Near-Infrared Fluorescence Imaging Directly Visualizes Lymphatic Drainage Pathways and Connections between Superficial and Deep Lymphatic Systems in the Mouse Hindlimb

Lymphatic platelet thrombosis limits bone repair by precluding lymphatic transporting DAMPs

In the musculoskeletal system, lymphatic vessels (LVs), which are interdigitated with blood vessels, travel and form an extensive transport network. Blood vessels in bone regulate osteogenesis and hematopoiesis, however, whether LVs in bone affect fracture healing is unclear. Here, we investigate the lymphatic draining function at the tibial fracture sites using near-infrared indocyanine green lymphatic imaging (NIR-ICG) and discover that lymphatic drainage insufficiency (LDI) starts on day one and persists for up to two weeks following the fracture in male mice. Sufficient lymphatic drainage facilitates fracture healing in male mice. Furthermore, we identify that lymphatic platelet thrombosis (LPT) blocks the draining lymphoid sinus and LVs, causes LDI, and inhibits fracture healing in male mice, which can be rescued by a blood thinner. Moreover, unblocked lymphatic drainage decreases neutrophils and increases M2-type macrophages of the hematoma niche to support osteoblast (OB) survival and bone marrow-derived mesenchymal stem cell (BMSC) proliferation via transporting damage-associated molecular patterns (DAMPs) in male rats. Lymphatic platelet thrombolysis also benefits senile fracture healing in female mice. These findings demonstrate that LPT limits bone regeneration by impeding lymphatic transporting DAMPs. Together, these findings represent a way forward in the treatment of bone repair.

Idiopathic pulmonary fibrosis (IPF): Diagnostic routes using novel biomarkers

Idiopathic pulmonary fibrosis (IPF) diagnosis is still the diagnosis of exclusion. Differentiating from other forms of interstitial lung diseases (ILDs) is essential, given the various therapeutic approaches. The IPF course is now unpredictable for individual patients, although some genetic factors and several biomarkers have already been associated with various IPF prognoses. Since its early stages, IPF may be asymptomatic, leading to a delayed diagnosis. The present review critically examines the recent literature on molecular biomarkers potentially useful in IPF diagnostics. The examined biomarkers are grouped into breath and sputum biomarkers, serologically assessed extracellular matrix neoepitope markers, and oxidative stress biomarkers in lung tissue. Fibroblasts and complete blood count have also gained recent interest in that respect. Although several biomarker candidates have been profiled, there has yet to be a single biomarker that proved specific to the IPF disease. Nevertheless, various IPF biomarkers have been used in preclinical and clinical trials to verify their predictive and monitoring potential.

A novel therapy for fracture healing by increasing lymphatic drainage

Background

The musculoskeletal system contains an extensive network of lymphatic vessels. Decreased lymph flow of the draining collecting lymphatics usually occurs in clinic after traumatic fractures. However, whether defects in lymphatic drainage can affect fracture healing is unclear.

Methods

To investigate the effect of lymphatic dysfunction on fracture healing, we used a selective VEGFR3 tyrosine kinase inhibitor to treat tibial fractured mice for 5 weeks versus a vehicle-treated control. To ensure successfully establishing deceased lymphatic drainage model for fractured mice, we measured lymphatic clearance by near infrared indocyanine green lymphatic imaging (NIR-ICG) and the volume of the draining popliteal lymph nodes (PLNs) by ultrasound at the whole phases of fracture healing. In addition, hindlimb edema from day 0 to day 7 post-fracture, pain sensation by Hargreaves test at day 1 post-fracture, bone histomorphometry by micro-CT and callus composition by Alcian Blue-Hematoxylin/Orange G staining at day 14 post-fracture, and bone quality by biomechanical testing at day 35 post-fracture were applied to evaluate fracture healing. To promote fracture healing via increasing lymphatic drainage, we then treated fractured mice with anti-mouse podoplanin (PDPN) neutralizing antibody or isotype IgG antibody for 1 week to observe lymphatic drainage function and assess bone repair as methods described above.

Results

Compared to vehicle-treated group, SAR-treatment group significantly decreased lymphatic clearance and the volume of draining PLNs. SAR-treatment group significantly increased soft tissue swelling, and reduced bone volume (BV)/tissue volume (TV), trabecular number (Tb.N), woven bone and biomechanical properties of fracture callus. In addition, anti-PDPN treated group significantly reduced the number of CD41+ platelets in PLNs and increased the number of pulsatile lymphatic vessels, lymphatic clearance and the volume of PLNs. Moreover, anti-PDPN treated group significantly reduced hindlimb edema and pain sensation and increased BV/TV, trabecular number (Tb.Th), woven bone and biomechanical properties of fracture callus.

Conclusions

Inhibition of proper lymphatic drainage function delayed fracture healing. Use of a anti-PDPN neutralizing antibody reduced lymphatic platelet thrombosis (LPT), increased lymphatic drainage and improved fracture healing.

The translational potential of this article

(1) We demonstrated lymphatic drainage function is crucial for fracture healing. (2) To unblock the lymphatic drainage and prevent the risk of bleeding and mortality by blood thinner, we demonstrated PDPN neutralizing antibody is a novel and safe way forward in the treatment of bone fracture healing by eliminating LPT and increasing lymphatic drainage.

Efficacy of Neonatal Porcine Bone Marrow-Derived Mesenchymal Stem Cell Xenotransplantation for the Therapy of Hind Limb Lymphedema in Mice

Lymphedema is an intractable disease with few effective therapeutic options. Autologous mesenchymal stem cell (MSC) transplantation is a promising therapy for this disease. However, its use is limited by the cost and time for preparation. Recently, xenotransplantation of porcine MSCs has emerged as an alternative to autologous MSC transplantation. In this study, we aimed to clarify the usefulness of neonatal porcine bone marrow-derived MSC (NpBM-MSC) xenotransplantation for the treatment of lymphedema. One million NpBM-MSCs were xenotransplanted into the hind limbs of mice with severe lymphedema (MSC transplantation group). The therapeutic effects were assessed by measuring the femoral circumference, the volume of the hind limb, the number and diameter of lymphatic vessels in the hind limb, and lymphatic flow using a near-infrared fluorescence (NIRF) imaging system. We compared the effects using mice with lymphedema that did not undergo NpBM-MSC transplantation (negative control group). The condition of the transplanted NpBM-MSCs was also evaluated histologically. The femoral circumference and volume of the hind limb had been normalized by postoperative day (POD) 14 in the MSC transplantation group, but not in the negative control group (P = 0.041). NIRF imaging revealed that lymphatic flow had recovered in the MSC transplantation group by POD 14, as shown by an increase in luminance in the hind limb. Histological assessment also showed that the xenotransplantation of NpBM-MSC increased the proliferation of lymphatic vessels, but they had been rejected by POD 14. The xenotransplantation of NpBM-MSCs is an effective treatment for lymphedema, and this is mediated through the promotion of lymphangiogenesis.

Surgical lymphedema models in the mice hindlimb-A systematic review and quality assessment

BACKGROUND

Lymphedema constitutes a major unsolved problem in plastic surgery. To identify novel lymphedema treatments, preclinical studies are vital. The surgical mouse lymphedema model is popular and cost-effective; nonetheless, a synthesis and overview of the literature with evidence-based guidelines is needed. The aim of this review was to perform a systematic review to establish best practice and support future high-quality animal studies exploring lymphedema treatments.

METHODS

We performed a systematic review following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, searching four databases (PubMed, Embase, Web of Science, and Scopus) from inception-September 2022. The Animals in Research Reporting In Vivo Experiments 2.0 (ARRIVE 2.0) guidelines were used to evaluate reporting quality. Studies claiming to surgically induce lymphedema in the hindlimb of mice were included.

RESULTS

Thirty-seven studies were included. Four main models were used. (1) Irradiation+surgery. (2) A variation of the surgery used by (1) + irradiation. (3) Surgery only (SPDF-model). (4) Surgery only (PLND-model). Remaining studies used other techniques. The most common measurement modality was the caliper. Mean quality coefficient was 0.57. Eighteen studies (49%) successfully induced sustained lymphedema. Combination of methods seemed to yield the best results, with an overrepresentation of irradiation, the removal of two lymph nodes, and the disruption of both the deep and superficial lymph vessels in the 18 studies.

CONCLUSION

Surgical mouse hindlimb lymphedema models are challenged by two related problems: (1) retaining lymphedema for an extended period, that is, establishing a (chronic) lymphedema model (2) distinguishing lymphedema from post-operative edema. Most studies failed to induce lymphedema and used error-prone measurements. We provide an overview of studies claiming to induce lymphedema and advocate improved research via five evidence-based recommendations to use: (1) a proven lymphedema model; (2) sufficient follow-up time, (3) validated measurement methods; (4) ARRIVE-guidelines; (5) contralateral hindlimb as control.

Lymphatic platelet thrombosis limits bone repair by precluding lymphatic transporting DAMPs

Lymphatic vessels (LVs) interdigitated with blood vessels, travel and form an extensive transport network in the musculoskeletal system. Blood vessels in bone regulate osteogenesis and hematopoiesis, however, whether LVs in bone affect fracture healing is unclear. Here, by near infrared indocyanine green lymphatic imaging (NIR-ICG), we examined lymphatic draining function at the tibial fracture sites and found lymphatic drainage insufficiency (LDI) occurred as early as two weeks after fracture. Sufficient lymphatic drainage facilitates fracture healing. In addition, we identified that lymphatic platelet thrombosis (LPT) blocks the draining lymphoid sinus and LVs, caused LDI and then inhibited fracture healing, which can be rescued by a pharmacological approach. Moreover, unblocked lymphatic drainage decreased neutrophils and increased M2-like macrophages of hematoma niche to support osteoblast (OB) survival and bone marrow-derived mesenchymal stem cell (BMSC) proliferation via transporting damage-associated molecular patterns (DAMPs). These findings demonstrate that LPT limits bone regeneration by blocking lymphatic drainage from transporting DAMPs. Together, these findings represent a novel way forward in the treatment of bone repair.

Establishment of a Simple, Reproducible, and Long-lasting Hind Limb Animal Model of Lymphedema

Background

Lymphedema is an intractable disease for which there is currently no established curative therapy. A reliable and long-lasting lymphedema model is essential for development of better treatments. In this study, we aimed to establish a simple, reproducible and long-lasting mouse model of lymphedema.

Methods

Our model is characterized by a combination of a circumferential skin incision in the femoral region, complete dissection of regional lymph nodes, and ablation of the inguinal route in the femoral region. The characteristics of the lymphedema were evaluated and compared with those of two other models. One of these models involved dissection of the subiliac, popliteal, and sciatic lymph nodes (model A) and the other excision of the subiliac, popliteal, and sciatic lymph nodes with cauterization of lymphatic vessels and closure without a skin excision (model B).

Results

Although the lymphedema in models A and B resolved spontaneously, that in the new model lasted for a month with increases in femoral circumference and hind limb volume, thickening of the skin, especially subcutaneous tissue, and congestion of peripheral lymphatic vessels. Furthermore, this model could be used for assessing the therapeutic effects of syngeneic mesenchymal stem cell transplantation. The average operation time for the new model was 14.4 ± 1.3 minutes.

Conclusion

Long-lasting lymphedema can be achieved by our new model, making it suitable for assessing therapies for lymphedema.

The effects of postoperative treadmill exercise on rats with secondary lymphedema

Cancer-related lymphedema (LE) is often caused by radiotherapy and surgery such as lymph node dissection (LND). Previous studies have reported that exercise is beneficial to relieve LE, but the changes in the lymphatic system following exercise are still unclear. This study aimed to examine the changes in lymphatic drainage pathways over the exercise period and beneficial effects of exercise in rats with LE. Twelve rats were randomly allocated into exercise and control groups (EG and CG; n = 6 each). To obtain LE, inguinal and popliteal LND followed by 20 Gy irradiation was performed. Treadmill exercise was 30 minutes/day, 5 days/week over the four-week period. Consecutive indocyanine green (ICG) lymphography images were collected and classified into five patterns: i) linear; ii) splash; iii) stardust; iv) diffuse, and v) none. Ankle thickness was measured weekly. Histopathological evaluation was performed to examine the skin thickness, collagen area fraction (%) and lymphatic vessel density in harvested tissue. ICG lymphography exhibited more linear and splash patterns in the EG at week 3. The difference of swelling between both groups was significantly different at week 4 (p = 0.016). Histopathologic data revealed a thinner epidermis (p = 0.041) and dermis (p = 0.002), lower collagen area fraction (%, p = 0.002), and higher lymph vessel density (p = 0.002) in the EG than the CG. In conclusion, we found that postoperative exercise can facilitate improvement in lymphatic fluid retention in the lymphedema rat model, resulting in improvement of pathological conditions in the lymphatic system.

Multifunctional Gold Nanoclusters for Effective Targeting, Near-Infrared Fluorescence Imaging, Diagnosis, and Treatment of Cancer Lymphatic Metastasis

Developing effective lymph-node (LN) targeting and imaging probes is crucial for the early detection and diagnosis of tumor metastasis to improve patient survival. Most current clinical LN imaging probes are based on small organic dyes (e.g., indocyanine green) or radioactive ^99mTc-complexes, which often suffer from limitations, such as rapid photobleaching, poor signal contrast, and potential biosafety issues. Moreover, these probes cannot easily incorporate therapeutic functions to realize beneficial theranostics without affecting their LN-targeting ability. Herein, we have developed dual-ligand-/multiligand-capped gold nanoclusters (GNCs) for specific targeting, near-infrared (NIR) fluorescence imaging, diagnosis, and treatment of LN cancer metastasis in in vivo mouse models. By optimizing the surface ligand coating, we have prepared Au₂₅(SR₁)_n(SR₂)_18-n (where SR₁ and SR₂ are different functional thiol ligands)-type GNCs, which display highly effective LN targeting, excellent stability and biocompatibility, and optimal body-retention time. Moreover, they can provide continuous NIR fluorescence imaging of LNs for >3 h from a single dose, making them well-suited for fluorescence-guided surgery. Importantly, we have further incorporated methotrexate, a chemotherapeutic drug, into the GNCs without affecting their LN-targeting ability. Consequently, they can significantly improve the efficiency of methotrexate delivery to target LNs, achieving excellent therapeutic efficacy with up to 4-fold lower hepatotoxicity. Thus, the GNCs are highly effective and safe theranostic nanomedicines against cancer lymphatic metastasis.

Long-Duration and Non-Invasive Photoacoustic Imaging of Multiple Anatomical Structures in a Live Mouse Using a Single Contrast Agent

Long-duration in vivo simultaneous imaging of multiple anatomical structures is useful for understanding physiological aspects of diseases, informative for molecular optimization in preclinical models, and has potential applications in surgical settings to improve clinical outcomes. Previous studies involving simultaneous imaging of multiple anatomical structures, for example, blood and lymphatic vessels as well as peripheral nerves and sebaceous glands, have used genetically engineered mice, which require expensive and time-consuming methods. Here, an IgG4 isotype control antibody is labeled with a near-infrared dye and injected into a mouse ear to enable simultaneous visualization of blood and lymphatic vessels, peripheral nerves, and sebaceous glands for up to 3 h using photoacoustic microscopy. For multiple anatomical structure imaging, peripheral nerves and sebaceous glands are imaged inside the injected dye-labeled antibody mass while the lymphatic vessels are visualized outside the mass. The efficacy of the contrast agent to label and localize deep medial lymphatic vessels and lymph nodes using photoacoustic computed tomography is demonstrated. The capability of a single injectable contrast agent to image multiple structures for several hours will potentially improve preclinical therapeutic optimization, shorten discovery timelines, and enable clinical treatments.

Comparison of normal hindlimb lymphatic systems in rats with detours present after lymphatic flow blockage

In the present study, we aimed to identify the normal hindlimb lymphatic systems in rats and compare them with the detours after lymphatic flow blockage. The lymphatic systems of the hindlimbs of normal rats were investigated via lymphography using a near-infrared fluorescence imaging system. The lymphatic vessels were stained using Evans Blue. The lymphatic flow was blocked through lymphatic vessel ligation combined with inguinal and popliteal lymph node dissection. Detours that appeared after 30 days were visualized using lymphography and immunostaining with anti-podoplanin antibodies. Three main results were obtained in the present study. First, the deep medial system, the superficial medial system, a connection between the superficial and deep medial lymphatic systems, and the superficial lateral system, were elucidated. Second, three types of detours, namely the detour of the lateral abdomen, the detour to the lymphatic vessel near the midline of the abdomen, and the detour to the contralateral inguinal lymph node, were identified after lymphatic flow blockage. Lastly, detours were located in the fatty layer above the panniculus carnosus muscle and their lumina were wide. The histology suggested that the detour was a pre-collecting lymphatic vessel. Lymphatic routes in the rat hindlimbs after lymphatic flow blockage were different from those of the normal rat lymphatic system. It was suggested that the detour is a pre-collecting lymphatic vessel and that encouraging its development may be a new method of simple lymphatic drainage.

Recent Advances in Fluorescence Imaging of Pulmonary Fibrosis in Animal Models

Pulmonary fibrosis (PF) is a lung disease that may cause impaired gas exchange and respiratory failure while being difficult to treat. Rapid, sensitive, and accurate detection of lung tissue and cell changes is essential for the effective diagnosis and treatment of PF. Currently, the commonly-used high-resolution computed tomography (HRCT) imaging has been challenging to distinguish early PF from other pathological processes in the lung structure. Magnetic resonance imaging (MRI) using hyperpolarized gases is hampered by the higher cost to become a routine diagnostic tool. As a result, the development of new PF imaging technologies may be a promising solution. Here, we summarize and discuss recent advances in fluorescence imaging as a talented optical technique for the diagnosis and evaluation of PF, including collagen imaging, oxidative stress, inflammation, and PF-related biomarkers. The design strategies of the probes for fluorescence imaging (including multimodal imaging) of PF are briefly described, which can provide new ideas for the future PF-related imaging research. It is hoped that this review will promote the translation of fluorescence imaging into a clinically usable assay in PF.

Deep-skin multiphoton microscopy of lymphatic vessels excited at the 1700-nm window in vivo

Visualization of lymphatic vessels is key to the understanding of their structure, function, and dynamics. Multiphoton microscopy (MPM) is a potential technology for imaging lymphatic vessels, but tissue scattering prevents its deep penetration in skin. Here we demonstrate deep-skin MPM of the lymphatic vessels in mouse hindlimb in vivo, excited at the 1700 nm window. Our results show that with contrast provided by indocyanine green (ICG), 2-photon fluorescence (2PF) imaging enables noninvasive imaging of lymphatic vessels 300 μm below the skin surface, visualizing both its structure and contraction dynamics. Simultaneously acquired second-harmonic generation (SHG) and third-harmonic generation (THG) images visualize the local environment in which the lymphatic vessels reside. After removing the surface skin layer, 2PF and THG imaging visualize finer structures of the lymphatic vessels: most notably, the label-free THG imaging visualizes lymphatic valves and their open-and-close dynamics in real time. MPM excited at the 1700-nm window thus provides a promising technology for the study of lymphatic vessels.

Lymphatic regeneration after implantation of aligned nanofibrillar collagen scaffolds: Preliminary preclinical and clinical results

BACKGROUND

We tested our hypothesis that implantation of aligned nanofibrillar collagen scaffolds (BioBridge™) can both prevent and reduce established lymphedema in the rat lymphedema model. Our authors report clinical cases that demonstrate new lymphatic formation guided by BioBridge™ as seen by near-infrared (NIR) fluoroscopy and magnetic resonance (MR) lymphography.

METHODS

A rat lymphedema model was utilized. A prevention group received implantation of BioBridge™ immediately after lymphadenectomy. A lymphedema group received implantation of BioBridge™ with autologous adipose-derived stem cells (ADSC; treatment group) or remained untreated (control group). All subjects were observed for 4 months after lymphadenectomy. The hindlimb change was evaluated using computed tomography-based volumetric analysis. Lymphagiogenesis was assessed by indocyanine green (ICG) lymphography.

RESULTS

Animals in the treatment group showed a reduction in affected limb volume. Animals in the prevention group showed no increase in the affected limb volume. ICG fluoroscopy demonstrated lymph flow and formation of lymphatics toward healthy lymphatics.

CONCLUSIONS

In the rat lymphedema model, implantation of BioBridge™ at the time of lymph node removal prevents the development of lymphedema. Treatment of established lymphedema with the BioBridge™ and ADSC reduces lymphedema. New lymphatic vessels are demonstrated by NIR fluoroscopy and MR lymphography. These findings have implications for the treatment of lymphedema in human subjects.

Lymphatic injury alters the contractility and mechanosensitivity of collecting lymphatics to intermittent pneumatic compression

KEY POINTS

We present the first in vivo evidence that lymphatic contraction can entrain with an external oscillatory mechanical stimulus. Lymphatic injury can alter collecting lymphatic contractility, but not much is known about how its mechanosensitivity to external pressure is affected, which is crucial given the current pressure application methods for treating lymphoedema. We show that oscillatory pressure waves (OPW), akin to intermittent pneumatic compression (IPC) therapy, optimally entrain lymphatic contractility and modulate function depending on the frequency and propagation speed of the OPW. We show that the OPW-induced entrainment and contractile function in the intact collecting lymphatics are enhanced 28 days after a contralateral lymphatic ligation surgery. The results show that IPC efficacy can be improved through proper selection of OPW parameters, and that collecting lymphatics adapt their function and mechanosensitivity after a contralateral injury, switching their behaviour to a pump-like configuration that may be more suited to the altered microenvironment.

ABSTRACT

Intermittent pneumatic compression (IPC) is commonly used to control the swelling due to lymphoedema, possibly modulating the collecting lymphatic function. Lymphoedema causes lymphatic contractile dysfunction, but the consequent alterations in the mechanosensitivity of lymphatics to IPC is not known. In the present work, the spatiotemporally varying oscillatory pressure waves (OPW) generated during IPC were simulated to study the modulation of lymphatic function by OPW under physiological and pathological conditions. OPW with three temporal frequencies and three propagation speeds were applied to rat tail collecting lymphatics. The entrainment of the lymphatics to OPW was significantly higher at a frequency of 0.05 Hz compared with 0.1 Hz and 0.2 Hz (P = 0.0054 and P = 0.014, respectively), but did not depend on the OPW propagation speed. Lymphatic function was significantly higher at a frequency of 0.05 Hz and propagation speed of 2.55 mm/s (P = 0.015). Exogenous nitric oxide was not found to alter OPW-induced entrainment. A contralateral lymphatic ligation surgery was performed to simulate partial lymphatic injury in rat tails. The intact vessels showed a significant increase in entrainment to OPW, 28 days after ligation (compared with sham) (P = 0.016), with a similar increase in lymphatic transport function (P = 0.0029). The results suggest an enhanced mechanosensitivity of the lymphatics, along with a transition to a pump-like behaviour, in response to a lymphatic injury. These results enhance our fundamental understanding of how lymphatic mechanosensitivity assists the coordination of lymphatic contractility and how this might be leveraged in IPC therapy.

Altered Lymphatic Vessel Anatomy and Markedly Diminished Lymph Clearance in Affected Hands of Patients With Active Rheumatoid Arthritis

OBJECTIVE

To assess differences between lymphatic function in the affected hands of rheumatoid arthritis (RA) patients with active synovitis and that of healthy controls, using indocyanine green (ICG) dye and near-infrared (NIR) imaging.

METHODS

NIR imaging of the hands of 8 patients with active RA and 13 healthy controls was performed following web space injection of 0.1 ml of 100 μM ICG. The percentage of ICG retention in the web spaces was determined by NIR imaging at baseline and at 7 days (±1 day) after the initial injections; image analysis provided contraction frequency. ICG+ lymphatic vessel (LV) length and branching architecture were assessed.

RESULTS

Retention of ICG in RA hands was higher compared to controls (P < 0.01). The average contraction frequency of ICG+ LVs in RA patients and in controls did not differ (mean ± SD 0.53 ± 0.39 contractions/minute versus 0.51 ± 0.35 contractions/minute). Total ICG+ LV length in RA hands was lower compared to healthy controls (58.3 ± 15.0 cm versus 71.4 ± 16.1 cm; P < 0.001), concomitant with a decrease in the number of ICG+ basilic LVs in the hands of RA patients (P < 0.05).

CONCLUSION

Lymphatic drainage in the hands of RA patients with active disease was reduced compared to controls. This reduction was associated with a decrease in total length of ICG+ LVs on the dorsal surface of the hands, which continued to contract at a similar rate to that observed in controls. These findings provide a plausible mechanism for exacerbation of synovitis and joint damage, specifically the accumulation and retention of inflammatory cells and catabolic factors in RA joints due to impaired efferent lymphatic flow. NIR/ICG imaging of RA hands is feasible and warrants formal investigation as a primary outcome measure for arthritis disease severity and/or persistence in future clinical trials.

Combining superficial and deep lymphovenous anastomosis for lymphedema treatment: Preliminary results

BACKGROUND

Superficial lymphovenous anastomosis (LVA) is a widely accepted procedure for treatment of mild-to-moderate lymphedema throughout the body. Anyway, not always are the superficial lymphatic vessels suitable for the anastomosis nor do they provide a sufficient drainage to significantly improve the condition. The continuous progress of supermicrosurgical technique over the last few years and the recent anatomical researches about the deep lymphatic network opened new perspectives for those lymphedema cases refractory to conventional procedures. Resorting to deep lymphatic vessels offer an additional opportunity to further improve the result obtained by means of superficial LVA. The aim of this report is to describe our experience treating lymphedema with superficial and deep lymphatic vessels LVA.

PATIENTS AND METHODS

Eight female patients presenting secondary (seven cases) and primary (one case) lymphedema, previously treated by means of multiple superficial LVAs, were considered eligible for deep lymphatics surgery to further improve their results. The affected area was the upper limb in one case and the lower limbs in seven cases. All the patients were evaluated preoperatively and postoperatively resorting to Campisi criteria. Four cases were initially classified as stage III, two stage IV, and two stage II. Five patients received deep LVA in the groin, two patients in the ankle along the posterior tibial artery and one in the wrist along the radial artery.

RESULTS

In all eight patients both subjective and objective improvements of the condition were reported with decrease of swelling and relief from heaviness sensation. The postoperative course was always uneventful and at the 9 months follow up none of the patients presented recurrence of the disease, even with the complete removal of compressive therapy.

CONCLUSIONS

Deep lymphatic vessels LVA might represent a valid alternative to the superficial ones to treat lymphedema when previous results are not satisfactory nor when no superficial lymphatic vessels are available for anastomosis.

Evaluation of lymphatic flow pattern using indocyanine green fluorescence imaging in a highly metastatic mouse model

Recently, the feasibility of real‐time indocyanine green (ICG) fluorescence imaging–guided complete mesocolic excision in colon cancer surgery has been demonstrated; however, its application to the evaluation of lymphatic flow in widespread lymph node metastasis is uncertain. This study aimed to evaluate lymphatic flow using the real‐time ICG fluorescence imaging. A mouse model of subcutaneous inoculation of BJMC3879Luc2 cells, which have been demonstrated to highly metastasize to the lymph nodes, was used as an evaluation model. Tumor growth and lymphatic flow were monitored weekly by bioluminescent imaging and near‐infrared (NIR) fluorescence imaging, respectively. After sacrificing the mice, lymph node metastases were evaluated by bioluminescent imaging and histopathology. Lymphatic flows in a model of high lymph node metastasis were evaluated using NIR fluorescence imaging. Pathological metastases of bilateral axillary, femoral, and para‐aortic lymph nodes were detected in all inoculated mice (100%: 5/5). Real‐time NIR fluorescence imaging showed the primary lymphatic vessels staining through the metastatic lymph nodes as before the inoculation of the cancer cells. Hitherto, it has been considered that lymphatic flow was changed using the bypass pathway due to occlusion of the primary lymphatic vessels. In this presented study, real‐time ICG fluorescence imaging showed no changes in lymphatic flow after lymph node metastasis. Our results suggest that real‐time ICG fluorescence imaging may have potential for the guidance of colon cancer surgery in cases of widespread lymph node 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.

Multiplexed NIR-II Probes for Lymph Node-Invaded Cancer Detection and Imaging-Guided Surgery

Tumor-lymph node (LN) metastasis is the dominant prognostic factor for tumor staging and therapeutic decision-making. However, concurrently visualizing metastasis and performing imaging-guided lymph node surgery is challenging. Here, a multiplexed-near-infrared-II (NIR-II) in vivo imaging system using nonoverlapping NIR-II probes with markedly suppressed photon scattering and zero-autofluorescence is reported, which enables visualization of the metastatic tumor and the tumor metastatic proximal LNs resection. A bright and tumor-seeking donor-acceptor-donor (D-A-D) dye, IR-FD, is screened for primary/metastatic tumor imaging in the NIR-IIa (1100-1300 nm) window. This optimized D-A-D dye exhibits greatly improved quantum yield of organic D-A-D fluorophores in aqueous solutions (≈6.0%) and good in vivo performance. Ultrabright PbS/CdS core/shell quantum dots (QDs) with dense polymer coating are used to visualize cancer-invaded sentinel LNs in the NIR-IIb (>1500 nm) window. Compared to clinically used indocyanine green, the QDs show superior brightness and photostability (no obvious bleaching even after continuous laser irradiation for 5 h); thus, only a picomolar dose is required for sentinel LNs detection. This combination of dual-NIR-II image-guided surgery can be performed under bright light, adding to its convenience and appeal in clinical use.

Pre-collecting lymphatic vessels form detours following obstruction of lymphatic flow and function as collecting lymphatic vessels

Background

Previously, we showed that lymphatic vessels (LVs) formed detours after lymphatic obstruction, contributing to preventing lymphedema. In this study, we developed detours using lymphatic ligation in mice and we identified the detours histologically.

Methods and results

Under anesthesia, both hindlimbs in mice were subcutaneously injected with Evans blue dye to detect LVs. We tied the right collecting LV on the abdomen that passes through the inguinal lymph node (LN) at two points. The right and left sides comprised the operation and sham operation sides, respectively. Lymphography was performed to investigate the lymph flow after lymphatic ligation until day 30, using a near-infrared fluorescence imaging system. Anti-podoplanin antibody and 5-ethynyl-2’-deoxyuridine (EdU) were used to detect LVs and lymphangiogenesis. Within 30 days, detours had developed in 62.5% of the mice. Detours observed between two ligation sites were enlarged and irregular in shape. Podoplanin⁺ LVs, which were located in the subcutaneous tissue of the upper panniculus carnosus muscle, connected to collecting LVs at the upper portion from the cranial ligation site and at the lower portion from the caudal ligation site. EdU⁺ cells were not observed in these detours. The sham operation side showed normal lymph flow and did not show enlarged pre-collecting LVs until day 30.

Conclusions

Detours after lymphatic ligation were formed not by lymphangiogenesis but through an enlargement of pre-collecting LVs that functioned as collecting LVs after lymphatic ligation. Further studies are required to explore the developmental mechanism of the lymphatic detour for treatment and effective care of lymphedema in humans.

In Vivo Optical Performance of a New Class of Near-Infrared-Emitting Conjugated Polymers: Borylated PF8-BT

Borylated poly(fluorene-benzothiadiazoles) (PF8-BT) are π-conjugated polymers (CPs) with deep-red/near-infrared (NIR) absorption and emission profiles suitable for in vivo optical imaging. A fully borylated PF8-BT derivative (P4) was encapsulated in pegylated poly(lactic-co-glycolic acid) (PEG-PLGA) nanoparticles and compared with a reference NIR-emitting CP (PCPDTBT) or indocyanine green (ICG). All formulations satisfied quality requirements for parenterally administered diagnostics. P4 nanoparticles had higher quantum yield (2.3%) than PCPCDTBT (0.01%) or ICG nanoparticles (1.1%). The signal/background ratios (SBRs) of CP systems P4 and PCPDTBT in a phantom mouse (λ_em = 820 nm) increased linearly with fluorophore mass (12.5-100 μg/mL), while the SBRs of ICG decreased above 25 μg/mL. P4 nanoparticles experienced <10% photobleaching over 10 irradiations (PCPDTBT: ∼25% and ICG: >44%). In a mouse tumor xenograft model, P4 nanoparticles showed a 5-fold higher SBR than PCPDTBT particles with fluorophore accumulation in the liver > spleen > tumor. Blood chemistry and tissue histology showed no abnormalities compared to untreated animals after a single administration.

Arterial Lymphatics in Atherosclerosis: Old Questions, New Insights, and Remaining Challenges

The lymphatic network is well known for its role in the maintenance of tissue fluid homeostasis, absorption of dietary lipids, trafficking of immune cells, and adaptive immunity. Aberrant lymphatic function has been linked to lymphedema and immune disorders for a long time. Discovery of lymphatic cell markers, novel insights into developmental and postnatal lymphangiogenesis, development of genetic mouse models, and the introduction of new imaging techniques have improved our understanding of lymphatic function in both health and disease, especially in the last decade. Previous studies linked the lymphatic vasculature to atherosclerosis through regulation of immune responses, reverse cholesterol transport, and inflammation. Despite extensive research, many aspects of the lymphatic circulation in atherosclerosis are still unknown and future studies are required to confirm that arterial lymphangiogenesis truly represents a therapeutic target in patients with cardiovascular disease. In this review article, we provide an overview of factors and mechanisms that regulate lymphangiogenesis, summarize recent findings on the role of lymphatics in macrophage reverse cholesterol transport, immune cell trafficking and pathogenesis of atherosclerosis, and present an overview of pharmacological and genetic strategies to modulate lymphatic vessel density in cardiovascular tissue.

PEGylation Regulates Self-Assembled Small-Molecule Dye-Based Probes from Single Molecule to Nanoparticle Size for Multifunctional NIR-II Bioimaging

To date, small-molecule dye-based probes have been at the forefront of research in biomedical imaging, especially in the second near-infrared (NIR-II) window (1.0-1.7 µm). However, how to precisely regulate the synthesized size of NIR-II organic dye-based probes remains challenging. Moreover, systematic studies on whether the size of NIR-II probes affects optical/pharmacokinetic properties are still rare. Here, an ingenious PEGylation strategy is developed to regulate the self-assembly size of organic dye-based (CH1055 scaffold) NIR-II probes (SCH1-SCH4) from nanoparticles to the single molecule, and the relationship between their size and chemical/physical properties is thoroughly investigated. Based on their own merits, nanoprobe SCH1 (≈170 nm), with outstanding fluorescent brightness (quantum yield ≈0.14%), performs accurate tracing of the lymphatic system as well as identification of vessel networks in mice brains with excellent signal-to-background ratio images. Meanwhile, rapidly excreted SCH4, showing fast and high passive liver tumor uptake and promising tumor/normal tissue ratios (>7), is capable of facilitating precise image-guided tumor surgery, and also demonstrates the first example of the assessment of liver fibrosis in the NIR-II window.