Browsing by Author "Rancourt, Derrick Emile"

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    The Effect of The Notch Signalling Pathway Inhibition on The Osteogenic Differentiation of Pluripotent Stem Cells
    (2022-04) Helmi, Summer Ahmed Mahmoud; Rancourt, Derrick Emile; Jamniczky, Heather; Kurrasch, Deborah; Wang, Lisheng; Cobb, John
    Critical size bone defects are a common problem in orthopedics; a critical-size bone defect is a defect larger than 1.5 times the diameter of the injured bone. The most common causes of critical size bone defects are trauma, tumor excision, and infection. The treatment options for critical-size bone defects are very challenging, primarily with underlying chronic conditions like osteoporosis and diabetes. Bone is a dynamic and highly specialized connective tissue due to its unique regeneration capability. However, if the bone defect is large, it would require grafting to heal properly as this defect will not heal by itself if left untreated. Induced Pluripotent stem cell-based cell therapies for bone regeneration involve reprogramming a patient’s cells into iPSC and re-directing them to differentiate into the osteoblast lineage, then culturing them onto a scaffolding system that provides structural and functional support to the differentiated cells. Appropriate scaffolds and the careful use of bioactive molecules to enhance the differentiation outcome are vital components for successful iPSC-based tissue engineering. These combinations considerably impact bone cell-material interactions that guide bone regeneration and improve bone healing and regeneration processes. The Notch signalling pathway is highly conserved in cell fate determination throughout the animal kingdom and plays a role in the terminal differentiation in various tissues. The Notch signalling pathway was proven to enhance self-renewal and inhibit differentiation of bone progenitors. In the first part of this thesis, we explored the effect of inhibiting the Notch signalling pathway on mouse pluripotent stem cells. The results showed that inhibiting the Notch signalling pathway enhanced the differentiation of mouse pluripotent stem cells to osteoblasts. Moving forward, in the second part of the thesis, we explored if inhibiting the Notch signalling pathway in human pluripotent stem cells will have a similar advancement in the differentiation to bone cells. The results showed significant improvement in the osteogenic differentiation outcome compared to control cultures. In the third part, we tested the effect of Notch inhibition on the osteogenic differentiation of human induced pluripotent stem cells in vivo in an ectopic bone formation model. Collagen scaffolds mixed with DAPT Notch inhibitor guided and enhanced the osteogenic differentiation of human iPSC to tumor-free bone tissue. This approach can significantly accelerate the bone generation and healing of critical-size bone defects in normal patients and patients with underlying debilitating conditions.
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    Going (Reo)viral: factors promoting successful revival oncolytics infection
    (MDPI, 2018-08-11) Bourhill, Tarryn; Mori, Yoshinori; Rancourt, Derrick Emile; Shmulevitz, Maya; Johnston, Randal N.
    Oncolytic viruses show intriguing potential as cancer therapeutic agents. These viruses are capable of selectively targeting and killing cancerous cells while leaving healthy cells largely unaffected. The use of oncolytic viruses for cancer treatments in selected circumstances has recently been approved by the Food and Drug Administration (FDA) of the US and work is progressing on engineering viral vectors for enhanced selectivity, efficacy and safety. However, a better fundamental understanding of tumour and viral biology is essential for the continued advancement of the oncolytic field. This knowledge will not only help to engineer more potent and effective viruses but may also contribute to the identification of biomarkers that can determine which patients will benefit most from this treatment. A mechanistic understanding of the overlapping activity of viral and standard chemotherapeutics will enable the development of better combinational approaches to improve patient outcomes. In this review, we will examine each of the factors that contribute to productive viral infections in cancerous cells versus healthy cells. Special attention will be paid to reovirus as it is a well-studied virus and the only wild-type virus to have received orphan drug designation by the FDA. Although considerable insight into reoviral biology exists, there remain numerous deficiencies in our understanding of the factors regulating its successful oncolytic infection. Here we will discuss what is known to regulate infection as well as speculate about potential new mechanisms that may enhance successful replication. A joint appreciation of both tumour and viral biology will drive innovation for the next generation of reoviral mediated oncolytic therapy.
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    Mechanopluripotency – Adherens Junction Mechanotransduction Supports mESC Pluripotency Gene Expression via β-catenin Nuclear Translocation in Response to Fluid Shear Stress
    (2023-11-07) Harper, Lane Ward; Rancourt, Derrick Emile; Moorhead, Gregory B.; Sen, Arindom
    Pluripotent stem cells are increasingly being investigated as a base platform from which effector cells can be differentiated and utilized in various contexts as whole-cell therapeutics. Current culture methodologies require 2D plate culture and this represents a bottleneck in the form of increased costs associated with consumable usage and difficulties with standardization in manipulation. These difficulties cascade into ballooning therapy costs and troubles with cGMP compliance required for all biopharmaceutical manufacturing. To this end, there has been interest in culturing pluripotent stem cells in bioreactors, shown in previous therapeutic biopharmaceutical platforms to achieve cost-effective scale and compliance. In our bioreactor work, we have observed an increase in core pluripotency gene expression in mouse embryonic stem cells (mESCs) cultured as aggregates at specific impeller speeds in stirred tank bioreactors. We have termed this phenomenon “mechanopluripotency”. This project aimed to investigate the mechanism(s) responsible for our observation of induced pluripotency in the bioreactor. Using mutant cell lines containing a β-catenin reporter system, we show in both the bioreactor and a defined model system that in response to shear stress of ~6 dyne/cm2 β-catenin translocates to the nucleus where it is responsible for co-activation of the Wnt signaling pathway, known to affect pluripotency gene expression. Additionally, we show evidence that this response is mediated via altered molecular dynamics at the adherens junction, a key hub for cell-cell connections. By knocking out the cytoskeleton protein vinculin we show that β-catenin signaling is impaired in both the bioreactor and defined model system and a decrease in core pluripotency gene expression in the absence of exogenous maintenance factors. These results indicate that mechanopluripotency is mediated primarily through β-catenin and by impairing the adherens junction’s ability to adapt to mechanical force the response is attenuated.