Macrophage Engineering Using mRNA

Currently, macrophages are considered to play an important role in the regulation of tissue and organ homeostasis, and in autoimmune diseases, atherosclerosis, and cancer. As a promising new drug for inducing antigen-specific immunity, in vitro-transcription (IVT) mRNA has also been used to deliver genetic information directly into various cells. mRNA is easily developed, inexpensive to produce, and efficiently scalable for manufacturing purposes. Creative Biogene is a leading custom service provider in the field of mRNA-based cellular engineering and reprogramming. With experienced experts and the latest advanced technologies, we are able to reprogram tumor-associated macrophages (TAMs) using IVT mRNA for cancer treatment. Here, we highlight cell therapy with mRNA-based modified macrophages as a rapidly developing field.

Macrophages and tumor-associated macrophages (TAMs)

Macrophages

Macrophages are a type of white blood cells of the mononuclear phagocyte immune system and their chief competences are phagocytic activity as well as antigen presentation. Macrophages continuously monitor their microenvironments and clear away harmful matter, such as pathogens, cellular debris, tumor cells, and toxic metabolites. In addition to stimulating the immune system (including innate and adaptive immunity), macrophages can release a variety of active substances (such as growth factors and cytokines) to further modulate immune and inflammatory responses. In general, macrophages can be divided into two main groups, including the classically activated macrophages (M1) phenotype and alternatively activated macrophages (M2) phenotype, which is associated with their pro- and anti-inflammatory properties.

• Classically activated macrophages (M1) phenotype
• The M1 phenotype can be induced by lipopolysaccharide (LPS), interferon gamma (IFN-γ), and granulocyte-macrophage colony-stimulating factor (GM-CSF) and is characterized by TLR-2, TLR-4, CD80, and CD86 expression. M1 macrophages have pro-inflammatory activity. Since M1 phenotype expresses MHC class II molecules on their surface, they participate in the immune response. Besides, it is reported that M1 macrophages are also related to the recognition and elimination of cancer cells.
• Alternatively activated macrophages (M2) phenotype

The alternative activation of macrophages is promoted by antigen-antibody complexes, complement system components, apoptotic cells, interleukins, and so on. M2 macrophages show diverse gene expression signatures, and distinct macrophage subpopulations have been identified, including M2a, M2b, M2c, and M2d. Generally, the corresponding M2 phenotypes are characterized by high levels of CD206 (a mannose receptor) and CD163 (a scavenger receptor). M2 macrophages show pronounced anti-inflammatory properties and are implicated in extracellular matrix remodeling as well as angiogenesis. These cells suppress the immune response and are thought to be tumorigenic.

Tumor-associated macrophages (TAMs)

The circulating monocytes give rise to mature macrophages according to the conditions of the internal environment, and macrophages are converted into TAMs when they are recruited into the tumor microenvironment and in suitable conditions. TAMs include M2 macrophages and a small fraction of M1 macrophages. These cells lack the function of phagocytizing tumor cells and protect tumor cells from being killed as well as assist them to spread to other tissues and organs (tumor-promoting functions).

Fig 1. The two main subpopulations of macrophages and TAMs. (Zhou, J., et al., 2020).

Macrophage engineering using mRNA

Based on a targeted mRNA delivery system, we have the ability to deliver synthetic mRNA encoding M1-polarizing transcription factors to reprogram TAMs for the treatment of a variety of cancers, including melanoma, glioblastoma, and ovarian cancer. Our services include the design of biodegradable nanoparticles (NPs), production of IVT mRNA according to genes encoding master regulators of macrophage polarization, programming TAMs into antitumor macrophages. We have developed a targeted nanocarrier that leads to robust gene expression in TAMs. To confer macrophage-targeting, we further modify the surface of particles with Di-mannose moieties. In addition, for inducing macrophage polarization, it is a crucial step to select and produce mRNA encoding M1-polarizing transcription factors. We identify the results of NP-mediated mRNA for reprogramming by NanoString gene expression analysis in vitro (using BMDMs).

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