Exosomes carrying stable bioactive molecules, such as nucleic acids and proteins, are highly effective liquid biopsy biomarkers that can provide dynamic insights into the diagnosis and prognosis of various diseases. Benefiting from the unique role of exosomes' active cargo in mediating cellular communication, Creative Biolabs provides services related to the discovery and research of exosome markers to advance the disease diagnostic applications of exosomes.

Rationale

It has been well established that lipids and proteins in exosomes secreted by living cells via the cytosol constitute the bulk of the membrane, while various nucleic acids are stably encapsulated in the lumen. These diverse active molecules are capable of being transported through the circulation to neighboring and distant recipient cells supported by exosomal carriers, thus participating in the regulation of a wide range of intercellular communication and physiological processes. Exosomal nucleic acids, especially miRNAs, together with their target genes, form a complex regulatory network involving roles in the regulation of gene expression associated with cell proliferation, differentiation, migration, and death. Exosome next-generation sequencing (NGS)-based analysis of exosomal RNAs showed that all RNA isoforms including mRNA, lncRNA, and miRNA have been detected in exosomes and undergo changes in species composition in pathological states. In addition, exosome whole transcriptome sequencing has been used to profile exosome contents in a variety of biological fluids including cerebrospinal fluid, plasma, urine, and ascites. Thus, exosomes and their components have become promising markers for diagnostic and prognostic applications in diseases.

Diagnostic Advantages and Applications of Exosomes at Creative Biolabs

Early detection of disease progression several months before the clinical presentation and radiological confirmation can significantly reduce cancer mortality. Liquid biopsy, which samples circulating biological fluids containing active markers and performs molecular analysis, is an effective strategy for cancer non-invasive diagnosis and is considered to be a complementary method to biopsy. Liquid biopsies with exosomes as markers not only break through several limitations of traditional solid biopsies but also demonstrate superiority over other sources of liquid biopsies, including

• Sample source diversity and easy storage. Exosomes are more readily available from virtually all body fluids than circulating tumor cells, including blood, plasma, serum, urine, cerebrospinal fluid, saliva, ascites, amniotic fluid, breast milk, pleural fluid, and bronchoalveolar lavage fluid. Similar exosomal markers are observed for these samples in the fresh state, stored at 4°C for 24 hours and at -80°C for long-term storage, and the higher biological stability greatly reduces the cost and difficulty of their preservation and transportation. Hence, it demonstrates the excellent clinical applicability of exosome samples compared to other samples in terms of collection and preservation.
• Convenient sampling operability facilitates dynamic monitoring. Liquid biopsies overcome the limitations of traditional tissue biopsies that do not allow access to diseased tissue when inoperable, resulting in non-invasive, non-destructive results. This allows multiple sampling for continuous and dynamic monitoring based on liquid biopsies.
• Clearer analytical methods and more reliable predictive accuracy: exosomes prefer to be isolated in a neutral rather than acidic environment, with classical extraction methods by ultracentrifugation and continuously innovative methods under development. Recognized markers such as CD9, CD81, and TSG101 and unique cup-like features under electron microscopy are applied to effectively differentiate exosomes. Subsequently, established sequencing and histological analysis techniques are used to achieve a clear analysis of exosome-associated disease markers, possessing a more reliable diagnostic accuracy than traditional serum-based biomarkers such as a carcinoembryonic antigen.
• Richer biological information. Exosomes are generated from living cells and contain biological information about their origin, which is more representative than cell-free DNA (cfDNA) derived from necrotic and apoptotic processes. On the one hand, exosomes appear with the same surface proteins as their parental cells or even target cells, contributing to exosome isolation of specific origin and predicting metastasis to specific organs. On the other hand, the majority of plasma cfDNA in advanced plasmacytic ovarian cancer and mitochondrial DNA at higher than the plasma and peripheral blood copy numbers located in exosomes, showing the sensitivity and specificity of nucleic acid mutation frequency detection of exosomes over cfDNA.

Given the above advantages of exosomes as liquid biopsy markers, at Creative Biolabs, the diseases involved in the discovery and study of exosomes as diagnostic biomarkers include, but are not limited to:

• Tumor Diagnosis-Applied Exosomes
• Pregnancy Disorders Diagnosis-Applied Exosomes
• Cardiovascular Diseases Diagnosis-Applied Exosomes
• Allograft Rejection Detection-Applied Exosomes in Organ Transplantation
• Renal Disease Diagnosis-Applied Exosomes
• Lung Disease Diagnosis-Applied Exosomes
• Liver Disease Diagnosis-Applied Exosomes
• Neurological Diseases Diagnosis-Applied Exosomes
• Virus Infections Diagnosis-Applied Exosomes
• Parasitic Infections Diagnosis-Applied Exosomes

Fig.1 Biogenesis, secretion, composition, and application of exosomes as liquid biopsy. (Zhou, 2020)

Procedures for Diagnosis at Creative Biolabs

The general procedure for exosome diagnosis at Creative Biolabs is divided into the following key steps:

• Exosome exosome isolation and purification from biofluidic samples. At Creative Biolabs, various sample sources are available for exosome isolation, including cell cultures, plasma, serum, urine, cerebrospinal fluid, saliva, ascites, follicular fluid, and breast milk. We offer a wide selection of methods for exosome isolation and purification by ultracentrifugation, size-exclusion chromatography, tangential flow filtration, affinity-based capture, and combinations of the above methods.
• Exosome contents extraction and profiling. Creative Biolabs has established a comprehensive platform for exosome content profiling. For exosomal RNA sequencing, Creative Biolabs has equipped several powerful technologies including PCR, qPCR, and NGS. With these technologies, we offer a wide range of exosomal RNA analysis services, including whole transcriptome sequencing and miRNA sequencing. Exosomal proteomic analysis is performed by mass spectrometry to identify and analyze exosomal protein composition data. Chemical isotope labeling and nLC-MS-based technologies are available for exosomal lipidomics and metabolomics analysis services.

Fig.2 Schematic representation detailing the discovery of biomarkers from exosomes. (Elkommos-Zakhary, 2022)

As a significant biomarker for liquid biopsy for screening and diagnosis of diverse diseases, exosomes play an indispensable guiding role in the future of clinical oncology. Drawing on the multiple active cargoes carried by exosomes that can be used as liquid biopsy biomarker candidates, Creative Biolabs provides exosome marker discovery services in diagnostic applications and comprehensive research analysis services, including exosome isolation, profiling, and sequencing, improving the research of disease prognosis and diagnosis. Please feel free to contact us if you are interested in our services.

References

1. Zhou, B.; et al. Application of exosomes as liquid biopsy in clinical diagnosis. Signal Transduct Target Ther. 2020, 5(1): 144.
2. Elkommos-Zakhary, M.; et al. Exosome RNA sequencing as a tool in the search for cancer biomarkers. Noncoding RNA. 2022, 8(6): 75.

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