Rituximab: a potential therapeutic advance in scleroderma: what is the evidence?

Fibrillin microfibrils and proteases, key integrators of fibrotic pathways

Supramolecular networks composed of multi-domain ECM proteins represent intricate cellular microenvironments which are required to balance tissue homeostasis and direct remodeling. Structural deficiency in ECM proteins results in imbalances in ECM-cell communication resulting often times in fibrotic reactions. To understand how individual components of the ECM integrate communication with the cell surface by presenting growth factors or providing fine-tuned biomechanical properties is mandatory for gaining a better understanding of disease mechanisms in the quest for new therapeutic approaches. Here we provide an overview about what we can learn from inherited connective tissue disorders caused primarily by mutations in fibrillin-1 and binding partners as well as by altered ECM processing leading to defined structural changes and similar functional knock-in mouse models. We will utilize this knowledge to propose new molecular hypotheses which should be tested in future studies.

Toward personalized medicine in scleroderma: classification of scleroderma patients into stable "inflammatory" and "fibrotic" subgroups

There is no universally agreed-upon treatment for the fibrosis of scleroderma. Recently, much information has been generated relating to the fundamental mechanisms underlying this disease. Partly based on these observations, both anti-inflammatory and anti-fibrotic agents have been considered as possible therapies. However, this information has not been successfully translated into clinical practice. In this issue, Pendergrass et al. use genome-wide expression profiling to provide valuable insights into scleroderma. Previously, the authors showed that morphea and "limited" scleroderma patients and a small subset of diffuse scleroderma (dSSc) patients express an "inflammatory" profile, whereas the majority of dSSc patients express a "fibroproliferative" profile. In the current study, the investigators show that the gene expression profile of these patients is fixed over time; i.e., in contrast to a previously held belief, the inflammatory patients do not go on to become fibrotic, and vice versa. These data suggest that expression profiling might be used to design clinical trials for scleroderma. The inflammatory patients might be treated with anti-inflammatory agents, whereas fibroproliferative patients might be treated with antifibrotic agents.

Egr-ly awaiting a "personalized medicine" approach to treat scleroderma

Scleroderma, an autoimmune disorder characterized by skin and organ fibrosis, has no treatment. Although over the past decade valuable insights into the molecular mechanisms underlying scleroderma have been generated, results in clinical trials have been disappointing. This issue is likely to arise due to the heterogeneity of scleroderma. Molecular insights into the heterogeneity of this disease have been provided by genome-wide expression profiling. In a recent paper, Bhattacharyya and colleagues (PLOS One 6:e23082, 2011b) to show that the overexpression of a range of "fibroproliferative" genes in diffuse cutaneous scleroderma patients are likely to be caused by the overexpression of transcription factor Early growth response (Egr)-1. Only a minority of Egr-1-regulated genes were also found to be regulated by TGF-ß. Moreover, Greenblatt and colleagues (Am J Pathol., 2012) have shown that the overexpression of "inflammatory" genes overexpressed in "localized" scleroderma and a small subset of limited and diffuse scleroderma patients is likely to be due to the activity of interleukin-13 (IL-13). Intriguingly, at a gene expression level, murine sclerodermatous graft-versus-host disease (sclGVHD) approximates this inflammatory subset of scleroderma. These data suggest that targeting Egr-1 expression/activity might be a novel therapeutic strategy to control fibrosis in a subset of diffuse scleroderma patients, and further emphasize that notion that elevated canonical TGFβ signaling is insufficient to explain the fibrosis observed in scleroderma. Moreover, targeting IL-13 expression/activity might be a novel therapeutic strategy to target the inflammation leading to "localized" scleroderma.

Rituximab in the treatment of systemic sclerosis-associated interstitial lung disease: comment on the article by Yoo

Several lines of evidence from basic research indicate that B cells may contribute to the pathogenesis of systemic sclerosis. Clinical studies as well have provided preliminary data pointing to the direction that B-cell depletion with rituximab might be a therapeutic option for patients with this debilitating disease.