Dissecting regulatory T cell expansion using polymer microparticles presenting defined ratios of self-antigen and regulatory cues.

Biomaterials allow for the precision control over the combination and release of cargo needed to engineer cell outcomes. These capabilities are particularly attractive as new candidate therapies to treat autoimmune diseases, conditions where dysfunctional immune cells create pathogenic tissue environments during attack of self-molecules termed self-antigens. Here we extend past studies showing combinations of a small molecule immunomodulator co-delivered with self-antigen induces antigen-specific regulatory T cells. In particular, we sought to elucidate how different ratios of these components loaded in degradable polymer particles shape the antigen presenting cell (APC) -T cell interactions that drive differentiation of T cells toward either inflammatory or regulatory phenotypes. Using rapamycin (rapa) as a modulatory cue and myelin self-peptide (myelin oligodendrocyte glycoprotein- MOG) - self-antigen attacked during multiple sclerosis (MS), we integrate these components into polymer particles over a range of ratios and concentrations without altering the physicochemical properties of the particles. Using primary cell co-cultures, we show that while all ratios of rapa:MOG significantly decreased expression of co-stimulation molecules on dendritic cells (DCs), these levels were insensitive to the specific ratio. During co-culture with primary T cell receptor transgenic T cells, we demonstrate that the ratio of rapa:MOG controls the expansion and differentiation of these cells. In particular, at shorter time points, higher ratios induce regulatory T cells most efficiently, while at longer time points the processes are not sensitive to the specific ratio. We also found corresponding changes in gene expression and inflammatory cytokine secretion during these times. The in vitro results in this study contribute to in vitro regulatory T cell expansion techniques, as well as provide insight into future studies to explore other modulatory effects of rapa such as induction of maintenance or survival cues.

D-dimer Release From Livers During Ex Situ Normothermic Perfusion and After In Situ Normothermic Regional Perfusion: Evidence for Occult Fibrin Burden Associated With Adverse Transplant Outcomes and Cholangiopathy.

BACKGROUND: Deceased donor livers are prone to biliary complications, which may necessitate retransplantation, and we, and others, have suggested that these complications are because of peribiliary vascular fibrin microthrombi. We sought to determine the prevalence and consequence of occult fibrin within deceased donor livers undergoing normothermic ex situ perfusion (NESLiP) and evaluate a role for fibrinolysis. METHODS: D-dimer concentrations, products of fibrin degradation, were assayed in the perfusate of 163 livers taken after 2 h of NESLiP, including 91 that were transplanted. These were related to posttransplant outcomes. Five different fibrinolytic protocols during NESLiP using alteplase were evaluated, and the transplant outcomes of these alteplase-treated livers were reviewed. RESULTS: Perfusate D-dimer concentrations were lowest in livers recovered using in situ normothermic regional perfusion and highest in alteplase-treated livers. D-dimer release from donation after brain death livers was significantly correlated with the duration of cold ischemia. In non-alteplase-treated livers, Cox proportional hazards regression analysis showed that D-dimer levels were associated with transplant survival ( P = 0.005). Treatment with alteplase and fresh frozen plasma during NESLiP was associated with significantly more D-dimer release into the perfusate and was not associated with excess bleeding postimplantation; 8 of the 9 treated livers were free of cholangiopathy, whereas the ninth had a proximal duct stricture. CONCLUSIONS: Fibrin is present in many livers during cold storage and is associated with poor posttransplant outcomes. The amount of D-dimer released after fibrinolytic treatment indicates a significant occult fibrin burden and suggests that fibrinolytic therapy during NESLiP may be a promising therapeutic intervention.

Biomaterial Strategies for Selective Immune Tolerance: Advances and Gaps.

Autoimmunity and allergies affect a large number of people across the globe. Current approaches to these diseases target cell types and pathways that drive disease, but these approaches are not cures and cannot differentiate between healthy cells and disease-causing cells. New immunotherapies that induce potent and selective antigen-specific tolerance is a transformative goal of emerging treatments for autoimmunity and serious allergies. These approaches offer the potential of halting-or even reversing-disease, without immunosuppressive side effects. However, translating successful induction of tolerance to patients is unsuccessful. Biomaterials offer strategies to direct and maximize immunological mechanisms of tolerance through unique capabilities such as codelivery of small molecules or signaling molecules, controlling signal density in key immune tissues, and targeting. While a growing body of work in this area demonstrates success in preclinical animal models, these therapies are only recently being evaluated in human trials. This review will highlight the most recent advances in the use of materials to achieve antigen-specific tolerance and provide commentary on the current state of the clinical development of these technologies.

Anticancer efficacy of tannic acid is dependent on the stiffness of the underlying matrix.

Tannic acid (TA) has been previously shown to have anticancer potential for breast cancer but its effects on melanoma have not yet been investigated. Similarly, stiffness of the tumor microenvironment is known to have a profound effect on breast cancer metastasis, but little is known about its role on melanoma. The goal of the current study is to investigate the synergistic effects of TA and matrix stiffness on melanoma progression. A375 melanoma cells with metastatic potential were cultured on TA crosslinked uncompacted (UC; soft) and electrochemically compacted (ECC; stiff) collagen gels and the effects of TA on gel morphology, mechanical properties, and cellular response (i.e. morphology and proliferation) were evaluated. SEM results showed that TA crosslinking induced merging of collagen fibrils that resulted in decrease in pore size of both UC and ECC collagen gels. Tensile testing showed that TA crosslinking significantly (p < 0.05) improved the mechanical properties of ECC collagen gels. Results from Alamar blue assay showed that TA preferentially inhibited the proliferation of A375 melanoma cells compared to the non-cancerous NIH 3T3 fibroblasts on UC collagen gels. However, on ECC collagen gels, preferential effect of TA was not prevalent as proliferation of both cell types was inhibited to a similar extent. When comparing the two gel types, inhibition of A375 melanoma cell proliferation was more pronounced on TA crosslinked UC collagen gels compared to TA crosslinked ECC collagen gels. Overall, these results suggest that TA incorporated into UC collagen gels may more selectively inhibit the proliferation of melanoma cells, and that matrix stiffness is an important driver of tumor proliferation and progression.