The molecular logic of insulin resistance begins at the cell membrane. When insulin binds its receptor, a signalling cascade follows: insulin receptor substrates are tyrosine-phosphorylated, the PI3K/Akt pathway is activated, and the glucose transporter GLUT4 moves to the cell surface to import glucose. In resistant tissues, this cascade is sabotaged. Stress kinases such as JNK and PKC drive excessive serine phosphorylation of insulin receptor substrates, blunting the signal, while negative regulators like PTEN and SOCS proteins and inflammatory cytokines such as TNF-alpha and IL-6 further suppress the pathway. Meanwhile, diacylglycerols and ceramides accumulate in non-adipose tissues, creating a lipotoxic environment that fuels endoplasmic reticulum stress and oxidative damage. In adipose tissue, macrophages polarize toward a pro-inflammatory M1 state, adiponectin secretion falls, and leptin and resistin rise, amplifying systemic resistance.

What makes the review’s argument distinctive is its emphasis on mitochondria as central players rather than bystanders. Mitochondria govern substrate oxidation, ATP synthesis, and reactive oxygen species homeostasis, and in insulin-resistant skeletal muscle their oxidative capacity consistently declines. Impaired fatty acid oxidation allows partially oxidized lipid intermediates to build up, and these metabolites actively sabotage insulin signalling through PKC and JNK activation. In the liver, mitochondrial dysfunction promotes pathological gluconeogenesis and fat accumulation, while in pancreatic beta cells it accelerates stress-induced apoptosis. The review describes a self-reinforcing loop in which disrupted fusion and fission dynamics, stalled mitophagy, and downregulated biogenesis through the PGC-1alpha/NRF1/TFAM axis drive ROS overproduction and ATP depletion, deepening signalling defects and eventually precipitating beta-cell failure.

Against this backdrop, mesenchymal stem cell-derived exosomes have emerged as a compelling cell-free therapeutic platform. These membrane-bound nanovesicles, roughly 30 to 150 nanometres across, are generated through the endosomal pathway and carry a heterogeneous cargo of microRNAs, long non-coding RNAs, proteins, lipids, and metabolites. They display characteristic surface markers such as the tetraspanins CD9, CD63, and CD81 along with TSG101 and ALIX, and their cholesterol- and sphingomyelin-rich membrane supports vesicle stability. Once taken up by recipient cells through endocytosis or membrane fusion, this cargo can reprogramme gene expression and cellular behaviour. Crucially, compared with transplanting whole stem cells, exosomes carry negligible risk of tumorigenicity or ectopic differentiation, provoke low immunogenicity, can be stored and standardized as off-the-shelf biologics, and can cross barriers as formidable as the blood-brain barrier.

The preclinical evidence base is growing rapidly. Exosomes from human umbilical cord mesenchymal stem cells administered to diabetic rats increased GLUT4 translocation, lowered HbA1c, and improved glucose uptake, while in insulin-resistant human adipocytes they restored glucose uptake by upregulating SIRT1 and IRS1 and normalizing adipokine profiles, decreasing leptin and raising adiponectin. Bone marrow-derived exosomes activated the PI3K/Akt pathway, increased GLUT4 expression, and shifted adipose tissue macrophages toward an anti-inflammatory M2 phenotype in diet-induced obese mice. Wharton’s jelly-derived exosomes alleviated hepatic steatosis by activating the FGF21/adiponectin axis, reducing endoplasmic reticulum stress, and enhancing mitochondrial fatty acid oxidation. Other studies showed reduced beta-cell apoptosis and improved insulin secretion in diabetic rat models. The review is candid, however, that most of these findings come from short-term rodent studies with small sample sizes and considerable heterogeneity in exosome sources, isolation methods, and dosing.

The microRNA cargo is where the therapeutic precision lies. These roughly 22-nucleotide non-coding RNAs fine-tune gene expression post-transcriptionally, and several are deeply implicated in insulin resistance. The review highlights miR-29b-3p as a cautionary tale: exosomes from aged bone marrow stem cells are enriched in this microRNA, which targets SIRT1 and actively promotes metabolic dysfunction, and inhibiting it rescues insulin sensitivity, implicating it in age-related resistance. By contrast, miR-21 protects pancreatic beta cells under hypoxic and inflammatory stress by suppressing pro-apoptotic pathways involving p38 MAPK, PDCD4, and FasL, while miR-146a dampens NF-kappaB signalling and reduces secretion of TNF-alpha, IL-6, and IL-1beta. An insulin-sensitizing microRNA called miR-3075, enriched in hepatocyte-derived exosomes during early-stage obesity, enhances insulin sensitivity by targeting fatty acid 2-hydroxylase, though this compensatory mechanism is lost in chronic obesity.

This is precisely where genetic engineering enters the picture. Rather than relying on whatever cargo native exosomes happen to carry, researchers can reprogramme the parent stem cells using lentiviral transfection or electroporation, enriching the resulting vesicles with protective microRNAs while silencing harmful ones such as miR-29b-3p through antagonists, siRNAs, or CRISPR interference. Bicistronic and multi-cistronic vectors built with internal ribosome entry sites or 2A self-cleaving peptides allow a single exosome to carry combinations such as miR-21, miR-146a, and SIRT3, a mitochondrial deacetylase that enhances respiratory chain function, curbs ROS production, and promotes PGC-1alpha-mediated biogenesis via SOD2. Dual-engineered exosomes co-loading SIRT3 with insulin-mimetic domains have already shown superior mitochondrial protection in myocardial ischemia-reperfusion models, and analogous strategies could, in principle, reverse the bioenergetic deficits that characterize insulin-resistant muscle, liver, and islets.

Targeting is the other half of the engineering challenge. Because insulin resistance is a systemic, multi-organ disease, exosomes must reach skeletal muscle, adipose tissue, the liver, and pancreatic islets simultaneously, yet biodistribution studies show that systemically injected vesicles are rapidly cleared by the liver and spleen. Surface functionalization offers partial answers: polyethylene glycol prolongs circulation, while conjugated homing peptides, aptamers, and antibodies steer vesicles toward specific organs. The review cites examples including dual-engineered vesicles co-expressing CXCR4 and a P-selectin-binding peptide for tissue-specific homing, aptamer-functionalized exosomes that suppressed allergic airway inflammation in mice, and an ASGR1-targeting platform designed to home to hepatocytes for fatty liver disease. Aptamer- and PEG-modified exosomes have shown superior islet protection compared with unmodified vesicles, combining prolonged circulation with precise beta-cell delivery.

Substantial hurdles remain before any of this reaches patients. Manufacturing is a bottleneck: ultracentrifugation, tangential flow filtration, and size-exclusion chromatography each compromise reproducibility, and genetic modification adds variability in transfection efficiency and cargo loading. Viral vectors raise concerns about insertional mutagenesis and long-term oncogenic potential, while the long-term safety of repeated dosing and of overexpressed agents like SIRT3 is untested. Mechanistically, much of the evidence remains correlative, and direct transfer of intact mitochondria via exosomes is still debated, with most data favouring miRNA- and protein-mediated regulation instead. As of 2025, exosome therapies have entered early-phase trials mainly for wound healing, graft-versus-host disease, and diabetic complications, but no large-scale trial has yet targeted systemic insulin resistance.

Even so, the conceptual shift the review describes is hard to ignore. Conventional drugs such as metformin and thiazolidinediones modestly improve insulin sensitivity but cannot simultaneously correct impaired signalling, chronic inflammation, ectopic lipid burden, and mitochondrial dysfunction. Gene-modified exosomes, by contrast, are designed to do all of these things in one particle, coordinating signalling restoration, inflammatory repolarization, beta-cell preservation, and mitochondrial rescue. If the field can solve scalable good-manufacturing-practice production, achieve durable multi-organ targeting, and validate safety in large animal models, these engineered nanovesicles could move from experimental tools to genuine disease-modifying therapies, transforming the treatment of insulin resistance from symptom management into root-cause repair.

Subject of Research: Gene-modified mesenchymal stem cell-derived exosomes as a therapeutic strategy for insulin resistance

Article Title: Therapeutic Potential of Gene‐Modified MSC‐Exos in Insulin Resistance: Mitochondrial Crosstalk and miRNA Regulation

Article References: Jia, Q., Li, B., Xing, Y., Zhang, Y., Gao, B., Li, X., & Ha, X. (2026). Therapeutic Potential of Gene‐Modified MSC ‐Exos in Insulin Resistance: Mitochondrial Crosstalk and miRNA Regulation. Journal of Cellular and Molecular Medicine, 30(17), Article e71342. https://doi.org/10.1111/jcmm.71342

Image Credits: AI Generated

DOI: 10.1111/jcmm.71342

Keywords: insulin resistance, MSC-derived exosomes, mesenchymal stem cells, miRNA, mitochondrial dysfunction, type 2 diabetes, SIRT3, gene engineering, exosome therapy, metabolic disease, inflammation, pancreatic beta cells

The core idea is deceptively simple. Natural T cells do not rely on their antigen receptor alone; they depend on co-stimulatory receptors such as CD28 and ICOS, the inducible T cell co-stimulator, to fine-tune activation, survival and differentiation. The researchers reasoned that if a therapeutic T cell receptor could be fused directly to a co-stimulatory signaling domain, every encounter with a tumor cell would deliver not just a recognition signal but a survival and persistence signal at the same time. The construct they engineered, which they call TCR:ICOS, combines the extracellular variable and constant domains of a conventional T cell receptor with a CD28 transmembrane segment and intracellular domains drawn from both ICOS and CD3 epsilon. The result is a single hybrid receptor that couples antigen specificity to co-stimulation in one molecular unit.

The functional consequences in mice were dramatic. T cells carrying the TCR:ICOS receptor showed enhanced, antigen-specific production of inflammatory cytokines, the chemical weapons that help recruit and coordinate an immune attack. More importantly, the cells persisted far longer within tumors than their conventional counterparts, and this persistence translated into clinical outcomes: delayed recurrence of melanoma and, in a subset of animals, complete and durable cures. For a field in which the transience of engineered T cells is a central bottleneck, the demonstration that a receptor-level modification can extend the working lifespan of the cells inside a hostile tumor microenvironment is a significant proof of concept.

Beneath the phenotypic changes lies a defined signaling logic. The team found that TCR:ICOS activation engaged two major pathways, PI3K and NF-kappa B, while paradoxically restraining the activation of AKT, a kinase downstream of PI3K that is often associated with terminal differentiation and metabolic burnout in T cells. This combination appears to be the key to the durability. Sustained PI3K and NF-kappa B signaling supports inflammatory function and survival, while blunted AKT activity helps the cells avoid the hyperactive, exhausted state that typically shortens the life of tumor-infiltrating lymphocytes. When the researchers genetically ablated the ICOS-PI3K pathway, the long-term anti-tumor effects disappeared, confirming that this signaling axis is not a side effect but the mechanistic engine of the durable response.

Single-cell level analysis reinforced the picture of a fundamentally altered differentiation program. TCR:ICOS T cells were enriched for a stem-like state, a less differentiated, self-renewing condition that immunologists regard as the hallmark of long-lived, re-challenge-capable T cell populations. They also showed resistance to exhaustion, the progressive loss of function marked by inhibitory receptors such as PD1, LAG3 and TIM3 that plagues conventional tumor-infiltrating cells. In practical terms, the engineered cells behaved less like short-lived commandos and more like a renewable garrison, capable of maintaining pressure on the tumor over time rather than expending themselves in a single burst of activity.

Translating the concept from mouse to human T cells required an additional round of molecular engineering. Early versions of the hybrid receptor did not express efficiently on the surface of human cells, a common obstacle in receptor design where folding, assembly and trafficking can fail silently. The team solved this by identifying a single amino acid change in the cytosolic tail of the receptor that enabled functional surface expression. Crucially, the optimized receptor avoided two well-known hazards of introducing engineered T cell receptors into patient cells: mispairing with endogenous TCR chains, which can create unpredictable and potentially dangerous specificities, and competition for limited CD3 molecules, which can impair the function of the T cell’s native receptor complex.

The human-cell experiments went beyond a single antigen. The researchers showed that the optimized TCR:ICOS format sustained the functional performance of human T cells across repeated stimulation cycles and could be extended to multiple tumor antigens, including targets relevant to solid cancers such as NY-ESO-1 and ROPN1, without eroding T cell fitness. This uniform applicability matters for the field. Many receptor-engineering advances are idiosyncratic, working for one TCR or one antigen but failing when generalized. A format that preserves T cell quality across different specificities offers a modular platform: any tumor-reactive TCR could, in principle, be equipped with the same built-in co-stimulation and inherit the same durability advantages.

The findings arrive at a moment when the cell therapy field is intensely focused on next-generation designs. Chimeric antigen receptors, or CARs, already incorporate co-stimulatory domains such as CD28 or 4-1BB, and that choice profoundly shapes how CAR T cells persist and differentiate. TCR-based therapies, which can recognize intracellular tumor antigens presented by HLA molecules and therefore access a much larger pool of cancer targets, have lacked an equivalent, systematic way to embed co-stimulation. The TCR:ICOS design fills that gap, and its mechanism, favoring stem-like persistence through PI3K and NF-kappa B while restraining AKT, offers a template that other groups can rationally modify.

There are, of course, steps between a mouse melanoma model and approved therapy. The study was conducted in preclinical systems, and human trials will need to establish safety, particularly given that engineered co-stimulation could, in principle, amplify off-tumor reactivity if a TCR recognizes healthy tissue. Dosing, manufacturing consistency and the behavior of TCR:ICOS cells in the complex, immunosuppressive environment of human solid tumors all remain to be tested. The authors note that the work was supported by the Dutch Cancer Society and a Health Holland public-private partnership, and several team members report pending patents related to the receptor design, signaling commercial interest in bringing the platform toward clinical evaluation.

Even so, the study offers a compelling answer to one of adoptive cell therapy’s most persistent questions: how to make engineered T cells last. By fusing recognition and co-stimulation into a single receptor, the Rotterdam team has shown that durability can be designed into the therapeutic product itself rather than bolted on with cytokines, checkpoint blockade or lymphodepleting chemotherapy. If the format performs in human trials as it has in mice, TCR:ICOS could become a foundational component of fitter, longer-lived T cell products for solid tumors, turning a transient spark of immune attack into a sustained campaign against cancer.

Subject of Research: Engineering T cell receptors with built-in ICOS co-stimulation to extend the durability of adoptive T cell therapy against solid tumors

Article Title: T cell receptors equipped with ICOS provide T cells with durable anti-tumor response

Article References: Marraffa, A., Berrevoets, C., Mosiello, M., Coelho, R. M., Roelofs, D., van Brakel, M., Wijers, R., Kroese, K., Peeters, M. J., Dik, W. A., Kunert, A., Abbott, R. J., Hammerl, D., Schliehe, C., & Debets, R. (2026). T cell receptors equipped with ICOS provide T cells with durable anti-tumor response. Molecular Cancer, 25(1), Article 216. https://doi.org/10.1186/s12943-026-02765-9

Image Credits: AI Generated

DOI: 10.1186/s12943-026-02765-9

Keywords: adoptive T cell therapy, T cell receptor, ICOS, co-stimulation, T cell exhaustion, solid tumors, melanoma, PI3K signaling, NF-kappa B, stem-like T cells, gene engineering, Molecular Cancer