Abstract
Mesenchymal stem cells (MSCs) have been shown to exert immunomodulatory effects in both acute and chronic diseases. In acute inflammatory conditions like sepsis, cell therapy must be administered within hours of diagnosis, requiring “off-the-shelf” cryopreserved allogeneic cell products. However, their immunomodulatory potency, particularly in abilities to modulate innate immune cells, has not been well documented. Herein we compared the stabilities and functionalities of cultured versus thawed, donor-matched MSCs in modulating immune responses in vitro and in vivo. Cultured and thawed MSCs exhibited similar surface marker profiles and viabilities at 0 hr; however, thawed MSCs exhibited higher levels of apoptotic cells beyond 4 hrs. In vitro potency assays showed no significant difference between the abilities of both MSCs (donor-matched) to suppress proliferation of activated T cells, enhance phagocytosis of monocytes, and restore endothelial permeability after injury. Most importantly, in animals with polymicrobial sepsis, both MSCs significantly improved the phagocytic ability of peritoneal lavage cells, and reduced plasma levels of lactate and selected inflammatory cytokines without significant difference between groups. These results show comparable in vitro and in vivo immunomodulatory efficacy of thawed and fresh MSC products, providing further evidence for the utility of a cryopreserved MSC product for acute inflammatory diseases.
Highlights
Preclinical studies suggest that cryopreserved Mesenchymal stem cells (MSCs) may have reduced immunomodulatory activities immediately post-thaw, may not be as effective as MSCs harvested immediately from culture
Viability was measured with Trypan blue exclusion at 0, 2, 4, and 6 hours post-thaw or harvest
While there were no significant differences in cell viability for cultured and thawed MSCs at 0 hours (92% ± 2.7% and 93% ± 2.6%) or 6 hours (91% ± 2.3% and 81% ± 2.5%, respectively) (Fig. 1A), as expected this was slightly lower for the thawed cell product at the later time point
Summary
Preclinical studies suggest that cryopreserved MSCs may have reduced immunomodulatory activities immediately post-thaw, may not be as effective as MSCs harvested immediately from culture. Given the contrasting results reported to date, whether a cryopreserved--thawed MSC product could serve as a comparably effective therapeutic substitute for freshly cultured cells is still debatable, especially for acute inflammatory conditions like ARDS or sepsis. To address this question, we compared the immunomodulatory potential of cultured versus thawed MSCs using several in vitro potency assays, as well as in an animal model of acute inflammatory disease (i.e., sepsis). The ability of the cultured and thawed MSCs to reduce inflammation and improve pathogen clearance was assessed in a CLP murine model of polymicrobial sepsis
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