The Complex Epidermal and Dermal Milieu of M2 Macrophages/IL-31/IL-31RA Network May Play a Role in Keloid Associated Pruritus.

backgroundThe exact pathogenesis of keloid (KD) associated pruritus is still unknown and responds poorly to current antipruritic therapies. Pruritogenic role of interleukin-31 (IL-31) has been studied extensively and was proven in a variety of pruritus associated diseases, while its role in KD is still rather vague.

objectiveThe aim of this study is to explore the pathophysiological mechanism of KD-associated pruritus by detecting the correlation between the severity of pruritus and the expression of pruritogenic cytokines IL -31 and its receptor complex components, IL-31 receptor α (IL-31RA) and Onstostatin M receptor β (OSMRβ), and the number of their source cells.

methodsA total of 46 keloid tissue samples were included in this study and clinical data were recorded, of which 24 were available with both lesional and clinically adjacent uninvolved perilesional skin ( AUPS, taken at least 0.5 cm away from the keloid edge ), and 22 were available with lesional skin only. In this study, immunofluorescence detection was used to detect and compare the expression differences of IL-31 and its receptors (IL-31RA and OSMRβ) in different layers (epidermis, superficial dermis, and deep dermis) between keloid lesions and AUPS and the correlation between the IL-31 expression level and the severity of KD-associated pruritus was explored. In addition, immunofluorescence co-localization was used to explore the cell source of IL-31, and the correlation between the number of source cells and the severity of KD-associated pruritus was explored. The fluorescence intensity in epidermis and number of infiltrating cells in the dermis was quantified and normalized by ImageJ software.

resultsIn this study, the KD and AUPS groups were matched for age and gender, which were not statistically different and, there was no significant difference in the sample causes and distribution between two groups. Compared with the AUPS, the number of IL-31(+) cells in the superficial and deep dermal and the total fluorescence intensity of IL-31 in the epidermis were significantly increased in the KD and they were positively correlated with the severity of pruritus. IL-31-derived cells are M2 macrophages and mast cells, but mainly from M2 macrophages. M2 macrophages in the superficial dermis of keloid are related to the severity of KD-associated pruritus. Although mast cells play an important role in the induction of pruritus, the number of infiltrated mast cells in the skin of KD patients was not correlate with the severity of KD-associated pruritus. IL-31RA was strongly expressed in the epidermis and superficial dermis of both groups, and was positively correlated with the severity of pruritus. The number of OSMRβ (+) cells in the superficial dermis of the KD was significantly higher than that of the AUPS, but has no correlation with the severity of pruritus.

conclusionOur data indicate this complex dermal milieu of M2 macrophages/IL-31/IL-31RA network could be useful a therapeutic target for KD-associated pruritus. The superficial dermis may be an important injection layer for the pharmaceuticals and other treatment of KD-associated pruritus. LEVEL OF EVIDENCE II: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .