Characterization of CRISPR/Cas9-edited human placental allogenic stromal cells with low tissue factor expression and reduced thrombotic effects.

The tissue factor (TF/CD142) expressed by mesenchymal stromal cells (MSCs) has been regarded as a safety concern in clinical applications as it may trigger thrombosis when MSCs administered intravenously. Human placental allogenic stromal cells (ASCs) are culture-expanded, undifferentiated MSC-like cells derived from full-term postpartum placenta and possess immunomodulatory and pro-angiogenic activities, however, express TF. Here we performed CRISPR/Cas9-mediated TF gene knock out (TFKO) in ASCs, leading to significantly lower TF expression, activity and thrombotic effects. ASCs' characteristics including expansion, expression of phenotypic markers and secretory profile remained unchanged in edited cells, and their immunomodulatory activities, which are functionally relevant to therapeutic applications, were not affected upon TFKO. Taken together, this study provides a feasible strategy which could improve the clinical safety features of MSC-based cell therapy by CRISRP/Cas9-mediated TF gene knock out.

Intrathecal Injection of Allogenic Bone Marrow-Derived Mesenchymal Stromal Cells in Treatment of Patients with Severe Ischemic Stroke: Study Protocol for a Randomized Controlled Observer-Blinded Trial.

Mesenchymal stromal cells (MSCs) can differentiate into multiple tissues. Preclinical studies have shown that MSC-based therapy is a potential new treatment approach for ischemic stroke. These results support the urgent need for further studies of MSC transplantation in the treatment of ischemic stroke in humans. Here, we develop a prospective, randomized, controlled, observer-blinded phase II trial to assess the clinical safety, feasibility, and therapeutic mechanisms of allogenic bone marrow-derived MSCs (BM-MSCs) by intrathecal infusion in the treatment of patients with cerebral infarction within the middle cerebral artery and with a National Institutes of Health Stroke Scale (NIHSS) score from 15 to 25. Sample size calculation has determined that a patient population of 118, with ischemic stroke between 30 and 90 days following onset, will be randomly divided into experimental (n = 59) and control (n = 59) groups. Then eligible patients will receive four intrathecal infusions of allogenic BM-MSCs (1 × 106 cells/kg body weight) once a week. All patients have detailed functional assessments and magnetic resonance imaging prior to cell infusion and at intervals up to 1 year after. The primary outcome is the score on the modified Rankin Scale at 90 days after treatment, and the second outcomes include multiple indicators of safety and feasibility. And this trial has been registered as ChiCTR-INR-16008908 (25 July 2016).