Sulfated chitosan directs the recovery of ischemic stroke by attenuating the inflammatory cascade.

Background: Ischemic stroke is considered a fatal ischemic disease with high mortality and morbidity. Acute ischemic stroke is a cascade of inflammatory reactions, which not only causes vascular degeneration but also leads to neurological disorders. During this period, the rapid response of neutrophil-dominated granulocytes releases cytokines and chemokines to affect tissue repair. Thus, effective regulation of neutrophils appears to be the key in treating major organ injuries associated with inflammation. Methods: This study developed a semisynthetic sulfated chitosan (SCS) associated with the functional sulfated groups. The immunoregulatory effects of SCS on neutrophils were tested by Real-Time Quantitative Reverse Transcription (RT-PCR), ELISA and immunofluorescence staining at gene and protein levels in vitro. Flow cytometry, WB and PCR were used to study the effect of neutrophils on macrophages, indicating the regulation of the inflammatory cascade by SCS. Acute ischemic stroke model was established to verify the effectiveness and the regulation of inflammatory cascade of SCS. Finally, the lower limb ischemia model was used to verify the universality of SCS in the treatment of ischemic diseases, especially with regard to acute inflammatory-related major organ damage. Results: SCS can not only promote neutrophil apoptosis, but also enable neutrophils to produce vascular-related subsets to regulate immunity and promote angiogenesis. Neutrophil stimulated by SCS mediated macrophage polarization via IL-10-induced Stat3 signaling pathway to weaken the inflammatory cascade. In animal models of ischemic hind limb and ischemic stroke, SCS had demonstrated its ability to shorten the acute inflammatory period, as indicated by neutrophil, and accelerate the subsequent repair period characterized by the presence of M₂ macrophages. Additionally, SCS effectively inhibits the expression of MMP-9 to provide a favorable environment for rapid extracellular matrix reconstruction. Encouragingly, treatment with SCS had been shown to reduce the expansion of the infarct volume by approximately 20% in our experiments. Conclusion: This study underscores the effect of SCS in regulating the heterogeneity of neutrophils in order to suppress the initiation of inflammation to treat ischemic stroke. Crucially, our approach relies on non-exogenous growth factors and cells, highlighting its remarkable potential for clinical translatability in the treatment of major organ injuries.