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Biomedical subjects

M Neeman

Publications and source records attributed to M Neeman.

At least 19 recordsLinked to original sources
PubMed2005

Labeling fibroblasts with biotin-BSA-GdDTPA-FAM for tracking of tumor-associated stroma by fluorescence and MR imaging.

Fibroblasts at the tumor-host interface can differentiate into myofibroblasts and pericytes, and contribute to the guidance and stabilization of endothelial sprouts. After intravenous administration of biotin-BSA-GdDTPA-FAM in mice with subcutaneous MLS human ovarian carcinoma tumors, the distribution of the macromolecular MRI/optical contrast material was confined to blood vessels in normal tissues, while it co-registered with alphaSMA-positive stroma tracks within the tumor. These alphaSMA-positive tumor-associated myofibroblasts and pericytes showed uptake of the contrast material into intracellular granules. We evaluated the use of this contrast material for in vitro labeling of tumor fibroblasts as an approach for tracking their involvement in angiogenesis. Fluorescence microscopy demonstrated internalization of the contrast material, and MRI revealed a significant increase in the R(1) relaxation rate of labeled fibroblasts. R(1) not only remained elevated for 2 weeks in culture, it also increased with cell proliferation, indicating prolonged retention of the contrast material and subsequent intracellular processing and redistribution of the material, and thereby enhancing MR contrast. Moreover, cells that were labeled ex vivo with MR contrast material and co-inoculated with tumor cells in mice were detected in vivo by MRI. Uptake of the contrast material was suppressed by nystatin, suggesting internalization by caveolae-mediated endocytosis. This study shows that labeling of fibroblasts with biotin-BSA-GdDTPA-FAM is feasible and would allow noninvasive in vivo tracking of fibroblasts during tumor angiogenesis and vessel maturation.

Animals↗
PubMed2001

Diffusion anisotropy MRI for quantitative assessment of recovery in injured rat spinal cord.

Spinal cord injury and its devastating consequences are the subject of intensive research aimed at reversing or at least minimizing functional loss. Research efforts focus on either attenuating the post-injury spread of damage (secondary degeneration) or inducing some regeneration. In most of these studies, as well as in clinical situations, evaluation of the state of the injured spinal cord poses a serious difficulty. To address this problem, we carried out a diffusion-weighted MRI experiment and developed an objective routine for quantifying anisotropy in injured rat spinal cords. Rats were subjected to a contusive injury of the spinal cord caused by a controlled weight drop. Untreated control rats were compared with rats treated with T cells specific to the central nervous system self-antigen myelin basic protein, a form of therapy recently shown to be neuroprotective. After the rats were killed their excised spinal cords were fixed in formalin and imaged by multislice spin echo MRI, using two orthogonal diffusion gradients. Apparent diffusion coefficient (ADC) values and anisotropy ratio (AI) maps were extracted on a pixel-by-pixel basis. The calculated sum of AI values (SAI) for each slice was defined as a parameter representing the total amount of anisotropy. The mean-AI and SAI values increased gradually with the distance from the site of the lesion. At the site itself, the mean-AI and SAI values were significantly higher in the spinal cords of the treated animals than in the controls (P = 0.047, P = 0.028, respectively). These values were consistent with the score of functional locomotion. The difference was also manifested in the AI maps, which revealed well-organized neural structure in the treated rats but not in the controls. The SAI values, AI histograms, and AI maps proved to be useful parameters for quantifying injury and recovery in an injured spinal cord. These results encourage the development of diffusion anisotropy MRI as a helpful approach for quantifying the extent of secondary degeneration and measuring recovery after spinal cord injury. Magn Reson Med 45:1-9, 2001.

Animals↗
PubMed2001

In vivo BOLD contrast MRI mapping of subcutaneous vascular function and maturation: validation by intravital microscopy.

Bold contrast MRI was applied for mapping vascular maturation in tumor- and wound-induced skin angiogenesis using the response of mature vessels to hypercapnia (inhalation of air vs. air 5% CO(2)) and the response of all vessels to hyperoxia (air 5% CO(2) vs. oxygen 5% CO(2) (carbogen)). MRI signal enhancement with hypercapnia was reduced in centered vs. linear phase encoding, suggesting increased blood flow. However, intravital microscopy demonstrated constriction of arterioles and reduced flux and density of red blood cells in mature capillaries with hypercapnia, with no change in the diameter of wound-induced neovasculature. The discrepancy in flow between MRI and intravital microscopy is consistent with increased plasma flow and reduced hematocrit. Hyperoxia resulted in increased blood oxygenation and constriction of all vessels. These results provide a hemodynamic explanation for the selective registration of MRI response to hypercapnia with mature vessels and the response to hyperoxia with total vascular function.

Animals↗
PubMed2001

Compartmentation of intracellular water in multicellular tumor spheroids: diffusion and relaxation NMR.

Diffusion and relaxation of water in C6 glioma and MLS human ovarian carcinoma spheroids were measured from 1D projections acquired using a 2D diffusion-relaxation correlation pulse sequence and processed by non-negative least-square (NNLS) analysis. Systematic underestimation of I(s) and ADC(s) were observed for I(s)/(I(s) + I(f)) < 0.001. In the presence of spheroids, two apparent diffusion coefficient (ADC) compartments were observed, where ADC(f), ADC(s), and I(f), I(s) are the respective ADCs and signal intensities of the fast and slow compartments. These compartments differed also in their T(2) relaxation (ADC(s) = 0.5-0.74 x 10(-5) cm(2)/s, T(2) = 36-45 ms; and ADC(f) = 2.2-2.8 x 10(-5) cm(2)/s, T(2) = 280-316 ms). The two ADC compartments and the slow T(2) compartment were consistent with slow exchange. The fast T(2) compartment showed a drift with diffusion weighting, suggesting that it represents water exchanging between compartments that differ in their ADC and T(2). Both ADC(s) and I(s) were markedly attenuated with increasing diffusion time (Delta) for Delta < 100 ms, and increased at longer Delta. These results are consistent with restricted diffusion and fast relaxation of intracellular water for short diffusion time (T(1)' = 46.6 ms), and with predominant extracellular contribution to ADC(s) at longer diffusion times. Magn Reson Med 46:68-77, 2001.

Animals↗
PubMed2001

Magnetic resonance imaging applications in the evaluation of tumor angiogenesis.

Angiogenesis, the growth of new blood vessels, is a critical component in the development of solid tumors. Over the last decade, progress in the study of the biology of angiogenesis has led to identification of a large number of molecules that promote, participate, and regulate the growth of new vessels in normal tissue and in tumors. Consequently, many new targets for suppression of angiogenesis have been identified and are now at various stages of development and evaluation in clinical trials. Magnetic resonance imaging (MRI) provides an attractive tool for in vivo analysis of the basic biology of angiogenesis, for preclinical evaluation of the activity of a number of potential antiangiogenic agents, as well as for clinical detection, diagnosis, and prognosis. One of the features of MRI is the wide range of physiologic parameters by which angiogenesis can be imaged. This review presents the biological basis of angiogenesis with emphasis on characteristics of the neovasculature that can be used for imaging, followed by an overview of the MRI approaches that are being evaluated for the analysis of tumor angiogenesis.

Blood Volume↗
PubMed2001

Antivascular treatment of solid melanoma tumors with bacteriochlorophyll-serine-based photodynamic therapy.

We describe here a strategy for photodynamic eradication of solid melanoma tumors that is based on photo-induced vascular destruction. The suggested protocol relies on synchronizing illumination with maximal circulating drug concentration in the tumor vasculature attained within the first minute after administrating the sensitizer. This differs from conventional photodynamic therapy (PDT) of tumors where illumination coincides with a maximal concentration differential of sensitizer in favor of the tumor, relative to the normal surrounding tissue. This time window is often achieved after a delay (3-48 h) following sensitizer administration. We used a novel photosensitizer, bacteriochlorophyll-serine (Bchl-Ser), which is water soluble, highly toxic upon illumination in the near-infrared (lambda max 765-780 nm) and clears from the circulation in less than 24 h. Nude CD1 mice bearing malignant M2R melanotic melanoma xenografts (76-212 mm3) received a single complete treatment session. Massive vascular damage was already apparent 1 h after treatment. Changes in vascular permeability were observed in vivo using contrast-enhanced magnetic resonance imaging (MRI), with the contrast reagent Gd-DTPA, by shortening spin-spin relaxation time because of hemorrhage formation and by determination of vascular macromolecular leakage. Twenty-four hours after treatment a complete arrest of vascular perfusion was observed by Gd-DTPA-enhanced MRI. Histopathology performed at the same time confirmed primary vascular damage with occlusive thrombi, hemorrhage and tumor necrosis. The success rate of cure of over 80% with Bchl-Ser indicates the benefits of the short and effective treatment protocol. Combining the sensitizer administration and illumination steps into one treatment session (30 min) suggests a clear advantage for future PDT of solid tumors.

Animals↗
PubMed2000

Passive or active immunization with myelin basic protein promotes recovery from spinal cord contusion.

Partial injury to the spinal cord can propagate itself, sometimes leading to paralysis attributable to degeneration of initially undamaged neurons. We demonstrated recently that autoimmune T cells directed against the CNS antigen myelin basic protein (MBP) reduce degeneration after optic nerve crush injury in rats. Here we show that not only transfer of T cells but also active immunization with MBP promotes recovery from spinal cord injury. Anesthetized adult Lewis rats subjected to spinal cord contusion at T7 or T9, using the New York University impactor, were injected systemically with anti-MBP T cells at the time of contusion or 1 week later. Another group of rats was immunized, 1 week before contusion, with MBP emulsified in incomplete Freund's adjuvant (IFA). Functional recovery was assessed in a randomized, double-blinded manner, using the open-field behavioral test of Basso, Beattie, and Bresnahan. The functional outcome of contusion at T7 differed from that at T9 (2.9+/-0.4, n = 25, compared with 8.3+/-0.4, n = 12; p<0.003). In both cases, a single T cell treatment resulted in significantly better recovery than that observed in control rats treated with T cells directed against the nonself antigen ovalbumin. Delayed treatment with T cells (1 week after contusion) resulted in significantly better recovery (7.0+/-1; n = 6) than that observed in control rats treated with PBS (2.0+/-0.8; n = 6; p<0.01; nonparametric ANOVA). Rats immunized with MBP obtained a recovery score of 6.1+/-0.8 (n = 6) compared with a score of 3.0+/-0.8 (n = 5; p<0.05) in control rats injected with PBS in IFA. Morphometric analysis, immunohistochemical staining, and diffusion anisotropy magnetic resonance imaging showed that the behavioral outcome was correlated with tissue preservation. The results suggest that T cell-mediated immune activity, achieved by either adoptive transfer or active immunization, enhances recovery from spinal cord injury by conferring effective neuroprotection. The autoimmune T cells, once reactivated at the lesion site through recognition of their specific antigen, are a potential source of various protective factors whose production is locally regulated.

Animals↗
PubMed2000

Preclinical MRI experience in imaging angiogenesis.

Magnetic resonance imaging (MRI) provides a range of non-invasive measures for visualization of tumor angiogenesis in the clinic as well as in experimental tumor models. MRI methods were developed for assessment of spatial and temporal changes in perfusion, blood volume fraction, vascular permeability, vascular function, vascular maturation, vessel diameter and tortuosity. Molecular targeted contrast agents were used for mapping specific markers of neovasculature. These approaches were applied for analysis of a number of regulatory mechanisms controlling tumor angiogenesis and for preclinical evaluation of tumor response to antiangiogenic agents.

Animals↗
PubMed2000

Hyaluronic acid as an anti-angiogenic shield in the preovulatory rat follicle.

Angiogenesis in the preovulatory follicle is confined to the theca cell layers, and penetration of capillaries through the basement membrane into the granulosa cell layers does not occur until after ovulation. However, elevated expression of the angiogenic growth factor (VEGF) has been reported in the cumulus cells surrounding the oocyte, which are expelled from the follicle during ovulation. This spatial and temporal discrepancy between VEGF expression and angiogenesis was studied here in the rat ovarian follicle, and we showed that cumulus cells secrete to the follicular fluid, in addition to VEGF, material with antiangiogenic activity that blocks endothelial cell proliferation, migration, and capillary formation in vitro. Hyaluronic acid produced by the cumulus cells can account for this antiangiogenic activity. Degradation of hyaluronic acid by hyaluronidase restored proliferation and migration of endothelial cells directed toward the cumulus. Inhibition of hyaluronic acid synthesis with 6-diazo-5-oxo-1-norleucine restored endothelial proliferation and migration in vitro, and it also resulted in early penetration of capillaries across the follicular basement membrane in vivo. These results support the role of hyaluronic acid produced by the cumulus cells as a high-molecular-weight, antiangiogenic shield that prevents premature vascularization of the preovulatory follicle by blocking endothelial cell migration and proliferation.

Animals↗
PubMed1999

In vivo prediction of vascular susceptibility to vascular susceptibility endothelial growth factor withdrawal: magnetic resonance imaging of C6 rat glioma in nude mice.

One of the hallmarks of tumor neovasculature is the prevalence of immature vessels manifested by the low degree of recruitment of vascular mural cells such as pericytes and smooth muscle cells. This difference in the architecture of the vascular bed provides an important therapeutic window for inflicting tumor-selective vascular damage. Here we demonstrate the application of gradient echo magnetic resonance imaging (MRI) for noninvasive in vivo mapping of vascular maturation, manifested by the ability of mature vessels to dilate in response to elevated levels of CO2. Histological alpha-actin staining showed a match between dilating vessels detected by MRI and vessels coated with smooth muscle cells. Switchable, vascular endothelial growth factor (VEGF)-overexpressing tumors (C6-pTET-VEGF rat glioma s.c. tumors in nude mice) displayed high vascular function and significant vascular damage upon VEGF withdrawal. However, damage was restricted to nondilating vessels, whereas mature dilating tumor vessels were resistant to VEGF withdrawal. Thus, MRI provides in vivo visualization of vascular maturity and prognosis of vascular obliteration induced by VEGF withdrawal.

Actins↗
PubMed1999

Spatial and temporal modulation of perfusion in the rat ovary measured by arterial spin labeling MRI.

The hemodynamic changes triggered by luteinizing hormone/human chorionic gonadotropin (LH/hCG) in ovaries of immature pregnant mare serum gonadotropins (PMSG)-primed female Wistar rats were followed by pulsed arterial spin labeling magnetic resonance imaging. Decreased perfusion was monitored in the first 2 hours after administration of hCG followed by a transient significant rise in perfusion. Subsequently, constant ovarian perfusion of 10.9 +/- 4.3 mL min(-1) g(-1) was maintained during the exponential increase in ovarian volume. However, ovarian perfusion was not uniform, and prior to ovulation poorly perfused regions were detected that were assigned to the follicular fluid in preovulatory follicles. This result implied that in the time scale of seconds, corresponding to the T1 relaxation time of water in the follicular fluid, exchange of arterial water with water in the follicular fluid was negligible. Along with the drop in the levels of high-energy phosphate metabolites detected by 31P nuclear magnetic resonance spectroscopy and the shift to glycolytic metabolism, these results support the hypothesis that physiological hypoxia could play a role in large preovulatory follicles as part of the normal ovarian cycle.

Animals↗
PubMed1999

Perfusion of the rat ovary: application of pulsed arterial spin labeling MRI.

Pulsed arterial spin labeling was used for mapping ovarian perfusion and measurement of blood velocity in the ovarian artery. Arterial blood was tagged upstream by pulsed slice selective saturation, and saturation transfer due to perfusion was monitored within the rat ovary. The velocity of arterial blood was determined from the dependence of the saturation transfer on the thickness of the saturation slice and the delay between successive saturation pulses. This method allows for determination of arterial velocity, even when the artery itself is not identified in the images. The arterial velocity of blood to the ovary was 3.6+/-0.6 cm x s(-1). The mean ovarian perfusion was 8.7+/-3.5 ml x min(-1) x g(-1) during the surge of luteinizing hormone and 5.9+/-3.0 ml min(-1) x g(-1) during the luteal phase. Arterial labeling can thus be used for following vascular remodeling and angiogenesis during the ovarian cycle by MRI.

Animals↗
PubMed1999

Stimulation of tumour growth by wound-derived growth factors.

The goal of this work was to determine the molecular basis for the induction of tumour vascularization and progression by injury. Magnetic resonance imaging (MRI) studies demonstrated that administration of wound fluid derived from cutaneous injuries in pigs reduced the lag for vascularization and initiation of growth of C6 glioma spheroids, implanted in nude mice, and accelerated tumour doubling time. The former effect can be attributed to the angiogenic capacity of wound fluid as detected in vivo by MRI, and in vitro in promoting endothelial cell proliferation. The latter effect, namely the induced rate of tumour growth, is consistent with the angiogenic activity of wound fluid as well as with the finding that wound fluid was directly mitogenic to the tumour cells, and accelerated growth of C6 glioma in spheroid culture. Of the multiple growth factors present in wound fluid, two key factors, heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) and platelet-derived growth factor (PDGF), were identified as the dominant mitogens for C6 glioma, and inhibition of their activity using specific neutralizing antibodies suppressed the mitogenic effect of wound fluid on DNA synthesis in C6 glioma. This study suggests that the stimulatory effect of injury on tumour progression can possibly be attenuated by therapeutic targeting directed against a limited number of specific growth factors.

Angiogenesis Inducing Agents↗
PubMed1999

Dynamic remodeling of the vascular bed precedes tumor growth: MLS ovarian carcinoma spheroids implanted in nude mice.

The goal of this study was to monitor the vascular bed during the lag phase in growth of implanted spheroids as a model of tumor dormancy. Vascular development and tumor growth were followed up by magnetic resonance imaging in a model system of MLS ovarian carcinoma spheroids implanted subcutaneously in female nude mice. Apparent vessel density in a 1-mm rim surrounding the spheroid was evaluated by gradient echo imaging as a measure of the angiogenic potential of the tumor. Vascular functionality and maturation were assessed by signal intensity changes in response to hyperoxia (elevated oxygen) and hypercapnia (elevated carbon dioxide), respectively. Tumor growth was delayed by 12 to 57 days after implantation. During this long period in which tumor volume did not change, up to 6 cycles of vascular development and regression were observed. We propose here that dynamic remodeling of the vascular bed may precede exit of tumors from dormancy. The sustained oscillations in the angiogenic response to the implanted spheroid are consistent with hypoxic regulation of vascular endothelial growth factor (VEGF), combined with the role of VEGF as an essential survival factor for newly formed blood vessels. Vascular maturation, manifested by physiological vasodilatory response to carbon dioxide, may be important for conferring vascular stability and exit from dormancy.

Animals↗
PubMed1999

Inhibition of neovascularization and tumor growth, and facilitation of wound repair, by halofuginone, an inhibitor of collagen type I synthesis.

Halofuginone, an inhibitor of collagen alpha1(I) gene expression was used for the treatment of subcutaneously implanted C6 glioma tumors. Halofuginone had no effect on the growth of C6 glioma spheroids in vitro, and these spheroids showed no collagen alpha1(I) expression and no collagen synthesis. However, a significant attenuation of tumor growth was observed in vivo, for spheroids implanted in CD-1 nude mice which were treated by oral or intraperitoneal (4 microg every 48 hours) administration of halofuginone. In these mice, treatment was associated with a dose-dependent reduction in collagen alpha1(I) expression and dose- and time-dependent inhibition of angiogenesis, as measured by MRI. Moreover, halofuginone treatment was associated with improved re-epithelialization of the chronic wounds that are associated with this experimental model. Oral administration of halofuginone was effective also in intervention in tumor growth, and here, too, the treatment was associated with reduced angiogenic activity and vessel regression. These results demonstrate the important role of collagen type I in tumor angiogenesis and tumor growth and implicate its role in chronic wounds. Inhibition of the expression of collagen type I provides an attractive new target for cancer therapy.

Animals↗