Controlling placental spheroid growth and phenotype using engineered synthetic hydrogel matrices.

The human placenta is a complex organ comprised of multiple trophoblast subtypes, and inadequate models to study the human placenta in vitro limit the current understanding of human placental behavior and development. Common in vitro placental models rely on two-dimensional culture of cell lines and primary cells, which do not replicate the native tissue microenvironment, or poorly defined three-dimensional hydrogel matrices such as Matrigel™ that provide limited environmental control and suffer from high batch-to-batch variability. Here, we employ a highly defined, synthetic poly(ethylene glycol)-based hydrogel system with tunable degradability and presentation of extracellular matrix-derived adhesive ligands native to the placenta microenvironment to generate placental spheroids. We evaluate the capacity of a hydrogel library to support the viability, function, and phenotypic protein expression of three human trophoblast cell lines modeling varied trophoblast phenotypes and find that degradable synthetic hydrogels support the greatest degree of placental spheroid viability, proliferation, and function relative to standard Matrigel controls. Finally, we show that trophoblast culture conditions modulate cell functional phenotype as measured by proteomics analysis and functional secretion assays. Engineering precise control of placental spheroid development in vitro may provide an important new tool for the study of early placental behavior and development.

Translation of cell therapies to treat autoimmune disorders.

Autoimmune diseases are a diverse and complex set of chronic disorders with a substantial impact on patient quality of life and a significant global healthcare burden. Current approaches to autoimmune disease treatment comprise broadly acting immunosuppressive drugs that lack disease specificity, possess limited efficacy, and confer undesirable side effects. Additionally, there are limited treatments available to restore organs and tissues damaged during the course of autoimmune disease progression. Cell therapies are an emergent area of therapeutics with the potential to address both autoimmune disease immune dysfunction as well as autoimmune disease-damaged tissue and organ systems. In this review, we discuss the pathogenesis of common autoimmune disorders and the state-of-the-art in cell therapy approaches to (1) regenerate or replace autoimmune disease-damaged tissue and (2) eliminate pathological immune responses in autoimmunity. Finally, we discuss critical considerations for the translation of cell products to the clinic.

Engineering of Trophoblast Extracellular Vesicle-Delivering Hydrogels for Localized Tolerance Induction in Cell Transplantation.

Purpose: The need for chronic systemic immunosuppression, which presents a host of acute risks to transplantation patients, remains the primary limitation for the translation of many cell therapies, such as insulin secreting cells for the treatment of type 1 diabetes. Trophoblasts are the professional tolerogenic cells of the placenta, and they secrete a range of soluble factors to induce antigen specific tolerance toward allogeneic fetal tissue during pregnancy, including extracellular vesicles. Here we develop a trophoblast extracellular vesicle-delivering hydrogel designed for sustained, localized tolerogenic factor delivery within a transplant site to induce localized tolerance toward cell grafts. Methods: We engineer a synthetic poly(ethylene glycol)-based hydrogel system to tether extracellular vesicles for sustained delivery, and compare this system to passive vesicle entrapment within an alginate hydrogel system. We characterize trophoblast extracellular vesicles for size and morphology, and evaluate vesicle tolerogenic protein content via proteomic analysis. We validate the retention and tethering of extracellular vesicles within the hydrogel systems via scanning electron and stimulated emission depletion microscopy, and measure vesicle release rate over time. Finally, we evaluate trophoblast extracellular vesicle influence on natural killer cell activation in vitro. Results: We isolated trophoblast extracellular vesicles and proteomics confirmed the presence of tolerogenic factors. We confirmed the presence of extracellular vesicles within hydrogel delivery vehicles, and synthetic hydrogels extended extracellular vesicle release relative to a passive hydrogel system. Finally, extracellular vesicles reduced natural killer cell activation in vitro, confirming the tolerogenic potential of hydrogel-delivered extracellular vesicles. Conclusions: This tolerogenic extracellular vesicle-delivering hydrogel platform designed for delivery within a transplant site could serve as an alternative to systemic immunosuppression in cell transplantation, potentially reducing the risks associated with cell therapies and widening the eligible patient population.

Biomaterial-based approaches to engineering immune tolerance.

The development of biomaterial-based therapeutics to induce immune tolerance holds great promise for the treatment of autoimmune diseases, allergy, and graft rejection in transplantation. Historical approaches to treat these immunological challenges have primarily relied on systemic delivery of broadly-acting immunosuppressive agents that confer undesirable, off-target effects. The evolution and expansion of biomaterial platforms has proven to be a powerful tool in engineering immunotherapeutics and enabled a great diversity of novel and targeted approaches in engineering immune tolerance, with the potential to eliminate side effects associated with systemic, non-specific immunosuppressive approaches. In this review, we summarize the technological advances within three broad biomaterials-based strategies to engineering immune tolerance: nonspecific tolerogenic agent delivery, antigen-specific tolerogenic therapy, and the emergent area of tolerogenic cell therapy.