Intraocular pressure-related side-effects after endothelial keratoplasty.

PURPOSE: To investigate circumpapillary retinal nerve fibre layer (RNFL) thickness, pupillary function and diameter after phacoemulsification and lens implantation alone or combined with endothelial keratoplasty (EK). METHODS: This study was a secondary analysis of data from a randomized, single-masked trial, that included 72 patients with Fuchs' endothelial dystrophy and cataract, equally allocated (1:1) to ultrathin Descemet's stripping automated endothelial keratoplasty or Descemet's membrane endothelial keratoplasty. The cataract extraction (CE) group included 40 patients undergoing cataract surgery only. All patients were treated with phacoemulsification and lens implantation. RESULTS: RNFL thickness was significantly lower in the CE group than after EK for the global (p < 0.01), nasal (p = 0.04), and temporal sectors (p = 0.01) 12 months after surgery. RNFL thickness was comparable between patients treated with rebubbling and others (p ≥ 0.16 for all comparisons) after 12 months. The CE group and patients treated with EK demonstrated a comparable scotopic (p = 0.34) and photopic pupil diameter (p = 0.95) as well as a comparable maximum (p = 0.83) and average pupillary constriction velocity (p = 0.95) after 12 months. In contrast, patients treated with rebubbling had a significantly smaller scotopic pupil diameter (p = 0.04). CONCLUSION: In this study, no evidence was found indicating a negative impact on the RNFL thickness after EK when compared to CE 12 months after surgery. Iris function and pupil diameter were comparable between the CE group and patients treated with EK after 12 months.

Local Adenoviral Delivery of Vascular Endothelial Growth Factor C Induces Lymphangiogenesis in the Conjunctiva in Rabbits.

INTRODUCTION: The purpose of this study was to determine if conjunctival lymphangiogenesis can be induced using adenoviral delivery of vascular endothelial growth factor C (VEGF-C). METHODS: Seventeen New Zealand white rabbits received a subconjunctival injection containing 3.5 × 107 plaque-forming units of an adenoviral vector containing the gene-encoding VEGF-C (Ad-VEGF-C). The contralateral eye was used for control experiment (the same volume of either saline or an empty vector). After 2 weeks, the animals were examined with trypan blue conjunctival lymphangiography, and the eyes were harvested for histology and immunohistochemistry (podoplanin and CD31). RESULTS: Trypan blue conjunctival lymphangiography revealed significantly more extensive conjunctival vessel network in the Ad-VEGF-C group compared with control: 1.35 ± 0.67 versus 0.28 ± 0.17 vessel length/analysed area (p = <0.0001). This finding was confirmed with immunohistochemistry, where a significant increase in the number of lymphatic vessels was found compared to control; 34 ± 9 per mm2 versus 13 ± 8 per mm2 (p = 0.0019). Furthermore, there was a significant increase in lymphatic cross-sectional area; 32,500 ± 7,900 µm2 per mm2 versus 17,600 ± 9,700 µm2 per mm2 (p = 0.0149). Quantification of blood vessels revealed no significant difference in blood vessel density between Ad-VEGF-C and control; 19 ± 9 per mm2 versus 14 ± 8 per mm2 (p = 0.1971). There was no significant difference in total blood vessel area; 13,200 ± 7,600 µm2 per mm2 versus 7,100 ± 3,000 µm2 per mm2 (p = 0.0715). Eyes treated with an adenoviral vector (VEGF-C or empty vector) responded with a reactive cellular response, predominantly lymphocytes, towards the vector. CONCLUSION: The study demonstrates the feasibility of inducing conjunctival lymphangiogenesis with a single subconjunctival injection of Ad-VEGF-C. Future studies will explore how this can be used with a therapeutic purpose.

Topical dilation as first-line treatment for fibrin membrane pupillary-block glaucoma following uncomplicated cataract surgery.

Fibrin membrane pupillary-block glaucoma is an uncommon complication after phacoemulsification cataract surgery. We present a case treated successfully by pharmacological dilation of the pupil. Previous case reports have recommended the use of Nd:YAG peripheral iridotomy, Nd:YAG membranotomy and intracameral tissue plasminogen activator.The patient presented with intraocular pressure (IOP) of 45 mmHg 2 days after uneventful phacoemulsification cataract surgery. Anterior segment optical coherence tomography revealed that a fibrinous membrane-filled space had formed between the pupillary plane and the implanted intraocular lens.The diagnosis of fibrin membrane pupillary-block glaucoma was made. Initial treatment consisted of IOP-lowering medication and topical pupillary dilation (atropine 1%, phenylephrine hydrochloride 10% and tropicamide 1%). Within 30 min, the dilation broke the pupillary block and the IOP was 15 mmHg. The inflammation was treated with topical dexamethasone, nepafenac and tobramycin. Within a month, the patient reached a visual acuity of 1.0.

[Primary angle closure].

Glaucoma is the most common cause of irreversible blindness globally with a significant contribution from angle-closure glaucoma. Over the past 20 years, the terminology has been standardised with the term glaucoma being used exclusively for patients with signs of glaucomatous damage to the optic nerve. Prospective randomised clinical trials have changed treatment algorithms as summarised in this review. Prophylactic iridotomy is now only offered to selected at-risk patients, while removal of the lens with phacoemulsification is more often used as the primary treatment of patients with angle closure.

Function of Upper Extremity Human Lymphatics Assessed by Near-Infrared Fluorescence Imaging.

Background: Knowledge of functional parameters that can be used for evaluation of upper extremity lymphatic function is limited. This study aims to evaluate near-infrared fluorescence (NIRF) imaging for evaluation of lymphatic function in the human arm. Methods and Results: Ten healthy male volunteers (age 25.7 ± 1.3 years) were included and examined at two occasions. The lymphatic functional frequency and velocity were examined at baseline, during hyperthermia and after exercise. In addition, the maximum pressure generated by contraction of the lymphatic vessels was estimated. The mean contraction frequency was found to be 0.9 ± 0.4/min, and the mean velocity of the propulsions was 1.1 ± 0.3 cm/s. The average maximal pressure generated by the contraction of the lymphatic vessels was 59 ± 12 mmHg. No significant difference in frequency, velocity, or pumping pressure was found between the two visits (p > 0.05). Local hyperthermia increased contraction frequency significantly, whereas exercise decreased frequency and increased propulsion velocity. Conclusions: The functional lymphatic parameters evaluated by NIRF imaging showed good repeatability with no significant difference between visits. Future examinations should be conducted with standardization of temperature and exercise, as these parameters were shown to alter lymphatic function.

Reduced Lymphatic Function Predisposes to Calcium Channel Blocker Edema: A Randomized Placebo-Controlled Clinical Trial.

Background: The current belief is that the calcium channel blocker (CCB)-induced edema is due to a preferential arterial over venous dilatation leading to increased fluid filtration. We challenged this conviction by measuring the lymphatic removal of interstitial fluid during chronic systemic treatment with the CCB, amlodipine. Lymphatic vessels could potentially be an off-target effect of the drugs and play a role in CCB edema. Methods and Results: Sixteen healthy postmenopausal women completed a 12-week double-blinded randomized placebo-controlled crossover trial. Lymphatic function was assessed by near-infrared fluorescence imaging. The lymphatic function during amlodipine treatment compared with placebo did not show any difference in pumping pressure (53.9 ± 13.9 mmHg vs. 54.7 ± 9.4 mmHg, p = 0.829), contraction frequency (0.4 ± 0.2/min vs. 0.4 ± 0.3/min, p = 0.932), refill time (440 ± 438 seconds vs. 442 ± 419 seconds, p = 0.990), or propagation velocity of lymph packets (18 ± 10 mm/s vs. 15 ± 7 mm/s, p = 0.124). However, the subjects who developed edema during CCB treatment had a 20% lower baseline lymphatic pumping pressure (48.9 ± 4.4 mmHg, n = 7) than the subjects not affected by treatment (59.1 ± 1.2 mmHg, n = 9, p = 0.025). Contraction frequency, refill time, and lymph packet velocity showed no differences in baseline values between the two groups. Conclusion: Our results suggest that CCB does not directly impair lymphatic function. However, our results show that a reduced lymphatic function predisposes to CCB edema, which may explain why some patients develop edema during treatment.

Göttingen Minipig is not a Suitable Animal Model for in Vivo Testing of Tissue-Engineered Corneal Endothelial Cell-Carrier Sheets and for Endothelial Keratoplasty.

AIM: To test the feasibility of implanting human anterior lens capsules (HALCs) with porcine corneal endothelial cells (pCEC) in vivo in Göttingen minipigs and at the same time test the suitability of Göttingen minipig as model for endothelial keratoplasty. MATERIALS AND METHODS: Cell-carrier constructs of decellularized HALC with cultured (pCEC) were created for implementation in vivo. Eight Göttingen minipigs (6 months old) underwent surgery with descemetorhexis or removal of endothelium by scraping and implementation of HALC without (animal 1-4) and with (animal 5-8) pCEC. Follow-up examinations included optical coherence tomography (OCT) imaging (1,2 and 3 months) and slit-lamp examination (<1 week as well as 1,2 and 3 months). RESULTS: Intraoperative challenges included difficulties in maintaining an anterior chamber due to soft tissue and vitreous pressure, development of corneal edema and difficulties removing Descemet's membrane because of strong adhesion to stroma. Therefore, descemetorhexis was replaced by mechanical scraping of the endothelium in animal 4-8. HALCs without pCEC were implanted in animal 1-4. Apposition to the back surface was not achieved in animal 1 and 3 because of corneal edema and poor visibility. Animal 5 was sacrificed because of a lens capsule tear. HALCs with pCEC were implanted in animal 6-8. Slit-lamp examination the first week revealed corneal edema in all animals, although mild in animals 4. One-month examination showed retrocorneal membranes with overlying corneal edema in all animals. Histology showed fibrosis in the AC and on the back surface of the cornea, compatible with the clinical diagnosis of retrocorneal membrane. CONCLUSIONS: In conclusion, the minipig is not suitable for corneal transplantation studies in vivo because of intraoperative challenges and development of retrocorneal membrane postoperatively. For in vivo testing of the surgical handling and the therapeutic potential of tissue-engineered endothelial cell-carrier constructs other animal models are required.

Role of the lymphatic vasculature in cardiovascular medicine.

The lymphatic vasculature has traditionally been considered important for removal of excessive fluid from the interstitial space, absorption of fat from the intestine and the immune system. Advances in molecular medicine and imaging have provided us with new tools to study the lymphatics. This has revealed that the vessels are actively involved in regulation of immune cell trafficking and inflammation. We now know much about how new lymphatic vessels are created (lymphangiogenesis) and that this is important in, for example, wound healing and tissue repair. The best characterised pathway for lymphangiogenesis is the vascular endothelial growth factor C (VEGF-C)/VEGFR3 pathway. Over recent years, there has been an increasing interest in the role of the lymphatics in cardiovascular medicine. Preclinical studies have shown that lymphangiogenesis and immune cell trafficking play a role in cardiovascular conditions such as atherosclerosis, recovery after myocardial infarction and rejection of cardiac allografts. Targeting the VEGF-C/VEGFR3 pathway can be beneficial in these conditions. The clinical spectrum of lymphatic abnormalities and lymphoedema is wide and overlaps with congenital heart disease. Important long-term complications to the Fontan circulation involves the lymphatics. New and improved imaging modalities has improved our understanding and management of these patients. Lymphatic leaks and flow abnormalities can be successfully treated, minimally invasively, with percutaneous embolisation. Future research will prove if the preclinical findings that point to a role of the lymphatics in several cardiovascular conditions will result in new treatment options.

Scheimpflug Imaging of the Danish Cohort of Patients With Wilson Disease.

PURPOSE: The purpose of this study was to investigate the use of anterior segment imaging in diagnosing Kayser-Fleischer rings in patients with Wilson disease. METHODS: In a tertiary center for Wilson disease, patients were examined with a Pentacam HR Scheimpflug-based tomography device in addition to conventional slit-lamp examination. The inferior part of the cornea was analyzed using both a built-in densitometry module and ImageJ. RESULTS: Thirty-one patients with Wilson disease (78% of all Danish patients) were included, resulting in 83 examinations over a 5-year period. Ten had a manifest Kayser-Fleischer ring in the inferior part of the cornea on at least 1 examination, 5 had other causes of peripheral corneal scatter, and 16 had normal examinations. The built-in densitometry module performed poorly in discriminating between the presence and absence of a Kayser-Fleischer ring. However, analysis of the images in ImageJ and calculation of a normalized signal (peak posterior value/peak anterior value) with a cutoff value set to 1 detected 28 of 31 Kayser-Fleischer rings and resulted in 96% sensitivity and 95% specificity. In 12 patients who underwent 3 or more examinations during the period, changes in the normalized signal seemed to reflect the efficiency of the treatment, although more studies are needed for this conclusion. CONCLUSIONS: ImageJ-based analysis of Pentacam images has a high sensitivity in detecting Kayser-Fleischer rings and can be used as a diagnostic procedure for Wilson disease and may be a tool to monitor the disease in an objective manner.

Morphology and Function of the Lymphatic Vasculature in Patients With a Fontan Circulation.

BACKGROUND: The Fontan procedure has revolutionized the treatment of univentricular hearts. However, it is associated with severe complications such as protein-losing enteropathy, plastic bronchitis, and peripheral edema that may involve the lymphatic circulation. We aimed to assess lymphatic function and morphology in patients with a univentricular circulation. METHODS: The functional state of lymphatic vessels in the lower extremities of patients with a Fontan circulation (n=10) was investigated using the novel technique near-infrared fluorescence imaging and compared with an age-, sex-, and weight-matched control group of healthy volunteers (n=10). The lymphatic morphology was described using T2-weighted magnetic resonance imaging, and microvascular permeability was estimated by strain gauge plethysmography. RESULTS: The Fontan patients had 17% lower lymphatic pumping pressure (50±3.1 mm Hg) compared with controls (60±2.8 mm Hg; P=0.0341) and a 62% higher contraction frequency (0.8±0.1 min-1) compared with the healthy controls (0.5±0.1 min-1; P=0.0432). Velocity by which the lymph is moved and refill time after manual emptying of the lymphatic vessels showed no differences between the 2 groups. The thoracic duct was elongated 10% ( P=0.0409) and with an abnormal course in the Fontan patients compared with normal. No difference in microvascular permeability was found between the 2 groups. CONCLUSIONS: Patients with a Fontan circulation have an impaired lymphatic pumping capacity and morphologically changed thoracic duct. Our results indicate a challenged lymphatic vasculature in the Fontan circulation and may play a role in the pathogenesis of the complications that are seen in Fontan patients. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov . Unique identifier: NCT03379805.

Spontaneous and α-adrenoceptor-induced contractility in human collecting lymphatic vessels require chloride.

Human lymphatic vessels are myogenically active and respond to sympathetic stimulation. The role of various cations in this behavior has recently been investigated, but whether the anion Cl- is essential is unclear. With ethical approval and informed consent, human thoracic duct and mesenteric lymphatic vessels were obtained from surgical patients. Spontaneous or norepinephrine-induced isometric force production from isolated vessels was measured by wire myography; the transmembrane Cl- gradient and Cl- channels were investigated by substitution of extracellular Cl- with the impermeant anion aspartate and inhibition of Cl- transport and channels with the clinical diuretics furosemide and bendroflumethiazide as well as DIDS and 5-nitro-2-(3-phenylpropylamino)benzoic acid. The molecular expression of Ca2+-activated Cl- channels was investigated by RT-PCR, and proteins were localized using immunoreactivity. Spontaneous and norepinephrine-induced contractility in human lymphatic vessels was highly abrogated after Cl- substitution with aspartate. About 100-300 µM DIDS or 5-nitro-2-(3-phenylpropylamino)benzoic acid inhibited spontaneous contractile behavior. Norepinephrine-stimulated tone was furthermore markedly abrogated by 200 µM DIDS. Furosemide lowered only spontaneous constrictions, whereas bendroflumethiazide had nonspecific inhibitory effects. Consistent expression of transmembrane member 16A [TMEM16A (anoctamin-1)] was found in both the thoracic duct and mesenteric lymphatic vessels, and immunoreactivity with different antibodies localized TMEM16A to lymphatic smooth muscle cells and interstitial cells. The significant change in contractile function observed with inhibitors and anion substitution suggests that Cl- movement over the plasma membrane of lymphatic myocytes is integral for spontaneous and α-adrenoceptor-evoked contractility in human collecting lymphatic vessels. Consistent detection and localization of TMEM16A to myocytes suggests that this channel could play a major functional role. NEW & NOTEWORTHY In this study, we report the first observations of Cl- being a critical ionic component of spontaneous and agonist-evoked contractility in human lymphatics. The most consistently expressed Ca2+-activated Cl- channel gene in the human thoracic duct and mesenteric lymphatic vessels appears to be transmembrane member 16A, suggesting that this channel plays a major role.

A Validation Study of Near-Infrared Fluorescence Imaging of Lymphatic Vessels in Humans.

BACKGROUND: Near-infrared fluorescence (NIRF) imaging is a new imaging technique that is used to visualize lymphatic vessels in humans. It has a high spatial and temporal resolution, allowing real-time visualization of lymphatic flow. METHODS AND RESULTS: The current study investigated the intra- and inter-individual variability of the technique, and how local hypo- and hyperthermia (20°C, 40°C), as well as exercise affect lymph transport. In this study, 10 healthy volunteers were studied twice, with 2 weeks between. NIRF imaging was conducted by using intradermal Indocyanine green injections and a custom-built camera setup. All data were blinded before analysis and presented as mean ± standard deviation. Mean contraction frequency and lymph propulsion velocity were 0.59 ± 0.13 minutes-1 and 1.51 ± 0.24 cm/s, respectively, with no significant difference during each 4 hours examination or between the two visits. The maximal pressure that the lymphatic flow in the vessels could overcome on test day 1 and 2 was 56 ± 9 mmHg and 57 ± 9 mmHg, respectively (p = 0.496). Local hyperthermia increased contraction frequency from 0.62 ± 0.4 minutes to 1.46 ± 0.5 minutes-1 (p < 0.05). Hypothermia caused no significant changes. Immediately after exercise (exercising at a simulated distance of 1.4 km on a cycle ergometer), an increase in lymph propulsion velocity from 1.5 ± 0.49 to 2.2 ± 0.63 cm/s was observed (p < 0.05); whereas contraction frequency was unaltered. A decrease in contraction frequency from 0.68 ± 0.25 minutes to 0.35 ± 0.19 minutes-1 was observed 10 minutes after exercise, without a change in velocity. CONCLUSIONS: NIRF imaging can be conducted for 4 hours without a change in lymphatic activity. Furthermore, it has the sensitivity to detect changes in lymphatic activity by local hyperthermia and exercise. No changes were seen after local hypothermia. Pumping pressure shows good repeatability, whereas the other parameters show poor repeatability.

Spontaneous and Evoked Contractility of Human Intestinal Lymphatic Vessels.

BACKGROUND: Mesenteric lymphatic vessels (MLVs) from various animal species have been intensively studied. We aimed to establish the viability and basic contractile characteristics of human MLVs maintained in vitro and to determine the reactivity of MLVs with norepinephrine (NE) and substance P (SP) and to compare with the thoracic duct (TD). METHODS AND RESULTS: Isolated human lymphatic vessels were mounted on a wire myograph under isometric conditions and tension was recorded. The diameter-tension characteristics for MLVs were generated by stretching the vessels and stimulating with a 125 mM K+ solution containing 10 µM NE. The diameter-tension data generated for MLVs from two separate surgical patient groups were found to be similar: maximum active tension for MLVs occurred when the passive stretch corresponded to a transmural pressure of 22 mmHg. Subsequent experiments on human MLVs were performed by normalization with 22 mmHg as the equivalent target pressure. The majority of MLVs were responders (spontaneous activity and/or reactivity with 10 µM NE or 125 mM K+ solution). Nonresponders (16% of vessel segments) had significantly smaller inner diameters. MLVs responded consistently to NE (1 nM-10 µM) but the responsiveness of MLVs and TD to SP (0.1 nM-10 µM) was poor: TD reacted only with 10 µM SP, whereas MLVs were sensitive to nanomolar concentrations and the contractile response declined with higher concentrations. CONCLUSIONS: Under in vitro isometric conditions, human MLVs generate maximum tension when stretched to a passive level corresponding to 22 mmHg, and the majority of MLVs are responsive when normalized to this pressure. MLVs respond to NE and SP though NE produces a more consistent response in the concentration range tested.

Lymph vessels: the forgotten second circulation in health and disease.

The lymphatic circulation is still a somewhat forgotten part of the circulatory system. Despite this, novel insights in lymph angiogenesis in health and disease, application of immune markers for lymphatic growth and differentiation and also the introduction of new imaging techniques to visualize the lymphatic circulation have improved our understanding of lymphatic function in both health and disease, especially in the last decade. These achievements yield better understanding of the various manifestations of lymph oedemas and malformations, and also the patterns of lymphovascular spread of cancers. Immune markers that recognize lymphatic endothelium antigens, such as podoplanin, LYVE-1 and Prox-1, can be successfully applied in diagnostic pathology and have revealed (at least partial) lymphatic differentiation in many types of vascular lesions.

Use of Fish Scale-Derived BioCornea to Seal Full-Thickness Corneal Perforations in Pig Models.

The aim of this study was to test the use of BioCornea, a fish scale-derived collagen matrix for sealing full-thickness corneal perforations in mini-pigs. Two series of experiments were carried out in 8 Lan-Yu and 3 Göttingen mini-pigs, respectively. A 2mm central full thickness corneal perforation was made with surgical scissors and 2mm trephines. The perforations were sealed immediately by suturing BioCornea to the wounded cornea. The conditions of each patched cornea were followed-up daily for 3 or 4 days. Status of operated eyes was assessed with slit lamp examination or optical coherence tomography (OCT). Animals were sacrificed after the study period and the corneas operated were fixated for histological examination. Both OCT imaging and handheld slit lamp observations indicated that a stable ocular integrity of the perforated corneas was maintained, showing no leakage of aqueous humor, normal depth of anterior chamber and only mild swelling of the wounded cornea. Hematoxylin and eosin staining of the patched cornea showed no epithelial ingrowths to the perforated wounds and no severe leucocyte infiltration of the stroma. The fish scale-derived BioCornea is capable to seal full-thickness corneal perforation and stabilize the integrity of ocular anterior chamber in pre-clinic mini-pig models. BioCornea seems to be a safe and effective alternative for emergency treatment of corneal perforations.

Publication rate and PhD enrolment following a medical pre-graduate research programme.

INTRODUCTION: In the 1990s, the publication and PhD recruitment rates following the Danish pre-graduate research programme (PGRP) in medicine were 54% and 33%, respectively. Updated estimates are unknown. METHODS: All medical students enrolled in the PGRP at the Faculty of Medicine, Aarhus University (Health), Denmark, during 2003-2012 were included (n = 687). The PGRP files were merged with PhD students' files at Health. A systematic literature search was completed for research students who had enrolled during the 2006-2009 period (n = 227). The factors investigated were student age, sex, PGRP completion time and years in medical school at the time of PGRP initiation. Supervisors were described by sex, title, position and affiliation. Calculations were tested by the chi-squared test; p < 0.05 was considered significant. RESULTS: A larger proportion of male medical students conducted a PGRP compared to female medical students (28% versus 19%; p < 0.01). Within three and a half years from PGRP initiation, 13% of the research students had enrolled in a PhD programme at Health, and 52% had published ≥ 1 paper with ≥ 1 supervisor. The research student was the first author on 43% of the overall 224 papers, and 90% were original articles. Publication was positively associated with completion of the PGRP in < 18 months and with embarking on a PhD and with having a male main supervisor. PhD recruitment was related to enrolment in the PGRP after fewer years in medical school. CONCLUSIONS: Fast completion of the PGRP and early enrolment in the programme were associated with scientific publishing and PhD recruitment. The publication rate has remained stable over time.

Voltage-gated sodium channels contribute to action potentials and spontaneous contractility in isolated human lymphatic vessels.

Voltage-gated sodium channels (VGSC) play a key role for initiating action potentials (AP) in excitable cells. VGSC in human lymphatic vessels have not been investigated. In the present study, we report the electrical activity and APs of small human lymphatic collecting vessels, as well as mRNA expression and function of VGSC in small and large human lymphatic vessels. The VGSC blocker TTX inhibited spontaneous contractions in six of 10 spontaneously active vessels, whereas ranolazine, which has a narrower VGSC blocking profile, had no influence on spontaneous activity. TTX did not affect noradrenaline-induced contractions. The VGSC opener veratridine induced contractions in a concentration-dependent manner (0.1-30 µm) eliciting a stable tonic contraction and membrane depolarization to -18 ± 0.6 mV. Veratridine-induced depolarizations and contractions were reversed ∼80% by TTX, and were dependent on Ca(2+) influx via L-type calcium channels and the sodium-calcium exchanger in reverse mode. Molecular analysis determined NaV 1.3 to be the predominantly expressed VGSC isoform. Electrophysiology of mesenteric lymphatics determined the resting membrane potential to be -45 ± 1.7 mV. Spontaneous APs were preceded by a slow depolarization of 5.3 ± 0.6 mV after which a spike was elicited that almost completely repolarized before immediately depolarizing again to plateau. Vessels transiently hyperpolarized prior to returning to the resting membrane potential. TTX application blocked APs. We have shown that VGSC are necessary for initiating and maintaining APs and spontaneous contractions in human lymphatic vessels and our data suggest the main contribution from comes NaV 1.3. We have also shown that activation of these channels augments the contractile activity of the vessels.