ORIGINAL ARTICLE HIF-1a Confers Resistance to Induced Stress in Bone Marrow-derived Mesenchymal Stem Cells Ali Asghar Kiani, a Ahmad Kazemi, a Rahele Halabian, b Mahshid Mohammadipour, c Ali Jahanian-Najafabadi, d and Mehryar Habibi Roudkenar c a Department of Hematology and Blood Banking, School of Allied Medical Sciences, Tehran University of Medical Sciences, Tehran, Iran b Applied Microbiology Research Center Baqiyatallah University of Medical Science, Tehran, Iran c Blood Transfusion Research Center, High Institute for Research and Education in Transfusion Medicine, Tehran, Iran d Department of Pharmaceutical Biotechnology, School of Pharmacy, Isfahan University of Medical Sciences and Health Services, Isfahan, Iran Received for publication December 10, 2012; accepted March 5, 2013 (ARCMED-D-12-00702). Background and Aims. The major limiting factor in therapeutic application of mesen- chymal stem cells (MSCs) is their high vulnerability during the early days of transplanta- tion. Hence, researchers have been encouraged to find various strategies to make the cells resistant to different stresses before and after transplantation. Overexpression of HIF-1a in MSCs to confer resistance against harmful conditions was the aim of this study. Methods. Using an in vitro approach, we engineered MSCs to overexpress HIF-1a and then evaluated their viability following exposure to hypoxic and oxidative stresses. The inherent expression of HIF-1a was downregulated by siRNA. Viability and apoptosis of the MSCs were then evaluated in vitro following their exposure to hypoxic and oxida- tive stress conditions. Results. Whereas overexpression of HIF-1a in MSCs was protective against cell death and apoptosis triggered by hypoxic and oxidative stress conditions, its downregulation increased apoptosis and death rate. Conclusions. Our study is the first to demonstrate how human MSCs can be manipulated to gain protection against stresses that potentially limit their clinical application. Ó 2013 IMSS. Published by Elsevier Inc. Key Words: Mesenchymal stem cells, HIF-1a, HIF-1a-siRNA, Oxidative stress, Apoptosis. Introduction Mesenchymal stem cells (MSCs) are a heterogeneous subset of stromal cells with a substantial capacity for self-replication and multilineage differentiation (1). MSCs are used in treat- ment of various diseases such as myocardial infarction (2), osteogenesis imperfecta (3), degenerative diseases (4), and metabolic diseases (5), as well as bone marrow transplanta- tion (BMT) and graft vs. host disease (GVHD) (6). However, rarity of MSCs (!1/10000 of bone marrow nucleated cells) is a significant hurdle for their clinical application. Thus, MSCs are required to be expanded first in vitro, as has been already performed (7). However, in vitro processing imposes various stresses to MSCs which, along with their high vulnerability, results in a low number of viable cells (!1%) in the recipient’s body where they must also manage stressful conditions (2,8,9). Therefore, experimental manipulation of MSCs to increase their resis- tance to the mentioned stresses has been recently attempted as an approach to improve their clinical usefulness. It has been shown that MSCs are able to migrate to damaged hypoxic sites (10), and that MSCs are therapeuti- cally more effective at hypoxic sites (11). Nonetheless, it is not yet clear whether MSCs exploit anti-apoptotic mecha- nisms including upregulation of HIF-1a at hypoxic sites. HIF-1a is a well-known protein with several protective functions against stresses, especially hypoxia (12). HIF- 1a probably exerts its effects through induction of mecha- nisms involved in proliferation, metabolism, oxygen consumption, and survival (13). Furthermore, it is also Address reprint requests to: Mehryar Habibi Roudkenar, IBTO, Tehran, Republic of Iran; Phone: 989126944566l; FAX: þ982188673410; E-mail: roudkenar@ibto.ir 0188-4409/$ - see front matter. Copyright Ó 2013 IMSS. Published by Elsevier Inc. http://dx.doi.org/10.1016/j.arcmed.2013.03.006 Archives of Medical Research 44 (2013) 185e193