United States

Background
Sensorimotor disruption can lead to many neurological disorders, thus the investigation of these cortical areas in animal models is paramount to learn more about their function. Here, we used optogenetics a biological tool to control activity of neurons and other cell types with light and a whisker discrimination task in mice. This invoked localized silencing of the Somatosensory (S1) and Motor (M1) cortices to demonstrate their involvement in the whisker discrimination task and thus deepen our understanding of cortical involvement in behavior. 

Methods
We used transgenic VGat-Chr2 mice, which expressed channelrhodopsin in inhibitory neurons. These inhibitory neurons can then be activated by light leading to localized silencing in targeted areas. The animals underwent a thinned-skull surgical procedure, where cranial windows were implanted over S1 and M1. The mice were then trained in a whisker-based go/no-go task that consisted of a direction discrimination, where one rotor direction is a distractor and the second is the important stimulus (Direction task). Optogenetic stimulation was applied during the behavioral sessions at different time points. Three cortical targets were examined: M1, S1, and V1 (control site).

Results
During the Direction task, optogenetic stimulation impaired performance, particularly during the Stimulus phase. M1 stimulation led to a reduction in correct rejections (CRs) and an increase in false alarms (FAs) during direction 2. S1 stimulation decreased the number of hits and CRs. The results for V1 were inconclusive due to limited data.

Conclusion
The impact of optogenetic inhibition of S1 suggests a disruption in the encoding of sensory properties and a decline in the animals&#39; ability to select the correct response. Surprisingly, M1 inhibition resulted in an increase in false alarms (FAs) instead of suppressing motor planning and execution, indicating that M1 may play a role in the integration of sensory information rather than being directly involved in the motor response of licking. Overall, inhibiting S1 impairs the encoding of sensory properties and decision-making processes, while inhibiting M1 affects the integration of sensory information. This research provides valuable insights into the specific roles of cortical regions in whisker discrimination tasks, emphasizing the potential of optogenetic modulation to enhance our understanding of sensorimotor pathways.

AMA Research Challenge 2023

Investigating cortical involvement in sensorimotor whisker discrimination task in mice

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AMA Research Challenge 2024 

Join the AMA Research Challenge poster symposium and semifinals to explore top research posters and score posters in the semifinals (an AMA member exclusive opportunity).

Background
Sensorimotor disruption can lead to many neurological disorders, thus the investigation of these cortical areas in animal models is paramount to learn more about their function. Here, we used optogenetics a biological tool to control activity of neurons and other cell types with light and a whisker discrimination task in mice. This invoked localized silencing of the Somatosensory (S1) and Motor (M1) cortices to demonstrate their involvement in the whisker discrimination task and thus deepen our understanding of cortical involvement in behavior. 

Methods
We used transgenic VGat-Chr2 mice, which expressed channelrhodopsin in inhibitory neurons. These inhibitory neurons can then be activated by light leading to localized silencing in targeted areas. The animals underwent a thinned-skull surgical procedure, where cranial windows were implanted over S1 and M1. The mice were then trained in a whisker-based go/no-go task that consisted of a direction discrimination, where one rotor direction is a distractor and the second is the important stimulus (Direction task). Optogenetic stimulation was applied during the behavioral sessions at different time points. Three cortical targets were examined: M1, S1, and V1 (control site).

Results
During the Direction task, optogenetic stimulation impaired performance, particularly during the Stimulus phase. M1 stimulation led to a reduction in correct rejections (CRs) and an increase in false alarms (FAs) during direction 2. S1 stimulation decreased the number of hits and CRs. The results for V1 were inconclusive due to limited data.

Conclusion
The impact of optogenetic inhibition of S1 suggests a disruption in the encoding of sensory properties and a decline in the animals' ability to select the correct response. Surprisingly, M1 inhibition resulted in an increase in false alarms (FAs) instead of suppressing motor planning and execution, indicating that M1 may play a role in the integration of sensory information rather than being directly involved in the motor response of licking. Overall, inhibiting S1 impairs the encoding of sensory properties and decision-making processes, while inhibiting M1 affects the integration of sensory information. This research provides valuable insights into the specific roles of cortical regions in whisker discrimination tasks, emphasizing the potential of optogenetic modulation to enhance our understanding of sensorimotor pathways.

poster

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### Grand Prize Sponsor

AMA would like to thank Laurel Road for sponsoring a $10,000 grand prize for the winner of the AMA Research Challenge. Laurel Road is not involved in the judging or scoring process to select the winner. The winner will be announced on February 4, 2024 during the AMA Research Challenge finals. Payment of the grand prize will be directly from Laurel Road. See the AMA Research Challenge Official Rules for terms and conditions.

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Join the AMA Research Challenge poster symposium and semifinals to explore top research posters, score posters in the semifinals (an AMA member exclusive opportunity) and attend education sessions with experienced physicians to learn tips to advance your research and career. 

Stroke is a leading cause of disability in the United States and the general population worldwide. Currently there are no successful treatments to restore normal function to stroke patients once brain damage has occurred. Our laboratory has pioneered antibody therapy directed at the neurite inhibitory protein Nogo-A to promote neuroplasticity and improve post-stroke recovery. Recent work from our laboratory has showed that Nogo-A blocks nerve growth factor (NGF)-dependent TrkA phosphorylation and activates a ceramide-dependent pathway, which negatively influences neuronal survival and neurite outgrowth. These findings suggest that the upregulation of Nogo-A following ischemic injury may interfere with the intrinsic neurotrophin-dependent plasticity that mediates recovery. Our central hypothesis is treatments that circumvent or block Nogo-A inhibition of TrkA to stimulate TrkA-mediated neurotrophin signaling pathways will enhance neuroplasticity and improve recovery following ischemic stroke. We conducted a pilot study, where we examined the effect of a TrkA agonist on Nogo-A signaling and functional recovery after experimental stroke in vivo. Baseline behavioral tests including skilled forelimb reaching task and horizontal ladder walk task were conducted on 8 male Long Evans, black hooded rats. The animals were then subjected to ischemic damage in the sensorimotor cortex by permanent middle cerebral artery occlusion. We continued behavior analysis 1 week after stroke and the animals were treated either with novel selective TrkA agonist gambogic amide or vehicle. Behavior was repeated 8 weeks later to determine functional recovery. In addition, we will also inject BDA for tracing of axonal pathways. The preliminary data from the behavior tests suggests that animals treated with agonist have better functional recovery as compared to control animals. This work will provide new treatments and strategies for enhancing stroke recovery in addition to advancing the knowledge of the function of Nogo-A as a negative regulator of neurotrophin signaling following brain injury.

Removal of Nogo-A Inhibition by Neurotrophin Signaling Pathway Activation Improves Sensorimotor Function After Stroke 


Background
Alzheimer's disease (AD) is the only top 10 cause of death that cannot be prevented, cured, or even slowed. We are developing attenuated furoxans− thiophilic NO donors that have neuroprotective activity, cross the blood brain barrier (a common obstacle in CNS drug discovery), and improve memory in mice− with the goal of alleviating the symptoms of AD and understanding its pathophysiology. Although Furoxans have been studied extensively, their mechanistic chemistry and protein targets have not been explored; in order to identify the subset of relatively reactive cellular thiols we will need to incorporate binding partners.

Methods
In order to identify the cellular targets responsible for furoxan bioactivation, we will synthesize furoxan analogs incorporating a photoaffinity labeling group and a terminal alkyne to covalently modify target proteins. We used OCF3 due to previously seen activity and incorporated diazirine, a main photoreactive group used in identifying biomolecule targets, to help facilitate a covalent bond between the compound and its target. Mainly diazirines present reactive and alkynyl sites are crucial in understanding cellular interactions with attenuated furoxans. The PAL group will attach the probe to binding partners upon irradiation with UV light. Following the synthesis of the compounds, we performed photolysis analysis via HPLC to determine the affects on photoreactivity.

Results
The tautomeric form of the furoxan being studied (3-aryl versus 4-aryl) does impact photoreactivity. The 4-Aryl OCF3 analog had a half-life of 7.7 minutes at 312 nm and 4.9 minutes and 365 nm. The 3-Aryl OCF3 analog had a half-life of 27.0 minutes at 312 nm and 5.6 minutes and 365 nm.The 4-aryl has a shorter half-life than the 3-aryl at 312 nm, however, 3-aryl has a shorter half-life at 365 nm in comparison to the 4-aryl.

Conclusion
Based on the non-reactive nature of the compounds, utilization of molecular probes will aid in understanding the mechanism of action. Incorporating a photoaffinity labeling cap group to probes that possess the efficacy of our active furoxan library would help to identify the cellular targets responsible for furoxan bioactivation and address the reactivity of our series of compounds. The purpose of the work is to use various molecular probes to broaden our understanding of our furoxan library, how it functions in the biological system, and also to use the obtained information to enhance affinity, efficacy, and metabolic effects.

Synthesis of 3 & 4 Aryl Furoxan Photoaffinity Probes

Background: Ovarian cancer (OC) is a deadly disease, with the 3rd highest mortality to incidence ratio of all cancers. OC’s asymptomatic nature early in the disease causes identification at advanced stages in 70+% of patients, at which point the 5-year survival rate can be as low as 20%. To date, no single biomarker has been able to detect early OC with high sensitivity and specificity. While elevated levels of Cancer Antigen 125 (CA-125) have been used to monitor patients pre-/post-operatively, CA-125 is limited in detecting early OC, and other benign ovarian or nongynecological conditions also have shown elevated CA-125. There is a critical need for novel biomarkers that can be used for screening, early diagnosis of OC and distinction of benign vs malignant masses. Our objective is to develop a novel sensitive and specific biomarker panel for OC early diagnosis where prognosis can be improved.

Methods: 288 plasma samples from women with OC (at various stages), benign gynecological conditions, other cancer types, and healthy non-cancer controls were analyzed with a curated panel of 8 biomarkers: CA-125, Growth Differentiation Factor 15 (GDF-15), Human Epididymis Protein (HE-4), Hepatocyte Growth Factor (HGF), Interleukin-6 (IL-6), Leukemia Inhibitory Factor (LIF), Osteopontin (OPN), and Prolactin (PRL). Receiver-operating characteristic (ROC) analysis was performed to assess sensitivity and specificity of single and multi-biomarkers amongst various subgroups.

Results: Univariate ROC analysis identified HE-4 and GDF-15 as having the highest area under the curve (AUC) (AUC=0.868, AUC=0.850, respectively) when comparing all stages of OC to healthy controls, a value greater than CA-125 (AUC=0.762). GDF-15 had the highest AUC when differentiating between early OC and healthy controls (AUC=0.772), a value greater than CA-125 (AUC=0.607). Amongst univariate markers, LIF was able to best differentiate between several other types of cancer (peritoneal, pancreatic, lung, and stomach) and OC. Multivariate analysis identified the panel containing CA-125, GDF-15, HE-4, IL-6, OPN, and PRL as having the highest AUC when comparing OC to healthy controls (AUC=0.956 for all stages, AUC=0.896 for early stages) and to benign conditions (AUC=0.826 for all stages). Adding LIF to this model allowed for best differentiation between OC and other cancer types (AUC=0.805 for all stages).

Conclusion: These results validate a novel biomarker panel for early detection of OC as well as distinction of benign masses and other malignancies from OC. Our results are expected to have an important positive impact by accurately detecting premalignant changes or early-stage OC in asymptomatic individuals.

Novel Biomarker Panels for Ovarian Cancer Screening

Purpose: Age-related macular degeneration (AMD) is characterized by pathologic extracellular lipid-rich deposits below and above the retinal pigment epithelium (RPE), respectively termed drusen and reticular pseudodrusen (RPD). Given apolipoprotein E (apoE) is one of the major components in drusen and RPD, the polarity of apoE secretion by the RPE likely contributes to whether RPD, drusen, or both dominate in an AMD patient. The mechanism dictating the polarity of apoE secretion in the RPE remains unknown. However, ATP-binding cassette A1 (ABCA1), a lipid transporter expressed in the RPE, is required for maintaining extracellular apoE levels in hepatocytes, where ABCA1 and apoE are both polarized to the sinusoidal side of the cell. We therefore investigated whether localization of ABCA1 in the RPE dictates the polarity of apoE secretion and if modulation of ABCA1 levels or function can alter extracellular apoE levels.

Methods: Human fetal (hf) RPE were plated on Transwells to allow for separate manipulation of the apical and basolateral sides of the RPE. To induce preferential apical apoE secretion, we applied two treatments we have shown will alter apoE secretion polarity: the addition of serum to only one chamber and aging cultures for more than a year. Immunocytochemistry (ICC) was then used to assess the localization of ABCA1 in hfRPE. ABCA1 was colocalized to phalloidin, an apical marker, and MCT3, a basolateral marker. Accumulation of secreted apoE was evaluated by Western Blots of the apical and basolateral media. ABCA1 expression was determined by Western Blot after treatment with Liver X Receptor (LXR) agonist, which upregulates ABCA1 expression, and after treatment with probucol, a ABCA1 inhibitor.

Results: ICC of hfRPE under conditions that favored apical apoE secretion did not show a corresponding shift in apical localization of ABCA1. In general, whether apoE secretion was polarized or not, ABCA1 had a fairly even distribution between the apical and basolateral RPE membranes. Treatment of hfRPE with LXR agonist upregulated ABCA1 but did not increase or switch the polarity of apoE secretion. Treatment with probucol caused a decrease in ABCA1 expression but no consistent effects on apoE secretion.

Conclusions: We demonstrated that the localization of ABCA1 in hfRPE is not related to the polarized secretion of apoE. Further experiments will probe other candidate mechanisms governing the polarity of apoE secretion in the RPE.

ABCA1 is Not Responsible for Polarized ApoE Secretion in the RPE

Purpose: To test the hypothesis that rod photoreceptor mitochondria function in vivo progressively declines over time.

Methods: 2, 12, and 24 mo dark- and light-adapted C57BL/6J (B6J) mice were examined by OCT. We measured i) an index of mitochondrial configuration within photoreceptors measured from the profile shape aspect ratio (MCP/AR) of the hyperreflective band posterior to the external limiting membrane (ELM)], ii) a proxy for energy-dependent pH-triggered water removal, the thickness of the ELM-retinal pigment epithelium (ELM-RPE), and its correlate iii) the hyporeflective band (HB) signal intensity at the photoreceptor tips. Visual performance was assessed by optokinetic tracking.

Results: In 2 mo and 24 mo mice, MCP/AR in both inferior and superior retina were smaller in light than in dark; no dark-light differences were noted in 12 mo mice. Dark-adapted inferior and superior, and light-adapted superior, ELM-RPE thickness increased with age. The dark-light difference in ELM-RPE thickness remained constant across all ages. All ages showed a decreased HB signal intensity magnitude in dark relative to light. In 12 mo mice, the dark-light difference in HB magnitude was greater than in younger and older mice. Anatomically, outer nuclear layer thickness decreased with age. Visual performance indices were reduced at 24 mo compared to 2 mo mice.

Conclusions: Whilst the working hypothesis was not supported herein, the results raise the possibility of a mid-life adaptation in rod mitochondrial function during healthy aging in B6J mice, a plasticity that occurred prior to declines in visual performance. 


Do Multiple OCT Biomarkers Indicate Age-related Decline in Rod Mitochondrial Function in C57BL/6J Mice? 

Purpose:
Multipotent adult stem cells (MASCs) isolated from human neonatal foreskin have been previously shown to differentiate into multiple mesodermal phenotypes. In vivo bone regeneration studies indicated that MASCs differentiated to osteoclasts, which are derived from monocytes. We tested the ability of MASCs isolated from human neonatal foreskin to differentiate into hematopoietic phenotypes in culture.

Methods:
Human tissues were obtained from the National Disease Research Institute under an IRB. MASCs isolated from human neonatal foreskin were isolated using an established protocol, enriched by freeze thawing, and expanded in culture. The MASCs were obtained by trypsinizing confluent adherent cultures, then aliquoting these cells into suspension or adherent cultures. The cells were fed with media with logarithmic concentrations of dexamethasone, a non-specific differentiator, from 0 M to 10-6 M, for 4 weeks. One culture method was the use of 15 mL centrifuge tubes. The centrifuge tubes were placed in the incubator after feedings at a 45 degree angle. Another method was suspending the MASCs into methylcellulose. Adherent cultures were done in 24 well plates. The presence of hematopoietic phenotypes was tested by immunohistochemical staining with primary antibodies to CD45, CD11b, CD33, and CD4. Alexa Flour 488 conjugated goat anti-mouse was used as a secondary antibody, and DAPI was used to stain nuclei. Staining was then visualized and images were captured.

Results:
MASCs from human neonatal foreskin differentiated into hematopoietic phenotypes. Nucleated hematopoietic cells (anti-CD45), myeloid lineages (anti-CD33), leukocytes (CD11b), and lymphocytes (CD4) were visualized in the final suspension cultures. Phenotypes were absent in control cultures (no dexamethasone), and found in greater numbers cultures treated with 10-8 to 10-6 M dexamethasone. 

Conclusion:
These preliminary results indicate that human MASCs are capable of differentiating into cells of the hematopoietic lineage. CD45 is a marker for all nucleated hematopoietic cells, CD33 is specific for monocytes/macrophages, CD11b is specific for leukocytes, and CD4 is specific for lymphocytes. Further research is needed to confirm these in vitro results, and then test the ability of MASCs to differentiate to hematopoietic phenotypes in vivo.

Differentiating Human Multipotent Adult Stem Cells toHematopoietic Phenotypes in Vitro

Background
Our group has shown that high density mesenchymal stromal cell (MSC) sheet implantation improves bone healing in a critical-sized bone defect model; however, these cells exhibit increased aging and cellular senescence in prolonged sheet culture, diminishing their therapeutic potential. Promisingly, rapamycin has emerged as a potential agent to rejuvenate aged MSCs. This study aimed to confirm rapamycin’s ability to prevent senescence and isolate specific pathways/genes responsible.

Methods
hPMSCs were seeded at high density (65,000 cell/cm2) and treated with either rapamycin (10 nM) or control vehicle (DMSO) for up to 7 days. Senescence and autophagy were assessed by senescence-associated 𝛽-Galactosidase (SA 𝛽-Gal) staining and DAPI nuclear staining, respectively. Additionally, cell culture media was extracted at different time points to assess senescence-associated cytokines IL-6 and IL-8 via ELISA. Finally, total RNA was extracted for differential gene analysis via GeneChip Clariom S Human Arrays.

Results 
Rapamycin significantly decreased SA-B Gal staining at all time points, with 67.7% and 72.9% less area when compared to control at day 4 and 7, respectively. Senescent-associated cytokine IL-6 levels were significantly reduced when compared to control, with 614.3 pg/ml and 286.6 pg/ml decreases at day 2 and 4 of treatment, respectively. Interestingly, IL-8 expression had increased significantly at all time points, with a 979.9 pg/ml difference at day 4 of treatment. Autophagy associated vacuoles-stained area had a 3.94-fold increase at day 4 of treatment compared to vehicle. Microarray gene analysis identified a total of 429 genes with a 2-fold or greater change in expression following treatment. FoxO, cellular senescence, and cell cycle pathways are some of many effected with significantly altered expression of FBXO32, PSAT1, CXCL8, and MYC, acting as potential players in rapamycin’s anti-aging effects.

Conclusion 
Rapamycin has proven effective in prolonging pMSC lifespan. The speculation and understanding of genes enacting this function may aid in isolating this specific role for usage in prolonging sheet cultures to enhance bioengineering applications. Numerous pathways identified in this study may explain rapamycin’s anti-aging functionality and lead to the creation of therapeutics specifically targeting relevant genes. The presence of enhanced IL-8 may prove beneficial in preserving stem cell functionality, specifically for wound healing applications. These findings prove rapamycin is a candidate for improving stem cell preparation and support previous studies indicating IL-8 may enhance stem cell viability, results useful in advancing stem cell therapy usage for bone remodeling/bioengineering.


Rapamycin Prevents Senescence and Functional Decline of High-Density Placental Mesenchymal Stem Cells

Background
Osteoporosis is one of the major causes of fractures in adults. As of 2004, it was estimated that approximately 10 million Americans >50 years have osteoporosis with annual cost of $25 billion. Osteoporosis can lead to many fragility fractures, especially hip fractures. Hip fractures are often associated with high levels of mortality. The cumulative mortality that is associated with one-year post hip fracture is between 20-40% with an additional risk of refracture. Although there are non-pharmacologic and pharmacologic treatment options available for osteoporosis, their use post hip fracture is low. Of the patients who present with fragility fractures, only 9-20% of the patients are treated for osteoporosis, increasing the chance of re-fracture in untreated patients.

Methods
A literature search was performed using PubMed and the following key words: “Osteoporosis” and “Hip fractures” in Title/Abstract. Initial search led to 3345 results. Studies on only humans were included. Literature after 2013 was included. Only Clinical Trials, Meta-Analyses, Randomized Controlled Trials, Reviews, Systematic Reviews were included. After an extensive two-tier review process, 14 articles are included in this review. 

Results
Fracture Liaison Service (FLS) and Orthogeriatric Service (OGS) are multidisciplinary team approaches that provide care for patients post-fragility fractures. FLS is shown to increase the rates of DEXA evaluations, improved prescription initiation rates for osteoporosis medications, and reduction in re-fracture rates. When comparing the effectiveness of FLS at tertiary hospitals, the hospital with FLS approximately 30% reduction in any refractures and 40% reduction in new major fractures over a three-year period. FLS is shown to be cost-effective as it prevented more fractures and increased quality-adjusted life years (QALYs). OGS is also shown to decrease length of stay at the hospital, lower risk of in-hospital mortality, and delirium. In addition, patients receiving OGS had improved mobility at 12 months post fracture when compared to usual orthopedic care. Implementation of FLS and OGS also shows decrease in mortality within 30 days and within one year in patients with hip fracture.

Conclusion
The introduction of FLS and OGS models changed the field of post fracture osteoporosis management. Initiation of pharmacological and nonpharmacological treatments post fracture has the potential to improve bone health, decrease re-fracture rates, decrease mortality and morbidity, and improve quality of life. The costs of follow up medical care have been shown to be reduced these services These models have been effective at providing the care that fragility fracture patients need.

The Importance of Fracture-Liaison Services and Orthogeriatric Services for Osteoporotic fractures

Background
Cartilage damage is challenging to treat due to its limited self-healing capacity caused by its avascular nature. However, 3D tissue engineering approaches that utilize biomaterials, additives, and cells offer a promising solution to regenerate functional cartilage. These innovative techniques have the potential to restore native cartilage properties, prevent the development of osteoarthritis, and restore joint function. In this study, we investigate a novel alginate-based 3D bioink composed of human articular cartilage for cartilage tissue engineering.

Methods
The bioink was developed by encapsulating C20A4 human articular chondrocytes in a mixture consisting of 20% medium viscosity sodium alginate (Alg), 5% polyvinyl alcohol (PVA), 5% Gum Arabic (GA), and 5% human articular cartilage. The human articular cartilage was obtained from cartilage shavings of distal femurs and ground into a powder for incorporation into the bioink. The bioink was printed into concentric discs using a BIO-X 3D Bioprinter, and the resulting 3D-biofabricated constructs were cross-linked with calcium chloride, rinsed, and cultured in chondrogenic media. Thirty-six total constructs were fabricated. Immediately after 3D printing, a portion of constructs were visualized with SEM (n=1) and underwent compression testing (n=5) to examine the microstructure and mechanical strength respectively. The remaining constructs were placed in culture for 1,7 or 14 days and subsequently analyzed for cellular viability (n=5) and gene expression (n=5) at each time point.

Results
SEM imaging revealed that the 3D-printed constructs exhibited a porous structure. The average elastic modulus of the constructs was 0.48 MPa. Post-printing, the cellular viability was 87.2% which decreased significantly to 76.4% at day 7 (p<0.001) but recovered to 85.9% at day 14 in culture. Furthermore, gene expression analysis showed a significant increase in transcriptional activity of chondrogenic genes Col2a1 (p=0.008) and Sox9 (p=0.021) at day 14 compared to day 1.

Conclusion
This study explored the use of an innovative alginate-based 3D bioink composed of human articular cartilage for cartilage tissue engineering. The bioink successfully formed porous 3D constructs that withstood the printing process. Additionally, the elastic modulus of these engineered constructs approached that of native cartilage (0.45-0.8MPa). Although cellular viability initially decreased, it gradually recovered over a two-week culture period. Moreover, the upregulation of chondrogenic genes indicates the potential of the bioink to promote cartilage regeneration. These findings suggest this bioink holds promise as an effective approach for cartilage tissue engineering, offering possibilities for future therapeutic interventions in cartilage repair and regeneration.

Novel 3D Extrusion Bioink Containing Processed Human Articular Cartilage for Application in Cartilage Tissue Engineering

Cerebrospinal fluid (CSF) homeostasis in the brain relies on a delicate balance in CSF production, circulation, and excretion. When this balance is compromised, patients develop a spectrum of disorders, including hydrocephalus and neurodegenerative diseases. Emerging studies suggest that the lymphatic system, referred to as the glymphatic system in the brain, may have a previously unknown role in CSF homeostasis. Interestingly, it is unknown whether the glymphatic system has any role in embryonic CSF regulation. Frog Xenopus has been widely used to study fundamental neurodevelopmental processes and is a unique model to investigate CSF dynamics. In Xenopus, unlike any other model system, whole brain CSF circulation can be visualized in real-time and manipulated easily, providing unprecedented insight into CSF hemostasis. In this work, we asked whether frogs have a glymphatic system and its role in CSF regulation. Using the frog Xenopus model system, we show that the glymphatic system is essential in CSF drainage during embryonic brain development. We used post-fertilization day 4-Xenopus tadpoles, where we injected conjugated ovalbumin into the brain ventricle and simultaneously into the tadpole's heart. Then we used confocal imaging to visualize CSF circulation and systemic cardiac circulation in parallel. We showed that there was no overlap between the two circulations. However, when we disrupted lymphatic formation, we showed that CSF excretion was disrupted, suggesting that Xenopus CSF excretion relies on the glymphatic system rather than cardiac circulation. In further studies, we will look at how CSF excretion is conserved among species and relate to our patients with hydrocephalus, Alzheimer’s, and other neurodegenerative diseases where abnormal CSF excretion is critical for disease progression.

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Removal of Nogo-A Inhibition by Neurotrophin Signaling Pathway Activation Improves Sensorimotor Function After Stroke

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