Panoply™ Human IL4 Knockdown Stable Cell Line

Macrophages can be classified into M1 and M2 phenotypes, both of which play pivotal roles in the inflammatory process. M1 macrophages initiate inflammatory responses by releasing various pro-inflammatory cytokines (such as IL-1 and IFN-γ) and other inflammatory mediators (such as nitric oxide, glutamate, and reactive oxygen species). In contrast, M2 macrophages counteract the pro-inflammatory state mediated by M1 macrophages and promote tissue repair by secreting anti-inflammatory cytokines (such as IL-10). In the context of spinal cord injury (SCI), an imbalance between M1 and M2 macrophages leads to irreversible tissue destruction. Therefore, increasing the population of M2 macrophages and promoting macrophage polarization toward the M2 phenotype are crucial for SCI treatment. Based on this, researchers established an in vitro co-culture system to investigate the effects of neural stem cells (NSCs) on macrophages. The results demonstrated that NSCs induce macrophage polarization toward the M2 phenotype and inhibit polarization toward the M1 phenotype in an interleukin-4 (IL-4)-dependent manner. Furthermore, the nuclear factor (NF)-κB/p65 signaling pathway is involved in M1 macrophage polarization; NSCs induce M2 polarization by inhibiting the activation of the NF-κB/p65 pathway, a process that is also dependent on IL-4. These findings deepen the understanding of the pathological mechanisms underlying SCI and facilitate the exploration of novel therapeutic strategies.

Previous studies have shown that stimulation by different cytokines influences macrophage polarization (M1 or M2 phenotype). Stimulation with IL-4 or IL-13 induces M2 polarization, whereas stimulation with TNF-α or IFN-γ induces M1 polarization. To determine whether these cytokines are involved in the interaction between neural stem cells (NSCs) and macrophages, researchers cultured NSCs in neuronal differentiation medium. RT-qPCR and ELISA results revealed that, as the culture period progressed, the mRNA and protein expression levels of IL-4 in the cells increased significantly, whereas the expression levels of IL-13 or IL-10 showed no significant changes (Figure 1A and B). In contrast, no significant differences were observed in the mRNA and protein expression levels of TNF-α and IFN-γ during neuronal differentiation (Figure 1C and D). To further confirm whether IL-4 secretion is critical for NSC-induced M2 polarization of macrophages, researchers generated IL-4 knockdown NSCs (designated as NSCshIL-4) and subsequently co-cultured these cells with macrophages. RT-qPCR results showed that, compared with macrophages cultured alone, those co-cultured with NSCshIL-4 exhibited significantly higher mRNA expression levels of M1 macrophage markers (CD85 and iNOS) (Figure 1E). Conversely, the mRNA expression levels of M2 macrophage markers (CD206 and CD163) were significantly lower in macrophages co-cultured with NSCshIL-4 than in those cultured alone (Figure 1F). These results indicate that NSCs induce M2 polarization in macrophages in an IL-4-dependent manner.

Figure 1. NSCs induce M2 polarization of macrophages by upregulating IL-4. (Ji Z, et al., 2020)