distance axonal projections that modulate striatal output. While contemporary treatments temporarily alleviate symptoms of this disconnection, there is no approach able to replace the nigrostriatal pathway. We applied microtissue engineering techniques to create a living, implantable tissue-engineered nigrostriatal pathway (TE-NSP) that mimics the architecture and function of the native pathway. TE-NSPs comprise a discrete population of dopaminergic neurons extending long, bundled axonal tracts within the lumen of hydrogel micro-columns. Neurons were isolated from the ventral mesencephalon of transgenic rats selectively expressing the green fluorescent protein in dopaminergic neurons with subsequent fluorescent-activated cell sorting to enrich a population to 60% purity. The lumen extracellular matrix and growth factors were varied to optimize cytoarchitecture and neurite length, while immunocytochemistry and fast-scan cyclic voltammetry (FSCV) revealed that TE-NSP axons released dopamine and integrated with striatal neurons in vitro. Finally, TE-NSPs were implanted to span the nigrostriatal pathway in a rat PD model with a unilateral 6-hydroxydopamine SNpc lesion. Immunohistochemistry and FSCV established that transplanted TE-NSPs survived, maintained their axonal tract projections, extended dopaminergic neurites into host tissue, and released dopamine in the striatum. This work showed proof of concept that TE-NSPs can reconstruct the nigrostriatal pathway, providing motivation for future studies evaluating potential functional benefits and long-term durability of this strategy. This pathway reconstruction strategy may ultimately replace lost neuroarchitecture and alleviate the cause of motor symptoms for PD patients.
Each year in the USA, over 2.4 million people experience mild traumatic brain injury (TBI), which can induce long-term neurological deficits. The dentate gyrus of the hippocampus is notably ...susceptible to damage following TBI, as hilar mossy cell changes in particular may contribute to post-TBI dysfunction. Moreover, microglial activation after TBI may play a role in hippocampal circuit and/or synaptic remodeling; however, the potential effects of chronic microglial changes are currently unknown. The objective of the current study was to assess neuropathological and neuroinflammatory changes in subregions of the dentate gyrus at acute to chronic time points following mild TBI using an established model of closed-head rotational acceleration induced TBI in pigs.
This study utilized archival tissue of pigs which were subjected to sham conditions or rapid head rotation in the coronal plane to generate mild TBI. A quantitative assessment of neuropathological changes in the hippocampus was performed via immunohistochemical labeling of whole coronal tissue sections at 3 days post-injury (DPI), 7 DPI, 30 DPI, and 1 year post-injury (YPI), with a focus on mossy cell atrophy and synaptic reorganization, in context with microglial alterations (e.g., density, proximity to mossy cells) in the dentate gyrus.
There were no changes in mossy cell density between sham and injured animals, indicating no frank loss of mossy cells at the mild injury level evaluated. However, we found significant mossy cell hypertrophy at 7 DPI and 30 DPI in anterior (> 16% increase in mean cell area at each time; p = < 0.001 each) and 30 DPI in posterior (8.3% increase; p = < 0.0001) hippocampus. We also found dramatic increases in synapsin staining around mossy cells at 7 DPI in both anterior (74.7% increase in synapsin labeling; p = < 0.0001) and posterior (82.7% increase; p = < 0.0001) hippocampus. Interestingly, these morphological and synaptic alterations correlated with a significant change in microglia in proximity to mossy cells at 7 DPI in anterior and at 30 DPI in the posterior hippocampus. For broader context, while we found that there were significant increases in microglia density in the granule cell layer at 30 DPI (anterior and posterior) and 1 YPI (posterior only) and in the molecular layer at 1 YPI (anterior only), we found no significant changes in overall microglial density in the hilus at any of the time points evaluated post-injury.
The alterations of mossy cell size and synaptic inputs paired with changes in microglia density around the cells demonstrate the susceptibility of hilar mossy cells after even mild TBI. This subtle hilar mossy cell pathology may play a role in aberrant hippocampal function post-TBI, although additional studies are needed to characterize potential physiological and cognitive alterations.
Aggregated α-synuclein proteins form brain lesions that are hallmarks of neurodegenerative synucleinopathies, and oxidative stress has been implicated in the pathogenesis of some of these disorders. ...Using antibodies to specific nitrated tyrosine residues in α-synuclein, we demonstrate extensive and widespread accumulations of nitrated α-synuclein in the signature inclusions of Parkinson's disease, dementia with Lewy bodies, the Lewy body variant of Alzheimer's disease, and multiple system atrophy brains. We also show that nitrated α-synuclein is present in the major filamentous building blocks of these inclusions, as well as in the insoluble fractions of affected brain regions of synucleinopathies. The selective and specific nitration of α-synuclein in these disorders provides evidence to directly link oxidative and nitrative damage to the onset and progression of neurodegenerative synucleinopathies.
Despite increasing appreciation of the critical role that neuroinflammatory pathways play in brain injury and neurodegeneration, little is known about acute microglial reactivity following diffuse ...traumatic brain injury (TBI) — the most common clinical presentation that includes all concussions. Therefore, we investigated acute microglial reactivity using a porcine model of closed-head rotational velocity/acceleration-induced TBI that closely mimics the biomechanical etiology of inertial TBI in humans. We observed rapid microglial reactivity within 15min of both mild and severe TBI. Strikingly, microglial activation was restrained to regions proximal to individual injured neurons – as denoted by trauma-induced plasma membrane disruption – which served as epicenters of acute reactivity. Single-cell quantitative analysis showed that in areas free of traumatically permeabilized neurons, microglial density and morphology were similar between sham or following mild or severe TBI. However, microglia density increased and morphology shifted to become more reactive in proximity to injured neurons. Microglial reactivity around injured neurons was exacerbated following repetitive TBI, suggesting further amplification of acute neuroinflammatory responses. These results indicate that neuronal trauma rapidly activates microglia in a highly localized manner, and suggest that activated microglia may rapidly influence neuronal stability and/or pathophysiology after diffuse TBI.
•Microglia responded to localized neuronal injury within minutes of closed-head TBI.•Rapid activation was only appreciable in regions exhibiting permeabilized neurons.•Microglia reactivity was exacerbated following repetitive TBI.•This gyrencephalic injury model closely replicates biomechanics of clinical TBI.•Acute inflammation may influence pathophysiology following concussion in humans.
Intracytoplasmic inclusions composed of α‐synuclein (α‐syn) are characteristic of neurodegenerative Lewy body disorders. Using novel monoclonal antibodies raised against altered α‐syn, we uncovered ...an unprecedented and extensive burden of α‐syn pathology in the striatum of Lewy body disorders. The highest density of striatal pathology was observed in patients with a combination of Alzheimer's disease and dementia with Lewy bodies or pure dementia with Lewy bodies, and these α‐syn aggregates may contribute to the parkinsonism seen in these disorders.
Parkinson's disease (PD) is the second most common progressive neurodegenerative disease, affecting 1-2% of people over 65. The classic motor symptoms of PD result from selective degeneration of ...dopaminergic neurons in the substantia nigra pars compacta (SNpc), resulting in a loss of their long axonal projections to the striatum. Current treatment strategies such as dopamine replacement and deep brain stimulation (DBS) can only minimize the symptoms of nigrostriatal degeneration, not directly replace the lost pathway. Regenerative medicine-based solutions are being aggressively pursued with the goal of restoring dopamine levels in the striatum, with several emerging techniques attempting to reconstruct the entire nigrostriatal pathway-a key goal to recreate feedback pathways to ensure proper dopamine regulation. Although many pharmacological, genetic, and optogenetic treatments are being developed, this article focuses on the evolution of transplant therapies for the treatment of PD, including fetal grafts, cell-based implants, and more recent tissue-engineered constructs. Attention is given to cell/tissue sources, efficacy to date, and future challenges that must be overcome to enable robust translation into clinical use. Emerging regenerative medicine therapies are being developed using neurons derived from autologous stem cells, enabling the construction of patient-specific constructs tailored to their particular extent of degeneration. In the upcoming era of restorative neurosurgery, such constructs may directly replace SNpc neurons, restore axon-based dopaminergic inputs to the striatum, and ameliorate motor deficits. These solutions may provide a transformative and scalable solution to permanently replace lost neuroanatomy and improve the lives of millions of people afflicted by PD.
Since brain stem regions associated with early Parkinson’s disease (PD) pathology encroach upon those involved in taste function, the ability to taste may be compromised in PD. However, studies on ...this point have been contradictory. We administered well-validated whole-mouth and regional taste tests that incorporated multiple concentrations of sucrose, citric acid, caffeine, and sodium chloride to 29 early stage PD patients and 29 age-, sex-, and race-matched controls. Electrogustometry was also performed on the anterior tongue. The PD cohort was tested both on and off dopamine-related medications in counterbalanced test sessions. While whole-mouth taste identification test scores for all stimuli were, on average, nominally lower for the PD patients than for the controls, a trend in the opposite direction was noted for the intensity ratings at the lower stimulus concentrations for all stimuli except caffeine. Moreover, regional testing found that PD subjects tended to rate the stimuli, relative to the controls, as more intense on the anterior tongue and less intense on the posterior tongue. No significant associations were evident between taste test scores and UPDRS scores, L-DOPA medication equivalency values, or
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TcTRODAT-1 SPECT imaging of dopamine transporter uptake within the striatum and associated regions. Our findings suggest that suprathreshold measures of taste function are influenced by PD and that this disease differentially influences taste function on anterior (CN VII) and posterior (CN IX) tongue regions. Conceivably PD-related damage to CN IX releases central inhibition on CN VII at the level of the brainstem, resulting in enhanced taste intensity on the anterior tongue.
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