Rheumatoid arthritis as a bone marrow disorder

Area of Science:

• Immunology
• Rheumatology
• Hematology

Background:

• Traditional views of rheumatoid arthritis (RA) focus on joint-specific autoimmunity and T cell involvement.
• Emerging evidence suggests fibroblast-like and macrophagelike synoviocytes in RA pannus originate from or have counterparts in bone marrow (BM).
• The B cell autoimmunity characteristic of RA occurs early, with synovial tissue and BM favoring B cell responses.

Purpose of the Study:

• To challenge the established concepts of RA pathogenesis.
• To propose a novel hypothesis that RA may originate as a bone marrow stem cell disorder.
• To explore the implications of this hypothesis for RA treatment and understanding its comorbidities.

Main Methods:

• Literature review and synthesis of existing research on RA pathogenesis, bone marrow, and T/B cell roles.
• Analysis of the role of synovial microenvironments and bone marrow abnormalities in RA.
• Consideration of evidence from viral tropism, autoimmune overlaps, and bone marrow transplantation outcomes.

Main Results:

• The study posits that RA could be viewed as a disorder of microenvironments sustaining B cell responses, potentially originating in abnormal bone marrow.
• Germinal centers, unique to RA synovium, and BM abnormalities support the idea of RA as a B cell-centric disorder.
• Viral tropism for BM and overlaps with other lymphoproliferative disorders suggest a potential systemic origin, possibly initiated in the bone marrow.

Conclusions:

• Rheumatoid arthritis (RA) may initiate as a stem cell disorder within the bone marrow, distinct from a purely joint-focused autoimmune process.
• The bone marrow's role in sustaining B cell responses and potential stem cell abnormalities are central to this revised understanding of RA.
• This hypothesis warrants further investigation, particularly regarding the rheumatological outcomes of bone marrow transplantation in RA patients, and suggests transplant-like therapeutic strategies.