The Role of Collagen VI α6 Chain Gene in Atopic Dermatitis

Establishment of new mouse model for allergic dermatitis showing severe fibrosis

Allergic dermatitis (AD) is a skin disease characterized by a chronic inflammation caused by immune dysregulation. In the histopathology of patients with AD, there are several features, such as accumulation of eosinophils and mast cells, hyperkeratosis, and dermal fibrosis which are related to the exacerbation of AD. Mast cells and eosinophils are thought to be involved in fibrosis, but the details are unknown. Yama mouse is an inbred mouse showing genetically eosinophilia. If eosinophils have significant effect on fibrosis, it may be possible to establish a new AD model with severe fibrosis. In this study, AD was induced by applying dinitrofluorobenzene to mice auricle. Yama mice showed AD lesion with more severe dermal fibrosis with severe eosinophil infiltration than Balb/c and Nc/nga mice. The expression of transforming growth factor-β (TGF-β), a cytokine important for fibrosis, was not significantly different among Yama, Balb/c, and Nc/nga mice, while the expression of interleukin-4 (IL-4), which is also mediator of tissue fibrosis, was increased only in Yama mice. The results of this study showed that AD with more severe fibrosis could be induced in Yama mice than in Balb/c and Nc/nga mice. In Yama mice, it can be concluded that the severe fibrosis is TGF-β independent, and IL-4 would be the main mediator of severe fibrosis. This mouse model may be useful for elucidating the mechanism of fibrosis in chronic AD, and for conducting research leading to the development of new therapies.

The Role of Collagens in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease affecting both children and adults. The clinical picture of AD manifests in typical skin lesions, such as localized eczema and dry skin, with dominant, persistent itching that leads to sleep disturbances. The pathophysiology of AD has been extensively investigated with respect to epigenetic and genetic factors, skin barrier defects, as well as immunological and microbial disorders. However, to date, the involvement of extracellular matrix (ECM) elements has received limited attention. Collagen, a major component of the ECM, may serve as a therapeutic target for the future treatment of AD. This paper summarizes the role of collagens, which are the most abundant components of the extracellular matrix in AD.

The coordinated activities of collagen VI and XII in maintenance of tissue structure, function and repair: evidence for a physical interaction

Collagen VI and collagen XII are structurally complex collagens of the extracellular matrix (ECM). Like all collagens, type VI and XII both possess triple-helical components that facilitate participation in the ECM network, but collagen VI and XII are distinct from the more abundant fibrillar collagens in that they also possess arrays of structurally globular modules with the capacity to propagate signaling to attached cells. Cell attachment to collagen VI and XII is known to regulate protective, proliferative or developmental processes through a variety of mechanisms, but a growing body of genetic and biochemical evidence suggests that at least some of these phenomena may be potentiated through mechanisms that require coordinated interaction between the two collagens. For example, genetic studies in humans have identified forms of myopathic Ehlers-Danlos syndrome with overlapping phenotypes that result from mutations in either collagen VI or XII, and biochemical and cell-based studies have identified accessory molecules that could form bridging interactions between the two collagens. However, the demonstration of a direct or ternary structural interaction between collagen VI or XII has not yet been reported. This Hypothesis and Theory review article examines the evidence that supports the existence of a functional complex between type VI and XII collagen in the ECM and discusses potential biological implications.

A fragment of type VI collagen alpha-6 chain is elevated in serum from patients with atopic dermatitis, psoriasis, hidradenitis suppurativa, systemic lupus erythematosus and melanoma

Extracellular matrix (ECM) remodeling of the skin is a continuous process necessary for maintaining tissue homeostasis. Type VI collagen (COL6) is characterized as a beaded filament, located in the dermal ECM, where COL6-α6-chain has been demonstrated upregulated in atopic dermatitis. The aim of this study was to develop and validate a competitive ELISA, targeting the N-terminal of COL6-α6-chain, named C6A6, and evaluate its associations with the dermatological condition's atopic dermatitis, psoriasis, hidradenitis suppurativa, systemic lupus erythematosus, systemic sclerosis, urticaria, vitiligo, and cutaneous malignant melanoma in comparison, to healthy controls. A monoclonal antibody was raised and employed in an ELISA assay. The assay was developed, technically validated, and evaluated in two independent patient cohorts. Cohort 1 showed C6A6 was significantly elevated in patients with atopic dermatitis (p < 0.0001), psoriasis (p < 0.0001), hidradenitis suppurativa (p = 0.0095), systemic lupus erythematosus (p = 0.0032) and melanoma (p < 0.0001) compared to healthy donors. Cohort 2 confirmed C6A6 being upregulated in atopic dermatitis compared to healthy controls (p < 0.0001), but also associated with disease severity (SCORAD, p = 0.046) and lowered in patients receiving calcineurin inhibitors (p = 0.014). These findings are hypothesis generating, and the utility of the C6A6 biomarker for disease severity and treatment response needs to be validated in larger cohorts and longitudinal studies.