High-cell density-induced VCAM1 expression inhibits the migratory ability of mesenchymal stem cellsSoko Nishihira*†, Naoto Okubo*‡, Noriko Takahashi*, Akira Ishisaki*, Yoshiki Sugiyama† and Naoyuki Chosa*1*Division of Biochemistry and Molecular Genetics, Department of Oral Biology, Iwate Medical University School of Dentistry, Morioka, Iwate 0208505, Japan, †Division of Oral Surgery, Department of Oral and Maxillofacial Surgery, Iwate Medical University School of Dentistry, Morioka, Iwate 0208505, Japan, and ‡Open Research Project, Advanced Oral Health Research Center, Iwate Medical University, Morioka, Iwate 0208505, Japan

MSCs (mesenchymal stem cells) migrate into damaged tissue and then proliferate and differentiate into various cell lineages to regenerate bone, cartilage, fat and muscle. Cell–cell adhesion of MSCs is essential for the MSC-dependent tissue regeneration after their homing into a damaged tissue. However, it remains to be elucidated what kinds of adhesion molecules play important roles in the cell–cell communication between MSCs. In order to identify adhesion molecules that facilitate mutual contact between MSCs, a comprehensive analysis of mRNA expression in adhesion molecules was performed by comparing profiles of expression status of adhesion molecules in MSCs at low- and high-cell density. We found that the expression level of VCAM1 (vascular cell adhesion molecule-1)/CD106 was clearly up-regulated in the human bone marrow-derived MSCs–UE7T-13 cells – under a condition of high cell density. Intriguingly, the migratory ability of the cells was clearly accelerated by a knockdown of VCAM1. Furthermore, the migratory ability of UE7T-13 cells was decreased by the over expression of exogenous VCAM1. In addition, the high cell density-induced expression of VCAM1 was clearly suppressed by NF-κB (nuclear factor-κB) signalling-related protein kinase inhibitors such as an IKK-2 (IκB kinase-2) inhibitor VI. In conclusion, the high cell density-induced VCAM1 expression through the NF-κB pathway inhibits the migratory ability of human bone marrow-derived MSCs.

Key words: cell density, mesenchymal stem cell, migration, nuclear factor-κB pathway, vascular cell adhesion molecule-1

Abbreviations: CMVE, cardiac microvascular endothelium, DMEM, Dulbecco's modified Eagle's medium, ECs, endothelial cells, FBS, fetal bovine serum, FCM, flow cytometry, GFP, green fluorescent protein, HSCs, haematopoietic stem cells, ICAM1, intercellular adhesion molecule-1, also known as CD54, IKK-2, IκB kinase-2, IL-1, interleukin-1, MSCs, mesenchymal stem cells, NF-κB, nuclear factor-κB, PE, phycoerythrin, PI3K, phosphoinositide 3-kinase, PKC, protein kinase C, qRT-PCR, quantitative RT-PCR, RTK, receptor tyrosine kinase, RT-PCR, reverse transcription-PCR, siRNA, small interfering RNA, TNF-α, tumour necrosis factor-α, VCAM1, vascular cell adhesion molecule-1, VLA-4, very late antigen-4