TGF-β1 mediates pathologic changes of secondary lymphedema by promoting fibrosis and inflammation

Molecular pathophysiology of secondary lymphedema

Lymphedema occurs as a result of lymphatic vessel damage or obstruction, leading to the lymphatic fluid stasis, which triggers inflammation, tissue fibrosis, and adipose tissue deposition with adipocyte hypertrophy. The treatment of lymphedema is divided into conservative and surgical approaches. Among surgical treatments, methods like lymphaticovenular anastomosis and vascularized lymph node transfer are gaining attention as they focus on restoring lymphatic flow, constituting a physiologic treatment approach. Lymphatic endothelial cells form the structure of lymphatic vessels. These cells possess button-like junctions that facilitate the influx of fluid and leukocytes. Approximately 10% of interstitial fluid is connected to venous return through lymphatic capillaries. Damage to lymphatic vessels leads to lymphatic fluid stasis, resulting in the clinical condition of lymphedema through three mechanisms: Inflammation involving CD4+ T cells as the principal contributing factor, along with the effects of immune cells on the VEGF-C/VEGFR axis, consequently resulting in abnormal lymphangiogenesis; adipocyte hypertrophy and adipose tissue deposition regulated by the interaction of CCAAT/enhancer-binding protein α and peroxisome proliferator-activated receptor-γ; and tissue fibrosis initiated by the overactivity of Th2 cells, leading to the secretion of profibrotic cytokines such as IL-4, IL-13, and the growth factor TGF-β1. Surgical treatments aimed at reconstructing the lymphatic system help facilitate lymphatic fluid drainage, but their effectiveness in treating already damaged lymphatic vessels is limited. Therefore, reviewing the pathophysiology and molecular mechanisms of lymphedema is crucial to complement surgical treatments and explore novel therapeutic approaches.

TGFβ1-Induced Fibrotic Responses of Conjunctival Fibroblasts through the Wnt/β-Catenin/CRYAB Signaling Pathway

Conjunctival fibrosis is a common postoperative complication of glaucoma filtration surgery, resulting in uncontrolled intraocular pressure and surgery failure. Therefore, it is urgent to understand the molecular mechanisms underlying conjunctival fibrosis and to explore novel pharmacologic anti-fibrosis therapies for glaucoma filtration surgery. The 4D-DIA quantitative proteomic results, coupled with experimental data, revealed the activation of the Wnt/β-catenin pathway in transforming growth factor (TGF)-β1-induced human conjunctival fibroblasts (HConFs). Treatment with ICG-001, a Wnt/β-catenin inhibitor, effectively inhibited cell proliferation and migration in TGFβ1-treated HConFs. ICG-001 treatment alleviated the increased generation of extracellular matrix proteins induced by TGFβ1. In addition, ICG-001 reduced the expression level of α smooth muscle actin (α-SMA) and inhibited cell contractility in TGFβ1-treated HConFs. Proteomics data further suggested that αB-crystallin (CRYAB) was a downstream target of Wnt/β-catenin, which was up-regulated by TGFβ1 and down-regulated by ICG-001. Immunoblotting assay also indicated that ICG-001 reduced the expressions of ubiquitin and β-catenin in TGFβ1-treated HConFs, implying that CRYAB stabilized β-catenin by inhibiting its ubiquitination degradation. Exogenous CRYAB promoted cell viability, increased extracellular matrix protein levels, and up-regulated α-SMA expression of HConFs under TGFβ1 stimulation. CRYAB rescued TGFβ1-induced fibrotic responses that were suppressed by ICG-001. In conclusion, this study elucidates the regulatory mechanism of the Wnt/β-catenin/CRYAB pathway in conjunctival fibrosis, offering promising therapeutic targets for mitigating bleb scarring after glaucoma filtration surgery.

Breast Cancer-Related Lymphedema Results in Impaired Epidermal Differentiation and Tight Junction Dysfunction

Breast cancer-related lymphedema (BCRL) is characterized by skin changes, swelling, fibrosis, and recurrent skin infections. Clinical studies have suggested that lymphedema results in skin barrier defects; however, the underlying cellular mechanisms and the effects of bacterial contamination on skin barrier function remain unknown. In matched biopsies from patients with unilateral BCRL, we observed decreased expression of FLG and the tight junction protein ZO-1 in skin affected by moderate lymphedema or by subclinical lymphedema in which dermal backflow of lymph was identified by indocyanine green lymphography, relative to those in the controls (areas without backflow and from the unaffected arm). In vitro stimulation of keratinocytes with lymph fluid obtained from patients undergoing lymphedema surgery led to the same changes as well as increased expression of keratin 14, a marker of immature keratinocytes. Finally, using mouse models of lymphedema, we showed that similar to the clinical scenario, the expression of skin barrier proteins was decreased relative to that in normal skin and that colonization with Staphylococcus epidermidis bacteria amplified this effect as well as lymphedema severity. Taken together, our findings suggest that lymphatic fluid stasis contributes to skin barrier dysfunction in lymphedema.

Targeting lymphatic function in cardiovascular-kidney-metabolic syndrome: preclinical methods to analyze lymphatic function and therapeutic opportunities

The lymphatic vascular system spans nearly every organ in the body and serves as an important network that maintains fluid, metabolite, and immune cell homeostasis. Recently, there has been a growing interest in the role of lymphatic biology in chronic disorders outside the realm of lymphatic abnormalities, lymphedema, or oncology, such as cardiovascular-kidney-metabolic syndrome (CKM). We propose that enhancing lymphatic function pharmacologically may be a novel and effective way to improve quality of life in patients with CKM syndrome by engaging multiple pathologies at once throughout the body. Several promising therapeutic targets that enhance lymphatic function have already been reported and may have clinical benefit. However, much remains unclear of the discreet ways the lymphatic vasculature interacts with CKM pathogenesis, and translation of these therapeutic targets to clinical development is challenging. Thus, the field must improve characterization of lymphatic function in preclinical mouse models of CKM syndrome to better understand molecular mechanisms of disease and uncover effective therapies.

The rehabilitation efficacy of diaphragmatic breathing combined with limb coordination training for lower limb lymphedema following gynecologic cancer surgery

Objective

To investigate the impact of diaphragmatic breathing combined with limb training on lower limb lymphedema following surgery for gynecological cancer.

Methods

From January 2022 to May 2022, 60 patients with lower limb lymphedema post-gynecologic cancer surgery were chosen. They were split into a control group (n = 30) and a treatment group (n = 30). The control group underwent complex decongestive therapy (CDT) for managing lower limb lymphedema after gynecologic cancer surgery, while the treatment group received diaphragmatic breathing combined with limb coordination training alongside CDT. Both groups completed a 4-week treatment regimen. The lower limb lymphedema symptoms were evaluated using the genital, lower limb, buttock, and abdomen (GCLQ) scores; bilateral lower limb circumference measurements; and anxiety and depression scores.

Results

Compared to sole CDT administration, individuals undergoing diaphragmatic breathing coupled with limb coordination training experienced notable reductions in scores for the self-perceived symptom assessment questionnaire (GCLQ), bilateral lower limb circumference, as well as anxiety and depression scores.

Conclusion

The incorporation of diaphragmatic breathing combined withalongside limb coordination training can accelerate and augment the efficacy of treating lower limb lymphedema post-gynecologic cancer surgery.

The Role of Inflammation in Lymphedema: A Narrative Review of Pathogenesis and Opportunities for Therapeutic Intervention

Lymphedema is a chronic and progressive disease of the lymphatic system characterized by inflammation, increased adipose deposition, and tissue fibrosis. Despite early hypotheses identifying lymphedema as a disease of mechanical lymphatic disruption alone, the progressive inflammatory nature underlying this condition is now well-established. In this review, we provide an overview of the various inflammatory mechanisms that characterize lymphedema development and progression. These mechanisms contribute to the acute and chronic phases of lymphedema, which manifest clinically as inflammation, fibrosis, and adiposity. Furthermore, we highlight the interplay between current therapeutic modalities and the underlying inflammatory microenvironment, as well as opportunities for future therapeutic development.

A new lymphedema treatment using pyro-drive jet injection

Lymphedema, resulting from impaired lymphatic drainage, causes inflammation, fibrosis and tissue damage leading to symptoms such as limb swelling and restricted mobility. Despite various treatments under exploration, no standard effective therapy exists. Here a novel technique using the pyro-drive jet injection (PJI) was used to create artificial clefts between collagen fibers, which facilitated the removal of excess interstitial fluid. The PJI was used to deliver a mixture of lactated Ringer's solution and air into the tail of animals with secondary skin edema. Edema levels were assessed using micro-CT scanning. Histopathological changes and neovascularization were evaluated on the injury-induced regenerative tissue. Regarding tissue remodeling, we focused on connective tissue growth factor (CTGF) and vascular endothelial growth factor (VEGF)-C. PJI markedly diminished soft tissue volume in the experimental lymphedema animals compared to the non-injected counterparts. The PJI groups exhibited a significantly reduced proportion of inflammatory granulation tissue and an enhanced density of lymphatic vessels and α-smooth muscle actin (αSMA)-positive small vessels in the fibrous granulation tissue compared to the controls. In addition, PJI curtailed the prevalence of CTGF- and VEGF-C-positive cells in regenerative tissue. In a lymphedema animal model, PJI notably ameliorated interstitial edema, promoted lymphatic vessel growth, and bolstered αSMA-positive capillaries in fibrous granulation tissue. PJI's minimal tissue impact post-lymph node dissection indicates significant potential as an early, standard preventative measure. Easily applied in general clinics without requiring specialized training, it offers a cost-effective and highly versatile solution to the management of lymphedema.

Apelin-VEGF-C mRNA delivery as therapeutic for the treatment of secondary lymphedema

Secondary lymphedema (LD) corresponds to a severe lymphatic dysfunction leading to the accumulation of fluid and fibrotic adipose tissue in a limb. Here, we identified apelin (APLN) as a powerful molecule for regenerating lymphatic function in LD. We identified the loss of APLN expression in the lymphedematous arm compared to the normal arm in patients. The role of APLN in LD was confirmed in APLN knockout mice, in which LD is increased and associated with fibrosis and dermal backflow. This was reversed by intradermal injection of APLN-lentivectors. Mechanistically, APLN stimulates lymphatic endothelial cell gene expression and induces the binding of E2F8 transcription factor to the promoter of CCBE1 that controls VEGF-C processing. In addition, APLN induces Akt and eNOS pathways to stimulate lymphatic collector pumping. Our results show that APLN represents a novel partner for VEGF-C to restore lymphatic function in both initial and collecting vessels. As LD appears after cancer treatment, we validated the APLN-VEGF-C combination using a novel class of nonintegrative RNA delivery LentiFlash® vector that will be evaluated for phase I/IIa clinical trial.

[Research advances on stem cell-based treatments in animal studies and clinical trials of lymphedema]

Objective

To summarize the progress of the roles and mechanisms of various types of stem cell-based treatments and their combination therapies in both animal studies and clinical trials of lymphedema.

Methods

The literature on stem cell-based treatments for lymphedema in recent years at home and abroad was extensively reviewed, and the animal studies and clinical trials on different types of stem cells for lymphedema were summarized.

Results

Various types of stem cells have shown certain effects in animal studies and clinical trials on the treatment of lymphedema, mainly through local differentiation into lymphoid endothelial cells and paracrine cytokines with different functions. Current research focuses on two cell types, adipose derived stem cells and bone marrow mesenchymal stem cells, both of which have their own advantages and disadvantages, mainly reflected in the therapeutic effect of stem cells, the difficulty of obtaining stem cells and the content in vivo. In addition, stem cells can also play a synergistic role in combination with other treatments, such as conservative treatment, surgical intervention, cytokines, biological scaffolds, and so on. However, it is still limited to the basic research stage, and only a small number of studies have completed clinical trials.

Conclusion

Stem cells have great transformation potential in the treatment of lymphedema, but there is no unified standard in the selection of cell types, the amount of transplanted cells, and the timing of transplantation.

Not just fibrotic: endothelial-derived TGFβ maintains contractile function and lymphatic muscle phenotype during homeostasis

Cell-cell communication within the lymphatic vasculature during homeostasis is incompletely detailed. Although many discoveries highlight the pathological roles of transforming growth factor-beta (TGFβ) in chronic vascular inflammation and associated fibrosis, only a small amount is known surrounding the role of TGFβ-signaling in homeostatic lymphatic function. Here, we discovered that pharmacological blockade of TGFβ receptor 1 (TGFβR1) negatively impacts rat mesenteric lymphatic vessel pumping, significantly reducing vessel contractility and surrounding lymphatic muscle coverage. We have identified mesenteric lymphatic endothelial cells themselves as a source of endogenous vascular TGFβ and that TGFβ production is significantly increased in these cells via activation of a number of functional pattern recognition receptors they express. We show that a continuous supply of TGFβ is essential to maintain the contractile phenotype of neighboring lymphatic muscle cells and support this conclusion through in vitro analysis of primary isolated lymphatic muscle cells that undergo synthetic differentiation during 2-D cell culture, a phenomenon that could be effectively rescued by supplementation with recombinant TGFβ. Finally, we demonstrate that lymphatic endothelial production of TGFβ is regulated, in part, by nitric oxide in a manner we propose is essential to counteract the pathological over-production of TGFβ. Taken together, these data highlight the essential role of homeostatic TGFβ signaling in the maintenance of lymphatic vascular function and highlight possible deleterious consequences of its inhibition.NEW & NOTEWORTHY The growth factor TGFβ is commonly associated with its pathological overproduction during tissue fibrosis rather than its homeostatic functions. We expose the lymphatic endothelium as a source of endogenous TGFβ, the impact of its production on the maintenance of surrounding lymphatic muscle cell phenotype, and internally regulated mechanisms of its production. Overall, these results highlight the intricate balance of TGFβ-signaling as an essential component of maintaining lymphatic contractile function.

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.

Bioinformatics led discovery of biomarkers related to immune infiltration in diabetes nephropathy

BACKGROUND

The leading cause of end-stage renal disease is diabetic nephropathy (DN). A key factor in DN is immune cell infiltration (ICI). It has been shown that immune-related genes play a significant role in inflammation and immune cell recruitment. However, neither the underlying mechanisms nor immune-related biomarkers have been identified in DNs. Using bioinformatics, this study investigated biomarkers associated with immunity in DN.

METHODS

Using bioinformatic methods, this study aimed to identify biomarkers and immune infiltration associated with DN. Gene expression profiles (GSE30528, GSE47183, and GSE104948) were selected from the Gene Expression Omnibus database. First, we identified 23 differentially expressed immune-related genes and 7 signature genes, LYZ, CCL5, ALB, IGF1, CXCL2, NR4A2, and RBP4. Subsequently, protein-protein interaction networks were created, and functional enrichment analysis and genome enrichment analysis were performed using the gene ontology and Kyoto Encyclopedia of Genes and Genome databases. In the R software, the ConsensusClusterPlus package identified 2 different immune modes (cluster A and cluster B) following the consistent clustering method. The infiltration of immune cells between the 2 clusters was analyzed by applying the CIBERSORT method. And preliminarily verified the characteristic genes through in vitro experiments.

RESULTS

In this study, the samples of diabetes nephropathy were classified based on immune related genes, and the Hub genes LYZ, CCL5, ALB, IGF1, CXCL2, NR4A2 and RBP4 related to immune infiltration of diabetes nephropathy were obtained through the analysis of gene expression differences between different subtypes.

CONCLUSIONS

This study was based on bioinformatics technology to analyze the biomarkers of immune related genes in diabetes nephropathy. To analyze the pathogenesis of diabetes nephropathy at the RNA level, and ultimately provide guidance for disease diagnosis, treatment, and prognosis.

Treatment with YIGSR peptide ameliorates mouse tail lymphedema by 67 kDa laminin receptor (67LR)-dependent cell-cell adhesion

Impaired microcirculation can cause lymphatic leakage which leads to a chronic swelling in the tissues of the body. However, no successful treatment gives any protection against lymphedema due to the lack of well-revealed pathophysiology of secondary lymphedema. Binary image of laminin immunohistochemical expression revealed that distribution of laminin expression localized during surgically induced lymphedema. 67 kDa laminin receptor (67LR) mRNA expression showed a peak at during lymphedema exacerbation. Since the response of 67LR molecules may affect the prevention of inflammation and edema, here we have hypothesized that 67LR ligand of YIGSR peptide could permit reconstructive environment for amelioration of lymphedema and evaluated the effect of YIGSR in a mouse tail model of lymphedema. Indeed, intra-abdominal injections of YIGSR for the first 3 days after inducing lymphedema in the mouse tail model reduced the tail lymphedema on day 14 by 27% (P = 0.035). Histology showed that YIGSR treatment protected lymphedema impairment in epidermis and dermis, and it also inhibited the expansion of intercellular spaces and enhanced especially cell adhesion in the basement membrane as revealed by transmission electron microscopy. Interestingly, the treatment also reduced the local expression of transforming growth factor (TGF)β. Further elucidation of the mechanisms of 67LR-facilitated lymphangiogenesis contributes to find potential targets for the treatment of lymphedema.

Bioinformatics analysis of the immune cell infiltration characteristics and correlation with crucial diagnostic markers in pulmonary arterial hypertension

BACKGROUND

Pulmonary arterial hypertension (PAH) is a pathophysiological syndrome, characterized by pulmonary vascular remodeling. Immunity and inflammation are progressively recognized properties of PAH, which are crucial for the initiation and maintenance of pulmonary vascular remodeling. This study explored immune cell infiltration characteristics and potential biomarkers of PAH using comprehensive bioinformatics analysis.

METHODS

Microarray data of GSE117261, GSE113439 and GSE53408 datasets were downloaded from Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified in GSE117261 dataset. The proportions of infiltrated immune cells were evaluated by CIBERSORT algorithm. Feature genes of PAH were selected by least absolute shrinkage and selection operator (LASSO) regression analysis and validated by fivefold cross-validation, random forest and logistic regression. The GSE113439 and GSE53408 datasets were used as validation sets and logistic regression and receiver operating characteristic (ROC) curve analysis were performed to evaluate the prediction value of PAH. The PAH-associated module was identified by weighted gene association network analysis (WGCNA). The intersection of genes in the modules screened and DEGs was used to construct protein-protein interaction (PPI) network and the core genes were selected. After the intersection of feature genes and core genes, the hub genes were identified. The correlation between hub genes and immune cell infiltration was analyzed by Pearson correlation analysis. The expression level of LTBP1 in the lungs of monocrotaline-induced PAH rats was determined by Western blotting. The localization of LTBP1 and CD4 in lungs of PAH was assayed by immunofluorescence.

RESULTS

A total of 419 DEGs were identified, including 223 upregulated genes and 196 downregulated genes. Functional enrichment analysis revealed that a significant enrichment in inflammation, immune response, and transforming growth factor β (TGFβ) signaling pathway. CIBERSORT analysis showed that ten significantly different types of immune cells were identified between PAH and control. Resting memory CD4+ T cells, CD8+ T cells, γδ T cells, M1 macrophages, and resting mast cells in the lungs of PAH patients were significantly higher than control. Seventeen feature genes were identified by LASSO regression for PAH prediction. WGCNA identified 15 co-expression modules. PPI network was constructed and 100 core genes were obtained. Complement C3b/C4b receptor 1 (CR1), thioredoxin reductase 1 (TXNRD1), latent TGFβ binding protein 1 (LTBP1), and toll-like receptor 1 (TLR1) were identified as hub genes and LTBP1 has the highest diagnostic efficacy for PAH (AUC = 0.968). Pearson correlation analysis showed that LTBP1 was positively correlated with resting memory CD4+ T cells, but negatively correlated with monocytes and neutrophils. Western blotting showed that the protein level of LTBP1 was increased in the lungs of monocrotaline-induced PAH rats. Immunofluorescence of lung tissues from rats with PAH showed increased expression of LTBP1 in pulmonary arteries as compared to control and LTBP1 was partly colocalized with CD4+ cells in the lungs.

CONCLUSION

LTBP1 was correlated with immune cell infiltration and identified as the critical diagnostic maker for PAH.

Topical captopril: a promising treatment for secondary lymphedema

Transforming growth factor-beta 1 (TGF-β1)-mediated tissue fibrosis is an important regulator of lymphatic dysfunction in secondary lymphedema. However, TGF-β1 targeting can cause toxicity and autoimmune complications, limiting clinical utility. Angiotensin II (Ang II) modulates intracellular TGF-β1 signaling, and inhibition of Ang II production using angiotensin-converting enzyme (ACE) inhibitors, such as captopril, has antifibrotic efficacy in some pathological settings. Therefore, we analyzed the expression of ACE and Ang II in clinical lymphedema biopsy specimens from patients with unilateral breast cancer-related lymphedema (BCRL) and mouse models, and found that cutaneous ACE expression is increased in lymphedematous tissues. Furthermore, topical captopril decreases fibrosis, activation of intracellular TGF-β1 signaling pathways, inflammation, and swelling in mouse models of lymphedema. Captopril treatment also improves lymphatic function and immune cell trafficking by increasing collecting lymphatic pumping. Our results show that the renin-angiotensin system in the skin plays an important role in the regulation of fibrosis in lymphedema, and inhibition of this signaling pathway may hold merit for treating lymphedema.

The Future of Lymphedema: Potential Therapeutic Targets for Treatment

Purpose of Review

This review aims to summarize the current knowledge regarding the pharmacological interventions studied in both experimental and clinical trials for secondary lymphedema.

Recent Findings

Lymphedema is a progressive disease that results in tissue swelling, pain, and functional disability. The most common cause of secondary lymphedema in developed countries is an iatrogenic injury to the lymphatic system during cancer treatment. Despite its high incidence and severe sequelae, lymphedema is usually treated with palliative options such as compression and physical therapy. However, recent studies on the pathophysiology of lymphedema have explored pharmacological treatments in preclinical and early phase clinical trials.

Summary

Many potential treatment options for lymphedema have been explored throughout the past two decades including systemic agents and topical approaches to decrease the potential toxicity of systemic treatment. Treatment strategies including lymphangiogenic factors, anti-inflammatory agents, and anti-fibrotic therapies may be used independently or in conjunction with surgical approaches.

Current Status of Lymphangiogenesis: Molecular Mechanism, Immune Tolerance, and Application Prospect

The lymphatic system is a channel for fluid transport and cell migration, but it has always been controversial in promoting and suppressing cancer. VEGFC/VEGFR3 signaling has long been recognized as a major molecular driver of lymphangiogenesis. However, many studies have shown that the neural network of lymphatic signaling is complex. Lymphatic vessels have been found to play an essential role in the immune regulation of tumor metastasis and cardiac repair. This review describes the effects of lipid metabolism, extracellular vesicles, and flow shear forces on lymphangiogenesis. Moreover, the pro-tumor immune tolerance function of lymphatic vessels is discussed, and the tasks of meningeal lymphatic vessels and cardiac lymphatic vessels in diseases are further discussed. Finally, the value of conversion therapy targeting the lymphatic system is introduced from the perspective of immunotherapy and pro-lymphatic biomaterials for lymphangiogenesis.

TGF-β signaling in lymphatic vascular vessel formation and maintenance

Transforming growth factor (TGF)-β and its family members, including bone morphogenetic proteins (BMPs), nodal proteins, and activins, are implicated in the development and maintenance of various organs. Here, we review its role in the lymphatic vascular system (the secondary vascular system in vertebrates), which plays a crucial role in various physiological and pathological processes, participating in the maintenance of the normal tissue fluid balance, immune cell trafficking, and fatty acid absorption in the gut. The lymphatic system is associated with pathogenesis in multiple diseases, including lymphedema, inflammatory diseases, and tumor metastasis. Lymphatic vessels are composed of lymphatic endothelial cells, which differentiate from blood vascular endothelial cells (BECs). Although TGF-β family signaling is essential for maintaining blood vessel function, little is known about the role of TGF-β in lymphatic homeostasis. Recently, we reported that endothelial-specific depletion of TGF-β signaling affects lymphatic function. These reports suggest that TGF-β signaling in lymphatic endothelial cells maintains the structure of lymphatic vessels and lymphatic homeostasis, and promotes tumor lymphatic metastasis. Suppression of TGF-β signaling in lymphatic endothelial cells may therefore be effective in inhibiting cancer metastasis. We highlight recent advances in understanding the roles of TGF-β signaling in the formation and maintenance of the lymphatic system.

Single and combined impacts of irradiation and surgery on lymphatic vasculature and fibrosis associated to secondary lymphedema

Lymphedema (LD) refers to a condition of lymphatic dysfunction associated with excessive fluid accumulation, fibroadipose tissue deposition and swelling. In industrialized countries, LD development mainly results from a local disruption of the lymphatic network by an infection or cancer-related surgery (secondary LD). In the absence of efficient therapy, animal models are needed to decipher the cellular and molecular mechanisms underlying LD and test putative drugs. In this study, we optimized and characterized a murine model of LD that combines an irradiation of the mice hind limb and a radical surgery (lymph node resection associated to lymphatic vessel ligation). We investigated the respective roles of irradiation and surgery in LD formation by comparing their impacts, alone or in combination (with different intervention sequences), on eight different features of the pathology: swelling (paw thickness), indocyanine green (ICG) clearance, lymphatic vasculature remodeling, epidermal and dermal thickening, adipocyte accumulation, inflammatory cell infiltration and collagen deposition. This study supports the importance of radiation prior to surgery to experimentally induce a rapid, severe and sustained tissue remodeling harboring the different hallmarks of LD. We provide the first experimental evidence for an excessive deposition of periostin (POSTN) and tenascin-C (TNC) in LD. Through a computerized method of digital image quantification, we established the spatial map of lymphatic expansion, as well as collagen, POSTN and TNC deposition in papillary and reticular dermis of lymphedematous skins. This mouse model is available to study the patho-physiology of LD and test potential therapeutic targets.

Fibronectin-1 is a dominant mechanism for rheumatoid arthritis via the mediation of synovial fibroblasts activity

Rheumatoid arthritis (RA) has a high incidence and adverse effects on patients, thus posing a serious threat to people’s life and health. However, the underlying mechanisms regarding the development of RA are still elusive. Herein, we aimed to evaluate the RA-associated molecular mechanisms using the scRNA-seq technique. We used the GEO database to obtain scRNA-seq datasets for synovial fibroblasts (SFs) from RA cases, and the genes were then analyzed using principal component analysis (PCA) and T-Stochastic Neighbor Embedding (TSNE) analyses. Bioinformatics evaluations were carried out for asserting the highly enriched signaling pathways linked to the marker genes, and the key genes related to RA initiation were further identified. According to the obtained results, 3 cell types (0, 1, and 2) were identified by TSNE and some marker genes were statistically upregulated in cell type 1 than the other cell types. These marker genes predominantly contributed to extracellular matrix (ECM) architecture, collagen-harboring ECM, and ECM structural components, and identified as enriched with PI3K/AKT signaling cascade. Notably, fibronectin-1 (FN-1) has been identified as a critical gene that is strongly linked to the development of SFs and has enormous promise for regulating the onset of RA. Moreover, such an investigation offers novel perspectives within onset/progression of RA, suggesting that FN-1 may be a key therapeutic target for RA therapies.