Department of Biological Sciences, Oakland University, Rochester, Michigan.
School of Dentistry, University of California, Los Angeles, Los Angeles, California.
Orthod Craniofac Res. 2019 May;22 Suppl 1:192-198. doi: 10.1111/ocr.12260.
Skeletal stem cells (SSCs) are characterized by expression of cell surface biomarkers and their ability to differentiate into bone, cartilage and fat. However, the current biomarkers used to identify these cell populations are not cell-type-specific or indicative of the differentiation status of these cells and are therefore unreliable. Our objective was to identify alternative cell surface biomarkers and transcription factors shared between SSCs isolated from the bone marrow (BM) and those derived from pluripotent stem cells (PSC).
Human PSCs were induced into SSCs. FACS and qRT-PCR were used to determine differences in expression of cell surface biomarkers and transcription factors between SSCs derived from PSCs and isolated from BM, in differentiating cells, in cells from early and late passage, and in fibroblasts.
A significant reduction in proliferation and capacity of SSCs to differentiate into adipocytes and osteoblasts was observed after 3 passages. Protein and mRNA analysis indicated that commonly used biomarkers remain highly expressed in cells that lost capacity for differentiation. However, integrin α6 (CD49f) and transcription factors GATA6, PRDM16, SIM2 and SOX11 were significantly upregulated in SSCs compared to fibroblasts. In early stages of adipogenic and osteogenic differentiation, the expression of CD49f, GATA6 and SIM2 was reduced in later passage cells, which have limited proliferation and differentiation capabilities.
Our results suggest that CD49f and transcription factors GATA6 and SIM2 identify functional SSCs.
骨骼干细胞（SSC）的特征在于细胞表面生物标志物的表达及其分化为骨、软骨和脂肪的能力。然而，目前用于鉴定这些细胞群体的生物标志物不是细胞类型特异性的，也不能指示这些细胞的分化状态，因此不可靠。我们的目标是确定从骨髓（BM）分离的 SSC 和多能干细胞（PSC）衍生的 SSC 之间共享的替代细胞表面生物标志物和转录因子。
将人 PSC 诱导为 SSC。使用 FACS 和 qRT-PCR 来确定源自 PSC 的 SSC 与从 BM 分离的 SSC 之间、在分化细胞中、在早期和晚期传代细胞中以及在成纤维细胞中表达细胞表面生物标志物和转录因子的差异。
在传代 3 次后，观察到 SSC 的增殖能力和分化为脂肪细胞和成骨细胞的能力显著降低。蛋白和 mRNA 分析表明，在失去分化能力的细胞中，常用的生物标志物仍高度表达。然而，与成纤维细胞相比，整合素α6（CD49f）和转录因子 GATA6、PRDM16、SIM2 和 SOX11 在 SSC 中显著上调。在成脂和成骨分化的早期阶段，CD49f、GATA6 和 SIM2 的表达在具有有限增殖和分化能力的后期传代细胞中降低。
我们的结果表明，CD49f 和转录因子 GATA6 和 SIM2 可识别功能性 SSC。
