The review traces the technical foundations that made this transformation possible. Early mRNA research was long hampered by the molecule’s inherent instability, inefficient delivery into cells, and unwanted activation of innate immune defenses that suppressed protein production. Two breakthroughs changed the trajectory. The incorporation of modified nucleosides, particularly pseudouridine and N1-methyl-pseudouridine, dampened recognition by innate immune sensors such as Toll-like receptors and the cytosolic RNA sensors RIG-I and MDA5, while simultaneously enhancing translational efficiency. In parallel, lipid nanoparticle (LNP) delivery systems solved the problem of getting fragile, negatively charged RNA molecules across cell membranes and into the cytoplasm, where ribosomes can translate them into protein.

The architecture of a synthetic mRNA construct is itself a feat of rational engineering. Each transcript carries a 7-methylguanosine cap that protects against degradation and recruits the translation machinery, optimized untranslated regions that tune stability and expression kinetics, a codon-adapted open reading frame encoding the antigen or therapeutic protein of interest, and a poly(A) tail of roughly 100 to 150 adenine residues that promotes mRNA circularization and sustained protein output. Cap analogs such as anti-reverse cap analogs and CleanCap technologies, UTR sequences borrowed from highly expressed genes like globin, and chromatographic purification to remove double-stranded RNA contaminants all contribute to potency and safety. Because mRNA operates in the cytoplasm and never enters the nucleus, expression is transient and non-integrating, a pharmacological profile that distinguishes mRNA from permanent gene-editing approaches.

Delivery remains the field’s central bottleneck, and the review devotes detailed attention to it. LNPs, typically composed of ionizable lipids, helper phospholipids, cholesterol, and PEG-lipids, remain the most clinically advanced carriers. Ionizable lipids stay neutral in the bloodstream but become protonated in the acidic endosome, destabilizing the endosomal membrane and releasing mRNA into the cytosol. Polymeric nanoparticles built from materials such as PLGA offer tunable, biodegradable alternatives, though cytotoxicity and lower transfection efficiency persist. Viral and virus-like particle systems deliver RNA efficiently but raise immunogenicity and regulatory concerns, prompting interest in hybrid platforms. The next frontier is targeting: ligand-decorated nanoparticles and organ-selective lipid compositions are being engineered to direct mRNA to the lungs, heart, spleen, immune cells, and, ultimately, the brain, rather than defaulting to liver accumulation.

Once delivered, mRNA therapeutics work through a coordinated immunological sequence. Antigen-presenting cells such as dendritic cells internalize the nanoparticles, the mRNA is translated into antigenic protein, and that protein is processed and displayed on MHC class I and class II molecules, activating CD8-positive cytotoxic T cells and CD4-positive helper T cells respectively. B cells are stimulated to produce antibodies, while innate sensing of the RNA itself acts as a built-in adjuvant. The review also categorizes three platform generations: conventional non-replicating mRNA, the clinically validated workhorse; self-amplifying RNA derived from alphavirus replicases, which promises high expression at low doses but poses delivery and reactogenicity challenges; and circular RNA, whose covalently closed loop resists exonuclease degradation and supports prolonged, cap-independent translation through IRES or m6A-mediated initiation.

Oncology is where the therapeutic expansion is most advanced. Early mRNA cancer vaccines targeted tumor-associated antigens, shared proteins overexpressed in malignancies but limited by immune tolerance. The field has since pivoted toward neoantigens, mutated peptides generated by tumor-specific somatic mutations that the immune system recognizes as foreign. Personalized mRNA vaccines now pair next-generation tumor sequencing with bioinformatic neoepitope prediction, allowing multiple patient-specific targets to be encoded in a single construct manufactured on compressed timelines. Programs in melanoma, lung, colorectal, and pancreatic cancer are increasingly combining these vaccines with checkpoint inhibitors targeting PD-1, PD-L1, or CTLA-4, on the logic that vaccines expand tumor-specific T cells while checkpoint blockade reverses tumor-induced exhaustion.

Beyond cancer, the review highlights a striking inversion of vaccine logic: tolerogenic mRNA. In autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, and lupus, mRNA constructs encoding disease-relevant autoantigens can be delivered in a non-inflammatory context to promote regulatory T cells and suppress autoreactivity without global immunosuppression. In protein replacement therapy, mRNA encoding missing enzymes, clotting factors, or transport proteins offers repeat-dose treatment for hemophilia, lysosomal storage diseases, and metabolic disorders without genomic integration. The review cautions, however, that patients with genetic deficiencies may lack tolerance to the newly synthesized protein, creating risks of anti-drug antibodies; strategies such as modified nucleosides, low intermittent dosing, and tissue-restricted expression are proposed to mitigate this. Cardiovascular applications include VEGF mRNA to stimulate angiogenesis after ischemic injury, while neurological applications confront the formidable barrier of the blood-brain barrier through receptor-mediated transport, intrathecal delivery, and engineered nanoparticles.

Clinical translation is accelerating but uneven. Preclinical animal studies have demonstrated that liver-directed mRNA can correct biochemical abnormalities in metabolic disease models, that neoantigen vaccines can delay tumor growth, and that localized VEGF expression improves perfusion after ischemia. Companies including Moderna, BioNTech, CureVac, and Arcturus Therapeutics are advancing pipelines spanning personalized oncology, rare disease protein replacement, and self-amplifying RNA platforms, with trial designs increasingly incorporating adaptive protocols, biomarker-driven enrollment, and combination regimens. Regulatory science is adapting in parallel, grappling with products that combine features of biologics, nucleic acid medicines, and nanotechnology, and with manufacturing quality attributes ranging from double-stranded RNA impurity levels to nanoparticle size distribution and batch comparability.

Significant obstacles temper the enthusiasm. Many mRNA products still require cold-chain storage that strains logistics in low-resource settings, prompting work on thermostable and lyophilized formulations. Reactogenicity, complement activation, and anti-carrier immune responses complicate repeated dosing, while off-target innate activation can suppress translation in non-vaccine applications. Costs are high, particularly for personalized cancer vaccines requiring rapid custom manufacturing, and global manufacturing capacity remains concentrated in a handful of countries, raising the prospect that therapeutic inequities could extend beyond pandemics into chronic disease care. Looking forward, the review identifies artificial intelligence as a key accelerator, with machine learning models improving neoantigen prediction, codon and UTR optimization, and lipid discovery, and envisions an integrated ecosystem in which genomic profiling, AI-guided sequence design, automated manufacturing, and real-world biomarker data converge into a rapid-response therapeutic platform. If delivery science and equitable access keep pace, the authors argue, mRNA may evolve from a pandemic-era vaccine technology into a foundational pillar of programmable, personalized medicine.

Subject of Research: Expanding therapeutic applications of mRNA technology beyond infectious disease vaccines

Article Title: mRNA Therapeutics Beyond Infectious Diseases: Expanding Therapeutic Applications and Future Perspectives

Article References: Dejen, G. M. (2026). mRNA Therapeutics Beyond Infectious Diseases: Expanding Therapeutic Applications and Future Perspectives. Immunity, Inflammation and Disease, 14(9), Article e70511. https://doi.org/10.1002/iid3.70511

Image Credits: AI Generated

DOI: 10.1002/iid3.70511

Keywords: mRNA therapeutics, lipid nanoparticles, cancer vaccines, neoantigens, protein replacement therapy, autoimmune disease, self-amplifying RNA, circular RNA, drug delivery, personalized medicine, regenerative medicine, blood-brain barrier

Osteoarthritis, the most common form of arthritis affecting millions worldwide, is characterized by the progressive degradation of cartilage and joint tissues, leading to pain, stiffness, and impaired mobility. Conventional treatments primarily aim to manage symptoms rather than to halt or reverse disease progression. The advent of circRNA-based therapeutics offers a tantalizing avenue by enabling endogenous protein expression in affected tissues, thereby directly addressing the molecular deficiencies underlying the pathology.

The research team, spearheaded by Suo, Li, Tan, and colleagues, designed an innovative circRNA construct encoding a therapeutic protein critical for cartilage homeostasis. Their approach capitalizes on the intrinsic stability and translational capacity of circRNAs, which differ fundamentally from linear messenger RNAs due to their covalently closed loop structure, imparting resistance to exonucleases and enhancing persistence within cells. This stability translates into prolonged protein expression, a coveted feature for therapeutic efficacy.

To assess the translational potential of their circRNA platform, the scientists employed a well-established osteoarthritis model in male mice. By intra-articularly delivering the circRNA formulation directly into the affected joints, they ensured localized expression, minimizing off-target effects and systemic exposure. Advanced delivery vectors encapsulated in lipid nanoparticles likely facilitated efficient cellular uptake and circRNA release, although specifics were methodically optimized to maximize bioavailability and minimize immunogenicity.

The results were remarkable. Mice treated with circRNA-based replacement therapy exhibited significant attenuation of cartilage degradation, reduced inflammatory markers, and restoration of joint function compared to untreated controls. Histological analyses confirmed the preservation of cartilage architecture, and behavioral assays underscored improvements in mobility and pain-related responses. These outcomes testify to the potential of circRNA therapeutics to not only satiate protein deficits but also modulate the intricate cellular milieu that governs tissue repair and inflammation.

Beyond the immediate therapeutic benefits, this study illuminates the advantages of circRNA over other nucleic acid-based modalities. Unlike linear mRNAs used in various vaccines and experimental therapies, circRNAs evade rapid degradation and possess an inherent translational advantage, which could translate into lower dosing requirements and reduced side effect profiles. Their biocompatibility and scalability further enhance their clinical appeal, fostering enthusiasm for extensive preclinical and eventual clinical evaluations.

One of the compelling facets of this research is the team’s detailed mechanistic exploration. By employing transcriptomic and proteomic analyses, they demonstrated that the circRNA-mediated protein replacement reinstated key signaling pathways disrupted in osteoarthritic joints. These pathways include anabolic signals promoting cartilage synthesis and catabolic cascades associated with matrix degradation. The capacity of circRNA therapeutics to reprogram diseased tissue environments by restoring molecular balance underscores their versatility.

While the immediate focus was on osteoarthritis, the implications of this work extend far beyond degenerative joint diseases. Protein replacement therapy via circRNA could revolutionize treatments for a swath of disorders typified by protein insufficiencies, such as certain enzyme deficiencies, neurodegenerative diseases, and muscular dystrophies. The modularity of circRNA design facilitates the customization of therapeutic proteins, enabling tailored interventions for a diversity of clinical phenotypes.

Despite the promising outcomes, the authors acknowledged several challenges that must be addressed before circRNA therapies can reach clinical settings. Immunogenicity remains a critical consideration, given that exogenous RNA species may elicit innate immune responses. The study carefully evaluated potential cytotoxic and inflammatory effects, finding minimal adverse reactions, yet long-term safety profiles necessitate comprehensive assessment. Additionally, translating dosage paradigms from murine models to humans requires nuanced pharmacokinetic and pharmacodynamic studies.

The delivery vehicles used to ferry circRNAs into tissues also warrant optimization. Lipid nanoparticles showed efficacy in this experimental context, but their biodistribution, metabolism, and clearance must be finely controlled to avoid unintended accumulation or off-target effects. Emerging nanotechnologies and surface modifications may enhance specificity and cellular targeting, broadening the therapeutic index of circRNA interventions.

As the field advances, the integration of circRNA platforms with regenerative medicine and biomaterials holds exciting promise. For instance, combining circRNA therapeutics with hydrogel scaffolds or injectable biomatrices could offer sustained localized delivery, augmenting cartilage regeneration and functional restoration. This multidisciplinary convergence stands to amplify therapeutic durability and patient outcomes.

Furthermore, the scalability and manufacturing ease of circRNA vaccines and therapies have been bolstered by recent biotechnological breakthroughs. The robust in vitro transcription protocols and enzymatic circularization methods now permit high-fidelity synthesis of clinical-grade circRNAs, compounding the practicality of rapid therapeutic development, especially in response to emergent diseases or individualized medicine paradigms.

The profound implications of this study resonate across the biomedical landscape. By harnessing the unique properties of circRNAs for protein replacement, the research embodies the paradigm shift toward RNA therapeutics extending beyond transient gene knockdown or vaccine platforms, venturing into durable protein restoration with therapeutic impact. This capacity may recalibrate treatment frameworks for chronic diseases, moving from symptomatic management to molecular correction.

As more research groups engage with circRNA biology, understanding their interactions with cellular machinery, including ribosomes, nucleases, and immune sensors, will refine therapeutic design. The interplay between circRNA modifications, secondary structures, and translation efficiency presents fertile ground for innovation, aiming to optimize expression while mitigating risks.

In summary, Suo and colleagues have charted a transformative trajectory for osteoarthritis treatment through circRNA-based protein replacement therapy. Their meticulous experimentation substantiates the viability of this approach in mitigating joint degeneration and functional decline, hinting at broader applications for circRNA therapeutics. As clinical translation progresses, these insights offer hope for millions affected by osteoarthritis and related disorders, heralding a new chapter in RNA medicine.

This research not only enhances our molecular toolkit but also exemplifies the synergy between fundamental RNA biology and clinical ambition, inspiring continued exploration into circRNA’s therapeutic potential. The journey from bench to bedside may be complex, yet the promise of durable, target-specific, and minimally invasive treatments invigorates the quest for next-generation therapies grounded in RNA innovation.

Subject of Research: Circular RNA-based protein replacement therapy for osteoarthritis treatment

Article Title: Circular RNA-based protein replacement therapy mitigates osteoarthritis in male mice

Article References:
Suo, J., Li, L., Tan, W. et al. Circular RNA-based protein replacement therapy mitigates osteoarthritis in male mice. Nat Commun 16, 8480 (2025). https://doi.org/10.1038/s41467-025-63343-z

Image Credits: AI Generated