Macrophage-like cells generated by phorbol myristate acetate (PMA)-induced differentiation of the THP-1 monocytic cell line are routinely used in lieu of primary macrophages for studies of macrophage polarization during host-pathogen interactions and disease progression. The phenotypes of the THP-1 macrophages are influenced by the level and duration of PMA stimulation, and possibly also by the presence of adhesion factors, such as fibronectin. Here, we use self-organizing maps (SOMs) of single-cell Raman spectra to probe the effects of PMA concentration, time interval post-PMA treatment, and adhesion factors on THP-1 cell differentiation. Raman spectra that encode for biochemical composition were acquired from individual cells on substrates coated with fibronectin or poly-L-lysine before and after stimulation with 20 nM or 200 nM PMA for 3 d, and following culture for 5 d in PMA-free medium. SOMs that show the extent of dissimilarity between the cell spectra were constructed. For all stimulation conditions, the SOMs indicated the spectra acquired from cells after 3 d stimulation had diverged from those of untreated cells. Treatment with 200 nM PMA for 3 d produced a mixture of fully and partially differentiated cells on both adhesion factor, whereas the outcome of 20 nM PMA treatment for 3 d depended on the adhesion factor. As observed for high PMA concentration, a mixture of partially and fully differentiated cells was obtained after THP-1 cells were treated with 20 nM PMA for 3 d. Conversely, cells on poly-L-lysine treated with 20 nM PMA for 3 d were spectrally different from both untreated cells and cells rested for 5 d after treatment, indicating an intermediate stage of differentiation. Thus, like primary monocyte differentiation and macrophage polarization, the transition of THP-1 monocytes into macrophage-like cells may also be modulated by integrin-binding interactions. Furthermore, the composite of culture and stimulation conditions may confound the comparison of results from separate studies.

中文翻译：

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使用单细胞拉曼光谱的自组织图探索单核细胞系的成熟

由佛波肉豆蔻酸酯乙酸酯（PMA）诱导的THP-1单核细胞系分化产生的巨噬细胞样细胞通常用于代替初级巨噬细胞，用于研究宿主-病原体相互作用和疾病进展期间的巨噬细胞极化。THP-1巨噬细胞的表型受PMA刺激水平和持续时间的影响，还可能受粘附因子（例如纤连蛋白）的存在的影响。在这里，我们使用单细胞拉曼光谱的自组织图（SOM）来探查PMA浓度，PMA处理后的时间间隔以及粘附因子对THP-1细胞分化的影响。在用20nM或200nM PMA刺激3 d前后，从涂有纤连蛋白或聚L-赖氨酸的基质上的单个细胞获取编码生物化学成分的拉曼光谱，然后在不含PMA的培养基中培养5天。构建了显示细胞光谱之间差异程度的SOM。对于所有刺激条件，SOM均表明3天刺激后从细胞获得的光谱与未经处理的细胞不同。用200 nM PMA处理3 d会产生两种粘附因子均完全分化和部分分化的细胞，而20 nM PMA处理3 d的结果取决于粘附因子。如对高PMA浓度观察到的，用20nM PMA处理THP-1细胞3天后，获得了部分分化和完全分化的细胞的混合物。相反，用20 nM PMA处理3 d的聚L-赖氨酸细胞与未处理细胞和处理后静置5 d的细胞光谱不同，表明分化的中间阶段。因此，像原代单核细胞分化和巨噬细胞极化一样，THP-1单核细胞向巨噬细胞样细胞的过渡也可以通过整联蛋白结合相互作用来调节。此外，培养和刺激条件的综合可能会混淆来自单独研究的结果的比较。