Background Pathogenesis of Systemic Sclerosis (SSc) is complex and includes impaired communication between endothelial cells, epithelial cells and fibroblasts, leading to connective tissue fibrosis such as dermal fibrosis. About half of the patients present pigmentation patches. It is already known that CCN2 (CTGF) is increased in SSc and that polymorphism of its promoter is associated with the disease. More recently, it was shown that CCN2 is increased in the epidermis of SSc patients. CCN2 is part of a family of 6 members, including CCN3 (NOV), which often antagonizes CCN2. We have previously observed that CCN3 is modulated in non-segmental vitiligo, a hypopigmentary skin disorder, and that fibroblasts can regulate skin pigmentation. In SSc, CCN2 upregulation is sustained by an autocrine activating loop of endothelin 1 (ET-1). ET-1 is a well known pigmentary factor and its secretion by endothelial cells has recently been demonstrated as inducer of skin pigmentation.
Objectives We hypothesize that in patients with pigmentary disorders, secretion of CCN by dermal cells is dysregulated (isoforms, levels). Thus, we plan to study the expression profile of CCNs, among other factors implicated both in fibrosis and pigmentation (ET-1, PPARγ, HIF1α) in SSc patients presenting or not skin pigmentary disorders.
Methods Skin biopsies were obtained from 10 SSc patients, both in abnormally pigmented zones (hypo and/or hyperpigmented) and in non-lesional skin areas. Two patients with morphea were also included. Normal skin from healthy donors was used as control. Biopsies were used to culture fibroblasts, endothelial cells and keratinocytes and to perform histological and immunohistochemical analysis. We performed proteomic analysis, and immunocytochemistry regarding CCN2 and CCN3 on skin cells.
Results Clinical examination of patients with SSc revealed two patterns of pigmentary troubles. Some patients have hypo and/or hyperpigmentary patches in non sun-exposed areas, whereas other patients have only hyperpigmentation in exposed areas which looks like photoaging. In most patients, it seems that pigmentary troubles appeared during the early development of the disease. Our preliminary datas revealed that level of expression of CCN3 observed by immunohistochemistry or in fibroblasts protein extracts differed in lesional and non-lesional areas. Moreover, SSc patients presented various CCN3 isoforms according to pigmentary status. CCN2 examination also revealed variation of its expression as compared to healthy controls. Interestingly, these abnormalities could also be found in apparently non-lesional skin areas from SSc patients, which suggests that CCN2 and 3 expression is altered at early stages of the disease.
Conclusions Differential level of expression and presence of various isoforms of CCNs have to be confirmed in fibroblasts and endothelial cells according to the pigmentary status of the fibrotic areas. This will allow us to verify our hypothesis of two different types of SSc, depending on time of apparition and localization of pigmentary patches. This could help to detect the disease early, which is essential for therapeutic issues. Moreover, if spatio-temporal variations of CCN are confirmed, it could open a specific therapeutic window for the use of CCNs modulators.
Disclosure of Interest None declared