Spatiotemporal distribution and differentiation potential of Col1+ cells in alveolar socket healing

Objective·To combine the Cre/loxP recombinase system with a tooth extraction model to explore the spatiotemporal distribution of Col1+ cells secreting type Ⅰ collagen (collagen type Ⅰ, COL1) during alveolar socket healing and their potential to differentiate into osteoblasts.Methods·Col1-CreERT2 mice were mated with Rosa26-LoxP-Stop-LoxP-tdTomato mice to obtain Col1-CreERT2;tdTomato double transgenic offspring mice. Fifteen offspring mice were selected and tamoxifen (TA) was intraperitoneally injected to label the Col1+ cell lineage. One week later, the right maxillary first molars of the offspring mice were completely extracted under general anesthesia to establish a double transgenic mouse tooth extraction model. The offspring mice were divided into 5 groups, with 3 mice in each group. Maxillary bone samples were collected at 0, 3, 7, 14, and 28 days after tooth extraction, respectively. Paraffin sections were used to observe the dynamic distribution of the Col1+ cell lineage during alveolar socket healing. Immunofluorescence techniques were employed to label the osteoblast-specific transcription factor osterix (OSX), vascular marker endomucin (EMCN), and neuronal marker β3-tubulin to investigate the osteogenic potential of Col1+ cells and their spatial localization relationship with blood vessels and nerves.Results·The tooth extraction model of Col1-CreERT2;tdTomato double transgenic mice was successfully established. Paraffin section observations revealed that Col1+ cells appeared in the alveolar socket on the third day after the model was established; on the seventh day, the number of Col1+ cells increased and alveolar socket osteogenesis gradually occurred; on the 28th day, the proportion of Col1+ cells further increased and they were distributed around the bone trabeculae. The results of statistical analysis showed that the number of Col1+ cells increased over time during alveolar socket healing (all P