Senescence in palatal rugae development.

OBJECTIVES

Periodic patterning is a common feature observed in many organs and is believed to share common molecular mechanisms during development. Palatal rugae, periodically patterned ridges located on the mammalian hard palate, provide an excellent experimental model for investigating the mechanisms of periodic patterning.

METHODS

We investigated senescence during palatal rugae development in wild-type mice.

RESULTS

Senescence-associated β-galactosidase (SA-β-gal) activity was observed during palatal rugae development in wild-type mice. During embryonic days (E) 12-14, SA-β-gal activity was detected in the placodes of rugae 1-4 and 8. IL-6 and p21 expression were present in the placodes of these rugae at these stages. SA-β-gal signal began to disappear at E15 and was no longer detectable in all rugae at E16. The expression of macrophage markers was observed as SA-β-gal activity disappeared. SA-β-gal activity persisted in mice with epithelial conditional deletion of p21. Furthermore, we successfully reduced SA-β-gal activity using a senolytic drug.

CONCLUSIONS

Senescence-like cells, activated via a p21-independent pathway, are present during palatal rugae development.