Isolation of bone marrow stromal cell-derived smooth muscle cells by a human SM22alpha promoter: in vitro differentiation of putative smooth muscle progenitor cells of bone marrow

背景：骨髓基质细胞(BMSCs)具有许多间充质干细胞的特性，可分化为平滑肌细胞(SMC)。然而，很少有人密切关注骨髓间充质干细胞中的平滑肌细胞系的细胞发育情况。方法和结果：为了研究在骨髓黏附细胞中是否存在符合SMC谱系的细胞群，我们试图用启动子分选的方法检测和跟踪这种细胞类型的体外分化，该方法带有人SM22pha启动子(-480bp)/绿色荧光蛋白(GFP)构建。将该构建体导入骨髓单个核细胞接种后5天出现的黏附细胞中。GFP在5天后首次在表达PDGF-β但既不表达成熟(Calponin)也不表达未成熟(SMemb)SMC特异性蛋白的细胞群[Ad(G)细胞]中检测到。然而，这些细胞最终被培养成表达SMC特异性蛋白(α-平滑肌肌动蛋白、钙蛋白和SM-1)的单个克隆，这表明Ad(G)细胞至少具有部分祖细胞特性。由于早期研究报道PDGF-β信号在间充质平滑肌祖细胞分化中起关键作用，因此Ad(G)细胞可能是表达PDGF-β的间充质平滑肌祖细胞。结论：我们证实了在骨髓间充质干细胞中存在注定要成为SMC的细胞群，并跟踪了它们向SMC的分化。

BACKGROUND: Bone marrow stromal cells (BMSCs) have many characteristics of mesenchymal stem cells that can differentiate into smooth muscle cells (SMCs). However, there have been few studies closely following the cell development of smooth muscle lineage among BMSCs. METHODS AND RESULTS: To investigate the possible existence of a cell population committed to the SMC lineage among bone marrow adhesion cells, we tried to detect and follow the in vitro differentiation of such a cell type by using a promoter-sorting method with a human SM22alpha promoter (-480 bp)/green fluorescent protein (GFP) construct. The construct was transfected to adhesion cells that appeared 5 days after the seeding of mononuclear cells from bone marrow. GFP was first detectable 5 days aftel the transfection in a cell population [Ad(G) cells], which expressed PDGF-beta but neither mature (calponin) nor immature (SMemb) SMC-specific proteins at that time. However, the cells were eventually grown into individual clones that expressed SMC-specific proteins (alpha-smooth muscle actin, calponin, and SM-1), suggesting that Ad(G) cells have partly at least progenitor properties. Because early studies have reported that PDGF-beta signaling plays pivotal roles in the differentiation of mesenchymal smooth muscle progenitor cells, Ad(G) cells might be putative mesenchymal smooth muscle progenitors expressing PDGF-beta. CONCLUSIONS: We demonstrated the presence of a cell population fated to become SMCs and followed their differentiation into SMCs among BMSCs.