Plasmonic Assemblies for Real-Time Single-Molecule Biosensing.

Their tunable optical properties and versatile surface functionalization have sparked applications of plasmonic assemblies in the fields of biosensing, nonlinear optics, and photonics. Particularly, in the field of biosensing, rapid advances have occurred in the use of plasmonic assemblies for real-time single-molecule sensing. Compared to individual particles, the use of assemblies as sensors provides stronger signals, more control over the optical properties, and access to a broader range of timescales. In the past years, they have been used to directly reveal single-molecule interactions, mechanical properties, and conformational dynamics. This review summarizes the development of real-time single-molecule sensors built around plasmonic assemblies. First, a brief overview of their optical properties is given, and then recent applications are described. The current challenges in the field and suggestions to overcome those challenges are discussed in detail. Their stability, specificity, and sensitivity as sensors provide a complementary approach to other single-molecule techniques like force spectroscopy and single-molecule fluorescence. In future applications, the impact in real-time sensing on ultralong timescales (hours) and ultrashort timescales (sub-millisecond), time windows that are difficult to access using other techniques, is particularly foreseen.

Heterogeneous Kinetics in the Functionalization of Single Plasmonic Nanoparticles.

The functionalization of gold nanoparticles with DNA has been studied extensively in solution; however, these ensemble measurements do not reveal particle-to-particle differences. Here we study the functionalization of gold nanorods with thiolated single-stranded DNA (ssDNA) at the single-particle level. We exploit the sensitivity of the plasmon resonance to the local refractive index to study the functionalization in real time using single-particle spectroscopy. We find particle-to-particle variations of the plasmon shift that are attributed to the particle size distribution and variations in ssDNA coverage. We find that the ssDNA coverage varies by ∼10% from particle to particle, beyond the expected variation due to Poisson statistics. Surprisingly, we find binding rates that differ from particle to particle by an order of magnitude, even though the buffer conditions are identical. We ascribe this heterogeneity to a distribution of activation energies caused by particle-to-particle variations in effective surface charge. These results yield insight into the kinetics of biofunctionalization at the single particle level and highlight that significant kinetic heterogeneity has to be taken into account in applications of functional particles. The presented methodology is easily extended to any nanoparticle coating and can be used to optimize functionalization protocols.

Applying refinement to the use of mice and rats in rheumatoid arthritis research.

Rheumatoid arthritis (RA) is a painful, chronic disorder and there is currently an unmet need for effective therapies that will benefit a wide range of patients. The research and development process for therapies and treatments currently involves in vivo studies, which have the potential to cause discomfort, pain or distress. This Working Group report focuses on identifying causes of suffering within commonly used mouse and rat 'models' of RA, describing practical refinements to help reduce suffering and improve welfare without compromising the scientific objectives. The report also discusses other, relevant topics including identifying and minimising sources of variation within in vivo RA studies, the potential to provide pain relief including analgesia, welfare assessment, humane endpoints, reporting standards and the potential to replace animals in RA research.

Rationally manipulating aptamer binding affinities in a stem-loop molecular beacon.

Single-stranded DNA sequences that are highly specific for a target ligand are called aptamers. While the incorporation of aptamer sequences into stem-loop molecular beacons has become an essential tool in optical biosensors, the design principles that determine the magnitude of binding affinity and its relationship to placement of the aptamer sequence in the stem-loop architecture are not well defined. By controlled placement of the aptamer along the loop region of the molecular beacon, it is observed that the binding affinity can be tuned over 4 orders of magnitude (1.3 nM - 203 µM) for the Huizenga and Szostak ATP DNA aptamer sequence. It is observed that the Kd is enhanced for the fully exposed sequence, with reduced binding affinity when the aptamer is part of the stem region of the beacon. Analysis of the ΔG values indicate a clear correlation between the aptamer hybridized length in the stem and its observed Kd. The use of a nanometal surface energy transfer probe method for monitoring ATP binding to the aptamer sequence allows the observation of negative cooperativity between the two ATP binding events. Maintenance of the high binding affinity of this ATP aptamer and the observation of two separate Kd's for ATP binding indicate NSET as an effective, nonmanipulative, optical method for tracking biomolecular changes.

Beyond survival: how well do transplanted livers work? A preliminary comparison of standard-risk, high-risk, and living donor recipients.

To help decrease mortality on the liver transplant waitlist, transplant centers are using living donors (LD) and high-risk donors (HRD) in addition to standard-risk donors (SRD). HRD is defined as having a donor risk index score higher than 1.6, which suggests a great risk of graft failure. Recent studies have examined survival rates between HRD and SRD recipients; however, little is known about outcomes other than survival, specifically psychosocial outcomes. The purpose of this preliminary, prospective study was to compare post-transplant psychosocial and recovery outcomes between SRD and LD and HRD liver recipients. These outcomes include cognitive functioning, psychological distress, quality of life, and self-reported and objective measures of recovery. Eighty-four patients provided baseline and six-month post-transplant data. There were generally no statistically significant differences at baseline or the six-month follow-up, suggesting that patients receiving HRD livers have similar outcomes to those who receive SRD livers. However, some effect sizes suggest potential advantages for LD recipients compared to SRD recipients. Transplant centers may be more willing to encourage patients to accept HRD or LD livers knowing that they may have comparable outcomes to SRD recipients, which also has implications for the transplant waitlist.

To eat or not to eat; is that really the question? An evaluation of problematic eating behaviors and mental health among bariatric surgery candidates.

Problematic eating behaviors, such as emotional eating, and food addiction, may affect weight; however, little is known about these eating behaviors, especially among those seeking bariatric surgery. Therefore, the purpose of this study was to estimate the prevalence of problematic eating behaviors and to investigate their relationship with other eating behaviors, body mass index (BMI), and psychiatric symptoms. There were 142 patients who completed a required psychiatric evaluation prior to bariatric surgery. Of these, 16.9 % met criteria for a food addiction and 25.4-40.7 % endorsed emotional eating, depending on type of emotional eating. The number of food addiction symptoms endorsed was related to emotional eating. Both food addiction and emotional eating were related to anxiety and depressive symptoms. However, surprisingly, BMI was not related to a food addiction diagnosis, emotional eating scores, or psychiatric symptoms. Results from this study suggest that problematic eating behaviors are occurring among bariatric surgery candidates. Furthermore, this study may help to address the conflicting research regarding the effects of psychiatric symptoms on weight-loss outcomes. Perhaps it is the problematic eating behaviors (e.g., food addiction and emotional eating) that are associated with psychiatric symptoms that could be influencing outcomes. Future research should evaluate treatments for problematic eating behaviors and whether treatments improve weight-loss success.

Management of primary spontaneous pneumothorax: Did practice change after a landmark multicentre study?

OBJECTIVE: To compare management of primary spontaneous pneumothorax (PSP) before and after the completion of multicentre study which showed non-inferiority of conservative compared to interventional treatment for PSP. METHODS: This is a retrospective study of patients aged 14-50 years with a first diagnosis of medium to large PSP before and after March 2019 in a tertiary ED. Medical record and radiology database review were used to identify demographic, clinical and radiological data. RESULTS: The proportion of patients receiving an intervention in the ED decreased from 31.3% (10/32) to 12.5% (3/24). CONCLUSION: Intervention for management of PSP is less frequent, suggesting adoption and implementation of best evidence.

A concept for international societally relevant microbiology education and microbiology knowledge promulgation in society.

EXECUTIVE SUMMARY: Microbes are all pervasive in their distribution and influence on the functioning and well-being of humans, life in general and the planet. Microbially-based technologies contribute hugely to the supply of important goods and services we depend upon, such as the provision of food, medicines and clean water. They also offer mechanisms and strategies to mitigate and solve a wide range of problems and crises facing humanity at all levels, including those encapsulated in the sustainable development goals (SDGs) formulated by the United Nations. For example, microbial technologies can contribute in multiple ways to decarbonisation and hence confronting global warming, provide sanitation and clean water to the billions of people lacking them, improve soil fertility and hence food production and develop vaccines and other medicines to reduce and in some cases eliminate deadly infections. They are the foundation of biotechnology, an increasingly important and growing business sector and source of employment, and the centre of the bioeconomy, Green Deal, etc. But, because microbes are largely invisible, they are not familiar to most people, so opportunities they offer to effectively prevent and solve problems are often missed by decision-makers, with the negative consequences this entrains. To correct this lack of vital knowledge, the International Microbiology Literacy Initiative-the IMiLI-is recruiting from the global microbiology community and making freely available, teaching resources for a curriculum in societally relevant microbiology that can be used at all levels of learning. Its goal is the development of a society that is literate in relevant microbiology and, as a consequence, able to take full advantage of the potential of microbes and minimise the consequences of their negative activities. In addition to teaching about microbes, almost every lesson discusses the influence they have on sustainability and the SDGs and their ability to solve pressing problems of societal inequalities. The curriculum thus teaches about sustainability, societal needs and global citizenship. The lessons also reveal the impacts microbes and their activities have on our daily lives at the personal, family, community, national and global levels and their relevance for decisions at all levels. And, because effective, evidence-based decisions require not only relevant information but also critical and systems thinking, the resources also teach about these key generic aspects of deliberation. The IMiLI teaching resources are learner-centric, not academic microbiology-centric and deal with the microbiology of everyday issues. These span topics as diverse as owning and caring for a companion animal, the vast range of everyday foods that are produced via microbial processes, impressive geological formations created by microbes, childhood illnesses and how they are managed and how to reduce waste and pollution. They also leverage the exceptional excitement of exploration and discovery that typifies much progress in microbiology to capture the interest, inspire and motivate educators and learners alike. The IMiLI is establishing Regional Centres to translate the teaching resources into regional languages and adapt them to regional cultures, and to promote their use and assist educators employing them. Two of these are now operational. The Regional Centres constitute the interface between resource creators and educators-learners. As such, they will collect and analyse feedback from the end-users and transmit this to the resource creators so that teaching materials can be improved and refined, and new resources added in response to demand: educators and learners will thereby be directly involved in evolution of the teaching resources. The interactions between educators-learners and resource creators mediated by the Regional Centres will establish dynamic and synergistic relationships-a global societally relevant microbiology education ecosystem-in which creators also become learners, teaching resources are optimised and all players/stakeholders are empowered and their motivation increased. The IMiLI concept thus embraces the principle of teaching societally relevant microbiology embedded in the wider context of societal, biosphere and planetary needs, inequalities, the range of crises that confront us and the need for improved decisioning, which should ultimately lead to better citizenship and a humanity that is more sustainable and resilient. ABSTRACT: The biosphere of planet Earth is a microbial world: a vast reactor of countless microbially driven chemical transformations and energy transfers that push and pull many planetary geochemical processes, including the cycling of the elements of life, mitigate or amplify climate change (e.g., Nature Reviews Microbiology, 2019, 17, 569) and impact the well-being and activities of all organisms, including humans. Microbes are both our ancestors and creators of the planetary chemistry that allowed us to evolve (e.g., Life's engines: How microbes made earth habitable, 2023). To understand how the biosphere functions, how humans can influence its development and live more sustainably with the other organisms sharing it, we need to understand the microbes. In a recent editorial (Environmental Microbiology, 2019, 21, 1513), we advocated for improved microbiology literacy in society. Our concept of microbiology literacy is not based on knowledge of the academic subject of microbiology, with its multitude of component topics, plus the growing number of additional topics from other disciplines that become vitally important elements of current microbiology. Rather it is focused on microbial activities that impact us-individuals/communities/nations/the human world-and the biosphere and that are key to reaching informed decisions on a multitude of issues that regularly confront us, ranging from personal issues to crises of global importance. In other words, it is knowledge and understanding essential for adulthood and the transition to it, knowledge and understanding that must be acquired early in life in school. The 2019 Editorial marked the launch of the International Microbiology Literacy Initiative, the IMiLI. HERE, WE PRESENT: our concept of how microbiology literacy may be achieved and the rationale underpinning it; the type of teaching resources being created to realise the concept and the framing of microbial activities treated in these resources in the context of sustainability, societal needs and responsibilities and decision-making; and the key role of Regional Centres that will translate the teaching resources into local languages, adapt them according to local cultural needs, interface with regional educators and develop and serve as hubs of microbiology literacy education networks. The topics featuring in teaching resources are learner-centric and have been selected for their inherent relevance, interest and ability to excite and engage. Importantly, the resources coherently integrate and emphasise the overarching issues of sustainability, stewardship and critical thinking and the pervasive interdependencies of processes. More broadly, the concept emphasises how the multifarious applications of microbial activities can be leveraged to promote human/animal, plant, environmental and planetary health, improve social equity, alleviate humanitarian deficits and causes of conflicts among peoples and increase understanding between peoples (Microbial Biotechnology, 2023, 16(6), 1091-1111). Importantly, although the primary target of the freely available (CC BY-NC 4.0) IMiLI teaching resources is schoolchildren and their educators, they and the teaching philosophy are intended for all ages, abilities and cultural spectra of learners worldwide: in university education, lifelong learning, curiosity-driven, web-based knowledge acquisition and public outreach. The IMiLI teaching resources aim to promote development of a global microbiology education ecosystem that democratises microbiology knowledge.

Towards the microbial home: An overview of developments in next-generation sustainable architecture.

Disruptive innovation is needed to raise the threshold of sustainable building performance, so that our buildings improve on net zero impacts and have a life-promoting impact on the natural world. This article outlines a new approach to next-generation sustainable architecture, which draws on the versatile metabolisms of microbes as a platform by incorporating microbial technologies and microbially produced materials into the practice of the built environment. The regenerative architecture arising from these interventions includes a broad range of advances from using new materials, to creating bioreceptive surfaces that promote life, and providing green, bio-remediating energy from waste. Such innovations are presently reaching the marketplace as novel materials like Biocement® with lower embodied carbon than conventional materials that adopt microbially facilitated processes, and as novel utilities like PeePower® that transforms urine into electrical energy and bioreactor-based building systems such as the pioneering BIQ building in Hamburg. While the field is still young, some of these products (e.g. mycelium biocomposites) are poised for uptake by the public-private economic axis to become mainstream within the building industry. Other developments are creating new economic opportunities for local maker communities that empower citizens and catalyse novel vernacular building practices. In particular, the activation of the microbial commons by the uptake of microbial technologies and materials through daily acts of living, 'democratises' resource harvesting (materials and energy) in ways that sustain life, and returns important decisions about how to run a home back to citizens. This disruptive move re-centres the domestic-commons economic axis to the heart of society, setting the stage for new vernacular architectures that support increasingly robust and resilient communities.

Medical Evaluation Readiness Information Toolset (MERIT): Developing a Data-driven Decision Support Tool to Augment Complex Clinical Decisions.

INTRODUCTION: Medical readiness continues to be a significant concern for the military. DoD policy directs medical authorities to refer service members to the Disability Evaluation System (DES) when the course of further recovery is relatively predictable or within 1 year of diagnosis, whichever is sooner. The Medical Evaluation Readiness Information Toolset (MERIT) is an application that leverages artificial intelligence within a clinical decision support tool to provide clinicians with predictions of a service member's likelihood of referral to the DES for the top 24 medical conditions that result in separation from the service, which represent more than 90% of all referral cases to the DES since 2000. MATERIALS AND METHODS: Data spanned 19 years and contained records for over 3 million army service members. The MERIT team incorporated a novel approach using a Gamma window function to weight recent medical data more than older medical data in the creation of a "Disease Severity Index" (DSI) that summarized the progression of a health deterioration process per medical condition code. Time-dependent medical encounter data were aggregated into an individual-level DSI. The identified features including the DSI were used in logistic regression and random forest models to predict whether a service member is likely to be referred to the DES. Models were constructed for each of the top 24 unfitting medical conditions. RESULTS: MERIT produced a set of high-performing classification models with area under the receiver operating characteristics curves across all conditions exceeding 0.919 using logistic regression for all conditions. CONCLUSIONS: This project demonstrated with a high degree of accuracy that MERIT, using a combination of ICD codes and personnel records, can be used to develop an individual risk profile for each service member.

Addressing Emergency Department Care for Patients Experiencing Incarceration: A Narrative Review.

Patients experiencing incarceration face a multitude of healthcare disparities. These patients are disproportionately affected by a variety of chronic medical conditions. Patients who are incarcerated often remain shackled throughout their hospital course, experience bias from members of the healthcare team, and have many barriers to privacy given the omnipresence of corrections officers. Despite this, many physicians report little formal training on caring for this unique patient population. In this narrative review, we examine the current literature on patients who are incarcerated, especially as it pertains to their care in the emergency department (ED).We also propose solutions to address these barriers to care in the ED setting.

Notes From the Field: Diverse Partner Perspectives Improve the Usability and Equity Focus of Implementation Guides.

Context: School-based asthma programs (SBAPs) have improved health and educational disparities among youth with asthma. Design: To support scaling out effective SBAPs, our school partners identified a need for online implementation guides that are "always available," to meet the needs of school nurses' demanding schedules. School nurses play a key role in the adoption and implementation of SBAPs, so it is important to ensure the implementation guide would be highly usable and acceptable to them. Objective: Accordingly, our research team collaborated with human-centered design experts to identify the "user journeys" of school nurses and co-created our online implementation guide as a public-facing website with input from local and national school nurse partners. Main Results: In this perspectives article, our school nurse implementation partners and human-centered design experts reflect on challenges overcome in this process of developing a tailored implementation guide to school nurses and offer lessons from the field to others seeking to co-create implementation guides with community partners.

The Identification of GPR52 Agonist HTL0041178, a Potential Therapy for Schizophrenia and Related Psychiatric Disorders.

HTL0041178 (1), a potent GPR52 agonist with a promising pharmacokinetic profile and exhibiting oral activity in preclinical models, has been identified. This molecule was the outcome of a judicious molecular property-based optimization approach, focusing on balancing potency against metabolic stability, solubility, permeability, and P-gp efflux.

Developing a Social Determinants of Health Needs Assessment for Colorado Kids (SNACK) Tool for a School-Based Asthma Program: Findings from a Pilot Study.

Background: School-based asthma programs effectively address poorly controlled asthma and asthma disparities, especially when coupled with screening for and addressing social determinants of health (SDOH) needs. Existing screening tools are tailored to clinical settings; therefore, we sought to develop a community-based SDOH screening tool. Design/Methods: We used a four-phase iterative design process to develop and pilot a community-based screening tool. We used a modified Delphi process to identify screening tool domains, identified validated items for inclusion, and developed an appropriate tool layout for populations with limited health/general literacy. Community advisory boards reviewed and refined a draft tool. Next, we conducted a qualitative pilot test of acceptability to parents and feasibility for staff in a community health center. Results: Six domains are included in our SDOH screening tool: health care access, transportation, food insecurity, public benefits, housing, and utilities. In the pilot test, 41 screenings were completed, and 36 parents (16.7% Spanish speaking) provided feedback. Most families understood the purpose of the screening; felt that the questions were clear, appropriate, and quick to complete; and liked the pictures. The clinic's care coordinator expressed a preference for the pilot tool compared to their existing screening tool and recommended improvements to encourage honest reporting by patients. Conclusion: This community-based screening tool addresses key SDOH needs that impact asthma and is acceptable to families. The next steps are to implement the tool in school-based asthma programs to support improvements in asthma outcomes and disparities by identifying and addressing families' unmet SDOH needs.

Heart rate variability and baroreceptor sensitivity following exercise-induced hyperthermia in endurance trained men.

We evaluated the effect of exercise-induced hyperthermia (EIH) on autonomic nervous system (ANS) function in the early (<80 min) and late (24 and 48 h) stages of recovery. Eight males underwent three repeated 6 min 70° head-up tilts (HUT1, HUT2 and HUT3), each separated by 10-min supine rest in a non-exercise/non-heat stress control state (NHS). On a separate day, three 6 min 70° HUT were performed following EIH (esophageal temperature ≥ 40°C) and repeated after 24 and 48 h of recovery. Heart rate, stroke volume (SV), mean arterial pressure and cardiac output ([Formula: see text]) were evaluated during the last min prior to a change in posture. Responses to 70° HUT were compared to the same challenge performed without prior exercise and under a NHS condition. Relative to NHS, [Formula: see text] was maintained during the repeated HUT's following EIH, despite significant reductions in SV and sustained elevations in esophageal temperature (p < 0.05). The preserved [Formula: see text] appears to be due to increased HR (HUT1: NRS = 76 ± 3 beats min(-1), EIH = 126 ± 6 beats min(-1)) stemming from modulation of the ANS toward sympathetic dominance. Parasympathetic withdrawal was evidenced by a reduction in root mean squared successive difference (i.e., HUT1: NHS = 66 ± 12 ms, EIH = 9 ± 1 ms) of heart rate variability and paralleled by a reduction in baroreceptor sensitivity for all HUT's following EIH (p < 0.05). Despite significant modulation in ANS activity, Q is maintained and participants do not become orthostatic intolerant/syncopal during the short-term recovery period following EIH. Normal ANS and cardiovascular function is restored following 24 h of recovery.

Influence of nonthermal baroreceptor modulation of heat loss responses during uncompensable heat stress.

We evaluated the hypothesis that with increasing levels of hyperthermia, thermal influences would predominate over nonthermal baroreceptor control of cutaneous vascular conductance (CVC) and local sweat rate (LSR). On separate days, eight male participants were positioned in either an upright seated posture (URS) or a 15 degrees head-down tilt (HDT) posture in a thermoneutral condition and during passive heating, until mean body temperature (T(body)) increased by 1.5 degrees C. Hemodynamic [heart rate (HR), cardiac output, mean arterial pressure (MAP)] and thermal responses [T(re), CVC, LSR] were measured continuously. MAP showed a gradual decrease in the early- to mid-stages of heating for both HDT and URS. At a T(body) > 0.6 degrees C, MAP achieved a stable, albeit reduced level from baseline resting for the duration of the heating, whereas MAP decreased significantly throughout the heating period in the URS position (p < 0.001). CVC increased rapidly in the early stages of heating and achieved a stable elevated level in both HDT and URS at the mid-stage of heating (T(body) increase

Cardiovascular and thermal responses to repeated head-up tilts following exercise-induced heat stress.

BACKGROUND: We evaluated the acute cardiovascular and thermoregulatory responses to repeated 70 degrees head-up tilts (HUT) performed following exercise-induced hyperthermia. METHODS: Eight male subjects underwent intermittent episodes of 70 degrees HUT in either a non-exercise/ non-heat stress state (NH) or an exercise-induced hyperthermic state (EIH). Subjects remained supine for 30 min in a thermoneutral environment (22 degrees C) and were subsequently exposed to three successive 6-min 70 degrees head-up tilts (HUT1, HUT2, HUT3), each separated by 10 min of supine resting. During EIH, subjects were rendered hyperthermic by exercise in the heat (core temperature of approximately 40.0 degrees C) and were then transferred to an ambient temperature of 22 degrees C. We evaluated the relative change in hemodynamic and thermal responses from the last minute in the supine position preceding the HUT to the final minute in HUT. RESULTS: While we measured a difference in the relative change in heart rate between conditions for all HUTs, no differences were observed in mean arterial pressure (MAP), total peripheral resistance, or cardiac output. A reduced change in baroreceptor sensitivity was measured in EIH for HUT1 only (-2 +/- 1 ms x mmHg(-1) following EIH compared to -13 +/- 3 ms x mmHg(-1) during NH). A significant transient reduction in cutaneous vascular conductance (CVC) occurred during HUT1 and HUT2 following EIH (-20 +/- 5% CVCmax and -9 +/- 3 %CVCmax, respectively), despite significant elevations in core temperature above resting levels (i.e., 1.4 degrees C and 0.9 degrees C for HUT1 and HUT2). CONCLUSION: We conclude that the maintenance of MAP following exercise in the heat is mitigated by reductions in skin perfusion despite significant elevations in core temperature.

A 30% Volumetric Muscle Loss Does Not Result in Sustained Functional Deficits after a 90-Day Recovery in Rats.

Volumetric muscle loss (VML) is defined as the loss of skeletal muscle tissue which exceeds the body's repair capabilities leading to sustained functional deficits over time. Some etiologies leading to VML include traumatic injuries, congenital diseases, and degenerative myopathies. Currently, the lack of standardized animal models prevents an appropriate estimation of the severity of injury capable of exceeding self-regeneration. Recent work in our laboratory has shown that a 30% VML does not create a sustained functional loss in rats after 3 months. Therefore, the purpose of this study was to evaluate the percentage threshold of muscle loss that results in permanent functional deficits. We surgically created models of 30, 40, and 50% VML injuries in the tibialis anterior (TA) of rats, and subsequently evaluated TA function and structure after a 90-day recovery period. TA muscle force production was measured in situ by stimulating the sciatic nerve to obtain a maximum tetanic force. Results revealed that the maximum force produced by rats with a 30% VML was not significantly different from the uninjured muscle, while the maximum force of the 40% and 50% VML groups was significantly lower in comparison to the uninjured muscle. Overall, this study further supports our observations, suggesting that a 30% VML rat model is not suitable for VML studies. Thus, increasing VML percentages might provide an improved standardized and clinically relevant model for VML that produces a long-term deficit in muscle self-regeneration, while providing a strong base for future tissue engineering techniques in medicine.

A Comparison of Ovine Facial and Limb Muscle as a Primary Cell Source for Engineered Skeletal Muscle.

Volumetric muscle loss (VML) contributes to the number of soft tissue injuries that necessitate reconstructive surgery, but treatment options are often limited by tissue availability and donor site morbidity. To combat these issues, our laboratory has developed scaffold-free tissue-engineered skeletal muscle units (SMUs) as a novel treatment for VML injuries. Recently, we have begun experiments addressing VML in facial muscle, and the optimal starting cell population for engineered skeletal muscle tissue for this application may not be cells derived from hindlimb muscles due to reported heterogeneity of cell populations. Thus, the purpose of this study was to compare SMUs fabricated from both craniofacial and hindlimb sources to determine which cell source is best suited for the engineering of skeletal muscle. Herein, we assessed the development, structure, and function of SMUs derived from four muscle sources, including two hindlimb muscles (i.e., soleus and semimembranosus [SM]) and two craniofacial muscles (i.e., zygomaticus major and masseter). Overall, the zygomaticus major exhibited the least efficient digestion, and SMUs fabricated from this muscle exhibited the least aligned myosin heavy chain staining and consequently, the lowest average force production. Conversely, the SM muscle exhibited the most efficient digestion and the highest number of myotubes/mm2; however, the SM, masseter, and soleus groups were roughly equivalent in terms of force production and histological structure. Impact Statement An empirical comparison of the development, structure, and function of engineered skeletal muscle tissue fabricated from different muscles, including both craniofacial and hindlimb sources, will not only provide insight into innate regenerative mechanisms of skeletal muscle but also will give our team and other researchers the information necessary to determine which cell sources are best suited for the skeletal muscle tissue engineering.

Repairing Volumetric Muscle Loss in the Ovine Peroneus Tertius Following a 3-Month Recovery.

Much effort has been made to fabricate engineered tissues on a scale that is clinically relevant to humans; however, scale-up remains one of the most significant technological challenges of tissue engineering to date. To address this limitation, our laboratory has developed tissue-engineered skeletal muscle units (SMUs) and engineered neural conduits (ENCs), and modularly scaled them to clinically relevant sizes for the treatment of volumetric muscle loss (VML). The goal of this study was to evaluate the SMUs and ENCs in vitro, and to test the efficacy of our SMUs and ENCs in restoring muscle function in a clinically relevant large animal (sheep) model. The animals received a 30% VML injury to the peroneus tertius muscle and were allowed to recover for 3 months. The animals were divided into three experimental groups: VML injury without a repair (VML only), repair with an SMU (VML+SMU), or repair with an SMU and ENC (VML+SMU+ENC). We evaluated the SMUs before implantation and found that our single scaled-up SMUs were characterized by the presence of contracting myotubes, linearly aligned extracellular matrix proteins, and Pax7+ satellite cells. Three months after implantation, we found that the repair groups (VML+SMU and VML+SMU+ENC) had restored muscle mass and tetanic force production to a level that was statistically indistinguishable from the uninjured contralateral muscle after 3 months in vivo. Furthermore, we demonstrated the ability of our ENCs to effectively bridge the gap between native nerve and the repair site by eliciting a muscle contraction through direct electrical stimulation of the re-routed nerve. Impact statement The fabrication of tissues of clinically relevant sizes is one of the largest obstacles preventing engineered tissues from achieving widespread use in the clinic. This study aimed to combat this limitation by developing a fabrication method to scale-up tissue-engineered skeletal muscle for the treatment of volumetric muscle loss in a large animal (sheep) model and evaluating the efficacy of the tissue-engineered constructs after a 3-month recovery.