Background and Objective Rheumatoid arthritis (RA) is an immune-mediated inflammatory disease of unknown aetiology. Changes in the lymph nodes could precede those in the synovial joints. Recent studies reported the importance of lymph node stromal cells (LNSCs) in lymphoid homeostasis, peripheral tolerance and the adaptive immune response. Therefore, we characterised the functional capacities of LNSCs in human lymph nodes during health and different phases of RA.
Materials and Methods Individuals with arthralgia but without any evidence of arthritis upon physical examination who were positive for IgM rheumatoid factor and/or anti-citrullinated protein antibodies were included (n = 12; RA risk group). In addition, we included patients with early arthritis (disease duration <1 year; n = 6), RA (n = 15) and healthy controls (n = 8). All study subjects underwent ultrasound-guided inguinal lymph node biopsy. LNSCs were isolated and cultured from freshly collected lymph node needle biopsies. LNSCs originating from different culture passages were studied to investigate the effects of in vitro culture on the expression level of stromal cell associated genes, including VCAM-1, ColIVa and IL-6. In addition, we analysed the expression of Deaf1 and Aire, transcriptional regulators involved in peripheral tolerance. Functional capacities of LNSCs were studied by analysing STAT-1 and MxA mRNA induction and interleukin (IL)-6 and IL-8 production after TLR-3 triggering by PolyI:C.
Results Cells with a fibroblast-like morphology started to grow out from the stromal part of lymph node biopsies within a few weeks of culture. Passage 0 consisted of a mixture of adherent cells, resulting in a lower expression of the measured stromal genes. From passage 1 gene expression levels for VCAM-1, ColIVa and IL-6 increased and stabilised. All LNSCs cell lines expressed Deaf1 while the expression of Aire was only detected at very low levels. LNSCs were sensitive for TLR-3 ligation by PolyI:C resulting in upregulated STAT-1 and MxA, downregulated Deaf1 and high levels of IL-6 and IL-8. Chemokines CCL19 and CCL20 were only expressed after stimulation with PolyI:C. There was a high variability between donors and interim analysis showed no clear differences between LNSCs cultured from healthy individuals, RA risk or RA patients.
Conclusions We developed a culture system for human LNSCs to facilitate research on the role of the lymph node microenvironment in the pathogenesis of RA. Cultured human LNSCs express typical stromal cell markers and are responsive for TLR-3 triggering. Interestingly, the LNSCs express the transcriptional regulator Deaf1 which may indicate peripheral tissue antigen expression by LNSCs.