CD44-Expressed Exosome Modification Service

The long-term and huge challenge of exosomes as delivery vehicles is the massive uptake and rapid clearance mediated by the mononuclear phagocyte system (MPS), which greatly hinders the development of exosome delivery platforms. Investigating potential phagocytosis-evading molecules is beneficial for achieving exosome evasion of MPS regulation and improving cargo delivery. Creative Biolabs offers CD44-related exosome engineering services to assist clients in researching the function of CD44-expressed exosomes.

Overview of Exosomal Evasion of Phagocytosis

Macrophages are one of the three phagocytic cell types besides granulocytes and dendritic cells involved in the recognition, phagocytosis, and degradation of cellular debris and pathogens. Recognition and phagocytic destruction of exosomes by these phagocytes is the main reason for the short half-life of exosomes circulating in vivo after systemic injection, which greatly diminishes the therapeutic effect of the drug. It has been reported that up to 99% of systemically administered nanoparticles are cleared by the liver, while only 0.7% of the dose is delivered to solid tumors. This comes from the presence of the largest number of tissue-resident macrophages in the liver, the largest solid organ. These macrophages recognize multiple factors including antibodies, complement, and fibronectin through surface receptors to achieve wrapping and phagocytosis of foreign objects. This specific phagocytosis is an important functional feature of macrophages. Therefore, understanding and controlling the granular phagocytosis of exosomes evading macrophages is extremely critical to improve exosome delivery performance.

Different strategies have been proposed to generate "stealth" exosomes for the immune system by modifying exosomes to express different anti-phagocytic molecules on their surface. This increases the bioavailability and circulating half-life of therapeutic exosomes, allowing the delivery of exosomes to target tissues, transferring their therapeutic molecular cargo, and improving their efficacy. Therefore, it is promising to explore the effect of exosome modification by molecules associated with the phagocytosis machinery on their evasion of phagocytosis for strategies to inhibit exosome clearance and increase targeting effects.

Fig.1 The modification methods of engineered exosomes. (Xiao, 2023)

CD44-Expressed Exosome Modification

CD44 is a complex transmembrane adhesion glycoprotein expressed in various cells, including embryonic stem cells, differentiated cells, and cancer cells. Different selective splicing during transcription gives rise to two CD44 isoforms, including the standard isoform (CD44s) and the CD44 variant isoform (CD44v). CD44 is a recognized marker of tumor stem cells and a key regulator of epithelial-mesenchymal transition (EMT), involved in tumorigenesis, progression, and metastasis. On the one hand, CD44 is involved in regulating the expression of MMPs (Matrix metalloproteinases), especially MMP2 and MMP9, in a HA (hyaluronic acid)-dependent or HA-independent manner, degrading the extracellular matrix and promoting tumor invasion and metastasis. On the other hand, CD44 also promotes the separation of E-cadherin and β-catenin at the cytoplasmic membrane and promotes translocation of released β-catenin, which in turn activates genes that drive cell migration and invasion.

It is necessary for the ideal exosome vehicles to remain intact in complex biological systems and exhibit an extended circulation time in the bloodstream, so as to maximize drug delivery to the intended site and evade clearance by MPS. It was found that blocking CD44 using monoclonal antibodies inhibited macrophage-mediated phagocytosis, allowing the particles to remain in the bloodstream for longer periods. This suggests the biological relevance of studying the transport function of CD44-expressing exosomes. CD44 expression on the surface of exosomal membranes can be achieved through pre- and post-isolation approaches of exosome engineering while being compatible with the loading of therapeutic cargoes.

Fig.2 CD44 molecules, prominent ligands and associated molecules. (Wang, 2018)

CD44 is a well-recognized tumor stem cell membrane surface marker involved in tumor initiation, progression, and metastasis, while monoclonal antibodies and blocking peptides against CD44 have been applied in numerous studies for tumor intervention. Creative Biolabs has established multiple cargo loading modification strategies to provide CD44-expressed exosome modification service. Please contact us to discuss your project.

References

Xiao, G.; et al. Combinational antitumor strategies of exosomes as drug carriers: Mini review. Front Pharmacol. 2023, 13: 1107329.
Wang, Z.; et al. CD44/CD44v6 a reliable companion in cancer-initiating cell maintenance and tumor progression. Front Cell Dev Biol. 2018, 6: 97.

Plant Exosome Isolation