| Glioma is the most common malignant tumor in central nervous system, invasive growth is one of the most important biological behavior of tumor cells, which infiltrating the surrounding brain tissue to grow, it is usually not easy to distinguish clear boundaries between tumor tissue and normal brain tissue. Different levels of edema can always be found around tumor tissue, peritumoral edema refers to conventional enhanced CT, MRI scan showed the low-density and low-signal areas surrounding the tumor. Generally it is agreed that glioma tumor edema is the root of glioma recurrence, the edema can be used to reflect the malignant degree, and helpful in the glioma diagnosis, treatment and prognosis of great significance. Current conventional imaging examination can not have the characteristic distinction of the substance of the tumor and surrounding edema, while the magnetic resonance perfusion imaging, PWI as a new technology to enhance clinical treatment can provide more information that can be offset to some extent its shortcomings. Although peritumoral edema formation mechanisms are not yet entirely clear, but with the Scholars from the perspective of cellular and molecular biology study of peritumoral edema in-depth, more and more evidence suggest that the occurrence of peritumoral edema is related to vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMPs) and other factors. In this paper, with applications of magnetic resonance perfusion imaging technologies, vascular endothelial growth factor (VEGF), matrix metalloproteinase-9 (MMP-9) and microvessel density (MVD) expression were detected by immunohistochemistry in glioma tumor and peritumoral edema tissues separately, and at the same time structural characteristics of peritumoral edema region were observed by light microscopy and transmission electron microscopy, to discuss glioma angiogenesis, peritumoral edema formation mechanism of the structure, biological behavior and clinical significance.ObjectiveThe value in detecting tumor angiogenesis and peritumoral edema by studying the perfusion results of PWI of the human brain glioma were discussed; VEGF, MMP-9 and MVD expression were detected by immunohistochemistry in glioma tumor and peritumoral edema tissues separately, and at the same time structural characteristics of peritumoral edema region were observed by light microscopy and transmission electron microscopy, to reveal the relationship between VEGF, MMP-9 expression and angiogenesis and peritumoral brain edema (PTBE) and tumor malignant degree.MethordsAccording to conventional CT, MRI images,patients were divided into two groups, without peritumoral edema and with peritumoral edema group, the later group consists of 23 patients with peritumoral edema. All patients underwent preoperative unenhanced or enhanced MR scan, according to conventional T1-weighted scan (T1WI), T2-weighted scan (T2WI), and T1WI enhanced scan, tumor size and peritumoral edema volume were measured,to calculate the edema Index (EI), in order to estimate the extent of brain edema. At the same time,all the cases underwented MR perfusion imaging (PWI) checks, acquiring cerebral blood volume (cerebral blood volume, CBV) and a more accurate picture of the real tumor boundary, then calculated the tumor and peritumoral edema zone average relative regional cerebral blood volume values (rCBV), analysised these parameters with glioma grade and angiogenesis, and its diagnostic significance of peritumoral edema. Combined with conventional CT, MRI images supporting the naked eye under examination to determine the tumor and peritumoral edema position, since the aneurysm from the inside out according to the order of sub-parts derived (tumor, peritumoral edema) of the two copies, one of which fixed with 10% neutral formalin, cutted into paraffin-embedded tissue sections, underwented HE staining and immunohistochemical method (SABC) to detect VEGF, MMP-9 expression of the tumor and peritumoral edema area; with CD34 antibodies to mark vascular endothelial cells, counted microvessel density (microvessel density, MVD), to assess the degree of angiogenesis. The other specimens were fixed with 3% glutaraldehyde, and then embedded by SPURR low-viscosity embedding medium, ultra-structural pathological structural changes in tumor and peritumoral edema zone were. observed by electron microscopy ation.Results1. The incidence of peritumoral edema is 76.7%. The single-factor analysis of variance (LSD method), P<0.01, can be considered at different levels of glioma El index is not exactly the same.Ⅱgrade glioma andⅠ,Ⅳgrade gliomas in the degree of edema, there was significant difference (P<0.05), withⅢgrade glioma in the degree of edema was no significant difference (P> 0.05). 2. The scope of abnormal perfusion area displayed on CBV pseudo-color pictures is larger than which showed on conventional MRI images. Low-grade gliomas Group:Compared with the contralateral normal brain,cerebral blood volume pseudo-color pictures in gliomar tumor showed a lower slightly higher perfusion changes. The distribution of signal intensity-time curve is similar to normal brain tissue:Negative-enhanced curves were symmetrical on both sides, the first pass duration of the negative enhancements was not obvious, the enhanced baseline levels compared with the previous baseline levels decreased slightly. High-grade gliomas Group:the signal degree of cerebral blood volume pseudo-color pictures were uneven, tumor perfusion area showed medium or high signal, peritumoral edema was lower or equal perfusion area. Signal intensity-time curve was negative enhanced, the up and decline in branch curves are asymmetry, after the first-pass contrast agent enhanced the baseline levels were lower than before, but it still can be seen rising up to the baseline level slowly, this phenomenon has prompted leakage of contrast agent, there may exist blood-brain barrier damage. Negative enhanced the area under the curve contains significantly larger than that group of low-grade gliomas, indicating a markerful increase in tumor angiogenesis. Of low-grade gliomas group:The tumor’s mean rCBV is1.64±0.50, peritumoral mean rCBV is 0.76±0.46; Of high-grade gliomas group:the tumor’s mean rCBV is 3.58±1.19, peritumoral mean rCBV is 1.64±0.90. rCBV in peritumoral edema zone of high-grade gliomas was significantly higher than in the contralateral white matter, rCBV value in tumor area was significantly higher than in the peritumoral edema (P<0.01), rCBV values near edema zone were higher than that far away from the edema, tumor and peritumoral edema regional average rCBV values of high-grade gliomas group were greater than those of low-grade gliomas group, the difference was statistically significant (P <0.05). 3. VEGF, MMP-9 immunohistochemical staining expression of 6 cases of normal brain tissue (NB) were negative; the average of MVD is 6-7 by the light microscope under 10×20 times. In tumor tissues, VEGF expressed in the cytoplasm of tumor cells and endothelial cells showed brown-yellow staining, MMP-9 expressed in the cytoplasm of in the the cytoplasm of tumor cells and vascular basement membrane showed brown-yellow staining. In peritumoral edema tissues, VEGF expressed in the cytoplasm of endothelial cells and glial cells showed brown-yellow staining, tumor organizations, MMP-9 expressed in the cytoplasm of glial cells and vascular basement membrane showed brown-yellow staining.①VEGF expression in tumor tissues of high-grade gliomas group were higher than the corresponding value of the low-level group, the difference was significant (P <0.01); while in peritumoral tissues, the difference was not statistically significant (P>0.05). VEGF expression in tumor tissues were higher than in peritumoral tissues, the differences were statistically significant (P< 0.05).②It can not be thought that differences between the MMP-9 expression in tumor and in peritumoral tissues of different pathological levels were statistically different (P>0.05).③In low-level group:tumor MVD averaged 15.75±8.53, peritumoral MVD mean 12.25±7.40; in high-level group:tumor MVD averaged 40.00±13.87, peritumoral mean MVD is 30.93±16.32. MVD values can be used to reflect the degree of angiogenesis. Tumor MVD value is higher than that of peritumoral, their difference was statistically significant (P<0.05). There was a significant difference between MVD of different pathological levels(P<0.05), and with the increase of tumor grade, MVD values have gradually increased trends.4.①MVD values and rCBV values at all levels of glioma tumor and peritumoral edema area were significantly positively correlated (P<0.01); VEGF values and rCBV values at all levels of glioma tumor and peritumoral edema area were significantly correlated (P<0.05;P<0.01); MMP-9 values and rCBV values at all levels of glioma tumor and peritumoral edema were also significantly correlated (P <0.01).②VEGF values and the MMP-9 values at all levels of glioma tumor and peritumoral edema area were significantly correlated (P<0.01), prompted that VEGF and MMP-9 may be a mechanism for the existence of interaction effect. Between VEGF, MMP-9 expression of high-grade gliomas group and glioma angiogenesis existed significant positive correlations (P<0.01); in tumor and peritumoral edema tissues, MVD, VEGF, MMP-9 and EI are significantly correlated (P<0.01).5. HE staining observed under light microscope:intratumor micro vessel density of low-level group is small, peripheral vascular tumor response is light, peritumoral edema was not obvious, peritumoral infiltration is not serious; intratumor microvessel density of high-level group is large, tumor and peritumoral edema is obvious,it is common to find large areas of hemorrhage and necrosis, obvious vascular reactivity and peritumoral infiltration, or even the distribution of tumor cells nest.Light microscopic features of tumor and peritumoral area:①In the tumor area:with obvious hyperplasia of capillary endothelial cells, thickening and arranged as multi-layer, vascular structures are still complete, which was more common around the distribution of tumor cells; large areas of hemorrhage and necrosis may be seen, necrotic area showed homogeneous staining cell-free zone, the performance of high-grade gliomas is more extensive. With serious edema can be seen clearly by the organization sparse, multi-edema and vacuoles, a few shows a marked widening of blood vessels outside the cavity and its surrounding tissue sparse and necrosis;②peritumoral area existed swelling and proliferation of capillary endothelial cell, showing that intravascular congestion, blood vessel external cavity has noticeably increased, more capillaries can be seen around the exudation, with more obvious sparse surroundings, dense cytoplasmic vacuoles edema, around hemorrhage the common were solubility of necrosis cells, glial cell swelling, the boundary is not clear.6. Pathological observation under electron microscope:With obvious edema can be seen clearly damaged blood-brain barrier and tumor-brain barrier more serious, more invasive tumor cells and more obvious microvascular changes. Also, which can be seen clearly that microvascular endothelial cells full of large cystic vesicle organelles (vesicular vacuolar organelle, VVO, many small vacuoles interconnected into a capsule and formed grape-like structure) and more moth-eaten hollow in the basement membrane, were consistent with VEGF levels and MMP-9 levels separately. This prompt us that VEGF may be involved in increase the VVO structure in the endothelial cells, MMP-9 may be involved in destruction of extracellular matrix and capillary basement membrane structure, namely, the ultrastructural pathology of peritumoral edema may be related to both the structural changes. In the above-mentioned changes, although basement membrane thickening can be showed uneven, moth-eaten appear empty, but the basement is still full, some tumor cells of the glial membrane surrounding the blood vessel wall, but no tumor cells invade the basement membrane or endothelial cell gap.Conclusions①Glioma tumor invasiveness and edema generation are the result of the interaction between microvascular endothelial cells and glioma cells. Both VEGF and MMP-9 played very important roles in angiogenesis and peritumoral edema mechanisms to promote the evolution of malignant gliomas.②PWI signs of peritumoral brain edema can be indirectly reflected in glioma angiogenesis and prediction of malignancy of glioma.③Combination of MVD, VEGF, MMP-9 and relative cerebral blood volume (rCBV) values can be used as effective indicators to determine the degree and prognosis of malignant tumor. |
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