The anti-inflammatory cytokine interleukin-10 (IL-10) has been explored previously as a treatment method for spinal cord injury (SCI) due to its ability to attenuate pro-inflammatory cytokines and reduce apoptosis. Primary limitations when using systemic injections of IL-10 are that it is rapidly cleared from the injury site and that it does not cross the blood–spinal cord barrier. Here, mineral-coated microparticles (MCMs) were used to obtain a local sustained delivery of IL-10 directly into the injury site after SCI. Female Sprague-Dawley rats were contused at T10 and treated with either an intraperitoneal injection of IL-10, an intramedullary injection of IL-10, or MCMs bound with IL-10 (MCMs+IL-10). After treatment, cytokine levels were measured in the spinal cord, functional testing and electrophysiology were performed, axon tracers were injected into the brainstem and motor cortex, macrophage levels were counted using flow cytometry and immunohistochemistry, and lesion size was measured. When treated with MCMs+IL-10, IL-10 was significantly elevated in the injury site and inflammatory cytokines were significantly suppressed, prompting significantly less cells expressing antigens characteristic of inflammatory macrophages and significantly more cells expressing antigens characteristic of earlier stage anti-inflammatory macrophages. Significantly more axons were preserved within the rubrospinal and reticulospinal tracts through the injury site when treated with MCMs+IL-10; however, there was no significant difference in corticospinal tract axons preserved, regardless of treatment group. The rats treated with MCMs+IL-10 were the only group with a significantly higher functional score compared to injured controls 28 days post-contusion. These data demonstrate that MCMs can effectively deliver biologically active IL-10 for an extended period of time altering macrophage phenotype and aiding in functional recovery after SCI.

Neural Regen Res, Official publication of Publishing House of Neural Regeneration Research China Association of Rehabilitation Medicine,China

Spinal cord injury (SCI) often results in permanent loss of motor and sensory function. After SCI, the blood–spinal cord barrier (BSCB) is disrupted, causing the infiltration of neutrophils and macrophages, which secrete several kinds of cytokines, as well as matrix metalloproteinases (MMPs). MMPs are proteases capable of degrading various extracellular matrix (ECM) proteins, as well as many non-matrix substrates. The tissue inhibitor of MMPs (TIMP)-1 is significantly upregulated post-SCI and operates via MMP-dependent and MMP-independent pathways. Through the MMP-dependent pathway, TIMP-1 directly reduces inflammation and destruction of the ECM by binding and blocking the catalytic domains of MMPs. Thus, TIMP-1 helps preserve the BSCB and reduces immune cell infiltration. The MMP-independent pathway involves TIMP-1’s cytokine-like functions, in which it binds specific TIMP surface receptors. Through receptor binding, TIMP-1 can stimulate the proliferation of several types of cells, including keratinocytes, aortic smooth muscle cells, skin epithelial cells, corneal epithelial cells, and astrocytes. TIMP-1 induces astrocyte proliferation, modulates microglia activation, and increases myelination and neurite extension in the central nervous system (CNS). In addition, TIMP-1 also regulates apoptosis and promotes cell survival through direct signaling. This review provides a comprehensive assessment of TIMP-1, specifically regarding its contribution to inflammation, ECM remodeling, and scar formation after SCI.

Neural Regen Res, Official publication of Publishing House of Neural Regeneration Research China Association of Rehabilitation Medicine,China

Spinal cord injury (SCI) triggers a secondary injury cascade characterized by neuroinflammation, reactive gliosis, and neuronal apoptosis. While many pro-inflammatory cytokines contributing to this cascade reach peak upregulation within 24 h, Interleukin-18 (IL-18) exhibits a delayed upregulation profile, typically peaking 7 days post-injury. This review examines the temporal regulation and cell-specific roles contributing to the rise in IL-18 after SCI. Following primary insult, damage-associated molecular patterns prime and activate the NLRP3 inflammasome, which in turn drives latent IL-18 secretion. Cellularly, microglia function as the primary producers of IL-18 via the TLR4/p38-MAPK pathway, while astrocytes serve as the primary responders through IL-18R/p65-NF-κβ signaling. The microglia-astrocyte cross-talk propagates reactive gliosis, drives neuropathic pain, facilitates neuronal loss, and potentially contributes to the formation of the astrocytic border. Targeted therapeutic interventions such as upstream inhibition of NLRP3 inflammasome assembly or direct IL-18 neutralization successfully mitigate neuroinflammation. By either inhibiting NLRP3 inflammasome activation or directly neutralizing IL-18, these treatments shift the microglial toward a protective state, restrict histological damage, and significantly improve functional recovery.