Therapeutic benefits of angiogenetic gene-modified human mesenchymal stem cells after cerebral ischemia

Abstract

Intravenous transplantation of human mesenchymal stem cells (hMSCs) expanded from adult bone marrow ameliorates functional deficits in rat cerebral infarction models. Several hypotheses to account for the therapeutic mechanisms have been suggested, but angiogenesis is thought to be of critical importance. Recently, we have reported the therapeutic benefits of hMSCs which have been transfected with the angiopoietin-1 gene in a rat permanent middle cerebral artery occlusion (MCAO) model. To potentially enhance the therapeutic effects of angiopoietin-1 gene-modified hMSC (Ang-hMSC), we transfected hMSCs with the angiopoietin-1 gene and the VEGF gene, and investigated whether the combination of Ang-1 and VEGF gene-modified hMSCs (Ang-VEGF-hMSC) contribute to functional recovery in a rat MCAO model. We induced MCAO using intraluminal vascular occlusion, and hMSCs, Ang-hMSCs, VEGF-hMSCs or Ang-VEGF-hMSCs were intravenously infused 6 h later. MRI and behavioral analyses revealed that rats receiving Ang-VEGF-hMSCs showed the greatest structural–functional recovery as compared to the other groups. These results suggest that intravenous administration of hMSCs transfected with the angiopoietin-1 and VEGF gene using a fiber-mutant adenovirus vector may represent a new strategy for the treatment of ischemia.

Introduction

Intravenous injection of human mesenchymal stem cells (hMSCs) several hours after ischemia onset can reduce infarction size and improve functional outcome in rat cerebral ischemia models (Chen et al., 2001, Honma et al., 2006, Horita et al., 2006, Iihoshi et al., 2004, Li et al., 2002, Liu et al., 2006, Nomura et al., 2005). Although the detailed mechanisms of therapeutic benefits of MSCs injection remain unclear, angiogenesis is thought to be involved in neurological recovery after ischemia (Chen et al., 2003, Krupinski et al., 1994, Onda et al., 2007).

Vascular endothelial growth factor (VEGF) and angiopoietin 1 (Ang-1) are both important in angiogenesis (Carmeliet and Collen, 1997), but have different effects on vessel formation. VEGF has strong angiogenic effects in brain (Zhang and Chopp, 2002), limb (Baumgartner et al., 1998) and myocardial ischemia models (Kastrup, 2003). It is required to initiate the formation of immature vessel trunks (Carmeliet and Collen, 1997). Angiopoietin is involved in maturation, stabilization, and remodeling of vessels (Davis et al., 1996, Suri et al., 1996, Suri et al., 1998, Yancopoulos et al., 2000), and promotes angiogenesis in the brain (Onda et al., 2007, Ward and Lamanna, 2004). VEGF treatment alone to promote neovascularization can have deleterious effects. It is a potent enhancer of vascular permeability to blood plasma proteins which could contribute to brain edema after cerebral infarction (Bates et al., 2002, Wang et al., 1996). Ang-1 protects the peripheral vasculature from vascular leakage (Thurston et al., 1999) and thus might account for its anti-edematic effects following cerebral ischemia. We have recently demonstrated that intravenous infusion of hMSCs genetically modified to secrete Ang-1 has a modest neuroprotective effect in a rat cerebral ischemia model (Onda et al., 2007). The present study was designed to determine whether VEGF and the combined hypersecretion of VEGF and Ang-1 by hMSCs could influence angiogenesis and functional outcome in a rat stroke model.