Jarczak Justyna, Thetchinamoorthy Kannathasan, Wierzbicka Diana, Bujko Kamila, Ratajczak Mariusz Z, Kucia Magdalena
Laboratory of Regenerative Medicine, Medical University of Warsaw, Warsaw, Poland.
Stem Cell Institute at James Graham Brown Cancer Center, University of Louisville, Louisville, KY, United States.
Front Immunol. 2025 Apr 8;16:1515856. doi: 10.3389/fimmu.2025.1515856. eCollection 2025.
The complement system expressed intracellularly and known as complosome has been indicated as a trigger in the regulation of lymphocyte functioning. The expression of its genes was confirmed also in several types of human bone marrow-derived stem cells: mononuclear cells (MNCs), very small embryonic-like stem cells (VSELs), hematopoietic stem/progenitor cells (HSPCs), endothelial progenitors (EPCs) and mesenchymal stem cells (MSCs). In our previous studies, we demonstrated the expression of complosome proteins including C3, C5, C3aR, and cathepsin L in purified HSPCs. However, there is still a lack of results showing the expression of complosome system elements and other immunity-related proteins in human HSPCs at the level of single cell resolution.
We employed scRNA-seq to investigate comprehensively the expression of genes connected with immunity, in two populations of human HSPCs: CD34+Lin-CD45+ and CD133+Lin-CD45+, with the division to subpopulations. We focused on genes coding complosome elements, selected cytokines, and genes related to antigen presentation as well as related to immune regulation.
We observed the differences in the expression of several genes e.g. C3AR1 and C5AR1 between two populations of HSPCs: CD34+LinCD45+ and CD133+Lin-CD45+ resulting from their heterogeneous nature. However, in both kinds of HSPCs, we observed similar cell subpopulations expressing genes (e.g. NLRP3 and IL-1β) at the same level, which suggests the presence of cells performing similar functions connected with the activation of inflammatory processes contributing to the body's defense against infections.
To our best knowledge, it is the first time that expression of complosome elements was studied in HSPCs at the single cell resolution with the use of single cell sequencing. Thus, our data sheds new light on complosome as a novel regulator of hematopoiesis that involves intracrine activation of the C5a-C5aR-Nlrp3 inflammasome axis.
细胞内表达的补体系统即复合小体，已被证明是淋巴细胞功能调节的触发因素。其基因表达在几种类型的人骨髓来源干细胞中也得到了证实：单核细胞（MNCs）、极小型胚胎样干细胞（VSELs）、造血干/祖细胞（HSPCs）、内皮祖细胞（EPCs）和间充质干细胞（MSCs）。在我们之前的研究中，我们证明了复合小体蛋白包括C3、C5、C3aR和组织蛋白酶L在纯化的HSPCs中的表达。然而，仍然缺乏在单细胞分辨率水平上显示人HSPCs中复合小体系统元件和其他免疫相关蛋白表达的结果。
我们采用单细胞RNA测序（scRNA-seq）全面研究了人类HSPCs的两个群体：CD34+Lin-CD45+和CD133+Lin-CD45+中与免疫相关基因的表达，并将其细分为亚群。我们重点关注编码复合小体元件、选定细胞因子以及与抗原呈递和免疫调节相关的基因。
由于其异质性，我们观察到HSPCs的两个群体即CD34+LinCD45+和CD133+Lin-CD45+之间几种基因（如C3AR1和C5AR1）的表达存在差异。然而，在这两种HSPCs中，我们观察到相似的细胞亚群以相同水平表达基因（如NLRP3和IL-1β），这表明存在执行与激活炎症过程相关的相似功能的细胞，这些炎症过程有助于机体抵御感染。
据我们所知，这是首次使用单细胞测序在单细胞分辨率水平上研究HSPCs中复合小体元件的表达。因此，我们的数据为复合小体作为一种新型造血调节因子提供了新的线索，该调节因子涉及C5a-C5aR-Nlrp3炎性小体轴的内分泌激活。
