Human bone marrow stromal cell cultures conditioned by traumatic brain tissue extracts: growth factor production

Treatment of traumatic brain injury (TBI) with bone marrow stromal cells (MSCs) improves functional outcome in the rat. However, the specific mechanisms by which introduced MSCs provide benefit remain to be elucidated. Currently, the ability of therapeutically transplanted MSCs to replace injured parenchymal CNS tissue appears limited at best. Tissue replacement, however, is not the only possible compensatory avenue in cell transplantation therapy. Various growth factors have been shown to mediate the repair and replacement of damaged tissue, so trophic support provided by transplanted MSCs may play a role in the treatment of damaged tissue. We therefore investigated the temporal profile of various growth factors, brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and hepatocyte growth factor (HGF), within cultures of human MSCs (hMSCs) conditioned with cerebral tissue extract from TBI. hMSCs were cultured with TBI extracts of rat brain in vitro and quantitative sandwich enzyme-linked immunosorbent assays (ELISAs) were performed. TBI-conditioned hMSCs cultures demonstrated a time-dependent increase of BDNF, NGF, VEGF, and HGF, indicating a responsive production of these growth factors by the hMSCs. The ELISA data suggest that transplanted hMSCs may provide therapeutic benefit via a responsive secretion of an array of growth factors that can foster neuroprotection and angiogenesis.     

Combination therapy of stroke in rats with a nitric oxide donor and human bone marrow stromal cells enhances angiogenesis and neurogenesis

We tested the hypothesis that intravenous infusion of human marrow stromal cells (hMSC) with a nitric oxide donor, (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl) aminio] diazen-1-ium-1,2-diolate (DETA/NONOate), enhances angiogenesis, neurogenesis and neurological functional recovery after stroke in rats compared to individual therapy. Experimental groups consist of rats subjected to 2 h of middle cerebral artery occlusion (MCAo) and at 24 h after MCAo intravenous injection of (n=10/group): Group 1: phosphate buffered saline (PBS 1 ml) for control. Group 2: NONOate alone (0.4 mg/kg). Group 3: hMSCs (1 x 10(6)) alone. Group 4: hMSCs (1 x 10(6)) with NONOate (0.4 mg/kg). Functional tests and immunohistochemical staining were performed. Marginal functional recovery after treatment of stroke was found with 1 x 10(6) hMSCs alone (p=0.06) and no benefit was detected with NONOate alone (0.4 mg/kg, p=0.64). However, NONOate+hMSCs in combination significantly induced functional recovery (p<0.05). Treatment using hMSC in combination with NONOate significantly increased vessel perimeter and endothelial cell proliferation compared with hMSC or NONOate alone treatment (p<0.05). Cell proliferation and neurogenesis were assessed with bromodeoxyuridine (BrdU) labeling and immunostaining for cell type-specific markers. Combination treatment promoted increased, BrdU positive cell number in the subventricular zone (SVZ), migrating neuronal doublecortin immunoreactive cells and VEGF and bFGF expression in the ischemic boundary area compared to individual treatment. The functional therapeutic enhancement of combination treatment may be attributed to increased plasticity induced by the combination of a nitric oxide donor and hMSC therapy. These data suggest that pharmacological and cellular therapy may provide an additive therapeutic benefit after stroke.     

Neurotrophic and growth factor gene expression profiling of mouse bone marrow stromal cells induced by ischemic brain extracts

Treatment of rodents after stroke with bone marrow stromal cells (BMSCs) improves functional outcome. However, the mechanisms underlying this benefit have not been ascertained. This study focused on the contribution of neurotrophic and growth factors produced by BMSCs to therapeutic benefit. Rats were subjected to middle cerebral artery occlusion and the ischemic brain extract supernatant was collected to prepare the conditioned medium. The counterpart normal brain extract from non‐ischemic rats was employed as the experimental control. Using microarray assay, we measured the changes of the neurotrophin associated gene expression profile in BMSCs cultured in different media. Furthermore, real‐time RT‐PCR and fluorescent immunocytochemistry were utilized to validate the gene changes. The morphology of BMSCs, cultured in the ischemic brain‐conditioned medium for 12 h, was dramatically altered from a polygonal and flat appearance to a fibroblast‐like long and thin cell appearance, compared to those in the normal brain‐conditioned medium and the serum replacement medium. Forty‐four neurotrophin‐associated genes in BMSCs were identified by microarray assay under all three culture media. Twelve out of the 44 genes (7 neurotrophic and growth factor genes, 5 receptor genes) increased in BMSCs cultured in the ischemic brain‐conditioned medium compared to the normal brain‐conditioned medium. Real time RT‐PCR and immunocytochemistry validated that the ischemic brain‐conditioned medium significantly increased 6/7 neurotrophic and growth factor genes, compared with the normal brain‐conditioned medium. These six genes consisted of fibroblast growth factor 2, insulin‐like growth factor 1, vascular endothelial growth factor A, nerve growth factor beta, brain‐derived neurotrophic factor and epidermal growth factor. Our results indicate that transplanted BMSCs may work as ‘small molecular factories’ by secreting neurotrophins, growth factors and other supportive substances after stroke, which may produce therapeutic benefits in the ischemic brain.     

Human mesenchymal stem cell‐derived Schwann cell‐like cells exhibit neurotrophic effects,via distinct growth factor production,in a model of spinal cord injury

Human bone marrow‐derived mesenchymal stem cells (hMSCs) are considered a desirable cell source for autologous cell transplantation therapy to treat nervous system injury due to their ability to differentiate into specific cell types and render the tissue microenvironment more favorable for tissue repair by secreting various growth factors. To potentiate their possible trophic effect, hMSCs were induced without genetic modification to adopt characteristics of Schwann cells (SCs), which provide trophic support for regenerating axons. The induced hMSCs (shMSCs) adopted a SC‐like morphology and expressed SC‐specific proteins including the p75 neurotrophin receptor, which correlated with cell‐cycle exit. In addition, shMSCs secreted higher amounts of several growth factors, such as hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) when compared with uninduced hMSCs. Coculture of shMSCs with Neuro2A cells significantly increased neurite outgrowth and cell proliferation but decreased cell death. Transplantation of shMSCs in an ex vivo model of spinal cord injury dramatically enhanced axonal outgrowth, which was mediated by HGF and VEGF secretion and also decreased cell death. These results demonstrate that shMSCs could serve as an endogenous source of neurotrophic growth factors to facilitate axonal regeneration while at the same time protecting the resident cells at the site of tissue injury. We propose that these induced hMSCs without genetic modification are useful for autologous cell therapy to treat nervous system injury. © 2010 Wiley‐Liss, Inc.     

Human marrow stromal cell therapy for stroke in rat: neurotrophins and functional recovery

OBJECTIVE: To test the effect of i.v.-injected human bone marrow stromal cells (hMSC) on neurologic functional deficits after stroke in rats. METHODS: Rats were subjected to transient middle cerebral artery occlusion and IV injected with 3 x 10(6) hMSC 1 day after stroke. Functional outcome was measured before and 1, 7, and 14 days after stroke. Mixed lymphocyte reaction and the development of cytotoxic T lymphocytes measured the immune rejection of hMSC. A monoclonal antibody specific to human cellular nuclei (mAb1281) was used to identify hMSC and to measure neural phenotype. ELISA analyzed neurotrophin levels in cerebral tissue from hMSC-treated or nontreated rats. Bromodeoxyuridine injections were used to identify newly formed cells. RESULTS: Significant recovery of function was found in rats treated with hMSC at 14 days compared with control rats with ischemia. Few (1 to 5%) hMSC expressed proteins phenotypic of brain parenchymal cells. Brain-derived neurotrophic factor and nerve growth factor significantly increased, and apoptotic cells significantly decreased in the ischemic boundary zone; significantly more bromodeoxyuridine-reactive cells were detected in the subventricular zone of the ischemic hemisphere of rats treated with hMSC. hMSC induced proliferation of lymphocytes without the induction of cytotoxic T lymphocytes. CONCLUSION: Neurologic benefit resulting from hMSC treatment of stroke in rats may derive from the increase of growth factors in the ischemic tissue, the reduction of apoptosis in the penumbral zone of the lesion, and the proliferation of endogenous cells in the subventricular zone.     

Brain and spinal cord affected by amyotrophic lateral sclerosis induce differential growth factors expression in rat mesenchymal and neural stem cells

C. Nicaise, D. Mitrecic and R. Pochet (2011) Neuropathology and Applied Neurobiology 37, 179–188
Brain and spinal cord affected by amyotrophic lateral sclerosis induce differential growth factors expression in rat mesenchymal and neural stem cells Stem cell research raises hopes for incurable neurodegenerative diseases. In amyotrophic lateral sclerosis (ALS), affecting the motoneurones of the central nervous system (CNS), stem cell‐based therapy aims to replace dying host motoneurones by transplantation of cells in disease‐affected regions. Moreover, transplanted stem cells can serve as a source of trophic factors providing neuroprotection, slowing down neuronal degeneration and disease progression. Aim: To determine the profile of seven trophic factors expressed by mesenchymal stem cells (MSC) and neural stem cells (NSC) upon stimulation with CNS protein extracts from SOD1‐linked ALS rat model. Methods: Culture of rat MSC, NSC and fibroblasts were incubated with brain and spinal cord extracts from SOD1(G93A) transgenic rats and mRNA expression of seven growth factors was measured by quantitative PCR. Results: MSC, NSC and fibroblasts exhibited different expression patterns. Nerve growth factor and brain‐derived neurotropic factor were significantly upregulated in both NSC and MSC cultures upon stimulation with SOD1(G93A) CNS extracts. Fibroblast growth factor 2, insulin‐like growth factor and glial‐derived neurotropic factor were upregulated in NSC, while the same factors were downregulated in MSC. Vascular endothelial growth factor A upregulation was restricted to MSC and fibroblasts. Surprisingly, SOD1(G93A) spinal cord, but not the brain extract, upregulated brain‐derived neurotropic factor in MSC and glial‐derived neurotropic factor in NSC. Conclusions: These results suggest that inherent characteristics of different stem cell populations define their healing potential and raise the concept of ALS environment in stem cell transplantation.     

Neurotrophic factor expression after focal brain ischemia preceded by different preconditioning strategies

BACKGROUND: Both prolonged brain ischemia and preconditioning (PC) induce expression of neurotrophic factors. However, the influence of PC on their expression after a long-term ischemia remains vague. Previously, we have found various effects of PC on mRNA levels of different cytokines after focal brain ischemia. Thus, we investigated mRNA expression of nerve growth factor, brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor after 90-min middle cerebral artery occlusion (MCAo) preceded by ischemic or chemical PC. METHODS: MCAo was induced in rats using the suture method. PC had been carried out 3 days earlier. There were 4 experimental groups: MCAo alone; ischemic PC and MCAo; chemical PC and MCAo, and sham-operated rats. Expression of mRNAs in the ipsi- and contralateral cortex was studied by semiquantitative RT-PCR at 12 and 24 h after MCAo. RESULTS: Despite clearly neuroprotective effects of both PC strategies, mRNA levels of neurotrophic factors were similar in tolerant and nontolerant rats. Only BDNF mRNA expression, 12 h after reperfusion, was lower when ischemic PC was applied prior to long-term ischemia. CONCLUSIONS: These results suggest that PC generally does not change the expression of neurotrophic factor expression after a long-term focal brain ischemia compared to the nontolerant state.     

Caspase inhibition by Z-VAD increases the survival of grafted bone marrow cells and improves functional outcome after MCAo in rats

Marrow stromal cells (MSCs) transplantation into brain has been employed to treat experimental ischemia. However, MSCs undergo apoptosis and few survive in the ischemic brain. We test the hypotheses that coadministration of bone marrow cells (BMCs) with a cell-permeable inhibitor of caspases, Z-Val-Ala-DL-Asp-fluoromethylketone (Z-VAD), into the ischemic boundary zone (IBZ) of brain promotes BMCs survival and improve outcome. Experimental groups consist of: 24 h after MCAo, either phosphate-buffered saline (PBS, n=4), dead BMC (n=4), fresh BMC (n=10), Z-VAD only (n=4), or BMC with Z-VAD (n=6) were intracerebrally injected. BMCs were harvested from donor adult rats labeled with bromodeoxyuridine (BrdU). Rats were subjected to an adhesive-removal somatosensory and motor-rotarod functional tests before MCAo and at 1 and 7 days after MCAo. Rats treated with a combination of Z-VAD and BMCs exhibited significant improvement in the adhesive-removal test at 7 days compared with the control group (combined MCAo+PBS and MCAo+dead BMC) (p<0.01), and the numbers of BrdU-BMC increased (p<0.05) and apoptotic cells decreased (p<0.05) compared with BMC alone transplantation. Our data suggest that intracerebral coadministration of BMC with Z-VAD enhances the survival of grafted BMC and improves neurological functional recovery after MCAo.     

Effects of nerve growth factor and Noggin-modified bone marrow stromal cells on stroke in rats

Treatment with bone marrow stromal cells (BMSCs) ameliorates neurological functional deficits after stroke. Nerve growth factor (NGF) is a neurotrophic factor that supports the survival and growth of neural cells. Noggin, an antagonist of bone morphogenetic protein (BMP), promotes the differentiation of stem cells into neurons. In this study, we hypothesize that transfection of NGF and Noggin in BMSC treatment of stroke promotes BMSC neuronal differentiation and improves functional outcome after stroke. Adenovirus was used to trasfect NGF and Noggin and the transfection efficiency was measured by Western blot and immunostaining in vitro. The transfected BMSCs with NGF and/or Noggin were administered intravenously at 5 days after middle cerebral artery occlusion (MCAo) in rats. The neurological functional outcome and BMSC migration and differentiation in the ischemic brain were measured. The transplantation of BMSCs with NGF or Noggin elicited neurological functional improvement, promoted BMSCs present in the ischemic brain, and also up-regulated neuro-like cell differentiation as well as increased synaptophysin expression in the ischemic brain compared with nontreatment control animals (P< 0.05). Treatment of stroke with a combination of transfection of NGF and Noggin in BMSCs induced a synergistic effect on improved neurological functional outcome, BMSCs present in the ischemic brain, and synaptophysin expression in the ischemic brain compared with BMSCs transfected with an NGF- or Noggin-alone group (P < 0.05). These data demonstrate that increasing NGF or Noggin expression in BMSCs contributes to brain plasticity after stroke and that a synergistic effect is induced on the coexistence of NGF and Noggin in BMSCs treatment of stroke.     

Neuroprotective effects of human mesenchymal stem cells on dopaminergic neurons through anti-inflammatory action

Parkinson's disease (PD) is a common, progressive neurodegenerative disorder caused by the loss of dopaminergic neurons in the substantia nigra (SN). Numerous studies have provided evidence suggesting that neuroinflammation plays an important role in the pathogenesis of PD. In this study, we used lipopolysaccharide (LPS)-induced in vitro and in vivo inflammation models to investigate whether human mesenchymal stem cells (hMSCs) have a protective effect on the dopaminergic system through anti-inflammatory mechanisms. The hMSC treatment significantly decreased LPS-induced microglial activation, tumor necrosis factor (TNF)-alpha, inducible nitric oxide synthase (iNOS) mRNA expression, and production of NO and TNF-alpha compared with the LPS-only treatment group. In co-cultures of microglia and mesencephalic dopaminergic neurons, hMSC treatment significantly decreased the loss of tyrosine hydroxylase-immunopositive (TH-ip) cells. The hMSC treatment in rats showed that TH-ip neuronal loss induced by LPS stimulation in the SN was considerably decreased and was clearly accompanied by a decrease in activation of microglia, as well as TNF-alpha and iNOS mRNA expression and production of TNF-alpha. These data suggest that hMSCs have a neuroprotective effect on dopaminergic neurons through anti-inflammatory actions mediated by the modulation of microglial activation. Along with various trophic effects and trans-differentiational potency, the anti-inflammatory properties of MSCs could have major therapeutic implications in the treatment of PD.     

Reciprocal Th1 and Th17 regulation by mesenchymal stem cells: Implication for multiple sclerosis

Human mesenchymal stem cells (hMSCs) are being considered for clinical trials of multiple sclerosis (MS). We examined the effects of adult bone marrow‐derived hMSCs on responses of primary human Th1, Th17, and Th1/17 double‐expressing T‐cell subsets, all implicated in MS. As expected, soluble products from hMSCs inhibited Th1 responses; however, Th17 responses were increased. Secretion of interleukin (IL)‐10, considered anti‐inflammatory, was decreased. Pretreating hMSCs with the proinflammatory cytokine IL‐1β accentuated these effects, and caused decreases in the Th1/17 subset. These findings underscore the importance of further preclinical work and immune‐monitoring to define hMSC effects on disease‐relevant immune responses under variable conditions. ANN NEUROL 2010     

Human bone marrow‐derived mesenchymal stem cells induce Th2‐polarized immune response and promote endogenous repair in animal models of multiple sclerosis

Cell‐based therapies are attractive approaches to promote myelin repair. Recent studies demonstrated a reduction in disease burden in mice with experimental allergic encephalomyelitis (EAE) treated with mouse mesenchymal stem cells (MSCs). Here, we demonstrated human bone marrow‐derived MSCs (BM‐hMSCs) promote functional recovery in both chronic and relapsing‐remitting models of mouse EAE, traced their migration into the injured CNS and assayed their ability to modulate disease progression and the host immune response. Injected BM‐hMSCs accumulated in the CNS, reduced the extent of damage and increased oligodendrocyte lineage cells in lesion areas. The increase in oligodendrocytes in lesions may reflect BM‐hMSC‐induced changes in neural fate determination, since neurospheres from treated animals gave rise to more oligodendrocytes and less astrocytes than nontreated neurospheres. Host immune responses were also influenced by BM‐hMSCs. Inflammatory T‐cells including interferon gamma producing Th1 cells and IL‐17 producing Th17 inflammatory cells and their associated cytokines were reduced along with concomitant increases in IL‐4 producing Th2 cells and anti‐inflammatory cytokines. Together, these data suggest that the BM‐hMSCs represent a viable option for therapeutic approaches. © 2009 Wiley‐Liss, Inc.     

Peripheral administration of fetuin-A attenuates early cerebral ischemic injury in rats

Cerebral ischemia-elicited inflammatory responses are driven by inflammatory mediators produced both by central (e.g., neurons and microglia) and infiltrating peripheral immune cells (e.g., macrophage/monocyte), and contribute to the evolution of tissue injury. A ubiquitous molecule, spermine, is released from injured cells, and counter-regulates release of various proinflammatory cytokines. However, the spermine-mediated anti-inflammatory activities are dependent on the availability of fetuin-A, a liver-derived negative acute-phase protein. Using an animal model of focal cerebral ischemia (i.e., permanent middle cerebral artery occlusion, MCAo), we found that levels of fetuin-A in the ischemic brain tissue were elevated in a time-dependent manner, starting between 2 and 6 h, peaking around 24 to 48 h, and returning to baseline 72 h after MCAo. When administered peripherally, exogenous fetuin-A gained entry across the BBB into the ischemic brain tissue, and dose dependently reduced brain infarct volume at 24 h after MCAo. Meanwhile, fetuin-A effectively attenuated (i) ischemia-induced HMGB1 depletion from the ischemic core; (ii) activation of centrally (e.g., microglia) and peripherally derived immune cells (e.g., macrophage/monocytes); and (iii) TNF production in ischemic brain tissue. Taken together, these experimental data suggest that fetuin-A protects against early cerebral ischemic injury partly by attenuating the brain inflammatory response.     

Therapeutic benefit of intracerebral transplantation of bone marrow stromal cells after cerebral ischemia in rats

We tested the hypothesis that bone marrow stromal cells (MSCs) transplanted into the ischemic boundary zone, survive, differentiate and improve functional recovery after middle cerebral artery occlusion (MCAo). MSCs were harvested from adult rats and cultured with or without nerve growth factor (NGF). For cellular identification, MSCs were prelabeled with bromodeoxyuridine (BrdU). Rats (n=24) were subjected to 2 h of MCAo, received grafts at 24 h and were euthanized at 14 days after MCAo. Test groups consisted of: (1) control-MCAo alone (n=8); (2) intracerebral transplantation of MSCs (n=8); (3) intracerebral transplantation of MSCs cultured with NGF (n=8). Immunohistochemistry was used to identify cells from MSCs. Behavioral tests (rotarod, adhesive-removal and modified neurological severity score [NSS]) were performed before and after MCAo. The data demonstrate that MSCs survive, migrate and differentiate into phenotypic neural cells. Significant recovery of somatosensory behavior (p<0.05) and NSS (p<0.05) were found in animals transplanted with MSCs compared with control animals. Animals that received MSCs cultured with NGF displayed significant recovery in motor (p<0.05), somatosensory (p<0.05) and NSS (p<0.05) behavioral tests compared with control animals. Our data suggest that intracerebral transplantation of MSCs may provide a powerful autoplastic therapy for stroke.     

Impact of ageing on biological features of bone marrow stromal cells (BMSC) in cell transplantation therapy for CNS disorders: Functional enhancement by granulocyte‐colony stimulating factor (G‐CSF)

This study was designed to clarify the effects of donor age on biological features of bone marrow stromal cells (BMSC), one of the candidates for cell transplantation therapy for CNS disorders, because many aged patients might require such therapy. This study was also aimed to test whether ex vivo treatments with granulocyte‐colony stimulating factor (G‐CSF) could modify biological properties of BMSC from aged donors and enhance its therapeutic effects in an animal model of traumatic brain injury. The BMSC were harvested from young (6‐week‐old) and aged (100‐week‐old) rats. The ageing significantly increased the senescence‐associated β‐galactosidase (SA‐β‐gal) activity of the cultured BMSC, and decreased their proliferative capacity and production of nerve growth factor (NGF) and brain‐derived neurotrophic factor (BDNF). As the next step, the rats were subjected to brain freezing injury by applying liquid nitrogen onto the neocortex through the thinned skull. The 6‐week BMSC, 100‐week BMSC, G‐CSF‐treated 100‐week BMSC or vehicle were stereotactically injected into the ipsilateral striatum at 7 days post‐injury. Transplantation of the 6‐week BMSC, but not 100‐week BMSC, significantly improved locomotor function. However, treatment of the 100‐week BMSC with 0.1 µmol of G‐CSF significantly improved their proliferation activity and growth factor production, and recovered therapeutic effects in the injured brain. In conclusion, donor age may largely determine biological aspects of BMSC. G‐CSF may contribute to improve the outcome of BMSC transplantation therapy for CNS disorders in aged patients.     

Improvement of neurological deficits by intracerebral transplantation of human adipose tissue-derived stromal cells after cerebral ischemia in rats

Mesenchymal stem cells can be expanded rapidly in vitro and differentiated into multiple mesodermal cell types. In addition, their differentiation into neuron-like cells expressing markers typical for mature neurons has been reported. We isolated human adipose tissue stromal cells (hATSCs) from human liposuction tissues and induced neural differentiation with azacytidine. Following neural induction, hATSCs changed toward neural morphology and displayed expression of MAP2 and GFAP. hATSCs, which were labeled with LacZ adenovirus, were injected into the lateral ventricle of the rat brain. Transplanted cells migrated to various parts of the brain, and ischemic brain injury by middle cerebral artery occlusion (MCAo) increased their migration to the injured cortex. Some of the transplanted cells expressed MAP2 and GFAP. Transplantation of hATSCs improved functional deficits in ischemic brain injury induced by MCAo. Intracerebral grafting of BDNF-transduced hATSCs significantly improved motor recovery of functional deficits in MCAo rats. These data indicate that transplanted hATSCs survive, migrate, and improve functional recovery after stroke and that genetically engineered hATSCs can express biologically active gene products and, therefore, can function as effective vehicles for therapeutic gene transfer to the brain.     

Angiopoietin/Tie2 pathway mediates type 2 diabetes induced vascular damage after cerebral stroke

We investigated the changes and the molecular mechanisms of cerebral vascular damage after stroke in type-2 diabetic (T2DM) mice. Adult male db/db T2DM and wild-type (WT) mice were subjected to transient middle cerebral artery occlusion (MCAo) and sacrificed 24 hours after MCAo. T2DM-mice exhibited significantly increased blood glucose, brain hemorrhagic rate, mortality and cerebrovascular density, but decreased cerebrovascular diameter, arteriolar density and arterial mural cell numbers in the ischemic brain compared with WT mice. The hemorrhagic rate was significantly correlated with the mortality (r = 0.85). T2DM-mice also exhibited increased blood-brain barrier leakage and concomitantly, increased Angiopoietin2, but decreased Angiopoietin1, Tie2 and tight junction protein expression in the ischemic brain. Angiopoietin1 gene expression also significantly decreased in the common carotid artery (CCA) in T2DM-mice compared with WT mice after stroke. To further test the effects of T2DM on cerebrovascular damage, we performed in vitro studies. The capillary-like tube formation of primary cultured mouse brain endothelial cells (MBECs) significantly increased, but artery cell migration in the primary CCA cultures significantly decreased both in Sham and MCAo T2DM-mice compared with the WT mice. Angiopoietin1 treatment significantly increased artery cell migration in T2DM-CCA after MCAo. Tie2-FC, a neutralized Tie2 antibody, significantly decreased artery cell migration in WT-CCA after MCAo. Therefore, decreased Angiopoietin1/Tie2 and increased Angiopoietin2 expression may contribute to diabetes-induced vascular damage after stroke.     

Transplantation of Flk-1+ human bone marrow-derived mesenchymal stem cells promotes angiogenesis and neurogenesis after cerebral ischemia in rats

Transplantation of bone marrow‐derived mesenchymal stem cells (BMSCs) is a potential therapy for cerebral ischemia. Although BMSCs‐induced angiogenesis is considered important for neurological functional recovery, the neurorestorative mechanisms are not fully understood. We examined whether BMSCs‐induced angiogenesis enhances cerebral tissue perfusion and creates a suitable microenvironment within the ischemic brain, which in turn accelerates endogenous neurogenesis and leads to improved functional recovery. Adult female rats subjected to 2 h middle cerebral artery occlusion (MCAO) were transplanted with a subpopulation of human BMSCs from male donors (Flk‐1+ hBMSCs) or saline into the ipsilateral brain parenchymal at 3 days after MCAO. Flk‐1+ hBMSCs‐treated rats exhibited significant behavioral recovery, beginning at 2 weeks after cerebral ischemia compared with controls. Moreover, rats treated with Flk‐1+ hBMSCs showed increased glucose metabolic activity and reduced infarct volume. Flk‐1+ hBMSCs treatment significantly increased the expression of vascular endothelial growth factor and brain‐derived neurotrophic factor, promoted angiogenesis, and facilitated cerebral blood flow in the ischemic boundary zone. Further, Flk‐1+ hBMSCs treatment enhanced proliferation of neural stem/progenitor cells (NSPCs) in the subventricular zone and subgranular zone of the hippocampus. Finally, more NSPCs migrated toward the ischemic lesion and differentiated to mature neurons or glial cells with less apoptosis in Flk‐1+ hBMSCs‐treated rats. These data indicate that angiogenesis induced by Flk‐1+ hBMSCs promotes endogenous neurogenesis, which may cause functional recovery after cerebral ischemia.