Charged-Up Exosomes From Energy-Boosted Cells Heal Stubborn Diabetic Wounds

Chronic diabetic wounds are among the most stubborn failures of modern medicine. Roughly a quarter of people with diabetes will develop a diabetic wound during their lifetime, and when healing stalls, the consequences can be catastrophic: persistent infection, tissue death and, in the worst cases, amputation. The root of the problem is twofold. Blood vessels fail to regenerate properly, starving the wound of oxygen and nutrients, while the immune system becomes locked in a destructive, pro-inflammatory state that never resolves. Now, a team of researchers writing in Materials Today Bio reports a strategy that attacks both problems at once, using a small metabolic molecule to supercharge endothelial cells so that they release healing exosomes capable of reprogramming macrophages.

The molecule at the heart of the study is AICAR, a well-known activator of AMPK, an enzyme often described as the cell’s central metabolic switch. When the researchers treated human umbilical vein endothelial cells with AICAR under inflammatory conditions designed to mimic the diabetic wound environment, AMPK phosphorylation rose more than threefold. The effects cascaded through the cells’ mitochondria: transmission electron microscopy showed preserved mitochondrial ultrastructure instead of the swelling and shrinkage seen in untreated controls, respiratory-chain complexes I through V became more active, and ATP production roughly doubled. Mitochondrial membrane potential increased, mitochondrial mass expanded, and levels of damaging mitochondrial superoxide fell.

Metabolic readouts confirmed that AICAR had shifted endothelial cells into a genuinely high-energy state. The NAD+/NADH ratio rose while the lactate/pyruvate ratio fell, both changes pointing toward enhanced oxidative phosphorylation and suppressed glycolysis. Critically, these effects disappeared when the cells were co-treated with Compound C, an AMPK inhibitor, establishing that the metabolic transformation was AMPK-dependent. Energized endothelial cells also became better builders of blood vessels: they produced more VEGF, migrated faster across scratch wounds, formed more extensive tube networks on Matrigel, and stimulated denser vessel growth in the chick chorioallantoic membrane assay.

But the most striking discovery came from the cells’ secretions. Exosomes, nanosized vesicles that ferry proteins and genetic material between cells, are increasingly recognized as key mediators of intercellular communication in tissue repair. When the team isolated exosomes from AICAR-treated endothelial cells, dubbed AI-EXO, they found that AICAR stimulation increased exosome yield roughly threefold and boosted bioactive protein content 2.2-fold compared with exosomes from untreated cells. Mass spectrometry confirmed that no residual AICAR was encapsulated inside the vesicles, meaning their biological activity came entirely from their own cargo.

Proteomic profiling of AI-EXO revealed a distinct molecular signature, with growth arrest-specific protein 6, or GAS6, standing out among the most significantly upregulated proteins. GAS6 is a secreted ligand with well-documented anti-inflammatory and tissue-protective effects, and it signals through MER, a receptor of the TAM family expressed on macrophages. The researchers hypothesized that AI-EXO might use GAS6 to push macrophages out of their destructive pro-inflammatory M1 state and into the pro-healing M2 state, a transition that is notoriously impaired in diabetes.

The evidence was compelling. When inflammatory M1 macrophages were treated with AI-EXO, the proportion of iNOS-positive M1 cells plummeted to 4.8 percent while Arg-1-positive M2 cells surged to 41.3 percent, yielding an M2-to-M1 ratio of about 8.60, compared with roughly 0.30 in controls. To prove GAS6 was the culprit, the team silenced the GAS6 gene in endothelial cells before AICAR treatment; the resulting exosomes lost nearly all of their reprogramming power. Adding recombinant GAS6 back restored the effect, and blocking either MER or its downstream target AKT with pharmacological inhibitors likewise abolished the M1-to-M2 shift. A GAS6-neutralizing antibody provided independent confirmation that the vesicles’ immunomodulatory function depends specifically on this protein.

With the mechanism established in vitro, the researchers built a delivery system to translate it into living wounds. Using melt electrospinning writing, a high-precision 3D printing technique, they fabricated porous polycaprolactone scaffolds coated with a GelMA hydrogel loaded with AICAR, creating a patch designated MEWs + GelMA@AI. The scaffold released AICAR sustainably for approximately 15 days, and its compressive modulus of about 217 kilopascals provided mechanical stability without excessive stiffness. Endothelial cells cultured on the patch under inflammatory conditions showed a survival rate of nearly 95 percent, well above the 78 percent seen on plain scaffolds, and attached in far greater numbers.

The real test came in diabetic rats, whose diabetes was induced with streptozotocin and a high-sugar, high-fat diet. Full-thickness wounds treated with the AICAR-loaded patch closed significantly faster than wounds in all control groups, including those receiving systemic AICAR injections. Histology told the story beneath the surface: less inflammatory-cell infiltration, denser collagen deposition on Masson’s trichrome staining, and markedly increased CD31-positive neovascularization. Immunofluorescence of wound tissue on day 14 showed the same macrophage shift seen in the dish, with more F4/80-positive Arg-1-positive M2 cells and fewer F4/80-positive iNOS-positive M1 cells. When the researchers added a MER inhibitor to the patch, these benefits largely vanished, confirming that the GAS6/MER/AKT pathway drives the healing response in vivo.

Safety data were reassuring. Fasting blood glucose and body weight showed no significant differences between groups, indicating that neither local nor systemic AICAR delivery disturbed systemic metabolism. Histological examination of major organs revealed no abnormalities, and the patch actually lowered local glucose concentrations within the wound tissue, partially reversing the hyperglycemic microenvironment that sabotages repair. The authors note important caveats, however: the streptozotocin rat model does not fully capture the comorbidities, infection and neuropathy of human diabetic ulcers, the in vitro work relied on immortalized cell lines, and the isolated exosome preparations contain a heterogeneous mix of vesicle subtypes whose individual contributions remain to be disentangled.

Even so, the study represents a notable conceptual advance. It is the first work to identify the GAS6/MER/AKT axis as the link between the metabolic state of endothelial cells and macrophage reprogramming in chronic wounds, framing tissue repair as an immunometabolic conversation between cell types. By pairing a metabolism-centered intervention with a biodegradable scaffold that releases its payload over weeks, the researchers offer a template for dual-targeted wound therapy, one that simultaneously rebuilds vasculature and recalibrates immunity. For the millions of patients whose wounds refuse to heal, that combination of vascular and immune repair, delivered from a single patch, could eventually change the trajectory of diabetic wound care.

Subject of Research: AICAR-loaded scaffolds promoting diabetic wound healing through endothelial energy metabolism, exosomal GAS6 signaling and macrophage reprogramming

Article Title: AICAR-induced energy supply and paracrine activity of endothelial cells accelerate chronic diabetic wound healing by promoting angiogenesis and modulating macrophage reprogramming

Article References: Su, H., Liu, C., Cheng, Y., Cheng, W., Xu, A., Hu, D., Shi, H., Huang, M., Yuan, H., Huang, C., Huang, Y., Su, S., Duan, C., & Feng, X. (2026). AICAR-induced energy supply and paracrine activity of endothelial cells accelerate chronic diabetic wound healing by promoting angiogenesis and modulating macrophage reprogramming. Materials Today Bio, 41, Article 103743. https://doi.org/10.1016/j.mtbio.2026.103743

Image Credits: AI Generated

DOI: 10.1016/j.mtbio.2026.103743

Keywords: diabetic wounds, AICAR, AMPK, exosomes, GAS6, macrophage polarization, angiogenesis, MER/AKT signaling, GelMA hydrogel, melt electrospinning, tissue engineering, immunometabolism