High-resolution 3D volumetry versus conventional measuring techniques for the assessment of experimental lymphedema in the mouse hindlimb

3D scanner's potential as a novel tool for lymphedema measurement in mouse hindlimb models

Lymphedema is characterized by persistent swelling due to impaired lymphatic function and presents significant challenges in both research and clinical settings. Traditional contact-based measurement techniques such as paw thickness and circumferential measurements using calipers or silk thread are useful but limited by observer variability and measurement accuracy. Non-contact methods, including various imaging techniques, offer improvements but often at higher cost and complexity. In this study, we address the need for a more reliable, cost-effective, and non-invasive method for assessing lymphedema in mouse models. Here we show that 3D scanning technology can enhance the measurement of lymphedema in a mouse hindlimb model. Our results indicate that 3D scanners provide more consistent measurements with lower variability compared with conventional methods and without the need for direct contact, which could potentially alter the measurement outcomes. The findings of this study suggest that 3D scanning could replace traditional methods, offering a more standardized and less subjective tool for lymphedema research in the near future. This technology would not only improve upon conventional methods but also extend the capabilities for detailed anatomical analyses in small animal models, which could have implications for other areas of biomedical research.

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.

Methods of ex vivo analysis of tissue status in vascularized composite allografts

Vascularized composite allotransplantation can improve quality of life and restore functionality. However, the complex tissue composition of vascularized composite allografts (VCAs) presents unique clinical challenges that increase the likelihood of transplant rejection. Under prolonged static cold storage, highly damage-susceptible tissues such as muscle and nerve undergo irreversible degradation that may render allografts non-functional. Skin-containing VCA elicits an immunogenic response that increases the risk of recipient allograft rejection. The development of quantitative metrics to evaluate VCAs prior to and following transplantation are key to mitigating allograft rejection. Correspondingly, a broad range of bioanalytical methods have emerged to assess the progression of VCA rejection and characterize transplantation outcomes. To consolidate the current range of relevant technologies and expand on potential for development, methods to evaluate ex vivo VCA status are herein reviewed and comparatively assessed. The use of implantable physiological status monitoring biochips, non-invasive bioimpedance monitoring to assess edema, and deep learning algorithms to fuse disparate inputs to stratify VCAs are identified.

Lymphatic channel sheet of polydimethylsiloxane for preventing secondary lymphedema in the rat upper limb model

Secondary lymphedema is a severe complication of cancer treatment, but there is no effective curative method yet. Lymph node dissection and radiation therapy for cancer treatment may lead to secondary lymphedema, which is a chronic disease induced by malfunction of lymphatic flow. The lymphatic channel sheet (LCS) is an artificial micro-fluidic structure that was fabricated with polydimethylsiloxane to maintain lymphatic flow and induce lymphangiogenesis. The structure has two-dimensional multichannels that increase the probability of lymphangiogenesis and allow for relatively easy application. We verified the efficacy of the lymphatic channel sheet through macroscopic and microscopic observation in small animal models, which underwent brachial lymph node dissection and irradiation. The lymphatic channel sheet enabled the successful transport of lymphatic fluid from the distal to the proximal area in place of the removed brachial lymph nodes. It prevented swelling and abnormal lymphatic drainage during the follow-up period. Lymphangiogenesis was also identified inside the channel by histological analysis after 8 weeks. According to these experimental results, we attest to the roles of the lymphatic channel sheet as a lymphatic pathway and scaffold in the rat upper limb model of secondary lymphedema. The lymphatic channel sheet maintained lymphatic flow after lymph node dissection and irradiation in an environment where lymph flow is cut off. It also relieved symptoms of secondary lymphedema by providing a lymph-friendly space and inducing lymphangiogenesis.

Current Advancements in Animal Models of Postsurgical Lymphedema: A Systematic Review

Significance: Secondary lymphedema is a debilitating disease caused by lymphatic dysfunction characterized by chronic swelling, dysregulated inflammation, disfigurement, and compromised wound healing. Since there is no effective cure, animal model systems that support basic science research into the mechanisms of secondary lymphedema are critical to advancing the field. Recent Advances: Over the last decade, lymphatic research has led to the improvement of existing animal lymphedema models and the establishment of new models. Although an ideal model does not exist, it is important to consider the strengths and limitations of currently available options. In a systematic review adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we present recent developments in the field of animal lymphedema models and provide a concise comparison of ease, cost, reliability, and clinical translatability. Critical Issues: The incidence of secondary lymphedema is increasing, and there is no gold standard of treatment or cure for secondary lymphedema. Future Directions: As we iterate and create animal models that more closely characterize human lymphedema, we can achieve a deeper understanding of the pathophysiology and potentially develop effective therapeutics for patients.

Microcomputed tomography versus plethysmometer and electronic caliper in the measurements of lymphedema in the hindlimb of mice

Lymphedema affects 20% of women diagnosed with breast cancer. It is a pathology with no known cure. Animal models are essential to explore possible treatments to understand and potentially cure lymphedema. The rodent hindlimb lymphedema model is one of the most widely used. Different modalities have been used to measure lymphedema in the hindlimb of mice, and these are generally poorly assessed in terms of the interrater agreement; thus, there could be a risk of measuring bias and poor reproducibility. We examined the interrater agreement of µCT-scans, electronic caliper thickness of the paw and plethysmometer in the measurement of lymphedema in the hindlimb of mice. Three independent raters assessed 24 C57BL6 mice using these three modalities four times (week 1, 2, 4 and 8) with a total of 96 samples. The mean interrater differences were then calculated. The interrater agreement was highest in the µCT-scans, with an extremely low risk of measurement bias. The interrater agreement in the plethysmometer and electronic caliper was comparable with a low to moderate risk of measurement bias. The µCT-scanner should be used whenever possible. The electronic caliper should only be used if there is no µCT-scanner available. The plethysmometer should not be used in rodents of this size.

Adipose tissue-derived microvascular fragments promote lymphangiogenesis in a murine lymphedema model

Chronic lymphedema after cancer treatment is common and there is still no cure for this disease. We herein investigated the lymphangiogenic capacity of adipose tissue-derived microvascular fragments (MVF), which contain stem cells and lymphatic vessel fragments. Secondary lymphedema was induced in the hindlimbs of C57BL/6J mice. Green fluorescence protein (GFP)+ MVF were isolated from transgenic C57BL/6Tg (CAG-EGFP)1Osb/J mice, suspended in collagen hydrogel, and injected in the lymphadenectomy defect of wild-type animals. This crossover model allowed the detection of MVF-derived blood and lymphatic vessels after transplantation. The MVF group was compared with animals receiving collagen hydrogel only or a sham intervention. Lymphangiogenic effects were analyzed using volumetry, magnetic resonance (MR) lymphography, histology, and immunohistochemistry. MVF injection resulted in reduced hindlimb volumes when compared to non-treated controls. MR lymphography revealed lymphatic regeneration with reduced dermal backflow after MVF treatment. Finally, MVF transplantation promoted popliteal angiogenesis and lymphangiogenesis associated with a significantly increased microvessel and lymphatic vessel density. These findings indicate that MVF transplantation represents a promising approach to induce therapeutic lymphangiogenesis.

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.

Comparison between stromal vascular fraction and adipose derived stem cells in a mouse lymphedema model

Background: Lymphedema is one of the most common complications following breast cancer. Axillary lymph node dissection and radiotherapy are two well-known risk factors resulting in either removal or damage to the lymph nodes. As stem cells are known for their regenerative capabilities, they could theoretically repair/restore the damaged lymph vessels leading to a decrease in lymphedema.Methods: We evaluated the treatment of SVF and ASC on a mouse lymphedema model. Forty-five mice were allocated into three groups containing 15 mice each. The SVF group was injected with 100 μl containing 1 × 10⁶ SVF, the ASC group with 100 μl ml containing 1 × 10⁶ ASC and the NS with 100 μl ml of NS. Volumes of the mice were assessed weekly by μCT hindlimb volumetry for a total of 8 weeks. Lymph vessel morphometry was assessed by cross-sections of both hindlimbs stained for anti-LYVE1. Lymphatic function was assessed by lymphatic clearance.Results: The volume change between the groups was non-significant throughout all 8 weeks. The immunohistochemistry showed a statistically significant difference between the hindlimbs in ASC vs. NS group p = 0.032, 95% CI [-2121, -103].Conclusion: The volume of the hindlimbs showed that treatment with SVF or ASC yielded very similar results compared to the control group when assessed after 8 weeks. In week two the biggest difference between ASC and NS was seen but the difference diminished during the 8 weeks. The secondary outcomes showed that the lymph vessel lumen decreased when treated with ASC compared to the control group. Lymphoscintigraphy yielded non-significant results.

Quantification of tissue volume in the hindlimb of mice using microcomputed tomography images and analysing software

When studying illnesses that cause disturbance in volume such as lymphedema, reliable quantification of tissue volume is important. Lymphedema results in swelling and enlargement of extremities and can be both physically and psychologically stressful to the patient. Experiments in rodent models provide a cost-effective research platform and are important for preclinical research on lymphedema. When performing such research, it can be crucial to measure the changes in tissue volume. Researchers must ensure that the risk of measurement error, when measuring the tissue volume, is as low as possible. The main goal of this article was to perform a comprehensive examination of the intra- and interrater agreement and hereby assess the risk of measurement error when using microcomputed tomography (µCT) images to measure hindlimb volume. We examined the agreement between four raters with different levels of prior experience and found that the risk of measurement error is extremely low when using this method. The main limitation of this method is that it is relatively expensive and time-consuming. The main advantages of this method are that it is easily learned and that it has a high intra- and interrater agreement, even for raters with no prior measuring experience.

IGF2 mRNA Binding Protein 2 Transgenic Mice Are More Prone to Develop a Ductular Reaction and to Progress Toward Cirrhosis

The insulin-like growth factor 2 (IGF2) mRNA binding proteins (IMPs/IGF2BPs) IMP1 and 3 are regarded as oncofetal proteins, whereas the hepatic IMP2 expression in adults is controversially discussed. The splice variant IMP2-2/p62 promotes steatohepatitis and hepatocellular carcinoma. Aim of this study was to clarify whether IMP2 is expressed in the adult liver and influences progression toward cirrhosis. IMP2 was expressed at higher levels in embryonic compared to adult tissues as quantified in embryonic, newborn, and adult C57BL/6J mouse livers and suggested by analysis of publicly available human data. In an IMP2-2 transgenic mouse model microarray and qPCR analyses revealed increased expression of liver progenitor cell (LPC) markers Bex1, Prom1, Spp1, and Cdh1 indicating a de-differentiated liver cell phenotype. Induction of these LPC markers was confirmed in human cirrhotic tissue datasets. The LPC marker SPP1 has been described to play a major role in fibrogenesis. Thus, DNA methylation was investigated in order to decipher the regulatory mechanism of Spp1 induction. In IMP2-2 transgenic mouse livers single CpG sites were differentially methylated, as quantified by amplicon sequencing, whereas human HCC samples of a human publicly available dataset showed promoter hypomethylation. In order to study the impact of IMP2 on fibrogenesis in the context of steatohepatitis wild-type or IMP2-2 transgenic mice were fed either a methionine-choline deficient (MCD) or a control diet for 2-12 weeks. MCD-fed IMP2-2 transgenic mice showed a higher incidence of ductular reaction (DR), accompanied by hepatic stellate cell activation, extracellular matrix (ECM) deposition, and induction of the LPC markers Spp1, Cdh1, and Afp suggesting the occurrence of de-differentiated cells in transgenic livers. In human cirrhotic samples IMP2 overexpression correlated with LPC marker and ECM component expression. Progression of liver disease was induced by combined MCD and diethylnitrosamine (DEN) treatment. Combined MCD-DEN treatment resulted in shorter survival of IMP2-2 transgenic compared to wild-type mice. Only IMP2-2 transgenic livers progressed to cirrhosis, which was accompanied by strong DR. In conclusion, IMP2 is an oncofetal protein in the liver that promotes DR characterized by de-differentiated cells toward steatohepatitis-associated cirrhosis development with poor survival.

Magnetic Resonance Lymphography at 9.4 T Using a Gadolinium-Based Nanoparticle in Rats: Investigations in Healthy Animals and in a Hindlimb Lymphedema Model

OBJECTIVES

Magnetic resonance lymphography (MRL) in small animals is a promising but challenging tool in preclinical lymphatic research. In this study, we compared the gadolinium (Gd)-based nanoparticle AGuIX with Gd-DOTA for interstitial MRL in healthy rats and in a chronic rat hindlimb lymphedema model.

MATERIALS AND METHODS

A comparative study with AGuIX and Gd-DOTA for interstitial MRL was performed in healthy Lewis rats (n = 6). For this purpose, 75 μL of 3 mM AGuIX (containing 30 mM Gd-DOTA side residues) and 75 μL 30 mM Gd-DOTA were injected simultaneously in the right and left hindlimbs. Repetitive high-resolution, 3-dimensional time-of-flight gradient recalled echo MRL sequences were acquired over a period of 90 minutes using a 9.4 T animal scanner. Gadofosveset-enhanced MR angiography and surgical dissection after methylene blue injection served as supportive imaging techniques. In a subsequent proof-of-principle study, AGuIX-based MRL was investigated in a hindlimb model of chronic lymphedema (n = 4). Lymphedema of the right hindlimbs was induced by means of popliteal and inguinal lymphadenectomy and irradiation with 20 Gy. The nonoperated left hindlimbs served as intraindividual controls. Six, 10, and 14 weeks after lymphadenectomy, MRL investigations were performed to objectify lymphatic reorganization. Finally, skin samples of the lymphedematous and the contralateral control hindlimbs were analyzed by means of histology and immunohistochemistry.

RESULTS

AGuIX-based MRL resulted in high-resolution anatomical depiction of the rodent hindlimb lymphatic system. Signal-to-noise ratio and contrast-to-noise ratio of the popliteal lymph node were increased directly after injection and remained significantly elevated for up to 90 minutes after application. AGuIX provided significantly higher and prolonged signal intensity enhancement as compared with Gd-DOTA. Furthermore, AGuIX-based MRL demonstrated lymphatic regeneration in the histopathologically verified chronic lymphedema model. Collateral lymphatic vessels were detectable 6 weeks after lymphadenectomy.

CONCLUSIONS

This study demonstrates that AGuIX is a suitable contrast agent for preclinical interstitial MRL in rodents. AGuIX yields anatomical imaging of lymphatic vessels with diameters greater than 200 μm. Moreover, it resides in the lymphatic system for a prolonged time. AGuIX may therefore facilitate high-resolution MRL-based analyses of the lymphatic system in rodents.

Deep brain stimulation during early adolescence prevents microglial alterations in a model of maternal immune activation

In recent years schizophrenia has been recognized as a neurodevelopmental disorder likely involving a perinatal insult progressively affecting brain development. The poly I:C maternal immune activation (MIA) rodent model is considered as a neurodevelopmental model of schizophrenia. Using this model we and others demonstrated the association between neuroinflammation in the form of altered microglia and a schizophrenia-like endophenotype. Therapeutic intervention using the anti-inflammatory drug minocycline affected altered microglia activation and was successful in the adult offspring. However, less is known about the effect of preventive therapeutic strategies on microglia properties. Previously we found that deep brain stimulation of the medial prefrontal cortex applied pre-symptomatically to adolescence MIA rats prevented the manifestation of behavioral and structural deficits in adult rats. We here studied the effects of deep brain stimulation during adolescence on microglia properties in adulthood. We found that in the hippocampus and nucleus accumbens, but not in the medial prefrontal cortex, microglial density and soma size were increased in MIA rats. Pro-inflammatory cytokine mRNA was unchanged in all brain areas before and after implantation and stimulation. Stimulation of either the medial prefrontal cortex or the nucleus accumbens normalized microglia density and soma size in main projection areas including the hippocampus and in the area around the electrode implantation. We conclude that in parallel to an alleviation of the symptoms in the rat MIA model, deep brain stimulation has the potential to prevent the neuroinflammatory component in this disease.

An Important Role of VEGF-C in Promoting Lymphedema Development

Secondary lymphedema is a common complication after cancer treatment, but the pathomechanisms underlying the disease remain unclear. Using a mouse tail lymphedema model, we found an increase in local and systemic levels of the lymphangiogenic factor vascular endothelial growth factor (VEGF)-C and identified CD68⁺ macrophages as a cellular source. Surprisingly, overexpression of VEGF-C in a transgenic mouse model led to aggravation of lymphedema with increased immune cell infiltration and vascular leakage compared with wild-type littermates. Conversely, blockage of VEGF-C by overexpression of soluble VEGF receptor-3 reduced edema development, diminishing inflammation and blood vascular leakage. Similar findings were obtained in a hind limb lymph node excision lymphedema model. Flow cytometry analyses and immunofluorescence stainings in lymphedematic tissue showed that VEGF receptor-3 expression was restricted to lymphatic endothelial cells. Our data suggest that endogenous VEGF-C causes blood vascular leakage and fluid influx into the tissue, thus actively contributing to edema formation. These data may provide the basis for future clinical therapeutic approaches.