Allogeneic Gene-Modified Mesenchymal Stem Cells for Stable Stroke: Mechanism of Action and Translation to the Clinic (IN8-2.004)

Abstract

Objective: MSCs transfected with Notch-1 have demonstrated regenerative properties in rodent models of stable stroke. While cell replacement mechanisms have been ruled out, the details of the cell9s regenerative mechanism of action are not clear. Here we test several hypotheses; the production of soluble trophic factors, the production of beneficial extracellular matrix, and anti-inflammatory/immunosuppressive effects. Background MSCs secrete soluble factors that could serve as positive signals for regeneration and have well-established anti-inflammatory properties. Less well-studied is the production of beneficial extracellular matrix. Here we demonstrate these mechanisms at play in vitro and in rat models of stroke. Design/Methods: Rescue of primary neurons from insults (oxygen-glucose deprivation, excitotoxicity) can be mediated by co-culture with MSCs or by conditioned medium, demonstrating the effects of soluble factors. Analysis of conditioned medium revealed several key factors and demonstrated phenotypic differences between MSCs and Notch-transfected MSCs. Similar co-culture experiments demonstrated the beneficial effects of extracellular matrix produced by these cells. Mixed lymphocyte reactions demonstrated the immunosuppressive effects and again showed the phenotypic effects of Notch transfection. Immunohistochemical observations in models of neural injury supported the in vitro findings. Results: Secreted factors from Notch-transfected MSCs provide neurotrophic support to primary neurons in vitro. Analysis of extracellular matrix produced by these cells identified proteins contributing to their efficacy. Inflammation acts as a barrier to neural regeneration. MSCs attenuate these effects. Conclusions: Failure of regeneration after stroke appears to be a lack of sufficent positive stimuli (trophic factors etc.) and the presence of inhibitory stimuli (inflammation). No single entity has been found that can overcome these barriers. Cell therapy, working by multiple mechanisms, may provide a way forward. While mechanistic studies continue, GMP manufacturing and GLP safety studies have led to an active IND. A Phase 1 clinical trial is underway for patients with stable ischemic stroke. Supported by: SanBio Inc. Disclosure: Dr. Case has received personal compensation for activities with SanBio. Dr. Case holds stock and/or stock options in SanBio, which sponsored research in which Dr. Case was involved as an investigator.