Study of Urinary Kallikrein to Enhance Collateral Circulation in Symptomatic Intracranial Atherosclerosis

Inclusion Criteria: 1. Acute ischemic stroke or TIA within 72 hours; 2. Intracranial ICA, MCA M1 segment stenosis (\>70%) Exclusion Criteria: 1. \>70% Stenosis in an intracranial artery other than the culprit artery. 2. \>50% Stenosis of an extracranial carotid or vertebral artery on the ipsilateral side. 3. Perforator strokes based on MRI. 4. Non-atherosclerotic lesion, for example, moyamoya disease, vascular inflammatory disease due to infection, autoimmunity diseases, developmental or genetic abnormalities, for example, fibromuscular dysplasia, sickle-cell anaemia, suspected vasospasm. 5. Potential cardiac embolism as cause. 6. Intracranial haemorrhage within 6 weeks. 7. Concomitant intracranial tumour, aneurysm or arteriovenous malformation. 8. Known contraindications for heparin, aspirin, clopidogrel or contrast. 9. Haemoglobin \<10 g/dL, blood platelet count \<100 000, international normalisation ratio \>1.5, or other uncorrectable coagulopathies.Impaired liver function (alanine aminotransferase or glutamic oxalacetic transaminase ≥ 3×upper limit of normal) or renal function (serum creatinie ≥ 1.5mg/dl); 10. A baseline modified Rankin Score of ≥3. 11. Life expectancy of \<1 year due to the concomitant illness. 12. Pregnant or lactating women. 13. long-term statins users. 14. History of mental instability or dementia.