Molecular and cellular profiling of systemic sclerosis and its preclinical stages

Abstract

The development of unrestrained fibrosis in the skin and internal organs is the hallmark of systemic sclerosis (SSc). Nevertheless, it is known that fibrosis is preceded by vascular and immune modifications. On the basis of SSc-specific autoantibodies and nailfold capillary lesions it is possible to identify individuals with Raynaud’s phenomenon considered at increased risk to develop SSc when compared with the general population. Furthermore, some characteristic SSc features are not fibrotic, they can precede fibrosis and still be sufficient to meet the EUropean League Against Rheumatism (EULAR)/American College of Rheumatology (ACR) classification criteria for SSc. In my PhD thesis I aimed to characterize how patients with early SSc and SSc without any sign of fibrosis differ from fibrotic SSc patients (limited and diffuse cutaneous SSc; lcSSc and dcSSc), by that contributing to increase the knowledge about the events which lead to the onset of fibrosis and provide new ground to prevent it. To do so, we first investigated how different factors involved in vascular and immune activation “behave” in the circulation of early SSc individuals, in patients with SSc without fibrotic features, comparing with fibrotic SSc patients. We then investigated in the different groups natural killer (NK) and NKT-like cells, important in infections control, tumor development and immuneregulation. We found that: - the Interferon (IFN) signature described in SSc patients with fibrosis, is already present since the early SSc stage and in the non-fibrotic SSc group to an even higher extent then in fibrotic SSc patients: - markers of vascular damage (angiopoietin-2, CXCL16, E-selectin, ICAM-1) are already elevated in the circulation of early SSc patients and in a gradually increasing fashion in patients with SSc without fibrotic features and to the highest degree in fibrotic SSc patients, mirroring the same deteriorating trend in clinical parameters (inflammation indicators, lung involvement) from early SSc to non-fibrotic SSc and finally to the lcSSc and dcSSc subsets; - CXCL10, CXCL11, TNFR2 and CHI3L1 can clearly distinguish patients with early SSc and even more the ones with SSc without fibrotic features from healthy controls (HC). Furthermore, within each patient group, the patients who faster evolved (early SSc developing full-blown SSc and non-fibrotic SSc developing fibrotic features) were the ones with the highest circulating levels of CXCL10 and TNFR2; - NK and NKT-like cells from early SSc and non-fibrotic SSc patients produce higher levels of pro-inflammatory/pro-fibrotic molecules (TNF-α, IL-6) than HC in response to different activating triggers; - in the circulation of patients with the most extensive skin fibrosis, dcSSc - but not in early SSc nor in patients with SSc without fibrosis -, a reduction of NK cells expressing the activating receptor NKp46 and of NKT-like cells expressing Killer-Immunoglobulin-like (KIR) receptors are observed. These patterns suggest that in dcSSc patients both NK and NKT-like cells could be less functional - hypothesis confirmed by in vitroNK cell cytotoxicity tests. Moreover, comparing with the phenotype of NK and T cells from patients with rheumatoid and psoriatic arthritis, these expression patterns seem rather specific for SSc.