# The Influence of Fluidic Flow Stress on the Development of the Secondary Palate

## TL;DR

This study shows that mechanical stress from maternal movement helps develop the secondary palate in mice by promoting cell growth and bone formation.

## Contribution

The study reveals that exogenous fluidic flow stress enhances palatal development via Hippo and WNT/β-catenin pathways.

## Key findings

- Loaded palatal shelves showed increased thickness, volume, and cell proliferation.
- YAP and β-catenin nuclear translocation and osteogenic markers were upregulated in loaded tissues.
- No significant apoptosis was observed in response to mechanical stress.

## Abstract

Craniofacial development is orchestrated by a finely regulated interplay of numerous genes and signaling pathways. Palatogenesis proceeds through a complex, stepwise process, in which endogenous mechanical stresses within tissues have been implicated. However, the impact of exogenous fluidic flow mechanical stress derived from maternal movement on palatal development remains unclear. In this study, we investigated the effect of exogenous fluidic flow mechanical stress on palatal morphogenesis, focusing on the horizontal outgrowth of palatal shelves after elevation. Palatal tissues dissected from mouse embryos were subjected to organ culture with or without mechanical loading (loaded and unloaded groups, respectively). Stress magnitude was quantified by calculating wave energy, and morphometric and molecular analyses were performed. Compared with the unloaded group, palatal shelves in the loaded group showed significant increases in thickness and volume, accompanied by enhanced cell proliferation, nuclear translocation of YAP and β-catenin, and upregulation of the osteogenic markers Osterix and Osteocalcin. No significant difference in apoptosis was observed. These findings indicate that exogenous mechanical stress promotes cell proliferation and osteogenic differentiation through the Hippo and WNT/β-catenin pathways in palate explants. Our results suggest that moderate maternal movement-induced mechanical stress contributes to normal palatogenesis, providing new insights into the mechanisms underlying cleft palate.