<p>It is estimated that 1 in 500 Americans are inflicted with type I diabetes (T1D) with approximately 18,000 children and adolescents diagnosed each year. Islet/β cell replacement with long-lasting glucose-sensing and insulin-releasing functions has the potential to eliminate the need for insulin injections and minimize complications for individuals with T1D. However, limitations remain precluding it from widespread clinical use, including i) limited donor supply, ii) significant loss of functional islet mass upon transplantation, iv) limited functional longevity, and v) need for life-long systemic immunosuppression. To restore glucose-responsive insulin-release back to the patient’s body without the need for systemic immunosuppression, our approach involves a subcutaneous injection using a novel fibril-forming biologic, type I oligomeric collagen (Oligomer). Oligomer protects and in situ encapsulates replacement cells beneath the skin by transitioning from a liquid to a stable collagen-fibril scaffold, within seconds, just like those found in the body’s tissues. Preclinical validation studies in streptozotocin-induced diabetic mice show that replacement of islets at a dose of 500 or 800, results in a rapid (within 24 hours) reversal of hyperglycemia. All animals receiving syngeneic islets maintained euglycemia for beyond 90 days, while >80% of animals receiving allogeneic or xenogeneic (rat) islets remained euglycemia for at least 50 days. Histopathological analysis of Oligomer-islet implants showed normal morphology with no apparent evidence of a foreign body response and immune cell infiltrate. To our knowledge, this is the first report of an injectable subQ islet transplant strategy that yields rapid lowering and extended glycemic control without systemic immunosuppression.</p>

<p>Type 1 Diabetes Mellitus (T1D), a chronic disease affecting over 1.5 million Americans, is characterized by the autoimmune destruction of insulin-producing β-cells within pancreatic islets. Islet/β-cell replacement therapies, where replenishable β-cell sources are implanted within protective microenvironments, have the potential to provide a long-term solution for individuals with T1D by restoring glucose-sensitive, insulin release and overall glycemic control. However, most conventional encapsulation materials elicit an immune reaction, known as a foreign body response (FBR), which compromises β-cell health and function. In this dissertation, we designed and evaluated various formulations of a polymerizable collagen, namely type I oligomeric collagen (Oligomer), as encapsulation materials for minimally invasive, subcutaneous delivery of replacement β-cells. Preclinical validation in chemically-induced diabetic mice demonstrated rapid (within 24 hours) reversal of diabetes for beyond 90 days with no signs of rejection or FBR after subcutaneous delivery of both allogeneic and xenogeneic (rat) islets. To further define this uncommon mechanism of protection, the tissue response to Oligomer, in comparison to commercial synthetic and collagen-based materials, was evaluated following subcutaneous implantation within rats, a well-established biocompatibility model. Histological and transcriptomics analyses were used to define the immune response at both cellular and molecular levels. Interestingly, Oligomer showed minimal and transient activation of innate immune cells similar to the sham surgical control, with no evidence of foreign body giant cell formation, inflammatory-mediated bioresorption, or fibrosis. Overall, this work evaluates preclinical efficacy and demonstrates mechanistic understanding of immune tolerance for Oligomer materials for β-cell replacement therapy and other regenerative medicine applications.</p>

Résumé : Durant les dernières années, l’encapsulation d’îlots pancréatiques endocriniens a reçu une grande attention parce qu’elle pourrait constituer une solution pour diminuer les taux d'échecs des transplantations. Dans le contexte de la perte de la matrice extracellulaire (MEC) native des îlots lors de leur isolation et le rejet de greffes par le système immunitaire du receveur, cette thèse vise à améliorer la compréhension des interactions entre la MEC et les cellules des îlots pancréatiques endocriniens ainsi qu’à étudier les effets de stress apoptotiques associés à des éléments du système immunitaire sur la survie et les fonctions des îlots. Ces études pourraient permettre de raffiner notre compréhension des mécanismes associés au rejet des greffes d'îlots de Langerhans. Dans cette thèse, le premier chapitre constitue une revue de la littérature permettant de mettre en lumière les rôles réciproques de la MEC dans l'action des cellules immunitaires et l'influence de ces rôles sur le diabète de type 1 (DT1) et sur la transplantation d'îlots. Ce premier chapitre a été publié dans la revue Pathologie Biologie. Le premier travail expérimental comprend la culture de cellules d'insulinomes de rat (INS-1) sur des surfaces composées de carboxyméthyl dextrane (CMD) recouvertes de fibronectine, RGD ou YIGSR, un peptide synthétique de la laminine. Dans cette étude, l'effet bénéfique d’éléments de la MEC sur ces cellules productrices d'insuline a été démontré. Les cellules INS-1 ont davantage proliféré sur ces surfaces et sécrétaient plus d’insuline que les cellules INS-1 cultivées sur les surfaces contrôle de CMD, CMD+RGE et dans les plaques à multi-puits de polystyrène vendues pour la culture tissulaire (TCPS). Cette première étude a été publiée dans Acta Biomaterialia. La deuxième étude expérimentale avait pour objectif d’étudier l’effet protecteur de gels de fibrine pour enrober des îlots pancréatiques endocriniens isolés de jeunes porcs et exposés à deux concentrations de peroxyde d'hydrogène (H[indice inférieur 2]O[indice inférieur 2]). L’enrobage dans la fibrine a permis de réduire l'apoptose chez les cellules des îlots et d’améliorer la sécrétion d'insuline par ceux-ci lorsque les résultats étaient comparés à ceux des îlots non-enrobés. Ce travail a été publié dans la revue Islets. Dans la troisième étude expérimentale, des îlots porcins étaient enrobés dans des gels de fibrine et d'alginate et exposés à des monocytes humains pour comparer l’effet de l’enrobage par ces deux matériaux sur la survie et les fonctions des îlots. Les monocytes sécrétaient des concentrations importantes de cytokines TNFα, IL-6, IL-1β en réponse à la fibrine seule et aux îlots. Les cellules des îlots enrobés dans les gels de fibrine et d'alginate étaient moins apoptotiques et sécrétaient plus d'insuline que leurs contrôles respectifs non-enrobés. Cette étude a été acceptée dans la revue Pathologie Biologie. // Abstract : In recent years, the encapsulation of endocrine pancreatic islets has received enhanced attention as it might constitute a solution for islet transplantation failure. In the context of the loss of the native islet extracellular matrix (ECM) and graft rejection by the recipient’s immune system, this thesis aims to improve the understanding of ECM-islet cell interactions and immune system-related implications in islet survival and function in the context of type 1 diabetes mellitus (T1DM) and islet graft rejection. In the first chapter, a literature review introduces the reciprocal roles of the ECM in immune cell action and the influence of these interactions on T1DM and islet transplantation. The most important ECM components are discussed followed by an overview of immune cells and their possible implication in diabetes. Immune cell integrins and cytokines and their communication with and influence on ECM are highlighted, concluding in a brief discussion of the significance of these interactions for islet transplantation and encapsulation. This review has been accepted for publication by Pathologie Biologie. The first experimental work comprises the culture of rat insulinoma cells (INS-1) on welldefined low-fouling carboxymethyl-dextran (CMD) surfaces covalently grafted with fibronectin, RGD and YIGSR, a synthetic laminin peptide, resulting in higher cell proliferation and insulin secretion of INS-1 cells when compared to the controls CMD, CMD+RGE and tissue culture polystyrene (TCPS) plates. With this work, the beneficial effect of ECM cues on insulin-producing cells was proven. This study has been published in Acta Biomaterialia. The second experimental work aimed to study the effect of fibrin gels when used to embed endocrine pancreatic islets isolated from young pigs and exposed to hydrogen peroxide (H[subscript 2]O[subscript 2]). Fibrin-embedded islets showed less apoptosis and higher relative insulin secretion than islets on TCPS, verifying the protective effect of fibrin towards islets. This study has been published in Islets. In the third experimental study, porcine islets were encapsulated in fibrin and alginate gels and exposed to human monocytes to compare the two materials and to further investigate the immune protective properties of fibrin and alginate. Monocytes secreted high concentrations of TNFα, IL-6, and IL-1β in response to fibrin, but at the same time islets in both fibrin and alginate gels were less apoptotic and secreted more insulin then their TCPS controls. This study has been submitted to Pathologie Biologie.