LMP student seminars: 3 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
Xinyin Wang
- Title: Expression and localization of sperm fusion factors and its role in infertility
- Supervisor: Dr Jeff Lee
Angela Zhou
- Title: Advancing microvessel-based strategies for cell replacement therapy
- Supervisor: Dr. Sara Vasconcelos
Location: MSB 4279
Seyedeh Sara Fooladi
- Title: Harnessing the Potential of Mammalian Retinal Müller glia to Regenerate Cone Photoreceptors
- Supervisor: Dr. Rod Bremner
Dachuan (Dustin) Zhang
- Title: The Role of Apolipoprotein A-IV in Blood Transfusion
- Supervisor: Dr. Heyu Ni
Abstracts
Xinyin Wang: Expression and localization of sperm fusion factors and its role in infertility
Infertility affects 1 in 6 Canadians, with this rate doubling since the 1980’s. In one-third of cases, the underlying cause is unknown or termed ‘unexplained infertility’. The etiology and pathobiology of fertilization failure remain poorly defined. At the molecular level, fertilization requires the sperm to undergo the acrosome reaction, penetrate the zona pellucida, and fuse with the egg. This process is critically dependent on two fusion factors: IZUMO1 on the sperm and its receptor, JUNO, on the egg. Additionally, IZUMO1 must re-localize to the sperm's equatorial segment for surface expression and binding to JUNO. Beyond IZUMO1, other sperm fusion factors, such as DCST1 and TMEM81, have been identified as indispensable for fertilization, though their roles during sperm-egg fusion remain unclear. We hypothesize these factors also undergo re-localization after acrosome reaction. Moreover, due to the critical nature of these fusion factors, we believe defects in their expression, localization, or binding may contribute to clinical cases of subfertility.
Sperm from 40 patients undergoing IVF (11 total fertilization failure (TFF)/low fertilization and 29 normal fertilization) were assessed using imaging flow cytometry to evaluate the expression and localization of DCST1, TMEM81, and IZUMO1, as well as IZUMO1-JUNO binding.
DCST1 and TMEM81 were expressed on the equatorial segment of acrosome reacted sperm but absent on acrosome intact sperm. Additionally, no significant differences were observed for the localization and expression of IZUMO1 and DCST1 and no significant differences were observed for IZUMO1-JUNO binding between the two groups. However, the TFF/low fertilization group exhibited lower levels of acrosome reaction compared to controls.
Our findings suggest that acrosome reaction, which regulates the re-localization of IZUMO1, DCST1, and TMEM81, is correlated with fertilization rate. Reduced acrosome-reacted sperm may contribute to infertility by limiting the number of fusion-competent sperm available for egg penetration and fertilization. A larger cohort is needed to validate these findings, and we aim to expand our study to 50 patients per group.
Angela Zhou: Advancing microvessel-based strategies for cell replacement therapy
Human pluripotent stem cells or embryonic stem cells have emerged as a powerful tool in regenerative medicine for replacing damaged or diseased tissues. Despite these advances, tissue vascularization remains a bottleneck for the clinical translation of cell replacement therapies as a lack of appropriate vascularization hinders tissue survival and therefore engraftment and function.
The Vasconcelos lab has developed a unique method to preform a microvasculature that is based on adipose-derived, microvascular fragments. These microvascular fragments can be obtained by digestion of adipose tissue and most importantly, they can progress into mature, perfusion networks in vivo.
My PhD aims to understand and elucidate the dynamic processes and cues microvascular fragments progress through to form mature vascular networks in vivo. Through intravital imaging I will elucidate key cell types, cues, and processes that are necessary for successful vascular regeneration. Understanding key drivers of maturation in implanted MVs is paramount to the development of effective neovascularization therapies.
Seyedeh Sara Fooladi: Harnessing the Potential of Mammalian Retinal Müller glia to Regenerate Cone Photoreceptors
Cone photoreceptors are responsible for visual acuity and colour vision. Their loss leads to blindness in various diseases including retinitis pigmentosa (RP). Zebrafish can regenerate their entire retina upon injury. This phenomenon happens through the dedifferentiation of Muller glia (MG) into a progenitor-like state, followed by division and subsequent differentiation, replacing the damaged cells. Mammalian MG have lost this regenerative ability and, despite extensive work, no study has ever reported their successful differentiation into mature cones. This project aims to harness the potential of mammalian retinal MG to regenerate cone photoreceptors.
MYCN is an oncoprotein best known for its ability to promote division. This protein is expressed in post-mitotic human cone precursors but is down-regulated in adult cones. The function of MYCN in cone precursors is still unknown. We wondered whether it may influence cone fate. In unpublished work, we discovered that overexpression of MYCN induces cone precursors in postnatal murine retinal progenitors. Indeed, scRNAseq analysis confirms that MYCN biases murine post-natal progenitors towards this lineage. Since the transcriptome of progenitors and MG is similar, a similar response can be anticipated in MG. (Blackshaw, 2004) Therefore, we hypothesize that the transient expression of MYCN can initially facilitate MG differentiation into cone precursors, facilitating their subsequent maturation into cones.
To investigate the effects of MYCN overexpression in inducing cone lineage we use GlastCreER; Sun1-GFP mice where Tamoxifen administration leads to activation of Cre in MG. At birth, these mice are electroporated with a Cre-dependent plasmid containing MYCN. In MG, activated Cre removes the stop cassette, inducing permanent expression of MYCN from the electroporated plasmid and a green-fluorescent reporter from the Sun1-GFP transgene in the mice.
Early results from collaboration with the Cayouette lab (IRCM, Montreal), suggest that MYCN can reprogram adult MG towards the cone lineage. I will present our results tracking the effect of MYCN expression in post-natal murine retinal progenitors and adult MG on lineage transformation.
Dachuan (Dustin) Zhang: The Role of Apolipoprotein A-IV in Blood Transfusion
Platelets are small anucleate blood cells that play a key role in hemostasis. Platelet transfusion is a lifesaving procedure to stop bleeding, and approximately 115,000 platelet units are manufactured every year in Canada. Platelets are also part of innate immunity and can be actively involved in inflammation and immune responses.
The β3 integrin (e.g. GPIIbIIIa), a major platelet surface protein, mediates platelet adhesion to injured vessel walls, and bridges adjacent platelets for aggregation through binding to fibrinogen (Fg) or other ligands. Notably, Fg-β3 binding can deliver outside-in signaling, which drives platelet activation, de novo synthesis of P-selectin and other granule component releasates. P-selectin is a key mediator of inflammation, leukocyte rolling, and T helper 1 (Th1) cell immune response. As platelet P-selectin mediates platelet-leukocyte interactions, Fg-β3 binding is therefore important not only for hemostasis, but also likely for inflammation and immune response. Apolipoprotein A-IV (apoA-IV) is a lipid binding protein that is mainly synthesized in the small intestine during lipid absorption.
We previously discovered that apoA-IV is a competitive inhibitory ligand of platelet αIIbβ3 integrin (GPIIbIIIa) and decreased platelet adhesion and aggregation. The anti-inflammatory activity of apoA-IV has also been observed for suppressing P-selectin expression and platelet-leukocyte adhesion in a mouse colitis model and dampening effector cell functions in eosinophil for allergic inflammation. Although abundant in blood plasma (150–370 µg/mL), whether apoA-IV in blood products (e.g. whole blood, platelets, plasma) can attenuate inflammation and immune response, enabling successful blood transfusions, has not been explored.
To test this hypothesis, apoA-IV deficient (apoA-IV-/-) mice and WT (apoA-IV+/+) C57BL/6 mice littermates were transfused with BALB/c murine platelets (mPLT), human platelets (hPLT), human red blood cells (hRBC), and sheep red blood cells (sRBC) via tail vein. Serum antibody titers, T cell populations in blood, and serum cytokine profile were tested in flow cytometry and cytokine dot blot assays.
We found that apoA-IV-/- mice generated higher antibody levels than WT littermates after transfusions of BALB/c mPLT, hPLT, hRBC, and sRBC. Furthermore, apoA-IV-/- mouse generated higher serum cytokine levels after hRBC transfusion than WT littermate, especially pro-inflammatory cytokines stromal cell-derived factor 1 (SDF-1) and tissue inhibitors of metalloproteinases 1 (TIMP-1). After sRBC transfusion, apoA-IV-/- mice also had increased CD4+ T cell population and decreased CD4+FOXP3+ regulatory T cell population in peripheral blood than WT littermates.
These data demonstrated that apoA-IV exhibited immune suppressive functions following blood transfusion, providing insights into the protective role of apoA-IV to attenuate transfusion-mediated adverse inflammation and immune responses.
Contact
No need to register.
Contact lmp.grad@utoronto.ca with any questions