The differentiation of mesenchymal stem cells by mechanical stress or/and co-culture system

https://doi.org/10.1016/j.bbrc.2006.10.170Get rights and content

Abstract

Differentiation of mesenchymal stem cells (MSCs) into anterior cruciate ligament (ACL) cells is regulated by many factors. Mechanical stress affects the healing and remodeling process of ACL after surgery in important ways. Besides, co-culture system had also showed the promise to induce MSCs toward different kinds of cells on current research. The purpose of this study was to investigate the gene expression of ACL cells’ major extracellular matrix (ECM) component molecules of MSCs under three induction groups. In addition, to follow our previous study, cell electrophoresis technique and mRNA level gene expression of MSC protein were also used to analyze the differentiation of MSCs. The results reveal that specific regulatory signals which released from ACL cells appear to be responsible for supporting the selective differentiation toward ligament cells in co-culture system and mechanical stress promotes the secretion of key ligament ECM components. Therefore, the combined regulation could assist the development of healing and remolding of ACL tissue engineering. Furthermore, this study also verifies that cell electrophoresis could be used in investigation of cell differentiation. Importantly, analysis of the data suggests the feasibility of utilizing MSCs in clinical applications for repairing or regenerating ACL tissue.

Section snippets

Materials and methods

Isolation and growth of MSCs. To isolate human MSCs, bone marrow aspirates of 10–20 ml were taken from the iliac crest of patients ranging in age from 40 to 60 years old. Institutional Review Board approval was obtained for the use of the human bone marrow. Nucleated cells were isolated with a density gradient [Ficoll/paque (Pharmacia)] and resuspended in complete culture medium. The culture medium used was Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 10% fetal calf serum

Cell morphology and orientation

When the MSCs were subjected to 10% elongation for 48 h, changes were induced in their morphology and particularly in their orientation (Fig. 1b). When cyclic strain was not applied, the cells show no particular orientation (Fig. 1a). After mechanical stress was applied, the cells orient perpendicularly to the strain axis and cause MSCs to change their morphology to spindle shape and also change their orientation. Hayakawa et al. also speculated that the stress fibers stretching and subsequently

Discussion

Our study shows mRNA expression of ACL cells’ typical markers of MSCs with significant increase in group II and group III, especially in group III. Both of the cells under group II and group III were exposure to mechanical stress, therefore, it is suggested that mechanical stress appeared to promote the increase of mRNA expression of ECM gene of cells. It is reasonable to speculate that mechanical signals may trigger cell-surface stretch receptors and adhesion sites, resulting in cascades that

Acknowledgments

The authors thank the National Taiwan University Hospital and the National Science Council of the Republic of China for their financial support.

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