Osteogenic Factor Runx2 Marks a Subset of Leptin Receptor-Positive Cells that Sit Atop the Bone Marrow Stromal Cell Hierarchy
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Bone marrow mesenchymal stem and progenitor cells (BM-MSPCs) maintain homeostasis of bone tissue by providing osteoblasts. Although several markers have been identified for labeling of MSPCs, these labeled cells still contain non-BM-MSPC populations. Studies have suggested that MSPCs are observed as leptin receptor (LepR)-positive cells, whereas osteoblasts can be classified as positive for Runx2, a master regulator for osteoblastogenesis. Here, we demonstrate, using Runx2-GFP reporter mice,that the LepR-labeled population contains Runx2-GFPlowsub-population, which possesses higher fibroblastic colony-forming units (CFUs) and mesensphere capacity, criteria for assessing stem cell activity, than the Runx2-GFP−population. In response to parathyroid hormone (PTH), a bone anabolic hormone, LepR+Runx2-GFPlowcells increase Runx2 expression and form multilayered structures near the bone surface. Subsequently, the multilayered cells express Osterix and Type I collagen α, resulting in generation of mature osteoblasts. Therefore, our results indicate that Runx2 is weakly expressed in the LepR+population without osteoblastic commitment, and the LepR+Runx2-GFPlowstromal cells sit atop the BM stromal hierarchy.
- Scientific reports.
Scientific reports. 7(1), 4928, 2017-07-10
Nature Publishing Group