Israel Medical Association Journal

In 2013, the idea of the hyperferritinemic syndrome was introduced to suggest the possible inflammatory properties of ferritin in contributing to the pathogenesis of four diseases, namely Still’s disease, macrophage activation syndrome (MAS), septic shock, and catastrophic antiphospholipid syndrome [1]. Based on this concept, ex vivo and in vitro studies were performed reporting the inflammatory properties of the heavy subunit of ferritin (FeH) in inducing the commitment of macrophages toward an inflammatory phenotype, production of pro-inflammatory cytokines, and the direct stimulation of NLRP3 and NF-kB pathway [2,4]. In addition, recent in vivo studies have established the pathogenic role of hyperferritinemia [4-6], mainly triggering a Still’s disease-like phenotype in a wild type murine model by the aberrant activation of immune cells and production of inflammatory mediators [5]. Moreover, the hyperferritinemic syndrome arena has seen many recent developments due to the rapid accrual of knowledge in coronavirus disease 2019 (COVID-19) [6,7]. Specifically, the appearance of hyperferritinemia is increasingly recognized to be associated with a more severe patient phenotype at higher risk of poor prognosis due to the appearance of the cytokine storm syndrome [8], which is a hyper-inflammatory state due to overwhelming massive release of inflammatory mediators and rapidly evolving to multiorgan failure [9].

A virally-induced cytokine storm syndrome, associated with a massive and overwhelming systemic inflammation, burdens a subgroup of patients with severe coronavirus disease-2019 (COVID-19), which leads to pulmonary inflammation and extensive lung damage. These severe COVID-19 patients are characterized by high ferritin levels. These findings mirror what was previously reported about the prognostic role of this iron storage protein in other inflammatory diseases included in the hyperferritinemic syndrome. The latter suggests that ferritin could be a further pathogenic mediator in enhancing the inflammatory process, stimulating inflammatory pathways, and thus perpetuating a vicious pathogenic loop. Considering its activity as an immune activator, a therapeutic approach targeting ferritin may be also postulated in these diseases. Considering these observations, high ferritin levels characterize severe COVID-19 and other diseases included in the hyperferritinemic syndrome. Because ferritin could enhance the inflammatory process, it could be tested as a possible new therapeutic target to improve the outcome of these patients.

Microvascular damage, clinically expressed by Raynaud’s phenomenon, is generally the first symptom of the disease and the injured vascular cells, both endothelial and perivascular, may transdifferentiate to myofibroblasts, thus leading to collagen deposition in the tissue and consequent fibrosis. Systemic sclerosis (SSc, scleroderma) is complex disease characterized by autoimmunity, vasculopathy, and fibrosis. It has been shown that microvascular damage may be the first symptom of SSc. Injured endothelial cells and pericytes may transdifferentiate into myofibroblasts, the cells responsible for fibrosis and collagen deposition in the tissue. Based on these factors, the process of myofibroblast generation may link two pivotal events of SSc: microvascular damage and fibrosis. Understanding the development, differentiation, and function of myofibroblasts is therefore crucial to individuate early pathogenetic events and develop new therapeutic target for SSc, a condition in which no disease-modifying agents are available. The aim of this review was to discuss the possible origins of myofibroblasts in SSc, highlighting the process of endothelial mesenchymal transition and pericytes to myofibroblast transition and to show how these events may contribute to pathogenesis of the disease.