Lymph Stasis Research Articles

Lymphedema and subclinical lymphostasis (microlymphedema) facilitate cutaneous infection, inflammatory dermatoses, and neoplasia: A locus minoris resistentiae

Whether primary or secondary, lymphedema is caused by failure to drain protein-rich interstitial fluid. Typically affecting a whole limb, it has become apparent that lymphedema can also affect localized regions of the skin, or it can be clinically silent but histologically evident, denoted by dilated lymphangiectases (latent lymphedema). Chronic lymph stasis has numerous consequences, including lipogenesis, fibrosis, inflammation, lymphangiogenesis, and immunosuppression. For example, lymphedema’s disruption of immune cell trafficking leads to localized immune suppression, predisposing the area affected to chronic inflammation, infection (cellulitis and verrucosis), and malignancy (angiosarcoma and nonmelanoma skin cancer). The pathogenesis of lymphedema is reviewed and exemplified by describing how a combination of lymph stasis–promoting factors such as trauma, obesity, infection, and inflammatory disorders produces localized elephantiasis; furthermore, the finding of lymphangiectases is found to be common in numerous dermatologic disorders and argued to play a role in their pathogenesis. Lastly, it is discussed how antigen burden, which is controlled by lymphatic clearance, affects the immune response, resulting in immune tolerance, immunopathology, or normal adaptive immunity.

The immunocompromised district in dermatology: A unifying pathogenic view of the regional immune dysregulation

Besides the systemic immune deficiency, a sectorial default in immune control may occur in immunocompetent subjects. This regional immune defect can appear and remain confined to differently damaged skin areas, lately labeled immunocompromised districts (ICDs).An ICD is a skin area more vulnerable than the rest of the body for genetic or acquired reasons. Its vulnerability mainly consists in a local dysregulation of the immune control, which often facilitates (but sometimes hinders) the local onset of immunity-related eruptions or skin disorders.The factors responsible for localized immune dysregulation are multifarious, being represented by chronic lymphatic stasis, herpetic infections, ionizing or ultraviolet (UV) radiations, burns, all sorts of trauma (especially amputation), tattooing, intradermal vaccinations, and others of disparate nature (eg, paralytic stroke, poliomyelitis). Whatever the cause, in time an ICD may become a vulnerable site, prone to developing opportunistic infections, tumors, or dysimmune reactions (often of granulomatous type), strictly confined to the district itself; however, the opposite may also occur with systemic immune disorders or malignancies that selectively spare the district. In any case, the immunologic behavior of an ICD is different from that of the rest of the body. The pathomechanisms involved in this sectorial immune destabilization may reside in locally hampered lymph drainage that hinders the normal trafficking of immunocompetent cells (eg, chronic lymphedema, posttraumatic lymph stasis) or in a damage to sensory nerve fibers that release immunity-related peptides (eg, herpetic infections, carpal tunnel syndrome), or in both conditions (eg, amputation stump, radiation dermatitis).The ICD is a conceptual entity with no definite shape or dimension. It may take an extremely variable form and extent depending on the causative agent, ranging from a minimal area (eg, intradermal vaccination) or a small area (eg, herpes simplex infection), through a wide area (eg, radiotherapy), a bandlike segment (eg, skin mosaicism, herpes zoster infection), or an acral area (eg, carpal tunnel syndrome), up to a whole limb (eg, Stewart-Treves syndrome) or even an entire half body (eg, brain stroke).Varied newly coined terminology can be used to indicate the specific cause each time that it is responsible for a regional immune dysregulation. The advantage of the umbrella term ICD is that it encompasses all the possible causes involved in a local immune destabilization.An ICD may have a congenital or a postnatal origin, and interesting similarities between the two forms exist. An ICD may also take place in patients with a preexisting systemic immune deficiency, thus creating a more vulnerable site in an already vulnerable patient.Identifying a cutaneous ICD in a given patient is an important standpoint for both diagnostic and prevention purposes. This can be proven by the educative clinical examples that are reported here.

Redraping of the fat and eye lift for the correction of the tear trough

IntroductionTear trough deformity is very difficult to correct. It can appear at relatively young age and it deepens over the years due to laxity and loss of structural support.We describe a technique for the correction of tear trough deformity and mid-face laxity by means of redraping blepharoplasty and lateral “eye lift”. Materials and methodsUpper lid markings were made and removal of the excess skin was employed. The herniated fat was removed from the nasal fat pad.Using a subciliary incision the dissection was completed at the level of the orbital rim and the fat was repositioned with 5-0 Monocryl (poliglecaprone 25, Ethicon) sutures at the inner canthus to correct the tear trough. Subsequently, a canthopexy performed to secure the lower eyelid. We then dissected the cheek over the periosteum of the zygomatic bone-arch and the flap was suspended through a tunnel at the periosteum of the upper-lateral orbit by 5-0 Monocryl (poliglecaprone 25, Ethicon) suture. ResultsThirty-five procedures were performed between 2009 and 2013. Patients were followed for at least one year. Successful correction of the tear trough deformity with middle face elevation was achieved in all patients. Sclera show was noted in 7 patients but resolved over 3–6 months period with no surgical intervention. Diplopia was noted in 1 patient probably due to oedema and was released 4 weeks after the operation. The oedema was prolonged (more than 1.5 month) in 10 patients probably due to the lymphatic stasis. Conjunctivitis was also noted in 2 patients and was released by conservative treatment. ConclusionOur technique of redraping blepharoplasty and mid-face lift describes a relatively new approach for the correction of the tear trough deformity and middle face laxity. It shows stable results for up to 4 years although longer follow-up is needed to confirm the stability of the correction.

Differences in cardiovascular reactivity to mental stress in athletes vs. sedentary subjects

Tear trough deformity is very difficult to correct. It can appear at relatively young age and it deepens over the years due to laxity and loss of structural support.We describe a technique for the correction of tear trough deformity and mid-face laxity by means of redraping blepharoplasty and lateral “eye lift”.Upper lid markings were made and removal of the excess skin was employed. The herniated fat was removed from the nasal fat pad.Using a subciliary incision the dissection was completed at the level of the orbital rim and the fat was repositioned with 5-0 Monocryl (poliglecaprone 25, Ethicon) sutures at the inner canthus to correct the tear trough. Subsequently, a canthopexy performed to secure the lower eyelid. We then dissected the cheek over the periosteum of the zygomatic bone-arch and the flap was suspended through a tunnel at the periosteum of the upper-lateral orbit by 5-0 Monocryl (poliglecaprone 25, Ethicon) suture.Thirty-five procedures were performed between 2009 and 2013. Patients were followed for at least one year. Successful correction of the tear trough deformity with middle face elevation was achieved in all patients. Sclera show was noted in 7 patients but resolved over 3–6 months period with no surgical intervention. Diplopia was noted in 1 patient probably due to oedema and was released 4 weeks after the operation. The oedema was prolonged (more than 1.5 month) in 10 patients probably due to the lymphatic stasis. Conjunctivitis was also noted in 2 patients and was released by conservative treatment.Our technique of redraping blepharoplasty and mid-face lift describes a relatively new approach for the correction of the tear trough deformity and middle face laxity. It shows stable results for up to 4 years although longer follow-up is needed to confirm the stability of the correction.

Lymphangiogenesis and Angiogenesis in Abdominal Aortic Aneurysm

The pathogenesis of abdominal aortic aneurysm (AAA) is characterized to be inflammation-associated degeneration of vascular wall. Neovascularization is regularly found in human AAA and considered to play critical roles in the development and rupture of AAA. However, little is known about lymphangiogenesis in AAA. The purpose of this study was to demonstrate both angiogenesis and lymphangiogenesis in AAA. Abdominal aortic tissue was harvested either from autopsy (control group) and during open-repair surgery for AAA (AAA group). Adventitial lymphatic vasa vasorum was observed in both groups, but seemed to be no significant morphological changes in AAA. Immunohistochemical studies identified infiltration of lymphatic vessel endothelial hyaluronan receptor (LYVE) −1, vascular endothelial growth factor (VEGF)-C, and matrix metalloproteinase (MMP)-9-positive macrophages and podoplanin and Prox-1-positive microvessels in the intima/media in AAA wall, where hypoxia-inducible factors (HIF)-1α was expressed. VEGF-C and MMP-9 were not expressed in macrophages infiltrating in the adventitia. Intraoperative indocyanine green fluorescence lymphography revealed lymph stasis in intima/medial in AAA. Fluorescence microscopy of the collected samples also confirmed the accumulation of lymph in the intima/media but not in adventitia. These results demonstrate that infiltration of macrophages in intima/media is associated with lymphangiogenesis and angiogenesis in AAA. Lymph-drainage appeared to be insufficient in the AAA wall.

HF ultrasound vs PET-CT and telethermography in the diagnosis of In-transit metastases from melanoma: a prospective study and review of the literature

Over the past several years the incidence of cutaneous melanoma has rapidly increased. This tumor develops often in-transit metastases that significantly reduce patient survival at 5 years. To improve prognosis and quality of life in patients with melanoma metastases, a mini invasive procedure like electrochemotherapy (ECT) is adopted to remove superficial tissue lesions. To detect the melanoma metastases, high frequency (HF) ultrasound (US) is used. This technique, though, can be time-consuming and it needs an expert operator and a high performing machine. Therefore, we asked whether the US could be replaced or integrated with other less time-consuming techniques such as 18-FDG positron emission tomography/computed tomography (PET-CT) and telethermography (TT). Fifteen patients (4 males and 11 females - age range: 63–91) affected whit advanced stage melanoma were enrolled. They presented 52 in-transit metastases as detected by the three techniques used, HF-US, PET/CT and TT within 30 days before ECT. All the 52 lesions were detected by HF-US (100%), 24/52 were detected by PET-CT (42,6%) and 15/52 were detected by TT (27,7%). PET-CT reported 3.7% false positives, while no false positive were reported by TT. As US detected 100% lesions, compared to the other two techniques used, US, along with clinical examination, has still to be considered as gold standard in the diagnosis of metastatic lesions. US, associated with an exhaustive anamnesis and accurate clinical examination, cannot be replaced by either PET-CT or TT. When US performing devices and experienced operators are not available, though, it is highly recommended to integrate US with at least one of the other techniques. Under certain circumstances, as in the case of obese and non-collaborating patients or in patients with lymphatic stasis, these techniques should be integrated to obtain exact in-transit metastases evaluation.

Re-evaluation of qualitative lymphangioscintigraphic findings in secondary lower extremity lymphedema

To re-evaluate whether qualitative lymphangioscintigraphy (LAS) findings are sensitive enough to diagnose or classify the clinical severity of lower extremity lymphedema. LAS was performed in 78 extremities with lymphedema and 24 extremities without lymphedema between April, 2009 and March, 2012. We assessed the proportion of extremities in which there was no visual evidence of the ilioinguinal lymph nodes (LN-60) or the lymphatic trunk (Tr-60) 60 min after tracer injection, the number of visualized ilioinguinal lymph nodes (#LN), and the proportion of extremities with dermal backflow (pDBF) and lymph stasis (pLS). These were associated with the International Society of Lymphology (ISL) clinical stage. LN-60, Tr-60, #LN, pDBF, and pLS, especially when extending into both the thigh and lower leg, were significantly associated with the ISL stage. The sensitivity of LN-60, Tr-60, and #LN <2 for diagnosing lymphedema was 49, 47, and 59 %, respectively, with no significant difference among these parameters for consecutive ISL stages. None of the above measures was sufficiently sensitive to diagnose lymphedema or classify the severity of the disease; however, each of these criteria can aid in diagnosis, by excluding other diseases and assessing disease pathophysiology.

Pressures and Timing of Intermittent Pneumatic Compression Devices for Efficient Tissue Fluid and Lymph Flow in Limbs with Lymphedema

Pneumatic compression of tissues with lymph stasis is, aside from the manual massage, a commonly used therapeutic modality in limb lymphedema. A number of pneumatic devices have been constructed. There is lack of reports of comparative studies determining inflation pressure levels, inflation/deflation cycle times, and total pumping times. We tried to answer the question how high compression pressure and how long compression timing should be applied to the limb soft tissues to reach tissue fluid (TF) head pressure above 30 mmHg, necessary to initiate proximal flow. TF pressures were measured subcutaneously during intermittent pneumatic compression in the lymphedematous limbs stage II to IV. Pressures of 50, 80, and 120 mmHg and timing 5, 20, and 50 sec were applied. a) the TF head pressures were lower than those in inflated chambers, b) inflation time of 5 and 20 sec was not long enough to generate TF head pressures above 30 mmHg, even if the compression pressures were as high as 120 mmHg, c) the 50 sec timing allowed to reach head pressures above 30 mmHg; however, they remained always lower than in the compression chamber, d) TF head pressures differed at various levels of the limb depending on the soft tissue mass, e) deflation of the inflated whole sleeve for 5 and 20 sec was followed by high end pressures, whereas that of 50 sec brought about pressure drop to 0, facilitating refilling with TF of the distal parts of the massaged limb. Our observations point to the necessity of applying high pressures and compression times over 50 sec, to generate effective TF pressures and provide enough time for creating TF flow. Short inflation times generate TF pressures as in one-chamber devices that preclude its effectiveness compared to the multi-chamber devices.

The Lymphatics and the Inflammatory Response: Lessons Learned from Human Lymphedema

In lymphedema, there is a profound predisposition to infection with bacterial pathogens. It therefore seems appropriate to reconsider our unique functional definition of the lymphatic structures within a circulatory construct. While the lymphatics unquestionably fulfill a vital circulatory function, it seems more appropriate to view this complex network, comprised both of endothelial-lined vessels and of lymphoid tissue, as the nexus between the circulatory and immune systems. Viewed in this fashion, it becomes evident that the complex biology of regional lymphatic disruption is a manifestation of the interplay between these two vital bodily functions. Experimental lymph stasis in murine model has been utilized to effectively demonstrate the pathological attributes of human lymphedema, namely, inflammation, fat deposition, and fibrosis. Large-scale transcriptional corroborates the role of inflammatory mechanisms. The murine studies have set the stage for subsequent translational investigation of human lymphedema. Many of the gene expression pathways invoked by lymphedema are relevant to the inflammatory response and have provided a pragmatic approach to the successful identification of potentially relevant circulating biomarkers for human lymphedema.

Multidisciplinary Approaches to the Management of Breast-Cancer-Related Lymphedema

Breast-cancer-related lymphedema is a significant morbidity mostly observed following primary treatments for breast cancer (surgery, radiation, and chemotherapy) (1). Multiple complications might accompany lymphedema including cosmetic deformity, psychological disorders, consistent pain, and consequently decreased quality of life. Treatment mostly focuses on reducing edema and its subsequent pain; however, no definite treatment has been hitherto introduced (2). Surgical approaches in the management of lymphedema are efficient including physiologic methods (e.g. flap interposition, lymph transfer, and lymphatic bypass) and reductive techniques (e.g. liposuction) (3). While the former mostly targets at reducing lymphedema through restoring lymphatic drainage, the latter aims at removing fibrofatty tissues which contribute to lymph stasis. Microsurgical variation of lymphatic bypass has gained popularity, in which the accumulated lymph in the lymphedematous limb is redirected. Non-surgical approaches are also practiced in most cases. Comprehensive decongestive therapy, consisting of skin care, exercise, special bandaging and massage, is the most frequently used non-surgical approach efficacy of which could be enhanced in combination with self-management strategies (4). Recently newer techniques have been introduced to tackle lymphedema and its associated pain. Manual lymph drainage, stellate ganglion block, acupuncture, deep oscillation, and pneumatic compression have been efficiently used in several studies. Moreover, significant short-term progress has been reported following other modalities such as low-level laser therapy (5). The complexity of breast-cancer-related lymphedema and its complications necessitates a multidisciplinary approach with the primary goal of easing the burden of the disease on the breast cancer patients. In addition, developing special guidelines encompassing these multidisciplinary approaches and providing educational and training programs for both the patients and their families seems to be pivotal.

Correction: CD4+ Cells Regulate Fibrosis and Lymphangiogenesis in Response to Lymphatic Fluid Stasis

There was an error in the Funding statement. The correct version of the statement is: This study was supported by a Plastic Surgery Education Foundation Research Fellowship: “Mechanisms regulating fibrosis in chronic lymphedema” (Award: $50,000; PI: Jamie Zampell; 100% Effort; Mentor: Babak J. Mehrara, M.D.). Research reported in this publication was supported by the National Heart, Lung, And Blood Institute of the National Institutes of Health under Award Number R01HL111130. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Lymphoedema caused by idiopathic lymphatic thrombus

Primary lymphoedema includes some diseases whose genetic anomaly is detected and others whose pathology is unknown. In this article, we report a lymphatic thrombus found in a limb with lymphoedema during lymphatico-venous anastomosis (LVA). A 32-year-old man was aware of oedema in his left calcar pedis 3 years previously, which appeared without any trigger. Indocyanine green lymphography indicated lymphatic stasis in the left calf and thigh region, and we performed LVA for the patient. During the operation, we found yellow vessels, which were thought to be lymphatic vessels filled with a yellow solid substance, just beneath the superficial fascia at the left ankle. Pathological examination of the thrombi revealed hyaline material mixed with cell components. The cells were categorised as lymphatic endothelial cells, as they were positive for podoplanin. There was no evidence of malignancy. Causes of idiopathic lymphatic thrombus such as this may be one of the causes of so-called primary lymphoedema, and evaluation of such cases may be the first step towards elucidating the mechanisms involved in the development of primary lymphoedema.

Th2 differentiation is necessary for soft tissue fibrosis and lymphatic dysfunction resulting from lymphedema

Lymphedema is a dreaded complication of cancer treatment. However, despite the fact that >5 million Americans are affected by this disorder, the development of effective treatments is limited by the fact that the pathology of lymphedema remains unknown. The purpose of these studies was to determine the role of inflammatory responses in lymphedema pathology. Using mouse models of lymphedema, as well as clinical lymphedema specimens, we show that lymphatic stasis results in a CD4 T-cell inflammation and T-helper 2 (Th2) differentiation. Using mice deficient in T cells or CD4 cells, we show that this inflammatory response is necessary for the pathological changes of lymphedema, including fibrosis, adipose deposition, and lymphatic dysfunction. Further, we show that inhibition of Th2 differentiation using interleukin-4 (IL-4) or IL-13 blockade prevents initiation and progression of lymphedema by decreasing tissue fibrosis and significantly improving lymphatic function, independent of lymphangiogenic growth factors. We show that CD4 inflammation is a critical regulator of tissue fibrosis and lymphatic dysfunction in lymphedema and that inhibition of Th2 differentiation markedly improves lymphatic function independent of lymphangiogenic cytokine expression. Notably, preventing and/or reversing the development of pathological tissue changes that occur in lymphedema may be a viable treatment strategy for this disorder.

CD4+ Cells Regulate Fibrosis and Lymphangiogenesis in Response to Lymphatic Fluid Stasis

IntroductionLymphedema is a chronic disorder that occurs commonly after lymph node removal for cancer treatment and is characterized by swelling, fibrosis, inflammation, and adipose deposition. Although previous histological studies have investigated inflammatory changes that occur in lymphedema, the precise cellular make up of the inflammatory infiltrate remains unknown. It is also unclear if this inflammatory response plays a causal role in the pathology of lymphedema. The purpose of this study was therefore to characterize the inflammatory response to lymphatic stasis and determine if these responses are necessary for the pathological changes that occur in lymphedema.MethodsWe used mouse-tail lymphedema and axillary lymph node dissection (ANLD) models in order to study tissue inflammatory changes. Single cell suspensions were created and analyzed using multi-color flow cytometry to identify individual cell types. We utilized antibody depletion techniques to analyze the causal role of CD4+, CD8+, and CD25+ cells in the regulation of inflammation, fibrosis, adipose deposition, and lymphangiogenesis.ResultsLymphedema in the mouse-tail resulted in a mixed inflammatory cell response with significant increases in T-helper, T-regulatory, neutrophils, macrophages, and dendritic cell populations. Interestingly, we found that ALND resulted in significant increases in T-helper cells suggesting that these adaptive immune responses precede changes in macrophage and dendritic cell infiltration. In support of this we found that depletion of CD4+, but not CD8 or CD25+ cells, significantly decreased tail lymphedema, inflammation, fibrosis, and adipose deposition. In addition, depletion of CD4+ cells significantly increased lymphangiogenesis both in our tail model and also in an inflammatory lymphangiogenesis model.ConclusionsLymphedema and lymphatic stasis result in CD4+ cell inflammation and infiltration of mature T-helper cells. Loss of CD4+ but not CD8+ or CD25+ cell inflammation markedly decreases the pathological changes associated with lymphedema. In addition, CD4+ cells regulate lymphangiogenesis during wound repair and inflammatory lymphangiogenesis.

Intraoperative fluorescence lymphography using indocyanine green in a patient with chylothorax after esophagectomy: report of a case

We report a case of chylothorax treated successfully by a new diagnostic tool: indocyanine green (ICG) fluorescence lymphography. The patient, a 65-year-old man with adenocarcinoma of the esophagogastric junction, underwent radical esophagectomy, which was followed by the development of chylothorax. On postoperative day 10, we performed transabdominal ligation of the thoracic duct. During the re-operation, we injected ICG into the mesentery of the small bowel. We then performed mass ligation of the tissue right and dorsal of the aorta, including the thoracic duct, after which a near-infrared camera system revealed a fluorescent stripe on the caudal part of the ligation. The remnant thoracic duct appeared to be dilated as a result of lymphatic stasis. The patient was discharged 35 days after his initial surgery. We report this case to demonstrate the usefulness of intraoperative ICG lymphography as a tool to identify and confirm ligation of the thoracic duct transabdominally.

Lymphaticovenular Bypass Surgery for Lymphedema Management in Breast Cancer Patients

Historically, the reported incidence of upper extremity lymphedema in breast cancer survivors who have undergone axillary lymph node dissection has ranged from 9% to 41%. In the past 2 decades, sentinel lymph node biopsy has become popular as a way to minimize the morbidity associated with axillary dissection without compromising the cure rate for breast cancer patients. However, even with sentinel node biopsy, the postoperative incidence of upper limb lymphedema in breast cancer patients remains at 4-10%. Lymphedema occasionally emerges immediately after surgery but most often appears after a latent period. Obesity, postoperative seroma, and radiation therapy have been reported as major risk factors for upper extremity lymphedema, but the etiology of lymphedema is still not fully understood. Common symptoms of upper limb lymphedema are increased volume and weight of the affected limb and increased skin tension. The increased volume of the affected limb not only causes physical impairments in wearing clothes and in dexterity but also affects patients' emotional and mental status. Surgical management of lymphedema can be broadly categorized into physiologic methods and reductive techniques. Physiologic methods such as flap interposition, lymph node transfers, and lymphatic bypass procedures aim to decrease lymphedema by restoring lymphatic drainage. In contrast, reductive techniques such as direct excision or liposuction aim to remove fibrofatty tissue generated as a consequence of sustained lymphatic fluid stasis. Currently, microsurgical variations of lymphatic bypass, in which excess lymph trapped within the lymphedematous limb is redirected into other lymphatic basins or into the venous circulation, have gained popularity.

CD4+ inflammation is necessary for pathologic changes associated with sustained lymphatic fluid stasis

Zampell, Jamie Christine MD; Elhadad, Sonia PhD; Avraham, Tomer MD; Yan, Alan MD; Weitman, Evan S. MD; Mehrara, Babak J. MD, FACS Author Information

Phlebolymphedema: Disregarded cause of immunocompromised district

Recurrent lymphangitis, deep trauma, malignancy, and related treatments (ie surgery and radiotherapy) are usually considered the commonest causes of lymphedema. The role of chronic venous disease in this context is often overlooked; yet, all patients with advanced venous disease (stasis dermatitis) have some degree of lymph circulation impairment.1 Venous edema is assumed to be the sole consequence of increased capillary filtration from venous hypertension. Because lymph drainage is the main buffer against the formation of edema, a compensation for the increased lymph load does occur at the beginning. In the long run, however, when the transport capacity is exceeded, the lymphatics fail to keep their buffer function, and interstitial fluid accumulates. This leads to a clinical condition of mixed venous and lymphatic insufficiency that causes a progressive swelling of soft tissues, which is termed phlebolymphedema.2 There is clinical and laboratory evidence confirming the presence of microangiopathy of the lymphatic network in patients with chronic venous disease.3 Further causes of phlebolymphedema are vein stripping (saphenectomy) for varicosities, vein-harvesting procedures for coronary bypass grafting or other vascular surgery, orthopedic surgery, or penetrating trauma involving the medial aspect of a lower limb (Brodell syndrome).4 In all of these conditions, lymph stasis occurs in the involved district as a consequence of the almost inevitable surgical cutting of the lymph collectors

Regulation of Adipogenesis by Lymphatic Fluid Stasis

Although fat deposition is a defining clinical characteristic of lymphedema, the cellular mechanisms that regulate this response remain unknown. The goals of this two-part study were to determine the effect of lymphatic fluid stasis on adipogenesis and inflammation (part I) and how these changes regulate the temporal and spatial expression of fat differentiation genes (part II). Adult female mice underwent tail lymphatic ablation and were euthanized 6 weeks after surgery (n = 20). Fat deposition, fibrosis, and inflammation were then analyzed in the regions of the tail exposed to lymphatic fluid stasis as compared with normal lymphatic flow. Lymphatic fluid stasis in the tail resulted in significant subcutaneous fat deposition, with a 2-fold increase in fat thickness (p < 0.01). In addition, lymphatic stasis was associated with subcutaneous fat fibrosis and collagen deposition. Adipogenesis in response to lymphatic fluid stasis was associated with a marked mononuclear cell inflammatory response (5-fold increase in CD45 cells; p < 0.001). In addition, the authors noted a significant increase in the number of monocytes/macrophages as identified by F4/80 immunohistochemistry (p < 0.001). The mouse-tail model has pathologic findings that are similar to clinical lymphedema, including fat deposition, fibrosis, and inflammation. Adipogenesis in response to lymphatic fluid stasis closely resembles this process in obesity. This model therefore provides an excellent means with which to study the molecular mechanisms that regulate the pathophysiology of lymphedema.

Regulation of Adipogenesis by Lymphatic Fluid Stasis

Although fat deposition is a defining clinical characteristic of lymphedema, the cellular mechanisms that regulate this response remain unknown. The goal of this study was to determine how lymphatic fluid stasis regulates adipogenic gene activation and fat deposition. Adult female mice underwent tail lymphatic ablation and were euthanied at 1, 3, or 6 weeks postoperatively (n = 8 per group). Samples were analyzed by immunohistochemistry and Western blot analysis. An alternative group of mice underwent axillary dissections or sham incisions, and limb tissues were harvested 3 weeks postoperatively (n = 8 per group). Lymphatic fluid stasis resulted in significant subcutaneous fat deposition and fibrosis in lymphedematous tail regions (p < 0.001). Western blot analysis demonstrated that proteins regulating adipose differentiation including CCAAT/enhancer-binding protein-α and adiponectin were markedly up-regulated in response to lymphatic fluid stasis in the tail and axillary models. Expression of these markers increased in edematous tissues according to the gradient of lymphatic stasis distal to the wound. Immunohistochemical analysis further demonstrated that adiponectin and peroxisome proliferator-activated receptor-γ, another critical adipogenic transcription factor, followed similar expression gradients. Finally, adiponectin and peroxisome proliferator-activated receptor-γ expression localized to a variety of cell types in newly formed subcutaneous fat. The mouse-tail model of lymphedema demonstrates pathologic findings similar to clinical lymphedema, including fat deposition and fibrosis. The authors show that lymphatic fluid stasis potently up-regulates the expression of fat differentiation markers both spatially and temporally. These studies elucidate mechanisms regulating abnormal fat deposition in lymphedema pathogenesis and therefore provide a basis for developing targeted treatments.