Biomedical subjects

Michael Chopp

Publications and source records attributed to Michael Chopp.

125 records · Page 7Linked to original sources

PubMed2002

Bone marrow-derived endothelial progenitor cells participate in cerebral neovascularization after focal cerebral ischemia in the adult mouse.

We investigated whether circulating endothelial progenitor cells contribute to neovascularization after stroke. Donor bone marrow cells obtained from transgenic mice constitutively expressing beta-galactosidase transcriptionally regulated by an endothelial-specific promoter, Tie2, were injected into adult mice. Focal cerebral ischemia was induced by embolic middle cerebral artery (MCA) occlusion and changes of cerebral blood flow (CBF) were measured by perfusion-weighted magnetic resonance imaging (MRI). Laser scanning confocal microscopy (LSCM), immunohistochemistry and X-gal staining were performed. Perfusion-weighted MRI demonstrated increases in CBF around the boundary of an infarct area 1 month after ischemia. Morphological and 3-dimensional image analyses revealed enlarged and thin-walled blood vessels with sprouting or intussusception at the boundary of the ischemic lesion, which closely corresponded to elevated CBF areas detected on perfusion-weighted MRI, indicating the presence of neovascularization. X-gal and double immunostaining demonstrated that Tie2-lacZ-positive cells incorporated into sites of neovascularization at the border of the infarct, and these cells exhibited an endothelial antigenic marker (von Willebrand factor). In addition, bone marrow recipient mice without ischemia showed incorporation of Tie2-lacZ-expressing cells into vessels of the choroid plexus. These data suggest that formation of new blood vessels in the adult brain after stroke is not restricted to angiogenesis but also involves vasculogenesis and that circulating endothelial progenitor cells from bone marrow contribute to the vascular substructure of the choroid plexus.

Animals↗

PubMed2002

Cell proliferation and differentiation from ependymal, subependymal and choroid plexus cells in response to stroke in rats.

We tested the hypothesis that populations of ependymal, subependymal and choroid plexus cells proliferate and differentiate after stroke in adult rats. Rats were subjected to 2 h of middle cerebral artery occlusion (n=70) and euthanized at 1, 2, 4, 7, 14, 21 and 28 days (10 per time point). Hematoxylin and eosin staining and immunostaining were performed using antibodies against bromodeoxyuridine, neuronal nuclear antigen and glial fibrillary acidic protein after stroke. In normal nonischemic rats (n=10), single layers of ependymal and choroid plexus cells do not react with bromodeoxyuridine, neuronal nuclear antigen or glial fibrillary acidic protein. Individual subependymal cells express glial fibrillary acidic protein and bromodeoxyuridine, but not neuronal nuclear antigen. After stroke, increased bromodeoxyuridine reactivity was present in multiple layers of ependymal cells and nodules of subependymal cells and in scattered choroid plexus cells from 2 to 28 days and peaked at 7 days. Bromodeoxyuridine immunoreactivity colocalized with neural phenotypes of neuronal nuclear antigen (approximately 0.1-3.5%) and glial fibrillary acidic protein (approximately 8.6%) immunoreactivity in cells in the ventricular zone and the subventricular zone, as well as in the choroid plexus of the ischemia affected hemisphere. Our data suggest that ependymal, subependymal and choroid plexus cells are potential neural precursor cells in the adult mammalian brain.

Animals↗

PubMed2002

Ischemic cerebral tissue and MCP-1 enhance rat bone marrow stromal cell migration in interface culture.

OBJECTIVE: Intravascular administration of bone marrow stromal cells (MSCs) restores function in animal models of neural injury and neurodegeneration. Adult MSCs administered intravenously to rat migrate and express neural phenotypes in ischemic brain. The aim of the present study was to investigate the mechanisms targeting MSC migration into the ischemic brain. METHODS: Monocyte chemoattractant protein-1 (MCP-1), a chemoattractant factor, was measured in rat ischemic brain at various time points after middle cerebral artery occlusion (MCAo) using a specific enzyme-linked immunosorbent assay system (ELISA). In addition, using a microchemotaxis chamber, we measured whether ischemic brain tissue extracts induce migration of MSCs and whether brain tissue extracts incubated with antibodies against MCP-1 reduce MSC migration. RESULT: Our data indicate that ischemic brain MCP-1 levels significantly increase from 6 hours, peak at 48 hours after MCAo (p < 0.05), and thereafter gradually decrease. Brain tissue extract at 6 hours, 24 hours, and 48 hours after MCAo significantly increase MSC migration across the membrane of the microchemotaxis chamber compared to normal tissue (p < 0.05). However, when the ischemic brain tissue extracts are incubated with antibody against MCP-1, MSC migration is significantly reduced at 24 hours and 48 hours after MCAo compared to extracts without this antibody (p < 0.05). CONCLUSION: Our data suggest that MCP-1 contributes to MSC migration into the ischemic brain tissue environment.

Animals↗

PubMed2002

Vascular endothelial growth factor and angiopoietins in focal cerebral ischemia.

A growing body of evidence indicates that vascular growth factors and their receptors are activated after stroke, and these factors may contribute to ischemic cell damage and to angiogenesis during recovery from stroke. In this review, we focus on recent evidence for roles of vascular endothelial growth factor (VEGF) and angiopoietin 1 (Ang 1) in blood-brain barrier (BBB) leakage and angiogenesis after focal cerebral ischemia.

Angiopoietin-1↗

PubMed2002

Treatment of neural injury with marrow stromal cells.

We describe our preclinical studies on the use of bone-marrow stromal cells (MSC; an uncharacterised mixed population of plastic-adherent cells) in the treatment of neural injury. These cells obtained from donor rats or human beings have been directly transplanted into brain or administered intra-arterially or intravenously. MSC selectively target injured tissue and promote functional recovery. Signals that target inflammatory cells to injured tissue probably direct MSC to injury sites. Although some MSC express proteins typical of neural cells, the possibility that benefit is derived by replacement of infarcted tissue with differentiated MSC is highly unlikely. MSC activate endogenous restorative responses in injured brain, which include angiogenesis, neurogenesis, and synaptogenesis. Given the robust therapeutic benefit of these cells in the treatment of experimental neural injury, and the fact that MSC have been used in the treatment of other human disease, there is justification for further preclinical studies leading to clinical trials for the treatment of neural injury such as stroke.

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PubMed2002

Ischemic rat brain extracts induce human marrow stromal cell growth factor production.

Intravenous administration of human bone marrow stromal cells (hMSCs) after middle cerebral artery occlusion (MCAo) in rats provides functional benefit. We tested the hypothesis that these functional benefits are derived in part from hMSC production of growth and trophic factors. Quantitative sandwich enzyme-linked immunosorbent assay (ELISA) of hMSCs cultured with normal and MCAo brain extracts were performed. hMSCs cultured in supernatant derived from ischemic brain extracts increased production of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). These neurotrophins and angiogenic growth factors increased in a post-ischemia time-dependent manner. The hMSC capacity to increase expression of growth and trophic factors may be the key to the benefit provided by transplanted hMSCs in the ischemic brain.

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PubMed2002

MCP-1, MIP-1, IL-8 and ischemic cerebral tissue enhance human bone marrow stromal cell migration in interface culture.

Bone marrow stromal cells (MSCs) administered intravenously are effective in reducing neurological deficits after stroke in the rodent. These cells appear to selectively migrate and express neural phenotypes in ischemic brain. To elucidate the mechanisms targeting MSC migration into the ischemic brain, we measured, using a microchemotaxis chamber, the effect of select chemotactic factors and cytokines expressed in injured brain, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha) and interleukin-8 (IL-8), on migration of human bone marrow stromal cells (hMSCs). In addition, we investigated whether tissue extracts prepared from rat ischemic brain at various times after middle cerebral artery occlusion (MCAo) induce migration of hMSCs. Our data indicate that MCP-1, MIP-1alpha and IL-8 enhance the migration of hMSCs. Ischemic brain tissue extracts at 24, 48 h and 1 week after ischemia significantly increase hMSC migration across the membrane compared to non-ischemic tissue (p<0.05). These data indicate that hMSCs are targeted by inflammatory chemotactic agents and cytokines and that ischemic brain attracts hMSCs.

Animals↗

PubMed2002

Intracerebral transplantation of marrow stromal cells cultured with neurotrophic factors promotes functional recovery in adult rats subjected to traumatic brain injury.

This study was designed to examine the effects of bone marrow stromal cells (MSCs) cultured in vitro with or without neurotrophic factors transplanted into adult male Wistar rats after traumatic brain injury (TBI). MSCs harvested from donor Wistar rats were cultured with either the culture medium containing brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) or the same culture media without these factors. Control and experimental animals were then traumatized by a controlled cortical impact. One day after the impact, either the placebo or the washed MSCs (1 x 10(6)) cultured with or without NGF and BDNF were transplanted adjacent to the site of injury. In addition, a nontreated group of rats was employed. Motor function of the animals was evaluated by the Rotarod test both before and after the injury. All animals were sacrificed 8 days after TBI, and the brain sections were stained by H&E as well as for immunohistochemistry. MSCs survived and migrated toward the injury site. The group treated with MSCs cultured with BDNF and NGF had a significantly higher number of engrafted cells than the group treated with MSCs cultured without BDNF and NGF (6.3 x 10(4) +/- 4250 compared to 4.1 x 10(4) +/- 3684; p < 0.05). In both groups, some transplanted MSCs showed positive staining for astrocytic (GFAP) and neuronal markers (Neu N and MAP-2). The groups treated with MSCs had better motor function than the groups receiving no treatment or receiving the placebo (PBS; p < 0.05); however, the improvement reached statistical significance only in the group treated with MSCs cultured with neurotrophic factors. These data suggest that more robust motor function described in rats subjected to TBI and treated with intracerebral transplantation of MSCs was achieved by the use of MSCs cultured with neurotrophic factors.

Animals↗

PubMed2002

Correlation of VEGF and angiopoietin expression with disruption of blood-brain barrier and angiogenesis after focal cerebral ischemia.

In an effort to elucidate the molecular mechanisms underlying cerebral vascular alteration after stroke, the authors measured the spatial and temporal profiles of blood-brain barrier (BBB) leakage, angiogenesis, vascular endothelial growth factor (VEGF), associated receptors, and angiopoietins and receptors after embolic stroke in the rat. Two to four hours after onset of ischemia, VEGF mRNA increased, whereas angiopoietin 1 (Ang 1) mRNA decreased. Three-dimensional immunofluorescent analysis revealed spatial coincidence between increases of VEGF immunoreactivity and BBB leakage in the ischemic core. Two to 28 days after the onset of stroke, increased expression of VEGF/VEGF receptors and Ang/Tie2 was detected at the boundary of the ischemic lesion. Concurrently, enlarged and thin-walled vessels were detected at the boundary of the ischemic lesion, and these vessels developed into smaller vessels via sprouting and intussusception. Three-dimensional quantitative analysis of cerebral vessels at the boundary zone 14 days after ischemia revealed a significant (P < 0.05) increase in numbers of vessels (n = 365) compared with numbers (n = 66) in the homologous tissue of the contralateral hemisphere. Furthermore, capillaries in the penumbra had a significantly smaller diameter (4.8 +/- 2.0 microm) than capillaries (5.4 +/- 1.5 microm) in the homologous regions of the contralateral hemisphere. Together, these data suggest that acute alteration of VEGF and Ang 1 in the ischemic core may mediate BBB leakage, whereas upregulation of VEGF/VEGF receptors and Ang/Tie2 at the boundary zone may regulate neovascularization in ischemic brain.

Angiopoietin-1↗

PubMed2002

Magnetic resonance imaging characterization of hemorrhagic transformation of embolic stroke in the rat.

Intracranial hemorrhage is a critical factor when considering efficacy and safety of thrombolytic intervention after thromboembolic stroke. This study tested whether magnetic resonance imaging could identify tissue for hemorrhagic transformation after the onset of embolic stroke. Rats subjected to embolic stroke with and without recombinant tissue-type plasmogen activator (rt-PA) treatment were followed-up with magnetic resonance imaging using the inverse of the apparent forward transfer rate for magnetization transfer (k(inv)), gadolinium-chelate contrast-enhanced magnetic resonance imaging, and diffusion-, perfusion-, and T2-weighted imaging. Rats with embolic stroke either were treated with rt-PA 1 (n = 16) or 4 hours (n = 13) after stroke onset or were not treated (n = 15). From these groups, at total of 17 rats had intracerebral hemorrhage. Tissue progressing to hemorrhage and adjacent to the site of hemorrhage was analyzed to identify magnetic resonance imaging markers that characterize hemorrhagic transformation. The parameter maps of k(inv) and contrast-enhanced magnetic resonance imaging showed greater sensitivity in the detection of tissue destined for hemorrhagic transformation compared with the apparent diffusion coefficient of water (ADCw) and CBF. In tissue not destined to undergo hemorrhagic transformation, k(inv) maps and contrast-enhanced magnetic resonance imaging exhibited small increases in k(inv) and contrast-enhanced magnetic resonance imaging signal intensity in the area encompassing the territory supplied by the middle cerebral artery. In contrast, large increases in k(inv) and in signal intensity in the contrast-enhanced magnetic resonance images were detected in the region where gross hemorrhage was confirmed histologically. The values of k(inv), T2, and signal intensity in the contrast-enhanced magnetic resonance images were significantly higher in the region destined for hemorrhagic transformation (k(inv), P < or = 0.033 3-24 hours after embolization; T2, P < or = 0.037 24-48 hours; contrast-enhanced magnetic resonance imaging, P < 0.05 4-7 hours) compared with the nonhemorrhagic transformation ischemic region or in the contralateral homologous regions after onset of ischemia. Of these methods, k(inv) shows the most sensitivity in the detection of hemorrhagic transformation soon after embolization. The authors' data suggest that k(inv) and contrast-enhanced magnetic resonance imaging are potentially important methodologies for detecting tissue destined for hemorrhagic transformation.

Animals↗

PubMed2002

Sildenafil (Viagra) induces neurogenesis and promotes functional recovery after stroke in rats.

BACKGROUND AND PURPOSE: We tested the hypothesis that sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, promotes functional recovery and neurogenesis after stroke. METHODS: Male Wistar rats were subjected to embolic middle cerebral artery occlusion. Sildenafil (Viagra) was administered orally for 7 consecutive days starting 2 or 24 hours after stroke onset at doses of 2 or 5 mg/kg per day. Ischemic rats administered the same volume of tap water were used as a control group. Functional outcome tests (foot-fault, adhesive removal) were performed. Rats were killed 28 days after stroke for analysis of infarct volume and newly generated cells within the subventricular zone and the dentate gyrus. Brain cGMP levels, expression of PDE5, and localized cerebral blood flow were measured in additional rats. RESULTS: Treatment with sildenafil significantly (P<0.05) enhanced neurological recovery in all tests performed. There was no significant difference of infarct volume among the experimental groups. Treatment with sildenafil significantly (P<0.05) increased numbers of bromodeoxyuridine-immunoreactive cells in the subventricular zone and the dentate gyrus and numbers of immature neurons, as indicated by betaIII-tubulin (TuJ1) immunoreactivity in the ipsilateral subventricular zone and striatum. The cortical levels of cGMP significantly increased after administration of sildenafil, and PDE5 mRNA was present in both nonischemic and ischemic brain. CONCLUSIONS: Sildenafil increases brain levels of cGMP, evokes neurogenesis, and reduces neurological deficits when given to rats 2 or 24 hours after stroke. These data suggest that this drug that is presently in the clinic for sexual dysfunction may have a role in promoting recovery from stroke.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed2002

Multiparametric MRI ISODATA ischemic lesion analysis: correlation with the clinical neurological deficit and single-parameter MRI techniques.

BACKGROUND AND PURPOSE: The purpose of this study was to show that the computer segmentation algorithm Iterative Self-Organizing Data Analysis Technique (ISODATA), which integrates multiple MRI parameters (diffusion-weighted imaging [DWI], T2-weighted imaging [T2WI], and T1-weighted imaging [T1WI]) into a single composite image, is capable of defining the ischemic lesion in a time-independent manner equally as well as the MRI techniques considered the best for each phase after stroke onset (ie, perfusion weighted imaging [PWI] and DWI for the acute phase and T2WI for the outcome phase). METHODS: We measured MRI parameters of PWI, DWI, T2WI, and T1WI from patients at the acute phase (<30 hours) and DWI, T2WI, and T1WI at the outcome phase (3 months) of ischemic stroke. The clinical neurological deficit was graded with the National Institutes of Health Stroke Scale (NIHSS). We compared the ISODATA lesion size with the PWI, DWI, and T2WI lesion sizes measured within the same slice at each phase. The lesion sizes were also correlated with NIHSS score of each phase. RESULTS: We included 11 patients; 9 (82%) were women, and 7 (64%) were black. The mean+/-SD age was 65.5+/-9.3 years (range, 45 to 82 years). The median NIHSS score was 15 (minimum, 4; maximum, 24)at the acute phase and 3 (minimum, 0; maximum, 22) at the outcome phase. The median time interval from stroke symptom onset to the acute MRI study was 10 hours (range, 6 to 29 hours), and the mean time interval to the outcome study was 93+/-11 days (range, 72 to 106 days). In the acute phase, the ISODATA lesion size had high correlation with the PWI lesion size (r=0.95; 95% CI, 0.89 to 0.98; P<0.0001), DWI lesion size (r=0.83; 95% CI, 0.66 to 0.92; P<0.0001), and T2WI lesion size (r=0.67; 95% CI, 0.39 to 0.84; P=0.008) and moderate correlation with NIHSS score (r=0.59; 95% CI, 0.02 to 0.88; P=0.06). In the outcome phase, the ISODATA lesion size had high correlation with the T2WI lesion size (r=0.97; 95% CI, 0.94 to 0.99; P<0.0001) and NIHSS score (r=0.78; 95% CI, 0.34 to 0.94; P=0.004). CONCLUSIONS: The integrated ISODATA method can identify and characterize the ischemic lesion independently of time elapsed since stroke onset. The ISODATA lesion size highly correlates with the PWI and DWI lesion size in the acute phase and with the T2WI lesion size in the outcome phase of ischemic stroke, as well as with the clinical neurological status of the patient.

Aged↗

PubMed2002

Neural and marrow-derived stromal cell sphere transplantation in a rat model of traumatic brain injury.

OBJECT: This study was designed to investigate the effect of treatment with a novel composite material consisting of embryonic neurospheres and bone marrow-derived stromal cell spheres (NMSCSs) in a rat model of traumatic brain injury (TBI). METHODS: The NMSCS composite was injected into the TBI contusion site 24 hours after injury, and all rats were killed on Day 14 after the transplantation. The Rotarod test and the neurological severity score were used to evaluate neurological function. The transplanted NMSCS was analyzed in recipient rat brains by using histological staining and laser scanning confocal microscopy. The lesion volumes in the brains were also calculated using computer image analysis. CONCLUSIONS: Rats that received NMSCS transplants had reduced lesion volume and showed improved motor and neurological function when compared with control groups 14 days after the treatment. These results suggest that transplantation of this novel biological material (NMSCS) may be useful in the treatment of TBI.

Animals↗

PubMed2002

Intravenous administration of human umbilical cord blood reduces neurological deficit in the rat after traumatic brain injury.

We measured the effect of treatment of traumatic brain injury (TBI) in the rat with human umbilical cord blood (HUCB) administered i.v.. HUCB cells were injected into the tail vein 24 h after TBI and the rats were sacrificed at day 28 after the treatment. The Rotarod test and the neurological severity score (NSS) were used to evaluate neurological function. The distribution of the donor cells in the brain, heart, lung, kidney, liver, spleen, bone marrow, and muscle were analyzed in recipient rats using immunohistochemical staining and laser confocal microscopy. HUCB cells injected i.v. significantly reduced motor and neurological deficits compared with control groups by day 28 after the treatment. The cells preferentially entered the brain and migrated into the parenchyma of the injured brain and expressed the neuronal markers, NeuN and MAP-2, and the astrocytic marker, GFAP. Some HUCB cells integrated into the vascular walls within the boundary zone of the injured area. Our data suggest that i.v. administration of HUCB may be useful in the treatment of TBI.

Animals↗

PubMedDate not supplied

Biologic transplantation and neurotrophin-induced neuroplasticity after traumatic brain injury.

OBJECTIVE: In this review, we analyze progress in the treatment of traumatic brain injury with neurotrophins, growth factors and cell and tissue neurotransplantation. The primary objective of these therapies is to reduce neurologic deficits associated with the trauma by inducing neuroplasticity. These therapies are restorative and not necessarily neuroprotective. MAIN OUTCOME MEASURES: An extensive literature on administration of neurotrophics factors and cell and tissue cerebral transplantation is reviewed. The effects of these therapeutic approaches on brain biochemical, molecular, cellular, and tissue responses are summarized. CONCLUSION: The cumulative data indicate that cell therapy shows substantial promise in the treatment of neural injury.

Brain Injuries↗

PubMedDate not supplied

Bone marrow-derived mesenchymal stromal cells accelerate wound healing in the rat.

Bone marrow-derived mesenchymal stromal cells (BMSCs) are multipotential stem cells capable of differentiation into numerous cell types, including fibroblasts, cartilage, bone, muscle, and brain cells. BMSCs also secrete a large number of growth factors and cytokines that are critical to the repair of injured tissues. Because of the extraordinary plasticity and the ability of syngeneic or allogeneic BMSCs to secrete tissue-repair factors, we investigated the therapeutic efficacy of BMSCs for healing of fascial and cutaneous incisional wounds in Sprague-Dawley rats. Systemic administration of syngeneic BMSCs (2 x 10(6)) once daily for 4 days or a single treatment with 5 x 10(6) BMSCs 24 hours after wounding significantly increased the wound bursting strength of fascial and cutaneous wounds on days 7 and 14 postwounding. Wound healing was also significantly improved following injection of BMSCs locally at the wound site. Furthermore, allogeneic BMSCs were as efficient as syngeneic BMSCs in promoting wound healing. Administration of BMSCs labeled with iron oxides/1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate fluorescent dye revealed that systemically administered BMSCs engraft to the wound. The increase in the tensile strength of wounds treated with BMSCs was associated with increased production of collagen in the wound. In addition, BMSC treatment caused more rapid histologic maturation of wounds compared with untreated wounds. These data suggest that cell therapy with BMSCs has the potential to augment healing of surgical and cutaneous wounds.

Animals↗

PubMedDate not supplied

Combination of surgical resection and photodynamic therapy of 9L gliosarcoma in the nude rat.

The objective of the present study was to investigate the treatment of 9L gliosarcoma brain tumor in the rat with the combination of surgical resection and photodynamic therapy (PDT). Nude rats with intracranial 7-day-old 9L gliomas were randomly subjected to no treatment, PDT alone (Photofrin: 2 mg kg(-1), optical: 80 J cm(-2)), surgical resection alone or resection combined with 2 mg kg(-1) Photofrin-mediated PDT at an optical dose of 80 J cm(-2). All animals were sacrificed 14 days after tumor implantation. Hematoxylin-and-eosin and immunohistochemical stainings were performed to assess the tumor volume and the expression of vascular endothelial growth factor (VEGF) in the brain adjacent to the tumor (BAT) as well as the tumor cell apoptosis and proliferation. Our data show that both surgical resection alone and PDT alone significantly decreased tumor volume, but furthermore, surgical resection combined with PDT significantly reduced the tumor volume and reduced local tumor infiltration compared to either surgical resection or PDT treatment alone. PDT treatment with or without resection increased tumor apoptosis, but resection alone did not alter the tumor cell apoptosis compared with a nontreatment control group. Both surgical resection alone and PDT alone induced a significant increase in VEGF expression in the BAT; however intraoperative PDT did not further increase VEGF expression, compared with surgery alone or PDT alone. No significant differences were found in tumor cell proliferation as indicated by Ki67 immunoreactivity among the four groups. Our results suggest that PDT enhances the efficacy of surgical resection in the management of malignant gliomas without increasing VEGF expression in the BAT.

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