Activation of αSMA expressing perivascular cells during reactionary dentinogenesis

Aim To examine the contribution of perivascular cells expressing alpha SMA to reactionary dentinogenesis. Methodology An inducible, Cre-loxP in vivo fate-mapping approach was used to examine the contribution of the descendants of cells expressing the alpha SMA-CreERT2 transgene to reactionary dentinogenesis in mice molars. Reactionary dentinogenesis was induced by experimental mild injury to dentine without pulp exposure. The Student's t test was used to determine statistical significance at *P <= 0.05. Results The lineage tracing experiments revealed that mild injury to dentine first led to activation of alpha SMA-tdTomato(+) cells in the entire pulp chamber. The percentage of areas occupied by alpha SMA-tdTomato(+) in injured (7.5 +/- 0.7%) teeth were significantly higher than in teeth without injury (2 +/- 0.5%). After their activation, alpha SMA-tdTomato(+) cells migrated towards the site of injury, gave rise to pulp cells and a few odontoblasts that became integrated into the existing odontoblast layer expressing Col2.3-GFP and Dspp. Conclusion Mild insult to dentine activated perivascular alpha SMA-tdTomato(+) cells giving rise to pulp cells as well as a few odontoblasts that were integrated into the pre-existing odontoblast layer.