Determination of cryoprotectant for magnetic cryopreservation of dental pulp tissue.

Dental pulp, covered with dental hard tissue, is a promising source of mesenchymal stem cells and osteoprogenitor cells for regenerative medicine. Our previous studies showed that 73% of dental pulp cells isolated from magnetically cryopreserved teeth where their viability, morphology, and expression of stem cell surface markers were similar to the cells isolated from fresh teeth, suggesting that magnetic cryopreservation is an applicable method for intact tooth as well as dental pulp tissue banking. However, the cryoprotectant, concentration, contact surface, and equilibration time for magnetic cryopreservation of dental pulp require optimization. In addition, the integrity and viability of post-thawed dental pulp with and without dental hard tissue covering after magnetic cryopreservation were investigated. Lower concentration of the cryoprotectant (5% dimethyl sulfoxide [DMSO]) and shorter preequilibration time are required for magnetic cryopreservation compared with the conventional cryopreservation method. The structure of at least 33% of post-thawed pulp with dental hard tissue from the open end remained intact where >80% of cells were viable. The addition of the cryoprotectant additive trehalose did not replace or improve DMSO's efficacy for magnetic cryopreservation of dental pulp or intact tooth. Tooth banking for transplantation provides an alternative treatment to replace missing teeth. The optimized cryoprotectant conditions for dental pulp tissue during magnetic cryopreservation should lead to more satisfactory outcomes in clinical applications such as autotransplantation and the isolation and expansion of dental pulp stem cells for tissue repair.