Magnesium enhances adherence and cartilage formation of synovial mesenchymal stem cells through integrins

Objective: We previously reported that more than 60% of synovial mesenchymal stern cells (MSCs) placed on osteochondral defects adhered to the defect within 10 min and promoted cartilage regeneration. The efficiency of adherence is considered to depend on the interaction between cells and extracellular matrix (ECM), in which integrins may play some important roles. Divalent cations such as calcium, magnesium, and manganese may affect functions of integrins, and the integrins may be involved in differentiation of MSCs. Among divalent cations, magnesium is used in clinical practice as a therapeutic agent and increases the affinity of integrin to ECM. In this study, we investigated whether magnesium enhanced adherence and chondrogenesis of synovial MSC through integrins. Methods: We performed assays for adherence of human synovial MSCs to collagen-coated slides, in vitro chondrogenesis, ex vivo assays for adherence of human synovial MSCs to osteochondral defect, and in vivo assays for adherence and cartilage formation of synovial MSCs in a rabbit osteochondral defect model. Results: Magnesium increased adhesion of human synovial MSCs to collagen, and this effect was inhibited by neutralizing antibodies for integrin alpha 3 and beta 1. Magnesium also promoted synthesis of cartilage matrix during in vitro chondrogenesis of synovial MSCs, which was diminished by neutralizing antibodies for integrin beta 1 but not for integrin alpha 3. Ex vivo analyses demonstrated that magnesium enhanced adherence of human synovial MSCs to osteochondral defects. In vivo studies in rabbits showed that magnesium promoted adherence at 1 day and cartilage formation of synovial MSCs at 2 weeks. Conclusion: Magnesium enhanced adherence of synovial MSCs through integrins, which promoted synthesis of cartilage matrix at an early phase. (C) 2010 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.