Efeitos do campo magnético na criopreservação de células da polpa dentária e do tecido pulpar de dentes terceiros molares hígidos humanos

Abstract

Cell and tissue banking for use in regenerative therapy and research development becomes an important issue as life expectancy increases. This work aimed to evaluate the effects of unidirectional static magnetic fields during the initial cryopreservation process of cells and pulp tissue of healthy human third molar teeth. Dental pulps (n = 39) were obtained from third molars extracted, which were divided for cellular evaluation (n = 3) of viability and tissue evaluation (n = 36) to isolate dental pulp cells. For cell evaluation, isolated and expanded cells comprised the following groups: Group I: control, cells submitted to initial cryopreservation by conventional method; Group II: control, cells submitted to initial slow freezing; Group III: cells submitted to initial slow freezing with 150mT; Group IV: cells submitted to initial slow freezing with 290mT; Group V: cells submitted to initial slow freezing with 360mT. During cryopreservation the cells were suspended in freezing medium containing 0, 3 and 10% DMSO (dimethylsulfoxide): GI-II-III-IV-V 0%, GI-II-III-IV-V 3% and GI- II-III-IV-V 10%. For tissue evaluation, samples initially freezing in a conventional method comprised the following groups: Group I: pulps submitted to initial freezing without magnetic field (GI); Group II: pulps submitted to the initial freezing with 150mT (GII); Group III: pulps submitted to initial freezing with 290mT (GIII); Group IV: pulps submitted to the initial freezing with 360mT (GIV). Samples from cellular and tissue evaluations, after initial cryopreservation were stored in liquid nitrogen for 7 days. After the thawing process the cellular viability was measured by trypan blue and the efficiency of obtaining cells from the cryopreserved pulp by daily microscopic observation. The results showed that cell survival rates were similar between control groups and experimental groups at concentrations of 0%, 3% and 10% DMSO (p>0.05). After 96h of culture, the proliferation rate was higher for the groups exposed to the freezing medium with 3% and 10% DMSO, than DMSO free groups (p<0.05). Dental pulp cells exposed to magnetic field during freezing had a positive effect on the proliferating rate when the freezing medium was DMSO free (p<0.05). It was possible to obtain cells from all groups of the tissue analysis, and the GIV exhibited the highest efficiency rate. In conclusion, the magnetic field strength and the DMSO concentration tested, did not influence the viability rate measured by trypan blue immediately after thawing. But that promoted difference in the values of GI-II-III-IV-V 0% after 96h of cellular culture. The increase of magnetic field was directly proportional to the efficiency rate of dental pulp cell isolation from cryopreserved tissue.