engleski

In vivo Fate Mapping Identifies Periodontal Progenitor Cells

Adult progenitor cells have enormous potential for use in periodontal tissue regeneration. However, the true identity of these progenitors in vivo and their progeny has not been precisely defined. We hypothesize that expression of smooth muscle α-actin (αSMA) identifies progenitors in adult periodontal tissues. The objective of this study is to identify and trace periodontal progenitor cells in vivo. In order to determine whether αSMA promoter can identify cells with progenitor activity in vivo, we generated αSMACreERT2 mice. These were crossed with the Ai9 reporter line to generate αSMACreERT2/Ai9 mice. This allowed us to label a population of cells with a fluorescent reporter following tamoxifen induction of Cre activity. To detect transition of αSMACreERT2/Ai9 labeled cells into osteoblasts/cementoblasts we utilized a Col2.3GFP transgene and to label periodontal fibroblasts we used Scleraxis-GFP (Scx-GFP). To trace progenitor cells during normal growth, tamoxifen was administered to 3-week-old αSMACreERT2/Ai9/Col2.3GFP and αSMACreERT2/Ai9/Scx-GFP mice. Histology was performed on the second molars 2, 17 and 52 days later. To expand the pool of progenitor cells we utilized a periodontal ligament injury model. We observed a defined population of cells on day 2 after tamoxifen induction. These cells were located at the periapical region and expanded by day 17. Following 52 days we observed a significant contribution of αSMACreERT2/Ai9-labeled cells to cementoblasts (cellular cementum) which co-expressed Col2.3GFP. Seven days after injury we observed marked expansion of αSMACreERT2/Ai9-labeled cells within periodontal ligament, and at day 28 we can identify labeled periodontal fibroblasts co-expressing Scx-GFP and osteoblasts expressing Col2.3GFP. The population of cells labeled by αSMACreERT2/Ai9 shows expansion and differentiation into mature periodontal lineage cells during normal growth, and increased expansion following periodontal injury. This population may represent a source of progenitors that give rise to mature lineages of the periodontium.

Animal; Cell biology and Regeneration

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