Dear Colleagues,

Rheumatic diseases (RDs) are a heterogeneous cluster of pathological conditions, characterized by cellular and humoral immune responses, leading to an inflammatory milieu, with the production of pro-inflammatory cytokines. Musculo-skeletal manifestations represent a shared aspect that appear together with several clinical features that range from skin to renal involvement to the production of a large variety of autoantibodies.

One of the most important unmet needs in RDs consists of the identification of biomarkers able to identify patients at risk to develop more aggressive phenotypes and to predict response to treatment. In the last few years, some research has suggested a possible role for neural markers, such as semaphorin-3A (Sema3A), calcitonin gene-related peptide, nerve growth factor, and substance P, in immune response regulation. They are a large family of secreted or membrane-bound proteins, interacting with specific receptors. These neuropeptide pathways could stimulate well-defined changes in the activity and function of bone cells, leading to RD features.

For instance, Sema3A seems to exert a potent immunomodulator effect throughout the different stages of immune response by acting on T- and B-cells but also on FoxP3+ Tregs. This wide range of action strongly suggests a pivotal role for semaphorins in RD pathogenesis and the possibility to target these molecules as a therapeutic strategy. Data from the literature have so far provided contrasting results in terms of semaphorin serum levels in autoimmune diseases. Considering Sema3A, high levels of this molecule have been identified in patients affected by systemic lupus erythematosus, while low levels have been observed in patients with rheumatoid arthritis. Moreover, Sema3A seems to be contributing to bone remodeling in patients affected by spondyloarthropathies.

Nonetheless, neuropeptides seem to be involved in the pain modulation of patients affected by fibromyalgia, suggesting a possible role in disease pathogenesis and treatment.

The aim of this Special Issue is to summarize the latest knowledge and novel findings on the role of neuropeptides in RDs. We encourage basic scientists as well as clinicians to submit original research articles describing novel findings, as well as review articles summarizing the state of the art on neuropeptides in pathogenesis and as biomarkers and therapeutic targets in RDs.

Potential topics include, but are not limited to, the following:

• The role of neuropeptides in the pathogenesis of RDs;
• Genetic variants of neuropeptides in RDs;
• The potential role of neuropeptides in RD therapy;
• Neuropeptide modulation during the treatment of RDs.

Papers are published upon acceptance, regardless of the Special Issue publication date.

Dr. Carlo Perricone
Dr. Fulvia Ceccarelli
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Biomolecules is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.