Restoring balance to the immune system via Ex Vivo MSC therapy

Abstract

Background & Aim Mesenchymal stromal cells (MSCs) are shown to secrete potent immunomodulatory molecules and extracellular vesicles. However, delivery of these cells has yielded limited success in clinical applications, likely due to ineffective dosing and exposure times. To overcome these hurdles, Sentien Biotechnologies developed SBI-101, a continuous flow bioreactor with MSCs immobilized on the extraluminal side of a semi-permeable hollow-fiber membrane. Patient's blood flows through the lumen of the hollow fibers and is conditioned by MSC-secreted factors, allowing for the blood cells and MSCs to sense their environment and react to it. To study the effect of MSC-secreted factors delivered in this way, Sentien developed a scaled-down bioreactor system and explored its therapeutic efficacy through treatment of immune cell populations in vitro. Methods, Results & Conclusion MSCs were seeded into the extracapillary space of bioreactors at doses ranging from 0 (acellular control) to 9 million cells per device. Bioreactors were then perfused with media up to 8 days, with metabolite and cytokine analyses performed longitudinally. Data showed consumption of nutrients and production of cellular byproducts in a dose-dependent manner, indicating the maintenance of metabolically active MSCs over the perfusion time-course. Furthermore, MSCs were found to secrete a range of factors, including immunomodulatory and angiogenic, when immobilized in this way. Upon introduction of inflammatory stimuli to the in vitro system, MSCs modulated their secretion of factors and extracellular vesicles in response. Vesicle size and production of immunomodulatory factors, including IL-6 and PGE2, increased with stimuli. Activated PBMCs were then added to the perfusion medium to probe the effect of MSCs on inflamed blood cells. MSC treatment proved to regulate inflammatory milieu through modulation of cytokines and extracellular vesicles, suppressing T cell proliferation as well as decreasing cytotoxic and activated T cell populations. Conditioned medium and cells harvested from the perfusion circuits were further challenged via post-perfusion static assay. Treatment strategy was shown to influence lymphocyte and macrophage phenotype, proving a durable reprogramming effect. Thus, we report the ability of a hollow-fiber bioreactor to effectively maintain MSC function as well as impart an immunomodulatory effect on inflamed immune cell populations, laying the framework for a new generation of ex vivo cellular therapeutics.