LMP student seminars: 11 March

Each week during term time, MSc and PhD candidates in the Department of Laboratory Medicine and Pathobiology present their research.

Anyone is welcome. No need to register.

Location: Medical Sciences Building, rooms 4171 or 4279, see below.

As part of the core research curriculum, students taking LMP1001/2/3: Graduate Seminars in Laboratory Medicine and Pathobiology will present their projects. Please see abstracts below.

Group 3: Cardiovascular, Physiology and Metabolism

Location: MSB 4171

Annie Yew

• Title: Repurposing Homoharringtonine As A Novel Therapy For Muscle Wasting
• Supervisor: Dr. Hoon-Ki Sung

Jeff Zhang

• Title: Long-Term Safety and Anti-Arrhythmic Efficacy of Gel-PDA in a Murine Model of Atrial Fibrillation
• Supervisor: Dr. Ren-Ke Li

Group 5: Infectious Diseases, Inflammation and Immunology

Location: MSB 4279

Chuhan Dong

• Title: Antibody Isotype Matters: Murine IgG1 drives rapid antigen loss and RBC clearance via trogocytosis, independent of phagocytosis and complement in mice
• Supervisor: Dr. Alan Lazarus

Essam Karam

• Title: Enteric Adenovirus Evades STING-Mediated Interferon Signalling in the Human Intestinal Epithelium

• Supervisor: Dr. Stephen Girardin

Abstracts

Annie Yew: Repurposing Homoharringtonine As A Novel Therapy For Muscle Wasting

Skeletal muscle plays a pivotal role in various physiological functions, including voluntary movement, heat production, and regulation of glucose metabolism. Consequently, dysfunction of the skeletal muscle system is strongly associated with many pathological conditions, including type 2 diabetes mellitus and various degenerative diseases. These examples highlight the critical need for the development of novel therapeutic strategies to combat muscle wasting. In a previous study, we identified homoharringtonine (HHT), an FDA approved anti-leukemic drug, as a senolytic (selectively eliminates senescent cells) agent, which prolonged longevity and unexpectedly improved skeletal muscle function, suggesting a previously unrecognized role of HHT in regulating skeletal muscle health. In this project, muscle wasting mouse models were treated with HHT to investigate it’s on muscle function and its corresponding histological changes. HHT treatment was previously shown to improve muscle mass and function in a diet induced obesity model. Further histological analyses revealed this may result from a global shift towards larger sized myocytes, likely mediated through enhanced regenerative capacity. HHT was further explored in the D2.mdx model, which experiences severe skeletal and cardiac muscle degeneration. HHT-treated mice displayed functional improvements compared to their control counterparts with a reduction in degeneration and regeneration pathways. This suggests HHT treatment may mitigate myocyte degeneration and its subsequent need for regeneration, which is normally high in dystrophic mice. Together, this data suggests HHT treatment may improve skeletal muscle health and open new therapeutic avenues for the treatment of muscle wasting conditions.

Jeff Zhang: Long-Term Safety and Anti-Arrhythmic Efficacy of Gel-PDA in a Murine Model of Atrial Fibrillation

Conductive biomaterials have emerged as a promising therapeutic strategy for atrial fibrillation (AF). Our lab has identified a gelatin-based polydopamine (Gel-PDA) that confers structural and functional benefits in AF treatment. While short-term studies have demonstrated high efficacy, the lack of long-term data remains a barrier to clinical translation. This study addresses these gaps by evaluating the 6-month toxicity, functional outcomes, and implant stability of Gel-PDA.

KCNE1 knockout mice, reported to exhibit spontaneous AF, received atrial surface implantation of either Gel-PDA or a gelatin control. Preliminary analyses revealed no significant differences in systemic, cardiac structural, or electrophysiological markers between groups, except for body weight. Despite initial expectations for the disease model, spontaneous AF incidence was low; however, terminal programmed electrical stimulation (PES) successfully induced AF. The Gel-PDA group exhibited an AF incidence rate of 8%, compared to 70% in the gelatin control group, reflecting a statistically significant reduction in AF susceptibility (p = 0.0014). Additionally, overall AF burden, defined as the average duration of AF across all PES induction attempts, was significantly lower in the Gel-PDA group (0.1340 ± 0.1835 s) compared to the gelatin group (13.95 ± 18.55 s; p = 0.0159).

At the 6-month endpoint, Gel-PDA demonstrated sustained material stability, with 67.12% ± 4.46% of implant mass remaining, whereas gelatin was no longer detectable. Histological staining demonstrated no evidence of systemic morphological changes or cardiac structural remodelling. Overall, preliminary findings demonstrate no overt toxicity associated with long-term Gel-PDA implantation, as well as sustained therapeutic efficacy at 6 months post-implantation.\

Chuhan Dong: Antibody Isotype Matters: Murine IgG1 drives rapid antigen loss and RBC clearance via trogocytosis, independent of phagocytosis and complement in mice

Background: Antibodies targeting red blood cell (RBC) antigens have been classically associated with clearance through phagocytosis and/or complement in alloimmune and autoimmune contexts. Murine isotype IgG2a has been considered the most potent for RBC clearance due to its high affinity for multiple activating Fcγ receptors to promote phagocytosis and its ability to activate complement. However, some anti-RBC antibodies can mediate clearance independent of both phagocytosis and complement, the process and isotype-specific impacts underlying these non-classical pathways are incompletely understood.

Study design and methods: Using HOD transgenic mice where RBCs expresses a single recombinant antigen of Hen-egg-lysozyme, OVA sequences and human Duffy transmembrane protein, we evaluated three non-phagocytosis-inducing monoclonal anti-RBC antibodies targeting the Duffy portion of the HOD RBCs. Antigen loss and anemia were assessed by flow cytometry. Although prior studies showed no complement involvement in HOD mice, we assessed C3 deposition to confirm its absence under our conditions.

Results: Antigen loss through trogocytosis (partial uptake of RBC membrane by immune cells) mediated anemia in HOD mice. IgG1 induced faster antigen loss and greater anemia than IgG2a despite identical variable region sequences and IgG1 was effective at doses five‑fold lower than IgG2a, highlighting superior potency. No C3 deposition was detected, confirming complement independence.

Conclusion: We demonstrate trogocytosis as a potent, phagocytosis- and complement‑independent pathway for RBC clearance and anemia. The finding that murine IgG1 outperforms IgG2a under conditions where trogocytosis predominates expands our understanding of antibody‑induced RBC clearance and highlights implications for diseases like autoimmune hemolytic anemia, where non‑classical pathways may influence diagnosis and disease severity.

Essam Karam: Enteric Adenovirus Evades STING-Mediated Interferon Signalling in the Human Intestinal Epithelium

Stimulator of interferon genes (STING) is an intracellular immune sensor that plays a critical role in host defence against viral infection. STING is activated by cyclic dinucleotides generated by cyclic GMP-AMP synthase (cGAS) in response to cytosolic double-stranded DNA, leading to induction of interferons. Human adenoviruses are non-enveloped dsDNA viruses classified into seven species. Species F includes adenovirus type 40 (Ad40) and type 41 (Ad41), enteric pathogens that infect the intestinal epithelium and are a leading cause of infantile gastroenteritis. Although adenovirus infection disrupts intestinal homeostasis, the relationship between enteric adenovirus infection and STING activation in intestinal epithelial cells remains poorly characterized. Notably, direct activation of STING by enteric adenoviruses has not been demonstrated.

This project investigates the epithelial response to enteric adenovirus infection and defines the role of cGAS-STING signaling in host defense. I hypothesize that epithelial intrinsic STING signaling is protective, and that its dysregulation increases susceptibility to infection. Using patient-derived ileal and duodenal organoids, I infected human duodenal organoids with Ad41 and assessed host responses by western blot, RT-qPCR, and confocal microscopy.

Duodenal organoids exhibited a functional cGAS-STING pathway, confirmed by activation with the STING agonist diABZI. Ad41 infection induced STING phosphorylation but failed to trigger an interferon response despite robust viral transcript expression. These findings suggest that Ad41 evades STING-mediated antiviral signaling, enabling replication within the intestinal epithelium.

Contact

No need to register.

Contact lmp.grad@utoronto.ca with any questions.