Photo G Luo

Defended by Guotian LUO on 24-09-2021

Thesis director: Hervé PETITE


Mesenchymal stem cells (MSCs), also known as multipotent stromal cells, are promising candidates for tissue engineering applications. However, mounting evidence indicates that their therapeutic efficacy has fallen short of their initial promise and hype due to observed poor MSC survival and engraftment post-implantation. The hostile ischemic microenvironment, primarily characterized by oxygen and nutrient deprivation, is responsible for the rapid and massive death of MSCs post-implantation. Previously published research from the B3OA lab established that the absence of glucose (but not oxygen) is responsible for MSC death. The central hypothesis of this thesis is that glucose metabolism, a critical regulator of stem cell activity, enables MSCs to improve their survival and functional properties after transplantation, thereby increasing their therapeutic efficacy.
As a first step toward engineering a glucose-supplying construct, we propose investigating whether and how glucose affects the MSCs-mediated angiogenesis and then to developing an enzyme-controlled, nutritive hydrogel with an inbuilt system of glucose delivery to enhance MSC survival and functionalities post-implantation.

To accomplish our first objective, we discovered that supernatant conditioned media (CM) derived from human MSCs (hMSCs) cultured in the presence of glucose under near anoxia (0.1% O2) exhibited significantly greater angiogenic potential than CM derived from hMSCs cultured in the absence of glucose. Additionally, compared to hMSCs cultured in the presence of glucose under near-anoxia, hMSCs cultured in the absence of glucose exhibited a higher level of endoplasmic reticulum (ER) stress as evidenced by decreased nascent protein biosynthesis, and increased PERK pathway activity. Most importantly, when hMSC-containing hydrogels were implanted with glucose, the volume of newly formed blood vessels increased significantly compared to hMSC-containing hydrogels without glucose.

To accomplish our second objective, we developed a novel fibrin hydrogel composed of starch (a glucose polymer) and amyloglucosidase (AMG, an enzyme that degrades starch) to supply physiological levels of glucose to MSCs via glycolysis. Up to 14 days in vitro, hMSCs loaded in this novel starch/AMG hydrogel demonstrated improved cell survival and paracrine functions. Additionally, this novel nutritive hydrogel enhanced survival and angio-induction of MSCs when subcutaneously implanted in nude mice. However, the long-term sustainability of glucose production within the hydrogel and the complete resorption of this novel nutritive hydrogel require additional investigation.

Taken together, our findings demonstrate the beneficial effects of exogenous glucose on enhancing hMSCs-mediated angiogenesis and regulating hMSC ER stress under near-anoxia, as well as establishing proof of concept that a novel inbuilt glucose delivery system improves MSC survival and angio-induction post-implantation. These findings motivate the field to pursue a glucose-supply strategy to increase the therapeutic efficacy of MSC-mediated tissue engineering.

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