Hypoxia-Induced Mitogenic Factor (HIMF/FIZZ1/RELMa) Recruits Bone Marrow-Derived Cells to the Murine Pulmonary Vasculature Daniel J. Angelini1, Qingning Su1, Irina A. Kolosova1, Chunling Fan1, John T. Skinner1, Kazuyo Yamaji-Kegan 1 , Michael Collector2, Saul J. Sharkis2, Roger A. Johns1,3* 1 Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America, 2 Department of Oncology and Cancer Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America, 3 Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America Abstract Background: Pulmonary hypertension (PH) is a disease of multiple etiologies with several common pathological features, including inflammation and pulmonary vascular remodeling. Recent evidence has suggested a potential role for the recruitment of bone marrow-derived (BMD) progenitor cells to this remodeling process. We recently demonstrated that hypoxia-induced mitogenic factor (HIMF/FIZZ1/RELMa) is chemotactic to murine bone marrow cells in vitro and involved in pulmonary vascular remodeling in vivo. Methodology/Principal Findings: We used a mouse bone marrow transplant model in which lethally irradiated mice were rescued with bone marrow transplanted from green fluorescent protein (GFP)+ transgenic mice to determine the role of HIMF in recruiting BMD cells to the lung vasculature during PH development. Exposure to chronic hypoxia and pulmonary gene transfer of HIMF were used to induce PH. Both models resulted in markedly increased numbers of BMD cells in and around the pulmonary vasculature; in several neomuscularized small (,20 mm) capillary-like vessels, an entirely new medial wall was made up of these cells. We found these GFP+ BMD cells to be positive for stem cell antigen-1 and c-kit, but negative for CD31 and CD34. Several of the GFP+ cells that localized to the pulmonary vasculature were a-smooth muscle actin+ and localized to the media layer of the vessels. This finding suggests that these cells are of mesenchymal origin and differentiate toward myofibroblast and vascular smooth muscle. Structural location in the media of small vessels suggests a functional role in the lung vasculature. To examine a potential mechanism for HIMF-dependent recruitment of mesenchymal stem cells to the pulmonary vasculature, we performed a cell migration assay using cultured human mesenchymal stem cells (HMSCs). The addition of recombinant HIMF induced migration of HMSCs in a phosphoinosotide-3-kinase-dependent manner. Conclusions/Significance: These results demonstrate HIMF-dependent recruitment of BMD mesenchymal-like cells to the remodeling pulmonary vasculature. Citation: Angelini DJ, Su Q, Kolosova IA, Fan C, Skinner JT, et al. (2010) Hypoxia-Induced Mitogenic Factor (HIMF/FIZZ1/RELMa) Recruits Bone Marrow-Derived Cells to the Murine Pulmonary Vasculature. PLoS ONE 5(6): e11251. doi:10.1371/journal.pone.0011251 Editor: Marcelo G. Bonini, University of Illinois at Chicago, United States of America Received February 22, 2010; Accepted May 25, 2010; Published June 22, 2010 Copyright: 2010 Angelini et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was supported by NIH SCCOR P50 084946 (RAJ), NIH NHLBI 39706 (RAJ), NIH fellowship T32 GM075774-09 (DJA), Maryland Stem Cell Fund Exploratory Grant (IAK), and NIH PO1 CA070970 (SJS, MC). The funders had no role in study design, data collection and anaysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: rajohns@jhmi.edu Introduction Hypoxia-induced mitogenic factor (HIMF), also known as ‘‘found in inflammatory zone 1’’ (FIZZ1) and resistin-like molecule alpha (RELMa), is a pleiotropic cytokine that is highly inducible in lung [1–3]. We have shown it to have mitogenic, angiogenic, vasocon- strictive, and chemokine-like properties [3–6]. We initially described HIMF in the remodeling vasculature of the chronic hypoxia model of pulmonary hypertension (PH) [3] and have recently determined that HIMF plays a critical role in this process [7]. In rats, in vivo knockdown of HIMF specifically in the lung reduces the mean pulmonary artery pressure, pulmonary vascular resistance, and vascular remodeling associated with chronic hypoxia, whereas pulmonary gene transfer of HIMF initiates vascular remodeling and increases these physiological measurements [7]. Liu et al. [8] has shown that HIMF plays a key role in the transition of fibroblasts to myofibroblasts, which is essential to bleomycin-induced fibrosis and may play a role in vascular remodeling associated with PH. Our lab and others have demonstrated that the addition of recombinant HIMF to cultured cells activates the phosphoinosotide-3-kinase (PI- 3K)/Akt and extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated kinase (p42/44 MAPK) pathways in several different cell types [3,9,10]. Finally, we have demonstrated that HIMF is chemotactic for undifferentiated murine bone marrow- derived (BMD) cells and this action is mediated through Bruton’s tyrosine kinase (BTK) [5]. Pulmonary vascular remodeling is a key component of the pathogenesis of PH. Recent evidence has suggested the possibility PLoS ONE | www.plosone.org 1 June 2010 | Volume 5 | Issue 6 | e11251