Takebe Hiroaki, Sato Hanaka, Mizoguchi Toshihide, Hosoya Akihiro
Division of Histology, Department of Oral Growth and Development, School of Dentistry, Health Sciences University of Hokkaido, 1757 Kanazawa, Ishikari-Tobetsu, Hokkaido, 061-0293, Japan.
Tokyo Dental College, Oral Health Science Center, 2-9-18 Kanda Misaki-Cho, Chiyodaku, Tokyo, 101-0061, Japan.
Cell Tissue Res. 2025 Jan;399(1):119-127. doi: 10.1007/s00441-024-03940-4. Epub 2024 Nov 23.
α-Smooth muscle actin (α-SMA) is an actin isoform commonly found within vascular smooth muscle cells. Moreover, α-SMA-positive cells are localized in the dental follicle (DF). DF is derived from alveolar bone (AB), cementum, and periodontal ligament (PDL). Therefore, α-SMA-positive cells in the periodontal tissue are speculated to be a marker for mesenchymal stem cells during tooth development. In particular, the mechanism of osteoblast differentiation is not clear. This study demonstrated the fate of α-SMA-positive cells around the tooth germ immunohistochemically. First, α-SMA- and Runx2-positive localization at embryonic days (E) 13, E14, postnatal days (P) 9, and P15 was demonstrated. α-SMA- and Runx2-positive cells were detected in the upper part of the DF at P1. At P9 and P15, α-SMA-positive cells in the PDL were detected in the upper and lower parts. The positive reaction of Runx2 was also localized in the PDL. Then, the distribution of α-SMA-positive cell progeny at P9 and P15 were clarified using α-SMA-CreERT2/ROSA26-loxP-stop-loxP-tdTomato (α-SMA/tomato) mice. It has known that Runx2-positive cells differentiate into osteoblasts. In this study, some Runx2 and α-SMA-positive cells were localized in the DF and PDL. The lineage-tracing analysis demonstrated that the α-SMA/tomato-positive cells expressing Runx2 or Osterix were detected on the AB surface at P15. α-SMA/tomato-positive cells expressing type I collagen were found in the AB matrix. These results indicate that the progeny of the α-SMA-positive cells in the DF could differentiate into osteogenic cells. In conclusion, α-SMA could be a potential marker of progenitor cells that differentiate into osteoblasts.
α-平滑肌肌动蛋白（α-SMA）是一种常见于血管平滑肌细胞内的肌动蛋白异构体。此外，α-SMA阳性细胞定位于牙囊（DF）。牙囊源自牙槽骨（AB）、牙骨质和牙周韧带（PDL）。因此，牙周组织中的α-SMA阳性细胞被推测为牙齿发育过程中间充质干细胞的标志物。特别是，成骨细胞分化的机制尚不清楚。本研究通过免疫组织化学方法展示了牙胚周围α-SMA阳性细胞的命运。首先，证实了在胚胎第13天（E13）、E14、出生后第9天（P9）和P15时α-SMA和Runx2的阳性定位。在出生后第1天（P1），在牙囊上部检测到α-SMA和Runx2阳性细胞。在P9和P15时，在牙周韧带的上部和下部检测到α-SMA阳性细胞。Runx2的阳性反应也定位于牙周韧带。然后，使用α-SMA-CreERT2/ROSA26-loxP-stop-loxP-tdTomato（α-SMA/番茄）小鼠阐明了P9和P15时α-SMA阳性细胞后代的分布。已知Runx2阳性细胞可分化为成骨细胞。在本研究中，一些Runx2和α-SMA阳性细胞定位于牙囊和牙周韧带。谱系追踪分析表明，在P15时，在牙槽骨表面检测到表达Runx2或osterix的α-SMA/番茄阳性细胞。在牙槽骨基质中发现了表达I型胶原的α-SMA/番茄阳性细胞。这些结果表明，牙囊中α-SMA阳性细胞的后代可分化为成骨细胞。总之，α-SMA可能是分化为成骨细胞的祖细胞的潜在标志物。
