Geometric Cuts by an Autonomous Laser Osteotome Increase Stability in Mandibular Reconstruction With Free Fibula Grafts: A Cadaver Study.

BACKGROUND: Nonunion and plate exposure represent a major complication after mandibular reconstruction with free fibula flaps. These drawbacks may be resolved by geometric osteotomies increasing intersegmental bone contact area and stability. PURPOSE: The aim of this study was to compare intersegmental bone contact and stability of geometric osteotomies to straight osteotomies in mandibular reconstructions with free fibula grafts performed by robot-guided erbium-doped yttrium aluminum garnet laser osteotomy. STUDY DESIGN, SETTING, SAMPLE: This cadaveric in-vitro study was performed on fresh frozen human skull and fibula specimens. Computed tomography (CT) scans of all specimens were performed for virtual planning of mandibular resections and three-segment fibula reconstructions. The virtual planning was implemented in a Cold Ablation Robot-guided Laser Osteotome. PREDICTOR/EXPOSURE/INDEPENDENT VARIABLE: For predictor variables, straight and geometric puzzle-shaped osteotomies were designed at resection of the mandible and corresponding fibula reconstruction. MAIN OUTCOME VARIABLES: The primary outcome variable was the stability of the reconstructed mandible investigated by shearing tests. Moreover, secondary outcome variables were the duration of the laser osteotomies, the contact surface area, and the accuracy of the reconstruction, both evaluated on postsurgical CT scans. COVARIATES: Covariables were not applicable. ANALYSES: Data were reported as mean values (± standard deviation) and were statistically analyzed using an independent-sample t-test at a significance level of α = 0.05. Root mean square deviation was tested for accuracy. RESULTS: Eight skulls and 16 fibula specimens were used for the study. One hundred twelve successful laser osteotomies (96 straight and 16 geometrical) could be performed. Geometric osteotomies increased stability (110.2 ± 36.2 N vs 37.9 ± 20.1 N, P < .001) compared to straight osteotomies. Geometric osteotomy of the fibula took longer than straight osteotomies (10.9 ± 5.1 min vs 5.9 ± 2.2 min, P = .028) but could provide larger contact surface (431.2 ± 148.5 mm2 vs 226.1 ± 50.8 mm2, P = .04). Heat map analysis revealed a mean deviation between preoperational planning and postreconstructive CT scan of -0.8 ± 2.4 mm and a root mean square deviation of 2.51 mm. CONCLUSION AND RELEVANCE: Mandibular resection and reconstruction by fibula grafts can be accurately performed by a Cold Ablation Robot-guided Laser Osteotome without need for cutting guides. Osteotomy planning with geometric cuts offers higher stability and an increased bone contact area, which may enhance healing of the reconstructed mandible.

Down-phase auditory stimulation is not able to counteract pharmacologically or physiologically increased sleep depth in traumatic brain injury rats.

Modulation of slow-wave activity, either via pharmacological sleep induction by administering sodium oxybate or sleep restriction followed by a strong dissipation of sleep pressure, has been associated with preserved posttraumatic cognition and reduced diffuse axonal injury in traumatic brain injury rats. Although these classical strategies provided promising preclinical results, they lacked the specificity and/or translatability needed to move forward into clinical applications. Therefore, we recently developed and implemented a rodent auditory stimulation method that is a scalable, less invasive and clinically meaningful approach to modulate slow-wave activity by targeting a particular phase of slow waves. Here, we assessed the feasibility of down-phase targeted auditory stimulation of slow waves and evaluated its comparative modulatory strength in relation to the previously employed slow-wave activity modulators in our rat model of traumatic brain injury. Our results indicate that, in spite of effectively reducing slow-wave activity in both healthy and traumatic brain injury rats via down-phase targeted stimulation, this method was not sufficiently strong to counteract the boost in slow-wave activity associated with classical modulators, nor to alter concomitant posttraumatic outcomes. Therefore, the usefulness and effectiveness of auditory stimulation as potential standalone therapeutic strategy in the context of traumatic brain injury warrants further exploration.

Slow-wave sleep affects synucleinopathy and regulates proteostatic processes in mouse models of Parkinson's disease.

Slow-wave sleep (SWS) modulation in rodent models of Alzheimer's disease alters extracellular amyloid burden. In Parkinson's disease (PD), SWS appears to be closely linked with disease symptoms and progression. PD is characterized by damaging intracellular α-synuclein (αSyn) deposition that propagates extracellularly, contributing to disease spread. Intracellular αSyn is sensitive to degradation, whereas extracellular αSyn may be eliminated by glymphatic clearance, a process increased during SWS. Here, we explored whether long-term slow-wave modulation in murine models of PD presenting αSyn aggregation alters pathological protein burden and, thus, might constitute a valuable therapeutic target. Sleep-modulating treatments showed that enhancing slow waves in both VMAT2-deficient and A53T mouse models of PD reduced pathological αSyn accumulation compared to control animals. Nonpharmacological sleep deprivation had the opposite effect in VMAT2-deficient mice, severely increasing the pathological burden. We also found that SWS enhancement was associated with increased recruitment of aquaporin-4 to perivascular sites, suggesting a possible increase of glymphatic function. Furthermore, mass spectrometry data revealed differential and specific up-regulation of functional protein clusters linked to proteostasis upon slow wave­enhancing interventions. Overall, the beneficial effect of SWS enhancement on neuropathological outcome in murine synucleinopathy models mirrors findings in models of Alzheimer. Modulating SWS might constitute an effective strategy for modulating PD pathology in patients.

Improved functional and histochemical outcomes in l-DOPA plus tolcapone treated VMAT2-deficient mice.

Parkinson disease is typically treated with L-3,4-dihydroxyphenylalanine (or levodopa) co-prescribed with concentration stabilizers to prevent undesired motor fluctuations. However, the beneficial role of the chronic combined therapy on disease progression has not been thoroughly explored. We hypothesized that tolcapone, a catechol-O-methyl-transferase inhibitor, co-administered with levodopa may offer beneficial long-term disease-modifying effects through its dopamine stabilization actions. Here, we followed vesicular monoamine transporter 2-deficient and wild-type mice treated twice daily per os with vehicle, levodopa (20 mg/kg), tolcapone (15 mg/kg) or levodopa (12.5 mg/kg) + tolcapone (15 mg/kg) for 17 weeks. We assessed open field, bar test and rotarod performances at baseline and every 4th week thereafter, corresponding to OFF-medication weeks. Finally, we collected coronal sections from the frontal caudate-putamen and determined the reactivity level of dopamine transporter. Vesicular monoamine transporter 2-deficient mice responded positively to chronic levodopa + tolcapone intervention in the bar test during OFF-periods. Neither levodopa nor tolcapone interventions offered significant improvements on their own. Similarly, chronic levodopa + tolcapone intervention was associated with partially rescued dopamine transporter levels, whereas animals treated solely with levodopa or tolcapone did not present this effect. Interestingly, 4-month progression of bar test scores correlated significantly with dopamine-transporter-label density. Overall, we observed a moderate functional and histopathological improvement effect by chronic dopamine replacement when combined with tolcapone in vesicular monoamine transporter 2-deficient mice. Altogether, chronic stabilization of dopamine levels by catechol-O-methyl-transferase inhibition, besides its intended immediate actions, arises as a potential long-term beneficial approach during the progression of Parkinson disease.

Increased Sleep Need and Reduction of Tuberomammillary Histamine Neurons after Rodent Traumatic Brain Injury.

Although sleep-wake disturbances are prevalent and well described after traumatic brain injury, their pathophysiology remains unclear, most likely because human traumatic brain injury is a highly heterogeneous entity that makes the systematic study of sleep-wake disturbances in relation to trauma-induced histological changes a challenging task. Despite increasing interest, specific and effective treatment strategies for post-traumatic sleep-wake disturbances are still missing. With the present work, therefore, we aimed at studying acute and chronic sleep-wake disturbances by electrophysiological means, and at assessing their histological correlates after closed diffuse traumatic brain injury in rats with the ultimate goal of generating a model of post-traumatic sleep-wake disturbances and associated histopathological findings that accurately represents the human condition. We assessed sleep-wake behavior by means of standard electrophysiological recordings before and 1, 7, and 28 days after sham or traumatic brain injury procedures. Sleep-wake findings were then correlated to immunohistochemically labeled and stereologically quantified neuronal arousal systems. Compared with control animals, we found that closed diffuse traumatic brain injury caused increased sleep need one month after trauma, and sleep was more consolidated. As histological correlate, we found a reduced number of histamine immunoreactive cells in the tuberomammillary nucleus, potentially related to increased neuroinflammation. Monoaminergic and hypocretinergic neurotransmitter systems in the hypothalamus and rostral brainstem were not affected, however. These results suggest that our rat traumatic brain injury model reflects human post-traumatic sleep-wake disturbances and associated histopathological findings very accurately, thus providing a study platform for novel treatment strategies for affected patients.

Preliminary Evidence of Apathetic-Like Behavior in Aged Vesicular Monoamine Transporter 2 Deficient Mice.

Apathy is considered to be a core feature of Parkinson's disease (PD) and has been associated with a variety of states and symptoms of the disease, such as increased severity of motor symptoms, impaired cognition, executive dysfunction and dementia. Apart from the high prevalence of apathy in PD, which is estimated to be about 40%, the underlying pathophysiology remains poorly understood and current treatment approaches are unspecific and proved to be only partially effective. In animal models, apathy has been sub-optimally modeled, mostly by means of pharmacological and stress-induced methods, whereby concomitant depressive-like symptoms could not be ruled out. In the context of PD only a few studies on toxin-based models (i.e., 6-hydroxydopamine (6-OHDA) or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)) claimed to have determined apathetic symptoms in animals. The assessment of apathetic symptoms in more elaborated and multifaceted genetic animal models of PD could help to understand the pathophysiological development of apathy in PD and eventually advance specific treatments for afflicted patients. Here we report the presence of behavioral signs of apathy in 12 months old mice that express only ~5% of the vesicular monoamine transporter 2 (VMAT2). Apathetic-like behavior in VMAT2 deficient (LO) mice was evidenced by impaired burrowing and nest building skills, and a reduced preference for sweet solution in the saccharin preference test, while the performance in the forced swimming test was normal. Our preliminary results suggest that VMAT2 deficient mice show an apathetic-like phenotype that might be independent of depressive-like symptoms. Therefore VMAT2 LO mice could be a useful tool to study the pathophysiological substrates of apathy and to test novel treatment strategies for apathy in the context of PD.

Sleep Modulation Alleviates Axonal Damage and Cognitive Decline after Rodent Traumatic Brain Injury.

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. It produces diffuse axonal injury (DAI), which contributes to cognitive impairment, but effective disease-modifying treatment strategies are missing. We have recently developed a rat model of closed skull TBI that reproduces human TBI consequences, including DAI and clinical sequelae such as memory impairment. Here, we investigated whether sleep modulation after trauma has an impact on DAI and memory outcome. We assessed cognition with the novel object recognition test and stained for amyloid precursor protein, a DAI marker. We found that both sleep induction and restriction acutely after TBI enhanced encephalographic slow-wave activity, markedly reduced diffuse axonal damage in the cortex and hippocampus, and improved memory impairment 2 weeks after trauma. These results suggest that enhancing slow-wave sleep acutely after trauma may have a beneficial disease-modifying effect in subjects with acute TBI. SIGNIFICANCE STATEMENT: Traumatic brain injury (TBI) is a clinically important entity. Cognitive deficits belong to the most prevalent chronic posttraumatic symptoms, most likely due to diffuse axonal injury (DAI). A growing body of evidence suggests a role of sleep in the clearance of waste products in the brain, possibly including amyloid precursor protein (APP), a marker of DAI. In this study, we provide evidence that enhancement of slow-wave oscillatory activity in the delta-frequency range decreases the APP-immunoreactivity and preserves cognitive abilities after trauma, potentially offering novel, noninvasive treatment options for traumatic injury.

Novel Rat Model of Weight Drop-Induced Closed Diffuse Traumatic Brain Injury Compatible with Electrophysiological Recordings of Vigilance States.

Traumatic brain injury (TBI) is a major cause of persistent disabilities such as sleep-wake disorders (SWD). Rodent studies of SWD after TBI are scarce, however, because of lack of appropriate TBI models reproducing acceleration-deceleration forces and compatible with electroencephalography/myography (EEG/EMG)-based recordings of vigilance states. We therefore adapted the Marmarou impact acceleration model to allow for compatibility with EEG-headset implantation. After implantation of EEG/EMG electrodes, we induced closed TBI by a frontal, angular hit with a weight-drop device (56 rats, weight 2500 g, fall height 25 cm). Subsequently, we tested our model's usefulness for long-term studies on a behavioral, electrophysiological, and histological level. Neurological, motor, and memory deficits were assessed with the neurological severity score, open field, and novel object recognition tests, respectively. EEG/EMG recordings were performed in both Sham (n = 7) and TBI (n = 7) rats before and 1, 7, and 28 days after trauma to evaluate sleep-wake proportions and post-traumatic implant stability. Histological assessments included hematoxylin and eosin staining for parenchymal damage and hemorrhage and amyloid precursor protein staining for diffuse axonal damage. All rats survived TBI without major neurological or motor deficits. Memory function was impaired after TBI at weeks 1, 2, and 3 and recovered at week 4. EEG implants were stable for at least 1 month and enabled qualitative and quantitative sleep analyses. Histological assessments revealed no major bleedings or necrosis but intense diffuse axonal damage after TBI. This approach fulfills major pre-conditions for experimental TBI models and offers a possibility to electrophysiologically study behavioral states before and after trauma.

The effects of muscimol and AMN082 injections into the medial prefrontal cortex on the expression and extinction of conditioned fear in mice.

The medial prefrontal cortex (mPFC), in particular its infralimbic part, is a key region in mediating the extinction of conditioned fear. There is some evidence that the metabotropic glutamate receptor 7 (mGluR7) may be involved in the mediation or modulation of extinction. The aim of present study was to assess the potential role of mGluR7 in the mPFC in the extinction of conditioned fear in mice by local injections of AMN082, a positive allosteric modulator of mGluR7. Furthermore, for comparison we injected the GABA-A receptor agonist muscimol, which should lead to a temporary inactivation of mPFC. We found impaired between-session extinction of conditioned fear for the muscimol group as well as a decrease in fear expression. However, local injections of AMN082 into the mPFC had no effects. Overall, the results of the experiment add to a growing body of evidence that mPFC, especially the infralimbic region, is crucial in the extinction of fear memory.