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Category: Ankle; Sports Introduction/Purpose: Ankle sprains represent one of the most common injuries among both athletes and the general public (1). While most sprains resolve with conservative therapy, failure resulting in ligament laxity may necessitate surgical intervention due to pain and instability from injury to the anterior talofibular ligament (ATFL), the weakest ligament in the lateral ligamentous complex (2). Surgical repair of ATFL has relatively high success rates, however post-procedure chronic instability and pain remain a clinical challenge, with re-operation rates reported as high as 14% (3). The Artelon® FlexBand® matrix is a biocompatible, synthetic matrix designed to reinforce soft tissue repair during tendon/ligament reconstructive procedures. The goal of this study is to compare the outcomes of ATFL reconstructive surgery with and without this synthetic graft augmentation. Methods: This multi-center, IRB approved study used a combination of retrospective medical chart review and prospective procedure satisfaction phone surveys in patients that had undergone ATFL repair (isolated and non-isolated) with or without synthetic graft augmentation. These results represent an interim data analysis of an ongoing clinical study. A total of 234 patients, (82 Control and 152 FlexBand augmented) diagnosed with chronic lateral ankle instability that had failed conservative therapy, and required surgical intervention to repair the lateral ligament complex were enrolled across four different research centers. Patient demographics, physician assessment of healing progression, safety, complications necessitating a return to OR, and post-op rehabilitation schedule were analyzed. Two study sites used Visual Analog Scale (VAS) to assess pain pre-surgically and at 2, 6, and 12 week follow-up visits. Phone survey questionnaires were given to patients that reached at least 1yr post-op to assess long-term patient satisfaction and function. Results: Average patient age was 42yrs in both groups and average follow-up time was 19.2mo (FlexBand) and 28.4mo (Control). There was no statistical difference in baseline VAS pain scores between groups. Augmented patients demonstrated significantly lower VAS scores at 2-,6-, and 12-week follow-up visits (p < 0.001, p< 0.0001and p< 0.0001, respectively) compared to controls (Fig 1). In addition, a significant acceleration in return to FWB status in augmented group compared to control patients was observed (9.04 ± 0.38wks, N=101 vs. 11.82 ± 1.67wks, N=45; p = 0.027). Both groups demonstrated equivalent AE safety profiles and complications were similar across groups with 3.7% (3/82) of control and 3.9% (6/152) augmented patients requiring a return to OR, however, no AEs or complication events were related to the Flexband Device. Conclusion: Our data shows a significant reduction in VAS pain scores in patients who underwent the modified Brostrom procedure with augmentation at all follow up time points. In addition, synthetic graft augmentation may lead to earlier return to function due to the significantly lower time to achieve FWB status. Further investigation on the potential clinical benefits of ATFL augmentation with Artelon Flexband is ongoing through a prospective, randomized, controlled study. Overall, long-term (>1yr) patient satisfaction was equivalent across groups and a trend toward potential earlier recovery times were better for the augmented group than the control group.

Characterising interspecific interaction strengths, combined with population abundances of prey and their novel predators, is critical to develop predictive invasion ecology. This is especially true of aquatic invasive species, which can pose a significant threat to the structure and stability of the ecosystems to which they are introduced. Here, we investigated consumer-resource dynamics of two globally-established aquatic invasive species, European green crab (Carcinus maenas) and brown trout (Salmo trutta). We explored the mediating effect of prey density on predatory impact in these invaders relative to functionally analogous native rock crab (Cancer irroratus) and Atlantic salmon (Salmo salar), respectively, feeding on shared prey (Mytilus sp. and Tenebrio molitor, respectively). We subsequently combined feeding rates with each predator’s regional abundance to forecast relative ecological impacts. All predators demonstrated potentially destabilising Type II functional responses towards prey, with native rock crab and invasive brown trout exhibiting greater per capita impacts relative to their trophic analogues. Functional Response Ratios (attack rates divided by handling times) were higher for both invasive species, reflecting greater overall per capita effects compared to natives. Impact projections that incorporated predator abundances with per capita effects predicted severe impacts by European green crabs. However, brown trout, despite possessing higher per capita effects than Atlantic salmon, are projected to have low impact owing to currently low abundances in the sampled watershed. Should brown trout density increase sixfold, we predict it would exert higher impact than Atlantic salmon. Such impact-forecasting metrics and methods are thus vital tools to assist in the determination of current and future adverse impacts associated with aquatic invasive species.

The noise performance of three types of n+/p-well single-photon avalanche diodes (SPADs) fabricated in a standard 180 nm CMOS technology is studied. The SPADs had different poly gate configurations: no poly gate (SPAD_NG), a dummy floating poly gate (SPAD_DG), and a field poly gate connected to the n+ cathode (SPAD_FG). The measurement results of dark count rate and afterpulsing showed that the SPAD_DG had better noise performance compared to the SPAD_NG. This is because the dummy poly gate pushed the shallow trench isolation away from the active region of the SPAD, thus reducing the dark noise generated from the Si-SiO2 interface. The measurement results also revealed that the noise performance can be further improved by connecting the poly gate to the n+ cathode. The voltage on the poly gate in SPAD_FG reduced the electric field in the n-well guard ring (GR) region, thus reducing the carriers from the GR region that can enter the active region of SPADs and initiate dark counts.

Este estudio trata sobre los procesos históricos de racionalización de las interacciones humano-mastodonte en Ecuador, siendo el enfoque principal el mastodonte de Alangasí. Esta investigación también examina la documentación colonial española temprana de las creencias orales indígenas de los gigantes en los Andes y costa, que a menudo tienen vínculos directos con sitios reales con restos de mastodontes y megafauna. Tal enfoque conecta la investigación moderna con el pasado arqueológico y paleontológico. Un intermedio etnohistórico examina la semiótica indígena y europeo colonial de la megafauna a través del desarrollo de ciencia y la hermenéutica arqueológica y paleontológica. Este es un estudio tanto de la percepción como del avance de la racionalización del pasado prehistórico.

Background: Fully covered intraductal self-expanding metal stents (IDSEMS) have been well described in the management of post-liver transplant (LT) anastomotic strictures (ASs). Their antimigration waists and intraductal nature make them suited for deployment across the biliary anastomosis. Objectives: We conducted a multicentre study to analyse their use and efficacy in the management of AS. Design: This was a retrospective, multicentre observational study across nine tertiary centres in the United Kingdom. Methods: Consecutive patients who underwent endoscopic retrograde cholangiopancreatography with IDSEMS insertion were analysed retrospectively. Recorded variables included patient demographics, procedural characteristics, response to therapy and follow-up data. Results: In all, 162 patients (100 males, 62%) underwent 176 episodes of IDSEMS insertion for AS. Aetiology of liver disease in this cohort included hepatocellular carcinoma ( n = 35, 22%), followed by alcohol-related liver disease ( n = 29, 18%), non-alcoholic steatohepatitis ( n = 20, 12%), primary biliary cholangitis ( n = 15, 9%), acute liver failure ( n = 13, 8%), viral hepatitis ( n = 13, 8%) and autoimmune hepatitis ( n = 12, 7%). Early AS occurred in 25 (15%) cases, delayed in 32 (20%) cases and late in 95 (59%) cases. Age at transplant was 54 years (range, 12–74), and stent duration was 15 weeks (range, 3 days–78 weeks). In total, 131 (81%) had complete resolution of stricture at endoscopic re-evaluation. Stricture recurrence was observed in 13 (10%) cases, with a median of 19 weeks (range, 4–88 weeks) after stent removal. At removal, there were 21 (12%) adverse events, 5 (3%) episodes of cholangitis and 2 (1%) of pancreatitis. In 11 (6%) cases, the removal wires unravelled, and 3 (2%) stents migrated. All were removed endoscopically. Conclusion: IDSEMS appears to be safe and highly efficacious in the management of post-LT AS, with low rates of AS recurrence.

Objectives The COVID-19 pandemic inspired social changes that promote outdoor activities including eating at restaurants, which may linger in a world hyperfocused on disease transmission prevention, increasing the vulnerabilities to vehicle-based terrorism. Vehicle ramming attacks started to transition from a relatively rare method of attack to one of the most lethal forms of terrorism in Western countries just prior to the emergence of SARS-CoV-2. This study aims to provide a historical analysis of the terrorism-based attacks using vehicles between 1970 and 2019.Methods This study uses the methodology suggested by Tin et al in which the Global Terrorism Database hosted by the National Consortium for the Study of Terrorism and Responses to Terrorism was searched retrospectively for data. Data was collected from the database using the internal search function for terror events between January 1, 1970 and December 31, 2019 which used a vehicle as a means of attack.Results There were 257 recorded terror attacks that involved some type of vehicle between 1970 and 2019. The attacks resulted in 808 fatalities and 1715 injuries when excluding the September 11 attacks. 76 events occurred at the West Bank and Gaza Strip, 25 in the USA, 16 in Israel, and 14 in the UK. Of the 257 terror incidents, 71% (183) occurred within the last 6-year span of inquiry.Conclusion By 2016, vehicle attacks were the most lethal form of attack comprising just over half of all terrorism-related deaths in that year. Large gatherings such as festivals, sporting events, and now outdoor seating at restaurants, leave a number of people highly vulnerable to a vehicle ramming attacks depending on established countermeasures. The increased prevalence of outdoor activities and gatherings in a post-COVID-19 world will further expose large numbers of people to the potential vulnerabilities of vehicle-based terrorism. The scale of the casualties from a vehicle-based terror attack can overwhelm traditional resources and strain the abilities of the healthcare sector. Counterterrorism and disaster medicine specialists are crucial players in educating first responders and emergency medicine providers, allowing them to adequately prepare for an evolving threat in a world devastated by COVID-19.Level of evidence VI.

Quantum computers offer the potential to efficiently simulate the dynamics of quantum systems, a task whose difficulty scales exponentially with system size on classical devices. To assess the potential for near-term quantum computers to simulate many-body systems we develop a formalism to straightforwardly compute bounds on the number of Trotter steps needed to accurately simulate the time evolution of fermionic lattice models based on the first-order commutator scaling. We apply this formalism to two closely related many-body models prominent in condensed matter physics, the Hubbard and t-J models. We find that, while a naive comparison of the Trotter depth first seems to favor the Hubbard model, careful consideration of the model parameters and the allowable error for accurate simulation leads to a substantial advantage in favor of the t-J model. These results and formalism set the stage for significant improvements in quantum simulation costs.

Abstract: Tributyltin (TBT) is a synthetic chemical widely used in industrial and commercial applications. TBT exposure has been proven to elicit obesogenic effects. Gestational exposure led to increased white adipose tissue depot size in exposed (F1, F2) animals and in unexposed generations (F3, F4), an example of transgenerational inheritance. TBT exerts these effects, in part, by increasing the number and size of white adipocytes, by altering the fate of multipotent mesenchymal stromal stem cells to favor the adipocyte lineage, by altering adipokine secretion and by modulating chromatin structure. Adipose tissue resident macrophages are critical regulators in adipose tissue; however, the effects of TBT on adipose tissue macrophages remained unclear. Here we investigated the effects of TBT on macrophages and consequent impacts on adipocyte function. TBT significantly enhanced palmitate-induced inflammatory gene expression in mouse bone marrow derived macrophages and this effect was attenuated by antagonizing action of the nuclear receptor, PPARγ. TBT-treated macrophages decreased lipid accumulation in white adipocytes differentiated from MSCs accompanied by increased expression of lipolysis genes. Lastly, ancestral TBT exposure increased Tnf expression in adipose tissue resident macrophages in both exposed (F2) and unexposed (F3) generations, suggesting that TBT exposure led to an inherited predisposition toward inflammatory adipose tissue macrophages that can manipulate adipose tissue function. These findings provide new insights into the interplay between adipocytes and adipose tissue macrophages in obesity, further establishing a role for obesogens such as TBT in the development of obesity-related metabolic disorders.

Abstract Background Diabetes related foot ulcers can have physical, social, emotional, and financial impacts on the daily life and wellbeing of many people living with diabetes. Effective treatment of diabetes related foot ulcers requires a multi‐faceted, multi‐disciplinary approach involving a podiatrist, other healthcare professionals, and the person with diabetes however, limited research has been conducted on the lived experience of podiatric treatment for diabetes related foot ulcers to understand how people are engaged in their ulcer management. Therefore, this study aimed to explore the lived experience of receiving podiatric treatment for diabetes related foot ulcers in a tertiary care outpatient setting. Methods Ten participants were interviewed. All were male, with mean age of 69 (SD 15) years and currently undergoing podiatric treatment for a diabetes related foot ulcer in a tertiary care setting. Participants with diabetes related foot ulcers were purposively recruited from the outpatient podiatry clinic at a tertiary hospital in a metropolitan region of South Australia. Semi‐structured interviews were conducted to gain insight into the lived experience of people receiving podiatric treatment for their foot ulcer and understand how this experience impacts their regular lifestyle. Data were analysed using a thematic analysis method. Results Four themes were identified that add an understanding of the lived experience of participants: ‘Trusting the podiatrists with the right expertise’, ‘Personalised care’, ‘Happy with the service, but not always with prescribed care’, and ‘It's a long journey’. Participants described professional behaviour including high organisation and hygiene practices and demonstrated expertise as key factors influencing their trust of a podiatrist's care. Information tailored to individual needs was helpful for participants. Offloading devices and ulcer dressings were often burdensome. Podiatric treatment for foot ulcers was a lengthy and onerous experience for all participants. Conclusions The findings of this study suggest podiatrists can use practical strategies of maintaining consistency in who provides podiatry care for the person, demonstration of high organisational and hygiene standards, and using innovation to adapt information and equipment to suit an individual's lifestyle to support positive experiences of podiatric ulcer care. There is a need for further research to understand how a person's experience of podiatric ulcer care differs amongst genders, cultural groups, and healthcare settings to facilitate positive care experiences and reduce treatment burden for all people with diabetes requiring podiatric ulcer treatment.

No abstract available.

An osteoid osteoma is a benign bone tumor that arises from osteoblastic dysfunction and usually presents as nonspecific, nocturnal pain located in the diaphysis of long bones, with

Ultrasound can be used to assess injury and structural changes to the soft-tissue structure of the foot. It may be useful to assess the feet of people with diabetes who are at increased risk of plantar soft-tissue pathological changes. The aim of this study was to determine if ultrasound measurements of plantar soft-tissue thickness and assessments of tissue acoustic characteristics are reliable in people with and without diabetes mellitus. A repeated measures design was used to determine intra-observer reliability for ultrasound measurements of plantar skin and fat pad thickness and intra- and inter-observer reliability of plantar skin and fat pad tissue characterisation assessments made at foot sites which are at risk of tissue injury in people with diabetes. Thickness measurements and tissue characterisation assessments were obtained at the heel and forefoot in both the unloaded and compressed states and included discrete layers of the plantar tissues: skin, microchamber, horizontal fibrous band, macrochamber and total soft-tissue depth. At each site, relative intra-observer reliability was achieved for the measurement of at least one plantar tissue layer. The total soft-tissue thickness measured in the unloaded state (ICC 0.925-0.976) demonstrated intra-observer reliability and is the most sensitive for detecting small change on repeated measures. Intra-observer agreement was demonstrated for tissue characteristic assessments of the skin at the heel (k = 0.70), fat pad at the lateral sesamoid region (k = 0.70) and both skin and fat pad at the second (k = 0.80, k = 0.70 respectively) and third metatarsal heads (k = 0.90, k = 0.79 respectively). However, acceptable inter-observer agreement was not demonstrated for any tissue characteristic assessment, therefore the use of multiple observers should be avoided when making these assessments.

Abstract Background The health outcomes of men continue to be poorer than women globally. Challenges in addressing this problem include difficulties engaging men in weight loss programs as they tend to view these programs as contrary to the masculine narrative of independence and self-reliance. Researchers have been turning towards sports fans to engage men in health promotion programs as sports fans are typically male, and tend to have poor health habits. Methods Developed from the highly successful gender-sensitized Football Fans in Training program, Hockey Fans in Training (Hockey FIT) recruited 80 male hockey fans of the London Knights and Sarnia Sting who were overweight or obese into a weekly, 90-minute classroom education and group exercise program held over 12 weeks; a 40-week minimally-supported phase followed. A process evaluation of the Hockey FIT program was completed alongside a pragmatic randomized controlled trial and outcome evaluation in order to fully explore the acceptability of the Hockey FIT program from the perspectives of coaches delivering and participants engaged in the program. Data sources included attendance records, participant focus groups, coach interviews, assessment of fidelity (program observations and post-session coach reflections), and 12-month participant interviews. Results Coaches enjoyed delivering the program and found it simple to deliver. Men valued being among others of similar body shape and similar weight loss goals, and found the knowledge they gained through the program helped them to make and maintain health behaviour changes. Suggested improvements include having more hockey-related information and activities, greater flexibility with timing of program delivery, and greater promotion of technology support tools. Conclusions We confirmed Hockey FIT was an acceptable “gender-sensitized” health promotion program for male hockey fans who were overweight or obese. Minor changes were required for optimization, which will be evaluated in a future definitive trial. Trial registration NCT02396524 (Clinicaltrials.gov). Date of registration: Feb 26, 2015.

Category: Hindfoot Introduction/Purpose: Plantar fasciitis is the most common cause of heel pain, resulting in an estimated 1 million visits to medical professionals annually. Conservative treatments for plantar fasciitis include rest, orthotics, night splint, stretching and non- steroidal anti-inflammatory drugs. Such treatments are successful in nearly 90% of patients, however, more invasive treatments are required for patients whose heel pain symptoms persist greater than six months. Fetal tissues, including the umbilical cord (UC) and amniotic membrane (AM) have been increasingly used to modulate healing in different parts of the body over the last two decades. These tissues have been demonstrated to possess anti-inflammatory and anti-scarring properties in addition to containing growth factors, cytokines, and matrix components to promote healing, and offer a potential therapy for plantar fasciitis. Methods: In this clinical series, we sought to evaluate the efficacy of cryopreserved, particulate UC/AM tissues as a treatment for plantar fasciitis as well as to determine if multiple injections provide an even greater benefit compared to a single injection. A multicenter prospective study was performed where patients were randomized to receive 25, 50, or 100 mg UC/AM tissue and either a single injection or two injections (at baseline and six weeks). All injections were administered under ultrasound guidance into the plantar fascia. At six, 12, and 18 weeks, patients returned and data on foot pain as well as the FAAM questionnaire were collected. Results: Last year, we presented interim data on 18 patients who had completed 18 weeks of follow-up. This year, we present the completed results of the study. Overall, patient foot pain was found to be significantly reduced in all treatment groups from baseline. FAAM scores for both activities of daily living and sports subscales also improved in all treatment groups, with overall improvement ranging from 60 – 150% compared to baseline. All patients showed variable degrees of improvement with no patients showing any deterioration. Conclusion: The results of this case series are similar to the results of an earlier study which found that injection of a particulate human amniotic membrane product for plantar fasciitis was safe and comparable to corticosteroids. While all treatments demonstrated improvement in both foot pain and FAAM scores, there was both a dose dependent as well as injection dependent effect of particulate UC/AM tissue on foot pain reduction (100 mg > 50 mg >25 mg; 2 injections > 1injection) suggesting a possible additive effect. Overall, these results are promising and highlight the potential effectiveness of UC/AM tissues as a treatment for plantar fasciitis.

Background and study aims Stent insertion at endoscopic retrograde cholangiopancreatography (ERCP) is an established therapy for managing malignant biliary obstruction. Conventional plastic stents with a tubular design are most commonly used despite limited patency. Plastic stents with a winged design may theoretically increase the duration of stent patency. The aim of this study was to compare stent patency of the winged versus conventional plastic stents in patients with malignant biliary obstruction. Patients and methods A prospective, randomized subject-blinded trial was conducted. Patients with malignant biliary obstruction were randomized (1:1) to either a 10 French winged stent or 7 or 10 French conventional plastic stent. Strictures greater than 1 cm distal to the hilum were included. Patients were followed clinically to determine the frequency of stent failure until surgery, death or study closure. Results Fifty-eight patients were enrolled. Following 9 exclusions, 49 patients were randomized to a winged (n = 23) or conventional stent (n = 26). Median time to stent failure was 89 (95 % CI 26-NA) vs 143 (95 % CI 33 – 266) days (P = 0.963) for the winged and conventional group, respectively. Stent failure for the winged group occurred in 11 (48 %) compared to 14 (54 %) in the conventional group. Median survival was 123 (95 % CI 81 – 189) vs 342 days (95 % CI 123 – 704) (p = 0.084) in the winged and conventional group respectively. There were no procedure related adverse events. Conclusions Improvement in stent patency was not seen with the winged stent when compared to the conventional plastic stent. Clinical trials number NCT01514214.

Earthbag construction is a sustainable, low-cost, housing option for developing countries. Earthbag structures are built of individual soil-filled fabric bags (i.e., sand bags) stacked in a running bond pattern. Once stacked, earthbags are compacted and the soil inside the bags is dried in-place to form earthen bricks. Barbed wires are placed between each course to affect shear transfer within the wall. Results of an out-of-plane load test on a full-scale earthbag wall are presented in this paper. The wall was subjected to out-of-plane pressure up to 3.16 kPa, which resulted in plastic deformations up to 50 mm. The wall did not collapse during loading. Wall behavior and force transfer mechanisms are discussed.

Retroperitoneal hematoma is rare and benefits from a systematic approach to prevent morbidity and mortality. Management of such bleeds is based upon patient stability, the cause (spontaneous or posttraumatic), and source (arterial or venous). Herein, the authors describe a diagnostic and management algorithm for retroperitoneal hemorrhage with an example of a rare lumbar venous bleed under the complicated clinical setting of deep venous thrombosis.

Phototrophic microbial mats are among the most diverse ecosystems in nature. These systems undergo daily cycles in redox potential caused by variations in light energy input and metabolic interactions among the microbial species. In this work, solid electrodes with controlled potentials were placed under mats to study the electron transfer processes between the electrode and the microbial mat. The phototrophic microbial mat was harvested from Hot Lake, a hypersaline, epsomitic lake located near Oroville (Washington, USA). We operated two reactors: graphite electrodes were polarized at potentials of -700 mVAg/AgCl (cathodic mat system) and +300 mVAg/AgCl (anodic mat system) and the electron transfer rates between the electrode and mat were monitored. We observed a diel cycle of electron transfer rates for both anodic and cathodic mat systems. Interestingly, the cathodic mats generated the highest reducing current at the same time points that the anodic mats showed the highest oxidizing current. To characterize the physicochemical factors influencing electron transfer processes, we measured depth profiles of dissolved oxygen and sulfide in the mats using microelectrodes. We further demonstrated that the mat-to-electrode and electrode-to-mat electron transfer rates were light- and temperature-dependent. Using nuclear magnetic resonance (NMR) imaging, we determined that the electrode potential regulated the diffusivity and porosity of the microbial mats. Both porosity and diffusivity were higher in the cathodic mats than in the anodic mats. We also used NMR spectroscopy for high-resolution quantitative metabolite analysis and found that the cathodic mats had significantly higher concentrations of osmoprotectants such as betaine and trehalose. Subsequently, we performed amplicon sequencing across the V4 region of the 16S rRNA gene of incubated mats to understand the impact of electrode potential on microbial community structure. These data suggested that variation in the electrochemical conditions under which mats were generated significantly impacted the relative abundances of mat members and mat metabolism.

Microbial autotroph-heterotroph interactions influence biogeochemical cycles on a global scale, but the diversity and complexity of natural systems and their intractability to in situ manipulation make it challenging to elucidate the principles governing these interactions. The study of assembling phototrophic biofilm communities provides a robust means to identify such interactions and evaluate their contributions to the recruitment and maintenance of phylogenetic and functional diversity over time. To examine primary succession in phototrophic communities, we isolated two unicyanobacterial consortia from the microbial mat in Hot Lake, Washington, characterizing the membership and metabolic function of each consortium. We then analyzed the spatial structures and quantified the community compositions of their assembling biofilms. The consortia retained the same suite of heterotrophic species, identified as abundant members of the mat and assigned to Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. Autotroph growth rates dominated early in assembly, yielding to increasing heterotroph growth rates late in succession. The two consortia exhibited similar assembly patterns, with increasing relative abundances of members from Bacteroidetes and Alphaproteobacteria concurrent with decreasing relative abundances of those from Gammaproteobacteria. Despite these similarities at higher taxonomic levels, the relative abundances of individual heterotrophic species were substantially different in the developing consortial biofilms. This suggests that, although similar niches are created by the cyanobacterial metabolisms, the resulting webs of autotroph-heterotroph and heterotroph-heterotroph interactions are specific to each primary producer. The relative simplicity and tractability of the Hot Lake unicyanobacterial consortia make them useful model systems for deciphering interspecies interactions and assembly principles relevant to natural microbial communities.

A sample of public child welfare workers trained at two public universities in the south were surveyed concerning their readiness to engage in culturally responsive practice. Results indicate that non-Hispanic [...]

Abstract Background Understanding stem cell differentiation is essential for the future design of cell therapies. While retinoic acid (RA) is the most potent small molecule enhancer of skeletal myogenesis in stem cells, the stage and mechanism of its function has not yet been elucidated. Further, the intersection of RA with other signalling pathways that stimulate or inhibit myogenesis (such as Wnt and BMP4, respectively) is unknown. Thus, the purpose of this study is to examine the molecular mechanisms by which RA enhances skeletal myogenesis and interacts with Wnt and BMP4 signalling during P19 or mouse embryonic stem (ES) cell differentiation. Results Treatment of P19 or mouse ES cells with low levels of RA led to an enhancement of skeletal myogenesis by upregulating the expression of the mesodermal marker, Wnt3a, the skeletal muscle progenitor factors Pax3 and Meox1, and the myogenic regulatory factors (MRFs) MyoD and myogenin. By chromatin immunoprecipitation, RA receptors (RARs) bound directly to regulatory regions in the Wnt3a, Pax3, and Meox1 genes and RA activated a β-catenin-responsive promoter in aggregated P19 cells. In the presence of a dominant negative β-catenin/engrailed repressor fusion protein, RA could not bypass the inhibition of skeletal myogenesis nor upregulate Meox1 or MyoD. Thus, RA functions both upstream and downstream of Wnt signalling. In contrast, it functions downstream of BMP4, as it abrogates BMP4 inhibition of myogenesis and Meox1, Pax3, and MyoD expression. Furthermore, RA downregulated BMP4 expression and upregulated the BMP4 inhibitor, Tob1. Finally, RA inhibited cardiomyogenesis but not in the presence of BMP4. Conclusion RA can enhance skeletal myogenesis in stem cells at the muscle specification/progenitor stage by activating RARs bound directly to mesoderm and skeletal muscle progenitor genes, activating β-catenin function and inhibiting bone morphogenetic protein (BMP) signalling. Thus, a signalling pathway can function at multiple levels to positively regulate a developmental program and can function by abrogating inhibitory pathways. Finally, since RA enhances skeletal muscle progenitor formation, it will be a valuable tool for designing future stem cell therapies.

Neuronal loss in Parkinson's disease (PD) is associated with aberrant mitochondrial function and impaired proteostasis. Identifying the mechanisms that link these pathologies is critical to furthering our understanding of PD pathogenesis. Using human pluripotent stem cells (hPSCs) that allow comparison of cells expressing mutant SNCA (encoding α-synuclein (α-syn)) with isogenic controls, or SNCA-transgenic mice, we show that SNCA-mutant neurons display fragmented mitochondria and accumulate α-syn deposits that cluster to mitochondrial membranes in response to exposure of cardiolipin on the mitochondrial surface. Whereas exposed cardiolipin specifically binds to and facilitates refolding of α-syn fibrils, prolonged cardiolipin exposure in SNCA-mutants initiates recruitment of LC3 to the mitochondria and mitophagy. Moreover, we find that co-culture of SNCA-mutant neurons with their isogenic controls results in transmission of α-syn pathology coincident with mitochondrial pathology in control neurons. Transmission of pathology is effectively blocked using an anti-α-syn monoclonal antibody (mAb), consistent with cell-to-cell seeding of α-syn.