Visualization of fluid drainage pathways in lymphatic vessels and lymph nodes using a mouse model to test a lymphatic drug delivery system

Drug Combination Nanoparticles Containing Gemcitabine and Paclitaxel Enable Orthotopic 4T1 Breast Tumor Regression

Early diagnosis, intervention, and therapeutic advancements have extended the lives of breast cancer patients; however, even with molecularly targeted therapies, many patients eventually progress to metastatic cancer. Recent data suggest that residual breast cancer cells often reside in the lymphatic system before rapidly spreading through the bloodstream. To address this challenge, an effective drug combination composed of gemcitabine (G) and paclitaxel (T) is administered intravenously in sequence at the metastatic stage, but intravenous GT infusion may limit lymphatic GT drug accessibility and asynchronous drug exposure in cancer cells within the lymph. To determine whether co-localization of intracellular gemcitabine and paclitaxel (referred to as GT) could overcome these limitations and enhance the efficacy of GT, we have evaluated a previously reported GT drug-combination formulated in nanoparticle (referred to as GT-in-DcNP) evaluated in an orthotopic breast tumor model. Previously, with indocyanine green-labeled nanoparticles, we reported that GT-in-DcNP particles after subcutaneous dosing were taken up rapidly and preferentially into the lymph instead of blood vessels. The pharmacokinetic study showed enhanced co-localization of GT within the tumors and likely through lymphatic access, before drug apparency in the plasma leading to apparent long-acting plasma time-course. The mechanisms may be related to significantly greater inhibitions of tumor growth-by 100 to 140 times-in both sub-iliac and axillary regions compared to the equivalent dosing with free-and-soluble GT formulation. Furthermore, GT-in-DcNP exhibited dose-dependent effects with significant tumor regression. In contrast, even at the highest dose of free GT combination, only a modest tumor growth reduction was notable. Preliminary studies with MDA-231-HM human breast cancer in an orthotopic xenograft model indicated that GT-in-DcNP may be effective in suppressing human breast tumor growth. Taken together, the synchronized delivery of GT-in-DcNP to mammary tumors through the lymphatic system offers enhanced cellular retention and greater efficacy.

Advancing insights into in vivo meningeal lymphatic vessels with stereoscopic wide-field photoacoustic microscopy

Meningeal lymphatic vessels (mLVs) play a pivotal role in regulating metabolic waste from cerebrospinal fluid (CSF). However, the current limitations in field of view and resolution of existing imaging techniques impede understanding the stereoscopic morphology and dynamic behavior of mLVs in vivo. Here, we utilized dual-contrast functional photoacoustic microscopy to achieve wide-field intravital imaging of the lymphatic system, including mLVs and glymphatic pathways. The stereoscopic photoacoustic microscopy based on opto-acoustic confocal features has a depth imaging capability of 3.75 mm, facilitating differentiation between mLVs on the meninges and glymphatic pathways within the brain parenchyma. Subsequently, using this imaging technique, we were able to visualize the dynamic drainage of mLVs and identify a peak drainage period occurring around 20-40 min after injection, along with determining the flow direction from CSF to lymph nodes. Inspiringly, in the Alzheimer's disease (AD) mouse model, we observed that AD mice exhibit a ~ 70% reduction in drainage volume of mLVs compared to wild-type mice. With the development of AD, there is be continued decline in mLVs drainage volume. This finding clearly demonstrates that the AD mouse model has impaired CSF drainage. Our study opens up a horizon for understanding the brain's drainage mechanism and dissecting mLVs-associated neurological disorders.

Safety and efficacy of intracranial vascularized submental lymph node transfer for treating hydrocephalus

Hydrocephalus is routinely treated with ventriculoperitoneal shunt drainage of cerebrospinal fluid (CSF), a procedure plagued by high morbidity and frequent revisions. Vascularized submental lymph node (VSLN) transplants act as lymphatic pumps to drain interstitial fluid (ISF) from lymphedematous extremities. As the field of neuro-lymphatics comes to fruition, we hypothesize the efficacy of VSLN in the drainage of intracranial CSF-ISF. We report novel placement of VSLN in the temporal subdural space in two patients diagnosed with symptomatic communicating hydrocephalus. At a minimum follow-up of 1 month postoperatively, both experienced radiological and clinical improvements.

Intralymphatic injection of chemotherapy drugs modulated with glucose improves their anticancer effect

Lymph node metastasis (LNM) has a significant impact on cancer prognosis, emphasizing the need for effective treatment strategies. This study investigated the potential use of high osmotic pressure drug solutions with low viscosity administration using a lymphatic drug delivery system (LDDS) to improve LNM treatment outcomes. The hypothesis was that injection of epirubicin or nimustine at high osmotic pressure but without altered viscosity would enhance drug retention and accumulation in LNs, thereby improving the efficacy of treatment. Biofluorescence analysis revealed enhanced drug accumulation and retention in LNs after administration using LDDS compared to intravenous (i.v) injection. Histopathological results demonstrated minimal tissue damage in the LDDS groups. Pharmacokinetic analysis revealed an improved treatment response with higher drug accumulation and retention in LNs. The LDDS approach offers the potential for greatly reduced side effects of chemotherapy drugs, lower dosage requirements and crucially increased drug retention in LNs. The results highlight the promise of high osmotic pressure drug solutions with low viscosity administrated using the LDDS for enhancing the treatment efficacy of LN metastasis. Further research and clinical trials are warranted to validate these results and optimize the clinical translation of this novel treatment technique.

Drug formulation augments the therapeutic response of carboplatin administered through a lymphatic drug delivery system

Treatment of metastatic lymph nodes (LNs) is challenging due to their unique architecture and biophysical traits. Systemic chemotherapy fails to impede tumor progression in LNs due to poor drug uptake and retention by LNs, resulting in fatal systemic metastasis. To effectively treat LN metastasis, achieving specific and prolonged retention of chemotherapy drugs in the tumor-draining LNs is essential. The lymphatic drug-delivery system (LDDS) is an ultrasound-guided drug-delivery methodology for administration of drugs to LNs that addresses these requirements. However, early-stage metastatic LNs have an additional set of drug transport barriers, such as elevated intranodal pressure and viscosity, that negatively impact drug diffusion. In the present study, using formulations of elevated osmotic pressure and viscosity relative to saline, we sought to favorably alter the LN's physical environment and study its impact on pharmacokinetics and consequently the therapeutic efficacy of carboplatin delivered using the LDDS. Our study confirmed the capability of a drug formulation with elevated osmotic pressure and viscosity to alter the architecture of LNs, as it caused notable expansion of the lymphatic sinus. Additionally, the study delineated an optimal range of osmotic pressure and viscosity, centered around 1897 kPa and 11.5 mPa·s, above and below which therapeutic efficacy was found to decline markedly. These findings suggest that formulation osmotic pressure and viscosity are parameters that require critical consideration as they can both hinder and promote tumorigenesis. The facile formulation reported here has wide-ranging applicability across cancer spectrums and is thus anticipated to be of great clinical benefit.

Dermal Lymphatic Capillaries Do Not Obey Murray's Law

Lymphatic vessels serve as a major conduit for the transport of interstitial fluid, immune cells, lipids and drugs. Therefore, increased knowledge about their development and function is relevant to clinical issues ranging from chronic inflammation and edema, to cancer metastasis to targeted drug delivery. Murray's Law is a widely-applied branching rule upheld in diverse circulatory systems including leaf venation, sponge canals, and various human organs for optimal fluid transport. Considering the unique and diverse functions of lymphatic fluid transport, we specifically address the branching of developing lymphatic capillaries, and the flow of lymph through these vessels. Using an empirically-generated dataset from wild type and genetic lymphatic insufficiency mouse models we confirmed that branching blood capillaries consistently follow Murray's Law. However surprisingly, we found that the optimization law for lymphatic vessels follows a different pattern, namely a Murray's Law exponent of ~1.45. In this case, the daughter vessels are smaller relative to the parent than would be predicted by the hypothesized radius-cubed law for impermeable vessels. By implementing a computational fluid dynamics model, we further examined the extent to which the assumptions of Murray's Law were violated. We found that the flow profiles were predominantly parabolic and reasonably followed the assumptions of Murray's Law. These data suggest an alternate hypothesis for optimization of the branching structure of the lymphatic system, which may have bearing on the unique physiological functions of lymphatics compared to the blood vascular system. Thus, it may be the case that the lymphatic branching structure is optimized to enhance lymph mixing, particle exchange, or immune cell transport, which are particularly germane to the use of lymphatics as drug delivery routes.

Intranodal delivery of modified docetaxel: Innovative therapeutic method to inhibit tumor cell growth in lymph nodes

Delivery of chemotherapeutic agents into metastatic lymph nodes (LNs) is challenging as they are unevenly distributed in the body. They are difficult to access via traditional systemic routes of drug administration, which produce significant adverse effects and result in low accumulation of drugs into the cancerous LN. To improve the survival rate of patients with LN metastasis, a lymphatic drug delivery system (LDDS) has been developed to target metastatic LN by delivering chemotherapy agents into sentinel LN (SLN) under ultrasound guidance. The LDDS is an advanced method that can be applied in the early stage of the progression of tumor cells in the SLN before tumor mass formation has occurred. Here we investigated the optimal physicochemical ranges of chemotherapeutic agents’ solvents with the aim of increasing treatment efficacy using the LDDS. We found that an appropriate osmotic pressure range for drug administration was 700–3,000 kPa, with a viscosity < 40 mPa⋅s. In these physicochemical ranges, expansion of lymphatic vessels and sinuses, drug retention, and subsequent antitumor effects could be more precisely controlled. Furthermore, the antitumor effects depended on the tumor progression stage in the SLN, the injection rate, and the volumes of administered drugs. We anticipate these optimal ranges to be a starting point for developing more effective drug regimens to treat metastatic LN with the LDDS.

The Therapeutic Effect of Second Near-Infrared Absorbing Gold Nanorods on Metastatic Lymph Nodes via Lymphatic Delivery System

Photothermal therapy has been established recently as a non-invasive treatment protocol for cancer metastatic lymph nodes. Although this treatment approach shows efficient tumour ablation towards lymph node metastasis, the monitoring and reporting of treatment progress using the lymphatic delivery channel still need to be explored. Herein, we investigated the anti-tumour effect of pegylated gold nanorods with a high aspect ratio (PAuNRs) delivered via the lymphatic route in a mouse model. In this study, breast carcinoma (FM3A-Luc) cells were inoculated in the subiliac lymph node (SiLN) to induce metastasis in the proper axillary lymph node (PALN). The treatment was initiated by injecting the PAuNRs into the accessory axillary lymph node (AALN) after tumour metastasis was confirmed in the PALN followed by external NIR laser irradiation under a temperature-controlled cooling system. The anti-tumour impact of the treatment was evaluated using an in vivo bioluminescence imaging system (IVIS). The results showed a time-dependent reduction in tumour activity with significant treatment response. Tumour growth was inhibited in all mice treated with PAuNRs under laser irradiation; results were statistically significant (** p < 0.01) even after treatment was concluded on day 3. We believe that this non-invasive technique would provide more information on the dynamics of tumour therapy using the lymphatically administered route in preclinical studies.

Optimization of the delivery of molecules into lymph nodes using a lymphatic drug delivery system with ultrasound

Conventional treatment for lymph node (LN) metastasis such as systemic chemotherapy have notable disadvantages that lead to the development of unwanted effects. Previously, we have reported the lymphatic administration of drugs into metastatic LNs using a lymphatic drug delivery system (LDDS). However, prior studies of the LDDS have not attempted to optimize the conditions for efficient drug delivery. Here, we investigated the influence of several factors on the efficiency of drug delivery by a LDDS in conjunction with ultrasound (US). First, the effect of the injection rate on delivery efficiency was evaluated. Fluorescent molecules injected into an upstream LN were delivered more effectively into a downstream LN when a lower injection rate was used. Second, the influence of molecular weight on drug delivery efficiency was determined. We found that molecules with a molecular weight >10,000 were poorly delivered into the LN. Finally, we assessed whether the administration route affected the delivery efficiency. We found that the delivery efficiency was higher when molecules were administered into an upstream LN that was close to the target LN. These findings revealed the importance of a drug's physical properties if it is to be administered by LDDS to treat LN metastasis.

BRAFV600E Transduction of an SV40-Immortalized Normal Human Thyroid Cell Line Induces Dedifferentiated Thyroid Carcinogenesis in a Mouse Xenograft Model

Background: Despite active studies of the clinical importance of BRAF^V600E, suitable research models to investigate the role of this mutation in the etiopathogenesis of human thyroid cancers are limited. Thus, we generated cell lines by transducing the simian virus (SV)-40 immortalized human thyroid cell line Nthy-ori 3-1 (Nthy) with lentiviral vectors expressing either BRAF^WT (Nthy/WT) or BRAF^V600E. Nthy/WT and Nthy/V600E cells were then xenografted into mice to evaluate the carcinogenic role of BRAF^V600E. Methods: Each cell line was subcutaneously injected into NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ mice, and a pathological analysis was performed. The effects of the mutation were further verified by using a BRAF^V600E-selective inhibitor (PLX-4032, vemurafenib). The transcriptome was analyzed by RNA sequencing and compared with data from The Cancer Cell Line Encyclopedia and Gene Expression Omnibus. Results: While Nthy/WT was not tumorigenic in vivo, Nthy/V600E formed tumors reaching 2784.343 mm³ in 4 weeks, on average. A pathological analysis indicated that Nthy/V600E tumors were dedifferentiated thyroid cancer. We found metastases in the lung, liver, and relevant lymph nodes. A transcriptomic analysis revealed 5512 differentially expressed genes (DEGs) between the mutant and wild-type cell lines, and more DEGs were shared with anaplastic thyroid cancer than with papillary thyroid cancer. BRAF^V600E activated the cell cycle mainly by regulating G1/S phases. PLX-4032 treatment significantly inhibited tumor growth and metastasis. Conclusions: Our data show that BRAF^V600E plays a pivotal role in the carcinogenic transformation of an SV40-transfected immortalized normal human thyroid cell line. This xenograft model is expected to contribute to studies of the etiopathogenesis and treatment of highly malignant thyroid cancers.

In vivo delivery of an exogenous molecule into murine T lymphocytes using a lymphatic drug delivery system combined with sonoporation

Physical delivery of exogenous molecules into lymphocytes is extremely challenging because conventional methods have notable limitations. Here, we evaluated the potential use of acoustic liposomes (ALs) and sonoporation to deliver exogenous molecules into lymphocytes within a lymph node (LN). MXH10/Mo-lpr/lpr (MXH10/Mo/lpr) mice, which show systemic LN swelling, were used as the model system. After direct injection into the subiliac LN, a solution containing both ALs and TOTO-3 fluorophores (molecular weight: 1355) was able to reach the downstream proper axillary LN (PALN) via the lymphatic vessels (LVs). This led to the accumulation of a high concentration of TOTO-3 fluorophores and ALs in the lymphatic sinuses of the PALN, where a large number of lymphocytes were densely packed. Exposure of the PALN to >1.93 W/cm² of 970-kHz ultrasound allowed the solution to extravasate into the parenchyma and reach the large number of lymphocytes in the sinuses. Flow cytometric analysis showed that TOTO-3 molecules were delivered into 0.49 ± 0.23% of CD8⁺7AAD^- cytotoxic T lymphocytes. Furthermore, there was no evidence of tissue damage. Thus, direct administration of drugs into LVs combined with sonoporation can improve the delivery of exogenous molecules into primary lymphocytes. This technique could become a novel approach to immunotherapy.

An in silico model of cytotoxic T-lymphocyte activation in the lymph node following short peptide vaccination

Tumour immunotherapy is dependent upon activation and expansion of tumour-targetting immune cells, known as cytotoxic T-lymphocytes (CTLs). Cancer vaccines developed in the past have had limited success and the mechanisms resulting in failure are not well characterized. To elucidate these mechanisms, we developed a human-parametrized, in silico, agent-based model of vaccination-driven CTL activation within a clinical short-peptide vaccination context. The simulations predict a sharp transition in the probability of CTL activation, which occurs with variation in the separation rate (or off-rate) of tumour-specific immune response-inducing peptides (cognate antigen) from the major histocompatibility class I (MHC-I) receptors of dendritic cells (DCs) originally at the vaccination site. For peptides with MHC-I off-rates beyond this transition, it is predicted that no vaccination strategy will lead to successful expansion of CTLs. For slower off-rates, below the transition, the probability of CTL activation becomes sensitive to the numbers of DCs and T cells that interact subsequent to DC migration to the draining lymph node of the vaccination site. Thus, the off-rate is a key determinant of vaccine design.

Noninvasive and real-time pharmacokinetics imaging of polymeric nanoagents in the thoracoepigastric vein networks of living mice

Noninvasive and real-time visualization of the thoracoepigastric veins (TVs) of living mice was demonstrated by using two-photon excitation (TPE) optical imaging with a Eu-luminescent polymeric nanoagent as the angiographic contrast. The spatiotemporal evolution of the polymeric nanoagent in TVs was monitored for up to 2 h by TPE time-resolved (TPE-TR) bioimaging, which is free from the interference of tissue autofluorescence. A wide field-of-view covering the thoracoabdominal region allowed the visualization of the entire TV network with an imaging depth of 1 to 2 mm and a lateral resolution of 80 μm at submillimeter. Detailed analysis of the uptake, transport, and clearance processes of the polymeric nanoagent revealed a clearance time constant of ∼30  min and an apparent clearance efficiency of 80% to 90% for the nanoagent in both axial and lateral TVs. TPE-TR imaging of the dissected internal organs proved that the liver is mainly responsible for the sequestration of the nanoagent, which is consistent with the apparent retention efficiency of liver, ∼32  %  , as determined by the real-time in vivo TV imaging. We demonstrate the potency of TPE-TR modality in the pharmacokinetics imaging of the peripheral vascular systems of animal models, which can be beneficial for related nanotheranostics study.

A model system for studying superselective radiotherapy of lymph node metastasis in mice with swollen lymph nodes

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It is difficult to irradiate individual mouse lymph nodes (LNs) 1–2 mm in diameter.

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A maximum single dose is <8 Gy for whole-body irradiation of wild-type mice.

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We succeeded in applying radiation (8 Gy) to a single LN in mice with swollen LNs.

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Radiation-induced abscopal effects were observed in mice with swollen LNs.

Utilizing mice with swollen lymph nodes, we succeeded in irradiating individual metastatic lymph nodes through a hole in a lead shield. This system enabled us to increase the radiation dose to >8 Gy (the lethal dose for total-body irradiation) and evaluate both direct and abscopal antitumor effects.

Optimal range of injection rates for a lymphatic drug delivery system

The lymphatic drug delivery system (LDDS) is a new technique that permits the injection of drugs into a sentinel lymph node (SLN) at an early stage of tumor metastasis, thereby treating metastasis in the SLN and its secondary lymph nodes (LNs). The quantity of drug required for a LDDS is much smaller than that needed for systemic chemotherapy. However, the relationship between the rate of drug injection into a SLN and the amount of drug reaching the secondary LNs has not been investigated. In this study, we used an MXH10/Mo-lpr/lpr mouse model to show that the optimal rate for the injection of a fluorescent dye by a LDDS was 10 to 80 μL/min. An injection rate of 10 to 80 μL/min was able to fill the downstream LN. However, an injection rate of 100 μL/min drove the fluorescent dye into the efferent lymphatic vessels and thoracoepigastric vein, decreasing the amount of dye retained in the downstream LN. Bolus injection (defined as an injection rate of 2400 μL/min) was unable to deliver fluorescent dye into the downstream LN. These results agree with the impulse values calculated from the injection pressures in the upstream LN. We anticipate that our findings will facilitate the development of a LDDS for use in the clinic.

Development of a mouse model for the visual and quantitative assessment of lymphatic trafficking and function by in vivo imaging

Methods for quantitative analysis of long distance lymphatic transport of nanoparticles in live animals are yet to be established. We established a mouse model for analysis of time-dependent transport just beneath the abdominal skin to investigate lymph node-to-lymph node trafficking by in vivo imaging. For this purpose, popliteal lymph nodes (PLNs) as well as efferent and afferent lymphatic vessels, marginal veins, and feeding blood vessels were surgically resected to change the lymphatic flow from footpad injections. Using this model, we observed a novel lymphatic flow from the footpad to the proper axillary lymph node (ALN) via the inguinal lymph node (ILN). This drainage pathway was maintained over 12 weeks. Time-dependent transportation of 1,1′-dioctadecyltetramethyl indotricarbocyanine iodide-labelled liposomes from the footpad to the ILN was successfully quantified by an in vivo imaging system. Moreover, congestion and development of a new collateral lymphatic route was visualised under a lymphedema status. Histological analysis of abdominal skin tissues of this model revealed that PLN resection had no effect on the abdominal lymphatic system between the ILN and ALN. These data indicate that this model might be useful to clarify the mechanisms of lymphedema and study direct transportation of lymph or other substances between lymph nodes.

Therapeutic effect of cisplatin given with a lymphatic drug delivery system on false-negative metastatic lymph nodes

Systemic administration of drugs into the blood circulation is standard treatment for prevention of metastasis. However, systemic delivery cannot maintain sufficiently high concentrations of anticancer drugs in lymph nodes (LN). Here, we show that giving cisplatin (CDDP) using a lymphatic drug delivery system (LDDS) has the potential to treat false-negative metastatic LN. We found that in MXH10/Mo-lpr/lpr mice, which develop systemic swelling of LN up to 10 mm in diameter, accumulation of indocyanine green (ICG), which has a similar molecular weight to CDDP, in a target LN was greater for lymphatic delivery of ICG than for systemic (i.v.) administration. Furthermore, CDDP administration with a LDDS inhibited tumor growth in false-negative metastatic LN and produced fewer adverse effects than systemically given CDDP. We anticipate that drug delivery using a LDDS will, in time, replace systemic chemotherapy for the treatment of false-negative metastatic LN.

Lymphatic drainage system of the brain: A novel target for intervention of neurological diseases

The belief that the vertebrate brain functions normally without classical lymphatic drainage vessels has been held for many decades. On the contrary, new findings show that functional lymphatic drainage does exist in the brain. The brain lymphatic drainage system is composed of basement membrane-based perivascular pathway, a brain-wide glymphatic pathway, and cerebrospinal fluid (CSF) drainage routes including sinus-associated meningeal lymphatic vessels and olfactory/cervical lymphatic routes. The brain lymphatic systems function physiological as a route of drainage for interstitial fluid (ISF) from brain parenchyma to nearby lymph nodes. Brain lymphatic drainage helps maintain water and ion balance of the ISF, waste clearance, and reabsorption of macromolecular solutes. A second physiological function includes communication with the immune system modulating immune surveillance and responses of the brain. These physiological functions are influenced by aging, genetic phenotypes, sleep-wake cycle, and body posture. The impairment and dysfunction of the brain lymphatic system has crucial roles in age-related changes of brain function and the pathogenesis of neurovascular, neurodegenerative, and neuroinflammatory diseases, as well as brain injury and tumors. In this review, we summarize the key component elements (regions, cells, and water transporters) of the brain lymphatic system and their regulators as potential therapeutic targets in the treatment of neurologic diseases and their resulting complications. Finally, we highlight the clinical importance of ependymal route-based targeted gene therapy and intranasal drug administration in the brain by taking advantage of the unique role played by brain lymphatic pathways in the regulation of CSF flow and ISF/CSF exchange.

Evaluation of the enhanced permeability and retention effect in the early stages of lymph node metastasis

Most solid cancers spread to new sites via the lymphatics before hematogenous dissemination. However, only a small fraction of an intravenously administered anti‐cancer drug enters the lymphatic system to reach metastatic lymph nodes (LN). Here, we show that the enhanced permeability and retention (EPR) effect is not induced during the early stages of LN metastasis. Luciferase‐expressing tumor cells were injected into the subiliac LN of the MXH10/Mo‐lpr/lpr mouse to induce metastasis to the proper axillary LN (PALN). In vivo biofluorescence imaging was used to confirm metastasis induction and to quantify the EPR effect, measured as PALN accumulation of intravenously injected indocyanine green (ICG) liposomes. PALN blood vessel volume changes were measured by contrast‐enhanced high‐frequency ultrasound imaging. The volume and density of blood vessels in the PALN increased until day 29 after inoculation, whereas the LN volume remained constant. ICG retention was first detected on day 29 post‐inoculation. While CD31‐positive cells increased up to day 29 post‐inoculation, α‐smooth muscle actin‐positive cells were detected on day 29 post‐inoculation for the first time. These results suggest that the EPR effect was not induced in the early stages of LN metastasis; therefore, systemic chemotherapy would likely not be beneficial during the early stages of LN metastasis. The development of an alternative drug delivery system, independent of the EPR effect, is required for the treatment of LN metastasis.

A novel treatment for metastatic lymph nodes using lymphatic delivery and photothermal therapy

Systemic delivery of an anti-cancer agent often leads to only a small fraction of the administered dose accumulating in target sites. Delivering anti-cancer agents through the lymphatic network can achieve more efficient drug delivery for the treatment of lymph node metastasis. We show for the first time that polymeric gold nanorods (PAuNRs) can be delivered efficiently from an accessory axillary lymph node to a tumor-containing proper axillary lymph node, enabling effective treatment of lymph node metastasis. In a mouse model of metastasis, lymphatic spread of tumor was inhibited by lymphatic-delivered PAuNRs and near-infrared laser irradiation, with the skin temperature controlled by cooling. Unlike intravenous injection, lymphatic injection delivered PAuNRs at a high concentration within a short period. The results show that lymphatic administration has the potential to deliver anti-cancer agents to metastatic lymph nodes for inhibition of tumor growth and could be developed into a new therapeutic method.

Study of fluid dynamics reveals direct communications between lymphatic vessels and venous blood vessels at lymph nodes of mice

Cancer cells metastasize to lymph nodes, with distant metastasis resulting in poor prognosis. The role of lymph node metastasis (LNM) in the spread of cancer to distant organs remain incompletely characterized. The visualization of flow dynamics in the lymphatic and blood vessels of MXH10/Mo-lpr/lpr mice, which develop systemic swelling of lymph nodes up to 10mm in diameter, has revealed that lymph nodes have the potential to be a direct source of systemic metastasis. However, it is not known whether these fluid dynamics characteristics are universal phenomena present in other strains of laboratory mice. Here we show that the fluid dynamics observed in MXH10/Mo-lpr/lpr mice are the same as those observed in C57BL/6J, BALB/cAJcl and NOD/ShiJic-scidJcl mice. Furthermore, when fluorescent solution was injected into a tumor-bearing lymph node, the flow dynamics observed in the efferent lymphatic vessels and thoracoepigastric vein depended on the type of tumor cell. Our results indicate that fluid dynamics in the lymphatic and blood vessels of MXH10/Mo-lpr/lpr mice are generalized phenomena seen in conventional laboratory mice. We anticipate our results can facilitate studies of the progression of lymphatic metastasis to hematogenous metastasis via lymph nodes and the early diagnosis and treatment of LNM.

New concept for the prevention and treatment of metastatic lymph nodes using chemotherapy administered via the lymphatic network

Intravenous chemotherapy has poor access to metastatic lymph nodes (LNs) and is limited by short-lived drug concentrations. Here, we describe the administration of chemotherapy via the lymphatic network as a new concept for the prevention and treatment of metastatic LNs. A metastatic LN can be treated by the injection of drugs into an upstream LN, either the sentinel LN (SLN) or another upstream LN. In a mouse model, tumor cells were inoculated into the subiliac LN (SiLN) to induce metastasis to the proper axillary LN (PALN). Two routes were used for drug delivery to the PALN, namely from the SiLN and from the accessory axillary LN (AALN). We found that tumor masses were formed in lymphatic vessels between the SiLN and PALN. The flow of fluorescent solution injected into the SiLN towards the PALN decreased with tumor mass formation. Delivery from the AALN (free of metastatic tumor cells) to the PALN was identified as an alternative route. Intranodal injection can deliver high concentrations of drugs to secondary metastatic LNs. The study advocates a new concept for the prevention and treatment of metastatic lymph nodes whereby drugs injected into upstream lymph nodes can reach metastatic lymph nodes via the lymphatic network.

Characterization of internodal collecting lymphatic vessel function after surgical removal of an axillary lymph node in mice

Secondary lymphedema is an acquired lymphatic disorder, which occurs because of damage to the lymphatic system from surgery and/or radiation therapy for cancer treatment. However, it remains unknown how post-nodal collecting lymphatic vessels (CLVs) draining to the surgical wound area change in response to lymphadenectomy. We investigated functional and architectural changes of inguinal-to-axillary internodal CLVs (ICLVs) in mice after a single axillary LN (ALN) dissection using near-infrared fluorescence imaging. Our data showed no lymph flow in the ICLVs draining from the inguinal LN (ILN) at 2 days post-surgery. External compression enabled visualization of a small segment of contractile fluorescent ICLVs, but not all the way to the axillary region. At day 6, abnormal lymphatic drainage patterns, including lateral and retrograde lymph flow via vessels branching off the ICLVs were observed, which started to disappear beginning 9 days after surgery. The administration of vascular endothelial growth factor (VEGF)-C into the wound increased resolution of altered lymphatic drainage. Lymphatic drainage from the base of the tail to the ILN did not significantly change over time. These results demonstrate that lymph flow in the CLVs is dramatically affected by a LN dissection and long-term interruption of lymph flow might cause CLV dysfunction and thus contribute to chronic lymphatic disorders.

Early diagnosis of lymph node metastasis: Importance of intranodal pressures

Regional lymph node status is an important prognostic indicator of tumor aggressiveness. However, early diagnosis of metastasis using intranodal pressure, at a stage when lymph node size has not changed significantly, has not been investigated. Here, we use an MXH10/Mo-lpr/lpr mouse model of lymph node metastasis to show that intranodal pressure increases in both the subiliac lymph node and proper axillary lymph node, which are connected by lymphatic vessels, when tumor cells are injected into the subiliac lymph node to induce metastasis to the proper axillary lymph node. We found that intranodal pressure in the subiliac lymph node increased at the stage when metastasis was detected by in vivo bioluminescence, but when proper axillary lymph node volume (measured by high-frequency ultrasound imaging) had not increased significantly. Intravenously injected liposomes, encapsulating indocyanine green, were detected in solid tumors by in vivo bioluminescence, but not in the proper axillary lymph node. Basic blood vessel and lymphatic channel structures were maintained in the proper axillary lymph node, although sinus histiocytosis was detected. These results show that intranodal pressure in the proper axillary lymph node increases at early stages when metastatic tumor cells have not fully proliferated. Intranodal pressure may be a useful parameter for facilitating early diagnosis of lymph node metastasis.

A Novel Treatment Method for Lymph Node Metastasis Using a Lymphatic Drug Delivery System with Nano/Microbubbles and Ultrasound

Chemotherapy based on hematogenous administration of drugs to lymph nodes (LNs) located outside the surgically resected area shows limited tissue selectivity and inadequate response rates, resulting in poor prognosis. Here, we demonstrate proof of concept for a lymphatic drug delivery system using nano/microbubbles (NMBs) and ultrasound (US) to achieve sonoporation in LNs located outside the dissection area. First, we demonstrated the in vitro effectiveness of doxorubicin (Dox) delivered into three different tumor cell lines by sonoporation. Sonoporation increased the Dox autofluorescence signal and resulted in a subsequent decrease in cell viability. Next, we verified the antitumor effects of Dox in vivo using MXH10/Mo-lpr/lpr mice that exhibit systemic lymphadenopathy, with some peripheral LNs reaching 10 mm in diameter. We defined the subiliac LN (SiLN) as the upstream LN within the dissection area, and the proper axillary LN (PALN) as the downstream LN outside the dissection area. Dox and NMBs were injected into the SiLN and delivered to the PALN via lymphatic vessels; the PALN was then exposed to US when it had filled with solution. We found that sonoporation enhanced the intracellular uptake of Dox leading to high cytotoxicity. We also found that sonoporation induced extravasation of Dox from lymphatic endothelia and penetration of Dox into tumor tissues within the PALN. Furthermore, our method inhibited tumor growth and diminished blood vessels in the PALN while avoiding systemic toxic effects of Dox. Our findings indicate that a lymphatic drug delivery system with sonoporation represents a promising method for treating metastatic LNs located outside the dissection area.

Communication between lymphatic and venous systems in mice

The lymphatic system in mice consists of lymphatic vessels and 22 types of lymph nodes. Metastatic tumor cells in the lymphatic system spread to distant organs through the venous system. However, the communication routes between the lymphatic and venous systems have not been fully elucidated. Here, we identify the communication routes between the lymphatic and venous systems in the axillary and subiliac regions of MXH10/Mo-lpr/lpr inbred mice, which develop systemic swelling of lymph nodes up to 10mm in diameter, allowing investigation of the topography of the lymph nodes and lymphatic vessels. Using a gross anatomy dissection approach, the efferent lymphatic vessels of the proper axillary lymph node were shown to communicate with the subclavian vein. Furthermore, we found that the thoracoepigastric vein, which connects the subclavian vein and inferior vena cava, runs adjacent to the subiliac and proper axillary lymph nodes, and receives venous blood from these lymph nodes routed through small branches. The direction of blood flow in the thoracoepigastric vein occurred in two directions in the intermediate region between the proper axillary lymph node and subiliac lymph node; one to the subclavian vein, the other to the inferior vena cava. This paper reveals the anatomy of the communication between the lymphatic and venous systems in the axillary and subiliac regions of the mouse, and provides new insights relevant to the investigation of the mechanisms of lymph node metastasis and cancer immunology, and the development of diagnostic and treatment methods for lymph node metastasis, including drug delivery systems.