Background/Objectives: A specialized microenvironment in the bone marrow, composed of stromal cells including mesenchymal stem cells (MSCs), supports hematopoietic stem cell (HSC) self-renewal, and differentiation bands play an important role in leukemia development and progression. The reciprocal direct interaction between MSCs and CD34+HSCs under physiological and pathological conditions is yet to be fully characterized. Methods: Here, we established a direct co-culture model between MSCs and CD34+HSCs or MSCs and acute myeloid leukemia cells (THP-1, Molm-13, and primary cells from patients) to study heterocellular communication. Results: Following MSCs-CD34+HSCs co-culture, the expression of adhesion markers N-Cadherin and connexin 43 increased in both cell types, forming gap junction channels. Moreover, the clonogenic potential of CD34+HSCs was increased. However, direct contact of acute myeloid leukemia cells with MSCs reduced the expression levels of connexin 43 and N-Cadherin in MSCs. The impairment in gap junction formation may potentially be due to a defect in the acute myeloid leukemia-derived MSCs. Interestingly, CD34+HSCs and acute myeloid leukemia cell lines attenuated MSC osteoblastic differentiation upon prolonged direct cell–cell contact. Conclusions: In conclusion, under physiological conditions, connexin 43 and N-Cadherin interaction preserves stemness of both CD34+HSCs and MSCs, a process that is compromised in acute myeloid leukemia, pointing to the possible role of gap junctions in modulating stemness.
背景/目的：骨髓中的特殊微环境由间充质干细胞（MSCs）等基质细胞构成，支持造血干细胞（HSCs）的自我更新与分化，并在白血病的发生发展中起重要作用。然而，MSCs与CD34+HSCs在生理及病理条件下的双向直接相互作用机制尚未完全阐明。方法：本研究建立了MSCs与CD34+HSCs、以及MSCs与急性髓系白血病细胞（THP-1、Molm-13系及患者原代细胞）的直接共培养模型，以探究异型细胞间的通讯机制。结果：MSCs与CD34+HSCs共培养后，两种细胞中黏附标志物N-钙黏蛋白和连接蛋白43的表达均增加，并形成间隙连接通道。此外，CD34+HSCs的克隆形成能力得到增强。然而，急性髓系白血病细胞与MSCs直接接触会降低MSCs中连接蛋白43和N-钙黏蛋白的表达水平。间隙连接形成的损伤可能与急性髓系白血病来源的MSCs存在缺陷有关。值得注意的是，长期直接细胞接触后，CD34+HSCs和急性髓系白血病细胞系均会减弱MSCs的成骨分化能力。结论：综上所述，在生理条件下，连接蛋白43与N-钙黏蛋白的相互作用能维持CD34+HSCs和MSCs的干性，而这一过程在急性髓系白血病中受损，提示间隙连接可能在调节干细胞特性中发挥重要作用。
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