Nucleoside-modified VEGFC mRNA induces organ-specific lymphatic growth and reverses experimental lymphedema.

Lack or dysfunction of the lymphatics leads to secondary lymphedema formation that seriously reduces the function of the affected organs and results in degradation of quality of life. Currently, there is no definitive treatment option for lymphedema. Here, we utilized nucleoside-modified mRNA encapsulated in lipid nanoparticles (LNPs) encoding murine Vascular Endothelial Growth Factor C (VEGFC) to stimulate lymphatic growth and function and reduce experimental lymphedema in mouse models. We demonstrated that administration of a single low-dose of VEGFC mRNA-LNPs induced durable, organ-specific lymphatic growth and formation of a functional lymphatic network. Importantly, VEGFC mRNA-LNP treatment reversed experimental lymphedema by restoring lymphatic function without inducing any obvious adverse events. Collectively, we present a novel application of the nucleoside-modified mRNA-LNP platform, describe a model for identifying the organ-specific physiological and pathophysiological roles of the lymphatics, and propose an efficient and safe treatment option that may serve as a novel therapeutic tool to reduce lymphedema.

Lymphangiogenic therapy prevents cardiac dysfunction by ameliorating inflammation and hypertension.

The lymphatic vasculature is involved in the pathogenesis of acute cardiac injuries, but little is known about its role in chronic cardiac dysfunction. Here, we demonstrate that angiotensin II infusion induced cardiac inflammation and fibrosis at 1 week and caused cardiac dysfunction and impaired lymphatic transport at 6 weeks in mice, while co-administration of VEGFCc156s improved these parameters. To identify novel mechanisms underlying this protection, RNA sequencing analysis in distinct cell populations revealed that VEGFCc156s specifically modulated angiotensin II-induced inflammatory responses in cardiac and peripheral lymphatic endothelial cells. Furthermore, telemetry studies showed that while angiotensin II increased blood pressure acutely in all animals, VEGFCc156s-treated animals displayed a delayed systemic reduction in blood pressure independent of alterations in angiotensin II-mediated aortic stiffness. Overall, these results demonstrate that VEGFCc156s had a multifaceted therapeutic effect to prevent angiotensin II-induced cardiac dysfunction by improving cardiac lymphatic function, alleviating fibrosis and inflammation, and ameliorating hypertension.

VEGF-C-driven lymphatic drainage enables immunosurveillance of brain tumours.

Immune surveillance against pathogens and tumours in the central nervous system is thought to be limited owing to the lack of lymphatic drainage. However, the characterization of the meningeal lymphatic network has shed light on previously unappreciated ways that an immune response can be elicited to antigens that are expressed in the brain1-3. Despite progress in our understanding of the development and structure of the meningeal lymphatic system, the contribution of this network in evoking a protective antigen-specific immune response in the brain remains unclear. Here, using a mouse model of glioblastoma, we show that the meningeal lymphatic vasculature can be manipulated to mount better immune responses against brain tumours. The immunity that is mediated by CD8 T cells to the glioblastoma antigen is very limited when the tumour is confined to the central nervous system, resulting in uncontrolled tumour growth. However, ectopic expression of vascular endothelial growth factor C (VEGF-C) promotes enhanced priming of CD8 T cells in the draining deep cervical lymph nodes, migration of CD8 T cells into the tumour, rapid clearance of the glioblastoma and a long-lasting antitumour memory response. Furthermore, transfection of an mRNA construct that expresses VEGF-C works synergistically with checkpoint blockade therapy to eradicate existing glioblastoma. These results reveal the capacity of VEGF-C to promote immune surveillance of tumours, and suggest a new therapeutic approach to treat brain tumours.

Functional Nanocomplexes with Vascular Endothelial Growth Factor A/C Isoforms Improve Collateral Circulation and Cardiac Function.

Protein-based therapies are potential treatments for cancer, immunological, and cardiovascular diseases. However, effective delivery systems are needed because of their instability, immunogenicity, and so on. Crosslinked negatively charged heparin polysaccharide nanoparticle (HepNP) is proposed for protein delivery. HepNP can efficiently condense vascular endothelial growth factor (VEGF) because of the unique electronegative sulfonic acid and carboxyl domain of heparin. HepNP is then assembled with VEGF-C (Hep@VEGF-C) or VEGF-A (Hep@VEGF-A) protein for the therapy of myocardial infarction (MI) via intravenous (iv) injection. Hep@VEGF-A-mediated improvement of cardiac function by promoting angiogenesis is limited because of elevated vascular permeability, while Hep@VEGF-C effectively promotes lymphangiogenesis and reduces edema. On this basis, a graded delivery of VEGF-C (0.5-1 h post-MI) and VEGF-A (5 d post-MI) using HepNP is developed. At the dose ratio of 3:1 (Hep@VEGF-C vs Hep@VEGF-A), Hep@VEGF functional complexes substantially reduce the scar formation (≈-39%; p < 0.05) and improve cardiac function (≈+74%; p < 0.05). Such a HepNP delivery system provides a simple and effective therapeutic strategy for cardiovascular diseases by delivering functional proteins. Because of the unique binding ability of heparin with cytokines and growth factors, HepNP also has considerable application prospects in protein therapy for other serious diseases.

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.

VEGF-C attenuates ischemia reperfusion injury of liver graft in rats.

BACKGROUND: Vascular endothelial growth factor receptor-3 (VEGFR-3) / vascular endothelial growth factor -c (VEGF-C) signaling is reported to negatively regulate TLR4-triggered inflammation of macrophages. This study aims to clarify whether the VEGFR-3/VEGF-C signaling can suppress Kupffer cells (KCs) activation and attenuate hepatic ischemia-reperfusion injury (IRI) after liver transplantation. METHODS: A rat model of liver transplantation was performed. Donor livers were perfused with VEGF-C injection via portal vein during cold preservation, and controls were perfused with UW solution. Serum levels of alanine transaminase (ALT), total bilirubin (TBIL) and inflammatory cytokines, as well as histology were analyzed after 24 h. KCs were isolated from grafts, RT-PCR and immunofluorescence were used to evaluate polarization-specific marker genes, western bolt was employed to assess the expression of suppressor of cytokine signaling 1(SOCS1) and phosphorylated glycogen synthase kinase 3ß (p-GSK3ß), and EMSA was utilized to quantify the NF-κB transcriptional activity. RESULTS: Compared with controls, VEGF-C perfusion reduced ALT and TBIL levels and alleviated liver damage. Furthermore, VEGF-C perfusion suppressed serum proinflammatory cytokines secretion and increased IL-10.In addition, the VEGFR-3 mRNA of KCs was increased after reperfusion. VEGF-C perfusion suppressed NF-κB activity and up-regulated the expression of SOCS1 and p-GSK3ß in KCs, and shifted the M1/M2 balance toward an anti-inflammatory profile. CONCLUSION: Exogenous VEGF-C protects liver graft from IRI by regulating the inflammatory response and modifying polarization of KCs.

Alginate hydrogels allow for bioactive and sustained release of VEGF-C and VEGF-D for lymphangiogenic therapeutic applications.

Lymphatic dysfunction is associated with the progression of many cardiovascular disorders due to their role in maintaining tissue fluid homeostasis. Promoting new lymphatic vessels (lymphangiogenesis) is a promising strategy to reverse these cardiovascular disorders via restoring lymphatic function. Vascular endothelial growth factor (VEGF) members VEGF-C and VEGF-D are both potent candidates for stimulating lymphangiogenesis, though maintaining spatial and temporal control of these factors represents a challenge to developing efficient therapeutic lymphangiogenic applications. Injectable alginate hydrogels have been useful for the controlled delivery of many angiogenic factors, including VEGF-A, to stimulate new blood vasculature. However, the utility of these tunable hydrogels for delivering lymphangiogenic factors has never been closely examined. Thus, the objective of this study was to utilize ionically cross-linked alginate hydrogels to deliver VEGF-C and VEGF-D for potential lymphangiogenic applications. We demonstrated that lymphatic endothelial cells (LECs) are sensitive to temporal presentation of VEGF-C and VEGF-D but with different responses between the factors. The greatest LEC mitogenic and sprouting response was observed for constant concentrations of VEGF-C and a high initial concentration that gradually decreased over time for VEGF-D. Additionally, alginate hydrogels provided sustained release of radiolabeled VEGF-C and VEGF-D. Finally, VEGF-C and VEGF-D released from these hydrogels promoted a similar number of LEC sprouts as exogenously added growth factors and new vasculature in vivo via a chick chorioallantoic membrane (CAM) assay. Overall, these findings demonstrate that alginate hydrogels can provide sustained and bioactive release of VEGF-C and VEGF-D which could have applications for therapeutic lymphangiogenesis.

Local induction of lymphangiogenesis with engineered fibrin-binding VEGF-C promotes wound healing by increasing immune cell trafficking and matrix remodeling.

Lymphangiogenesis occurs in inflammation and wound healing, yet its functional roles in these processes are not fully understood. Consequently, clinically relevant strategies for therapeutic lymphangiogenesis remain underdeveloped, particularly using growth factors. To achieve controlled, local capillary lymphangiogenesis with protein engineering and determine its effects on fluid clearance, leukocyte trafficking, and wound healing, we developed a fibrin-binding variant of vascular endothelial growth factor C (FB-VEGF-C) that is slowly released upon demand from infiltrating cells. Using a novel wound healing model, we show that implanted fibrin containing FB-VEGF-C, but not free VEGF-C, could stimulate local lymphangiogenesis in a dose-dependent manner. Importantly, the effects of FB-VEGF-C were restricted to lymphatic capillaries, with no apparent changes to blood vessels and downstream collecting vessels. Leukocyte intravasation and trafficking to lymph nodes were increased in hyperplastic lymphatics, while fluid clearance was maintained at physiological levels. In diabetic wounds, FB-VEGF-C-induced lymphangiogenesis increased extracellular matrix deposition and granulation tissue thickening, indicators of improved wound healing. Together, these results indicate that FB-VEGF-C is a promising strategy for inducing lymphangiogenesis locally, and that such lymphangiogenesis can promote wound healing by enhancing leukocyte trafficking without affecting downstream lymphatic collecting vessels.

Vascular endothelial growth factor-C protects heart from ischemia/reperfusion injury by inhibiting cardiomyocyte apoptosis.

VEGF-C is a newly identified proangiogenic protein playing an important role in vascular disease and angiogenesis. However, its role in myocardial ischemia/reperfusion (I/R) injury remains unknown. The objective of this study was to determine the role and mechanism of VEGF-C in myocardial ischemia-reperfusion injury. Rat left ventricle myocardium was injected with recombinant human VEGF-C protein (0.1 or 1.0 µg/kg b.w.) 1 h prior to myocardial ischemia-reperfusion (I/R) injury. 24 h later, the myocardial infarction size, the number of TUNEL-positive cardiomyocytes, the levels of creatine kinase (CK), CK-MB, cardiac troponin, malondialdehyde (MDA) content, and apoptosis protein Bax expression were decreased, while Bcl2 and pAkt expression were increased in VEGF-C-treated myocardium as compared to the saline-treated I/R hearts. VEGF-C also improved the function of I/R-injured hearts. In the H2O2-induced H9c2 cardiomyocytes, which mimicked the I/R injury in vivo, VEGF-C pre-treatment decreased the LDH release and MDA content, blocked H2O2-induced apoptosis by inhibiting the pro-apoptotic protein Bax expression and its translocation to the mitochondrial membrane, and consequently attenuated H2O2-induced decrease of mitochondrial membrane potential and increase of cytochrome c release from mitochondria. Mechanistically, VEGF-C activated Akt signaling pathway via VEGF receptor 2, leading to a blockade of Bax expression and mitochondrial membrane translocation and thus protected cardiomyocyte from H2O2-induced activation of intrinsic apoptotic pathway. VEGF-C exerts its cardiac protection following I/R injury via its anti-apoptotic effect.

Extracorporeal shock wave therapy combined with vascular endothelial growth factor-C hydrogel for lymphangiogenesis.

BACKGROUND/AIMS: Lymphedema is a clinically incurable disease that occurs commonly after lymph node dissection and/or irradiation. Several studies have recently demonstrated that extracorporeal shock wave therapy (ESWT) could promote lymphangiogenesis associated with expression of vascular endothelial growth factor (VEGF)-C. This research concerned primarily the synergistic effect of ESWT combined with VEGF-C incorporated hydrogel (VEGF-C hydrogel) combination therapy for promoting lymphangiogenesis and ultimately alleviating lymphedema. METHODS: The VEGF-C hydrogel was applied to the injury site in a mouse model of lymphedema and then regularly underwent ESWT (0.05 mJ/mm(2), 500 shots) every 3 days for 4 weeks. RESULTS: Four weeks after the treatment, mice treated with VEGF-C hydrogel and ESWT showed signs of the greatest decrease in edema/collagenous deposits when compared with the other experimental group. LYVE-1-positive vessels also revealed that the VEGF-C/ESWT group had significantly induced the growth of new lymphatic vessels compared to the other groups. Western blot analysis showed that expression of VEGF-C (1.24-fold) and VEGF receptor-3 (1.41-fold) was significantly increased in the VEGF-C/ESWT group compared to the normal group. CONCLUSION: These results suggested that VEGF-C and ESWT had a synergistic effect and were very effective in alleviating the symptoms of lymphedema and promoting lymphangiogenesis.

Lymph node transfer and perinodal lymphatic growth factor treatment for lymphedema.

OBJECTIVE: Our objective was to define the optimal growth factor treatment to be used in combination with lymph node transfer to normalize lymphatic vascular anatomy. BACKGROUND: In the lymph node transfer method, lymphatic anastomoses are expected to form spontaneously. However, lymphangiogenic growth factor therapies have shown promising results in preclinical models of lymphedema. METHODS: The inguinal lymphatic vasculature of pigs was surgically destroyed around the inguinal lymph node. To enhance the regrowth of the lymphatic network in the defected area, adenoviral vascular endothelial growth factor C (VEGF-C) was administered intranodally or perinodally. Control animals received injections of saline or control vector. The lymphangiogenic effect of the growth factor therapy and any potential adverse effects associated with the 2 alternative delivery routes were examined 2 months postoperatively. RESULTS: Both routes of growth factor administration induced robust growth of lymphatic vessels and helped to preserve the structure of the transferred lymph nodes in comparison with the controls. The lymph nodes of the control treated animals regressed in size and their nodal structure was partly replaced by fibro-fatty scar tissue. Intranodally injected adenoviral VEGF-C and adenoviral vector encoding control gene LacZ induced macrophage accumulation inside the node, whereas perinodal administration of VEGF-C did not have this adverse effect. CONCLUSIONS: Lymphangiogenic growth factors improve lymphatic vessel regeneration and lymph node function after lymph node transfer. The perinodal route of delivery provides a basis for future clinical trials in lymphedema patients.

Vascular endothelial growth factor-C derived from CD11b+ cells induces therapeutic improvements in a murine model of hind limb ischemia.

OBJECTIVE: The use of bone marrow cells (BMCs) in therapeutic angiogenesis has been studied extensively. However, the critical paracrine effects of this treatment are still unclear. Therefore, we studied autotransfusable cells that produce vascular endothelial growth factor (VEGF), especially VEGF-C. METHODS: Male C57BL/6 mice with hind limb ischemia were administered intramuscular injections of phosphate-buffered saline as controls, or unsorted BMCs, sorted CD11b(+), or CD11b(-) cells from BMCs, and recombinant VEGF-C. To evaluate the treatments, perfusion was measured by laser Doppler scanning performed on days 0, 1, 3, 7, 14, 21, and 28. A functional assay was performed in parallel, with mice traversing an enclosed walkway. Capillary density was determined by directly counting vessels stained positive with von Willebrand factor at individual time points. Lymphangiogenesis was assessed by LYVE-1 positive cells. RESULTS: Postischemic recovery of hind limb perfusion significantly improved in BMC, CD11b(+), and VEGF-C treatment groups compared with the control groups, as assessed by laser Doppler scanning. On early operative days 1 and 3, the blood flow recovery ratio was higher in the CD11b(+)-treated group compared with BMC and VEGF-C treatment groups. In the functional assay, the VEGF-C group dramatically recovered compared with the control group. The capillary/myofiber ratio in the thigh muscle and number of LYVE-1 positive cells was higher in the CD11b(+) and VEGF-C groups than in controls. Furthermore, expression of VEGF-A, VEGF-C, and VEGF receptor messenger ribonucleic acid and protein was observed in CD11b(+) cells. CONCLUSIONS: The VEGF-C derived from CD11b(+) cells play a critical role in angiogenesis and lymphangiogenesis in a murine model of hind limb ischemia. Consequently, treatment with self-CD11b(+) cells accelerated recovery from ischemia and may be a promising therapeutic strategy for peripheral arterial disease patients.

Microlymphatic surgery for the treatment of iatrogenic lymphedema.

Lymphedema is a chronic and progressive condition that occurs after cancer treatment. Autologous lymph node transplant, or microsurgical vascularized lymph node transfer (ALNT), is a surgical treatment option that brings vascularized vascular endothelial growth factor-C-producing tissue into the operated field to promote lymphangiogenesis and bridge the distal obstructed lymphatic system with the proximal lymphatic system. Operative techniques for upper- and lower-extremity ALNT are described with 3 donor lymph node flaps (inguinal, thoracic, cervical). Surgical technique is described for the combination of ALNT with abdominal flaps and nonabdominal flaps. Imaging showing restoration of lymphatic drainage after ALNT is shown.

Improved regeneration of autologous transplanted lymph node fragments by VEGF-C treatment.

Secondary lymphedema is a common complication after removal of lymph nodes in combination with radiation therapy in the treatment of breast cancer, cervical cancer, and melanomas. Only symptomatic therapies are available at the moment, and lymphedema is for most patients a lifelong condition involving psychological and physical disabilities. Animal models exist to study the pathophysiology of lymphedema but not to study surgical treatments. The aim of this study was to show that regeneration of autologous transplanted lymph node fragments is possible in rats that were irradiated previously locally in the groin and to examine the effects of vascular endothelial growth factor (VEGF)-C injections on the rate of regeneration of transplanted lymph nodes. In all of the animals, inguinal and popliteal lymph nodes and adjacent lymphatic vessels were unilaterally removed and the inguinal region irradiated by a single dose of 15 Gy. Afterward, lymph node fragments were transplanted subcutaneously in the irradiated region. Half of the animals were treated by local VEGF-C injections after transplantation. Four weeks after transplantation, drainage of the leg was tested by injection of blue dye, and the transplanted fragments were removed and examined immunohistologically. We could show that regeneration of autologous transplanted lymph node fragments is possible in areas treated with radiotherapy in the rat. We also documented that transplants can achieve a connection to the lymphatic collectors of the leg. The results suggest that the outcome of regeneration can be improved by injection of VEGF-C in the transplantation area. Thus, lymph node fragment regeneration may be relevant for lymphedema prevention and therapy.

Influence of route of administration and liposomal encapsulation on blood and lymph node exposure to the protein VEGF-C156S.

VEGF-C156S is a recombinant form of human vascular endothelial growth factor C (VEGF-C), which targets the receptor VEGFR-3 present in the lymphatics. VEGF-C156S has lymphangiogenic properties and may represent a potential therapeutic approach in treating the lymphatic disease lymphedema. In the present study, we tested the hypotheses that (1) subcutaneous (s.c.) injection will provide higher lymphatic exposure than intravenous (i.v.) administration of VEGF-C156S and (2) s.c. injection of liposomal (s.c. Lipo) VEGF-C156S will provide greater lymphatic exposure than nonliposomal proteins. The protein VEGF-C156S was radiolabeled with Iodine-125 by a modified chloramine-T method and encapsulated into liposomes. The protein was injected at a dose of 125 µg/kg to mice i.v. or s.c.; the liposomal preparation was administered s.c. (s.c. Lipo). Blood and lymph nodes were collected over 24 h. The mean residence time in lymph nodes after s.c. or s.c. (Lipo) administration was approximately double that following i.v. administration. The area under the concentration-time curve (AUC) ratio of lymph node-blood after s.c. administration of VEGF-C156S was more than double of the AUC ratio after i.v. administration. The results suggest that lymph node exposure of VEGF-C156S was significantly higher after s.c. administration of liposomal or nonliposomal protein as compared with i.v. administration.

Exogenous VEGF-C augments the efficacy of therapeutic lymphangiogenesis induced by allogenic bone marrow stromal cells in a rabbit model of limb secondary lymphedema.

OBJECTIVE: To determine the effect of bone marrow stromal cells transplantation and vascular endothelial growth factor C administration as a treatment for secondary lymphedema. METHODS: Bone marrow stromal cells and/or vascular endothelial growth factor C protein were injected into a rabbit model of limb lymphedema. Water displacement volumetry was performed to measure limb volume changes. Immunohistochemistry was performed to detect VEGFR-3 and to count lymph vessel. Western blot analysis was performed to detect vascular endothelial growth factor C. RESULTS: Before treatment, rabbits had an average volume of edema in the limb of 61.25 ± 5.28, 62.37 ± 4.97, 60.58 ± 7.18 and 61.79 ± 4.33 ml (P = 0.753), respectively, in the BMSC + VEGF-C, bone marrow stromal cell, vascular endothelial growth factor C and control groups. With therapy, this was reduced to an average volume of 7.60 ± 3.02, 12.78 ± 3.41, 31.55 ± 3.51 and 62.33 ± 6.59 ml, respectively, in the four groups 6 months after treatment. Quantitative analysis showed that the vessel numbers were significantly increased in the BMSC + VEGF-C, bone marrow stromal cell and vascular endothelial growth factor C groups compared with the control group at 28 days after the operation (P< 0.05). Western blot analysis demonstrated that expression of vascular endothelial growth factor C was higher in the BMSC + VEGF-C and BMSC groups. CONCLUSIONS: The combined treatment with bone marrow stromal cell transplantation and vascular endothelial growth factor C administration is superior to bone marrow stromal cell transplantation alone in the treatment of limb lymphedema. Bone marrow stromal cell transplantation and vascular endothelial growth factor C administration could enhance the therapeutic effect of each other.

Experimental assessment of pro-lymphangiogenic growth factors in the treatment of post-surgical lymphedema following lymphadenectomy.

INTRODUCTION: Lymphedema is a frequent consequence of lymph node excision during breast cancer surgery. Current treatment options are limited mainly to external compression therapies to limit edema development. We investigated previously, post-surgical lymphedema in a sheep model following the removal of a single lymph node and determined that autologous lymph node transplantation has the potential to reduce or prevent edema development. In this report, we examine the potential of lymphangiogenic therapy to restore lymphatic function and reduce post-surgical lymphedema. METHODS: Lymphangiogenic growth factors (vascular endothelial growth factor-C (VEGF-C) and angiopoitein-2 (ANG-2)) were loaded into a gel-based drug delivery system (HAMC; a blend of hyaluronan and methylcellulose). Drug release rates and lymphangiogenic signaling in target endothelial cells were assessed in vitro and vascular permeability biocompatibility tests were examined in vivo. Following, the removal of a single popliteal lymph node, HAMC with the growth factors was injected into the excision site. Six weeks later, lymphatic functionality was assessed by injecting (125)Iodoine radiolabelled bovine serum albumin ((125)I-BSA) into prenodal vessels and measuring its recovery in plasma. Circumferential leg measurements were plotted over time and areas under the curves used to quantify edema formation. RESULTS: The growth factors were released over a two-week period in vitro by diffusion from HAMC, with 50% being released in the first 24 hours. The system induced lymphangiogenic signaling in target endothelial cells, while inducing only a minimal inflammatory response in sheep. Removal of the node significantly reduced lymphatic functionality (Nodectomy 1.9 ± 0.9, HAMC alone 1.7 ± 0.8) compared with intact groups (3.2 ± 0.7). There was no significant difference between the growth factor treatment group (2.3 ± 0.73) and the intact group. An increase in the number of regenerated lymphatic vessels at treatment sites was observed with fluoroscopy. Groups receiving HAMC plus growth factors displayed significantly reduced edema (107.4 ± 51.3) compared with non-treated groups (nodectomy 219.8 ± 118.7, and HAMC alone 162.6 ± 141). CONCLUSIONS: Growth factor therapy has the potential to increase lymphatic function and reduce edema magnitude in an animal model of lymphedema. The application of this concept to lymphedema patients warrants further examination.

Therapeutic responses to exogenous VEGF-C administration in experimental lymphedema: immunohistochemical and molecular characterization.

BACKGROUND: In a widely employed murine tail model of human acquired lymphedema, we have previously observed that, distal to the site of experimental lymphatic ablation, there is immunohistochemical evidence of a profound increase in cutaneous lymphatic vessel number and size that normalizes after VEGF-C administration. OBJECTIVE: In order to investigate the mechanistic basis of the lymphatic microvascular remodeling, we have studied the lymphedematous responses to VEGF-C after co-administration of systemic VEGFR-3 neutralizing antibody. We have also undertaken genome-wide whole-tissue transcriptional profiling of lymphedematous tissues before and after exogenous VEGF-C administration. STUDY DESIGN: We provoked postsurgical lymphedema in the mouse tail model and assessed the effects of exogenously administered human recombinant VEGF-C in the presence of a monoclonal anti-VEGFR-3 antibody. Polyclonal IgG was administered to a series of control subjects. Microvascular lymphatic remodeling was assessed through quantitative and qualitative anti-LYVE1 immunohistochemistry. Genome-wide transcriptional profiling was performed in whole skin derived from lymphedema with and without exogenous VEGF-C administration. Normal mice and surgical shams served as controls. RESULTS: In the presence of the monoclonal anti-VEGFR-3 neutralizing antibody, positive lymphatic microvascular remodeling in lymphedematous skin is nearly completely abrogated. Furthermore, the therapeutic impact of added VEGF-C is markedly attenuated, as is the ability of the growth factor to ameliorate tissue edema. Transcriptional profiling of the VEGF-C responses in treated lymphedema reveals a very restricted list of genes whose expression is upregulated in lymphedema and re-normalized following VEGF-C treatment. CONCLUSION: The postsurgical murine tail model of lymphedema closely simulates attributes of human lymphedema. The current series of investigations underscores the utility of the murine tail model to the preclinical and translational investigation of lymphedema. The derived insights continue to focus favorably upon the central role of the VEGFR-3 receptor and its ligands in the development and therapeutic resolution of lymphedema. Whole tissue transcriptional profiling continues to shed light on disease mechanisms and potential future targets for therapeutic intervention.

Vascular endothelial growth factor-C stimulates the lymphatic pump by a VEGF receptor-3-dependent mechanism.

Vascular endothelial growth factor (VEGF)-C plays an important role in lymphangiogenesis; however, functional responses of lymphatic vessels to VEGF-C have not been characterized. We tested the hypothesis that VEGF-C-induced activation of VEGF receptor (VEGFR)-3 increases lymphatic pump output. We examined the in vivo pump activity of rat mesenteric collecting lymphatics using intravital microscopy during basal conditions and during treatment with 1 nM recombinant VEGF-C, the selective VEGFR-3 agonist VEGF-Cys(156)Ser mutation (C156S; 1 nM), or 0.1 nM VEGF-A. Their specific responses were also analyzed during selective inhibition of VEGFR-3 with MAZ-51. Contraction frequency, end-diastolic diameter, end-systolic diameter, stroke volume index, pump flow index, and ejection fraction were evaluated. We also assessed arteriolar diameter and microvascular extravasation of FITC-albumin. The results show that both VEGF-C and VEGF-C156S significantly increased contraction frequency, end-diastolic diameter, stroke volume index, and pump flow index in a time-dependent manner. VEGF-A caused a different response characterized by a significantly increased stroke volume after 30 min of treatment. MAZ-51 (5 muM) caused tonic constriction and decreased contraction frequency. In addition, 0.5 and 5 muM MAZ-51 attenuated VEGF-C- and VEGF-C156S-induced lymphatic pump activation. VEGF-A caused vasodilation of arterioles, whereas VEGF-C and VEGF-C156S did not significantly alter arteriolar diameter. Also, VEGF-A and VEGF-C caused increased microvascular permeability, whereas VEGF-C156S did not. Our results demonstrate that VEGF-C increases lymphatic pumping through VEGFR-3. Furthermore, changes in microvascular hemodynamics are not required for VEGFR-3-mediated changes in lymphatic pump activity.

Regulation of lymphatic capillary regeneration by interstitial flow in skin.

Decreased interstitial flow (IF) in secondary lymphedema is coincident with poor physiological lymphatic regeneration. However, both the existence and direction of causality between IF and lymphangiogenesis remain unclear. This is primarily because the role of IF and its importance relative to the action of the prolymphangiogenic growth factor vascular endothelial growth factor (VEGF)-C (which signals primarily through its receptor VEGFR-3) are poorly understood. To clarify this, we explored the cooperative roles of VEGFR-3 and IF in a mouse model of lymphangiogenesis in regenerating skin. Specifically, a region of lymphangiogenesis was created by substituting a portion of mouse tail skin with a collagen gel within which lymphatic capillaries completely regenerate over a period of 60 days. The relative importance of IF and VEGF-C signaling were evaluated by either inhibiting VEGFR-3 signaling with antagonistic antibodies or by reducing IF. In some cases, VEGF-C signaling was then increased with exogenous protein. To clarify the role of IF, the distribution of endogenous matrix metalloproteinases (MMPs) and VEGF-C within the regenerating region was determined. It was found that inhibition of either VEGFR-3 or IF suppressed endogenous lymphangiogenesis. Reduction of IF was found to decrease lymphatic migration and transport of endogenous MMP and VEGF-C through the regenerating region. Therapeutic VEGF-C administration restored lymphangiogenesis following inhibition of VEGFR-3 but did not increase lymphangiogenesis following inhibition of IF. These results identify IF as an important regulator of the pro-lymphangiogenic action of VEGF-C.