Sticky Gel Carrying Supercharged Stem Cell Vesicles Repairs Burned Esophagus in Rats

When a child or adult accidentally swallows a corrosive household chemical, the consequences can be devastating. The caustic substance strips away the lining of the esophagus, triggering a cascade of inflammation, tissue death, and ultimately scarring that narrows the swallowing tube into a rigid, dysfunctional channel. According to pooled clinical data cited by the researchers, corrosive esophageal injury carries a mortality rate of 6.2 percent and leads to stricture formation in nearly a quarter of adult patients. Current treatments, ranging from repeated endoscopic dilations to major surgical reconstruction, are invasive, often ineffective, and carry serious risks including perforation, anastomotic leakage, and long-term complications in children such as malnutrition and impaired growth. A new study published in Materials Today Bio offers a radically different approach: a bioadhesive gel loaded with functionally enhanced stem cell-derived vesicles that, in rat experiments, suppressed inflammation, curbed oxidative stress, and dramatically reduced the fibrotic scarring that makes these injuries so dangerous.

The therapeutic platform, designated E-sEVs@CHA, combines two innovations that address the two biggest bottlenecks in regenerative medicine for the esophagus. The first is the extracellular vesicles themselves. Small extracellular vesicles, often called exosomes, are nanoscale membrane-bound packets released by cells that carry microRNAs, proteins, and lipids. Mesenchymal stem cells, particularly those derived from umbilical cord tissue, are prized for the immunomodulatory and pro-regenerative cargo of their vesicles, but naive vesicles from unstimulated cells often lack the potency needed to meaningfully alter a hostile injury environment. The research team, led by Dan Luo and Baoxiang Wang, tackled this by preconditioning the umbilical cord-derived mesenchymal stem cells with interleukin-6, a master regulator of the acute inflammatory response, for 24 hours before collecting the vesicles.

The logic behind this cytokine priming rests on a growing understanding that the therapeutic function of mesenchymal stem cells is not fixed but dynamically licensed by their surroundings. When exposed to inflammatory signals, the cells upregulate key immunomodulatory factors such as COX-2 and TSG-6, and their vesicles inherit an amplified capacity to calm immune overreactions and promote repair. Previous work has shown that preconditioning with interferon-gamma, tumor necrosis factor-alpha, or interleukin-1 beta can supercharge vesicles for treating endometritis, colitis, and other inflammatory conditions. In the new study, interleukin-6 stimulation increased both the particle concentration and protein content of the harvested vesicles, with E-sEVs reaching 1.25 x 10^11 particles per milliliter and 1.40 milligrams of protein per milliliter, compared with 0.91 x 10^11 particles and 1.08 milligrams for naive vesicles. Transmission electron microscopy confirmed that both populations displayed the characteristic circular, double-layered membrane morphology, with average diameters around 70 nanometers.

In laboratory assays, the enhanced vesicles proved decisively more capable than their naive counterparts. When lipopolysaccharide-stimulated macrophages were treated with E-sEVs, expression of the pro-inflammatory cytokines TNF-alpha and iNOS fell sharply while the anti-inflammatory mediators IL-10 and Arg-1 rose. Flow cytometry revealed that the primed vesicles drove macrophages from the aggressive M1 phenotype toward the reparative M2 phenotype far more effectively than naive vesicles, whether starting from resting M0 macrophages or from LPS-polarized M1 cells. The vesicles also demonstrated antioxidant power: in endothelial and esophageal epithelial cells stressed with hydrogen peroxide, E-sEVs reduced reactive oxygen species accumulation and preserved mitochondrial membrane potential better than naive vesicles or the carrier alone. In a fibrosis model induced by transforming growth factor-beta, the primed vesicles more strongly suppressed the fibrotic markers alpha-SMA and type I collagen in fibroblasts.

The second innovation is the delivery vehicle. The esophagus is a hostile environment for any locally administered therapy because its muscular walls generate continuous peristaltic waves that sweep away conventional formulations within minutes. To overcome this, the researchers turned to cationic hyaluronic acid, a derivative of the natural extracellular matrix molecule modified with positively charged groups. These positive charges promote electrostatic adhesion to the negatively charged cell surfaces and matrix components of injured tissue, prolonging residence time. The team systematically tested concentrations from 5 to 20 percent by weight, measuring how far the viscous fluid slid down vertical surfaces of paper, plastic, latex, and porcine skin. At 5 percent, the gel flowed away too quickly to retain a therapeutic payload; at 20 percent, it was nearly immobile and risked obstructing the esophagus. The sweet spot, 15 percent, balanced strong adhesion with smooth injectability through a gavage needle, and release experiments showed that more than 70 percent of loaded vesicles were liberated within six hours.

Safety testing of the carrier was thorough. Live-dead staining and proliferation assays in fibroblasts showed no cytotoxicity, and hemolysis rates remained below 2 percent, well within biomaterial safety thresholds. When 15 percent CHA was instilled into healthy rats daily for 28 days, blood chemistry markers of liver and kidney function, including ALT, AST, creatinine, uric acid, and urea nitrogen, showed no significant differences from controls, and histological examination of the esophagus, heart, liver, spleen, lung, and kidneys revealed no pathological changes. The authors attribute this biocompatibility partly to the modest degree of cationization, only 23 percent, and to the gel-like polymeric structure, which avoids the membrane-disrupting behavior seen with highly charged nanoparticle carriers such as PEI.

The decisive test came in a rat model of corrosive esophageal injury. The researchers induced injury by instilling 15 percent sodium hydroxide solution into the esophagus, a protocol that produced clear mucosal damage and, by day 28, significant fibrotic narrowing confirmed by esophagography and Masson staining. Rats then received intraesophageal instillations of either the carrier alone, naive vesicles in the carrier, or the enhanced E-sEVs@CHA formulation every other day. Early on, at day 8, histology showed that treated animals retained intact mucosal and muscularis layers while untreated injured rats suffered structural disruption and heavy inflammatory infiltration. Molecular analysis confirmed that the combination therapy significantly reduced messenger RNA levels of the pro-inflammatory cytokines IL-1beta, IL-6, and TNF-alpha while boosting anti-inflammatory IL-10, with the primed formulation showing a particularly strong inhibitory effect on IL-6.

By day 28, the differences were striking. Esophagography revealed severe luminal narrowing in untreated injured rats, only limited improvement with the carrier alone, and modest benefit with naive vesicles, but the E-sEVs@CHA group maintained a significantly widened esophageal passage approaching that of healthy controls. Masson staining and quantitative collagen analysis showed that the primed formulation produced the greatest reduction in collagen deposition, and expression of the fibrotic genes TGF-beta, alpha-SMA, and collagen I was most strongly suppressed in this group. Fluorescent tracking in mice demonstrated that the adhesive carrier extended vesicle retention in the esophagus to roughly two to three hours, compared with rapid clearance for free vesicles. While the authors acknowledge this retention window is short, they argue that vesicles are rapidly internalized by target cells and can trigger sustained downstream signaling even after the extracellular payload has cleared.

To understand why the primed vesicles outperformed naive ones, the team performed small RNA sequencing and label-free quantitative proteomics. They identified 168 differentially expressed microRNAs between the two vesicle populations, with three standing out: miR-1246, miR-193a-5p, and miR-1290. The predicted targets of these microRNAs were enriched in signaling pathways central to cell proliferation, migration, and tissue repair, including PI3K-Akt, MAPK, cAMP, and HIF-1. Notably, miR-1246 was downregulated in the primed vesicles; because this microRNA normally suppresses PIK3AP1 and thereby restrains PI3K-Akt signaling, its reduction could theoretically unleash pro-survival and pro-migratory programs in esophageal epithelial cells. Proteomic analysis showed that the primed vesicles carried increased amounts of extracellular matrix components such as COL1A2, COL5A1, and VCAN, which may provide a provisional scaffold for cell anchorage, while inflammatory chemokines like IL-6, CCL2, and CXCL1, along with complement proteins and coagulation factors, were reduced, suggesting a shift toward a regenerative, low-inflammation microenvironment. Differentially expressed proteins were significantly enriched in the JAK-STAT pathway, a signaling hub that crosstalks extensively with PI3K-Akt, MAPK, and HIF-1.

The study positions E-sEVs@CHA as a multi-phasic therapy matched to the three overlapping phases of corrosive injury: acute necrosis, inflammatory response, and chronic fibrosis. By acutely damping cytokine storms and oxidative damage while chronically inhibiting the fibrotic remodeling that produces strictures, the system addresses the full pathological arc rather than merely dilating the aftermath. The findings also build on earlier work showing that adipose-derived stem cell exosomes in chitosan sponges prevented strictures in a porcine model, and they contrast with a prior report that a single intravenous dose of mesenchymal stem cells failed to heal caustic esophageal injury in rats, underscoring the importance of both vesicle priming and repeated local delivery through a bioadhesive scaffold. The authors caution that retention time remains a limitation and that repeated dosing or chemical modification of the hydrogel could further improve outcomes, but the strategy offers a compelling, cell-free blueprint for a condition that currently has few good options.

Subject of Research: A bioadhesive hydrogel delivering IL-6-primed mesenchymal stem cell extracellular vesicles for repairing corrosive esophageal injury

Article Title: Adhesive cationic hyaluronic acid loading with small extracellular vesicles from IL-6 activated mesenchymal stem cells improves repair of corrosive esophageal injury

Article References: Adhesive cationic hyaluronic acid loading with small extracellular vesicles from IL-6 activated mesenchymal stem cells improves repair of corrosive esophageal injury. (n.d.). https://doi.org/10.1016/j.mtbio.2026.103706

Image Credits: AI Generated

DOI: 10.1016/j.mtbio.2026.103706

Keywords: corrosive esophageal injury, extracellular vesicles, exosomes, mesenchymal stem cells, interleukin-6, cationic hyaluronic acid, bioadhesive hydrogel, esophageal stricture, anti-fibrosis, macrophage polarization, drug delivery, regenerative medicine