淋巴管新生及其在相关疾病发生和治疗中的意义

淋巴管在维持体内微环境衡定、免疫反应和肿瘤淋巴转移等方面起着重要作用,淋巴管新生与胚胎发育、外伤修复、炎症转归和肿瘤转移密切相关.在趋化因子和生长因子的作用下,淋巴管内皮细胞迁移、增殖和构成管腔,形成新的淋巴管.近年来发现淋巴管内皮祖细胞参与淋巴管新生.淋巴管内皮特异表达Prox-1、podoplanin、VEGFR-3和 LYVE-1等,这些因子和受体调控淋巴管新生.VEGF-C/VEGFR-3或VEGF-D/VEGFR-3信号途径在淋巴管新生过程中起着重要作用.VEGF-C、VEGF-D和VEGFR-3可作为基因治疗的靶点,有望治疗淋巴管新生障碍性疾病以及抗移植后免疫排斥和抗肿瘤淋巴管转移.本文主要综述了胚胎发育、先天性淋巴水肿、炎性病变和肿瘤等状态下淋巴管新生的变化及其机制、淋巴管内皮祖细胞参与淋巴管新生的过程、淋巴管内皮细胞特异性转录因子和受体对于淋巴管新生的调控作用.     

淋巴水肿时淋巴管收缩的实验研究及其临床意义

本文通过对54只已制成淋巴水肿模型的大白鼠的淋巴管收缩功能进行观察后提出:淋巴水肿时,淋巴管收缩功能的变化依组织和淋巴管的病理改变大致可分三个时期。第一期、第二期因有收缩功能的淋巴管存在,可进行淋巴管静脉吻合手术;第三期大部分淋巴管因纤维化已完全丧失收缩功能,故不宜行淋巴管静脉吻合术。     

淋巴管系统与肿瘤新生淋巴管研究方法新进展

长期以来 ,由于缺乏特异的淋巴管系统研究方法与标记技术 ,淋巴管的研究报道较少。新研制的较特异敏感的染色方法以及新近发现的多种淋巴管内皮细胞标记物 ,将深化对淋巴管系统结构功能的认识和肿瘤新生淋巴管在淋巴道转移过程中的作用机制研究     

Prox-1与淋巴管新生和肿瘤转移的关系

侵袭和转移是恶性肿瘤的重要生物学行为之一,淋巴道转移是恶性肿瘤难以根治以及高病死率的主要原因,也是判断患者预后的主要指标。果蝇prospero同源异形盒蛋白1（prospero homeobox protein 1,Prox-1）在胚胎时期淋巴管形成过程中具有重要作用,可以作为淋巴管内皮细胞标志物,显示肿瘤新生淋巴管,并与肿瘤淋巴道转移密切相关。尽管Prox-1促进胚胎淋巴管形成机制的研究较为深入,但是在肿瘤淋巴管新生和淋巴道转移的作用机制方面仍有待于进一步探讨,Prox-1可能作为抑制肿瘤淋巴管新生和治疗肿瘤的新靶点,用于阻断肿瘤转移和改善患者预后。现就Prox-1与胚胎淋巴管形成、肿瘤淋巴管新生以及与肿瘤淋巴道转移关系的相关研究现状综述如下。     

第21届国际淋巴学大会会议通知

第21届国际淋巴学大会将于2007年9月26日至9月29日在上海召开。大会由国际淋巴学会主办，上海交通大学医学院附属第九人民医院承办。这是代表国际淋巴学领域最高水平的盛会，也是国际淋巴学会成立40年来首次在中国召开年会。会议交流的内容包括：淋巴管再生和淋巴管病变的基因学基础，淋巴系统的解剖和生理，淋巴循环障碍疾病的病理生理学，淋巴系统的影像学，肿瘤淋巴学（淋巴道转移和哨兵淋巴结），艾滋病与淋巴，丝虫病与淋巴水肿，淋巴水肿的诊断和治疗等。     

第21届国际淋巴学大会会议通知

第21届国际淋巴学大会将于2007年9月26日至9月29日在上海召开。大会由国际淋巴学会主办，上海交通大学医学院附属第九人民医院承办。这是代表国际淋巴学领域最高水平的盛会，也是国际淋巴学会成立40年来首次在中国召开年会。会议交流的内容包括：淋巴管再生和淋巴管病变的基因学基础，淋巴系统的解剖和生理，淋巴循环障碍疾病的病理生理学，淋巴系统的影像学，肿瘤淋巴学（淋巴道转移和哨兵淋巴结），艾滋病与淋巴，丝虫病与淋巴水肿，淋巴水肿的诊断和治疗等。     

细胞因子与肿瘤淋巴管形成

在很多恶性肿瘤中,淋巴道转移是其主要的转移途径,其在肿瘤的诊断、分期和治疗中起着关键的作用.肿瘤诱导血管形成对于肿瘤生长和转移的意义已经在研究者之间达成共识.研究发现,与血管生成类似,淋巴管形成参与胞外基质退化,刺激淋巴内皮细胞增殖和迁移,以及促进管状结构的形成[1].能在细胞间传递信息和具有免疫调节的的细胞因子自然在其形成中也起到重要作用.临床上已经利用包括是肿瘤分泌的和宿主细胞分泌的细胞因子的作用机制研制药物并治疗疾病.细胞因子在淋巴管形成中的作用机制会具有更广阔的价值.     

大隐静脉旁淋巴管的应用解剖

目的　研究大隐静脉周围淋巴管的解剖学特征,为治疗下肢继发性阻塞性淋巴水肿提供解剖学基础。  方法　择成年新鲜尸体3具,截取3对下肢。在内踝后皮内,注入少量双氧水,于真皮下找到淋巴管,将显影剂经30G注射针注入淋巴管。在下肢内侧沿显影之淋巴管进行追踪解剖、照像及X线记录。  结果　从内踝后区至腹股沟可见不同数量、大小的淋巴管,呈向心性、蜿蜒起伏地与大隐静脉伴行于下肢内侧的皮下组织内。管径在0.2 ~1.8 mm之间。在行程中淋巴管分叉或合流、或与附近淋巴管交叉通过。汇入腹股沟淋巴结前分成许多小分支。解剖过程中,发现了淋巴管壁的营养血管。  结论　详细描叙了从内踝后区到腹股沟淋巴结的淋巴通路。为治疗继发性淋巴水肿和其他与下肢淋巴系有关的疾病时提供形态学基础。     

男性外生殖器的淋巴流向

在３０具足月胎儿和新生儿男性新鲜尸体上，用淋巴管间接注射法观察了男性外生殖器淋巴管的分布、吻合情况及其淋巴流向，为临床阴茎癌的淋巴结清扫术和阴囊淋巴水肿作淋巴管静脉吻合术，提供解剖学依据。     

原发性小肠淋巴管扩张症2例并文献复习

目的探讨小肠淋巴管扩张症的临床表现,诊断、治疗及预后等。方法2例患儿除一般的血清学、尿液、超声心动图、腹部B超和腹部CT等检查外,均接受胃镜和（或）小肠镜检查并取黏膜行病理活检。结果例1,5岁发病,以反复水肿起病,小肠镜检查发现空肠、回肠弥漫性白色粟米样改变,病理提示肠黏膜固有膜内及黏膜肌层内可见到较多扩张淋巴管,淋巴管内皮细胞增生不明显。例2,5月龄发病,以水肿、腹泻起病,胃镜检查发现十二指肠黏膜弥漫性白色粟米样改变,正常绒毛结构消失,病理提示个别绒毛黏膜内可见轻度扩张淋巴管。2例患儿均除外引起小肠淋巴管扩张的继发性因素,结合起病年龄小,考虑原发性小肠淋巴管扩张症,其中例1诊断为小肠弥漫性淋巴管扩张。这2例患儿通过中链三酰甘油乳剂治疗后,随访症状明显缓解。结论小肠淋巴管扩张症在儿童中可能并不少见。对于反复低蛋白血症、反复水肿或慢性腹泻的患儿要警惕原发性小肠淋巴管扩张症,应尽早行内镜及病理活检,并通过特殊的饮食控制疾病。     

Lymphangiogenesis and expression of specific molecules as lymphatic endothelial cell markers

In recent years, several functional molecules specifically expressed and localized in lymphatic endothelial cells, such as 5'-nucleotidase, lymphatic vessel endothelial receptor-1, vascular endothelial growth factor receptor-3, podoplanin and Prox-1, have been identified. The discovery of the lymphatic endothelial cell markers facilitated detailed analysis of the nature and structural organization of the lymphatic vessels and their growth (lymphangiogenesis). As a result, over the past few years, advances have been made in understanding the cellular and molecular aspects of physiological lymphangiogenesis and tumor-induced lymphangiogenesis. The biology of lymphangiogenesis, particularly the mechanism of its regulation, is very important in understanding the formation of the lymphatic system as a biological regulation system transporting tissue fluid and wandering cells, including lymphocytes, and disease involving lymphangiogenesis. The understanding of the molecular mechanism of lymphangiogenesis and the elucidation of the development of normal and pathological tissues are expected to lead to the development of therapy for intractable diseases, such as malignant tumors and lymphedema.     

Vascular endothelial growth factor C is required for sprouting of the first lymphatic vessels from embryonic veins

Lymphatic vessels are essential for immune surveillance, tissue fluid homeostasis and fat absorption. Defects in lymphatic vessel formation or function cause lymphedema. Here we show that the vascular endothelial growth factor C (VEGF-C) is required for the initial steps in lymphatic development. In Vegfc-/- mice, endothelial cells commit to the lymphatic lineage but do not sprout to form lymph vessels. Sprouting was rescued by VEGF-C and VEGF-D but not by VEGF, indicating VEGF receptor 3 specificity. The lack of lymphatic vessels resulted in prenatal death due to fluid accumulation in tissues, and Vegfc+/- mice developed cutaneous lymphatic hypoplasia and lymphedema. Our results indicate that VEGF-C is the paracrine factor essential for lymphangiogenesis, and show that both Vegfc alleles are required for normal lymphatic development.     

Transgenic induction of vascular endothelial growth factor-C is strongly angiogenic in mouse embryos but leads to persistent lymphatic hyperplasia in adult tissues

Vascular endothelial growth factor-C (VEGF-C) is the quintessential lymphangiogenic growth factor that is required for the development of the lymphatic system and is capable of stimulating lymphangiogenesis in adults by activating its receptor, VEGFR-3. Although VEGF-C is a major candidate molecule for the development of prolymphangiogenic therapy for defective lymphatic vessels in lymphedema, the stability of lymph vessels generated by exogenous VEGF-C administration is not currently known. We studied VEGF-C-stimulated lymphangiogenesis in inducible transgenic mouse models in which growth factor expression can be spatially and temporally controlled without side effects, such as inflammation. VEGF-C induction in adult mouse skin for 1 to 2 weeks caused robust lymphatic hyperplasia that persisted for at least 6 months. VEGF-C induced lymphangiogenesis in numerous tissues and organs when expressed in the vascular endothelium in either neonates or adult mice. Very few or no effects were observed in either blood vessels or collecting lymph vessels. Additionally, VEGF-C stimulated lymphangiogenesis in embryos after the onset of lymphatic vessel development. Strikingly, a strong angiogenic effect was observed after VEGF-C induction in vascular endothelium at any point before embryonic day 16.5. Our results indicate that blood vessels can undergo VEGF-C-induced angiogenesis even after down-regulation of VEGFR-3 in embryos; however, transient VEGF-C expression in adults can induce long-lasting lymphatic hyperplasia with no obvious side effects on the blood vasculature.     

The role of lymphatic vessels in the heart

Although cardiac lymphatic vessels have been described for over three centuries, research progress on the role of cardiac lymphatic vessels in regulating cardiac physiology and their disturbances in the pathogenesis of cardiac disease has progressed very slowly, largely due to technical challenges in developing both animal models and cardiac lymphatic vascular imaging technologies. This review summarizes evidence showing that blocking cardiac lymph flow may contribute to several forms of cardiac injury including cardiac lymphedema, cardiac valvular deformation, coronary arterial injury, conduction disturbances, myocardial injury, and poor heart performance in animal and human heart studies. Conversely, improving cardiac lymph flow may have beneficial effects on heart function after heart attack (myocardial infarction). In addition, this review summarizes recent hypotheses about the forces generating cardiac lymph flow, in which the role of both the subepicardial and mid-myocardial myocytes synchronized contractions causing lymph flow is discussed. Lastly, possible mechanisms of blood vessel injury caused by the failure of perivascular lymphatic remodeling are discussed.     

An Experimental Model for the Study of Lymphedema and its Response to Therapeutic Lymphangiogenesis

BACKGROUND: Evaluation of the efficacy of molecular treatment strategies for lymphatic vascular insufficiency requires a suitable preclinical animal model. Ideally, the model should closely replicate the untreated human disease in its pathogenesis and pathological expression. OBJECTIVE: We have undertaken a study of the time course of the development and resolution of acquired, experimental lymphedema and of its responses to vascular endothelial growth factor (VEGF)-C lymphangiogenesis in the mouse tail model. STUDY DESIGN: We provoked post-surgical lymphedema in the mouse tail model and assessed the effects of exogenously administered human recombinant VEGF-C. Quantitative assessment of immune traffic function was performed through sequential in vivo bioluminescent imaging. RESULTS: In untreated lymphedema, tail edema was sustained until day 21. Exogenous administration of human recombinant VEGF-C produced a significant decrease in volume. Untreated lymphedema in the mouse tail model was characterized by the presence of dilated cutaneous lymphatics, marked acute inflammatory changes, and hypercellularity; VEGF-C produced a substantial reversion to the normal pattern, with notable regression in the size and number of cutaneous lymphatic vessels that express lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1). In vivo imaging confirmed the presence of an impairment of immune traffic in lymphedema that was ameliorated after VEGF-C administration. CONCLUSION: The post-surgical murine tail model of lymphedema closely simulates attributes of human lymphedema and provides the requisite sensitivity to detect therapeutically induced functional and structural alterations. It can, therefore, be used as an investigative platform to assess mechanisms of disease and its responses to candidate therapies, such as therapeutic lymphangiogenesis.     

A system for quantifying the patterning of the lymphatic vasculature

The lymphatic vasculature is critical for immunity and interstitial fluid homeostasis, playing important roles in diseases such as lymphedema and metastatic cancer. Animal models have been generated to explore the role of lymphatics and lymphangiogenic growth factors in such diseases, and to study lymphatic development. However, analysis of lymphatic vessels has primary been restricted to counting lymphatics in two-dimensional tissue slices, due to a lack of more sophisticated methodologies. In order to accurately examine lymphatic dysfunction in these models, and analyse the effects of lymphangiogenic growth factors on the lymphatic vasculature, it is essential to quantify the morphology and patterning of the distinct lymphatic vessels types in three-dimensional tissues. Here, we describe a method for performing such analyses, integrating user-operated image-analysis software with an approach that considers important morphological, anatomical and patterning features of the distinct lymphatic vessel subtypes. This efficient, reproducible technique is validated by analysing healthy and pathological tissues.     

A system for quantifying the patterning of the lymphatic vasculature

The lymphatic vasculature is critical for immunity and interstitial fluid homeostasis, playing important roles in diseases such as lymphedema and metastatic cancer. Animal models have been generated to explore the role of lymphatics and lymphangiogenic growth factors in such diseases, and to study lymphatic development. However, analysis of lymphatic vessels has primary been restricted to counting lymphatics in two-dimensional tissue slices, due to a lack of more sophisticated methodologies. In order to accurately examine lymphatic dysfunction in these models, and analyse the effects of lymphangiogenic growth factors on the lymphatic vasculature, it is essential to quantify the morphology and patterning of the distinct lymphatic vessels types in three-dimensional tissues. Here, we describe a method for performing such analyses, integrating user-operated image-analysis software with an approach that considers important morphological, anatomical and patterning features of the distinct lymphatic vessel subtypes. This efficient, reproducible technique is validated by analysing healthy and pathological tissues.     

Role of COX-2 in lymphangiogenesis and restoration of lymphatic flow in secondary lymphedema

The pathophysiology of secondary lymphedema remains poorly understood. To clarify the roles of cyclooxygenase (COX)-2 in enhancement of lymphangiogenesis during secondary lymphedema, we tested a mouse tail model and evaluated the recurrence of lymph flow. To induce lymphedema, a circumferential incision was made in the tail of anesthetized mice to sever the dermal lymphatic vessels. The maximum diameters of the tails were measured weekly. We found that the diameters of the tails around the wounds were markedly increased after surgery, and reached maximum size 2 weeks after wounding in mice without a COX-2 inhibitor, celecoxib (Celecoxib-). Expression of COX-2 in wound granulation tissues was markedly increased 1 week after surgery compared with unwounded naive control mice. In Celecoxib-, recurrence of lymphatic flow in the wound granulation tissues was detected 3 weeks after surgical treatment. In contrast, lymphatic flow was markedly suppressed in mice treated with celecoxib (Celecoxib+). Newly formed lymphatic structures were identified in the granulation tissues formed at wounded lesions in Celecoxib-, whereas those were markedly suppressed in Celecoxib+. Interstitial tissue pressures in the distal areas of the tail wounds were markedly increased in Celecoxib+ with reduced expression of vascular endothelial cell growth factor (VEGF)-C. F4/80-positive cells were accumulated to the wound granulation tissues in Celecoxib-, and the accumulation of these cells was suppressed in Celecoxib+. Prostaglandin E(2) (PGE(2)) upregulated the expressions of VEGF-A and VEGF-C in cultured macrophages, but not human lymphatic microvascular endothelial cells. The present study therefore suggests that lymphangiogenesis, together with recurrence of lymph flow after surgical induction of lymphedema, is upregulated by COX-2 possibly via generation of PGs.     

Inhibition of inflammatory lymphangiogenesis by integrin alpha5 blockade

The interaction between endothelial cells and extracellular matrix proteins plays an important role in (hem)angiogenesis. Integrins are able to mediate the outgrowth of newly formed blood vessels. In contrast, the role of integrins in lymphangiogenesis, ie, the outgrowth of new from pre-existing lymphatic vessels, has so far been unclear. Here, expression and functional relevance of integrins on lymphatic endothelium in vivo was investigated using the mouse model of combined inflammatory corneal hemangiogenesis and lymphangiogenesis. Immunohistochemistry revealed novel expression of both integrin alpha5 and alphav on both resting and activated lymphatic vessels in vivo. Integrin alpha5-inhibiting small molecules significantly blocked the outgrowth of new lymphatic vessels into the cornea in a dose-dependent manner. The outgrowth of blood vessels was less significantly affected by this treatment, thus allowing for selective inhibition of lymphangiogenesis at lower dosages. Combined inhibition of integrin alpha5 and alphav using inhibiting molecules did not significantly increase the anti-lymphangiogenic effect in vivo, thus suggesting an important functional role of integrin alpha5 in lymphangiogenesis. In summary, our findings demonstrate novel expression of specific integrins on growing lymphatic endothelial cells in vivo and reveal their functional role during lymphangiogenesis. This opens new treatment options for selective inhibition of lymphangiogenesis, eg, in oncology and transplant immunology.