Recanalization of the Collecting Lymphatics in Rabbit Hind Leg

Perturbed collagen metabolism underlies lymphatic recanalization failure in Gata2 heterozygous deficient mice

Lymphedema has become a global health issue following the growing number of cancer surgeries. Curative or supportive therapeutics have long been awaited for this refractory condition. Transcription factor GATA2 is crucial in lymphatic development and maintenance, as GATA2 haploinsufficient disease often manifests as lymphedema. We recently demonstrated that Gata2 heterozygous deficient mice displayed delayed lymphatic recanalization upon lymph node resection. However, whether GATA2 contributes to lymphatic regeneration by functioning in the damaged lymph vessels' microenvironment remains explored. In this study, our integrated analysis demonstrated that dermal collagen fibers were more densely accumulated in the Gata2 heterozygous deficient mice. The collagen metabolism-related transcriptome was perturbed, and collagen matrix contractile activity was aberrantly increased in Gata2 heterozygous embryonic fibroblasts. Notably, soluble collagen placement ameliorated delayed lymphatic recanalization, presumably by modulating the stiffness of the extracellular matrix around the resection site of Gata2 heterozygous deficient mice. Our results provide valuable insights into mechanisms underlying GATA2-haploinsufficiency-mediated lymphedema and shed light on potential therapeutic avenues for this intractable disease.

Lymphatic Contractile Function: A Comprehensive Review of Drug Effects and Potential Clinical Application

BACKGROUND

The lymphatic system and the cardiovascular system work together to maintain body fluid homeostasis. Despite that, the lymphatic system has been relatively neglected as a potential drug target and a source of adverse effects from cardiovascular drugs. Like the heart, the lymphatic vessels undergo phasic contractions to promote lymph flow against a pressure gradient. Dysfunction or failure of the lymphatic pump results in fluid imbalance and tissue oedema. While this can due to drug effects, it is also a feature of breast cancer-associated lymphoedema, chronic venous insufficiency, congestive heart failure and acute systemic inflammation. There are currently no specific drug treatments for lymphatic pump dysfunction in clinical use despite the wealth of data from pre-clinical studies.

AIM

To identify (1) drugs with direct effects on lymphatic tonic and phasic contractions with potential for clinical application, and (2) drugs in current clinical use that have a positive or negative side effect on lymphatic function.

METHODS

We comprehensively reviewed all studies that tested the direct effect of a drug on the contractile function of lymphatic vessels.

RESULTS

Of the 208 drugs identified from 193 studies, about a quarter had only stimulatory effects on lymphatic tone, contraction frequency and/or contraction amplitude. Of FDA-approved drugs, there were 14 that increased lymphatic phasic contractile function. The most frequently used class of drug with inhibitory effects on lymphatic pump function were the calcium channels blockers.

CONCLUSION

This review highlights the opportunity for specific drug treatments of lymphatic dysfunction in various disease states and for avoiding adverse drug effects on lymphatic contractile function.

GATA2 participates in the recanalization of lymphatic vessels after surgical lymph node extirpation

Lymphatic recanalization failure after lymphadenectomy constitutes a major risk of lymphedema in cancer surgery. It has been reported that GATA2, a zinc finger transcription factor, is expressed in lymphatic endothelial cells and is involved in the development of fetal lymphatic vessels. GATA3, another member of the GATA family of transcription factors, is required for the differentiation of lymphoid tissue inducer (LTi) cells and is essential for lymph node formation. However, how GATA2 and GATA3 function in recanalization after the surgical extirpation of lymphatic vessels has not been elucidated. Employing a new model of lymphatic recanalization, we examined the lymphatic reconnection process in Gata2 heterozygous deficient (Gata2^+/- ) and Gata3 heterozygous deficient (Gata3^+/- ) mice. We found that lymphatic recanalization was significantly impaired in Gata2^+/- mice, while Gata3^+/- mice rarely showed such abnormalities. Notably, the perturbed lymphatic recanalization in the Gata2^+/- mice was partially restored by crossing with the Gata3^+/- mice. Our results demonstrate for the first time that GATA2 participates in the regeneration of damaged lymphatic vessels and the unexpected suppressive activity of GATA3 against lymphatic recanalization processes.

Utility of indocyanine green injection in patients with cervical cancer besides the identification of sentinel lymph node (Review)

Due to the wide introduction of screening tests, patients with neoplastic diseases of the uterine cervix trend to be diagnosed in early stages of the disease, and less invasive surgical procedures are needed in certain cases. In this respect, the technique of sentinel lymph node dissection has been widely implemented as part of the therapeutic strategy, indocyanine green (ICG) being one of the most reliable markers for sentinel lymph node detection. However, it seems that this agent is extremely useful in order to achieve better short-term and long-term results after cervical cancer surgery, due to its capacity to determine the uterine vascular perfusion in cases in which conservative treatment, such as trachelectomy, is performed, as well as to prevent and treat lower limb lymphedema. A literature review was conducted of the studies which focused on the role of ICG utility in cervical cancer patients besides sentinel lymph node detection, special focus was given to vascularization preservation and lower limb lymphedema prevention and treatment.

Pre-collecting lymphatic vessels form detours following obstruction of lymphatic flow and function as collecting lymphatic vessels

Background

Previously, we showed that lymphatic vessels (LVs) formed detours after lymphatic obstruction, contributing to preventing lymphedema. In this study, we developed detours using lymphatic ligation in mice and we identified the detours histologically.

Methods and results

Under anesthesia, both hindlimbs in mice were subcutaneously injected with Evans blue dye to detect LVs. We tied the right collecting LV on the abdomen that passes through the inguinal lymph node (LN) at two points. The right and left sides comprised the operation and sham operation sides, respectively. Lymphography was performed to investigate the lymph flow after lymphatic ligation until day 30, using a near-infrared fluorescence imaging system. Anti-podoplanin antibody and 5-ethynyl-2’-deoxyuridine (EdU) were used to detect LVs and lymphangiogenesis. Within 30 days, detours had developed in 62.5% of the mice. Detours observed between two ligation sites were enlarged and irregular in shape. Podoplanin⁺ LVs, which were located in the subcutaneous tissue of the upper panniculus carnosus muscle, connected to collecting LVs at the upper portion from the cranial ligation site and at the lower portion from the caudal ligation site. EdU⁺ cells were not observed in these detours. The sham operation side showed normal lymph flow and did not show enlarged pre-collecting LVs until day 30.

Conclusions

Detours after lymphatic ligation were formed not by lymphangiogenesis but through an enlargement of pre-collecting LVs that functioned as collecting LVs after lymphatic ligation. Further studies are required to explore the developmental mechanism of the lymphatic detour for treatment and effective care of lymphedema in humans.

Axillary reverse mapping and lymphaticovenous bypass: Lymphedema prevention through enhanced lymphatic visualization and restoration of flow

BACKGROUND

A lymphedema (LE) prevention surgery (LPS) paradigm for patients undergoing axillary lymphadenectomy (ALND) was developed to protect against LE through enhanced lymphatic visualization during axillary reverse mapping (ARM) and refinement in decision making during lymphaticovenous bypass (LVB).

METHODS

A retrospective analysis of a prospective database was performed evaluating patients with breast cancer who underwent ALND, ARM, and LVB from September 2016 to December 2018. Patient and tumor characteristics, oncologic and reconstructive operative details, complications and LE development were analyzed.

RESULTS

LPS was completed in 58 patients with a mean age of 51.7 years. An average of 14 lymph nodes (LN) were removed during ALND. An average of 2.1 blue lymphatic channels were visualized with an average of 1.4 LVBs performed per patient. End to end anastomosis was performed in 37 patients and a multiple lymphatic intussusception technique in 21. Patency was confirmed 96.5% of patients. Adjuvant radiation was administered to 89% of patients. Two patients developed LE with a median follow-up of 11.8 months.

CONCLUSION

We report on our experience using a unique LPS technique. Refinements in ARM and a systematic approach to LVB allows for maximal preservation of lymphatic continuity, identification of transected lymphatics, and reestablishment of upper extremity lymphatic drainage pathways.

Patterns of lymphatic drainage after axillary node dissection impact arm lymphoedema severity: A review of animal and clinical imaging studies

Upper extremity lymphoedema after axillary node dissection is an iatrogenic disease particularly associated with treatment for breast or skin cancer. Anatomical studies and lymphangiography in healthy subjects identified that axillary node dissection removes a segment of the lymphatic drainage pathway running from the upper limb to the sub-clavicular vein, creating a surgical break. It is reasonable to infer that different patterns of lymphatic drainage may occur in the upper limb following surgery and contribute to the various presentations of lymphoedema from none to severe. Firstly, we reviewed animal imaging studies that investigated the repair of lymphatic drainage pathways from the limb after lymph node dissection. Secondly, we examined clinical imaging studies of lymphatic drainage pathways after axillary node dissection, including lymphangiography, lymphoscintigraphy and indocyanine green fluorescence lymphography. Finally, based on the gathered data, we devised a set of general principles for the restoration of lymphatic pathways after surgery. Lymphoscintigraphy shows that restoration of the original lymphatic pathway to the axilla after its initial disruption by nodal dissection was not uncommon and may prevent lymphoedema. We found that regenerated lymphatic vessels and dermal backflow (the reflux of lymph to the skin) contributed to either restoration of the original pathway or rerouting of the lymphatic pathway to other regional nodes. Variation in the lymphatic drainage pathway and the mechanisms of fluid drainage itself are the foundation of new lymphatic drainage patterns considered to be significant in determining the severity with which lymphoedema develops.

Spatio-temporal changes of lymphatic contractility and drainage patterns following lymphadenectomy in mice

Objective

To investigate the redirection of lymphatic drainage post-lymphadenectomy using non-invasive near-infrared fluorescence (NIRF) imaging, and to subsequently assess impact on metastasis.

Background

Cancer-acquired lymphedema arises from dysfunctional fluid transport after lymphadenectomy performed for staging and to disrupt drainage pathways for regional control of disease. However, little is known about the normal regenerative processes of the lymphatics in response to lymphadenectomy and how these responses can be accelerated, delayed, or can impact metastasis.

Methods

Changes in lymphatic “pumping” function and drainage patterns were non-invasively and longitudinally imaged using NIRF lymphatic imaging after popliteal lymphadenectomy in mice. In a cohort of mice, B16F10 melanoma was inoculated on the dorsal aspect of the paw 27 days after lymphadenectomy to assess how drainage patterns affect metastasis.

Results

NIRF imaging demonstrates that, although lymphatic function and drainage patterns change significantly in early response to popliteal lymph node (PLN) removal in mice, these changes are transient and regress dramatically due to a high regenerative capacity of the lymphatics and co-opting of collateral lymphatic pathways around the site of obstruction. Metastases followed the pattern of collateral pathways and could be detected proximal to the site of lymphadenectomy.

Conclusions

Both lymphatic vessel regeneration and co-opting of contralateral vessels occur following lymphadenectomy, with contractile function restored within 13 days, providing a basis for preclinical and clinical investigations to hasten lymphatic repair and restore contractile lymphatic function after surgery to prevent cancer-acquired lymphedema. Patterns of cancer metastasis after lymphadenectomy were altered, consistent with patterns of re-directed lymphatic drainage.

Recent advance in lymph dynamic analysis in lymphatics and lymph nodes

Lymphatics are a unidirectional transport system that carries fluid from the interstitial space and back into the blood stream. Initial lymphatics take up not only fluid but also high-molecular-weight substances, such as plasma proteins and hyaluronan; immune cells, such as lymphocytes, macrophages, and dendritic cells; and colloidal particles, such as carbon particles, bacteria, and tattoo dye. Interstitially injected colloidal particles are known to accumulate in the regional lymph nodes. This phenomenon is applied to find sentinel lymph nodes in cancer patients. Lymph flow rate and composition are influenced by interstitial fluid, lymphatic pump activity, and intra-lymphatic pressure. Lymph composition is changed during its flow downstream. In this review, the main focus is on the mechanisms of lymph formation at the initial lymphatics and lymph transport through the collecting lymphatics and lymph nodes. (*English Translation of J Jpn Coll Angiol, 2008, 48: 113-123.).

Lymph node dissection--understanding the immunological function of lymph nodes

Lymph nodes (LN) are one of the important sites in the body where immune responses to pathogenic antigens are initiated. This immunological function induced by cells within the LN is an extensive area of research. To clarify the general function of LN, to identify cell populations within the lymphatic system and to describe the regeneration of the lymph vessels, the experimental surgical technique of LN dissection has been established in various animal models. In this review different research areas in which LN dissection is used as an experimental tool will be highlighted. These include regeneration studies, immunological analysis and studies with clinical questions. LN were dissected in order to analyse the different cell subsets of the incoming lymph in detail. Furthermore, LN were identified as the place where the induction of an antigen-specific response occurs and, more significantly, where this immune response is regulated. During bacterial infection LN, as a filter of the lymph system, play a life-saving role. In addition, LN are essential for the induction of tolerance against harmless antigens, because tolerance could not be induced in LN-resected animals. Thus, the technique of LN dissection is an excellent and simple method to identify the important role of LN in immune responses, tolerance and infection.

Lymphangiogenesis: Molecular mechanisms and future promise

The growth of lymphatic vessels (lymphangiogenesis) is actively involved in a number of pathological processes including tissue inflammation and tumor dissemination but is insufficient in patients suffering from lymphedema, a debilitating condition characterized by chronic tissue edema and impaired immunity. The recent explosion of knowledge on the molecular mechanisms governing lymphangiogenesis provides new possibilities to treat these diseases.

In situ lymph dynamic characterization through lymph nodes in rabbit hind leg: special reference to nodal inflammation

In some lymph nodes, water and water-soluble substances of smaller molecular weight are known to be absorbed into blood vessels, and consequently the protein concentration of lymph within the nodes increases. In this study, we examined pressure-flow relationships of lymph nodes in situ and exchange properties of water and water-soluble substances through the nodes with special reference to inflamed lymph nodes. A lymph perfusion model through the lymph node in situ was constructed by cannulating one of the afferent lymphatics and an efferent lymphatic. Increasing infusion pressure (0 to 150 cmH(2)O) or decreasing outflow pressure (10 to -5 cmH(2)O) in the model caused a significant increase of the lymph outflow rate through the node. This rate was also increased significantly with increases in both intranodal venous pressure (range: control, 20, 30, and 40 mmHg) and prenodal lymph albumin concentration (range: 0%, 2.6%, and 10%). When formyl-Met-Leu-Phe-OH (fMLP)-mediated acute inflammation was produced in the lymph nodes, the lymph outflow rate through the node was significantly decreased. These results indicate that colloid osmotic pressure and hydrostatic pressure within the lymph node may play important roles in the transport of water and water-soluble substances through the node. Acute fMLP-mediated inflammation of lymph nodes also produced a significant decrease of the lymph flow rate through lymph nodes.