In vivo analysis of the presence of heme oxygenase-1, transcription factor Jun-D and CD90+/CD73+/CD105+/CD45- cells in the pulp of bleached teeth.

Abstract

To investigate hydrogen peroxide (H2 O2 )-induced responsiveness in pulp cells using heme oxygenase-1 (HO-1) immunolabelling, Jun-D immunolabelling to study the effects of H2 O2 on odontoblastic differentiation and CD90+/CD73+/CD105+/CD45- cell counting for in vivo identification of mesenchymal stem cells in the pulp. The maxillary molars of 50 rats were treated with a bleaching gel (35% H2 O2 , 1×30min) or placebo gel (control groups). At 2, 3, 7, 15 and 30days after the treatment (n=10), inflammation in pulp tissue was analysed by haematoxylin-eosin staining, HO-1- and Jun-D-immunolabelled cells were counted in each third of the pulp chamber, and the number of CD90+/CD73+/CD105+/CD45- cells was quantified by immunofluorescence. The results were assessed using the Paired t-test or Wilcoxon signed-rank test (P<0.05). Significant H2 O2 -induced inflammation was noted at 2 and 3days (P<0.05), with tertiary dentine formation occurring from 7days. The bleached specimens had greater HO-1 immunolabelling in the middle and cervical thirds of the coronal pulp at 2 and 3days, in all thirds at 7days, and in the occlusal third at 15days (P<0.05), and significant nuclear Jun-D immunolabelling in the cervical third at 2 and 3days and in the occlusal and middle thirds at 7days (P<0.05). Bleached and control groups had low numbers of CD90+/CD73+/CD105+/CD45- cells in the pulp at all periods (P>0.05). Pulp cells responded to oxidative stress by expressing HO-1 during the post-bleaching inflammation phase until the beginning of the repair phase. Jun-D expression occurred during the reduction of inflammation and the beginning of tertiary dentine production. The presence of oxidative stress did not influence the number of CD90+/CD73+/CD105+/CD45- cells identified in vivo in the dental pulp.