Bone morphogenetic protein 2 (BMP2)‐induced heterotopic bone formation (HBF) starts synchronously from zero upon BMP2 induction, which is advantageous for lineage tracking. The studies reported here in GLAST‐Cre^Ert2:tdTomato red (TR)^floxSTOPflox mice during BMP2‐induced HBF show 78.8 ± 11.6% of chondrocytes and 86.5 ± 1.9% of osteoblasts are TR⁺ after approximately 1 week. Clustering after single‐cell RNAseq resulted in nine cell types, and analysis revealed one as a highly replicating stem‐like cell (RSC). Pseudotiming suggested that the RSC transitions to a mesenchymal stem‐like cell that simultaneously expresses multiple osteoblast and chondrocyte transcripts (chondro‐osseous progenitor [COP]). RSCs and COPs were isolated using flow cytometry for unique surface markers. Isolated RSCs (GLAST‐TR⁺ Hmmr⁺ Cd200⁻) and COPs (GLAST‐TR⁺ Cd200⁺ Hmmr⁻) were injected into the muscle of mice undergoing HBF. Approximately 9% of the cells in heterotopic bone (HB) in mice receiving RSCs were GLAST‐TR⁺, compared with less than 0.5% of the cells in mice receiving COPs, suggesting that RSCs are many times more potent than COPs. Analysis of donor‐derived TR⁺ RSCs isolated from the engrafted HB showed approximately 50% were COPs and 45% were other cells, presumably mature bone cells, confirming the early nature of the RSCs. We next isolated RSCs from these mice (approximately 300) and injected them into a second animal, with similar findings upon analysis of HBF. Unlike other methodology, single cell RNAseq has the ability to detect rare cell populations such as RSCs. The fact that RSCs can be injected into mice and differentiate suggests their potential utility for tissue regeneration.

中文翻译：

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一种复制的干细胞样细胞，有助于骨形态发生蛋白 2 诱导的异位骨形成

骨形态发生蛋白 2 (BMP2) 诱导的异位骨形成 (HBF) 在 BMP2 诱导后从零同步开始，这有利于谱系追踪。GLAST-Cre ^Ert2 :tdTomato red (TR) ^floxSTOPflox小鼠在 BMP2 诱导的 HBF 期间报告的研究显示 78.8 ± 11.6% 的软骨细胞和 86.5 ± 1.9% 的成骨细胞是 TR ⁺大约 1 周后。单细胞 RNAseq 后的聚类产生九种细胞类型，分析显示一种是高度复制的干细胞样细胞 (RSC)。伪计时表明 RSC 转变为间充质干细胞样细胞，该细胞同时表达多种成骨细胞和软骨细胞转录物（软骨-骨祖细胞 [COP]）。RSCs 和 COPs 是使用流式细胞术分离的，用于独特的表面标记。将分离的 RSCs (GLAST-TR ⁺ Hmmr ⁺ Cd200 ^- ) 和 COPs (GLAST-TR ⁺ Cd200 ⁺ Hmmr ^- ) 注射到接受 HBF 的小鼠肌肉中。在接受 RSCs 的小鼠中，异位骨 (HB) 中大约 9% 的细胞是 GLAST-TR ⁺，与接受 COPs 的小鼠中不到 0.5% 的细胞相比，这表明 RSCs 的效力是 COPs 的许多倍。对从移植的 HB 中分离的供体来源的 TR ⁺ RSC 的分析显示，大约 50% 是 COP，45% 是其他细胞，可能是成熟的骨细胞，证实了 RSC 的早期性质。我们接下来从这些小鼠（大约 300 只）中分离出 RSC，并将它们注射到另一只动物中，在分析 HBF 时也有类似的发现。与其他方法不同，单细胞 RNAseq 能够检测稀有细胞群，例如 RSC。RSCs 可以注射到小鼠体内并进行分化这一事实表明它们对组织再生的潜在用途。