Cell polarization in ischemic stroke: molecular mechanisms and advances

Ischemic stroke is a cerebrovascular disease associated with high mortality and disability rates. Since the inflammation and immune response play a central role in driving ischemic damage, it becomes essential to modulate excessive inflammatory reactions to promote cell survival and facilitate tissue repair around the injury site. Various cell types are involved in the inflammatory response, including microglia, astrocytes, and neutrophils, each exhibiting distinct phenotypic profiles upon stimulation. They display either proinflammatory or anti-inflammatory states, a phenomenon known as ‘cell polarization.’ There are two cell polarization therapy strategies. The first involves inducing cells into a neuroprotective phenotype in vitro, then reintroducing them autologously. The second approach utilizes small molecular substances to directly affect cells in vivo. In this review, we elucidate the polarization dynamics of the three reactive cell populations(microglia, astrocytes, and neutrophils) in the context of ischemic stroke, and provide a comprehensive summary of the molecular mechanisms involved in their phenotypic switching. By unraveling the complexity of cell polarization, we hope to offer insights for future research on neuroinflammation and novel therapeutic strategies for ischemic stroke.

Reprogramming rat astrocytes into neurons using small molecules for cell replacement following intracerebral hemorrhage

Astrocytes are promising source cells to replace neurons lost to disease owing to a shared lineage and capacities for dedifferentiation and proliferation under pathological conditions.Reprogramming of astrocytes to neurons has been achieved by transcription factor modulation,but reprogramming in vitro or in vivo using small-molecule drugs may have several advantages for clinical application.For instance,small molecules can be extensively characterized for efficacy,toxicity,and tumorigenicity in vitro;induce rapid initiation and subsequent reversal of transdifferentiation upon withdrawal,and obviate the need for exogenous gene transfection.Here we report a new astrocyte-neuron reprogramming strategy using a combination of small molecules(0.5 m M valproic acid,1μM Rep Sox,3μM CHIR99021,2μM I-BET151,10μM ISX-9,and 10μM forskolin).Treatment with this drug combination gradually reduced expression levels of astroglial marker proteins(glial fibrillary acidic protein and S100),transiently enhanced expression of the neuronal progenitor marker doublecortin,and subsequently elevated expression of the mature neuronal marker Neu N in primary astrocyte cultures.These changes were accompanied by transition to a neuron-like morphological phenotype and expression of multiple neuronal transcription factors.Further,this drug combination induced astrocyte-to-neuron transdifferentiation in a culture model of intracerebral hemorrhage(ICH)and upregulated many transdifferentiation-associated signaling molecules in ICH model rats.In culture,the drug combination also reduced ICH model-associated oxidative stress,apoptosis,and pro-inflammatory cytokine production.Neurons derived from small-molecule reprogramming of astrocytes in adult Sprague-Dawley rats demonstrated long-term survival and maintenance of neuronal phenotype.This small-molecule-induced astrocyte-to-neuron transdifferentiation method may be a promising strategy for neuronal replacement therapy.

Neuroprotective effects of adipose-derived stem cells on ferrous sulfate-induced neurotoxicity

Background:Ferrous ion,a degradation product of hematomas,induces inflammatory reactions and other secondary injuries after intracerebral hemorrhage(ICH).Our study aimed to investigate the specific neuroprotective mechanism of adipose-derived stem cells(ADSCs)on ferrous ion-induced neural injury in vitro.Methods:ADSCs were co-cultured with primary cortical neurons in a transwell system treated with ferrous sulfate to generate an in vitro ICH model.ADSCs and cortical neurons were cultured in the upper and lower chambers,respectively.Neuron apoptosis was determined by flow cytometry.The levels of insulin-like growth factor-1(IGF-1),malondialdehyde(MDA)and nitric oxide synthase(NOS)activity in neuron culture medium were detected with commercial kits.In neurons,protein expression in phosphatidylinositol-3-kinase(PI3 K)/protein kinase B(Akt)signaling pathway,nuclear factor erythroid 2-related factor 2(Nrf2)/heme oxygenase-1(HO-1)signaling pathway and apoptosis-related proteins were detected by western blot.Results:ADSCs attenuated neural apoptosis,reduced MDA levels and NOS activity induced by ferrous sulfate.In neurons,IGF-1 was increased,as were p-PI3 K,p-Akt,Nrf2,HO-1,and Bcl-2 while cleaved caspase 3 was down-regulated.Conclusions:ADSCs exert neuroprotective effects against ferrous iron-induced neuronal damage by secreting IGF-1 and increasing the levels of Akt-dependent Nrf2/ARE signaling pathway.