Macrophage- and neutrophil-dominant arthritis in human IL-1α transgenic mice
Yasuo Niki, … , Kyosuke Fujikawa, Norihiro Tada
Yasuo Niki, … , Kyosuke Fujikawa, Norihiro Tada
Published May 1, 2001
Citation Information: J Clin Invest. 2001;107(9):1127-1135. https://doi.org/10.1172/JCI11530.
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Article

Macrophage- and neutrophil-dominant arthritis in human IL-1α transgenic mice

Abstract

To study the effects of IL-1α in arthritis, we generated human IL-1α (hIL-1α). Transgenic mice expressed hIL-1α mRNA in various organs, had high serum levels of hIL-1α, and developed a severe polyarthritic phenotype at 4 weeks of age. Not only bone marrow cells but also synoviocytes from knee joints produced biologically active hIL-1α. Synovitis started 2 weeks after birth, and 8-week-old mice showed hyperplasia of the synovial lining layer, the formation of hyperplastic synovium (pannus) and, ultimately, destruction of cartilage. Hyperplasia of the synovial lining was due to the accumulation of macrophage-like cells expressing F4/80 molecules. hIL-1α was widely distributed in macrophage- and fibroblast-like cells of the synovial lining cells, as well as synovial fluid monocytes. T and B cells were rare in the synovial fluid, and analysis of marker expression suggests that synoviocytes were directly histolytic and did not act as antigen-presenting cells. In the joints of these mice, we found elevated levels of cells of the monocyte/macrophage and granulocyte lineages and of polymorphonuclear neutrophils (PMNs), most of which expressed Gr-1, indicating that they were mature, tissue-degrading PMNs. Cultured synoviocytes and PMNs from these animals overexpress GM-CSF, suggesting that the hematopoietic changes induced by IL-1 and the consequent PMN activation and joint destruction are mediated by this cytokine.

Authors

Yasuo Niki, Harumoto Yamada, Shuhji Seki, Toshiyuki Kikuchi, Hironari Takaishi, Yoshiaki Toyama, Kyosuke Fujikawa, Norihiro Tada

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Figure 3

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(a) Northern blot analysis of hIL-1α mRNA from various tissues. Total RN...
(a) Northern blot analysis of hIL-1α mRNA from various tissues. Total RNA preparations from the knee joint, lumbar spine, brain, skeletal muscle, BM, spleen, liver, kidney, thymus, testis, and skin were analyzed. RNA (10 μg) was hybridized to an hIL-1α cDNA probe (upper panel). A mouse β-actin probe was used to control for qualitative and quantitative differences between the RNA preparations (lower panel). The results of a representative assay are shown. (b) SDS-PAGE and autoradiography of transgene-derived hIL-1α. Primary cultured synoviocytes and BM macrophages were pulsed with [35S]methionine/cysteine as outlined in Methods. After 5 hours, the cells were extensively washed and chased with cold media, for 2 hours for hIL-1α in cell lysates and for 12 hours for hIL-1α in culture supernatants. The cell lysates and supernatants were analyzed for radiolabeled hIL-1α by immunoprecipitation with anti–hIL-1α Ab. The immunoprecipitates were then subjected to SDS-PAGE and autoradiography. Two bands for high molecular weight hIL-1α and a band for low molecular weight hIL-1α were detected in both synoviocytes and BM macrophages. The specificity of the band was confirmed by a competition analysis in which the Ab was preblocked with recombinant hIL-1α (left lane). (c) Bioassay for transgene-derived hIL-1α. The culture supernatants were obtained from the synoviocytes or BM macrophages 48 hours after inoculation. D10 cells were cultured for 24 hours with or without a 25% vol/vol final concentration of the supernatants in culture wells and pulsed with [3H]TdR for the final 4 hours of incubation. [3H]TdR incorporation by the D10 cells was determined. The results are expressed as the mean ± SEM (n = 4). The specificity of IL-1 activity was confirmed by neutralizing with isotype-matched control Ig or anti–hIL-1α Ab or anti-mouse IL-1α Ab.