Multiple mouse models of primary lymphedema exhibit distinct defects in lymphovenous valve development.
ABSTRACT: Lymph is returned to the blood circulation exclusively via four lymphovenous valves (LVVs). Despite their vital importance, the architecture and development of LVVs is poorly understood. We analyzed the formation of LVVs at the molecular and ultrastructural levels during mouse embryogenesis and identified three critical steps. First, LVV-forming endothelial cells (LVV-ECs) differentiate from PROX1(+) progenitors and delaminate from the luminal side of the veins. Second, LVV-ECs aggregate, align perpendicular to the direction of lymph flow and establish lympho-venous connections. Finally, LVVs mature with the recruitment of mural cells. LVV morphogenesis is disrupted in four different mouse models of primary lymphedema and the severity of LVV defects correlate with that of lymphedema. In summary, we have provided the first and the most comprehensive analysis of LVV development. Furthermore, our work suggests that aberrant LVVs contribute to lymphedema.
Project description:Lymphatic vasculature is an integral part of digestive, immune and circulatory systems. The homeobox transcription factor PROX1 is necessary for the development of lymphatic vessels, lymphatic valves (LVs) and lymphovenous valves (LVVs). We and others previously reported a feedback loop between PROX1 and vascular endothelial growth factor-C (VEGF-C) signaling. PROX1 promotes the expression of the VEGF-C receptor VEGFR3 in lymphatic endothelial cells (LECs). In turn, VEGF-C signaling maintains PROX1 expression in LECs. However, the mechanisms of PROX1/VEGF-C feedback loop remain poorly understood. Whether VEGF-C signaling is necessary for LV and LVV development is also unknown. Here, we report for the first time that VEGF-C signaling is necessary for valve morphogenesis. We have also discovered that the transcriptional co-activators YAP and TAZ are required to maintain PROX1 expression in LVs and LVVs in response to VEGF-C signaling. Deletion of <i>Yap</i> and <i>Taz</i> in the lymphatic vasculature of mouse embryos did not affect the formation of LVs or LVVs, but resulted in the degeneration of these structures. Our results have identified VEGF-C, YAP and TAZ as a crucial molecular pathway in valve development.
Project description:Although patients with obesity-induced lymphedema can be treated by weight loss therapy, they find it difficult to lose the required amount of weight. The aims of this study were to clarify the characteristics of the lymphatic vessels in patients with obesity-induced lymphedema and to determine the feasibility and efficacy of lymphovenous anastomosis (LVA) in these patients. Methods:Twenty-two patients (44 edematous lower limbs) with a body mass index (BMI) >35 kg/m2 (obese group) and 91 patients with lymphedema (141 edematous lower limbs) and BMI <25 kg/m2 were enrolled as a control group (nonobese group) and underwent LVA. The diameter and depth of lymphatics and the effect of LVA were compared. Results:Lymphatics were detectable within 10-mm depth in the nonobese group and the obese group (3.0 ± 1.4 mm versus 3.5 ± 2.1 mm; P < 0.01). The lymphatic diameter was significantly greater in the obese group than in the nonobese group (0.79 ± 0.30 mm versus 0.54 ± 0.22 mm; P < 0.01). There was no significant difference in the rate of improvement in lymphedema after LVA between the nonobese group (9.1% ± 9.2%) and the obese group (8.9% ± 7.3%; P = 0.84). There was no correlation between the improvement rate of lymphedema and that of BMI in the obese group (P = 0.57). Conclusions:LVA is a feasible procedure even in morbidly obese patients. Considering that substantial weight loss is a difficult and time-consuming task for patients, LVA combined with not gaining weight is a good option for these patients.
Project description:INTRODUCTION:Analysis of quality of life (QOL) outcomes is an important aspect of lymphedema treatment since this disease can substantially impact QOL in affected individuals. There are a growing number of studies reporting patient-reported outcomes (PROMs) for patients with lymphedema. The purpose of this study was to conduct a systematic review of outcomes and utilization of PROMs following surgical treatment of lymphedema. METHODS:A literature search of four databases was performed up to and including March, 2019. Studies included reported on QOL outcomes after physiologic procedures, defined as either lymphovenous bypass (LVB) or vascularized lymph node transplant (VLNT), to treat upper and/or lower extremity primary or secondary lymphedema. RESULTS:In total, 850 studies were screened-of which, 32 studies were included in this review. Lymphovenous bypass was the surgical intervention in 16 studies, VLNT in 11 studies, and both in 5 studies. Of the 32 total studies, 16 used validated survey tools. The most commonly used PROM was the lymph quality of life measure for limb lymphedema (LYMQOL) (12 studies). In the remaining four studies, the upper limb lymphedema 27 scale (ULL27), the short form 36 questionnaire (SF-36), the lymphedema functioning, disability and health questionnaire (Lymph-ICF), and lymphedema life impact scale (LLIS) were each used once. QOL improvement following surgical treatment was noted in all studies. CONCLUSIONS:Physiologic surgical treatment of lymphedema results in improved QOL outcomes in most patients. The use of validated PROM tools is increasing but there is no current consensus on use. Future research to evaluate the psychometric properties of PROMs in lymphedema is needed to guide the development and use of lymphedema-specific tools.
Project description:Lymphedema, the most common lymphatic anomaly, involves defective lymphatic valve development; yet the epigenetic modifiers underlying lymphatic valve morphogenesis remain elusive. Here, we showed that during mouse development, the histone-modifying enzyme histone deacetylase 3 (Hdac3) regulates the formation of both lymphovenous valves, which maintain the separation of the blood and lymphatic vascular systems, and the lymphatic valves. Endothelium-specific ablation of Hdac3 in mice led to blood-filled lymphatic vessels, edema, defective lymphovenous valve morphogenesis, improper lymphatic drainage, defective lymphatic valve maturation, and complete lethality. Hdac3-deficient lymphovenous valves and lymphatic vessels exhibited reduced expression of the transcription factor Gata2 and its target genes. In response to oscillatory shear stress, the transcription factors Tal1, Gata2, and Ets1/2 physically interacted with and recruited Hdac3 to the evolutionarily conserved E-box-GATA-ETS composite element of a Gata2 intragenic enhancer. In turn, Hdac3 recruited histone acetyltransferase Ep300 to form an enhanceosome complex that promoted Gata2 expression. Together, these results identify Hdac3 as a key epigenetic modifier that maintains blood-lymph separation and integrates both extrinsic forces and intrinsic cues to regulate lymphatic valve development.
Project description:Lymphedema may be characterized by a progressive clinical course and limitations in improvement despite multi-modality treatment. In westernized countries, it most commonly presents as an undesirable complication of cancer treatment, particularly breast cancer. In the past several decades, surgical treatments for lymphedema have advanced, alongside developments in microsurgery. Lymphovenous anastomosis (LVA) and lymph node transplantation are physiological therapies that may reduce lymphedema through addressing its route cause. Ablative techniques such as liposuction and subcutaneous excision aid in resolving the accumulation of proteinaceous adipose and fibrotic tissue seen in advanced lymphedema. The goal of this review is to examine the outcomes and limitations of current surgical techniques used in lymphedema management.
Project description:Breast cancer-related lymphedema is a long-term condition that affects almost half of breast cancer survivors. Clinical studies have looked at the benefits of lymphaticovenular anastomosis (LVA) for the treatment of upper extremities lymphedema after breast cancer, however, there is still controversy if it improves lymphedema. This study aimed to analyze the studies and outcomes related to LVA for breast cancer-related lymphedema. A PubMed/Medline search was performed using "lymphovenous bypass", "upper extremity lymphedema", "arm lymphedema after breast cancer treatment", and "lymphaticovenular anastomosis" as key words. Only English articles reporting outcomes after LVA were included. We found 22 articles that met the inclusion criteria. Positive outcomes were found in 21 studies with an objective volume reduction and subjective symptoms relief after LVA. This literature review concluded that LVA has demonstrated a significant decrease in upper extremity volumes and an improvement in subjectively reporting symptoms in breast cancer-related lymphedema patients.
Project description:Human ex vivo gene therapy protocols have been used successfully to treat a variety of genetic disorders, infectious diseases, and cancer. Murine oncoretroviruses (specifically, gammaretroviruses) have served as the primary gene delivery vehicles for these trials. However, in some cases, such vectors have been associated with insertional mutagenesis. As a result, alternative vector platforms such as lentiviral vectors (LVVs) are being developed. LVVs may provide advantages compared with gammaretroviral vectors, including the ability to transduce large numbers of nondividing cells, resistance to gene silencing, and a potentially safer integration profile. The aim of this study was to develop a simplified process for the rapid production of clinical-grade LVVs. To that end, we used a self-inactivating bicistronic LVV encoding an MART (melanoma antigen recognized by T cells)-1-reactive T cell receptor containing oPRE, an optimized and truncated version of woodchuck hepatitis virus posttranslational regulatory element (wPRE). Using our simplified clinical production process, 293T cells were transiently transfected in roller bottles. The LVV supernatant was collected, treated with Benzonase, and clarified by modified step filtration. LVV produced in this manner exhibited titers and a biosafety profile similar to those of cGMP (current Good Manufacturing Practices) LVVs previously manufactured at the Indiana University Vector Production Facility in support of a phase I/II clinical trial. We describe a simple, efficient, and low-cost method for the production of clinical-grade LVV for ex vivo gene therapy protocols.
Project description:The management of lymphatic malformations (LMs) is challenging, particularly for large and complex lesions involving anatomical structures in the adjacent tissue. While lymphovenous anastomosis (LVA) has been reported as an effective treatment for lymphedema, it has hardly been described as a treatment for LM. Virtual reality has the ability to visualize human structures in three dimensions and can be used for the preoperative planning of complex cases. Here, we describe the first case of the management of an LM by LVA preoperatively planned with virtual reality. A young woman presented with an LM previously treated by gross excision. Following persistent complaints of swelling, a minimally invasive microsurgical intervention was planned. The results of the single photon emission tomography with computed tomography (SPECT-CT) and lymphoscintigraphy were analyzed using a virtual reality program, and a 3D patient-specific model was constructed. Based on the combined findings of this 3D model and lymphography with a fluorescent marker, a precise skin incision could be determined and one lymph vessel was anastomosed to a nearby vein. The swelling of the thigh reduced and the discomfort disappeared. Although more reports are needed to confirm its efficacy, LVA planned with virtual reality constructed images appears to be a valuable treatment option for complex lesions, including LMs.
Project description:Background ?Lymphedema is an accumulation of protein-rich fluid in the interstitial spaces resulting from impairment in the lymphatic circulation that can impair quality of life and cause considerable morbidity. Lower extremity lymphedema (LEL) has an overall incidence rate of 20%. Conservative therapies are the first step in treatment of LEL; however, they do not provide a cure because they fail to address the underlying physiologic dysfunction of the lymphatic system. Among several surgical alternatives, lymphaticovenous anastomosis (LVA) has gained popularity due to its improved outcomes and less invasive approach. This study aims to review the published literature on LVA for LEL treatment and to analyze the surgical outcomes. Methods ?PubMed database was used to perform a comprehensive literature review of all articles describing LVA for treatment of LEL from Novemeber 1985 to June 2019. Search terms included "lymphovenous" OR "lymphaticovenous" AND "bypass" OR "anastomosis" OR "shunt" AND "lower extremity lymphedema." Results ?A total of 95 articles were identified in the initial query, out of which 58 individual articles were deemed eligible. The studies included in this review describe notable variations in surgical techniques, number of anastomoses, and supplementary interventions. All, except one study, reported positive outcomes based on limb circumference and volume changes or subjective clinical improvement. The largest reduction rate in limb circumference and volume was 63.8%. Conclusion ?LVA demonstrated a considerable reduction in limb volume and improvement in subjective findings of lymphedema in the majority of patients. The maintained effectiveness of this treatment modality in long-term follow-up suggests great efficacy of LVA in LEL treatment.
Project description:PURPOSE:The purpose of the study was to determine when the risk of lymphedema is highest after treatment of breast cancer and which factors influence the time course of lymphedema development. METHODS AND MATERIALS:Between 2005 and 2017, 2171 women (with 2266 at-risk arms) who received surgery for unilateral or bilateral breast cancer at our institution were enrolled. Perometry was used to objectively assess limb volume preoperatively, and lymphedema was defined as a ?10% relative arm-volume increase arising >3 months postoperatively. Multivariable regression was used to uncover risk factors associated with lymphedema, the Cox proportional hazards model was used to calculate lymphedema incidence, and the semiannual hazard rate of lymphedema was calculated. RESULTS:With a median follow-up of 4 years, the overall estimated 5-year cumulative incidence of lymphedema was 13.7%. Significant factors associated with lymphedema on multivariable analysis were high preoperative body mass index, axillary lymph node dissection (ALND), and regional lymph node radiation (RLNR). Patients receiving ALND with RLNR experienced the highest 5-year rate of lymphedema (31.2%), followed by those receiving ALND without RLNR (24.6%) and sentinel lymph node biopsy with RLNR (12.2%). Overall, the risk of lymphedema peaked between 12 and 30 months postoperatively; however, the time course varied as a function of therapy received. Early-onset lymphedema (<12 months postoperatively) was associated with ALND (HR [hazard ratio], 4.75; P < .0001) but not with RLNR (HR, 1.21; P = .55). In contrast, late-onset lymphedema (>12 months postoperatively) was associated with RLNR (HR, 3.86; P = .0001) and, to a lesser extent, ALND (HR, 1.86; P = .029). The lymphedema risk peaked between 6 and 12 months in the ALND-without-RLNR group, between 18 and 24 months in the ALND-with-RLNR group, and between 36 and 48 months in the group receiving sentinel lymph node biopsy with RLNR. CONCLUSIONS:The time course for lymphedema development depends on the breast cancer treatment received. ALND is associated with early-onset lymphedema, and RLNR is associated with late-onset lymphedema. These results can influence clinical practice to guide lymphedema surveillance strategies and patient education.