Hyun-Ju Cho^1,2,3, Hyun-Jai Cho^1,2,3, Ho-Jae Lee^1,3, Myung-Kang Song^1,3, Ji-Yun Seo¹, Yeon-Hee Bae^1,3, Ju-Young Kim^1,3, Hae-Young Lee², Whal Lee⁴, Bon-Kwon Koo², Byung-Hee Oh², Young-Bae Park^2,3, Hyo-Soo Kim^{1,2,3,5*
 
1} National Research Laboratory for Stem Cell Niche, Seoul National University College of Medicine, Seoul, Korea, ² Cardiovascular Center & Department of Internal Medicine, Seoul National University Hospital, Seoul, Korea, ³ Innovative Research Institute for Cell Therapy, Seoul National University Hospital, Seoul, Korea, ⁴Department of Radiology, Seoul National University College of Medicine, Seoul, Korea, ⁵ World Class University Program, Department of Molecular Medicine and Biopharmaceutical Sciences, Seoul National University, Seoul, Korea

^* Corresponding author
Hyun-Ju Cho and Hyun-Jai Cho contributed equally to this work.

Abstract
Vascular calcification is an advanced feature of atherosclerosis for which no effective therapy is available. To investigate the modulation or reversal of calcification, we identified calcifying progenitor cells and investigated their calcifying/decalcifying potentials. Cells from the aortas of mice were sorted into four groups using Sca-1 and PDGFRα markers. Sca-1⁺ (Sca-1⁺/PDGFRα⁺ and Sca-1⁺/PDGFRα^-) progenitor cells exhibited greater osteoblastic differentiation potentials than Sca-1^- (Sca-1^-/PDGFRα⁺ and Sca-1^-/PDGFRα^-) progenitor cells. Among Sca-1⁺ progenitor populations, Sca-1⁺/PDGFRα^- cells possessed bidirectional differentiation potentials towards both osteoblastic and osteoclastic lineages, whereas Sca-1⁺/PDGFRα⁺ cells differentiated into an osteoblastic lineage unidirectionally. When treated with a peroxisome proliferator activated receptor γ (PPARγ) agonist, Sca-1⁺/PDGFRα^- cells preferentially differentiated into osteoclast-like cells. Sca-1⁺ progenitor cells in the artery originated from the bone marrow (BM) and could be clonally expanded. Vessel-resident BM-derived Sca-1⁺ calcifying progenitor cells displayed nonhematopoietic, mesenchymal characteristics. To evaluate the modulation of in vivo calcification, we established models of ectopic and atherosclerotic calcification. Computed tomography indicated that Sca-1⁺ progenitor cells increased the volume and calcium scores of ectopic calcification. However, Sca-1⁺/PDGFRα^- cells treated with a PPARγ agonist decreased bone formation 2-fold compared with untreated cells. Systemic infusion of Sca-1⁺/PDGFRα^- cells into Apoe^-/- mice increased the severity of calcified atherosclerotic plaques. However, Sca-1⁺/PDGFRα^- cells in which PPARγ was activated displayed markedly decreased plaque severity. Immunofluorescent staining indicated that Sca-1⁺/PDGFRα^- cells mainly expressed osteocalcin; however, activation of PPARγ triggered receptor activator for nuclear factor-κB (RANK) expression, indicating their bidirectional fate in vivo. These findings suggest that a subtype of BM-derived and vessel-resident progenitor cells offer a therapeutic target for the prevention of vascular calcification and that PPARγ activation may be an option to reverse calcification.

Citation: Cho H-J, Cho H-J, Lee H-J, Song M-K, Seo J-Y, et al. (2013) Vascular Calcifying Progenitor Cells Possess Bidirectional Differentiation Potentials. PLoS Biol 11(4): e1001534. doi:10.1371/journal.pbio.1001534

Academic Editor: Ronald M. Evans, Howard Hughes Medical Institute, The Salk Institute for Biological Studies, United States of America

Received: July 24, 2012; Accepted: February 28, 2013; Published: April 9, 2013

Copyright: ⓒ 2013 Cho 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 study was supported by the National Research Foundation, funded by the Korean Government (MEST) (2010-0020258), Republic of Korea. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Abbreviations: ALP, alkaline phosphatase; BM, bone marrow; BMT, bone marrow transplantation; MSCs, mesenchymal stem cells; NFACT1, nuclear factor of activated T-cells; OPG, osteoprotegerin; PDGFRα, platelet-derived growth factor receptor alpha; PLCγ1, phospholipase c, gamma-1; PPARγ, peroxisome proliferator activated receptor-gamma; RANK, receptor activator for nuclear factor κB; RANKL, receptor activator for nuclear factor κB ligand; Sca-1, stem cell antigen-1; TRAF6, TNF receptor associated factor 6; TRAP, tartrate-resistant acid phosphatase; VC, vascular calcification