Multifunctional Integrated Nanozymes Facilitate Spinal Cord Regeneration by Remodeling the Extrinsic Neural Environment

Abstract

High levels of reactive oxygen species (ROS) and inflammation create a complicated extrinsic neural environment that dominates the initial post‐injury period after spinal cord injury (SCI). The compensatory pathways between ROS and inflammation limited the efficacy of modulating the above single treatment regimen after SCI. Here, novel “nanoflower” Mn3O4 integrated with “pollen” IRF‐5SiRNA was designed as a combination antioxidant and anti‐inflammatory treatment after SCI. The “nanoflower” and “pollen” structure was encapsulated with a neutrophil membrane for protective and targeted delivery. Furthermore, valence‐engineered nanozyme Mn3O4 imitated the cascade response of antioxidant enzymes with a higher substrate affinity compared to natural antioxidant enzymes. Nanozymes effectively catalyzed ROS to generate O2, which is advantageous for reducing oxidative stress and promoting angiogenesis. The screened “pollen” IRF‐5SiRNA could reverse the inflammatory phenotype by reducing interferon regulatory factors‐5 (IRF‐5) expression (protein level: 73.08% and mRNA level: 63.10%). The decreased expression of pro‐inflammatory factors reduced the infiltration of inflammatory cells, resulting in less neural scarring. In SCI rats, multifunctional nanozymes enhanced the proliferation of various neuronal subtypes (motor neurons, interneurons, and sensory neurons) and the recovery of locomotor function, demonstrating that the remodeling of the extrinsic neural environment is a promising strategy to facilitate nerve regeneration.

Nanozyme-Integrated Thermoresponsive In Situ Forming Hydrogel Enhances Mesenchymal Stem Cell Viability and Paracrine Effect for Efficient Spinal Cord Repair

“…The overproduction of ROS by infiltrated neutrophils and macrophages around the SCI lesion site contributes to oxidative damage of DNAs, proteins, and lipids in neural cells as well as transplanted MSCs, resulting in the low survival rate of transplanted MSCs and greatly limiting the therapeutic efficiency of MSCs for SCI . Therefore, we further compared the oxidative microenvironmental condition of the spinal cord tissue after different treatments . Immunofluorescence staining results reveal that the levels of 4-hydroxynonenal (4-HNE, a product of lipid peroxidation) and inducible nitric oxide synthase (iNOS, proinflammatory cellular signaling molecule) are lower around the lesion sites in the CeNZ-gel group compared to the SCI and blank gel groups (Figure a,b), indicating that CeNZ-gel effectively reduces lipid peroxidation as well as the inflammatory response in vivo .…”

“…44 Therefore, we further compared the oxidative microenvironmental condition of the spinal cord tissue after different treatments. 52 Immunofluorescence staining results reveal that the levels of 4-hydroxynonenal (4-HNE, a product of lipid peroxidation) 45 and inducible nitric oxide synthase (iNOS, proinflammatory cellular signaling molecule) 46 are lower around the lesion sites in the CeNZ-gel group compared to the SCI and blank gel groups (Figure 5a,b), indicating that CeNZ-gel effectively reduces lipid peroxidation as well as the inflammatory response in vivo.…”

“…H 2 O 2 was utilized to mimic the oxidative stress microenvironment. 52 MSCs (5 × 10 5 cells/mL) encapsulated in the hydrogel were cultured in a medium containing 100 μM H 2 O 2 for 24 h. 53 Then, the MSCencapsulated hydrogel was incubated with Calcein/PI propidium iodide at 37 °C for 30 min and examined by CLSM (Nikon A1R, Japan).…”

“…H 2 O 2 was utilized to mimic the oxidative stress microenvironment. 52 MSCs (5 × 10 5 cells/mL) encapsulated in the hydrogel were cultured in a medium containing 100 μM H 2 O 2 for 24 h. 53 Then, the MSC-encapsulated hydrogel was incubated with 10 μM dichlorodihydrofluorescein diacetate (DCFH-DA) at 37 °C for 30 min and nuclei were stained with 2-(4amidinophenyl)-6-indolecarbamidine dihydrochloride (DAPI; Beyotime Biotech Co., Ltd., China). The images were obtained using CLSM (Nikon A1R, Japan).…”

“…H 2 O 2 was utilized to mimic the oxidative stress microenvironment. 52 MSCs (5 × 10 5 cells/mL) encapsulated in the hydrogel were cultured in a medium containing 100 μM H 2 O 2 for 24 h. 53 Then, the MSC-encapsulated hydrogel was ELISA Assay. The concentrations of growth factors including VEGF, ANG-1, and TGF-β1 secreted from MSCs encapsulated in the blank gel or CeNZ-gel were examined using ELISA kits (Enzymelinked Biotech Co., Ltd., China).…”