Inhibition of the mammalian target of rapamycin impedes lymphangiogenesis

Lymphatic malformation:Classification, Pathogenesis and Therapeutic Strategies

Lymphatic malformation is a lymphatic system tumor caused by abnormal development during the embryonic period, which leads to structural defects in the lymphatic vessels. It originates from lymphatic endothelial cells and is prone to occur in the lymphatic vessels of the head, neck and axilla. It is characterized by abnormal proliferation and cystic expansion of lymphatic endothelial cells. In the current study of the molecular mechanism of lymphatic malformation, phosphatidylinositol-4,5-bisphosphate3-kinase catalytic subunit alpha and phosphoinositide-3-kinase regulatory subunit 3 gene mutations lead to abnormal activation of PI3K/AKT/mTOR signaling pathway, promoting lymphatic malformation lymphatic endothelial cells proliferation and lymphangiogenesis; vascular endothelial growth factor C binds to vascular endothelial growth factor receptor 3 to promote the survival, proliferation and migration of lymphatic endothelial cells. Overexpression of vascular endothelial growth factor C is involved in the formation of lymphatic malformation subtype gorham-stout disease; in the Wnt/β-catenin signaling pathway, wingless-type MMTV integration site family member 5A loss leads to the occurrence of lymphatic malformation; asparaginyl-tRNA synthetase mutations activate extracellular signal-regulated kinase phosphorylation, driving the occurrence of lymphatic malformation subtypes generalized lymphatic abnormality and kaposiform lymphangiomatosis. Clinically, treatment strategies are symptom-oriented and individualized according to the location and clinical manifestations of the disease. In recent years, mTOR inhibitor silomus and vascular endothelial growth factor receptor 3 inhibitors are effective in the treatment of lymphatic malformation. This review aims to explore the latest progress of clinical manifestations, pathogenesis and treatment methods of lymphatic malformation.

Sirolimus for kaposiform hemangioendothelioma: Potential mechanisms of action and resistance

Kaposiform hemangioendotheliomas (KHEs) are vascular tumors that are considered borderline or locally aggressive and may lead to lethal outcomes. Traditional therapies, such as surgery and embolization, may be insufficient or technically impossible for patients with KHE. Sirolimus (or rapamycin), a specific inhibitor of mechanistic target of rapamycin, has recently been demonstrated to be very useful in the treatment of KHEs. Here, we highlight recent substantial progress regarding the effects of sirolimus on KHEs and discuss the potential mechanisms of action of sirolimus in treating this disease. The prevention of platelet activation and inflammation, along with antiangiogenic effects, the inhibition of lymphangiogenesis, the attenuation of fibrosis, or a combination of all these effects, may be responsible for the therapeutic effects of sirolimus. In addition, the mechanism of sirolimus resistance in some KHE patients is discussed. Finally, we review the somatic mutations that have recently been identified in KEH lesions, and discuss the potential of novel therapeutic targets based on these further understandings of the cellular and molecular pathogenesis of KHE.

Clinical characteristics and genetic analysis of a patient with diffuse pulmonary lymphangiomatosis: a case report and literature review

BACKGROUND

Diffuse pulmonary lymphangiomatosis (DPL) is a rare pulmonary disorder, which affects the lymphatic channels from the mediastinum to the pleura. DPL is often misdiagnosed or missed due to the lack of clear specificity and definitive medical therapies. In most cases, the disease progresses to chronic morbidity or even death.

CASE PRESENTATION

Here, we have reported a case of DPL in a 17-year-old boy who presented with hemoptysis and progressive breathlessness. The diagnosis was confirmed based on the typical imaging features observed through high-resolution computed tomography, chest magnetic resonance imaging, and lymphangiography. Furthermore, we have presented the genetic characteristics of the patient and his parents and discovered the following heterozygous variants of BCL6: NM_001706: exon5: c. A463G (p.M155V) and ATM: NM_000051: exon3: c.A107G (p.D36G). The patient underwent treatment with sirolimus for 2 months; his clinical symptoms disappeared completely, and the mediastinum soft mass shrank dramatically.

CONCLUSIONS

Early diagnosis of DPL is challenging for clinicians, and imaging plays an important role in determining the location and severity of the disease. The gene mutation detected in this study may facilitate the pathogenesis of DPL. Sirolimus can prevent further disease progression in the short term, which may be an effective and safe therapeutic alternative for treating DPL.

Immunosuppression Drugs Exhibit Differential Effects on Endothelial Cell Function

Immunosuppressive medications are widely used to treat patients with neoplasms, autoimmune conditions, and solid organ transplants. Prior studies indicate that immunosuppression drugs can cause adverse vascular remodeling. Given the systemic effects of the drugs, elucidating cell-type specific drug-effects has been challenging. We utilized induced pluripotent stem-cell derived endothelial cells to investigate the role of widely used immunosuppression drugs on endothelial function. We found that among immunosuppression agents, sirolimus reduced basic endothelial cell functions including cell migration, proliferation, acetylated LDL uptake, and angiogenesis properties; while tacrolimus only reduced nitric oxide release. This model allows for investigation of differential effect of immunosuppression drugs on endothelial function that can elucidate mechanisms contributing to adverse vascular profiles observed clinically.

Healthcare utilization in patients with head and neck lymphatic malformations with the introduction of sirolimus

OBJECTIVES

Historically, head and neck lymphatic malformations (HNLM) have been managed through surgical and interventional procedures. Sirolimus was introduced in 2016 and has aided in symptomatic control of HNLM. The study objective was to assess healthcare utilization with the introduction of sirolimus for HNLM.

METHODS

An observational cohort study of LM patients treated between 2008 and 2022 at a tertiary care children's hospital was performed. 588 charts were reviewed; patients with isolated, non-syndromic HNLM and at least 2 years of follow-up were included (n = 45). Data included sirolimus use, complications, presence of tracheostomy and/or gastrostomy-tube, and number and costs of HNLM-related sclerotherapies, procedures, hospitalizations, and emergency room visits. For patients who received sirolimus, encounters two years prior to and after sirolimus initiation were recorded. For the non-sirolimus group, encounters two years after the initial clinic visit for HNLM were recorded. Statistical analysis was used to compare the groups.

RESULTS

Median age at first clinic visit was 1.8 years (range 2 days-41 years). Tracheostomy was present in 43 % of sirolimus patients compared with 3 % of the non-sirolimus group (OR: 24.0, 95%CI: 1.55-1490, p = 0.02). Patients on sirolimus experienced significantly fewer sclerotherapy visits (z = 2.08, p = 0.03) compared to the non-sirolimus group. Minimal sirolimus-related side effects were reported. Total HNLM-related costs were significantly less in the sirolimus group during treatment (median $448.13, range $0-$7041.28) compared with before treatment (median $17,069.24, range $1999.16-$211,848.50, z = 2.20, p = 0.03). Median costs associated with sclerotherapy were less for the sirolimus groups during treatment compared with the non-sirolimus group (z = 1.97, p = 0.04). In the sirolimus group, costs associated with HNLM-related hospitalizations were significantly less during sirolimus treatment compared with before (z = 2.20, p = 0.03).

CONCLUSION

Sirolimus has improved the clinical course for HNLM patients by decreasing number of procedures and healthcare costs, with limited side effects. Larger cohorts matching type of HNLM and age are needed to assess healthcare utilization benefits of sirolimus.

Therapeutic Drug Monitoring for Sirolimus in Children with Vascular Anomalies: What Can We Learn from a Retrospective Study

Objectives: Sirolimus (SRL), a mammalian target of rapamycin inhibitor, has been widely used to treat patients with vascular anomalies (VAs). The objectives of this study were to summarize the routine blood SRL monitoring data for VAs children, to investigate the factors contributing to the variable blood SRL concentrations and to evaluate the efficacy and safety of SRL therapy. Methods: VAs patients with routine blood SRL monitoring from July 2017 to April 2022 at the Department of Burns and Plastic Surgery, Children's Hospital of Nanjing Medical University were retrospectively collected. Clinical data were obtained from the hospital information system. Results: In total, 67 children (35 females) were enrolled. The therapeutic drug monitoring data showed that the range of measured blood trough concentrations (Ctrough) was 3.6-46.8 ng/mL. At the initial measurements, only 33% of patients were in the target concentration range (10-15 ng/mL). But this proportion became 54% at the last measurements. The whole blood-Ctrough-to-daily dose (Ctrough/Dose) ratio was significantly associated with age and body weight (BW). The patients' laboratory results did not change significantly after SRL treatment. Although the incidence of adverse events was relatively high (44.8%), most of them were mild and tolerable. 70.3% patients had total responses to SRL, whereas 29.7% children exhibited stable disease or progressive disease. No significant differences were found in Ctrough between the total response group and non-response group. Conclusions: This retrospective study revealed a high variability in SRL blood concentrations in Chinese children with VAs. Of note, pediatric patients with older age and a higher BW had a lower Ctrough/Dose ratio. It is a concern whether the range of 10-15 ng/mL is feasible for Chinese children based only on our study. Further studies recruiting more patients are required to redefine the target reference range for children with VAs.

Targeted therapies for vascular malformations

Targeted medical therapies for the treatment of vascular malformations is an exciting and evolving area of research. As the identification of specific causative genetic mutations involved in vascular malformations becomes more accessible and inexpensive, the development of targeted therapies to address these genetic anomalies becomes all the more enticing. It is an excellent example of the potential of translational research where basic science discoveries are translated to clinical practise from 'bench to bedside'. In this mini-review we aim to synopsise some of the recent studies published in this area with specific focus on the paediatric population. We also aim to highlight the growing demand for future research in the field to elucidate further the optimum duration of treatments, strategies for discontinuation, potential for combination of therapies and the effects of prolonged use of these medications.

Long-term safety and influence on growth in patients receiving sirolimus: a pooled analysis

BACKGROUND

Sirolimus is increasingly utilized in treating diseases associated with mTOR pathway overactivation. Despite its potential, the lack of evidence regarding its long-term safety across all age groups, particularly in pediatric patients, has limited its further application. This study aims to assess the long-term safety of sirolimus, with a specific focus on its impact on growth patterns in pediatric patients.

METHODS

This pooled analysis inlcudes two prospective cohort studies spanning 10 years, including 1,738 participants (aged 5 days to 69 years) diagnosed with tuberous sclerosis and/or lymphangioleiomyomatosis. All participants were mTOR inhibitor-naive and received 1 mg/m²/day of sirolimus, with dose adjustments during a two-week titration period to maintain trough blood concentrations between 5 and 10 ng/ml (maximum dose 2 mg). Indicators of physical growth, hematopoietic, liver, renal function, and blood lipid levels were all primary outcomes and were analyzed. The adverse events and related management were also recorded.

RESULTS

Sirolimus administration did not lead to deviations from normal growth ranges, but higher doses exhibited a positive association with Z-scores exceeding 2 SD in height, weight, and BMI. Transient elevations in red blood cell and white blood cell counts, along with hyperlipidemia, were primarily observed within the first year of treatment. Other measured parameters remained largely unchanged, displaying only weak correlations with drug use. Stomatitis is the most common adverse event (920/1738, 52.9%). In adult females, menstrual disorders were observed in 48.5% (112/217).

CONCLUSIONS

Sirolimus's long-term administration is not associated with adverse effects on children's physical growth pattern, nor significant alterations in hematopoietic, liver, renal function, or lipid levels. A potential dose-dependent influence on growth merits further exploration.

TRIAL REGISTRATION

Pediatric patients: Chinese clinical trial registry, No. ChiCTR-OOB-15,006,535. Adult patients: ClinicalTrials, No. NCT03193892.

Everolimus-Related Chylothorax: A Rare Case Report

Everolimus is an orally administered mechanistic target of rapamycin inhibitor in solid-organ transplant patients. In addition to the common adverse side effects of this treatment, such as hyperlipidemia, rash, stomatitis, anorexia, diarrhea, anemia, thrombocytopenia, and leukopenia, pulmonary toxicity is also an important adverse side effect. Although pulmonary toxicity due to everolimus has been reported mostly as pneumonitis, cases of pleural effusion due to everolimus have also been reported rarely. Chylothorax is defined as the accumulation of lymphatic fluid in the pleural space. It may develop secondary to trauma or malignancy. In this case report, we present a patient with chylothorax after everolimus treatment.

Does Lymphovenous Anastomosis Effect Mammalian Target of Rapamycin Inhibitor-associated Lymphedema Patients?

The mammalian target of rapamycin (mTOR) inhibitors are used to prevent organ transplant rejection and are preferred over other immunosuppressants due to its low nephrotoxicity. However, mTOR inhibitors have been associated with various adverse effects including lymphedema. Although rare in incidence, previously known treatments for mTOR inhibitor-induced lymphedema were limited to discontinuation of related drugs and complex disruptive therapy with variable results. In this article, three patients who developed lymphedema in their lower limbs after using mTOR inhibitors, including two bilateral and one unilateral case, were treated with physiologic surgery methods such as lymphovenous anastomosis (LVA) and lymph node transfer. The efficacy of the treatment was evaluated. In the three cases described, cessation of the drug did not lead to any reduction in edema. The use of LVA and lymph node transfer resulted in early reductions in volume but failed to sustain over time. All patients underwent secondary nonphysiologic surgery such as liposuction resulting in sustained improvement. This series presents the first physiologic approach to mTOR inhibitor-induced lymphedema. Although further study is warranted, the physiologic surgical options may have limited success and nonphysiologic options may offer better sustainable results.

Chronic Rapamycin administration via drinking water mitigates the pathological phenotype in a Krabbe disease mouse model through autophagy activation

Krabbe disease (KD) is a rare disorder arising from the deficiency of the lysosomal enzyme galactosylceramidase (GALC), leading to the accumulation of the cytotoxic metabolite psychosine (PSY) in the nervous system. This accumulation triggers demyelination and neurodegeneration, and despite ongoing research, the underlying pathogenic mechanisms remain incompletely understood, with no cure currently available. Previous studies from our lab revealed the involvement of autophagy dysfunctions in KD pathogenesis, showcasing p62-tagged protein aggregates in the brains of KD mice and heightened p62 levels in the KD sciatic nerve. We also demonstrated that the autophagy inducer Rapamycin (RAPA) can partially reinstate the wild type (WT) phenotype in KD primary cells by decreasing the number of p62 aggregates. In this study, we tested RAPA in the Twitcher (TWI) mouse, a spontaneous KD mouse model. We administered the drug ad libitum via drinking water (15 mg/L) starting from post-natal day (PND) 21-23. We longitudinally monitored the mouse motor performance through grip strength and rotarod tests, and a set of biochemical parameters related to the KD pathogenesis (i.e. autophagy markers expression, PSY accumulation, astrogliosis and myelination). Our findings demonstrate that RAPA significantly enhances motor functions at specific treatment time points and reduces astrogliosis in TWI brain, spinal cord, and sciatic nerves. Utilizing western blot and immunohistochemistry, we observed a decrease in p62 aggregates in TWI nervous tissues, corroborating our earlier in-vitro results. Moreover, RAPA treatment partially removes PSY in the spinal cord. In conclusion, our results advocate for considering RAPA as a supportive therapy for KD. Notably, as RAPA is already available in pharmaceutical formulations for clinical use, its potential for KD treatment can be rapidly evaluated in clinical trials.

Tetrahydropalmatine: Orchestrating survival - Regulating autophagy and apoptosis via the PI3K/AKT/mTOR pathway in perforator flaps

BACKGROUND

Introduced in clinical practice in 1989, perforator flaps are vital for tissue defect repair, but they are challenged by distal necrosis. Tetrahydropalmatine (THP) from celandine is renowned for its anti-inflammatory and analgesic effects. This study investigates THP's use in perforator flaps.

METHODS

Thirty rats were divided into a control group and four THP concentration groups, while seventy-eight rats were categorized as control, THP, THP combined with rapamycin (RAP), and RAP alone. We created 11 cm by 2.5 cm multi-regional perforator flaps on rat backs, assessing survival blood flow and extracting skin flap tissue for autophagy, oxidative stress, apoptosis, and angiogenesis markers.

RESULTS

The THP group exhibited significantly reduced distal necrosis, increased blood flow density, and survival area on the seventh day compared to controls. Immunohistochemistry and Western blot results demonstrated improved anti-oxidative stress and angiogenesis markers, along with decreased autophagy and apoptosis indicators. Combining THP with RAP diminished flap survival compared to THP alone. This was supported by protein expression changes in the PI3K-AKT-mTOR pathway.

CONCLUSION

THP enhances flap survival by modulating autophagy, reducing tissue edema, promoting angiogenesis, and mitigating apoptosis and oxidative stress. THP offers a potential strategy for enhancing multi-regional perforator flap survival through the PI3K/AKT/mTOR pathway. These findings highlight THP's promise in combatting perforator flap necrosis, uncovering a novel mechanism for its impact on flap survival.

Dysregulation of Lymphatic Endothelial VEGFR3 Signaling in Disease

Vascular endothelial growth factor (VEGF) receptor 3 (VEGFR3), a receptor tyrosine kinase encoded by the FLT4 gene, plays a significant role in the morphogenesis and maintenance of lymphatic vessels. Under both normal and pathologic conditions, VEGF-C and VEGF-D bind VEGFR3 on the surface of lymphatic endothelial cells (LECs) and induce lymphatic proliferation, migration, and survival by activating intracellular PI3K-Akt and MAPK-ERK signaling pathways. Impaired lymphatic function and VEGFR3 signaling has been linked with a myriad of commonly encountered clinical conditions. This review provides a brief overview of intracellular VEGFR3 signaling in LECs and explores examples of dysregulated VEGFR3 signaling in various disease states, including (1) lymphedema, (2) tumor growth and metastasis, (3) obesity and metabolic syndrome, (4) organ transplant rejection, and (5) autoimmune disorders. A more complete understanding of the molecular mechanisms underlying the lymphatic pathology of each disease will allow for the development of novel strategies to treat these chronic and often debilitating illnesses.

The emerging Janus face of SVEP1 in development and disease

Sushi, von Willebrand factor type A, EGF, and pentraxin domain containing 1 (SVEP1) is a large extracellular matrix protein that is also detected in circulation. Recent plasma proteomic and genomic studies have revealed a large number of associations between SVEP1 and human traits, particularly chronic disease. These include associations with cardiac death and disease, diabetes, platelet traits, glaucoma, dementia, and aging; many of these are causal. Animal models demonstrate that SVEP1 is critical in vascular development and disease, but its molecular and cellular mechanisms remain poorly defined. Future studies should aim to characterize these mechanisms and determine the diagnostic, prognostic, and therapeutic value of measuring or intervening on this enigmatic protein.

Indication for a Pneumocystis Prophylaxis Therapy in Patients with Vascular Anomalies Treated with PIK3/AKT/mTOR Pathway Inhibitors: Experts' Opinion and Systematic Review from the Literature

BACKGROUND

Vascular anomalies (VAs) are increasingly being treated with PI3K/AKT/mTOR pathway inhibitors. These drugs have immunosuppressive properties and thus theoretically overexpose patients to opportunistic infections, especially Pneumocystis jirovecii pneumonia (PJP). PJP prophylaxis use lacks consensus. We aimed to investigate the prevalence of PJP in patients receiving mTOR/PI3K/AKT inhibitors for VAs and determine any indication for pneumocystis prophylaxis in this population.

METHODS

The study was conducted in 2 parts: (1) we sent a survey to a panel of international experts of VAs asking about their use of pneumocystis prophylaxis drugs and (2) we performed a systematic review of the literature of all published cases of patients receiving these drugs for VA to estimate the prevalence of PJP in this population.

RESULTS

Answers from 68 experts were analyzed: 21 (30.9%) answered they always add PJP prophylaxis when prescribing mTOR inhibitors, 20 (29.4%) case-by-case, and 27 (39.7%) never. For the systematic review, among 3,053 reports screened, 217 were included involving 1,189 patients (1,143 received sirolimus, 38 everolimus, 4 alpelisib, 4 miransertib). Among the 1,189 cases, 2 (0.2%) PJP were reported: one under sirolimus and one under everolimus. Thus, the prevalence of PJP was estimated at 0.88 cases/1,000 patients under sirolimus (95% CI: -0.84 to 2.59) and 26.31 cases/1,000 under everolimus (95% CI: -24.58 to 77.18). Patients with PJP never received prophylaxis drugs. We found no PJP cases under alpelisib and miransertib. PJP prophylaxis was given in 218 (18.3%) cases, more frequently for children (91.3 vs. 77.2% in the non-prophylaxis group, p = 0.012), mostly trimethoprim-sulfamethoxazole (186 patients, 85.3%).

CONCLUSION

Our study shows that even if PJP is a rare event, it may occur in patients with VAs treated with an mTOR inhibitor. Although our results cannot allow for revising guidelines, prophylaxis with TMP-SMX might be appropriate for a subgroup of patients with risk factors for PJP.

Modeling lymphangiogenesis: Pairing in vitro and in vivo metrics

Lymphangiogenesis is the mechanism by which the lymphatic system develops and expands new vessels facilitating fluid drainage and immune cell trafficking. Models to study lymphangiogenesis are necessary for a better understanding of the underlying mechanisms and to identify or test new therapeutic agents that target lymphangiogenesis. Across the lymphatic literature, multiple models have been developed to study lymphangiogenesis in vitro and in vivo. In vitro, lymphangiogenesis can be modeled with varying complexity, from monolayers to hydrogels to explants, with common metrics for characterizing proliferation, migration, and sprouting of lymphatic endothelial cells (LECs) and vessels. In comparison, in vivo models of lymphangiogenesis often use genetically modified zebrafish and mice, with in situ mouse models in the ear, cornea, hind leg, and tail. In vivo metrics, such as activation of LECs, number of new lymphatic vessels, and sprouting, mirror those most used in vitro, with the addition of lymphatic vessel hyperplasia and drainage. The impacts of lymphangiogenesis vary by context of tissue and pathology. Therapeutic targeting of lymphangiogenesis can have paradoxical effects depending on the pathology including lymphedema, cancer, organ transplant, and inflammation. In this review, we describe and compare lymphangiogenic outcomes and metrics between in vitro and in vivo studies, specifically reviewing only those publications in which both testing formats are used. We find that in vitro studies correlate well with in vivo in wound healing and development, but not in the reproductive tract or the complex tumor microenvironment. Considerations for improving in vitro models are to increase complexity with perfusable microfluidic devices, co-cultures with tissue-specific support cells, the inclusion of fluid flow, and pairing in vitro models of differing complexities. We believe that these changes would strengthen the correlation between in vitro and in vivo outcomes, giving more insight into lymphangiogenesis in healthy and pathological states.

Development of hemodynamically relevant acquired arterio-venous fistulae in patients with venous malformations

BACKGROUND

Venous malformations tend to retain their slow-flow behavior, even in progressive disease or regression following therapy.

OBJECTIVE

The aim of this study is to analyze the development of acquired hemodynamic relevant arterio-venous fistulae in patients with slow-flow malformations.

METHODS

This study is a retrospective analysis based on a consecutive local registry at a tertiary care Interdisciplinary Center for Vascular Anomalies. Patients with venous malformations and development of secondary arterio-venous fistulae were included. Indications for therapy of the vascular malformation were based on patients' symptoms and complications. The following endpoints were of clinical interest and were assessed: origin of development of arteriovenous fistula, development of secondary comorbidities as a result of the vascular malformation. For analysis we focused on descriptive statistics.

RESULTS

Out of 1213 consecutive patients with vascular malformations, in 6 patients perfusion changed from slow flow to arterio-venous fast-flow patterns. Four patients developed the fistula after local trauma in the area of the malformation, the other 2 patients developed the fistula due to progression of the disease and recurrent thrombophlebitis. These 2 patients had no trauma or interventions at the time of arterio-venous fistula development.

CONCLUSIONS

Acquired arterio-venous fast-flow fistula in patients with slow flow vascular malformation is very rare and might be a result of local trauma or the progression of the disease with recurrent thrombophlebitis. Specific evidence-based treatment options for these patients do not exist.

Lymphocele in Kidney Transplantation: A Comparison of Ligation and Non-ligation Technique of Iliac Lymphatic Dissection

BACKGROUND

To compare the incidence of lymphocele in kidney recipients following 2 lymphatic vessel division techniques: ligation and non-ligation.

METHODS

Retrospective reviews of the records of 402 patients with end-stage renal disease who underwent kidney transplantation from April 2015 to December 2019 at Siriraj Hospital.

RESULTS

Four hundred two patients were included in the study: 54.9% of the patients were male, and the patient's mean age was 41 years. There were 25.1% and 74.9% that received kidney grafts from living and deceased donors, respectively. The preoperative renal replacement therapies were 83.3% hemodialysis, 12.9% peritoneal dialysis, and 3.7% preemptive transplantation. Two hundred forty-nine patients received lymphatic division with the ligation technique and 153 patients received the non-ligation. Lymphoceles were found in 31 cases (7.7%). Lymphocele occurrence in the ligation group was lower than in the non-ligation group: 5.2% compared to 11.8% (P value = .017). There were 22.6% of lymphoceles that had a spontaneous resolution with no treatment.

DISCUSSION

The ligation of iliac lymphatic vessels during division reduced the incidence of lymphoceles non-ligation.

Cardiovascular effects of immunosuppression agents

Immunosuppressive medications are widely used to treat patients with neoplasms, autoimmune conditions and solid organ transplants. Key drug classes, namely calcineurin inhibitors, mammalian target of rapamycin (mTOR) inhibitors, and purine synthesis inhibitors, have direct effects on the structure and function of the heart and vascular system. In the heart, immunosuppressive agents modulate cardiac hypertrophy, mitochondrial function, and arrhythmia risk, while in vasculature, they influence vessel remodeling, circulating lipids, and blood pressure. The aim of this review is to present the preclinical and clinical literature examining the cardiovascular effects of immunosuppressive agents, with a specific focus on cyclosporine, tacrolimus, sirolimus, everolimus, mycophenolate, and azathioprine.

How we approach the use of sirolimus and new agents: Medical therapy to treat vascular anomalies

Vascular anomalies (VAs) are a heterogeneous group of primarily congenital tumors and malformations. The International Society for the Study of Vascular Anomalies (ISSVA) has developed a standard classification of these disorders, creating a uniform approach to their diagnosis. Recent discoveries evaluating the genetic causes of VAs have revealed that they are due to mutations in cancer pathways, including the PI3K/AKT/mTOR and RAS/MAPK/MEK pathways. These discoveries have led to improved phenotype-genotype correlation and have expanded medical therapy for this group of unique disorders.

Combination mTOR and SHP2 inhibitor treatment of lymphatic malformation endothelial cells

Mammalian target of rapamycin (mTOR) inhibitors are clinically effective at treating some complex lymphatic malformations (LM). The mTOR inhibitor rapamycin blocks the phosphoinositide 3-kinase (PI3K) pathway, which is commonly mutated in this condition. Although rapamycin is effective at controlling symptoms of LM, treatment courses are long, not all LMs respond to treatment, and many patients relapse after treatment has stopped. Concurrent rat sarcoma virus (RAS) pathway abnormalities have been identified in LM, which may limit the effectiveness of rapamycin. Protein tyrosine phosphatase-2 (SHP2) controls the RAS pathway upstream, and SHP2 inhibitors are being investigated for treatment of various tumors. The objective of this study was to determine the impact of SHP2 inhibition in combination with rapamycin on LM growth in vitro. Using primary patient cells isolated from a surgically resected LM, we found that combination treatment with rapamycin and the SHP2 inhibitor SHP099 caused a synergistic reduction in cell growth, migration and lymphangiogenesis. These results suggest that combination treatment targeting the PI3K and RAS signaling pathways may result in effective treatment of LMs of the head and neck.

Liver Transplant Oncology: Towards Dynamic Tumor-Biology-Oriented Patient Selection

While liver transplantation was initially considered as a curative treatment modality only for hepatocellular carcinoma, the indication has been increasingly extended to other tumor entities over recent years, most recently to the treatment of non-resectable colorectal liver metastases. Although oncologic outcomes after liver transplantation (LT) are consistently good, organ shortage forces stringent selection of suitable candidates. Dynamic criteria based on tumor biology fulfill the prerequisite of an individual oncological prediction better than traditional morphometric criteria based on tumor burden. The availability of specific (neo-)adjuvant therapies and customized modern immunosuppression may further contribute to favorable post-transplantation outcomes on the one hand and simultaneously open the path to LT as a curative option for advanced stages of tumor patients. Herein, we provide an overview of the oncological LT indications, the selection process, and expected oncological outcome after LT.

A precision medicine approach to hereditary hemorrhagic telangiectasia and complex vascular anomalies

Vascular anomalies represent a diverse group of disorders classified broadly as malformations or tumors and include the second most common hereditary bleeding disorder worldwide, hereditary hemorrhagic telangiectasia (HHT). Patients with HHT and other vascular anomalies suffer morbid consequences of these diseases, including bleeding, thrombosis, anemia, localized intravascular coagulation, tissue overgrowth, infections, and other complications. The International Society for the Study of Vascular Anomalies (ISSVA) has developed a standard classification of these disorders, creating a uniform approach to their diagnosis, and the treatments for vascular anomalies are rapidly evolving. Recent discoveries have elucidated the molecular basis of a number of common and uncommon vascular anomalies. HHT occurs due to mutations in the transforming growth factor beta (TGF-β) pathway, resulting in vascular endothelial growth factor excess. Complex vascular anomalies including Klippel-Trénaunay syndrome (KTS) and arteriovenous malformation (AVM) may occur due to mutations in the PI3K/AKT/mTOR and RAS/MAPK/MEK pathways. The discovery of the pathophysiologic mechanisms driving these diseases has led to improved phenotype-genotype correlation and the opportunity to target molecular pathways with medical therapies. Therefore, targeted agents have quickly become a standard of care in the treatment of vascular disorders (particularly HHT). Herein, we provide a case-based approach to the use of antiangiogenic therapies including bevacizumab and pazopanib for the treatment of bleeding in HHT and the use of mammalian target of rapamycin (sirolimus), PIK3CA (alpelisib), and MEK (trametinib) inhibitors in the treatment of complex vascular anomalies.

Transplant Onconephrology in Patients With Kidney Transplants

Cancer is a leading cause of death in patients with kidney transplantation. Patients with kidney transplants are 10- to 200-times more likely to develop cancers after transplant than the general population, depending on the cancer type. Recent advances in cancer therapies have dramatically improved survival outcomes; however, patients with kidney transplants face unique challenges of immunosuppression management, cancer screening, and recurrence of cancer after transplant. Patients with a history of cancer tend to be excluded from transplant candidacy or are required to have long cancer-free wait time before wait-listing. The strategy of pretransplant wait time management may need to be revisited as cancer therapies improve, which is most applicable to patients with a history of multiple myeloma. In this review, we discuss several important topics in transplant onconephrology: the current recommendations for pretransplant wait times for transplant candidates with cancer histories, cancer screening post-transplant, post-transplant lymphoproliferative disorder, strategies for transplant patients with a history of multiple myeloma, and novel therapies for patients with post-transplant malignancies. With emerging novel cancer treatments, it is critical to have multidisciplinary discussions involving patients, caregivers, transplant nephrologists, and oncologists to achieve patient-oriented goals.

Mammalian Target of Rapamycin Inhibitors and Wound Healing Complications in Kidney Transplantation: Old Myths and New Realities

Mammalian target of rapamycin inhibitors (mTOR-I) lacks nephrotoxicity, has antineoplastic effects, and reduces viral infections in kidney transplant recipients. Earlier studies reported a significant incidence of wound healing complications and lymphocele. This resulted in the uncomfortable willingness of transplant clinicians to use these agents in the immediate posttransplant period. As evidence and experience evolved over time, much useful information became available about the optimal use of these agents. Understandably, mTOR-I effects wound healing through their antiproliferative properties. However, there are a lot of other immunological and nonimmunological factors which can also contribute to wound healing complications. These risk factors include obesity, uremia, increasing age, diabetes, smoking, alcoholism, and protein-energy malnutrition. Except for age, the rest of all these risk factors are modifiable. At the same time, mycophenolic acid derivatives, steroids, and antithymocyte globulin (ATG) have also been implicated in wound healing complications. A lot has been learnt about the optimal dose of mTOR-I and their trough levels, its combinations with other immunosuppressive medications, and patients' profile, enabling clinicians to use these agents appropriately for maximum benefits. Recent randomized control trials have further increased the confidence of clinicians to use these agents in immediate posttransplant periods.

Towards a better treatment of patients with vascular malformations: certified interdisciplinary centers are mandatory

BACKGROUND

Vascular anomalies are orphan diseases that occur in all age groups and range from purely aesthetic to potentially life-threatening conditions. This thesis paper outlines the typical conferring problems in patient management and possible structural solutions for a better patient treatment in the future.

METHODS

A multi-perspective author panel consisting of key stakeholders from the German Interdisciplinary Society of Vascular Anomalies and the German Society for Surgery defined problem areas and possible solutions including quality indicators as criteria for certified interdisciplinary Vascular Anomalies Centers (VAC).

RESULTS

According to the literature available, clearly defined nomenclature and nosological entities often remain unused in this field, and consented diagnostic and therapeutic evidence is rare. Expert opinions dominate and in some cases lead to disparate recommendations. Typical patient problems arise from this situation, exemplified in patient vignettes. Centralized and standardized patient treatment in interdisciplinary VAC may be a solution to this problem. These centers should agree on a set of general principles and quality indicators with an additional minimum set of structural and procedural criteria.

DISCUSSION

The present position paper outlines perspectives for implementing certified interdisciplinary VAC. There is a need for a comprehensive nomenclature, access to interdisciplinary treatment centers, more scientific evidence, and further education in this rare group of diseases.

CONCLUSION

Use of scientifically sound and patient-relevant criteria for certifying the interdisciplinary quality of VAC is expected to improve health care in Germany.

Optimization of Initial Dose Regimen for Sirolimus in Pediatric Patients With Lymphangioma

Sirolimus is an effective oral treatment for pediatric patients with lymphangioma. The present clinical study in 15 children (0.12–16.39 years of age) examines the effects of underlying factors on sirolimus concentrations through application of a population pharmacokinetic model. Using Monte Carlo simulation, an initial dose regimen for sirolimus in pediatric patients with lymphangioma is presented. It is found that the lower the body weight, the higher the clearance rate and sirolimus clearances are 0.31–0.17 L/h/kg in pediatric patients with lymphangioma whose weights are 5–60 kg, respectively. The doses of sirolimus, 0.07, 0.06, 0.05 mg/kg/day are recommended for weights of 5–10, 10–24.5 and 24.5–60 kg in children with lymphangioma. This study is the first to establish a population pharmacokinetic model for sirolimus and to recommend initial doses in pediatric patients with lymphangioma. Large scale, prospective studies are needed in the future.

Sirolimus (Rapamycin) for Slow-Flow Malformations in Children: The Observational-Phase Randomized Clinical PERFORMUS Trial

Importance

Sirolimus is increasingly being used to treat various vascular anomalies, although evidence of its efficacy is lacking.

Objective

To assess the efficacy and safety of sirolimus for children with slow-flow vascular malformations to better delineate the indications for treatment.

Design, Setting and Participants

This multicenter, open-label, observational-phase randomized clinical trial included 59 children aged 6 to 18 years with a slow-flow vascular malformation who were recruited between September 28, 2015, and March 22, 2018, in 11 French tertiary hospital centers. Statistical analysis was performed on an intent-to-treat basis from December 4, 2019, to November 10, 2020.

Interventions

Patients underwent an observational period, then switched to an interventional period when they received oral sirolimus (target serum levels, 4-12 ng/mL). The switch time was randomized from month 4 to month 8, and the whole study period lasted 12 months for each patient.

Main Outcomes and Measures

The primary outcome was change in the volume of vascular malformations detected on magnetic resonance imaging scan (with centralized interpretation) per unit of time (ie, between the interventional period and the observational period). Secondary outcomes included subjective end points: pain, bleeding, oozing, quality of life, and safety.

Results

Among the participants (35 girls [59.3%]; mean [SD] age, 11.6 [3.8] years), 22 (37.3%) had a pure venous malformation, 18 (30.5%) had a cystic lymphatic malformation, and 19 (32.2%) had a combined malformation, including syndromic forms. Variations in the volume of vascular malformations detected on magnetic resonance imaging scans associated with the duration period were not overall significantly different between the interventional period and the observational period (all vascular malformations: mean [SD] difference, -0.001 [0.007]; venous malformations: mean [SD] difference, 0.001 [0.004]; combined malformations: mean [SD] difference, 0.001 [0.009]). However, a significant decrease in volume was observed for children with pure lymphatic malformations (mean [SD] difference, -0.005 [0.005]). Overall, sirolimus had positive effects on pain, especially for combined malformations, and on bleeding, oozing, self-assessed efficacy, and quality of life. During sirolimus treatment, 56 patients experienced 231 adverse events (5 serious adverse events, none life-threatening). The most frequent adverse event was an oral ulcer (29 patients [49.2%]).

Conclusions and Relevance

This observational-phase randomized clinical trial allows for clarifying the goals of patients and families when starting sirolimus therapy for children older than 6 years. Pure lymphatic malformations seem to be the best indication for sirolimus therapy because evidence of decreasing lymphatic malformation volume per unit of time, oozing, and bleeding and increasing quality of life was found. In combined malformations, sirolimus significantly reduced pain, oozing, and bleeding. Benefits seemed lower for pure venous malformations than for the 2 other subgroups, also based on symptoms.

Trial Registration

ClinicalTrials.gov Identifier: NCT02509468; clinicaltrialsregister.eu Identifier: 2015-001096-43.

Intermittent Administration Regimen of Sirolimus for Refractory Cervicofacial Lymphatic Malformation

BACKGROUND

The cervicofacial lymphatic malformations (LMs) often have poor outcomes due to their microcystic component and diffuse infiltration. Mostly, traditional treatments are inadequate for these refractory cases. Recent researches have shown that sirolimus is effective in the treatment of complicated LMs, however, there is still no standard strategy.

OBJECTIVE

To evaluate the efficacy and safety of intermittent oral sirolimus in treating refractory cervicofacial LMs as a second-line treatment.

METHODS

Fifteen pediatric patients of refractory cervicofacial LMs were retrospectively analyzed in this study. All the cases had received traditional therapy before, but could not completely control the symptoms and eliminate lesions. As a remedy, sirolimus was then proceeded with an intermittent administration regimen, that is 3 continuous months as a course and started the next course after 1 month interval. The clinical characteristics, imaging data of patients, the changes in the signs and symptoms observed, and associated adverse effects were collected and analyzed.

RESULTS

The patients initiated sirolimus therapy at the average age of 2.3 years (range 28 days-8 years 9 months). At the end point of the study, 2 patients remained on sirolimus in continuous courses of treatment. Of 13 patients who withdrawn therapy, 4 had restarted due to recurrence of symptoms and re-expansion of LMs. All patients demonstrated reduction in residual LMs and complete disappearance of symptoms during treatment, and 2 patients with complete resolution on imaging. Toxicity was tolerant in this series. There was no patient develop opportunistic or systemic bacterial infection.

CONCLUSIONS

Sirolimus is commended as a second-line treatment to treat intractable cervicofacial LMs after failure of traditional therapy. The intermittent administration regimen is efficacious to completely control symptoms and partially reduce residual lesions with good tolerance and limited side effects.

A New Experimental Lymphedema Model: Reevaluating the Efficacy of Rat Models and Their Clinical Translation for Chronic Lymphedema Studies

BACKGROUND

Our aim was to create a new rodent hind limb lymphedema model lacking the fibrosis effect induced by radiotherapy and subjected to the inhibition of lymphangiogenesis via sirolimus (rapamycin) to maintain a chronic lymphedema model and investigate its reliability for human treatment modalities.

METHODS

Forty-two Sprague-Dawley rats were randomly assigned to 7 groups: (1) surgery control, (2) vehicle-surgery control, (3) vehicle control, (4) rapamycin control, (5) surgery with 1 mg/kg per day rapamycin, (6) surgery with 1.5 mg/kg per day rapamycin, and (7) surgery with 2 mg/kg per day rapamycin. All surgeries were performed on the right hind limbs, with the left hind limbs also considered as a control. The drug and its solvent were administered daily into the relevant groups intraperiteonally. The presence of lymphedema was investigated by weekly limb circumference measurements, microcomputed tomography, fluorescence lymphography using indocyanine green dye, and microscopic evaluation at the end of the sixth week to determine any histological changes in the hind limbs.

RESULTS

In group 1, lymphedema was observed for 2 weeks (P = 0.032), whereas in groups 5, 6, and 7, lymphedema lasted for 3 weeks (P < 0.05.) Fluorescence using indocyanine green revealed that the edema was totally resolved after 6 weeks of surgery by a well-developed superficial lymphatic organization instead of the normal distinct vessel structure. Histologically, groups 1, 5, 5, and 7 demonstrated a significant increase in both the number of macrophages (P < 0.001) and newly formed lymphatic vessels in the right side surgically treated hind limb (P < 0.05).

CONCLUSIONS

Despite the extreme surgical destruction and lymphangiogenesis inhibition in the rat model, the sustained lymphedema did not last >3 weeks. Because of the rapid neolymphangiogenesis in murines and a different wound healing mechanism, they should not be considered as an appropriate model for research on human lymphedema in first place.

Drug-induced peripheral oedema: An aetiology-based review

Many drugs are responsible, through different mechanisms, for peripheral oedema. Severity is highly variable, ranging from slight oedema of the lower limbs to anasarca pictures as in the capillary leak syndrome. Although most often noninflammatory and bilateral, some drugs are associated with peripheral oedema that is readily erythematous (eg, pemetrexed) or unilateral (eg, sirolimus). Thus, drug-induced peripheral oedema is underrecognized and misdiagnosed, frequently leading to a prescribing cascade. Four main mechanisms are involved, namely precapillary arteriolar vasodilation (vasodilatory oedema), sodium/water retention (renal oedema), lymphatic insufficiency (lymphedema) and increased capillary permeability (permeability oedema). The underlying mechanism has significant impact on treatment efficacy. The purpose of this review is to provide a comprehensive analysis of the main causative drugs by illustrating each pathophysiological mechanism and their management through an example of a drug.

Management of lymphatic vascular malformations: A systematic review of the literature

OBJECTIVE

Lymphatic malformations (LM) are common congenital vascular lesions, most often diagnosed at birth. They deform local anatomy and can be life-threatening if they compress the aerodigestive tract or other vital structures. Significant progress has been made in the treatment of LMs in the past 20 years. We conducted a systematic review of the literature on the management of LMs.

METHODS

On September 21, 2020, we searched PubMed/MEDLINE for studies published from 2000 to 2020 reporting outcomes of invasive and pharmacologic treatment of LMs.

RESULTS

A total of 251 studies met the eligibility criteria. Surgery has continued to be a mainstay in the management of LMs, especially in the treatment of microcystic and mixed lesions. Sclerotherapy has emerged as a first-line treatment of macrocystic LMs and as an adjunctive therapy used in combination with surgery for other lesions. Sirolimus, a strong inhibitor of mTOR (mechanistic target of rapamycin), has shown tremendous promise in the treatment of LMs, as both an oral and a topical agent. Recent investigations have shown the potential of targeted small molecule modulators of cellular pathways in the treatment of LMs.

CONCLUSIONS

Multiple invasive and pharmacologic therapies have been shown to be effective in the treatment of LMs. Future research should focus on rigorous, prospective comparisons of these treatment modalities.

Characteristics of Lymphedema in Patients Treated with Mammalian Target of Rapamycin Inhibitors

Purpose: To investigate the characteristics of lymphedema in patients treated with mammalian target of rapamycin (mTOR) inhibitors and delineate complex decongestive therapy (CDT) outcomes. Methods and Results: We retrospectively analyzed 24 patients with mTOR inhibitor-induced lymphedema and 7 lymphedema patients (control) not treated with mTOR inhibitors, who visited the lymphedema clinic of the department of rehabilitation medicine from March 2016 to December 2019. We comprehensively reviewed clinical features, medication history, associated diseases, lymphoscintigraphy, lower extremity computed tomography venography (LE CTV), and the effect of CDT. By using ImageJ program, we measured the cross-sectional area (CSA) of muscle and subcutaneous fat of mid-thigh image in LE CTV and compared them to a control group not treated with mTOR inhibitors. Seventeen patients on sirolimus and seven patients on everolimus were included, with an approximately equal distribution of stages 2 and 3 lymphedema, and most with pitting edema. Ten patients had breast or gynecological cancer and underwent lymph node dissection. Lymphedema developed after mTOR inhibitor initiation, not postoperatively. Lymphoscintigraphy revealed decreased lymph node uptake and dermal backflow. LE CTV revealed subcutaneous honeycomb-shaped trabecular areas in the affected limbs of seven patients. Patients treated with mTOR inhibitors had a larger mean subcutaneous fat CSA and a smaller mean muscular CSA than controls. Lymphedema improved or remained unchanged after initial CDT. Daily CDT adequately controlled 11 cases, but exacerbation occurred in 5 of 7 poorly compliant patients, and cellulitis occurred in 6 patients. Conclusion: Physicians should identify mTOR inhibitor-related lymphedema early and discuss medication alternatives and CDT with patients.

Vascular anomalies: Classification and management

Vascular anomalies are broadly classified into two major categories: vascular tumors and vascular malformations. Most vascular anomalies are caused by sporadic mosaic gene mutations, and recent genetic studies have advanced our understanding of the molecular pathways involved in their pathogenesis. These findings have suggested new therapeutic approaches to vascular anomalies, focusing on their pathogenetic mechanism. This chapter seeks to integrate an improved molecular understanding within the updated classification system of the International Society for Study of Vascular Anomalies. We emphasize the genetic, radiologic, and interventional aspects of diagnosis and management in hopes of allowing improved multidisciplinary collaboration surrounding these complex and interesting anomalies.

c-Myc promotes lymphatic metastasis of pancreatic neuroendocrine tumor through VEGFC upregulation

Pancreatic neuroendocrine tumor (pNET) is a pancreatic neoplasm with neuroendocrine differentiation. pNET in early stage can be treated with surgical resection with long‐term survival, whereas the prognosis of pNET with locoregional or distant metastasis is relatively poor. Lymphangiogenesis is essential for tumor metastasis via the lymphatic system and may overhead distant metastasis. c‐Myc overexpression is involved in tumorigenesis. The role of c‐Myc in lymphangiogenesis is unclear. In this study, we evaluated the mechanism and effect of c‐Myc on lymphangiogenesis of pNET via interaction of lymphatic endothelial cells (LECs) and pNET cells. Lymph node metastasis was evaluated in pNET xenograft mice. Potential target agents to inhibit lymph node metastasis were evaluated in an animal model. We found that vascular endothelial growth factor C (VEGFC) expression and secretion was increased in pNET cell lines with c‐Myc overexpression. c‐Myc transcriptionally upregulates VEGFC expression and the secretion of pNET cells by directly binding to the E‐box of the VEGFC promoter and enhances VEGF receptor 3 phosphorylation and the tube formation of LECs. c‐Myc overexpression is associated with lymph node metastasis in pNET xenograft mice. Combinational treatment with an mTOR inhibitor and c‐Myc inhibitor or VEGFC‐neutralizing chimera protein reduced lymph node metastasis in the mice with c‐Myc overexpression. The mTOR inhibitor acts on lymphangiogenesis by reducing VEGFC expression in pNET cells and inhibiting the tube formation of LECs. In conclusion, mTOR and c‐Myc are important for lymphangiogenesis of pNET and are potential therapeutic targets for prevention and treatment of lymph node metastasis in pNET.

Everolimus-related unilateral abdominal lymphedema in a renal cancer patient: A case report

RATIONALE

Unilateral manifestation of lymphedema during everolimus therapy has been described only rarely, mostly in transplant recipients.

PATIENT CONCERNS

We report the first case of a patient who developed unilateral abdominal lymphedema, during a short period of everolimus treatment for renal cancer.

DIAGNOSIS

The abdominal asymmetry occurred only on the right side of the abdomen, neither ultrasound nor CT scan detected ascites but showed enlargement of the abdominal wall. The Naranjo Adverse Drug Reaction Probability scale was evaluated, in this case, a score of 6 indicated a probable adverse reaction to everolimus.

INTERVENTIONS

Discontinuation of everolimus therapy led to immediate alleviation and reduction of the lymphedema, with worsening once again after initiating retreatment with everolimus at a reduced dose.

OUTCOMES

The patient's lymphedema recovered after discontinuation of everolimus.

LESSONS

This rare case demonstrates the importance of the selection of mammalian target of rapamycin inhibitors using caution, especially for patients with a high risk of developing lymphedema.

Properties of rapamycin solid lipid nanoparticles for lymphatic access through the lungs & part I: the effect of size

Background: Lymphangioleiomyomatosis (LAM) is characterized by growth of smooth muscle-like cells in the lungs that spread to other organs via lymphatic vessels. Current oral rapamycin treatment is limited by low bioavailability of approximately 15%. Aim: The effect of inhaled rapamycin solid lipid nanoparticles (Rapa-SLNs) size on its penetration through the lymphatics. Method: Three Rapa-SLN formulations (200-1000 nm) were produced and assessed for particle characteristics and further for toxicity and performance in vitro. Results: Rapa-SLNs of 200 nm inhibited proliferation in TSC2-negative mouse embryonic fibroblast cells and penetrated the respiratory epithelium and lymphatic endothelium significantly faster compared with free rapamycin and larger Rapa-SLNs. Conclusion: Rapa-SLN approximately 200 nm allows efficient entry of rapamycin into the lymphatic system and is therefore a promising treatment for LAM patients.

Properties of rapamycin solid lipid nanoparticles for lymphatic access through the lungs & part II: the effect of nanoparticle charge

Aim: Lymphangioleiomyomatosis is characterized by smooth muscle-like cells in the lungs that spread to other organs via lymphatic vessels. Oral rapamycin is restricted by low bioavailability approximately 15%. The aim of the present study is to systematically investigate the effect of inhaled rapamycin solid lipid nanoparticles (Rapa-SLN) surface charge on efficacy and penetration into the lymphatics. Materials & methods: Rapa-SLN formulations with different charge: neutral, positive and negative, were produced and assessed for their physicochemical particle characteristics and efficacy in vitro. Results: Negative Rapa-SLNs were significantly faster at entering the lymphatic endothelium and more potent at inhibiting lymphanigiogenesis compared with neutral and positive Rapa-SLNs. Conclusion: Negative Rapa-SLNs showed efficient lymphatic access and should therefore be investigated further as a treatment for targeting extrapulmonary lymphangioleiomyomatosis.

Lymphatic vessels in solid organ transplantation and immunobiology

With the recent advances in our understanding of the function and biology of the lymphatic vascular system, it is clear that the lymphatic system plays an integral role in physiology, and in pathological settings, may contribute to either enhance or repress inflammation and disease progression. Inflammation is central to both acute and chronic rejection in the context of solid organ transplantation, and emerging evidence suggests the lymphatic system plays a key role in shaping outcomes. The goals of this review are to highlight and contextualize the roles of lymphatic vessels and lymphangiogenesis in immunobiology, the impact immunosuppressive therapies have on the lymphatic system and emerging evidence of organ-specific heterogeneity of lymphatic vessels in the context of solid organ transplantation.

Beyond a Passive Conduit: Implications of Lymphatic Biology for Kidney Diseases

The kidney contains a network of lymphatic vessels that clear fluid, small molecules, and cells from the renal interstitium. Through modulating immune responses and via crosstalk with surrounding renal cells, lymphatic vessels have been implicated in the progression and maintenance of kidney disease. In this Review, we provide an overview of the development, structure, and function of lymphatic vessels in the healthy adult kidney. We then highlight the contributions of lymphatic vessels to multiple forms of renal pathology, emphasizing CKD, transplant rejection, and polycystic kidney disease and discuss strategies to target renal lymphatics using genetic and pharmacologic approaches. Overall, we argue the case for lymphatics playing a fundamental role in renal physiology and pathology and treatments modulating these vessels having therapeutic potential across the spectrum of kidney disease.

Rapamycin treatment maintains developmental potential of oocytes in mice and follicle reserve in human cortical fragments grafted into immune-deficient mice

The ovarian follicle pool size is limited; it decreases with age and following germ cell-damaging chemo- or radiation therapies. Due to a trend of delaying child-bearing age in the modern society, it is important to investigate the possibility to maintain the follicle reserve for middle-aged women and cancer-bearing patients subject to therapies. Earlier studies demonstrated the important role of the mammalian targets of the rapamycin (MTOR) signaling pathway in the activation of primordial follicles and suggested that treatment with the MTOR inhibitor rapamycin could maintain the follicle pool in rodents. Here, we confirmed the ability of rapamycin treatment for 3 weeks to suppress primordial follicle development and to maintain follicle pool size in mice. We further demonstrated that the developmental potential of oocytes was not affected by rapamycin treatment and the effect of rapamycin to decrease initial follicle recruitment is reversible. Using human ovarian cortical fragments grafted into immune-deficient mice, we demonstrated the ability of rapamycin to suppress follicle growth from the primordial stage. Our studies provide the basis for further studies on the possibility of using MTOR inhibitors to maintain follicle reserve in middle-aged women and cancer patients before/during germ cell-damaging therapies.

Sirolimus and mTOR Inhibitors: A Review of Side Effects and Specific Management in Solid Organ Transplantation

Inhibitors of mechanistic target of rapamycin (mTOR inhibitors) are used as antiproliferative immunosuppressive drugs and have many clinical applications in various drug combinations. Experience in transplantation studies has been gained regarding the side effect profile of these drugs and the potential benefits and limitations compared with other immunosuppressive agents. This article reviews the adverse effects of mTOR inhibitors in solid organ transplantation, with special attention given to mechanisms hypothesized to cause adverse events and their management strategies.

Successful treatment of diffuse pulmonary lymphangiomatosis with sirolimus

Diffuse pulmonary lymphangiomatosis (DPL) is a rare disease characterized by uncontrolled proliferation of anastomosing lymphatic channels in the lungs, pleura and mediastinum. Several palliative treatment options have been suggested for this condition, such as surgical interventions, radiotherapy and systemic medications. However, the existing treatment modalities yield inconsistent results, and their use is often limited by toxic side effects. The aim of this case report is to demonstrate the diagnostic challenges of a rare disease and improvement in the condition of a DPL patient treated with sirolimus. A 27-year-old man presented to the pulmonologist with exertional dyspnea, chronic cough and intermittent hemoptysis. Upon medical investigation, a chest computed tomography (CT) scan revealed soft tissue masses infiltrating the mediastinum and bilateral interlobular septal thickening. A surgical biopsy was performed, and pathological tissue analysis showed findings consistent with the diagnosis of DPL. Treatment with sirolimus was initiated, maintaining trough concentrations between 10 and 15 ng/ml. At 21 months of treatment, the patient reported reduced symptoms of cough and dyspnea. A CT scan showed decreased interstitial thickening and reduced infiltrations in the mediastinum. Moreover, pulmonary function tests revealed a significant increase in FEV1 and FVC. The authors believe this is the first article reporting pulmonary function improvement in an adult DPL patient treated with sirolimus. Therefore, sirolimus therapy should be considered for DPL patients as it may be effective in improving their condition and preventing disease progression.

Immunohistochemical Analysis of mTOR Pathway-Related Proteins in Kaposiform Hemangioendothelioma

BACKGROUND

Mammalian target of rapamycin (mTOR) inhibitors have been shown to have excellent effects in the management of kaposiform hemangioendothelioma (KHE); however, the mechanism of action is unclear. This study identified the expressions of mTOR pathway-related proteins in different vascular tumors to provide insight into the pathogenesis of KHE.

METHODS

We retrospectively reviewed the pathologic specimens of 30 patients (KHE, 15; tufted angioma [TA], 5; infantile hemangioma [IH], 5; and lymphatic malformation [LM], 5). The immunohistochemical expression of mTOR-related proteins tuberous sclerosis complex 2 (TSC2), phosphatase and tensin homologue (PTEN), phosphorylated eukaryotic translation initiation factor 4E binding protein 1 (p-4EBP1), phosphorylated mTOR (p-mTOR), and phosphorylated ribosomal protein S6 kinase B1 (p-P70S6K) were analyzed using Image-Pro Plus software. KHE had the following pattern of expression in the spindle vascular endothelial cells: TSC2 (-); PTEN (-); p-4EBP1 (+); p-mTOR (+); and p-P70S6K (+).

RESULTS

All 3 patients treated with sirolimus had good responses. The TA results were similar to KHE with no significant differences (p-4EBP1: p = 0.0687; p-mTOR: p = 0.0832). The expressions of TSC2, PTEN, p-4EBP1, p-mTOR, and p-P70S6K were negative or weakly positive in IH with a statistically significant difference compared to KHE (p-4EBP1: p < 0.001; p-mTOR: p < 0.001; p-P70S6K: p < 0.001). LM had no significant differences when compared to KHE.

CONCLUSIONS

The absence of TSC2 and PTEN caused abnormal activation of the mTOR signaling pathway and may be involved in the pathogenesis of KHE. The expression of mTOR-related proteins in TA and LM was similar to KHE, unlike IH. The KHE pattern of expression [PTEN (-), TSC2 (-), p-mTOR (+), p-P70S6K (+), and p-4EBP1 (+)] suggested that sirolimus may be a good therapeutic choice.

Sirolimus Treatment of an Infant With Intrathoracic Kaposiform Hemangioendothelioma Complicated by Life-threatening Pleural and Pericardial Effusions

Kaposiform hemangioendothelioma (KHE) is a rare infiltrative vascular tumor that may be associated with Kasabach-Merritt Phenomenon (KMP), which is a consumptive coagulopathy with potentially life-threatening thrombocytopenia. Management of KHE and KMP is challenging, and currently, there are no standardized validated treatment protocols. Mammalian target of rapamycin inhibitors have been shown to be effective in the treatment of KHE. We describe a term male who presented as a diagnostic dilemma with life-threatening pleural and pericardial effusions and severe thrombocytopenia. After extensive work-up the etiology for his condition was determined to be KHE with KMP. The patient was commenced on sirolimus and responded well to therapy with resolution of KMP.

Development of a biomarker of efficacy in second-line treatment for lymphangioma of the tongue: a pilot study

Lymphangioma of the tongue is a rare lymphatic malformation, and various authors have reported the successful use of sirolimus for its treatment. However, the safety of sirolimus in children needs further evaluation so that those who do not respond are not necessarily exposed to its potential adverse effects. We hypothesised that assessment of lymphangiogenesis can be used to predict whether the patient will respond to sirolimus, so we organised a prospective study after ethics committee approval had been given. After clinical and histological diagnoses of lymphangioma of the tongue had been confirmed, 16 patients were given sirolimus 0.8mg/day in three divided doses. Clinical response was assessed and compared with lymphatic microvessel density (LMVD), which was calculated immunohistochemically using the monoclonal antibody D2-40 as the lymphatic endothelial marker. Nine patients responded well, five partially, and two failed to respond. Mean (SD) LVD among the good responders was 21.00 (3.74), whereas among non-responders it was 8.00 (4.24). There was a significant difference in mean LVD between good responders, partial responders, and non-responders (p=0.04). Sirolimus is effective in treating children with lymphangioma of the tongue, and lymphangiogenesis is a useful therapeutic predictive marker.