Tumor endothelial marker 1 is upregulated in heart after cardiac injury and participates in cardiac remodeling

CD248 interacts with ECM to promote hypertrophic scar formation and development

Hypertrophic scar (HS) presents a significant clinical challenge, frequently arising as a fibrotic sequela of burn injuries and trauma. Characterized by the aberrant activation and proliferation of myofibroblasts, HS lacks a targeted therapeutic approach to effectively reduce this dysregulation. This study offers novel evidence of upregulated expression of CD248 in HS tissues compared to normal skin (NS) tissues. Specifically, the expression of CD248 was predominantly localized to α-SMA+-myofibroblasts in the dermis. To explain the functional role of CD248 in dermal myofibroblast activity, we employed a targeted anti-CD248 antibody, IgG78. Both CD248 intervention and IgG78 treatment effectively suppressed the proliferative, migratory, and ECM-synthesizing activities of myofibroblasts isolated from HS dermis. In addition, IgG78 administration significantly attenuated HS formation in an in vivo rabbit ear model. The LC/MS analysis coupled with co-immunoprecipitation of HS tissues indicated a direct interaction between CD248 and the ECM components Fibronectin (FN) and Collagen I (COL I). These findings collectively suggest that CD248 may function as a pro-fibrotic factor in HS development through its interaction with ECM constituents. The utilization of an anti-CD248 antibody, such as IgG78, represents a promising novel therapeutic strategy for the treatment of HS.

Regulation of matrix reloading by tumor endothelial marker 1 protects against abdominal aortic aneurysm

Tumor endothelial marker 1 (TEM1), an activated mesenchymal cell marker, is implicated in tissue remodeling and repair. Herein, we investigated the role and therapeutic implications of TEM1 in abdominal aortic aneurysm (AAA), a potentially life-threatening aortic disease characterized by vascular inflammation and matrix turnover. Characterization of human AAA revealed increased TEM1 expression derived mainly from medial vascular smooth muscle cells (VSMCs) and adventitial fibroblasts. Bioinformatics analysis demonstrated the association between TEM1-expressing VSMCs and fibroblasts and collagen gene expression. Consistently, collagen content and TEM1 expressed by VSMCs and fibroblasts were increased during CaCl2-induced AAA formation in mice. TEM1 silencing in VSMCs and fibroblasts inhibited transforming growth factor-β1-induced phenotypic change, SMAD2 phosphorylation, and COL1A1 gene expression. Also, Tem1 deficiency reduced collagen synthesis and exacerbated CaCl2-induced AAA formation in mice without disturbing elastin destruction and inflammatory responses. In contrast, rTEM1 promoted phenotypic change and COL1A1 gene expression through SMAD2 phosphorylation in VSMCs and fibroblasts. Treatment with rTEM1 enhanced collagen synthesis, attenuated elastin fragmentation, and inhibited CaCl2-induced and angiotensin II-infused AAA formation. In summary, TEM1 in resident stromal cells regulates collagen synthesis to counteract aortic wall failure during AAA formation. Matrix integrity restored by rTEM1 treatment may hold therapeutic potential against AAA.

TEM1/endosialin/CD248 promotes pathologic scarring and TGF-β activity through its receptor stability in dermal fibroblasts

BACKGROUND

Pathologic scars, including keloids and hypertrophic scars, represent a common form of exaggerated cutaneous scarring that is difficult to prevent or treat effectively. Additionally, the pathobiology of pathologic scars remains poorly understood. We aim at investigating the impact of TEM1 (also known as endosialin or CD248), which is a glycosylated type I transmembrane protein, on development of pathologic scars.

METHODS

To investigate the expression of TEM1, we utilized immunofluorescence staining, Western blotting, and single-cell RNA-sequencing (scRNA-seq) techniques. We conducted in vitro cell culture experiments and an in vivo stretch-induced scar mouse model to study the involvement of TEM1 in TGF-β-mediated responses in pathologic scars.

RESULTS

The levels of the protein TEM1 are elevated in both hypertrophic scars and keloids in comparison to normal skin. A re-analysis of scRNA-seq datasets reveals that a major profibrotic subpopulation of keloid and hypertrophic scar fibroblasts greatly expresses TEM1, with expression increasing during fibroblast activation. TEM1 promotes activation, proliferation, and ECM production in human dermal fibroblasts by enhancing TGF-β1 signaling through binding with and stabilizing TGF-β receptors. Global deletion of Tem1 markedly reduces the amount of ECM synthesis and inflammation in a scar in a mouse model of stretch-induced pathologic scarring. The intralesional administration of ontuxizumab, a humanized IgG monoclonal antibody targeting TEM1, significantly decreased both the size and collagen density of keloids.

CONCLUSIONS

Our data indicate that TEM1 plays a role in pathologic scarring, with its synergistic effect on the TGF-β signaling contributing to dermal fibroblast activation. Targeting TEM1 may represent a novel therapeutic approach in reducing the morbidity of pathologic scars.

High plasma levels of endosialin and cardiovascular events in patients undergoing coronary angiography

Endosialin, also known as tumor endothelial marker-1, is a transmembrane glycoprotein that plays a role in inflammation and tumor progression. Endosialin is upregulated in atherosclerotic lesions. To elucidate the association between blood endosialin levels and cardiovascular events, we measured plasma endosialin levels in 389 patients undergoing coronary angiography who were followed up for a mean follow-up of 6.4 ± 4.2 years for cardiovascular events (cardiovascular death, myocardial infarction, unstable angina, heart failure, stroke, or need for coronary revascularization). Of the 389 patients, 223 had coronary artery disease (CAD). No significant difference was found in plasma endosialin levels between patients with and without CAD (median 0.92 vs. 0.92 ng/mL). During the follow-up, cardiovascular events occurred in 62 patients. Compared with patients without events, those with events had higher endosialin levels (1.12 vs. 0.89 ng/mL), and more often had endosialin level of > 1.1 ng/mL (53% vs. 31%) (P < 0.01). A Kaplan-Meier analysis showed lower event-free survival in patients with endosialin > 1.1 ng/mL than those with ≤ 1.1 ng/mL (P < 0.01). In a multivariate Cox regression analysis, endosialin > 1.1 ng/mL was an independent predictor of cardiovascular events (hazard ratio = 2.00; 95%CI = 1.21-3.32; P < 0.01). Thus, high plasma endosialin levels were associated with an increased risk of cardiovascular events in patients undergoing coronary angiography.

Soluble tumor endothelial marker 1 in heart failure with reduced ejection fraction: A pilot study

Background

Tumor endothelial marker 1 (TEM1/CD248) is a transmembrane protein that expresses in mesenchymal lineage derived cells during embryogenesis and becomes undetectable in normal adults after birth. Re-expression of TEM1 is found in organ fibrosis, wound healing and cardiac remodeling indicating its potential role in heart failure (HF). The purpose of this study is to explore the role of soluble TEM1 (sTEM1) in patients with HF with reduced ejection fraction.

Methods

We examined endomyocardial biopsy specimens from three HF patients and blood samples from 48 patients admitted for acute decompensated HF (age 72 years, men 61.7%). The expression of TEM1 in cardiac tissue and concentrations of sTEM1 in plasma were evaluated. Cultured rat cardiomyocytes (H9c2) and human cardiac fibroblasts (HCF) were stimulated with hypoxia or transforming growth factor beta (TGF-β) to observe the release of sTEM1 into culture media. The conditioned media of hypoxia-stimulated H9c2 cells was harvested and added into cultured cardiac fibroblast to evaluate its biological effect.

Results

Immunofluorescence study of biopsy specimens from three HF patients showed TEM1 expression in cardiomyocytes and cardiac fibroblasts. The plasma level of sTEM1 was significantly higher in patients (0.90 ± 0.23 vs. 0.33 ± 0.10 ng/mL, p = 0.032) with LVEF ≤ 35% compared with those with LVEF 36-49%. The sTEM1 levels had correlations with HF biomarkers of cardiac fibrosis, including growth differentiation factor-15 (GDF-15) and galectin-3. There was a significant increase in sTEM1 levels in the cultured media of H9c2 and HCF after being stressed with hypoxia or TGF-β. The conditioned media derived from hypoxia-stimulated H9c2 cells significantly increased cell proliferation of cardiac fibroblasts. This effect was partially reversed by anti-TEM1 antibody.

Conclusion

This pilot study demonstrated that cardiac TEM1 expression was upregulated in HF. The levels of sTEM1 were significantly higher in HF patients with LVEF ≤ 35% and correlated with other biomarkers of cardiac fibrosis. In vitro study proved that functional sTEM1 was released into cultured media after stressing cardiomyocytes and HCF.