Research Article Toll-like receptor 9 ligands enhance mesenchymal stem cell invasion and expression of matrix metalloprotease-13 S. Nurmenniemi a,b,c , P. Kuvaja d,e, ⁎ , S. Lehtonen d , S. Tiuraniemi d , I. Alahuhta a,c , R.K. Mattila f , J. Risteli b , T. Salo a,c,g , K.S. Selander e,h , P. Nyberg a,c,1 , P. Lehenkari d,e,1 a Department of Diagnostics and Oral Medicine, Institute of Dentistry, University of Oulu, Oulu, Finland b Department of Clinical Chemistry, Institute of Diagnostics, University of Oulu, Oulu, Finland c Oulu Center for Cell-Matrix-Research, University of Oulu, Oulu, Finland d Clinical Research Centre, Department of Surgery, University of Oulu, Oulu, Finland e Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, Oulu, Finland f Department of Medical Microbiology, Institute of Diagnostics, University of Oulu, Oulu, Finland g Oulu University Hospital, Oulu, Finland h Division of Hematology-Oncology, Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA ARTICLE INFORMATION ABSTRACT Article Chronology: Received 29 March 2010 Revised version received 20 May 2010 Accepted 21 May 2010 Available online 27 May 2010 Human mesenchymal stem cells (hMSCs) are multipotent cells that are found in the bone marrow. Inflammation and tissue damage mobilize MSCs and induce their migration towards the damaged site through mechanisms that are not well defined. Toll-like receptor-9 (TLR9) is a cellular receptor for microbial and vertebrate DNA. Stimulation of TLR9 induces inflammatory and invasive responses in TLR9-expressing cells. We studied here the expression of TLR9 in human MSCs and the effects of synthetic TLR9-agonists on their invasion. Constitutive expression of TLR9 was detected in human MSCs but the expression was suppressed when MSCs were induced to differentiate into osteoblasts. Using standard invasion assays and a novel organotypic culture model based on human myoma tissue, we discovered that stimulation with the TLR9 agonistic, CpG oligonucleotides increased the invasion capacity of undifferentiated MSCs. Simultaneously, an increase in MMP-13 synthesis and activity was detected in the CpG-activated MSCs. Addition of anti-MMP-13 antibody significantly diminished the CpG-induced hMSC invasion. We conclude that treatment with TLR9-ligands increases MSC invasiveness, and this process is at least partially MMP-13-mediated. © 2010 Elsevier Inc. All rights reserved. Keywords: Mesenchymal stem cells Toll-like receptor-9 Matrix metalloprotease-13 Invasion Organotypic culture EXPERIMENTAL CELL RESEARCH 316 (2010) 2676 – 2682 ⁎ Corresponding author. Department of Anatomy, Institute of Biomedicine, P.O. Box 5000, FIN-90014, University of Oulu, Oulu, Finland. Fax: +358 85376335. E-mail address: paula.kuvaja@oulu.fi (P. Kuvaja). Abbreviations: CAF, cancer-associated fibroblast; ECM, extracellular matrix; IL, interleukin; MMP, matrix metalloprotease; MSC, mesenchymal stem cell; NF-κB, nuclear factor κB; TGF-β, transforming growth factor β; TLR, toll-like receptor 1 These authors made equal contribution. 0014-4827/$ – see front matter © 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.yexcr.2010.05.024 available at www.sciencedirect.com www.elsevier.com/locate/yexcr