AIM:To study the effects of neurological improvement and remyelination after intracranial hemorrhage(ICH)in rats by a novel therapeutic strategy with hepatocyte growth factor(HGF)gene transfected human umbilical cord mesenchymal stem cells(hUCMSCs)by lentiviral vector.METHODS:ICH was induced in 60 adult male Sprague-Dawley rats by a stereotactically guided injection of bacterial type IV collagenase into the right internal capsule.Non-modified hUCMSCs,HGF-modified hUCMSCs with lentiviral vector or PBS were administered left intraventricularly 7 d after right internal capsule ICH.All rats underwent modified neurological severity scores for 35 d.Luxol fast blue staining,immunohistological staining and Western blotting assessments for myelin basic protein(MBP)were applied.RESULTS:The ICH rats receiving HGF-modified hUCMSCs demonstrated significant functional recovery,determined by modified neurological severity scores,compared to the other groups from 2 weeks after cell therapy.As indicated by Luxol fast blue staining,the percent area of demyelination was obviously reduced in the HGF-hUCMSC treatment group compared to the PBS control group and hUCMSC-only treatment group at 5 weeks after ICH.The expression of MBP detected by immunohistological staining and Western blotting was significantly higher in HGF-hUCMSCs treated brain than that in other groups(P