All-trans Retinoic Acid regulates cellular senescence of mouse embryonic palatal mesenchyme (MEPM) cells in...

Non-syndromic cleft lip and palate is one of the most common congenital craniofacial malformations, however, its mechanism is not well understood. A number of relevant studies have confirmed that the cleft lip and palate is caused by the interaction of environmental and genetic factors. Retinoic acid is one of the metabolites of vitamin A and is involved in various physiological functions in the body, which is essential for the regulation of cell growth and differentiation and the maintenance of normal human development. However, excessive intake of All-trans Retinoic Acid (atRA) is one of the etiological factors contributing to the development of cleft palate. Cell senescence is a hot topic and a new direction in recent years, which is related to the occurrence of various tumors and diseases. From the perspective of cellular senescence, this study aimed to verify the mechanism of action of atRA-induced cleft palate in model of mouse embryonic palatal mesenchyme (MEPM) cells. This study aims to verify whether the pathogenesis of the atRA-induced cleft palate occurs because the cellular senescence of MEPM cells via 53/p21 signaling pathway.

The palate tissues of atRA-induced cleft palate were obtained for section staining and western blotting test. MEPM cells were obtained from palate tissues and cultured in vitro, and then MEPM cells in vitro were treated with atRA. To verify that the atRA could affect the cell proliferative ability and cellular senescence of MEPM cells through the p53/p21 pathway, which resulted in the failure of palatal fusion in embryonic mice, leading to cleft palate. The senescence-associated β-Galactosidase staining, CCK-8 activity assay, cell cycle analysis and western blotting test were used.

In atRA-induced cleft palate group, tissue sections of the palate showed that there was no change in TUNEL apoptosis fluorescence staining. However, there was increased cellular senescence in MEPM cells treated with atRA as characterized by enhancing senescence-associated β-galactosidase (SA-β-Gal) activity, reducing cell proliferation, inducing MEPM cells cell cycle arrest at G1 phase and increasing expression of the senescence markers p53 and p21. p53/p21 signaling pathway was up-regulated, which could induce the cells to undergo senescence, resulting in a decrease of cell proliferative ability.

Our experimental results have shown that atRA could increase cell senescence through the p53/p21 signaling pathway in MEPM cells and diminish cell activity and proliferation ability, inducing the occurrence of cellular senescence and resulting in cleft palate in the embryonic mouse. From the viewpoint of cellular senescence, this study is intended to expand the mechanism of action of atRA-induced cleft palate as well as to provide new ideas for the study of the etiology of cleft palate.