Abstract

Acute lung injury (ALI) is characterized by uncontrolled inflammation, oxidative stress, and fibrotic remodeling, yet mesenchymal stem cell (MSC) therapies remain limited by poor retention and insufficient microenvironmental adaptation. Here, we engineered a composite system, GelMA@hMSCs-Alg-RGD (hereafter referred to as the sandwich composite), in which RGD (Arg-Gly-Asp) -functionalized alginate microbeads support human MSCs and are encapsulated within an adhesive, stress-relaxing dopamine-modified GelMA (GelMA-DA) hydrogel. This design provided a 3-dimensional low-tension niche that preserved MSC identity while enhancing paracrine potency, antioxidative capacity, and resistance to apoptosis. Conditioned media from hMSCs-Alg-RGD promoted endothelial proliferation, migration, invasion, and tube formation, while attenuating oxidative stress in a partially cytoskeleton-dependent manner. In fibroblasts, treatment suppressed alpha-smooth muscle actin stress fiber formation, focal adhesion maturation, and Yes-associated protein nuclear translocation, thereby preventing myofibroblast differentiation and restoring isotropic morphology. GelMA@hMSCs-Alg-RGD enabled rapid gelation, robust wet adhesion, stress-relaxing mechanics, and controlled degradation, resulting in prolonged pulmonary retention confirmed by in vivo and ex vivo imaging. In murine ALI, this strategy alleviated edema, reduced inflammatory cytokines (interleukin-6, tumor necrosis factor-α, and interleukin-1β), myeloperoxidase activity, and lipid peroxidation (malondialdehyde), while enhancing superoxide dismutase activity, improving survival, and reshaping the immune microenvironment through reduced neutrophil infiltration and enhanced macrophage M1 → M2 polarization. Together, these results establish GelMA@hMSCs-Alg-RGD as a bioengineered therapeutic that integrates localized retention with paracrine amplification to reprogram immune and mechanical microenvironments, offering a broadly applicable platform f