The Potential for Molecular Treatment Strategies in Lymphatic Disease

Lymphatic Development and Implications for Diagnosis and Therapy

The lymphatic system was first described in the 17th century independently by Olaus Rudbeck and Thomas Bartholin. Since then, there has been deep-seated fascination with its development, function, and dysfunction.

Vascular endothelial growth factor C treatment for mouse hind limb lymphatic revascularization

Spontaneous lymphatic revascularization is a challenge and the establishment of new therapeutic strategies may improve life quality for patients suffering from lymphatic disorders. This study was designed to verify if VEGFC treatment improves lymphatic vascularization in a time‐dependent manner in mouse hindlimb (HL) after resection of the inguinal lymph node. Lymphatic vascular density (Vv) and length (Lv) were evaluated by stereology after immunohistochemistry. The control Group (CG) was not manipulated but received saline instead of VEGFC treatment. The surgery Group (SG) had the left inguinal lymph node resected but did not received VEGFC treatment. VEGFC Treated Group (TG) had the node resected and received VEGFC treatment. VEGFC and VEGFR3 local expression were assessed by qPCR. There was an effect of time over Vv and Lv in the SG and significant difference between CG and SG in the regions studied (proximal, medium and distal regions) of the left HL (LHL). The Lv showed significant difference between CG and SG only in the medium region. The Vv and the Lv for TG were higher than the other groups. VEGFC and VEGFR3 gene expression presented time effect in all regions of the LHL for SG and TG. Both VEGFC and VEGFR3 gene expression presented significant difference between CG and SG, between SG and TG and between CG and TG. This study showed significant decrease in lymphatic vascularization in the left hindlimb of mice after surgical removal of the inguinal lymph node and adjacent lymphatic vessels. Exogenous VEGFC could recover lymphatic vascularization through stimulating neolymphangiogenesis.

French Oak Wood (Quercus robur) Extract (Robuvit) in Primary Lymphedema: A Supplement, Pilot, Registry Evaluation

The aim of this pilot supplement study was the evaluation of an oak wood extract (Robuvit, Quercus robur [QR], Horphag Research) in an 8-week registry study on lymphatic signs in primary lymphedema. Subjects with primary lymphedema confined to a single leg without skin changes or ulcerations were followed for at least 8 weeks. Lymphedema was mainly present distally (below the knee). Three groups were formed: one group used only the standard management for lymphedema; one used the same management plus 300 mg Robuvit; and one used the standard management plus 600 mg of Robuvit. The three groups were comparable. After 8 weeks the variation in leg volume was on average -6.2% with standard management, -15% in the QR 300 mg group, and -18.9% in the 600 mg group. The edema score was also significantly lower at 8 weeks in the two QR groups. The variation in proteins in the interstitial fluid in comparison with initial values was -14.8% in controls in comparison with -29.9% in QR 300 mg group and -36.9% in QR 600 mg group. Skin flux significantly improved (increased) in the two QR groups. Ultrasound pretibial skin thickness was decreased on average 6% in controls versus 10.3% in the low-dose QR group and 11.8% in the higher dose group. Perimalleolar thickness was decreased 7% in controls and more in the two QR groups. Ankle circumference was decreased 4.4% in controls and more in the two supplement groups. This pilot registry indicates that Robuvit can be effective in the management of primary lymphedema. More patients and longer evaluation periods are needed.

Molecular analysis and differentiation capacity of adipose-derived stem cells from lymphedema tissue

BACKGROUND

Many breast cancer patients are plagued by the disabling complication of upper limb lymphedema after axillary surgery. Conservative treatments using massage and compression therapy do not offer a lasting relief, as they fail to address the chronic transformation of edema into excess adipose tissue. Liposuction to address the adipose nature of the lymphedema has provided an opportunity for a detailed analysis of the stromal fraction of lymphedema-associated fat to clarify the molecular mechanisms for this adipogenic transformation.

METHODS

Adipose-derived stem cells were harvested from human lipoaspirate of the upper extremity from age-matched patients with lymphedema (n = 3) or subcutaneous adipose tissue from control patients undergoing cosmetic procedures (n = 3). Immediately after harvest, adipose-derived stem cells were analyzed using single-cell transcriptional profiling techniques. Osteogenic, adipogenic, and vasculogenic gene expression and differentiation were assessed by quantitative real-time polymerase chain reaction and standard in vitro differentiation assays.

RESULTS

Differential transcriptional clusters of adipose-derived stem cells were found between lymphedema and subcutaneous fat. Interestingly, lymphedema-associated stem cells had a much higher adipogenic gene expression and enhanced ability to undergo adipogenic differentiation. Conversely, they had lower vasculogenic gene expression and diminished capability to form tubules in vitro, whereas the osteogenic differentiation capacity was not significantly altered.

CONCLUSIONS

Adipose-derived stem cells from extremities affected by lymphedema appear to exhibit transcriptional profiles similar to those of abdominal adipose-derived stem cells; however, their adipogenic differentiation potential is strongly increased and their vasculogenic capacity is compromised. These results suggest that the underlying pathophysiology of lymphedema drives adipose-derived stem cells toward adipogenic differentiation.

Update on the biology and treatment of lymphedema

OPINION STATEMENT

The past decade has produced an explosion of insights into lymphatic vascular development and structural biology and, in parallel, into the function of the lymphatics in health and in disease. In lymphedema, there is a spectrum that extends from primary (heritable) to acquired causes of disease. The diagnosis of lymphatic edema implicates a very specific treatment approach that is predicated upon the favorable impact of physiotherapy upon lymph flow and protein clearance from the edematous zones of the body. The recognition of the unique biology that accompanies lymphatic causes of edema has stimulated new research directions that are likely to translate into exciting new pharmacologic and molecular approaches to diagnosis and treatment.

Biomarkers of Lymphatic Function and Disease

Substantial advances have accrued over the last decade in the identification of the processes that contribute to lymphatic vascular development in health and disease. Identification of distinct regulatory milestones, from a variety of genetic models, has led to a stepwise chronology of lymphatic development. Several molecular species have been identified as important tissue biomarkers of lymphatic development and function. At present, vascular endothelial growth-factor receptor (VEGFR)-3/VEGF-C/VEGF-D signaling has proven useful in the identification of clinical lymphatic metastatic potential and the assessment of cancer prognosis. Similar biomarkers, to be utilized as surrogates for the assessment of inherited and acquired diseases of the lymphatic circulation, are actively sought, and will represent a signal advance in biomedical investigation.

The unique biology of lymphatic edema

Sadly, the subject of lymphatic vascular insufficiency continues to engender relative neglect by health care professionals, which represents a source of frustration and fear among patients. A re-consideration of the unique, complex biology of lymphatic vascular disorders has the capacity both to reinvigorate interest and facilitate the implementation of the correct, existing treatment interventions for individuals affected by these disease states. While most of this complex lymphatic biology remains somewhat elusive, growing insights into the molecular mechanisms of lymphatic development and repair have been instructive. Present and future considerations in lymphedema diagnosis and management must acknowledge the unique tissue biology of this disorder. Many changes are unique to the lymphatic mechanisms of chronic edema. The profound stimulus to collagen deposition in the integument seems to be unique to chronic lymphatic edema, although this biology remains largely unexplicated. Several lines of evidence also suggest that lymphatic function has a unique and important influence upon adipose biology. Molecular investigation of murine models of human acquired lymphedema are beginning to shed light on these processes. Such focused mechanistic, approaches to the study of lymphedema and other lymphatic diseases are vital, as we attempt to expand our insights into the complex biology of lymphedema and its potential responsiveness to pharmacologic control and molecular intervention, prevention, and reversal.

Molecular targets for therapeutic lymphangiogenesis in lymphatic dysfunction and disease

The convergence of multiple disciplines upon the study of the lymphatic vasculature has invigorated a renaissance of research, using powerful investigative tools and an exponential growth of interest in this historically underappreciated system. Fundamental discoveries in lymphatic development have yielded relevant animal models for vexing clinical diseases that suffer from nonexistent of minimally effective treatments. Inherited and acquired lymphedema represent the current crux of research efforts to identify potential molecular therapies born from these early discoveries. The importance of the lymphatic system is, however, not limited to lymphedema but encompasses a diverse spectrum of human disease including inflammation and cancer metastasis. As the lymphatic vasculature continues to benefit from fruits of biomedical investigation, translation of mechanistic insights into targeted, rationally-conceived therapeutics will be become a reality.

Diagnosis and management of lymphatic vascular disease

The lymphatic vasculature is comprised of a network of vessels that is essential both to fluid homeostasis and to the mediation of regional immune responses. In health, the lymphatic vasculature possesses the requisite transport capacity to accommodate the fluid load placed upon it. The most readily recognizable attribute of lymphatic vascular incompetence is the presence of the characteristic swelling of tissues, called lymphedema, which arises as a consequence of insufficient lymph transport. The diagnosis of lymphatic vascular disease relies heavily upon the physical examination. If the diagnosis remains in question, the presence of lymphatic vascular insufficiency can be ascertained through imaging, including indirect radionuclide lymphoscintigraphy. Beyond lymphoscintigraphy, clinically-relevant imaging modalities include magnetic resonance imaging and computerized axial tomography. The state-of-the-art therapeutic approach to lymphatic edema relies upon physiotherapeutic techniques. Complex decongestive physiotherapy is an empirically-derived, effective, multicomponent technique designed to reduce limb volume and maintain the health of the skin and supporting structures. The application of pharmacological therapies has been notably absent from the management strategies for lymphatic vascular insufficiency states. In general, drug-based approaches have been controversial at best. Surgical approaches to improve lymphatic flow through vascular reanastomosis have been, in large part, unsuccessful, but controlled liposuction affords lasting benefit in selected patients. In the future, specifically engineered molecular therapeutics may be designed to facilitate the controlled regrowth of damaged, dysfunctional, or obliterated lymphatic vasculature in order to circumvent or mitigate the vascular insufficiency that leads to edema and tissue destruction.

Lymphatic Tissue Transplant in Lymphedema—A Minimally Invasive, Outpatient, Surgical Method: A 10-Year Follow-up Pilot Study

Lymphedema is mainly characterized by swelling, fibrosis, and nonpitting edema. The aim of this study was evaluation of the long-term (10 years) effects of autologus lymphatic tissue implant in lymphedema. Lymphatic tissue from 9 patients (harvested form the same patient in areas not affected by lymphedema) was reimplanted into the affected limb, and these patients were followed for 10 years. Lymph nodes were harvested at the neck, axillary, or inguinal space (contralateral limb). Results showed that limb volume was decreased in the treatment group vs. controls. In ultrasound, black, low density, lymphatic spaces were visible in 100% of patients at inclusion but in only 23% of these subjects at 10 years. Thus, this early report proposes a new, minimally invasive method to improve lymphedema. Studies in progress will indicate the role of lymphatic transplant in the management of lymphedema and the best indications for this method.

Lymphedema of the lower extremity: is it genetic or nongenetic?

Lymphedema of the lower extremities is a diagnostic challenge. Exclusion of secondary causes of limb swelling and secondary lymphedema is the initial step. Primary lymphedema is classified into idiopathic and familial (hereditary) subgroups. Hereditary lymphedema can be nonsyndromic or associated with congenital anomalies or with abnormal physical findings. A 13-year-old girl presented with unilateral lower extremity lymphedema. Her medical and family history was unremarkable. The physical examination was negative for dysmorphic features and congenital anomalies. Lymphoscintigraphy showed no evidence of lymph flow in the left lower extremity, which persisted at the delayed 2-hour image. A comprehensive clinical and family history that includes a thorough physical examination are the mainstays of the medical assessment of lymphedema in children. Isotopic lymphoscintigraphy is generally considered the gold standard for confirmation of the diagnosis. This article discusses the differential diagnosis, reviews the literature, and suggests a simplified and an updated flowchart for the classification of unilateral limb lymphedema in children.

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.

Indirect magnetic resonance lymphangiography to assess lymphatic function in experimental murine lymphedema

BACKGROUND

Recently, indirect magnetic resonance lymphangiography with gadolinium (Gd) has been demonstrated to offer the potential for safe, high-resolution visualization of the lymphatic vessels, in addition to the lymph nodes. In this study, the potential utility of indirect Gd contrast magnetic resonance imaging of lymphatic vascular function was investigated in the murine tail. Functional imaging of healthy mice is contrasted with the findings in experimentally-induced lymphatic vascular insufficiency.

METHODS

Postsurgical lymphedema was experimentally created in the murine tail. Normal and lymphedematous mouse tails were imaged following direct subcutaneous administration of Gadolinium-DTPA, 0.1 mmol/kg. Images were obtained in axial and coronal planes with a T1-weighted spin echo inversion-recovery sequence.

RESULTS

In the normal tail, both of the bilateral major collecting lymphatics were clearly visualized as the Gd tracer was cleared from the interstitial compartment. In contrast, the Gd tracer accumulated at the prior surgical site in the lymphedematous tail. Quantitative assessment of Gd clearance demonstrates that accumulation of Gd correlates with the impedance to lymph flow proximal to the site of surgical lymphatic ablation.

CONCLUSION

Magnetic resonance is a feasible and reliable method to be applied to quantitative functional imaging of the lymphatic vasculature in experimental models of lymphedema.

Molecular Regulation of Microlymphatic Formation and Function: Role of Nitric Oxide

Inhibition of lymphangiogenesis prevents lymphatic cancer metastasis, whereas induction of lymphangiogenesis alleviates lymphedema in experimental animal models. The number of known molecular players that govern the formation and function of the microlymphatic system is growing. Here, we review the role of nitric oxide within the regulation of lymphatic formation and function and point out key unanswered questions for its translation into clinical therapy.