Suspended cells from trabecular bone by collagenase digestion become virtually identical to mesenchymal stem cells obtained from marrow aspirates

Several reports describe that the explant culture of the trabecular bone after collagenase treatment produces mesenchymal stem cells (MSCs). However, the suspended cells had not been intensively examined concerning MSCs. We hypothesized that the cells would acquire the properties of MSCs during their expansion and therefore compared them with marrow aspirate-derived MSCs. Human trabecular bones were washed, digested, filtered, and expanded clonally for 14 days. Their proliferation ability (n = 9) and differentiation potentials for chondrocyte, adipocyte, and osteoblast (n = 6) were similar with those of marrow aspirate-derived MSCs. Epitope and mRNA analysis revealed some differences in both types of cells, which disappeared with expansion and subcultivation. A mixed population of collagenase-released (CR) cells had similar differentiation potentials with CR clone, CD31(+) fraction, and osteoblastic cells. For quantitative study, trabecular bone and bone marrow were harvested by single aspiration using a biopsy needle (n = 16). Although the total nucleated cell number harvested was similar, the colony-forming efficiency of CR cells was approximately 100-fold higher than that of BM cells and more than 1 million CR cells could be obtained in 14 days from all donors. Enzymatically released cells from trabecular bone became virtually identical to marrow aspirate-derived MSCs, demonstrating that a trabecular bone fragment can be an alternative source of MSCs.