Characterization of internodal collecting lymphatic vessel function after surgical removal of an axillary lymph node in mice

Lymphatic vessel network injury reduces local tumor control despite preservation of the tumor-draining lymph node

The lymphatic system plays complex, often contradictory, roles in many cancers, including melanoma; these roles include contributions to tumor cell metastasis and immunosuppression in the tumor microenvironment as well as generation of antitumor immunity. Advancing our understanding of lymphatic vessel involvement in regulating tumor growth and immune response may provide new therapeutic targets or treatment plans to enhance the efficacy of existing therapies. We utilized a syngeneic murine melanoma model in which we surgically disrupted the lymphatic vessel network draining from the tumor to the tumor-draining lymph node (TDLN) while leaving the TDLN intact. Although transport of lymphatic-specific molecular weight tracers to the TDLN remains present after surgery, disruption of the tumor-draining lymphatic vessels results in decreased local tumor control, as reflected in an increase in the rate of tumor growth and reduction in effector-like T cell infiltration into the tumor. Our findings suggest that preservation of the functional tumor-draining lymphatic network may be essential in promoting a robust antitumor immune response.

The effects of postoperative treadmill exercise on rats with secondary lymphedema

Cancer-related lymphedema (LE) is often caused by radiotherapy and surgery such as lymph node dissection (LND). Previous studies have reported that exercise is beneficial to relieve LE, but the changes in the lymphatic system following exercise are still unclear. This study aimed to examine the changes in lymphatic drainage pathways over the exercise period and beneficial effects of exercise in rats with LE. Twelve rats were randomly allocated into exercise and control groups (EG and CG; n = 6 each). To obtain LE, inguinal and popliteal LND followed by 20 Gy irradiation was performed. Treadmill exercise was 30 minutes/day, 5 days/week over the four-week period. Consecutive indocyanine green (ICG) lymphography images were collected and classified into five patterns: i) linear; ii) splash; iii) stardust; iv) diffuse, and v) none. Ankle thickness was measured weekly. Histopathological evaluation was performed to examine the skin thickness, collagen area fraction (%) and lymphatic vessel density in harvested tissue. ICG lymphography exhibited more linear and splash patterns in the EG at week 3. The difference of swelling between both groups was significantly different at week 4 (p = 0.016). Histopathologic data revealed a thinner epidermis (p = 0.041) and dermis (p = 0.002), lower collagen area fraction (%, p = 0.002), and higher lymph vessel density (p = 0.002) in the EG than the CG. In conclusion, we found that postoperative exercise can facilitate improvement in lymphatic fluid retention in the lymphedema rat model, resulting in improvement of pathological conditions in the lymphatic system.

Current Advancements in Animal Models of Postsurgical Lymphedema: A Systematic Review

Significance: Secondary lymphedema is a debilitating disease caused by lymphatic dysfunction characterized by chronic swelling, dysregulated inflammation, disfigurement, and compromised wound healing. Since there is no effective cure, animal model systems that support basic science research into the mechanisms of secondary lymphedema are critical to advancing the field. Recent Advances: Over the last decade, lymphatic research has led to the improvement of existing animal lymphedema models and the establishment of new models. Although an ideal model does not exist, it is important to consider the strengths and limitations of currently available options. In a systematic review adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we present recent developments in the field of animal lymphedema models and provide a concise comparison of ease, cost, reliability, and clinical translatability. Critical Issues: The incidence of secondary lymphedema is increasing, and there is no gold standard of treatment or cure for secondary lymphedema. Future Directions: As we iterate and create animal models that more closely characterize human lymphedema, we can achieve a deeper understanding of the pathophysiology and potentially develop effective therapeutics for patients.

Manual lymphatic drainage with or without fluoroscopy guidance did not substantially improve the effect of decongestive lymphatic therapy in people with breast cancer-related lymphoedema (EFforT-BCRL trial): a multicentre randomised trial

QUESTIONS

When added to decongestive lymphatic therapy (DLT), what is the effect of fluoroscopy-guided manual lymphatic drainage (MLD) versus traditional MLD or placebo MLD for the treatment of breast cancer-related lymphoedema (BCRL)?

DESIGN

Multicentre, three-arm, randomised controlled trial with concealed allocation, intention-to-treat analysis and blinding of assessors and participants.

PARTICIPANTS

At five hospitals in Belgium, 194 participants with unilateral chronic BCRL were recruited.

INTERVENTION

All participants received standard DLT (education, skin care, compression therapy and exercises). Participants were randomised to also receive fluoroscopy-guided MLD (n = 65), traditional MLD (n = 64) or placebo MLD (n = 65). Participants received 14 sessions of physiotherapy during the 3-week intensive phase and 17 sessions during the 6-month maintenance phase. Participants performed self-management on the other days.

OUTCOME MEASURES

All outcomes were measured: at baseline; after the intensive phase; after 1, 3 and 6 months of maintenance phase; and after 6 months of follow-up. The primary outcomes were reduction in excess volume of the arm/hand and accumulation of excess volume at the shoulder/trunk, with the end of the intensive phase as the primary endpoint. Secondary outcomes included daily functioning, quality of life, erysipelas and satisfaction.

RESULTS

Excess lymphoedema volume decreased after 3 weeks of intensive treatment in each group: 5.3 percentage points of percent excessive volume (representing a relative reduction of 23.3%) in the fluoroscopy-guided MLD group, 5.2% (relative reduction 20.9%) in the traditional MLD group and 5.4% (relative reduction 24.8%) in the placebo MLD group. The effect of fluoroscopy-guided MLD was very similar to traditional MLD (between-group difference 0.0 percentage points, 95% CI -2.0 to 2.1) and placebo MLD (-0.2 percentage points, 95% CI -2.1 to 1.8). Fluid accumulated at the shoulder/trunk in all groups. The average accumulation with fluoroscopy-guided MLD was negligibly less than with traditional MLD (-3.6 percentage points, 95% CI -6.4 to -0.8) and placebo MLD (-2.4 percentage points, 95% CI -5.2 to 0.4). The secondary outcomes also showed no clinically important between-group differences.

CONCLUSION

In patients with chronic BCRL, MLD did not provide clinically important additional benefit when added to other components of DLT.

REGISTRATION

NCT02609724.

Comparison of normal hindlimb lymphatic systems in rats with detours present after lymphatic flow blockage

In the present study, we aimed to identify the normal hindlimb lymphatic systems in rats and compare them with the detours after lymphatic flow blockage. The lymphatic systems of the hindlimbs of normal rats were investigated via lymphography using a near-infrared fluorescence imaging system. The lymphatic vessels were stained using Evans Blue. The lymphatic flow was blocked through lymphatic vessel ligation combined with inguinal and popliteal lymph node dissection. Detours that appeared after 30 days were visualized using lymphography and immunostaining with anti-podoplanin antibodies. Three main results were obtained in the present study. First, the deep medial system, the superficial medial system, a connection between the superficial and deep medial lymphatic systems, and the superficial lateral system, were elucidated. Second, three types of detours, namely the detour of the lateral abdomen, the detour to the lymphatic vessel near the midline of the abdomen, and the detour to the contralateral inguinal lymph node, were identified after lymphatic flow blockage. Lastly, detours were located in the fatty layer above the panniculus carnosus muscle and their lumina were wide. The histology suggested that the detour was a pre-collecting lymphatic vessel. Lymphatic routes in the rat hindlimbs after lymphatic flow blockage were different from those of the normal rat lymphatic system. It was suggested that the detour is a pre-collecting lymphatic vessel and that encouraging its development may be a new method of simple lymphatic drainage.

Impaired Peripheral Lymphatic Function and Cerebrospinal Fluid Outflow in a Mouse Model of Alzheimer's Disease

Cerebrospinal fluid (CSF) outflow from the brain occurs through absorption into the arachnoid villi and, more predominantly, through meningeal and olfactory lymphatics that ultimately drain into the peripheral lymphatics. Impaired CSF outflow has been postulated as a contributing mechanism in Alzheimer's disease (AD). Herein we conducted near-infrared fluorescence imaging of CSF outflow into the peripheral lymph nodes (LNs) and of peripheral lymphatic function in a transgenic mouse model of AD (5XFAD) and wild-type (WT) littermates. CSF outflow was assessed from change in fluorescence intensity in the submandibular LNs as a function of time following bolus, an intrathecal injection of indocyanine green (ICG). Peripheral lymphatic function was measured by assessing lymphangion contractile function in lymphatics draining into the popliteal LN following intradermal ICG injection in the dorsal aspect of the hind paw. The results show 1) significantly impaired CSF outflow into the submandibular LNs of 5XFAD mice and 2) reduced contractile frequency in the peripheral lymphatics as compared to WT mice. Impaired CSF clearance was also evidenced by reduction of fluorescence on ventral surfaces of extracted brains of 5XFAD mice at euthanasia. These results support the hypothesis that lymphatic congestion caused by reduced peripheral lymphatic function could limit CSF outflow and may contribute to the cause and/or progression of AD.

The Development and Treatment of Lymphatic Dysfunction in Cancer Patients and Survivors

Breast-cancer-acquired lymphedema is routinely diagnosed from the appearance of irreversible swelling that occurs as a result of lymphatic dysfunction. Yet in head and neck cancer survivors, lymphatic dysfunction may not always result in clinically overt swelling, but instead contribute to debilitating functional outcomes. In this review, we describe how cancer metastasis, lymph node dissection, and radiation therapy alter lymphatic function, as visualized by near-infrared fluorescence lymphatic imaging. Using custom gallium arsenide (GaAs)-intensified systems capable of detecting trace amounts of indocyanine green administered repeatedly as lymphatic contrast for longitudinal clinical imaging, we show that lymphatic dysfunction occurs with cancer progression and treatment and is an early, sub-clinical indicator of cancer-acquired lymphedema. We show that early treatment of lymphedema can restore lymphatic function in breast cancer and head and neck cancer patients and survivors. The compilation of these studies provides insights to the critical role that the lymphatics and the immune system play in the etiology of lymphedema and associated co-morbidities.

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.

Protocol of a randomised controlled trial regarding the effectiveness of fluoroscopy-guided manual lymph drainage for the treatment of breast cancer-related lymphoedema (EFforT-BCRL trial)

OBJECTIVES

Lymphoedema is a dreadful complication following breast cancer therapy. According to the International Society of Lymphology, the consensus treatment for breast cancer-related lymphoedema (BCRL) is the decongestive lymphatic therapy. This is a two-phase treatment and combines different treatment modalities including skin care, manual lymphatic drainage (MLD), compression therapy and exercise. However, the additional effect of MLD is debated since pooled data only demonstrated a limited non-significant additional value. A possible explanation is that in previous studies MLD has been applied blind, without knowledge of patient-specific lymphatic routes of transport. In addition, the MLD hand manoeuvres used by the therapists in previous studies, possibly did not optimally stimulate lymphatic transport. Recently, near-infrared fluorescence imaging has been introduced to visualise the superficial lymphatic network which allows MLD at the most needed location. The aim of the present study is to determine the effectiveness of the fluoroscopy-guided MLD, additional to the other parts of the decongestive lymphatic therapy and compared to the traditional or a placebo MLD, in the treatment of BCRL.

STUDY DESIGN

A three-arm double-blinded randomised controlled trial will be conducted in different university hospitals in Belgium. Based on a sample size calculation, 201 participants with chronic BCRL stage 1 or 2 of the arm or hand, with at least 5% difference between both sides (corrected for hand dominance) need to be recruited. All participants receive the standard treatment: skin care, compression therapy and exercises. The intervention group additionally receives fluoroscopy-guided MLD. One control group additionally receives the traditional 'blind' MLD and a second control group receives a placebo MLD. All subjects receive 3 weeks of daily intensive treatments and 6 months of maintenance treatment. Follow-up period is 6 months. The primary outcomes are the reduction in lymphoedema volume of the arm/hand and the change in stagnation of lymph fluid at level of the shoulder/trunk.