Boron increases the cell viability of mesenchymal stem cells after long-term cryopreservation.

The field of stem-cell biology has emerged as a key technology for the treatment of various disorders and tissue regeneration applications. However, a major problem remains in clinical practice, which is the question of whether stem cells preserve their self-renewal and differentiation potential in the culture conditions or not. In the current study, effects of boron on the cryopreservation of human tooth germ stem cells (hTGSCs) were evaluated for the first time. The impacts of various boron concentrations (sodium pentaborate pentahydrate (NaB)) were tested on characterized hTGSCs viability for different time intervals (24, 48, and 72 h). 20 μg/ml NaB with lower Me(2)SO concentration was found to display positive effects on hTGSCs during repeated freezing and defrosting cycles, and long-term cryopreservation. After thawing, cells were analyzed for their surface antigens and differentiation capacity. hTGSCs were successfully cryopreserved without any change in their mesenchymal stem cell characteristics as they were treated with boron containing freezing medium. In addition, fatty acid composition was examined to demonstrate membrane fatty acid profiles after freeze-thawing. Besides, NaB treatment extended osteogenic and chondrogenic differentiation of hTGSCs remarkably after long-term cryopreservation with respect to control groups. The study clearly suggests that NaB has a protective role on the survival of hTGSCs in short- and long-term cryopreservation. Due to the possible storage of hTGSCs at early ages, development of a functional and reliable cryopreservation media can be designed as a future solution to the dental stem cell banking.