The Effects of Dietary Loading on Chondrocytes Transdifferentiation During Postnatal Maxillary Growth

The mid-palatal suture is a key growth site for transverse maxillary expansion, yet the cellular mechanisms governing its postnatal development and response to mechanical loading remain poorly defined. This study investigated the contribution of chondrocyte-derived osteogenesis to maxillary bone formation and the influence of dietary loading on this process.

Two chondrocyte-lineage tracing mouse models were utilised: Aggrecan-Cre^ERT2 (Acan^Lineage); R26R^TdTomato; 2.3Col1a1-GFP and Col10a1-Cre (Col10a1^Lineage); R26R^TdTomato; 2.3Col1a1-GFP. Twelve 3-week-old male mice per genotype were randomly assigned to either a hard diet (control) or soft diet (experimental) for 6 weeks. A single tamoxifen injection was administered to Acan^Lineage mice at 3 weeks to induce Cre event. Radiographic, uCT and histomorphometric analyses were performed.

Soft diet feeding significantly reduced maxillary arch width, bone volume and bone mineral density in the mid-palatal region. Although chondrocyte proliferation was comparable between groups, differentiation was notably impaired. Lineage tracing demonstrated that both Acan^Lineage- and Col10a1^Lineage-derived bone cells were more abundant under hard diet conditions, while non-chondrocyte-derived bone cell numbers remained similar between groups. The population of Acan^Lineage-derived pre-osteoblasts and osteocytes was markedly lower in soft diet-fed mice.

Acan⁺ chondrocytes in the mid-palatal suture contribute to postnatal maxillary bone formation through transdifferentiation. Dietary mechanical loading regulates both chondrogenesis and chondrocyte transdifferentiation, ultimately affecting maxillary bone growth and remodelling.