A novel method to isolate mesenchymal stem cells from bone marrow in a closed system using a device made by nonwoven fabric.

Bone marrow stromal cells (BMSCs) include cells with multidirectional differentiation potential described as mesenchymal stem cells. For clinical use, it is important to develop a way to isolate BMSCs from bone marrow in a closed system without centrifugation. After screening 200 biomaterials, we developed a device containing a nonwoven fabric filter composed of rayon and polyethylene. The filter selectively traps BMSCs among mononuclear cells in bone marrow based on affinity, not cell size. The cells are then recovered by the retrograde flow. Using canine and human bone marrow cells, the biological properties of BMSCs isolated by the device were compared with those obtained by conventional methods using centrifugation. The total number isolated by the device was larger, as was the number of CD106(+)/STRO-1(+) double-positive cells. The cells showed osteogenic, chondrogenic, and adipogenic differentiation potential in vitro. Finally, the direct transplantation of cells isolated by the device without in vitro cultivation accelerated bone regeneration in a canine model of osteonecrosis in vivo. The proposed method is rapid and efficient, does not require a biological clean area, and will be useful for the clinical application of mesenchymal stem cells in bone marrow.