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MicroRNA targeting to achieve Systemic Sclerosis Control and Prediction

Final Report Summary - MICROSCAP (MicroRNA targeting to achieve Systemic Sclerosis Control and Prediction)

Systemic Sclerosis (SSc) is a disfiguring disease with high mortality and morbidity, characterized by progressive and uncontrollable fibrosis of the skin and internal organs. There is no successful therapy for SSc, resulting in a markedly shortened life expectancy, less than most cancers. Moreover, SSc diagnosis is very difficult in the early phase of the disease; consequently patient treatment is delayed until skin and/or internal organ involvement is evident and already irreversible. The pathology, therefore, presents an extreme need of both effective therapies and early diagnosis/prognosis markers, in order to treat SSc patients before the development of severe organ complications.
Immune system dysfunction constitutes one of SSc hallmarks. This is evident for example by the presence of auto-antibodies and the altered expression of type-I-interferon (IFN)-responsive genes in the skin and pheripheral blood of these patients. Interestingly, a subset of immune cells, the plasmacytoid dendritic cells (pDCs), are the most potent IFNα producers and infiltrate the fibrotic skin of SSc patients; here they produce also high levels of PF4, a chemokine recently proposed as SSc biomarker [van Bon et al., NEJM 2014]. However, the molecular mechanisms leading to pDC dysregulation and the persistent type-I-IFN signature are largely unexplored. This study investigated how a class of small RNA molecules, the microRNAs, influence pDC dysregulation and IFN-response in SSc.
Dr. Rossato identified and confirmed in independent cohorts of patients that a set of miRNAs are dysregualted in pDC of patients with established SSc. Most importantly the same miRNAs are induced already in patients presenting early-SSc symptoms, thus indicating that the alteration of these molecules might be implicated in SSc pathogenesis and therefore can constitute an interesting therapeutic target to halt the disease progression.
Interestingly, similar to what was observed in pDCs, the expression of miRNA in whole blood of the pre-clinical patients showed the same modulation and correlated well with the SSc classification score, thus suggesting that miRNAs altered in pre-clinical SSc patients could be also used as potential biomarker for early SSc diagnosis and prognosis. These observations constituted the core of a Prof-Of-Concept grant (MYRASYS) financed by the EU in 2015 and aimed at evaluating the potential usage of this set of miRNAs to identify SSc patients evolving toward a more severe disease phenotype. Early diagnosis of SSc will offer a “window of opportunity” to begin an early aggressive therapy intervention that can prevent or halt development of life-threatening complications.
Using in-vitro functional experiments, Dr. Rossato also demonstrated that a specific miRNA inhibited the expression of a crucial protein (IRF) involved in the development and activation of pDCs. Consistently, the induction of miRNA expression could inhibit the development of pDC in-vitro, similarly to what is observed in the circulation of SSc patients that present lower pDC counts. In addition, the overexpression of the miRNA in pDCs increased their ability to secrete IFNα, thus potentially contributing to the type-I-IFN signature observed in SSc patients.
Considering that the miRNA is upregulated already at the earliest stages of SSc, the inhibition of such molecule could effectively restore normal pDC function, thus potentially modulating the disease progression. Dr. Rossato conducted Proof-Of-Concept experiments to prove this point: the inhibition of this miRNA in pDCs of SSc patients by using specific antagonists restored the expression of IRF transcription factor to similar levels to what is present in healthy cells. These experiments demonstrated that modulation of miRNA expression can redirect pDC aberrances and potentially halt or dampen the disease progression.
Considering the limited treatment options for SSc (i.e. immunosuppression or autologous stem cell transplant) and their severe side effects, these findings provide an interesting opportunity for the development of novel tailored therapies. These results will constitute the basis to further prove the crucial role of pDC-miRNAs in in-vivo models of SSc and to discuss possible therapeutic development with pharmaceutical companies. The development of a novel therapy able to interfere with the disease development at early stage of the disease will limit the socio-economic burden associated with SSc, namely reducing the costs for chronic treatments and hospitalization and allowing patients to participate in society and stay productive for a longer period of time. Finally, considering that SSc is the prototype of fibrotic disease and that the project will investigate how chronic inflammation leads to fibrosis, the unique knowledge and therapeutic opportunities gained with this study will impact the full spectrum of fibrotic conditions.