In the brain, the role of matrilin-3, an extracellular matrix component in cartilage, is unknown. Here, we identify that matrilin-3 decreased in reactive astrocytes but was unchanged in neurons after ischemic stroke in animals. Importantly, it declined in serum of patients with acute ischemic stroke. Genetic or pharmacological inhibition or supplementation of matrilin-3 aggravates or reduces brain injury, astrocytic cell death, and glial scar, respectively, but has no direct effect on neuronal cell death. RNA sequencing demonstrates that Matn3^-/- mice display an increased inflammatory response profile in the ischemic brain, including the nuclear factor κB (NF-κB) signaling pathway. Both endogenous and exogenous matrilin-3 reduce inflammatory mediators. Mechanistically, extracellular matrilin-3 enters astrocytes via caveolin-1-mediated endocytosis. Cytoplasmic matrilin-3 translocates into the nucleus by binding to NF-κB p65, suppressing inflammatory cytokine transcription. Extracellular matrilin-3 binds to BMP-2, blocking the BMP-2/Smads pathway. Thus, matrilin-3 is required for astrocytes to exert neuroprotection, at least partially, by suppressing astrocyte-mediated neuroinflammation.

Rationale: Marfan syndrome (MFS), which is a dominantly inherited connective tissue disease resulting from a mutation in the FBN1 gene, exhibits variable manifestations affecting the cardiovascular, musculoskeletal, ophthalmologic, and pulmonary systems. Notably, neurologic deficiency, which involves ischemic or hemorrhagic stroke, is a rare but severe manifestation. The safety of rt-PA treatment for ischemic stroke caused by MFS is still under discussion. Patient concerns: In the current report, we discuss 3 atypical MFS cases presented as acute ischemic stroke, compared to those exhibiting cardiovascular and musculoskeletal abnormalities. Diagnoses: Three patients were diagnosed with acute ischemic stroke accompanied by MFS based on clinical manifestations, imaging examinations, and genetic testings. Interventions: The first case underwent intravenous thrombolytic therapy with rt-PA, the second case received antiplatelet therapy, and the third case received anticoagulant therapy and perfusion therapy. Outcomes: The neurologic deficiency of all three patients showed improvement upon discharge, and there were no symptoms of recurrence observed during the follow-up period. Lessons subsections: MFS is a rare etiology in young people with embolic stroke of undetermined source. Physicians should take MFS into consideration when they observe the characteristic symptoms during a consultation. The potential pathogenesis of ischemic stroke secondary to MFS may include cardio-embolism, arterial dissection, and hypoperfusion. Although intravenous thrombolysis is a promising therapy to treat acute ischemic stroke, further examinations should be conducted to rule out contraindications in patients with a suspicion of MFS.