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The most prominent capabilities of mesenchymal stem cells (MCSs) which make them promising for therapeutic applications are their capacity to endure and implant in the target tissue. However, the therapeutic applications of these cells are limited due to their early death within the first few days following transplantation. Therefore, to improve cell therapy efficacy, it is necessary to manipulate MSCs to resist severe stresses imposed by microenvironment. In this study, we manipulated MSCs to express a cytoprotective factor, nuclear factor erythroid-2 related factor 2 (Nrf2) to address this issue. Full-length human Nrf2 cDNA was isolated and TOPO cloned into TOPO cloning vector and then transferred to gateway adapted adenovirus expression vector by LR recombination reaction. Afterwards, the Nrf2 bearing recombinant virus was prepared in appropriate mammalian cell line and used to infect MSCs. The viability and apoptosis of the Nrf2 expressing MSCs were evaluated following hypoxic and oxidative stress conditions. Transient expression of Nrf2 by MSCs protected them against cell death and the apoptosis triggered by hypoxic and oxidative stress conditions. Nrf2 also enhanced the activity of SOD and HO-1. These findings could be used as a strategy for prevention of graft cell death in MSC-based cell therapy. It also indicates that management of cellular stress responses can be used for practical applications.

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Neutrophil Gelatinase-Associated Lipocalin (NGAL/Lcn2), a member of the lipocalin family, has a variety of functions. There are extensive studies examining the expression of NGAL under harmful conditions. However, its precise function remains poorly understood. Heme Oxygenase 1 (HO-1) is an enzyme with well-established cytoprotective effects. Previous work showed that NGAL induces expression of HO-1. Interestingly, the same stimuli induced the expression of both NGAL and HO-1. The current study was designed to (1) determine whether NGAL exerts its cytoprotective effect through HO-1 and (2) compare NGAL and HO-1 with each other in terms of their protective role against oxidative stress. The current data indicate that NGAL exerts its cytoprotective effect independent of HO-1 and protects cells against oxidative stress more efficiently than HO-1. The data also strongly suggest that induction of NGAL under harmful conditions is a compensatory response to ameliorate oxidative stress-mediated toxicity. These findings may suggest new applications of NGAL, particularly when oxidative stress is a major factor.

Despite many advantages of mesenchymal stem cells (MSCs) that make them suitable for cell therapy purposes, their therapeutic application has been limited due to their susceptibility to several stresses (e.g., nutrient-poor environment, oxidative stress, and hypoxic and masses of cytotoxic factors) to which they are exposed during their preparation and following transplantation. Hence, reinforcing MSCs against these stresses is a challenge for both basic and clinician scientists. Recently, much attention has been directed toward equipping MSCs with cytoprotective factors to strengthen them against unfavorable microenvironments. Here, we engineered MSCs with lipocalin 2 (Lcn2), a cytoprotective factor that is naturally induced following exposure of cells to stresses imposed by the microenvironment. Lcn2 overexpression not only did not interfere with the multidifferentiation capacity of the MSCs but also granted many protective properties to them. Lcn2 potentiated MSCs to withstand oxidative, hypoxia, and serum deprivation (SD) conditions via antagonizing their induced cytotoxicity and apoptosis. Adhesion rate of MSCs to coated culture plates was also enhanced by Lcn2 overexpression. In addition, Lcn2 induced antioxidants and upregulated some growth factors in MSCs. Our findings suggested a new strategy for prevention of graft cell death in MSC-based cell therapy.

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Lipocalin-2 (Lcn2, NGAL) is a member of the lipocalin super family with diverse function such as the induction of apoptosis, the suppression of bacterial growth, and modulation of inflammatory response. Much interest has recently been focused on the physiological/pathological role of the lipocalin-2 that is considered to be a novel protective factor against oxidative stress. However, its precise biological roles in this protection are not fully understood. In this report we intended to test the effect of lipocalin-2 on the expression of heme oxygenase (1, 2) and superoxide dismutase (1, 2) which are two strong antioxidants. NGAL was cloned to pcDNA3.1 plasmid by using genetic engineering method. The recombinant vector was transfected to CHO and HEK293T to establish stable cell expressing NGAL and the expression of HO-1, 2 and SOD 1, 2 were compared with appropriate controls by RT-PCR and western blot. On the other hand, expression of NGAL was suppressed by siRNA transfection in order to study the effect of lipocalin-2 on mentioned genes/proteins. The results showed that the expression of HO-1 and SOD 1, 2 enzymes were higher in cells expressing recombinant lipocalin-2 compared with the control cells. Although the expression of HO-1 was lower in NGAL silencing cells, the expression of SOD 1 and SOD 2 were higher. Our data suggest that NGAL is a potent inducer of HO-1 and somewhat SOD 1 and SOD 2 and it appears that part of antioxidant property of NGAL could be attributed to the induction of HO-1and SOD 1, 2 .

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