Heart Failure Impairs Bone Marrow Hematopoietic Stem Cell Function and Responses to Injury.

Background Heart failure (HF) is a clinical syndrome associated with a progressive decline in myocardial function and low-grade systemic inflammation. Chronic inflammation can have lasting effects on the bone marrow (BM) stem cell pool by impacting cell renewal and lineage differentiation. However, how HF affects BM stem/progenitor cells remains largely unexplored. Methods and Results EGFP+ (Enchanced green fluorescent protein) mice were subjected to coronary artery ligation, and BM was collected 8 weeks after myocardial infarction. Transplantation of EGFP+ BM into wild-type mice revealed reduced reconstitution potential of BM from mice subjected to myocardial infarction versus BM from sham mice. To study the effects HF has on human BM function, 71 patients, HF (n=20) and controls (n=51), who were scheduled for elective cardiac surgery were consented and enrolled in this study. Patients with HF exhibited more circulating blood myeloid cells, and analysis of patient BM revealed significant differences in cell composition and colony formation potential. Human CD34+ cell reconstitution potential was also assessed using the NOD-SCID-IL2rγnull mouse xenotransplant model. NOD-SCID-IL2rγnull mice reconstituted with BM from patients with HF had significantly fewer engrafted human CD34+ cells as well as reduced lymphoid cell production. Analysis of tissue repair responses using permanent left anteriordescending coronary artery ligation demonstrated reduced survival of HF-BM reconstituted mice as well as significant differences in human (donor) and mouse (host) cellular responses after MI. Conclusions HF alters the BM composition, adversely affects cell reconstitution potential, and alters cellular responses to injury. Further studies are needed to determine whether restoring BM function can impact disease progression or improve cellular responses to injury.

Aging impairs human bone marrow function and cardiac repair following myocardial infarction in a humanized chimeric mouse.

Ventricular remodeling following myocardial infarction (MI) is a major cause of heart failure, a condition prevalent in older individuals. Following MI, immune cells are mobilized to the myocardium from peripheral lymphoid organs and play an active role in orchestrating repair. While the effect of aging on mouse bone marrow (BM) has been studied, less is known about how aging affects human BM cells and their ability to regulate repair processes. In this study, we investigate the effect aging has on human BM cell responses post-MI using a humanized chimeric mouse model. BM samples were collected from middle aged (mean age 56.4 ± 0.97) and old (mean age 72.7 ± 0.59) patients undergoing cardiac surgery, CD34+/- cells were isolated, and NOD-scid-IL2rγnull (NSG) mice were reconstituted. Three months following reconstitution, the animals were examined at baseline or subjected to coronary artery ligation (MI). Younger patient cells exhibited greater repopulation capacity in the BM, blood, and spleen as well as greater lymphoid cell production. Following MI, CD34+ cell age impacted donor and host cellular responses. Mice reconstituted with younger CD34+ cells exhibited greater human CD45+ recruitment to the heart compared to mice reconstituted with old cells. Increased cellular responses were primarily driven by T-cell recruitment, and these changes corresponded with greater human IFNy levels and reduced mouse IL-1ß in the heart. Age-dependent changes in BM function led to significantly lower survival, increased infarct expansion, impaired host cell responses, and reduced function by 4w post-MI. In contrast, younger CD34+ cells helped to limit remodeling and preserve function post-MI.

International training considerations of Canadian Clinician-Scientist Trainees - A national survey.

PURPOSE: Canadian clinician-scientist trainees enrolled in dual degree programs often pursue an extended training route following completion of MD and MSc or PhD degrees. However, the proportion, plans and reasoning of trainees who intend to pursue training internationally following dual degree completion has not been investigated. In this study, we assessed the international training considerations of current clinician-scientist trainees. METHODS: We designed an 11-question survey, which was sent out by program directors to all current MDPhD program and Clinician Investigator Program (CIP) trainees. Responses were collected from July 8, 2019 to August 8, 2019. RESULTS: We received a total of 191 responses, with representation from every Canadian medical school and both MD-PhD program and CIP trainees. The majority of trainees are considering completing additional training outside Canada, most commonly post-doctoral and/or clinical fellowships. The most common reasons for considering international training include those related to quality and prestige of training programs. In contrast, the most common reasons for considering staying in Canada for additional training are related to personal and ethical reasons. Irrespective of intentions to pursue international training, the majority of trainees ultimately intend to establish a career in Canada. CONCLUSION: While most trainees are considering additional training outside of Canada due to prestige and quality of training, the majority of trainees intend to pursue a career as a clinician-scientist back in Canada. Trainees would likely benefit from improved guidance and mentorship on the value of international training, as well as enhanced support in facilitating cross-border mobility.

Overview of the Canadian Clinician Investigator Trainees' research presented at the 2019 CSCI-CITAC Joint Meeting.

The 2019 Annual General Meeting and Young Investigators' Forum of the Canadian Society for Clinical Investigation / Société Canadienne de Recherche Clinique (CSCI/SCRC) and Clinician Investigator Trainee Association of Canada / Association des Cliniciens-Chercheurs en Formation du Canada (CITAC/ACCFC) was held in Banff, Alberta on November 8-10th, 2019. The theme was "Positioning Early Career Investigators for Success: Strategy and Resilience". Lectures and workshops provided knowledge and tools to facilitate the attendees' development as clinician investigators. Dr. Jason Berman (President of CSCI/SCRC), Elina Cook (President of CITAC/ACCFC) and Drs. Doreen Rabi and Zelma Kiss (University of Calgary Organizing Co-Chairs) gave opening presentations. The keynote speakers were Dr. William Foulkes (McGill University) (Distinguished Scientist Award winner) and Dr. Andrés Finzi (Université de Montréal) (Joe Doupe Young Investigator Award winner). Dr. Robert Bortolussi (Dalhousie University) received the Distinguished Service Award for his work as the Editor-in-Chief of Clinical and Investigative Medicine and for being instrumental in the development of the Canadian Child Health Clinician Scientist Program. This meeting was the first to host a panel discussion with Drs. Stephen Robbins and Marcello Tonelli from the Canadian Institutes of Health Research. Workshops on communication, career planning and work-life balance were hosted by André Picard and Drs. Todd Anderson, Karen Tang, William Ghali, May Lynn Quan, Alicia Polachek and Shannon Ruzycki. The AGM showcased 90 presentations from clinician investigator trainees from across Canada. Most of the abstracts are summarized in this review. Eight outstanding abstracts were selected for oral presentation at the President's Forum.

Newsletter Fall 2020: Clinician Investigator Trainee Association of Canada (CITAC).

Message from the CITAC president To say that 2020 has been an unprecedented year is an understatement. The coronavirus disease 2019 (COVID-19) global pandemic and the major societal awakening on racial equity and justice have led us to reflect on our direction, goals and mission. Thanks to our talented and dedicated executive team, we were able to pivot our efforts and adapt to the changing landscape of research and advocacy. In April, we provided our members with a list of resources to help facilitate a smooth transition to working from home. In June, we published Clinician Investigator Trainee Association of Canada's (CITAC) press release on our role in combating anti-Black discrimination and racial injustice and have outlined specific advocacy efforts that we will be committing to over the next years (the full statement can be found on our website, https://www.citac-accfc.org).

Newsletter Spring 2020: Clinician Investigator Trainee Association of Canada (CITAC).

Message from Tina Marvasti, President of the Clinician Investigator Trainee Association of Canada: National and international collaborations and evidence based advocacy for the Canadian MD/PhD and MD+ trainees The overarching goals of the Clinician Investigator Trainee Association of Canada (CITAC) for 2020 are to expand its reach to increase membership and to continue to build strong relationships with our national and international partners. These goals will be achieved by applying the following three strategies: • Continue to develop and strengthen our relationships with national and international key partners and with stake holders • Better understand the needs of clinician-scientist trainees for evidence-based advocacy • Increase membership, improve communication with all members and highlight the accomplishments of trainees.

Piloting a long distance clinician scientist trainee mentorship match in Canada.

Clinician scientists are physicians who are uniquely trained to bridge the gap between scientific discovery and clinical practice. However, the challenges of integrating research and medicine are often not directly addressed in the clinician scientist training programs. Furthermore, the demanding training path is financially and personally daunting. Previous studies have shown that MD/PhD trainees value the advice and expertise of senior mentors in navigating their academic career path. Despite this demand for mentors, there is a lack of formal mentorship initiatives at the institutional level across Canada. Recently, MD/PhD trainees have attempted to address this issue by implementing a nationwide mentorship match, with the aim of making mentorship more accessible to trainees across Canada.

Rectification of radiotherapy-induced cognitive impairments in aged mice by reconstituted Sca-1+ stem cells from young donors.

BACKGROUND: Radiotherapy is widely used and effective for treating brain tumours, but inevitably impairs cognition as it arrests cellular processes important for learning and memory. This is particularly evident in the aged brain with limited regenerative capacity, where radiation produces irreparable neuronal damage and activation of neighbouring microglia. The latter is responsible for increased neuronal death and contributes to cognitive decline after treatment. To date, there are few effective means to prevent cognitive deficits after radiotherapy. METHODS: Here we implanted hematopoietic stem cells (HSCs) from young or old (2- or 18-month-old, respectively) donor mice expressing green fluorescent protein (GFP) into old recipients and assessed cognitive abilities 3 months post-reconstitution. RESULTS: Regardless of donor age, GFP+ cells homed to the brain of old recipients and expressed the macrophage/microglial marker, Iba1. However, only young cells attenuated deficits in novel object recognition and spatial memory and learning in old mice post-irradiation. Mechanistically, old recipients that received young HSCs, but not old, displayed significantly greater dendritic spine density and long-term potentiation (LTP) in CA1 neurons of the hippocampus. Lastly, we found that GFP+/Iba1+ cells from young and old donors were differentially polarized to an anti- and pro-inflammatory phenotype and produced neuroprotective factors and reactive nitrogen species in vivo, respectively. CONCLUSION: Our results suggest aged peripherally derived microglia-like cells may exacerbate cognitive impairments after radiotherapy, whereas young microglia-like cells are polarized to a reparative phenotype in the irradiated brain, particularly in neural circuits associated with rewards, learning, and memory. These findings present a proof-of-principle for effectively reinstating central cognitive function of irradiated brains with peripheral stem cells from young donor bone marrow.

Scientific overview on CSCI-CITAC Annual General Meeting and 2017 Young Investigators' Forum.

The 2017 Annual General Meeting of the Canadian Society of Clinician Investigators (CSCI) and Clinician Investigator Trainee Association of Canada/Association des Cliniciens-Chercheurs en Formation du Canada (CITAC/ACCFC) was a national Annual General Meeting (AGM) held in Toronto, Ontario November 20-22, 2017, in conjunction with the University of Toronto Clinician Investigator Program Research Day. The theme for this year's meeting was "Roll up your sleeves-How to manage your physician scientist career", emphasizing lectures and workshops that were designed to provide tools for being proactive and successful in career planning. The keynote speakers were Dr. Rod McInnes (McGill University and Canadian Institutes of Health Research Acting President), who was the Distinguished Scientist Award recipient, Dr. David Goltzman (McGill University), who was the 2017 Henry Friesen Award recipient, Dr. Gillian Hawker (University of Toronto), Dr. Mike Sapieha (Université de Montréal), who was the 2017 Joe Doupe Award recipient, and Dr. Alex MacKenzie (Children's Hospital of Eastern Ontario Research Institute, University of Ottawa). The workshops, focusing on career development for clinician scientists, were hosted by Dr. Lisa Robinson, Dr. Nicola Jones, Kevin Vuong, Fran Brunelle, Dr. Jason Berman and Dr. Alan Underhill. Further to this, the Young Investigators' Forum encompasses presentations from scientist-clinician trainees from across the country. All scientific abstracts are summarized in this review. There were over 100 abstracts showcased at this year's meeting during the highlighted poster sessions, with six outstanding abstracts selected for oral presentations during the President's Forum.

Scientific Overview on CSCI-CITAC Annual General Meeting and 2016 Young Investigators' Forum.

The 2016 Annual General Meeting of the Canadian Society of Clinician Investigators (CSCI) and Clinician Investigator Trainee Association of Canada/Association des Cliniciens-Chercheurs en Formation du Canada (CITAC/ACCFC) was a national conference held in Toronto November 21-23, 2016, in conjunction with The University of Toronto Clinician Investigator Program Research Day. The theme for this year's meeting was "Mapping Your Career as a Clinician-Scientist"; emphasizing essential skills for developing a fruitful career as clinician-scientist. The meeting featured an opening presentation by Dr. Alan Underhill, Dr. Nicola Jones and Alexandra Kuzyk. The keynote speakers were Dr. Nada Jabado (McGill University), who discussed the association between cancer and histones, Dr. Norman Rosenblum (University of Toronto), who addressed the career path and the "calling" of the Clinician Scientist, Dr. Martin Schmeing (McGill University), who was the 2016 Joe Doupe Award recipient, and Dr. Linda Rabeneck (Cancer Care Ontario and University of Toronto), who received the Friends of CIHR lectureship. The workshops, focusing on career development for clinician scientists, were hosted by Drs. Alan Underhill, Nicola Jones, Lynn Raymond, Michael Schlossmacher and Norman Rosenblum, as well as University of Toronto communication specialists, Caitlin Johannesson and Suzanne Gold. In addition, the Young Investigators' Forum included presentations from clinician investigator trainees from across the country. The research topics were diverse and comprehensive: from basic sciences to clinical practice; from epidemiology to medical engineering. All scientific abstracts are summarized in this review. Over 70 abstracts were showcased at this year's meeting during two poster sessions, with six outstanding abstracts selected for oral presentations during the President's Forum.