Eadem Sed Aliter. Validating an emergency department work domain analysis across three hospital configurations.

Work Domain Analysis (WDA), the foundational phase in the Cognitive Work Analysis Framework (CWA), provides a platform for understanding and designing complex systems. Though it has been used extensively, there are few applications in healthcare, and model validation for different contexts is not always undertaken. The current study aimed to validate an Emergency Department (ED) WDA across three metropolitan hospitals that differ in the type and nature of services they provide, including the ED in which the original ED WDA was developed. A facilitated workshop was conducted at the first ED and interviews at two subsequent EDs to refine and validate the ED WDA. ED subject matter experts (SMEs) including nurses, doctors, administration, and allied health personnel provided feedback on the model. SME feedback resulted in modifications to the original ED WDA model including combining nodes to reduce duplication and amending five labels for clarity. The resulting WDA provides a valid representation of the EDs found in metropolitan districts within an Australian state and can be used by roles such as frontline ED clinicians, hospital managers, and policy developers to facilitate the design, testing, and sharing of solutions to local and shared problems. The findings also demonstrate the importance of validating WDA models across different contexts.

Ethical and regulatory implications of the COVID-19 pandemic for the medical devices industry and its representatives.

The development and deployment of medical devices, along with most areas of healthcare, has been significantly impacted by the COVID-19 pandemic. This has had variable ethical implications, two of which we will focus on here. First, medical device regulations have been rapidly amended to expedite approvals of devices ranging from face masks to ventilators. Although some regulators have issued cessation dates, there is inadequate discussion of triggers for exiting these crisis standards, and evidence that this may not be feasible. Given the relatively low evidence standards currently required for regulatory approval of devices, this further indefinite reduction in standards raises serious ethical issues. Second, the pandemic has disrupted the usual operations of device representatives in hospitals, providing an opportunity to examine and refine this potentially ethically problematic practice. In this paper we explain and critically analyse the ethical implications of these two pandemic-related impacts on medical devices and propose suggestions for their management. These include an endpoint for pandemic-related adjustments to device regulation or a mechanism for continued refinement over time, together with a review of device research conducted under crisis conditions, support for the removal and replacement of emergency approved devices, and a review of device representative credentialling.

Identifying Constraints on Everyday Clinical Practice: Applying Work Domain Analysis to Emergency Department Care.

BACKGROUND: Emergency departments (EDs) are complex socio-technical work systems that require staff to manage patients in an environment of fluctuating resources and demands. To better understand the purpose, and pressures and constraints for designing new ED facilities, we developed an abstraction hierarchy model as part of a work domain analysis (WDA) from the cognitive work analysis (CWA) framework. The abstraction hierarchy provides a model of the structure of the ED, encompassing the core objects, processes, and functions relating to key values and the ED's overall purpose. METHODS: Reviews of relevant national and state policy, guidelines, and protocol documents applicable to care delivery in the ED were used to construct a WDA. The model was validated through focus groups with ED clinicians and subsequently validated using a series of WDA prompts. RESULTS: The model shows that the ED system exhibits extremely interconnected and complex features. Heavily connected functions introduce vulnerability into the system with function performance determined by resource availability and prioritization, leading to a trade-off between time and safety priorities. CONCLUSIONS: While system processes (e.g., triage, fast-track) support care delivery in ED, this delivery manifests in complex ways due to the personal and disease characteristics of patients and the dynamic state of the ED system. The model identifies system constraints that create tension in care delivery processes (e.g., electronic data entry, computer availability) potentially compromising patient safety. APPLICATION: The model identified aspects of the ED system that could be leveraged to improve ED performance through innovative ED system design.

Guideline adherence in the management of attention deficit hyperactivity disorder in children: An audit of selected medical records in three Australian states.

OBJECTIVE: To assess General Practitioner (GP) and pediatrician adherence to clinical practice guidelines (CPGs) for diagnosis, treatment and management of attention deficit hyperactivity disorder (ADHD). METHOD: Medical records for 306 children aged ≤15 years from 46 GP clinics and 20 pediatric practices in Australia were reviewed against 34 indicators derived from CPG recommendations. At indicator level, adherence was estimated as the percentage of indicators with 'Yes' or 'No' responses for adherence, which were scored 'Yes'. This was done separately for GPs, pediatricians and overall; and weighted to adjust for sampling processes. RESULTS: Adherence with guidelines was high at 83.6% (95% CI: 77.7-88.5) with pediatricians (90.1%; 95% CI: 73.0-98.1) higher than GPs (68.3%; 95% CI: 46.0-85.8; p = 0.02). Appropriate assessment for children presenting with signs or symptoms of ADHD was undertaken with 95.2% adherence (95% CI: 76.6-99.9), however ongoing reviews for children with ADHD prescribed stimulant medication was markedly lower for both pediatricians (51.1%; 95% CI: 9.6-91.4) and GPs (18.7%; 95% CI: 4.1-45.5). CONCLUSION: Adherence to CPGs for ADHD by pediatricians was generally high. Adherence by GPs was lower across most domains; timely recognition of medication side effects is a particular area for improvement.

Strategies to measure and improve emergency department performance: a scoping review.

BACKGROUND: Over the last two decades, Emergency Department (ED) crowding has become an increasingly common occurrence worldwide. Crowding is a complex and challenging issue that affects EDs' capacity to provide safe, timely and quality care. This review aims to map the research evidence provided by reviews to improve ED performance. METHODS AND FINDINGS: We performed a scoping review, searching Cochrane Database of Systematic Reviews, Scopus, EMBASE, CINAHL and PubMed (from inception to July 9, 2019; prospectively registered in Open Science Framework https://osf.io/gkq4t/). Eligibility criteria were: (1) review of primary research studies, published in English; (2) discusses a) how performance is measured in the ED, b) interventions used to improve ED performance and their characteristics, c) the role(s) of patients in improving ED performance, and d) the outcomes attributed to interventions used to improve ED performance; (3) focuses on a hospital ED context in any country or healthcare system. Pairs of reviewers independently screened studies' titles, abstracts, and full-texts for inclusion according to pre-established criteria. Discrepancies were resolved via discussion. Independent reviewers extracted data using a tool specifically designed for the review. Pairs of independent reviewers explored the quality of included reviews using the Risk of Bias in Systematic Reviews tool. Narrative synthesis was performed on the 77 included reviews. Three reviews identified 202 individual indicators of ED performance. Seventy-four reviews reported 38 different interventions to improve ED performance: 27 interventions describing changes to practice and process (e.g., triage, care transitions, technology), and a further nine interventions describing changes to team composition (e.g., advanced nursing roles, scribes, pharmacy). Two reviews reported on two interventions addressing the role of patients in ED performance, supporting patients' decisions and providing education. The outcomes attributed to interventions used to improve ED performance were categorised into five key domains: time, proportion, process, cost, and clinical outcomes. Few interventions reported outcomes across all five outcome domains. CONCLUSIONS: ED performance measurement is complex, involving automated information technology mechanisms and manual data collection, reflecting the multifaceted nature of ED care. Interventions to improve ED performance address a broad range of ED processes and disciplines.

Variability in clinicians' understanding and reported methods of identifying high-risk surgical patients: a qualitative study.

BACKGROUND: High-risk patients presenting for surgery require complex decision-making and perioperative management. However, given there is no gold standard for identifying high-risk patients, doing so may be challenging for clinicians in practice. Before a gold standard can be established, the state of current practice must be determined. This study aimed to understand how working clinicians define and identify high-risk surgical patients. METHODS: Clinicians involved in the care of high-risk surgical patients at a public hospital in regional Australia were interviewed as part of an ongoing study evaluating a new shared decision-making process for high-risk patients. The new process, Patient-Centred Advanced Care Planning (PC-ACP) engages patients, families, and clinicians from all relevant specialties in shared decision-making in line with the patient's goals and values. The semi-structured interviews were conducted before the implementation of the new process and were coded using a modified form of the 'constant comparative method' to reveal key themes. Themes concerning patient risk, clinician's understanding of high risk, and methods for identifying high-risk surgical patients were extricated for close examination. RESULTS: Thirteen staff involved in high-risk surgery at the hospital at which PC-ACP was to be implemented were interviewed. Analysis revealed six sub-themes within the major theme of factors related to patient risk: (1) increase in high-risk patients, (2) recognising frailty, (3) risk-benefit balance, (4) suitability and readiness for surgery, (5) avoiding negative outcomes, and (6) methods in use for identifying high-risk patients. There was considerable variability in clinicians' methods of identifying high-risk patients and regarding their definition of high risk. This variability occurred even among clinicians within the same disciplines and specialties. CONCLUSIONS: Although clinicians were confident in their own ability to identify high-risk patients, they acknowledged limitations in recognising frail, high-risk patients and predicting and articulating possible outcomes when consenting these patients. Importantly, little consistency in clinicians' reported methods for identifying high-risk patients was found. Consensus regarding the definition of high-risk surgical patients is necessary to ensure rigorous decision-making.

Evaluation of a hospital-based integrated model of eye care for diabetic retinopathy assessment: a multimethod study.

OBJECTIVES: Diabetic eye disease is a leading cause of blindness but can be mitigated by regular eye assessment. A framework of issues, developed from the literature of barriers to eye assessment, was used to structure an examination of perceptions of a new model of care for diabetic retinopathy from the perspective of staff using the model, and health professionals referring patients to the new service. DESIGN: Multimethod: interviews and focus groups, and a separate survey. SETTING: A new clinic based on an integrated model of care was established at a hospital in outer metropolitan Sydney, Australia in 2017. Funded jointly by Centre for Eye Health (CFEH) and the hospital, the clinic was equipped and staffed by optometrists who work alongside the ophthalmologists in the existing hospital eye clinic. PARTICIPANTS: Five (of seven) hospital staff working in the clinic (ophthalmologists and administrative officers) or referring to it from other departments (endocrinologists); nine optometrists from CFEH who developed or worked in the clinic; 10 community-based optometrists as potential referrers. RESULTS: The new clinic was considered to have addressed known barriers to eye assessment, including access, assistance for patients unable/unwilling to organise eye checks and efficient management of human resources. The clinic optimised known drivers of this model of care: providing clear scope of practice and protocols for shared care between optometrists and ophthalmologists, good communication between referrers and eye professionals and a collegial approach promoting interprofessional trust. Remaining areas of concern were few referrals from general practitioners, fewer referrals from hospital endocrinologists than expected and issues with stretched administrative capacity. There were also perceived mismatches between the priorities of hospital management and aims of the clinic. CONCLUSIONS: The new model was considered to have addressed many of the barriers to assessment. While there remain issues with the model, there were also unexpected benefits.

Improving decision making in acute healthcare through implementation of an intensive care unit (ICU) intervention in Australia: a multimethod study.

OBJECTIVE: To evaluate the implementation of an intensive care unit (ICU) intervention designed to establish rules for making ICU decisions about postsurgery beds. DESIGN: Preintervention/postintervention case study using a multimethod approach, involving two phases of staff interviews, process mapping and collection of administrative data. SETTING: ICU in a 700-bed regional tertiary care hospital in Australia. PARTICIPANTS: 31 interview participants. Phases 1 and 2 participants drawn from three groups of staff: bedside nursing staff in the ICU, ICU specialist doctors and senior management staff involved in oversight of ICU operations. Phase 2 included an additional participant group: staff from surgery and emergency departments. INTERVENTION: Implementation of an ICU escalation plan and introduction of a multidisciplinary morning meeting to determine ICU bed status in accordance with the plan. MAIN OUTCOME MEASURES: Interview data consisted of preintervention staff perceptions of ICU workplace cohesiveness with bed pressure, and postintervention staff perceptions of the escalation plan and ICU performance. Administrative data consisted of bed status (red, amber or green), monthly number of planned elective surgeries requiring an ICU bed and monthly number of elective surgeries cancelled due to unavailability of ICU beds. RESULTS: Improved internal communication, decision making and cohesion within the ICU and better coordination between ICU and other hospital departments. Significant reduction in elective surgeries cancelled due to unavailability of ICU beds, χ21=24.9, p<0.0001. CONCLUSIONS: By establishing rules for decision making around ICU bed allocation, the intervention improved internal professional relationships within the ICU as well as between the ICU and external departments and reduced the number of elective surgeries cancelled.

Compliance with ethical standards in the reporting of donor sources and ethics review in peer-reviewed publications involving organ transplantation in China: a scoping review.

OBJECTIVES: The objective of this study is to investigate whether papers reporting research on Chinese transplant recipients comply with international professional standards aimed at excluding publication of research that: (1) involves any biological material from executed prisoners; (2) lacks Institutional Review Board (IRB) approval and (3) lacks consent of donors. DESIGN: Scoping review based on Arksey and O'Mallee's methodological framework. DATA SOURCES: Medline, Scopus and Embase were searched from January 2000 to April 2017. ELIGIBILITY CRITERIA: We included research papers published in peer-reviewed English-language journals reporting on outcomes of research involving recipients of transplanted hearts, livers or lungs in mainland China. DATA EXTRACTION AND SYNTHESIS: Data were extracted by individual authors working independently following training and benchmarking. Descriptive statistics were compiled using Excel. RESULTS: 445 included studies reported on outcomes of 85 477 transplants. 412 (92.5%) failed to report whether or not organs were sourced from executed prisoners; and 439 (99%) failed to report that organ sources gave consent for transplantation. In contrast, 324 (73%) reported approval from an IRB. Of the papers claiming that no prisoners' organs were involved in the transplants, 19 of them involved 2688 transplants that took place prior to 2010, when there was no volunteer donor programme in China. DISCUSSION: The transplant research community has failed to implement ethical standards banning publication of research using material from executed prisoners. As a result, a large body of unethical research now exists, raising issues of complicity and moral hazard to the extent that the transplant community uses and benefits from the results of this research. We call for retraction of this literature pending investigation of individual papers.

Conflicts of interest in Australia's IVF industry: an empirical analysis and call for action.

In Australia, the growing assisted reproductive technologies (ART) industry has recently received some public criticism. Much of this criticism centres on the concern that doctors are increasingly motivated by profit, rather than patient interests. These concerns appear to suggest that the growing business of ART generates conflicts of interest (COI) for clinicians. While media reports may be rhetorically compelling, claims that ART practice is distorted by COI must be supported by empirical evidence. This preliminary study sought to engage with people involved with the ART industry and map out their concerns related to COI in ART. A small convenience sample of eight professionals was interviewed. Here, we present the major themes uncovered, including a richer understanding of the 'interests' of various parties involved in Australian ART. We then propose a strategy for how this topic could be constructively explored.

Association between the expression of vascular endothelial growth factors and metabolic syndrome or its components: a systematic review and meta-analysis.

BACKGROUND: Several studies have linked vascular endothelial growth factors (VEGFs) with metabolic syndrome or its components. However, there has been no systematic appraisal of the findings of these studies to date. The current systematic review and meta-analysis was conducted to explore this association. METHODS: PubMed, EMBASE, the Cochrane library, and clinical trials registries were used to retrieve peer-reviewed clinical studies that had evaluated the association of VEGFs with metabolic syndrome or its components without applying language and date restrictions. The final search was performed on 29 September 2017. RESULTS: We included 32 studies in this systematic review and meta-analysis, of which 16 studies (19 study arms) were included in the meta-analysis and remaining studies were qualitatively assessed. Overall, VEGF-A, VEGF-B and VEGF-C were strongly associated with metabolic syndrome or its components. The components of metabolic syndrome varied in their association. Obesity was not correlated with increased VEGF-A expression (p = 0.12), whereas VEGF-B and VEGF-C expression was significantly higher in those with obesity. In contrast, hyperglycemia in type 1 diabetes was strongly associated with increased VEGF-A levels (p < 0.00001), as was type 2 diabetes (p = 0.0006). The studies included in the qualitative analysis similarly showed an increase in VEGF family expression in people with metabolic syndrome, and with its components. CONCLUSION: The increased concentrations of vascular endothelial growth factors are variably associated with metabolic syndrome or its components. Each VEGF protein has a unique set of associations with the disease state.

Device representatives in hospitals: are commercial imperatives driving clinical decision-making?

Despite concerns about the relationships between health professionals and the medical device industry, the issue has received relatively little attention. Prevalence data are lacking; however, qualitative and survey research suggest device industry representatives, who are commonly present in clinical settings, play a key role in these relationships. Representatives, who are technical product specialists and not necessarily medically trained, may attend surgeries on a daily basis and be available to health professionals 24 hours a day, 7 days a week, to provide advice. However, device representatives have a dual role: functioning as commissioned sales representatives at the same time as providing advice on approaches to treatment. This duality raises the concern that clinical decision-making may be unduly influenced by commercial imperatives. In this paper, we identify three key ethical concerns raised by the relationship between device representatives and health professionals: (1) impacts on healthcare costs, (2) the outsourcing of expertise and (3) issues of accountability and informed consent. These ethical concerns can be addressed in part through clarifying the boundary between the support and sales aspects of the roles of device representatives and developing clear guidelines for device representatives providing support in clinical spaces. We suggest several policy options including hospital provision of expert support, formalising clinician conduct to eschew receipt of meals and payments from industry and establishing device registries.

Improving outcomes from high-risk surgery: a multimethod evaluation of a patient-centred advanced care planning intervention.

INTRODUCTION: Patients who are frail, have multiple comorbidities or have a terminal illness often have poor outcomes from surgery. However, sole specialists may recommend surgery in these patients without consultation with other treating clinicians or allowing for patient goals. The Patient-Centred Advanced Care Planning (PC-ACP) model of care provides a framework in which a multidisciplinary advanced care plan is devised to incorporate high-risk patients' values and goals. Decision-making is performed collaboratively by patients, their family, surgeons, anaesthetists, intensivists and surgical case managers. This study aims to evaluate the feasibility of this new model of care, and to determine potential benefits to patients and clinicians. METHODS AND ANALYSIS: After being assessed for frailty, patients will complete a patient-clinician information engagement survey pretreatment and at 6 months follow-up. Patients (and/or family members) will be interviewed about their experience of care pretreatment and at 3 and 6 months follow-ups. Clinicians will complete a survey on workplace attitudes and engagement both preimplementation and postimplementation of PC-ACP and be interviewed, following each survey, on the implementation of PC-ACP. We will use process mapping to map the patient journey through the surgical care pathway to determine areas of improvement and to identify variations in patient experience. ETHICS AND DISSEMINATION: This study has received ethical approval from Townsville Hospital and Health Service HREC (HREC/16/QTHS/100). Results will be communicated to the participating hospital, presented at conferences and submitted for publication in a peer-reviewed MEDLINE-indexed journal.

Health system frameworks and performance indicators in eight countries: A comparative international analysis.

OBJECTIVES: Performance indicators are a popular mechanism for measuring the quality of healthcare to facilitate both quality improvement and systems management. Few studies make comparative assessments of different countries' performance indicator frameworks. This study identifies and compares frameworks and performance indicators used in selected Organisation for Economic Co-operation and Development health systems to measure and report on the performance of healthcare organisations and local health systems. Countries involved are Australia, Canada, Denmark, England, the Netherlands, New Zealand, Scotland and the United States. METHODS: Identification of comparable international indicators and analyses of their characteristics and of their broader national frameworks and contexts were undertaken. Two dimensions of indicators - that they are nationally consistent (used across the country rather than just regionally) and locally relevant (measured and reported publicly at a local level, for example, a health service) - were deemed important. RESULTS: The most commonly used domains in performance frameworks were safety, effectiveness and access. The search found 401 indicators that fulfilled the 'nationally consistent and locally relevant' criteria. Of these, 45 indicators are reported in more than one country. Cardiovascular, surgery and mental health were the most frequently reported disease groups. CONCLUSION: These comparative data inform researchers and policymakers internationally when designing health performance frameworks and indicator sets.

Macquarie Surgical Innovation Identification Tool (MSIIT): a study protocol for a usability and pilot test.

INTRODUCTION: Medicine relies on innovation to continually improve. However, innovation is potentially risky, and not all innovations are successful. Therefore, it is important to identify innovations prospectively and provide support, to make innovation as safe and effective as possible. The Macquarie Surgical Innovation Identification Tool (MSIIT) is a simple checklist designed as a practical tool for hospitals to identify planned surgical innovations. This project aims to test the usability and pilot the use of the MSIIT in a surgical setting. METHODS AND ANALYSIS: The project will run in two phases at two Australian hospitals, one public and one private. Phase I will involve interviews, focus groups and a survey of hospital administrators and surgical teams to assess the usability and system requirements for the use of the MSIIT. Current practice regarding surgical innovation within participating hospitals will be mapped, and the best implementation strategy for MSIIT completion will be established. Phase II will involve trialling the MSIIT for each surgery within the trial period by various surgical personnel. Follow-up interviews, focus groups and a survey will be conducted with trial participants to collect feedback on their experience of using the MSIIT during the trial period. Comparative data on rates of surgical innovation during the trial period will also be gathered from existing hospital systems and compared to the rates identified by the MSIIT. ETHICS AND DISSEMINATION: Ethical approval has been obtained. The results of this study will be presented to interested health services and other stakeholders, presented at conferences and published in a peer-reviewed MEDLINE-indexed journal.

The basis of clinical tribalism, hierarchy and stereotyping: a laboratory-controlled teamwork experiment.

OBJECTIVES: To examine the basis of multidisciplinary teamwork. In real-world healthcare settings, clinicians often cluster in profession-based tribal silos, form hierarchies and exhibit stereotypical behaviours. It is not clear whether these social structures are more a product of inherent characteristics of the individuals or groups comprising the professions, or attributable to a greater extent to workplace factors. SETTING: Controlled laboratory environment with well-appointed, quiet rooms and video and audio equipment. PARTICIPANTS: Clinical professionals (n=133) divided into 35 groups of doctors, nurses and allied health professions, or mixed professions. INTERVENTIONS: Participants engaged in one of three team tasks, and their performance was video-recorded and assessed. PRIMARY AND SECONDARY MEASURES: Primary: teamwork performance. Secondary, pre-experimental: a bank of personality questionnaires designed to assess participants' individual differences. Postexperimental: the 16-item Mayo High Performance Teamwork Scale (MHPTS) to measure teamwork skills; this was self-assessed by participants and also by external raters. In addition, external, arm's length blinded observations of the videotapes were conducted. RESULTS: At baseline, there were few significant differences between the professions in collective orientation, most of the personality factors, Machiavellianism and conservatism. Teams generally functioned well, with effective relationships, and exhibited little by way of discernible tribal or hierarchical behaviours, and no obvious differences between groups (F (3, 31)=0.94, p=0.43). CONCLUSIONS: Once clinicians are taken out of the workplace and put in controlled settings, tribalism, hierarchical and stereotype behaviours largely dissolve. It is unwise therefore to attribute these factors to fundamental sociological or psychological differences between individuals in the professions, or aggregated group differences. Workplace cultures are more likely to be influential in shaping such behaviours. The results underscore the importance of culture and context in improvement activities. Future initiatives should factor in culture and context as well as individuals' or professions' characteristics as the basis for inducing more lateral teamwork or better interprofessional collaboration.

On the fragility of medical virtue in a neoliberal context: the case of commercial conflicts of interest in reproductive medicine.

Social, political, and economic environments play an active role in nurturing professional virtue. Yet, these environments can also lead to the erosion of virtue. As such, professional virtue is fragile and vulnerable to environmental shifts. While physicians are often considered to be among the most virtuous of professional groups, concern has also always existed about the impact of commercial arrangements on physicians' willingness and capacity to enact their professional virtues. This article examines the ways in which commercial arrangements have been negotiated to secure medical virtue from real or perceived threats of erosion. In particular, we focus on the concern surrounding conflicts of interest arising from commercial arrangements that have developed as a result of neoliberal economic and social policies. The deregulation of medical markets and privatization of services have produced new commercial relationships that are often misunderstood by patients, publics, and physicians themselves. 'Conflicts of interest' policies have been introduced in an attempt to safeguard ethical conduct and medical practice. However, a number of virtue ethicists have critiqued these policies as inadequate for securing virtue. We examine the ways in which commercial arrangements have been seen to impact upon medical virtue, both historically and in the context of modern medicine (using the example of fertility services in Australia). We then describe and critique current efforts to restore clinical virtue through both conflict of interest policies and through virtue ethics. Finally, we suggest some possible ways of addressing the corrosive effects of neoliberalism on medical virtue.

Diverse roles for Wnt7a in ventral midbrain neurogenesis and dopaminergic axon morphogenesis.

During development of the central nervous system, trophic, together with genetic, cues dictate the balance between cellular proliferation and differentiation. Subsequent to the birth of new neurons, additional intrinsic and extrinsic signals regulate the connectivity of these cells. While a number of regulators of ventral midbrain (VM) neurogenesis and dopaminergic (DA) axon guidance are known, we identify a number of novel roles for the secreted glycoprotein, Wnt7a, in this context. We demonstrate a temporal and spatial expression of Wnt7a in the VM, indicative of roles in neurogenesis, differentiation, and axonal growth and guidance. In primary VM cultures, and validated in Wnt7a-deficient mice, we show that the early expression within the VM is important for regulating VM progenitor proliferation, cell cycle progression, and cell survival, thereby dictating the number of midbrain Nurr1 precursors and DA neurons. During early development of the midbrain DA pathways, Wnt7a promotes axonal elongation and repels DA neurites out of the midbrain. Later, Wnt7a expression in the VM midline suggests a role in preventing axonal crossing while expression in regions flanking the medial forebrain bundle (thalamus and hypothalamus) ensured appropriate trajectory of DA axons en route to their forebrain targets. We show that the effects of Wnt7a in VM development are mediated, at least in part, by the ß-catenin/canonical pathways. Together, these findings identify Wnt7a as a new regulator of VM neurogenesis and DA axon growth and guidance.

Ryk, a receptor regulating Wnt5a-mediated neurogenesis and axon morphogenesis of ventral midbrain dopaminergic neurons.

Ryk is an atypical transmembrane receptor tyrosine kinase that has been shown to play multiple roles in development through the modulation of Wnt signaling. Within the developing ventral midbrain (VM), Wnts have been shown to contribute to the proliferation, differentiation, and connectivity of dopamine (DA) neurons; however, the Wnt-related receptors regulating these events remain less well described. In light of the established roles of Wnt5a in dopaminergic development (regulating DA differentiation as well as axonal growth and repulsion), and its interaction with Ryk elsewhere within the central nervous system, we investigated the potential role of Ryk in VM development. Here we show temporal and spatial expression of Ryk within the VM, suggestive of a role in DA neurogenesis and axonal plasticity. In VM primary cultures, we show that the effects of Wnt5a on VM progenitor proliferation, DA differentiation, and DA axonal connectivity can be inhibited using an Ryk-blocking antibody. In support, Ryk knockout mice showed reduced VM progenitors and DA precursor populations, resulting in a significant decrease in DA cells. However, Ryk(-/-) mice displayed no defects in DA axonal growth, guidance, or fasciculation of the MFB, suggesting other receptors may be involved and/or compensate for the loss of this receptor. These findings identify for the first time Ryk as an important receptor for midbrain DA development.

Wnt5a regulates midbrain dopaminergic axon growth and guidance.

During development, precise temporal and spatial gradients are responsible for guiding axons to their appropriate targets. Within the developing ventral midbrain (VM) the cues that guide dopaminergic (DA) axons to their forebrain targets remain to be fully elucidated. Wnts are morphogens that have been identified as axon guidance molecules. Several Wnts are expressed in the VM where they regulate the birth of DA neurons. Here, we describe that a precise temporo-spatial expression of Wnt5a accompanies the development of nigrostriatal projections by VM DA neurons. In mice at E11.5, Wnt5a is expressed in the VM where it was found to promote DA neurite and axonal growth in VM primary cultures. By E14.5, when DA axons are approaching their striatal target, Wnt5a causes DA neurite retraction in primary cultures. Co-culture of VM explants with Wnt5a-overexpressing cell aggregates revealed that Wnt5a is capable of repelling DA neurites. Antagonism experiments revealed that the effects of Wnt5a are mediated by the Frizzled receptors and by the small GTPase, Rac1 (a component of the non-canonical Wnt planar cell polarity pathway). Moreover, the effects were specific as they could be blocked by Wnt5a antibody, sFRPs and RYK-Fc. The importance of Wnt5a in DA axon morphogenesis was further verified in Wnt5a-/- mice, where fasciculation of the medial forebrain bundle (MFB) as well as the density of DA neurites in the MFB and striatal terminals were disrupted. Thus, our results identify a novel role of Wnt5a in DA axon growth and guidance.