# Dot1l Regulates the Spontaneous Bone Regeneration of Periosteum-Derived Stem Cells by Regulating Chac1 Expression

## TL;DR

This study shows that Dot1l regulates bone regeneration by controlling Chac1 expression in periosteum-derived stem cells, offering a new target for maxillofacial bone repair.

## Contribution

The novel finding is that Dot1l influences bone regeneration through the Notch pathway by downregulating Chac1 in periosteum-derived stem cells.

## Key findings

- Dot1l overexpression inhibits osteogenic differentiation of PDSCs by reducing ALP activity and calcium deposition.
- Dot1l downregulates Chac1 expression, which affects the Notch signaling pathway in PDSCs.
- Reduced Dot1l expression in PDSCs is linked to enhanced bone regeneration in mandibular defects.

## Abstract

Background: The periosteum plays an indispensable role in bone repair, and promoting osteogenic differentiation of periosteum-derived stem cells (PDSCs) is one of the most effective strategies for enhancing spontaneous bone regeneration in maxillofacial bone defects.

Methods: We established a rat model of mandibular defects with preserved periosteum to explore its bone regeneration capacity and the potential mechanisms of PDSC activation and osteogenic differentiation.

Results: Significant bone regeneration was observed in rats with preserved periosteum after mandibular defects. To explore the underlying mechanisms, PDSCs were isolated from the periosteum of rat mandibles, and the stem cell markers CD90 and CD44 was highly expressed in these PDSCs. Further, RNA-seq, RT-qPCR, and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional analyses revealed significantly reduced expression of the Dot1l gene, and the Notch pathway was significantly enriched in the PDSCs of the model group. Osteogenic assays demonstrated that the overexpression of Dot1l significantly inhibited the alkaline phosphatase (ALP) activity, calcium deposition, and the expression of osteogenic-related genes (such as RUNX2, OSX, ALP, and OCN) in PDSCs. Additionally, Dot1l significantly affects the Notch signaling pathway in the Gene Ontology (GO) pathways, and significantly downregulates the expression of Chac1 within it. Further, Dot1l inhibited ALP activity, calcium deposition, and the expression of osteogenic-related genes in PDSCs by downregulating Chac1 expression.

Conclusions: Our study suggests that mandibular defects can induce the activation of PDSCs and inhibit the expression of Dot1l, potentially affecting the Notch signaling pathway. Targeting the Dot1l/Chac1 pathway to regulate the osteogenic differentiation of PDSCs lays a solid foundation for periosteum-based maxillofacial bone regeneration.