Takahiro Ochi

Lymphoid Chemokine B Cell-Attracting Chemokine-1 (CXCL13) Is Expressed in Germinal Center of Ectopic Lymphoid Follicles Within the Synovium of Chronic Arthritis Patients

A unique feature in inflammatory tissue of rheumatoid arthritis (RA) is the formation of ectopic lymphoid aggregates with germinal center (GC)-like structures that can be considered to contribute to the pathogenesis of RA, because local production of the autoantibody, rheumatoid factor, is thought to be a causative factor in tissue damage. However, the factors governing the formation of GC in RA are presently unknown. To begin to address this, the expression of B cell attracting chemokine (BCA-1) (CXCL13), a potent chemoattractant of B cells, was examined in the synovium of patients with RA or with osteoarthritis (OA). Expression of BCA-1 mRNA was detected in all RA samples, but in only one of five OA samples. Lymphoid follicles were observed in four of seven RA samples and in two of eight OA samples, and in most of them BCA-1 protein was detected in GC. BCA-1 was not detected in tissues lacking lymphoid follicles. Notably, BCA-1 was detected predominantly in follicular dendritic cells in GC. CD20-positive B cells were aggregated in regions of BCA-1 expression, but not T cells or macrophages. These data suggest that BCA-1 produced by follicular dendritic cells may attract B cells and contribute to the formation of GC-like structures in chronic arthritis.

Synovial stromal cells from rheumatoid arthritis patients attract monocytes by producing MCP-1 and IL-8

Macrophages that accumulate in the synovium of rheumatoid arthritis patients play an important role in the pathogenesis of this inflammatory disease. However, the mechanism by which macrophages are attracted into the inflamed synovium and accumulate there has not been completely delineated. The results of this study show that rheumatoid arthritis synovial stromal cells produce the chemokines monocyte chemotactic protein-1 and IL-8, and these have the capacity to attract peripheral monocytes. These results suggest that one of the mechanisms by which macrophages accumulate in the inflamed synovium is by responding to the chemokines produced locally.

Rheumatoid Arthritis Synovial Stromal Cells Inhibit Apoptosis and Up-Regulate Bcl-xL Expression by B Cells in a CD49/CD29-CD106-Dependent Mechanism

Inflammatory sites, such as rheumatoid arthritis (RA) synovial tissue, contain large numbers of activated B cells and plasma cells. However, the mechanisms maintaining B cell viability and promoting their differentiation are not known, but interactions with stromal cells may play a role. To examine this, purified human peripheral B cells were cultured with a stromal cell line (SCL) derived from RA synovial tissue, and the effects on apoptosis and expression of Bcl-2-related proteins were analyzed. As a control, B cells were also cultured with SCL from osteoarthritis synovium or skin fibroblasts. B cells cultured with medium alone underwent spontaneous apoptosis. However, B cells cultured with RA SCL cells exhibited less apoptosis and greater viability. Although SCL from osteoarthritis synovium and skin fibroblasts also rescued B cells from apoptosis, they were less effective than RA SCL. B cell expression of Bcl-xL was markedly increased by RA SCL in a contact-dependent manner, whereas B cell expression of Bcl-2 was unaffected. Protection of B cells from apoptosis and up-regulation of Bcl-xL by RA SCL were both blocked by mAbs to CD106 (VCAM-1), but not CD54 (ICAM-1). Furthermore, cross-linking of CD49d/CD29 (very late Ag-4) on the surface of B cells rescued them from apoptosis and up-regulated Bcl-xL expression. These results indicate that SCL derived from RA synovial tissue play a role in promoting B cell survival by inducing Bcl-xL expression and blocking B cell apoptosis in a CD49d/CD29-CD106-dependent manner.

Establishment and characterization of nurse cell-like stromal cell lines from synovial tissues of patients with rheumatoid arthritis

OBJECTIVE To investigate the features of synovial stromal cells established from patients with rheumatoid arthritis (RA), and to define these cells as nurse cells. METHODS Synovial nurse-like stromal cell lines (RA-SNCs) were established from patients with RA. These cell lines were examined for morphology, pseudoemperipolesis activity, cell surface markers, and cytokine production. The interaction between these RA-SNCs and a synovial tissue B cell clone was also examined. RESULTS RA-SNCs had nurse cell activity. They spontaneously produced interleukin-6 (IL-6), IL-8, granulocyte colony-stimulating factor, and granulocyte-macrophage colony-stimulating factor. Furthermore, they produced IL-1beta and tumor necrosis factor alpha and expressed higher levels of the other cytokines after coculture with the B cell clone. Proliferation and Ig production by the B cell clone were dependent on direct contact with RA-SNCs. CONCLUSION These results indicate that the RA-SNCs were nurse cells. The findings suggest that RA-SNCs may play an important role in the pathogenesis of RA by producing large amounts of cytokines and maintaining infiltrating lymphocytes.

Rapid decalcification using microwaves for in situ hybridization in skeletal tissues.

In situ hybridization histochemistry is the sole tool available for detecting the localization and expression of specific RNA on histological sections under various in vivo conditions. For this paper, we examined the effect of microwave exposure on the time needed for decalcification of skeletal tissues and on the preservation of sensitivity for hybridization signals. Our data show that the use of microwave decalcification reduces the decalcification period while preserving intense hybridization signals for mouse alpha1 chain of procollagen type I mRNA in osteogenic cells in bone. The use of microwave treatment to decalcify skeletal tissues may prevent delay in obtaining experimental results or the loss of signals during in situ hybridization.

Bone marrow CD34+ progenitor cells from rheumatoid arthritis patients support spontaneous transformation of peripheral blood B cells from healthy individuals.

Abstract We show that bone marrow (BM) CD34+ progenitor cells from rheumatoid arthritis (RA) patients have the capacity to support spontaneous transformation of peripheral blood B cells. CD34+ cells purified from BM blood from eight RA patients and eight osteoarthritis (OA) patients were expanded with granulocyte/macrophage colony stimulating factor (GM-CSF) for 4–6 weeks. GM-CSF-stimulated BM CD34+ cells from three of eight RA patients, but none from seven OA patients, gave rise to spontaneous transformation of highly purified B cells of Epstein-Barr virus (EBV)- seronegative healthy donors. GM-CSF-stimulated BM CD34+ cells from four of six RA patients and from one of four OA patients also supported the spontaneous transformation of peripheral blood B cells from EBV-seropositive healthy donors. All the transformed B cell lines were positive for EBV-DNA as determined by PCR. Neither GM-CSF-stimulated BM CD34+ cells alone nor highly purified B cells alone gave rise to spontaneously transformed B cell lines. These results suggest that the capacity of BM CD34+ cells to support survival of B cells might contribute to the pathogenesis of RA by sustaining abnormal B cell responses.