Browsing by Subject "Heat-Shock Response"
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Item Open Access Cryopreserved Mesenchymal Stromal Cells Are Susceptible to T-Cell Mediated Apoptosis Which Is Partly Rescued by IFNγ Licensing.(Stem cells (Dayton, Ohio), 2016-09) Chinnadurai, Raghavan; Copland, Ian B; Garcia, Marco A; Petersen, Christopher T; Lewis, Christopher N; Waller, Edmund K; Kirk, Allan D; Galipeau, JacquesWe have previously demonstrated that cryopreservation and thawing lead to altered Mesenchymal stromal cells (MSC) functionalities. Here, we further analyzed MSC's fitness post freeze-thaw. We have observed that thawed MSC can suppress T-cell proliferation when separated from them by transwell membrane and the effect is lost in a MSC:T-cell coculture system. Unlike actively growing MSCs, thawed MSCs were lysed upon coculture with activated autologous Peripheral Blood Mononuclear Cells (PBMCs) and the lysing effect was further enhanced with allogeneic PBMCs. The use of DMSO-free cryoprotectants or substitution of Human Serum Albumin (HSA) with human platelet lysate in freezing media and use of autophagy or caspase inhibitors did not prevent thaw defects. We tested the hypothesis that IFNγ prelicensing before cryobanking can enhance MSC fitness post thaw. Post thawing, IFNγ licensed MSCs inhibit T cell proliferation as well as fresh MSCs and this effect can be blocked by 1-methyl Tryptophan, an Indoleamine 2,3-dioxygenase (IDO) inhibitor. In addition, IFNγ prelicensed thawed MSCs inhibit the degranulation of cytotoxic T cells while IFNγ unlicensed thawed MSCs failed to do so. However, IFNγ prelicensed thawed MSCs do not deploy lung tropism in vivo following intravenous injection as well as fresh MSCs suggesting that IFNγ prelicensing does not fully rescue thaw-induced lung homing defect. We identified reversible and irreversible cryoinjury mechanisms that result in susceptibility to host T-cell cytolysis and affect MSC's cell survival and tissue distribution. The susceptibility of MSC to negative effects of cryopreservation and the potential to mitigate the effects with IFNγ prelicensing may inform strategies to enhance the therapeutic efficacy of MSC in clinical use. Stem Cells 2016;34:2429-2442.Item Open Access The inoculum effect and band-pass bacterial response to periodic antibiotic treatment.(Mol Syst Biol, 2012) Tan, Cheemeng; Smith, Robert Phillip; Srimani, Jaydeep K; Riccione, Katherine A; Prasada, Sameer; Kuehn, Meta; You, LingchongThe inoculum effect (IE) refers to the decreasing efficacy of an antibiotic with increasing bacterial density. It represents a unique strategy of antibiotic tolerance and it can complicate design of effective antibiotic treatment of bacterial infections. To gain insight into this phenomenon, we have analyzed responses of a lab strain of Escherichia coli to antibiotics that target the ribosome. We show that the IE can be explained by bistable inhibition of bacterial growth. A critical requirement for this bistability is sufficiently fast degradation of ribosomes, which can result from antibiotic-induced heat-shock response. Furthermore, antibiotics that elicit the IE can lead to 'band-pass' response of bacterial growth to periodic antibiotic treatment: the treatment efficacy drastically diminishes at intermediate frequencies of treatment. Our proposed mechanism for the IE may be generally applicable to other bacterial species treated with antibiotics targeting the ribosomes.