Experimental Study Of Cranial-cervical Lymph Return And Expression Of Lymphangiogenesis Factors In Intracranial Tissue And Intra-extracranial Tumor

Lymph circumfluence is very important to stabilize the milieu interne. However, because there is no lymphatic vessel with endothelial cells, so central nervous system is regarded as"immunodeficiency". Till to the last 60's, animal experiments and clinical researches found out that the obstruction of the cervical lymph circumfluence could cause morphologic, physiological function and behavior abnormality of the brain tissue, cranocervical lymph return has been widely noticed. The VEGF family was found in 1989. Both VEGF-C and VEGF-D were identified as the main lymphangiogenesis factor in the following investigation, whose expression is a clue to the existence of lymphoid endothelial cell. But there is still a controversy about the expression and signification of VEGF-C and VEGF-D in the normal tissue and extra/intracranial carcinoma. In our study involving the cranial cervical lymphatic drainage, we taking 99mTc-DX (99m technetium-labeled stannous macromolecular dextran) as the lymphatic developer quantitatively analysis the pathway of cranial cervical lymphatic drainage by isotope tracer technology. The model of lymphatic cerebroedema in rabbits is established by means of obstruction of cranial cervical lymphatic drainage, which results in the obstruction of the lymphatic return in the brain. Using immuohistochemical method, we half quantitatively measure the expression of the lymphogenesis factor in both intracranial tissue of rabbits and extra/intracranial carcinoma of human. The cranocervical lymph return and its significance are studied and discussed in three aspects.Objective To study the cranial-cervical lymph circumfluence and pathway in rabbits and to observe the physiological and pathological changes after the lymphatic cerebroedema, which was brought by obstruction of cervical lymphatic drainage. We quantitatively analysis the expression of the lymphangiogenesis factor in both intracranial tissue of normal rabbits and extra/intracranial carcinoma of human, and further discuss the mode and significance of the cranial-cervical lymph circumfluence, finally open out the tendency and channel of intracranial metastasis of cervical tumor and extracranial metastasis of intracranial tumor.Methods 1. Using isotope tracer technology, the distribution and clearance of tracers were observed after microinjection of lymph developer labeled by 99mTc into cerebral cortex and deep cervical lymph nodes in rabbits. 2. Fifty New Zealand white rabbits were randomized into two groups: experiment group and control group. The rabbits in experiment group underwent ligation of cervical lymphatic vessel and clearance of lymph nods. The other group underwent mimic operation. At the point of 24h,48h,72h,96h and 168h after operation we measured contents of water, calcium and superoxide dismutase in rabbit brain. 3. The optic nerve, internal carotid artery and dura mater of base of skull of rabbits are chosen as the experimental subject. We half quantitatively measure the expression of the lymphangiogenesis factor and analysis the difference and significance of it with immunohistochemical dyeing method. In the meanwhile, we taking the human astrocytoma, meningoma, medulloblastoma, metastasis cancer in the brain and lung caner as specimen, measure the expression of VEGF-C and VEGF-D in the same way by which the expression of lymphangiogenesis factor is measured. Consequently we comparatively study the tendency of the lymphatic metastasis.Results 1. The clearance of the pathway after microinjection of lymph developer labeled by 99mTc-DX into cerebral cortex. (1) After injecting of 99mTc-DX 0.1 ml into cerebral cortex, relative activity of the brain tissue declined with time, whereas the relative activity of the Willis artery ring increased gradually and reached peak value at 4 hours after operation and then declined gradually. (2) Cervical lateral deep lymph nodes relative activity reached peak value 4 hours after injection of 99mTc-DX 0.1 ml into cerebral cortex and then declined gradually. Whereas the relative activity of vein blood that reached peak value 6 hours after operation was lower than that of the lymph nods. 2 The metastasis of the pathway after microinjection of lymph developer labeled by 99mTc-DX into deep lymph nods in rabbits. (1) After injection of 99mTc-DX 0.1ml into the cervical lateral deep lymph node, 99mTc-DX was measured in the dura mater of base of skull earlier than brain tissue and reached peak value 1.5-2 hours after injecting 99mTc-DX into cervical lateral deep lymph node and then declined gradually. Relative activity of the brain tissue reached peak value after 4 hours after injection of 99mTc-DX into cervical lateral lymph nodes and the peak value was much higher than dura mater of base of skull. (2) After injecting 99mTc-DX 0.1ml into the cervical lateral deep lymph nodes, 99mTc-DX increased in the cerebrospinal fluid and reached peak value 2-3 hours after injection and then declined gradually. Relative activity of the venous blood was significantly higher than cerebrospinal fluid, but it was reached peak value at 4–5 hours after injection. 3. After the cervical lymphatic drainage in rabbit brain are obstructed, the content of water of rabbit brain at the experimental group are significantly higher than the control group in 24 hours to 168 hours after operation (p<0.05). The peak showed up in 72 hours after operation. The content of calcium of rabbit brain at the experimental group were significantly higher than the control group in 24 hours to 168 hours after operation (p<0.05). The peak showed up in 72 hours after operation. The content of superoxide dismutase of rabbit brain at experimental group were significantly lower than the control group in 48 hours to 96 hours after operation (p<0.05). Then they are decreased in 48 hours after operation. The lowest point showed up in 96 hours after operation, then they return to normal level in the following week. 4. The expression of VEGF-C and VEGF-D was found in optic nerve, internal carotid artery and dura mater of base of skull in rabbits brain. The internal carotid artery was higher than the dura mater of base of skull, which is higher than the optic nerve. The expression of VEGF-C and VEGF-D was found in human astrocytoma, meningoma, medulloblastoma, metastasis cancer in the brain and lung caner. The astrocytoma and metastasis cancer in the brain are the highest, lung caner(lymphatic metastasis)was higher than menigoma, and medulloblastoma was the lowest. But the expression of VEGF-D in astrocytoma and metastasis cancer in the brain was indiscriminate.Conclusion1. The cranocervical lymph return in rabbits is existence and its pathway build up the lymph system of the base of skull. 2. The pathway of base of skull lymph system perhaps concludes peripheral space of nerve, peripheral space of Willis artery and dura mater of base of skull. 3. The contents of water, calcium in rabbit brain were increased significantly after obstruction of cervical lymphatic drainage. On the other hand, the contents of superoxide dismutase decreased markedly. The obstruction of cerebral lymphatic drainage occurred after obstruction of cervical lymphatic drainage. That brought lymphatic cerebroedema. 4. The expression of VEGF-C and VEGF-D was found in optic nerve, internal carotid artery and dura mater of base of skull in rabbit's brain. The internal carotid artery was higher than the dura mater of base of skull, which is higher than the optic nerve. 5. The expression of VEGF-C and VEGF-D was found in human astrocytoma, meningoma, medulloblastoma, metastasis cancer in the brain and lung caner. The astrocytoma and metastasis cancer in the brain are the highest, lung caner(lymphatic metastasis)was higher than menigoma, and medulloblastoma was the lowest. But the expression of VEGF-D in astrocytoma and metastasis cancer in the brain was indiscriminate. 6. The lymph system of the base of skull is the pathway of intra-extracranial tumor metastasis. So the obstruction of cranial-cervical lymph return, including clearance of lymph of the skull base, radical cervical clearance of lymph nodes and radiotherapy of lymph nodes, will decrease the probability of intra-extracranial tumor metastasis and are beneficial for patients'prognosis.