Duct Lymph Research Articles

Enhancement of the lymphatic system following intravenous administration of ferumoxytol.

Lymphatic imaging is becoming increasingly important in the management of patients with congenital heart disease. However, the influence of the intravenous contrast agent ferumoxytol on lymphatic imaging is not well understood. To evaluate the impact of intravenous ferumoxytol on T1-weighted and T2-weighted lymphatic imaging in patients with congenital heart disease. We included consecutive patients receiving ferumoxytol-enhanced 3D angiography for congenital heart disease evaluation. The visibility of the thoracic duct was reviewed on the T1-weighted 3D inversion recovery balanced-steady-state free precession (SSFP) with respiratory navigator gating sequence which is routinely used for angiography and the heavily T2-weighted turbo spin echo sequence which is employed for lymphatic imaging. Data on demographics and time interval between contrast administration and imaging were collected. Statistical analyses were performed using t-tests for continuous variables and chi-squared tests for categorical variables. One hundred nineteen consecutive patients with a mean age of 12.46 years±7.7 years were included. Of these, 45 cases underwent both T1-weighted and T2-weighted imaging; the other 74 underwent only T1-weighted imaging. Of the 45 patients, 20 had thoracic duct enhancement on T1-weighted imaging; among the 26 sedated, only 2 showed enhancement, while 18 of 19 non-sedated patients showed enhancement (P<0.001), indicating a strong association between sedation and reduced thoracic duct visibility. If T2-weighted imaging was performed after contrast administration, the thoracic duct was not visible on those images. For all 45 cases of visible thoracic duct in the entire cohort, the time from contrast administration to imaging ranged from 8 min up to 75 min. The enhancement of the thoracic lymphatic duct on T1-weighted imaging, coupled with degradation observed on T2-weighted imaging, suggests that intravenously administered ferumoxytol rapidly enters the lymphatic fluid. To prevent T2 shortening from degrading the imaging results, T2-weighted imaging for lymphatic evaluation should be performed prior to the administration of ferumoxytol. Sedation and, by inference, fasting may influence this property and warrant further investigation in future studies.

Selective Lymphatic Duct Embolization for Treatment of Thoracic Lymphatic Flow Disorders in Children: Technical Aspects and Comparison with Thoracic Duct Embolization

PurposeTo assess effectiveness of selective lymphatic duct embolization (SLDE) for treatment of thoracic lymphatic flow disorders, performed to maintain patency of the thoracic duct (TD), compared to thoracic duct embolization (TDE). Materials and MethodsRecords of 39 patients (mean age 7.6±7.1 years) with thoracic lymphatic flow disorders who underwent 43 SLDE procedures were analyzed and compared to a cohort of 104 patients (7.8±7.6 y) who underwent TDE. Relevant clinical and imaging data were collated.All patients presented with chylous effusion and/or plastic bronchitis. For the SLDE cohort, etiology of disorders included single-ventricle heart disease palliation in 28 patients (72%) and vascular malformation/aneuploidy in 8 (21%). For the TDE cohort, 92/104(88%) had single-ventricle heart disease palliation. ResultsSLDE was performed with glue via microcatheter in 35 procedures, and dextrose flood technique was used in 26. SLDE via direct needle access was performed in 11.After SLDE, presenting symptoms resolved in 33/39 patients (85%), improved in 5 (13%), and were unchanged in 1 (3%) (mean follow-up 693±523 days). The TD remained patent in all cases. There was a significant difference in outcomes (P=0.001) with the TDE cohort—symptoms resolved or improved in 75/104 patients (72%), were unchanged in 15 (14%); and new leak (e.g., ascites, protein-losing enteropathy) developed in 14 TDE patients (13%) (follow-up 1041±879 d). ConclusionSLDE was effective for treatment of thoracic lymphatic flow disorders, and outcomes were comparable to TDE. Selective techniques preserve the patency of the TD and may have potential benefits that warrant further study.

The right lymphatic duct: basic anatomy and clinical relevance.

The anatomical variability of the thoracic duct and the right lymphatic duct predisposes them to inadvertent damage following head and neck surgery thereby leading to chyle leak which is an uncommon complication with potentially significant associated morbidity. Although chyle leak is predominately associated with left-sided neck surgery, it also occurs as a complication of the right-sided neck dissection. Variable figures concerning chyle leakage after right-sided neck dissections were reported, ranging from 0 per cent to higher prevalences such as 14%, 24%, 33% and 60% of total cases of chyle leakages associated with neck surgery. The right-sided complications may implicate the right lymphatic duct and right-sided terminations of the thoracic duct into the venous system which occur in about 1-6% of humans. Other clinically relevant conditions involving the right-sided major lymphatic vessels include chyle leaks following right anterior cervical spine surgery, cysts of the right lymphatic duct and dilatation of the right lymphatic duct in the setting of recurrent cervical swelling. This article presents a review of the literature concerning the basic anatomy and the clinical relevance of the right lymphatic duct and the right-sided terminations of the thoracic duct into the venous circulation.

High-fat feeding drives the intestinal production and assembly of C16:0 ceramides in chylomicrons.

Consumption of a diet rich in saturated fat increases lipid absorption from the intestine, assembly into chylomicrons, and delivery to metabolic tissues via the lymphatic and circulatory systems. Accumulation of ceramide lipids, composed of sphingosine and a fatty acid, in metabolic tissues contributes to the pathogenesis of cardiovascular diseases, type 2 diabetes mellitus and cancer. Using a mesenteric lymph duct cannulated rat model, we showed that ceramides are generated by the intestine and assembled into chylomicrons, which are transported via the mesenteric lymphatic system. A lipidomic screen of intestinal-derived chylomicrons identified a diverse range of fatty acid, sphingolipid, and glycerolipid species that have not been previously detected in chylomicrons, including the metabolically deleterious C16:0 ceramide that increased in response to high-fat feeding in rats and human high-lipid meal replacement enteral feeding. In conclusion, high-fat feeding increases the export of intestinal-derived C16:0 ceramide in chylomicrons, identifying a potentially unknown mechanism through which ceramides are transported systemically to contribute to metabolic dysfunction.

Major and Trace Element Composition Differences Revealed in Porcine Intestine by Dynamic Analysis and MeV Ion Microscopy

Physiologically relevant concentrations in biological tissue, in the in vivo, state are of the order of μmol L−1 and mmol L−1. Up to the present, mapping the major elements in the matrix and its thickness has been neglected, despite their importance for quantification of lesser and trace element concentrations. Ryan and Jamieson's dynamic analysis, statistical spectral decomposition approach, is developed to quantitatively measure ex vivo tissue sections cut using a cryomicrotome. This mitigates the problem that physical analysis methods require a vacuum environment. This approach is used to quantitatively image the major matrix elements H, C, N, and O as well as trace maps of Ca, Fe, and Zn in a tissue section of porcine intestine. This sample is selected as it exhibits a complex morphology with multiple tissue compartments (such as muscle and mucosa, as well as void areas from blood vessels, lymph ducts, sinuses crypts, and villi. In the results, it is demonstrated that different tissue types can have a different matrix composition and thickness. Using this information, quantitative maps and elemental molarities for the lesser and trace elements Ca, Fe, and Zn are obtained.

IDENTIFICATION OF MICROFILARIAE USING CONVENTIONAL POLYMERASE CHAIN REACTION AND QPCR-HRM

Background: The presence of filarial worms in the lymph nodes can result in acute symptoms, such as inflammation of the lymph nodes and ducts, particularly in the groin region. As part of the life cycle of filariasis, symptomatic or asymptomatic patients with microfilariae in their blood can transmit the disease via mosquito bites. The inspection of microfilariae that is currently being developed uses Polymerase Chain Reaction (PCR) to carry out a unique DNA search technique. Purpose: Identify the type of microfilaria present in filariasis patients using Quantitative PCR High- Resolution Melting (qPCR-HRM) and conventional PCR techniques. Method: This study involved the examination of 19 samples using the qPCR-HRM method. Subsequently, the results that were considered positive for microfilaria underwent further testing using conventional PCR. Result: The results of the examination using these two methods revealed the presence of Brugia malayi and Wuchereria bancrofti microfilariae with peak melting temperatures ranging from 78.2 – 78.7 °C and 80.8 – 81.2 °C, and fragment sizes of 199 bp and 227 bp, respectively. Conclusion: Based on the results of the identification from these two methods, it is evident that microfilariae of Brugia malayi and Wuchereria bancrofti can be detected using both conventional and qPCR-HRM methods.

Risk factors of postoperative airway obstruction complications in children with oral floor mass.

The aim of the present study was to explore the risk factors of postoperative airway complications in children with oral floor mass. The first choice of auxiliary examination method for children with oral floor mass is also proposed. This retrospective study included 50 children with floor-of-mouth (FOM) masses. Medical records were reviewed, and information on age of onset, functional impacts present, age at consultation, imaging findings, history of preoperative aspiration, pathology findings, properties of biopsied fluid, treatment modality, postoperative outcomes, and operation were recorded. A total of 20 patients exhibited functional impacts such as difficulty in breathing and feeding. Ultrasound examination was performed in 28 cases; and magnetic resonance imaging, in 38 cases. The diagnosis was lymphatic malformation in 12 cases, developmental cyst in 29 cases, and solid mass in 7 cases. There were 28 cases of surgical resection, 9 cases underwent multiple puncture volume reduction followed by surgery, 11 cases treated using sclerotherapy injection, and 1 case treated using sclerotherapy injection and surgical resection. Young age, functional impact, and high grade of lymphatic duct malformation increased the risk of surgical treatment. B-scan ultrasound is the first choice for the diagnosis of FOM masses in children.

A case of early-stage type 3 gastric neuroendocrine tumor in the upper body of the stomach: is endoscopic resection feasible?

Although gastric neuroendocrine tumors (NETs) are uncommon compared with gastric carcinomas, the incidence of NETs has been recently increasing. Gastric NETs are classified into three subgroups, and among these, gastrin-independent sporadic type 3 gastric NETs have a poor prognosis because of frequent lymph node or distant metastasis. We experienced a case of an early-stage type 3 gastric NET associated with lymphovascular and submucosal invasion. In a 54year-old woman, esophagogastroduodenoscopy performed during a health screening identified an elevated lesion of the upper body of the stomach. The results of immunohistochemical analyses of endoscopic biopsy specimens obtained from the lesion were positive for chromogranin A and synaptophysin, indicating an NET. Because the patient's serum gastrin level was normal and she had no predisposing conditions for NET development, the tumor was diagnosed as a type 3 gastric NET. The patient underwent local resection of the tumor and regional lymph node dissection. The resected specimen indicated a diagnosis of type 3 gastric NET with invasion into the submucosa and lymphatic duct. This is an extremely rare case of an early-stage type 3 gastric NET. Our discussion provides insight into the pathogenesis and development of these tumors and the appropriate therapeutic strategy.

Options to apply national developments in the assessment of sentinel lymph node involvement in breast cancer

Background. Breast cancer is the leading oncopathology of women. The routine radical surgery performed in this pathology includes lymph node dissection, which provokes development of postmastectomy syndrome. However, the removal of non-metastatic lymph nodes is not rational according to the subsequent disability of the patients. This can be avoided by using a sentinel lymph node (SLN) biopsy procedure. At this stage of oncology development, there are several ways to visualize SLN. The fluorescent method is among the most promising. This technique has been used for many years. However, it is not sufficiently implemented in clinical practice. There are still several questions about the procedure for its performance. In addition, it requires the introduction and improvement of domestic developments, including reducing financial costs.Aim. To study the use of indocyanine green of domestic production (LLC Firm “FERMENT”, Russia) and the IC-GOR detection system (LLC “MedKomplekt”, Russia) for SLN biopsy in patients with early breast cancer.Materials and methods. From February to September 2023, biopsy of SLN using indocyanine green (LLC Firm “FERMENT”, Russia) was performed in 53 patients with early breast cancer without clinically detectable lesion of regional lymph nodes. In all cases, according to the clinical examination, the patients had an operable stage of breast cancer (cT1–3N0M0). 5 mg of indocyanine green, dissolved in 4 ml of water for injection, was administered after sanitizing of the surgical field intradermally and subcutaneously at 2 points in the upper-outer quadrant of the breast along the edge of the areola in 40 patients (75.5 %) or paratumorally in 13 patients (24.5 %). An incision in the axilla about 4 cm long was made no earlier than 10–15 minutes after injection of indocyanine green (when visualizing the track 1 cm beyond its distal end to avoid crossing the lymph duct, after which the drug can flow into the wound). After imaging, all detected lymph nodes were removed for planned morphological examination. Standard lymph node dissection of 1 and 2 level was performed in all patients. Middle age of patients was 64.5 years (from 37 to 85 year). In 40 patients (75.5 %) modified radical mastectomy was performed, breast conserving surgery was done in 13 cases (24.5 %).Results. SLN were visualized in 51 patients out of 53 (96.2 %). After the final morphological examination, the majority of patients in the group were ranged in the IA and IIA stages of the disease – 15 (28.3 %) and 28 (52.8 %), respectively. Metastasis in the SLN were found in 9 patients (17.0 %). Besides, in 3 cases (5.7 %) metastasis in the lymph nodes were found after lymph node dissection. In 4 cases (7.6 %) metastasis were found during lymph node dissection but were not detected in the removed SLN. Thus, in the study group 13 (24.5 %) patients had metastatic lymph node lesion despite negative clinical status. The total number of removed SLN in the study group was 169 (from 1 to 6), the average number of removed lymph nodes was 3.3. Any negative events, allergic and general reactions to indocyanine were not reported.Conclusion. Our technique of contrasting SLN with indocyanine green is adequate and reproducible. The frequency of detection of SLN with this method is 96.2 %, with an acceptable level of false negative results is 7.6 %. Indocyanine green (LLC Firm “FERMENT”, Russia) and the LED fluoroscopic cancer detector IC-GOR (LLC “MedKomplekt”, Russia) can be recommended for performing a SLN biopsy.

Lymphatic Chyle Duct Injury and Identification During Laparoscopic Sleeve Gastrectomy Preventing Postoperative Chylous Ascites

We present a case of intraoperative detection of an iatrogenic chyle duct injury during laparoscopic sleeve gastrectomy. The chyle duct injury was identified and managed by ligature, preventing postoperative chylous ascites.

Quantifying the Lymphatic Transport of Model Therapeutics from the Brain in Rats.

In recent years, the drainage of fluids, immune cells, antigens, fluorescent tracers, and other solutes from the brain has been demonstrated to occur along lymphatic outflow pathways to the deep cervical lymph nodes in the neck. To the best of our knowledge, no studies have evaluated the lymphatic transport of therapeutics from the brain. The objective of this study was to determine the lymphatic transport of model therapeutics of different molecular weights and lipophilicity from the brain using cervical lymph cannulation and ligation models in rats. To do this, anesthetized Sprague-Dawley rats were cannulated at the carotid artery and cannulated, ligated, or left intact at the cervical lymph duct. Rats were administered 14C-ibuprofen (206.29 g/mol, logP 3.84), 3H-halofantrine HCl (536.89 g/mol, logP 8.06), or 3H-albumin (∼65,000 g/mol) via direct injection into the brain striatum at a rate of 0.5 μL/min over 16 min. Plasma or cervical lymph samples were collected for up to 6-8 h following dosing, and brain and lymph nodes were collected at 6 or 8 h. Samples were subsequently analyzed for radioactivity levels via scintillation counting. For 14C-ibuprofen, plasma concentrations over time (plasma AUC0-6h) were >2 fold higher in lymph-ligated rats than in lymph-intact rats, suggesting that ibuprofen is cleared from the brain primarily via nonlymphatic routes (e.g., across the blood-brain barrier) but that this clearance is influenced by changes in lymphatic flow. For 3H-halofantrine, >73% of the dose was retained at the brain dosing site in lymph-intact and lymph-ligated groups, and plasma AUC0-8h values were low in both groups (<0.3% dose.h/mL), consistent with the high retention in the brain. It was therefore not possible to determine whether halofantrine undergoes lymphatic transport from the brain within the duration of the study. For 3H-albumin, plasma AUC0-8h values were not significantly different between lymph-intact, lymph-ligated, and lymph-cannulated rats. However, >4% of the dose was recovered in cervical lymph over 8 h. Lymph/plasma concentration ratios of 3H-albumin were also very high (up to 53:1). Together, these results indicate that 3H-albumin is transported from the brain not only via lymphatic routes but also via the blood. Similar to other tissues, the lymphatics may thus play a significant role in the transport of macromolecules, including therapeutic proteins, from the brain but are unlikely to be a major transport pathway from the brain for small molecule drugs that are not lipophilic. Our rat cervical lymph cannulation model can be used to quantify the lymphatic drainage of different molecules and factors from the brain.

Ivacaftor pharmacokinetics and lymphatic transport after enteral administration in rats.

Background: Ivacaftor is a modern drug used in the treatment of cystic fibrosis. It is highly lipophilic and exhibits a strong positive food effect. These characteristics can be potentially connected to a pronounced lymphatic transport after oral administration. Methods: A series of studies was conducted to describe the basic pharmacokinetic parameters of ivacaftor in jugular vein cannulated rats when dosed in two distinct formulations: an aqueous suspension and an oil solution. Additionally, an anesthetized mesenteric lymph duct cannulated rat model was studied to precisely assess the extent of lymphatic transport. Results: Mean ± SD ivacaftor oral bioavailability was 18.4 ± 3.2% and 16.2 ± 7.8%, respectively, when administered as an aqueous suspension and an oil solution. The relative contribution of the lymphatic transport to the overall bioavailability was 5.91 ± 1.61% and 4.35 ± 1.84%, respectively. Conclusion: Lymphatic transport plays only a minor role in the process of ivacaftor intestinal absorption, and other factors are, therefore, responsible for its pronounced positive food effect.

Size adjustment suture technique for lymphaticovenular anastomosis.

In this report, we describe a super microsurgical technique that enables rapid and accurate anastomosis while adjusting for caliber differences when anastomosing a small-caliber lymphatic vessel and a vein with a larger caliber, which is frequently encountered in surgeries such as lymphaticovenous anastomosis (LVA). The suture size adjustment technique was performed in 30 anastomoses of lymphatic vessels and veins, whose diameter of lymph duct was at least two times smaller than that of the vein. The type of lymphedema, caliber of lymphatic vessels and veins anastomosed, caliber ratio, vein wall thickness, modified caliber ratio after vein wall thickness subtracted, presence of additional anastomosis, and anastomosis time were examined. On average, the lymphatic vessels had a diameter of 0.61 mm, while the veins were 1.43mm in diameter. The mean caliber ratio of vein to lymphatic vessel was 2.3, while the modified caliber ratio of vein-to-lymphatic vessel was 1.5 on average. The average venous wall thickness was 0.51. The average anastomosis time was 9.1min and no additional anastomosis due to leakage was necessary in any case. We successfully performed an anastomosis of lymphatic vessels and veins with different calibers, which can maintain long-term patency while adjusting the caliber difference and suppressing leakage at the anastomosis site. Finally, the caliber of the vein is commonly larger than that of the lymphatic vessel to be anastomosed in many cases of LVA surgery, indicating that the proposed anastomosis method could be of therapeutic use in many cases.

Release of Lipids Stored in the Intestine by Glucagon-Like Peptide-2 Involves a Gut-Brain Neural Pathway.

The gut hormone GLP-2 (glucagon-like peptide-2) plays important roles in lipid handling in the intestine. During postabsorptive stage, it releases preformed chylomicrons stored in the intestine, the underlying mechanisms of which are not well understood. Previous studies implicate the involvement of neural pathways in GLP-2's actions on lipid absorption in the intestine, but the role of such mechanisms in releasing postabsorptive lipid storage has not been established. Here, in mesenteric lymph duct cannulated rats, we directly tested whether gut-brain neural communication mediates GLP-2's effects on postabsorptive lipid mobilization in the intestine. We performed total subdiaphragmatic vagotomy to disrupt the gut-brain neural communication and analyzed lipid output 5 hours after a lipid load in response to intraperitoneal GLP-2 or saline. Peripheral GLP-2 administration led to increased lymph lipid output and activation of proopiomelanocortin neurons in the arcuate nucleus of hypothalamus. Disruption of gut-brain neural communication via vagotomy blunted GLP-2's effects on promoting lipid release in the intestine. These results, for the first time, demonstrate a novel mechanism in which postabsorptive mobilization of intestinal lipid storage by GLP-2 enlists a gut-brain neural pathway.

Is Immediate Lymphatic Reconstruction on Breast Cancer Patients Oncologically Safe? A Preliminary Study

Background: In breast cancer patients receiving axillary lymph node dissection (ALND), immediate lymphatic reconstruction (ILR) with lymphovenous anastomosis is an emerging technique for reducing the risk of arm lymphedema. However, the oncologic safety of surgically diverting lymphatic ducts directly into venules in a node-positive axilla is still a concern of inadvertently inducing metastasis of remaining cancer cells. This study aimed to assess the oncologic safety of ILR. Methods: From January 2020 to January 2022, 95 breast cancer patients received ALND, and 45 of them also received ILR. Patients with recurrent cancer, with follow-up less than 12 months, and with missed data were excluded. Variables were compared between ILR and non-ILR groups, and the outcome of interest was the rate of distant recurrence after follow-up for at least 1 year. Results: Thirty-four patients in the ILR group and 32 patients in the non-ILR group fulfilled the inclusion criteria for analysis. No statistically significant difference was noted between groups in terms of age, body mass index, type of breast surgery, pathologic cancer staging, histologic type and grade of breast cancer, molecular subtypes, frequency of axillary lymph node metastasis, or adjuvant therapy. For the patients receiving follow-up for at least 1 year, no statistically significant difference was found in terms of distant recurrence rates between ILR and non-ILR groups (P = 0.44). Conclusion: For breast cancer patients receiving ALND, ILR with lymphovenous anastomosis is oncologically safe, within an average follow-up period of 21 months.

Mesenteric Lymph Duct Cannulation in a Rat Model to Harvest Lymph Fluid

Mesenteric Lymph Duct Cannulation in a Rat Model to Harvest Lymph Fluid

Mesenteric Lymph Duct Cannulation in a Rat Model to Harvest Lymph Fluid

Mesenteric Lymph Duct Cannulation in a Rat Model to Harvest Lymph Fluid

Tuberculous Dactilitis in Young Male, a Rare Case

Introduction : Chylothorax is an uncommon medical condition caused by the accumulation of chylous fluid in the pleural space. Chylothorax has no predilection for sex or age. The prevalence after various cardiothoracic surgeries is 0.2% to 1%. Mortality and morbidity rates are around 10%. Respiratory distress may occur due to compression of the lung by the accumulated fluid. Management and approaches to treating the condition require multidisciplinary therapy, starting from non-pharmacological, pharmacological, to interventional management. Case Report : A 57-year-old Man patient was referred to the emergency room with chief complaint of shortness of breath. Reduced breathing sound on both lung fields. No previous history of cancer or thoracic surgery were found. X-ray examination had found bilateral pleural effusion. Thoracocentesis and pleural fluid analysis was performed with total of 6800 cc serosanguinous, whitish fluid was extracted from both of the lung. The patient was diagnosed with chylothorax. Lymphangiography and embolization was performed on the leak on left thoracic duct (T10) from right lymph node. Antibiotic was also given to treat the community acquired pneumonia that could be one of the possible etiology on this patient. Dietary modification with low fat diet and Ocreotide was also given to this patient as one of the treatment modalities. Discussion : The diagnosis of Chylothorax on this patient was established based on pleural fluid analysis and evidenced by lymphangiography examination by the presence of a leak in the thoracic lymphatic duct. Various modalities to diagnose this condition have been carried out with inconclusive results. Non-pharmacological, pharmacological and radiological interventions with embolization through lymphangiography are proven to be able to stop leaks and reduce symptoms in this patient. Conclusion : Chyle leak to the pleural space may compress the lung and cause respiratory distress. Combinaton of thoracocentesis, embolization of the leakage, dietary intake modification and administration of ocreotide may help prevent further chylous fluid accumulation.

Lymphatic Defects in Zebrafish sox18 Mutants Are Exacerbated by Perturbed VEGFC Signaling, While Masked by Elevated sox7 Expression.

Mutations in the transcription factor-coding gene SOX18, the growth factor-coding gene VEGFC and its receptor-coding gene VEGFR3/FLT4 cause primary lymphedema in humans. In mammals, SOX18, together with COUP-TFII/NR2F2, activates the expression of Prox1, a master regulator in lymphatic identity and development. Knockdown studies have also suggested an involvement of Sox18, Coup-tfII/Nr2f2, and Prox1 in zebrafish lymphatic development. Mutants in the corresponding genes initially failed to recapitulate the lymphatic defects observed in morphants. In this paper, we describe a novel zebrafish sox18 mutant allele, sa12315, which behaves as a null. The formation of the lymphatic thoracic duct is affected in sox18 homozygous mutants, but defects are milder in both zygotic and maternal-zygotic sox18 mutants than in sox18 morphants. Remarkably, in sox18 mutants, the expression of the closely related sox7 gene is elevated where lymphatic precursors arise. Sox7 could thus mask the absence of a functional Sox18 protein and account for the mild lymphatic phenotype in sox18 mutants, as shown in mice. Partial knockdown of vegfc exacerbates lymphatic defects in sox18 mutants, making them visible in heterozygotes. Our data thus reinforce the genetic interaction between Sox18 and Vegfc in lymphatic development, previously suggested by knockdown studies, and highlight the ability of Sox7 to compensate for Sox18 lymphatic dysfunction.

Unanticipated Enhancement of Intestinal TG Output by Apoc3 ASO Inhibition.

The objective of this study was to investigate whether apoC3 (apolipoprotein C3) inhibition with an antisense oligonucleotide (ASO) modulates intestinal triglyceride secretion. Sprague-Dawley rats were treated with subcutaneous injections of apoC3 ASO 25 mg/kg twice weekly or inactive ASO for 4 weeks before the assessment of lymph flow, triglyceride and apoB48 appearance in the lymph. Rats were surgically implanted with catheters in the mesenteric lymph duct and duodenum. Following an overnight fast, an intraduodenal lipid bolus (1.5-mL intralipid) was administered. Lymph fluid was collected for the following 4 hours to compare effects on lymph flow, lymph triglyceride and apoB48 concentration, and secretion. To assess suppression of apoC3 expression and protein abundance by apoC3 ASO compared with inactive ASO (placebo), intestinal and hepatic tissues were collected from a subset of animals before (fasting) and after an enteral lipid bolus (post-lipid). ApoC3 ASO significantly reduced apoC3 mRNA expression in the liver compared with inactive ASO (fasting: 42%, P=0.0048; post-lipid: 66%, P<0.001) and in the duodenum (fasting: 29%, P=0.0424; post-lipid: 53%, P=0.0120). As expected, plasma triglyceride also decreased significantly (fasting: 74%, P<0.001; post-lipid: 33%, P=0.0276). Lymph flow and cumulative lymph volume remained unchanged following apoC3 ASO therapy; however, lymph triglyceride, but not apoB48 output, increased by 38% (ANOVA, P<0.001). Last, no changes were observed in stool triglyceride, intestinal fat (quantified via oil red O staining), and expression of mRNAs involved in triglyceride synthesis, lipid droplet formation, and chylomicron transport and secretion. Despite the marked reduction in plasma triglyceride concentration that occurs with apoC3 ASO inhibition, intestinal triglyceride output surprisingly increased rather than decreased. These data demonstrate that the reduction of intestinal triglyceride output does not contribute to the potent plasma triglyceride-lowering observed with this novel therapy for hypertriglyceridemia. Further studies are required to explore the mechanism of this intestinal effect.