CD112 Supports Lymphatic Migration of Human Dermal Dendritic Cells

Dendritic cell (DC) migration from peripheral tissues via afferent lymphatic vessels to draining lymph nodes (dLNs) is important for the organism's immune regulation and immune protection. Several lymphatic endothelial cell (LEC)-expressed adhesion molecules have thus far been found to support transmigration and movement within the lymphatic vasculature. In this study, we investigated the contribution of CD112, an adhesion molecule that we recently found to be highly expressed in murine LECs, to this process. Performing in vitro assays in the murine system, we found that transmigration of bone marrow-derived dendritic cells (BM-DCs) across or adhesion to murine LEC monolayers was reduced when CD112 was absent on LECs, DCs, or both cell types, suggesting the involvement of homophilic CD112-CD112 interactions. While CD112 was highly expressed in murine dermal LECs, CD112 levels were low in endogenous murine dermal DCs and BM-DCs. This might explain why we observed no defect in the in vivo lymphatic migration of adoptively transferred BM-DCs or endogenous DCs from the skin to dLNs. Compared to murine DCs, human monocyte-derived DCs expressed higher CD112 levels, and their migration across human CD112-expressing LECs was significantly reduced upon CD112 blockade. CD112 expression was also readily detected in endogenous human dermal DCs and LECs by flow cytometry and immunofluorescence. Upon incubating human skin punch biopsies in the presence of CD112-blocking antibodies, DC emigration from the tissue into the culture medium was significantly reduced, indicating impaired lymphatic migration. Overall, our data reveal a contribution of CD112 to human DC migration.

Involvement of the Macrophage Migration Inhibitory Factor (MIF) in Lipedema

Lipedema is a chronic disorder that mainly affects women. It is often misdiagnosed, and its etiology remains unknown. Recent research indicates an accumulation of macrophages and a shift in macrophage polarization in lipedema. One known protein superfamily that contributes to macrophage accumulation and polarization is the macrophage migration inhibitory factor (MIF) family. MIF-1 and MIF-2 are ubiquitously expressed and also regulate inflammatory processes in adipose tissue. In this study, the expression of MIF-1, MIF-2 and CD74-a common receptor for both cytokines-was analyzed in tissue samples of 11 lipedema and 11 BMI-matched, age-matched and anatomically matched control patients using qPCR and immunohistochemistry (IHC). The mRNA expression of MIF-1 (mean 1.256; SD 0.303; p = 0.0485) and CD74 (mean 1.514; SD 0.397; p = 0.0097) were significantly elevated in lipedema patients, while MIF-2 expression was unaffected (mean 1.004; SD 0.358; p = 0.9718). The IHC analysis corroborated the results for CD74 expression on a cellular level. In conclusion, our results provide first evidence for a potential involvement of the MIF family, presumably via the MIF-1-CD74 axis, in lipedema.

Benefits of robotic-assisted lymphatic microsurgery in deep anatomical planes

Micro- and supermicrosurgeries have become standard techniques for lymphatic reconstruction. As increasingly smaller vessels are being targeted, robotic-assisted surgery has emerged as a new approach to push reconstructive limits owing to its ability of motion scaling and providing better accessibility of deep anatomical regions. The precision of the robot is achieved at the expense of operating speed among other variables; therefore, the surgeon must weigh the enhanced dexterity against the additional operating time and cost required for the robotic surgical system itself to ensure optimal resource utilization. Here we present a case series of 8 patients who underwent robot-assisted lymphatic microsurgery for omental flap transfer to the axilla and lympho-venous anastomosis. The Symani® Surgical System was used with a conventional microscope or 3D exoscope. The use of 3D exoscope provided clear benefits in terms of surgeon positioning. Moreover, access to the recipient vessels near the thoracic wall was significantly improved with the robotic setup. In addition, suture precision was excellent, resulting in patent anastomoses. Operating time for anastomosis was comparable to that for manual anastomosis and demonstrated a steep learning curve. The benefits of robotic systems in operating fields with good exposure require further evaluation. However, owing to longer instruments, additional stability, dexterity, and motion precision, robotic systems offer a marked advantage for operating in deep anatomical planes and on small structures. A potentially new field for the implementation of robotic surgery is central lymphatic reconstruction. Progress in terms of operating time and cost is crucial, and future research should validate the effectiveness of robotic-assisted surgery in larger clinical studies.

Characterization of the soft-tissue wall lining residual periodontal pockets and implications in periodontal wound healing

AIM

To characterize the soft-tissue wall of remaining periodontal pockets for wound healing-related parameters versus healthy gingival crevices in the same individuals.

MATERIALS AND METHODS

Gingival tissues collected from the diseased interface of pockets (GT biopsies) and from healthy gingival crevices (G biopsies) were subjected to RT2-profiler PCR Array for wound healing-related markers and network analysis of differentially expressed genes. Lymphangiogenesis-related gene expression was determined by qRT-PCR. The migration potential of mesenchymal stem cells isolated from GT biopsies (GT-MSCs) and G biopsies (G-MSCs) was evaluated by the scratch- and the transwell migration assays. The total collagen protein content was determined in GT-MSCs and G-MSCs homogenates.

RESULTS

Gene-ontology analysis on significantly upregulated genes expressed in GT biopsies revealed enrichment of several genes involved in processes related to matrix remodeling, collagen deposition, and integrin signaling. No significantly expressed genes were seen in G biopsies. Regarding lymphangiogenesis-related genes, GT biopsies demonstrated greater expression for PROX1 than G biopsies (p = 0.05). Lower migration potential (p < 0.001), yet greater production of collagen protein (p = 0.05), was found for GT-MSCs over G-MSCs.

CONCLUSION

Differential expression patterns of various molecular pathways in biopsies and cell cultures of diseased versus healthy gingival tissues indicate a potential of the former for tissue remodeling and repair.

CLINICAL RELEVANCE

In the course of periodontitis, granulation tissue is formed within a periodontal defect in an attempt to reconstruct the site. Following treatment procedures periodontal granulation tissue remains inflamed but appears to retain healing potential.

Outcome of Facial Burn Injuries Treated by a Nanofibrous Temporary Epidermal Layer

BACKGROUND

The face is commonly affected in thermal injuries, with a demand for proper recognition and the correct choice of treatment to guarantee optimal aesthetic and functional outcomes. It is highly vascularized and often heals conservatively, highlighting the particular relevance of conservative treatment modalities, many of which require daily re-applications or dressing changes, which can be painful and tedious for both the patient and the healthcare providers. Motivated by encouraging results of a novel temporary nanofibrous epidermal layer, we herein present a case series of this technology in a case series of patients suffering from facial burns and treated in our Burn Center.

PATIENTS AND METHODS

Patients with superficial partial-thickness facial burns and mixed pattern burns, which were treated with SpinCare™, an electrospun nanofibrous temporary epidermal layer, between 2019 and 2021, at our institution were analyzed retrospectively. The Manchester scar scale (MSS) and numeric rating scale (NRS) were used for scar, pain, and outcome evaluation at different time points by five independent board-certified plastic surgeons with profound experience in burn surgery.

RESULTS

Ten patients (m = 9; f = 1) were treated and evaluated retrospectively. The mean age was 38.8 ± years (SD ± 17.85). The mean healing time was 6.4 days (SD ± 1.56). The mean follow-up was 16.4 months (SD ± 11.33). The mean MSS score was 5.06 (SD ± 1.31), and the mean NRS Score for pain was significantly reduced from initially 7 to 0.875 upon application (mean (pre-application) 7 ± 0.7 and (application) 0.875 ± 1.26; p ≤ 0.0001). Patients reported a NRS score of 10 in terms of functional and cosmetic outcomes at their final follow-up appointment. No adverse effects were observed.

CONCLUSIONS

The application of a nanofibrous temporary epidermal layer such as SpinCare™ represents a relatively easy-to-use, well-tolerated, and effective alternative for the treatment of partial-thickness facial burns.

PROMs after Lymphatic Reconstructive Surgery: Is There a Correlation between Volume Reduction and Quality of Life?

Patients with upper limb lymphedema and lower limb lymphedema experience a wide range of physical and psychological symptoms that affect quality of life. The benefits of lymphatic reconstructive surgery for patients with lymphedema are undisputed. However, recording volume reduction alone may be insufficient with regard to postoperative outcome because measurements are often inadequate, depend on many factors, and do not reflect improvement in quality of life.

Methods

We conducted a prospective single center study patients receiving lymphatic reconstructive surgery. Patients received volume measurements preoperatively and at standardized postoperative intervals. To evaluate patient-reported outcomes, patients completed the following questionnaires: LYMPH-Q Upper Extremity Module, quickDASH, SF 36, Lymphoedema Functioning, Disability and Health Questionnaire for Lower Limb Lymphoedema, and Lower Extremity Functional Scale at the aforementioned intervals.

Results

We included 55 patients with upper limb lymphedema (24%) and lower limb lymphedema (73%) of lymphedema grades I-III. Patients received lymphovenous anastomosis only (23%), free vascularized lymph node transfer (35%) or a combination of both (42%). Analysis of patient-reported outcome measurements revealed improvements with respect to a broad range of complaints, particularly physical function, symptoms, and psychological well-being. There was no correlation between the extent of volume reduction and improvement in quality of life (Pearson correlation coefficient below ±0.7; P > 0.05).

Conclusions

Based on a broad range of outcome measurements, we observed an improved quality of life in almost all patients, even in those without measurable volume loss of the extremity operated on, which emphasizes the need for a standardized use of patient-reported outcome measures to evaluate the benefits of lymphatic reconstructive surgery.

A Comparative Analysis to Dissect the Histological and Molecular Differences among Lipedema, Lipohypertrophy and Secondary Lymphedema

Lipedema, lipohypertrophy and secondary lymphedema are three conditions characterized by disproportionate subcutaneous fat accumulation affecting the extremities. Despite the apparent similarities and differences among their phenotypes, a comprehensive histological and molecular comparison does not yet exist, supporting the idea that there is an insufficient understanding of the conditions and particularly of lipohypertrophy. In our study, we performed histological and molecular analysis in anatomically-, BMI- and gender-matched samples of lipedema, lipohypertrophy and secondary lymphedema versus healthy control patients. Hereby, we found a significantly increased epidermal thickness only in patients with lipedema and secondary lymphedema, while significant adipocyte hypertrophy was identified in both lipedema and lipohypertrophy. Interestingly, the assessment of lymphatic vessel morphology showed significantly decreased total area coverage in lipohypertrophy versus the other conditions, while VEGF-D expression was significantly decreased across all conditions. The analysis of junctional genes often associated with permeability indicated a distinct and higher expression only in secondary lymphedema. Finally, the evaluation of the immune cell infiltrate verified the increased CD4+ cell and macrophage infiltration in lymphedema and lipedema respectively, without depicting a distinct immune cell profile in lipohypertrophy. Our study describes the distinct histological and molecular characteristics of lipohypertrophy, clearly distinguishing it from its two most important differential diagnoses.

Donor Site Defect Coverage of the Forearm with Dermal Substitute After Harvesting Radial Forearm Free Flap for Phalloplasty: Is MatriDerm® Worth the Effort?

An aesthetically and functionally pleasing phalloplasty is most commonly performed by a free radial forearm flap. However, the problem with donor site morbidity on the forearm remains unsolved. The aim of this study was to evaluate if the use of a dermal template such as MatriDerm® on the donor site significantly decreases the incidence of complications based on the Clavien–Dindo classification, such as wound healing disorders and reoperation rate, and if it could shortens the duration of hospital stay. A case series analysis was conducted at our institution. A total of 21 patients divided into two groups undergoing the phallic construction after the Gottlieb and Levine design in a single center underwent the donor site defect coverage either by MatriDerm® and split-thickness skin graft from the thigh or by full-thickness skin graft from the groin area. The use of MatriDerm® and split-thickness skin graft showed to have a statistically significant impact on the rate of complications (p = 0.008). Complications that were treated conservatively as well as that require surgical revision were significantly lower in the MatriDerm® group than in the full-thickness skin graft group (p = 0.002). Complications occurred not only at the forearm but also at the groin, where the full-thickness skin graft was harvested. The large dimension of the free radial forearm flap used for phalloplasty resulted in a significant donor site morbidity, leading to wound healing disorders, reoperations, and extended length of hospital stay. Therefore, we consider the use of dermal templates such as MatriDerm® as worth the additional effort and costs in this patient collective.

[Robotics in plastic surgery]

In recent years surgical robotic systems which were specifically developed for microsurgery have expanded the application of robotic-assisted surgery to plastic reconstructive surgery. Currently, there are two microsurgical robotic systems available for reconstructive plastic surgery. Both systems feature tremor reduction and motion scaling technologies, which are intended to optimize the surgeon's precision and dexterity. In the Department of Plastic Surgery and Hand Surgery at the University Hospital Zurich, the Symani Surgical System® has already been used for many microsurgical and supermicrosurgical operations, including autologous breast reconstruction, nerve transfer and, in particular, reconstructive lymphatic surgery. Despite special technical challenges, such as a lack of haptic feedback, the advantages outweigh the disadvantages for an appropriately trained and skilled microsurgeon, including smaller surgical access incisions for anatomically deep structures and an improvement in surgical precision.

A distinct M2 macrophage infiltrate and transcriptomic profile decisively influence adipocyte differentiation in lipedema

Lipedema is a chronic and progressive adipose tissue disorder, characterized by the painful and disproportionate increase of the subcutaneous fat in the lower and/or upper extremities. While distinct immune cell infiltration is a known hallmark of the disease, its role in the onset and development of lipedema remains unclear. To analyze the macrophage composition and involved signaling pathways, anatomically matched lipedema and control tissue samples were collected intra-operatively from gender- and BMI-matched patients, and the Stromal Vascular Fraction (SVF) was used for Cytometry by Time-of-Flight (CyTOF) and RNA sequencing. The phenotypic characterization of the immune component of lipedema versus control SVF using CyTOF revealed significantly increased numbers of CD163 macrophages. To gain further insight into this macrophage composition and molecular pathways, RNA sequencing of isolated CD11b+ cells was performed. The analysis suggested a significant modification of distinct gene ontology clusters in lipedema, including cytokine-mediated signaling activity, interleukin-1 receptor activity, extracellular matrix organization, and regulation of androgen receptor signaling. As distinct macrophage populations are known to affect adipose tissue differentiation and metabolism, we evaluated the effect of M2 to M1 macrophage polarization in lipedema using the selective PI3Kγ inhibitor IPI-549. Surprisingly, the differentiation of adipose tissue-derived stem cells with conditioned medium from IPI-549 treated SVF resulted in a significant decreased accumulation of lipids in lipedema versus control SVF. In conclusion, our results indicate that CD163+ macrophages are a critical component in lipedema and re-polarization of lipedema macrophages can normalize the differentiation of adipose-derived stem cells in vitro evaluated by the cellular lipid accumulation. These data open a new chapter in understanding lipedema pathophysiology and may indicate potential treatment options.

Targeted therapies and checkpoint inhibitors in sarcoma

Sarcomas are defined as a group of mesenchymal malignancies with over 100 heterogeneous subtypes. As a rare and difficult to diagnose entity, micrometastasis is already present at the time of diagnosis in many cases. Current treatment practice of sarcomas consists mainly of surgery, (neo)adjuvant chemo- and/or radiotherapy. Although the past decade has shown that particular genetic abnormalities can promote the development of sarcomas, such as translocations, gain-of-function mutations, amplifications or tumor suppressor gene losses, these insights have not led to established alternative treatment strategies so far. Novel therapeutic concepts with immunotherapy at its forefront have experienced some remarkable success in different solid tumors while their impact in sarcoma remains limited. In this review, the most common immunotherapy strategies in sarcomas, such as immune checkpoint inhibitors, targeted therapy and cytokine therapy are concisely discussed. The programmed cell death (PD)-1/PD-1L axis and apoptosis-inducing cytokines, such as TNF-related apoptosis-inducing ligand (TRAIL), have not yielded the same success like in other solid tumors. However, in certain sarcoma subtypes, e.g. liposarcoma or undifferentiated pleomorphic sarcoma, encouraging results in some cases when employing immune checkpoint inhibitors in combination with other treatment options were found. Moreover, newer strategies such as the targeted therapy against the ancient cytokine macrophage migration inhibitory factor (MIF) may represent an interesting approach worth investigation in the future.

Preoperative Mapping of Lymphatic Vessels by Multispectral Optoacoustic Tomography

Background: In lymphatic reconstructive surgery, visualization of lymph vessels is of paramount importance. Indocyanine green (ICG) lymphography is the current gold standard in preoperative lymphatic imaging. However, visualization of lymph vessels is often limited by an overlying dermal backflow of ICG, becoming particularly prominent in advanced lymphedema stages. Multispectral optoacoustic tomography (MSOT) has recently been introduced as a promising noninvasive tool for lymphatic imaging. Methods and Results: A single-center proof-of-concept study with a prospective observational design was conducted at the Department of Plastic Surgery and Hand Surgery of the University Hospital Zurich. Between February 2021 and August 2021, seven patients with different grades of lymphedema were analyzed by the MSOT Acuity system before undergoing lymphovenous anastomosis (LVA). Conventional ICG lymphography served as comparison. MSOT succeeded to accurately depict blood and lymphatic vessels at different locations in six patients, including areas of dermal backflow. The MSOT signal of lymph vessels further correlated well with their macroscopic appearance. Conclusion: We could successfully visualize lymphatic vessels in patients with lymphedema by MSOT and establish the new method for preoperative mapping and selection of incision sites for LVA. Regardless of dermal backflow patterns, MSOT proved to be a valuable approach for identifying and clearly discerning between lymphatic and blood vessels.

Mediators of Capillary-to-Venule Conversion in the Chronic Inflammatory Skin Disease Psoriasis

Psoriasis is a chronic inflammatory skin disease characterized by epidermal hyperplasia and hyperkeratosis, immune cell infiltration and vascular remodeling. Despite the emerging recognition of vascular normalization as a potential strategy for managing psoriasis, an in-depth delineation of the remodeled dermal vasculature has been missing. In this study, we exploited 5' single-cell RNA sequencing to investigate the transcriptomic alterations in different subpopulations of blood vascular and lymphatic endothelial cells directly isolated from psoriatic and healthy human skin. Individual subtypes of endothelial cells underwent specific molecular repatterning associated with cell adhesion and extracellular matrix organization. Blood capillaries, in particular, showed upregulation of the melanoma cell adhesion molecule as well as its binding partners and adopted postcapillary venule‒like characteristics during chronic inflammation that are more permissive to leukocyte transmigration. We also identified psoriasis-specific interactions between cis-regulatory enhancers and promoters for each endothelial cell subtype, revealing the dysregulated gene regulatory networks in psoriasis. Together, our results provide more insights into the specific transcriptional responses and epigenetic signatures of endothelial cells lining different vessel compartments in chronic skin inflammation.

Is Lymphedema a Systemic Disease? A Paired Molecular and Histological Analysis of the Affected and Unaffected Tissue in Lymphedema Patients

Secondary lymphedema is a chronic, debilitating disease and one of the most common side effects of oncologic surgery, substantially decreasing quality of life. Despite the progress conducted in lymphedema research, the underlying pathomechanisms remain elusive. Lymphedema is considered to be a disease affecting an isolated extremity, yet imaging studies suggest systemic changes of the lymphatic system in the affected patients. To evaluate potential systemic manifestations in lymphedema, we collected matched fat and skin tissue from the edematous and non-edematous side of the same 10 lymphedema patients as well as anatomically matched probes from control patients to evaluate whether known lymphedema manifestations are present systemically and in comparison to health controls. The lymphedematous tissue displayed various known hallmarks of lymphedema compared to the healthy controls, such as increased epidermis thickness, collagen deposition in the periadipocyte space and the distinct infiltration of CD4+ cells. Furthermore, morphological changes in the lymphatic vasculature between the affected and unaffected limb in the same lymphedema patient were visible. Surprisingly, an increased collagen deposition as well as CD4 expression were also detectable in the non-lymphedematous tissue of lymphedema patients, suggesting that lymphedema may trigger systemic changes beyond the affected extremity.

Novel Blood Vascular Endothelial Subtype-Specific Markers in Human Skin Unearthed by Single-Cell Transcriptomic Profiling

Ample evidence pinpoints the phenotypic diversity of blood vessels (BVs) and site-specific functions of their lining endothelial cells (ECs). We harnessed single-cell RNA sequencing (scRNA-seq) to dissect the molecular heterogeneity of blood vascular endothelial cells (BECs) in healthy adult human skin and identified six different subpopulations, signifying arterioles, post-arterial capillaries, pre-venular capillaries, post-capillary venules, venules and collecting venules. Individual BEC subtypes exhibited distinctive transcriptomic landscapes associated with diverse biological pathways. These functionally distinct dermal BV segments were characterized by their unique compositions of conventional and novel markers (e.g., arteriole marker GJA5; arteriole capillary markers ASS1 and S100A4; pre-venular capillary markers SOX17 and PLAUR; venular markers EGR2 and LRG1), many of which have been implicated in vascular remodeling upon inflammatory responses. Immunofluorescence staining of human skin sections and whole-mount skin blocks confirmed the discrete expression of these markers along the blood vascular tree in situ, further corroborating BEC heterogeneity in human skin. Overall, our study molecularly refines individual BV compartments, whilst the identification of novel subtype-specific signatures provides more insights for future studies dissecting the responses of distinct vessel segments under pathological conditions.

Development and Clinical Validation of the LymphMonitor Technology to Quantitatively Assess Lymphatic Function

Current diagnostic methods for evaluating the functionality of the lymphatic vascular system usually do not provide quantitative data and suffer from many limitations including high costs, complexity, and the need to perform them in hospital settings. In this work, we present a quantitative, simple outpatient technology named LymphMonitor to quantitatively assess lymphatic function. This method is based on the painless injection of the lymphatic-specific near-infrared fluorescent tracer indocyanine green complexed with human serum albumin, using MicronJet600^TM microneedles, and monitoring the disappearance of the fluorescence signal at the injection site over time using a portable detection device named LymphMeter. This technology was investigated in 10 patients with unilateral leg or arm lymphedema. After injection of a tracer solution into each limb, the signal was measured over 3 h and the area under the normalized clearance curve was calculated to quantify the lymphatic function. A statistically significant difference in lymphatic clearance in the healthy versus the lymphedema extremities was found, based on the obtained area under curves of the normalized clearance curves. This study provides the first evidence that the LymphMonitor technology has the potential to diagnose and monitor the lymphatic function in patients.

The Role of Macrophage Migration Inhibitory Factor in Adipose-Derived Stem Cells Under Hypoxia

Background: Adipose-derived stem cells (ASCs) are multipotent mesenchymal stem cells characterized by their strong regenerative potential and low oxygen consumption. Macrophage migration inhibitory factor (MIF) is a multifunctional chemokine-like cytokine that is involved in tissue hypoxia. MIF is not only a major immunomodulator but also is highly expressed in adipose tissue such as subcutaneous adipose tissue of chronic non-healing wounds. In the present study, we investigated the effect of hypoxia on MIF in ASCs isolated from healthy versus inflamed adipose tissue. Methods: Human ASCs were harvested from 17 patients (11 healthy adipose tissue samples, six specimens from chronic non-healing wounds). ASCs were treated in a hypoxia chamber at <1% oxygen. ASC viability, MIF secretion as well as expression levels of MIF, its receptor CD74, hypoxia-inducible transcription factor-1α (HIF-1α) and activation of the AKT and ERK signaling pathways were analyzed. The effect of recombinant MIF on the viability of ASCs was determined. Finally, the effect of MIF on the viability and production capacity of ASCs to produce the inflammatory cytokines tumor necrosis factor (TNF), interleukin (IL)-6, and IL-1β was determined upon treatment with recombinant MIF and/or a blocking MIF antibody. Results: Hypoxic treatment inhibited proliferation of ASCs derived from healthy or chronic non-healing wounds. ASCs from healthy adipose tissue samples were characterized by a low degree of MIF secretion during hypoxic challenge. In contrast, in ASCs from adipose tissue samples of chronic non-healing wounds, secretion and expression of MIF and CD74 expression were significantly elevated under hypoxia. This was accompanied by enhanced ERK signaling, while AKT signaling was not altered. Recombinant MIF did stimulate HIF-1α expression under hypoxia as well as AKT and ERK phosphorylation, while no effect on ASC viability was observed. Recombinant MIF significantly reduced the secretion of IL-1β under hypoxia and normoxia, and neutralizing MIF-antibodies diminished TNF-α and IL-1β release in hypoxic ASCs. Conclusions: Collectively, MIF did not affect the viability of ASCs from neither healthy donor site nor chronic wounds. Our results, however, suggest that MIF has an impact on the wound environment by modulating inflammatory factors such as IL-1β.

Adipose Tissue Hypertrophy, An Aberrant Biochemical Profile and Distinct Gene Expression in Lipedema

BACKGROUND

Lipedema is a common adipose tissue disorder affecting women, characterized by a symmetric subcutaneous adipose tissue deposition, particularly of the lower extremities. Lipedema is usually underdiagnosed, thus remaining an undertreated disease. Importantly, no histopathologic or molecular hallmarks exist to clearly diagnose the disease, which is often misinterpreted as obesity or lymphedema.

MATERIALS AND METHODS

The aim of the present study is to characterize in detail morphologic and molecular alterations in the adipose tissue composition of lipedema patients compared with healthy controls. Detailed histopathologic and molecular characterization was performed using lipid and cytokine quantification as well as gene expression arrays. The analysis was conducted on anatomically matched skin and fat tissue biopsies as well as fasting serum probes obtained from 10 lipedema and 11 gender and body mass index-matched control patients.

RESULTS

Histologic evaluation of the adipose tissue showed increased intercellular fibrosis and adipocyte hypertrophy. Serum analysis showed an aberrant lipid metabolism without changes in the circulating adipokines. In an adipogenesis gene array, a distinct gene expression profile associated with macrophages was observed. Histologic assessment of the immune cell infiltrate confirmed the increased presence of macrophages, without changes in the T-cell compartment.

CONCLUSIONS

Lipedema presents a distinguishable disease with typical tissue architecture and aberrant lipid metabolism, different to obesity or lymphedema. The differentially expressed genes and immune cell infiltration profile in lipedema patients further support these findings.

High-Fat Diet in the Absence of Obesity Does Not Aggravate Surgically Induced Lymphoedema in Mice

BACKGROUND

Lymphoedema represents the cardinal manifestation of lymphatic dysfunction and is associated with expansion of the adipose tissue in the affected limb. In mice, high-fat diet (HFD)-induced obesity was associated with impaired collecting lymphatic vessel function, and adiposity aggravated surgery-induced lymphoedema in a mouse model. The aim of the current study was to investigate whether adiposity is necessary to impair lymphatic function or whether increased lipid exposure alone might be sufficient in a surgical lymphoedema model.

METHODS

To investigate the role of increased lipid exposure in lymphoedema development we used a well-established mouse tail lymphoedema model. Female mice were subjected to a short-term (6 weeks) HFD, without development of obesity, before surgical induction of lymphedema. Lymphoedema was followed over a period of 6 weeks measuring oedema, evaluating tissue histology and lymphatic vascular function.

RESULTS

HFD increased baseline angiogenesis and average lymphatic vessel size in comparison to the chow control group. Upon induction of lymphedema, HFD-treated mice did not exhibit aggravated oedema and no morphological differences were observed in the blood and lymphatic vasculature. Importantly, the levels of fibro-adipose tissue deposition were comparable between the 2 groups and lymphatic vessel function was not impaired as a result of the HFD. Although the net immune cell infiltration was comparable, the HFD group displayed an increased infiltration of macrophages, which exhibited an M2 polarization phenotype.

CONCLUSIONS

These results indicate that increased adiposity rather than dietary influences determines predisposition to or severity of lymphedema.

Regulatory T cell transfer ameliorates lymphedema and promotes lymphatic vessel function

Secondary lymphedema is a common postcancer treatment complication, but the underlying pathological processes are poorly understood and no curative treatment exists. To investigate lymphedema pathomechanisms, a top-down approach was applied, using genomic data and validating the role of a single target. RNA sequencing of lymphedematous mouse skin indicated upregulation of many T cell-related networks, and indeed depletion of CD4⁺ cells attenuated lymphedema. The significant upregulation of Foxp3, a transcription factor specifically expressed by regulatory T cells (Tregs), along with other Treg-related genes, implied a potential role of Tregs in lymphedema. Indeed, increased infiltration of Tregs was identified in mouse lymphedematous skin and in human lymphedema specimens. To investigate the role of Tregs during disease progression, loss-of-function and gain-of-function studies were performed. Depletion of Tregs in transgenic mice with Tregs expressing the primate diphtheria toxin receptor and green fluorescent protein (Foxp3-DTR-GFP) mice led to exacerbated edema, concomitant with increased infiltration of immune cells and a mixed T_H1/T_H2 cytokine profile. Conversely, expansion of Tregs using IL-2/anti-IL-2 mAb complexes significantly reduced lymphedema development. Therapeutic application of adoptively transferred Tregs upon lymphedema establishment reversed all of the major hallmarks of lymphedema, including edema, inflammation, and fibrosis, and also promoted lymphatic drainage function. Collectively, our results reveal that Treg application constitutes a potential new curative treatment modality for lymphedema.

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

Secondary lymphedema is a common complication of cancer treatment characterized by chronic limb swelling with interstitial inflammation. The rodent hindlimb is a widely used model for the evaluation of novel lymphedema treatments. However, the assessment of limb volume in small animals is challenging. Recently, high-resolution three-dimensional (3D) imaging modalities have been introduced for rodent limb volumetry. In the present study we evaluated the validity of microcomputed tomography (μCT), magnetic resonance imaging (MRI) and ultrasound in comparison to conventional measuring techniques. For this purpose, acute lymphedema was induced in the mouse hindlimb by a modified popliteal lymphadenectomy. The 4-week course of this type of lymphedema was first assessed in 6 animals. In additional 12 animals, limb volumes were analyzed by μCT, 9.4 T MRI and 30 MHz ultrasound as well as by planimetry, circumferential length and paw thickness measurements. Interobserver correlation was high for all modalities, in particular for μCT analysis (r = 0.975, p < 0.001). Importantly, caliper-measured paw thickness correlated well with μCT (r = 0.861), MRI (r = 0.821) and ultrasound (r = 0.800). Because the assessment of paw thickness represents a time- and cost-effective approach, it may be ideally suited for the quantification of rodent hindlimb lymphedema.

Walking the Line: A Fibronectin Fiber-Guided Assay to Probe Early Steps of (Lymph)angiogenesis

Angiogenesis and lymphangiogenesis are highly complex morphogenetic processes, central to many physiological and pathological conditions, including development, cancer metastasis, inflammation and wound healing. While it is described that extracellular matrix (ECM) fibers are involved in the spatiotemporal regulation of angiogenesis, current angiogenesis assays are not specifically designed to dissect and quantify the underlying molecular mechanisms of how the fibrillar nature of ECM regulates vessel sprouting. Even less is known about the role of the fibrillar ECM during the early stages of lymphangiogenesis. To address such questions, we introduced here an in vitro (lymph)angiogenesis assay, where we used microbeads coated with endothelial cells as simple sprouting sources and deposited them on single Fn fibers used as substrates to mimic fibrillar ECM. The fibers were deposited on a transparent substrate, suitable for live microscopic observation of the ensuing cell outgrowth events at the single cell level. Our proof-of-concept studies revealed that fibrillar Fn, compared to Fn-coated surfaces, provides far stronger sprouting and guidance cues to endothelial cells, independent of the tested mechanical strains of the Fn fibers. Additionally, we found that VEGF-A, but not VEGF-C, stimulates the collective outgrowth of lymphatic endothelial cells (LEC), while the collective outgrowth of blood vascular endothelial cells (HUVEC) was prominent even in the absence of these angiogenic factors. In addition to the findings presented here, the modularity of our assay allows for the use of different ECM or synthetic fibers as substrates, as well as of other cell types, thus expanding the range of applications in vascular biology and beyond.

Animal models in surgical lymphedema research--a systematic review

BACKGROUND

Chronic secondary lymphedema is a well-known complication in oncologic surgery. Autologous lymph node transplantation, lymphovenous anastomosis, and other lymphatic surgeries have been developed in the last decades with rising clinical application. Animal models to explore the pathophysiology of lymphedema and microsurgical interventions have reached great popularity, although the induction of stable lymphedema in animals is still challenging. The aim of this review was to systematically assess lymphedema animal models and their potential use to study surgical interventions.

MATERIALS AND METHODS

A systematic review according to the PRISMA guidelines was performed without time or language restriction. Studies describing new or partially new models were included in chronological order. Models for primary and secondary lymphedema were assessed, and their potential for surgical procedures was evaluated.

RESULTS

The systematic search yielded 8590 discrete articles. Of 180 articles included on basis of title, 84 were excluded after abstract review. Ninety-six were included in the final analysis with 24 key articles.

CONCLUSIONS

No animal model is perfect, and many models show spontaneous lymphedema resolution. The rodent limb appears to be the most eligible animal model for experimental reconstruction of the lymphatic function as it is well accessible for vascularized tissue transfer. There is a need for standardized parameters in experimental lymphedema quantification. Also, more permanent models to study the effect of free vascularized lymph node transfer are needed.