Nondestructive evaluation of cell numbers in bone marrow stromal cell/beta-tricalcium phosphate composites using ultrasound.

Composites of bone marrow stromal cells (BMSCs)/beta-tricalcium phosphate (beta-TCP) have been increasingly used as bone substitutes and studied as a bone graft model for bone tissue engineering. The number of seeded cells in the composites is a crucial factor for achieving successful bone tissue regeneration. In this study, we showed that the actual number of cells in BMSC/beta-TCP composites 24 h after seeding at densities of 1.0 x 10(6), 1.5 x 10(6), 2.0 x 10(6), and 1.0 x 10(7) cells/mL was 2.8 +/- 1.5 x 10(5), 3.4 +/- 2.3 x 10(5), 3.7 +/- 1.0 x 10(5), and 3.7 +/- 1.8 x 10(5), respectively, indicating that even when one regular cell-seeding concentration was applied to the beta-TCP, the actual number of cells in the individual BMSC/beta-TCP composites varied considerably. In clinical setting, it is important to choose composites containing an appropriate number of cells before implanting them to patients. In an attempt to searching for the practical tools that can nondestructively evaluate the actual number of cells in beta-TCP after cell seeding, we looked into ultrasound system and developed a nondestructive and quantitative ultrasound device. We successfully demonstrated for the first time that ultrasound amplitude effectively responded to the quantity of BMSC/beta-TCP composites after 24-h cell seeding, and was well correlated to the actual number of cells contained (r = 0.903). Using this ultrasound device, orthopedic surgeons can choose composites that contain favorable number of cells before implantation. Our device could be a valuable, convenient, and nondestructive tool for future bone tissue engineering.