Transcriptome analysis and functional identification of adipose-derived mesenchymal stem cells in secondary lymphedema

Changes in intracellular water volume after leg lymphedema onset and lymphaticovenular anastomosis as its surgical intervention

OBJECTIVE

To clarify the changes in the intracellular water (ICW) volume in lymphedema-affected legs after lymphedema onset and its surgical intervention (ie, lymphaticovenular anastomosis [LVA]), we investigated the changes in body water composition using bioelectrical impedance analysis.

METHODS

This retrospective case series included 41 women with unilateral secondary leg lymphedema. The volume changes in the ICW and extracellular water (ECW) of the affected leg were measured using an InBody S10 (InBody Co, Ltd) multifrequency bioelectrical impedance analyzer, at both lymphedema onset and 1 year after LVA.

RESULTS

The volume increase with leg lymphedema onset was comparable between the ECW and ICW (0.59 L vs 0.56 L; 95% confidence interval [CI], -0.02 to 0.06; P = .27), and the increase rate was higher for ECW (35.3% vs 22.1%; 95% CI, 9.3%-17.2%; P < .001). The volume reduction at 1 year after LVA was comparable between ECW and ICW (0.23 L vs 0.27 L; 95% CI, -0.08 to 0.02; P = .20), and the reduction rate was higher for ECW (8.7% vs 7.0%, 95% CI, 0.04%-3.2%; P = .044). The volume difference between ICW and ECW remained constant throughout the six measurements before and after LVA (F[3.01, 120.20] = 1.85; P < .14).

CONCLUSIONS

Leg LVA reduced ICW in the lymphedematous leg. The onset of leg lymphedema increased ECW and ICW in the affected limb, and LVA decreased both ECW and ICW. The volume change in the affected leg was comparable between ECW and ICW at both lymphedema onset and after LVA. However, the rate of change was higher for ECW. The volume difference between ICW and ECW remained constant. Using bioelectrical impedance analysis, alterations in ICW volume were detected in the legs affected by lymphedema, both after the onset of lymphedema and after LVA intervention.

Thyroid Hormone Ameliorates Lymphedema by Suppressing Adipogenesis in a Murine Lymphedema Model

Background: Exogenous supplementation of thyroid hormone could inhibit excessive fat deposition in lymphedema tissue by suppressing adipogenesis. Methods and Results: Cell viability, adipogenic differentiation, and mRNA expression were measured in 3T3-L1 preadipocytes treated with L-thyroxine. Twelve mice were divided into control and L-thyroxine groups. Two weeks after lymphedema was surgically induced, the experimental mice were fed L-thyroxine for 4 weeks. Tail volume and body weight were measured, and 6 weeks after the surgery, tail skin and subcutaneous tissue were harvested for histopathologic examination and protein isolation. In 3T3-L1 cells, treatment with 10-500 μM L-thyroxine did not affect cell viability. Eight days after induction of adipogenic differentiation, lipid accumulation decreased significantly in the 50 and 100 μM L-thyroxine groups (p < 0.001). mRNA levels of peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), and fatty acid-binding protein 4 (FABP4) decreased significantly in the 100 μM L-thyroxine group compared with the control group (p = 0.017). Lymphedema tails treated with L-thyroxine exhibited decreased volume (p = 0.028) and thickness of dermal and subcutaneous tissue (p = 0.01) and increased vascular endothelial growth factor-C protein expression (p = 0.017) compared with the control. Conclusion: Thyroid hormone therapy inhibits the adipogenesis of 3T3-L1 cells in vitro and decreases the volume of murine lymphedema tail in vivo. These findings suggest that thyroid hormone therapy could be used to treat lymphedema.

Single-cell RNA sequencing of subcutaneous adipose tissues identifies therapeutic targets for cancer-associated lymphedema

Cancer-associated lymphedema frequently occurs following lymph node resection for cancer treatment. However, we still lack effective targeted medical therapies for the treatment or prevention of this complication. An in-depth elucidation of the cellular alterations in subcutaneous adipose tissues of lymphedema is essential for medical development. We performed single-cell RNA sequencing of 70,209 cells of the stromal vascular fraction of adipose tissues from lymphedema patients and healthy donors. Four subpopulations of adipose-derived stromal cells (ASCs) were identified. Among them, the PRG4⁺/CLEC3B⁺ ASC subpopulation c3 was significantly expanded in lymphedema and related to adipose tissue fibrosis. Knockdown of CLEC3B in vitro could significantly attenuate the fibrogenesis of ASCs from patients. Adipose tissues of lymphedema displayed a striking depletion of LYVE⁺ anti-inflammatory macrophages and exhibited a pro-inflammatory microenvironment. Pharmacological blockage of Trem1, an immune receptor predominantly expressed by the pro-inflammatory macrophages, using murine LR12, a dodecapeptide, could significantly alleviate lymphedema in a mouse tail model. Cell–cell communication analysis uncovered a perivascular ligand-receptor interaction module among ASCs, macrophages, and vascular endothelial cells. We provided a comprehensive analysis of the lineage–specific changes in the adipose tissues from lymphedema patients at a single-cell resolution. CLEC3B was found to be a potential target for alleviating adipose tissue fibrosis. Pharmacological blockage of TREM1 using LR12 could serve as a promising medical therapy for treating lymphedema.

Single-cell RNA sequencing identifies an Il1rn+/Trem1+ macrophage subpopulation as a cellular target for mitigating the progression of thoracic aortic aneurysm and dissection

Thoracic aortic aneurysm and dissection (TAAD) is a life-threatening condition characterized by medial layer degeneration of the thoracic aorta. A thorough understanding of the regulator changes during pathogenesis is essential for medical therapy development. To delineate the cellular and molecular changes during the development of TAAD, we performed single-cell RNA sequencing of thoracic aortic cells from β-aminopropionitrile-induced TAAD mouse models at three time points that spanned from the early to the advanced stages of the disease. Comparative analyses were performed to delineate the temporal dynamics of changes in cellular composition, lineage-specific regulation, and cell–cell communications. Excessive activation of stress-responsive and Toll-like receptor signaling pathways contributed to the smooth muscle cell senescence at the early stage. Three subpopulations of aortic macrophages were identified, i.e., Lyve1⁺ resident-like, Cd74^high antigen-presenting, and Il1rn⁺/Trem1⁺ pro-inflammatory macrophages. In both mice and humans, the pro-inflammatory macrophage subpopulation was found to represent the predominant source of most detrimental molecules. Suppression of macrophage accumulation in the aorta with Ki20227 could significantly decrease the incidence of TAAD and aortic rupture in mice. Targeting the Il1rn⁺/Trem1⁺ macrophage subpopulation via blockade of Trem1 using mLR12 could significantly decrease the aortic rupture rate in mice. We present the first comprehensive analysis of the cellular and molecular changes during the development of TAAD at single-cell resolution. Our results highlight the importance of anti-inflammation therapy in TAAD, and pinpoint the macrophage subpopulation as the predominant source of detrimental molecules for TAAD. Targeting the IL1RN⁺/TREM1⁺ macrophage subpopulation via blockade of TREM1 may represent a promising medical treatment.

Single-cell RNA-seq reveals lineage-specific regulatory changes of fibroblasts and vascular endothelial cells in keloids

Keloids are a benign dermal fibrotic disorder with features similar to malignant tumors. keloids remain a therapeutic challenge and lack medical therapies, which is partially due to the incomplete understanding of the pathogenesis mechanism. We performed single-cell RNA-seq of 28,064 cells from keloid skin tissue and adjacent relatively normal tissue. Unbiased clustering revealed substantial cellular heterogeneity of keloid tissue, which included 21 clusters assigned to 11 cell lineages. We observed significant expansion of fibroblast and vascular endothelial cell subpopulations in keloids, reflecting their strong association with keloid pathogenesis. Comparative analyses were performed to identify the dysregulated pathways, regulators and ligand-receptor interactions in keloid fibroblasts and vascular endothelial cells. Our results highlight the roles of transforming growth factor beta and Eph-ephrin signaling pathways in both the aberrant fibrogenesis and angiogenesis of keloids. Critical regulators probably involved in the fibrogenesis of keloid fibroblasts, such as TWIST1, FOXO3 and SMAD3, were identified. TWIST1 inhibitor harmine could significantly suppress the fibrogenesis of keloid fibroblasts. In addition, tumor-related pathways were activated in keloid fibroblasts and vascular endothelial cells, which may be responsible for the malignant features of keloids. Our study put insights into the pathogenesis of keloids and provides potential targets for medical therapies.

Wnt Signaling Regulates the Lymphatic Endothelial Transdifferentiation of Adipose-Derived Stromal Cells In Vitro

Lymphedema is a chronic, progressive disease that causes pain as well as heavy economic burdens to patients. Reconstruction of the impaired lymphatic system is the key to treat lymphedema. Currently, there is no cure, but mesenchymal stromal cells show promising potential for lymphatic endothelial regeneration. Adipose-derived stromal cells (ADSCs) have been proved to support lymphangiogenesis both in vivo and in vitro. However, the mechanism in vascular endothelial growth factor C-induced (VEGF-C-induced) lymphatic endothelial transdifferentiation of ADSCs remains unknown. In this study, we show a novel link between the Wingless and int-1 (Wnt) pathway and the lymphatic endothelial differentiation process. We used LiCl to activate Wnt and DKK-1 to inhibit Wnt. Compared with the Wnt inhibition group and the control groups, the Wnt activation group produced more lymphatic endothelial cell (LEC)-related mRNA and proteins. Besides, Wnt-activated ADSCs formed longer tubes in two-dimensional culture and promoted the growth of lymphatic vessels in a three-dimensional transwell ADSC-LEC co-culture system. Our results demonstrated that activation of Wnt during the lymphatic endothelial transdifferentiation of ADSCs would enhance the efficacy of VEGF-C treatment. We anticipate our assay to expand our knowledge of Wnt in cell transdifferentiation and lay a foundation for future efforts to explore a novel and effective ADSC-based therapy for lymphedema.