Megakaryocytes compensate for Kit insufficiency in murine arthritis
Pierre Cunin, … , Eric Boilard, Peter A. Nigrovic
Pierre Cunin, … , Eric Boilard, Peter A. Nigrovic
Published April 4, 2017
Citation Information: J Clin Invest. 2017;127(5):1714-1724. https://doi.org/10.1172/JCI84598.
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Research Article Immunology Inflammation

Megakaryocytes compensate for Kit insufficiency in murine arthritis

Abstract

The growth factor receptor Kit is involved in hematopoietic and nonhematopoietic development. Mice bearing Kit defects lack mast cells; however, strains bearing different Kit alleles exhibit diverse phenotypes. Herein, we investigated factors underlying differential sensitivity to IgG-mediated arthritis in 2 mast cell–deficient murine lines: KitWsh/Wsh, which develops robust arthritis, and KitW/Wv, which does not. Reciprocal bone marrow transplantation between KitW/Wv and KitWsh/Wsh mice revealed that arthritis resistance reflects a hematopoietic defect in addition to mast cell deficiency. In KitW/Wv mice, restoration of susceptibility to IgG-mediated arthritis was neutrophil independent but required IL-1 and the platelet/megakaryocyte markers NF-E2 and glycoprotein VI. In KitW/Wv mice, platelets were present in numbers similar to those in WT animals and functionally intact, and transfer of WT platelets did not restore arthritis susceptibility. These data implicated a platelet-independent role for the megakaryocyte, a Kit-dependent lineage that is selectively deficient in KitW/Wv mice. Megakaryocytes secreted IL-1 directly and as a component of circulating microparticles, which activated synovial fibroblasts in an IL-1–dependent manner. Transfer of WT but not IL-1–deficient megakaryocytes restored arthritis susceptibility to KitW/Wv mice. These findings identify functional redundancy among Kit-dependent hematopoietic lineages and establish an unanticipated capacity of megakaryocytes to mediate IL-1–driven systemic inflammatory disease.

Authors

Pierre Cunin, Loka R. Penke, Jonathan N. Thon, Paul A. Monach, Tatiana Jones, Margaret H. Chang, Mary M. Chen, Imene Melki, Steve Lacroix, Yoichiro Iwakura, Jerry Ware, Michael F. Gurish, Joseph E. Italiano, Eric Boilard, Peter A. Nigrovic

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Figure 6

MKs elaborate IL-1–containing microparticles and restore arthritis susceptibility in W/Wv mice.

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MKs elaborate IL-1–containing microparticles and restore arthritis susce...
(A) 1 × 104 MKs from B6 bone marrow were incubated 18 hours to test IL-1 production. Histograms show IL-1α and IL-1β concentration in MK lysate. n = 5. (B) Microparticle production from B6 MKs stained with green-CMFDA. Left, microparticles are gated based on size of beads (less than 1 μm). Dot plot of circulating intact platelets (red) was overlaid as a control to confirm bead sizing. Right, dot plot shows CMFDA+CD41+ events among microparticles; representative of 5 experiments. SSC, side scatter. (C) IL-1α and IL-1β concentration in B6 MK microparticle lysates. n = 4. (D) BM-derived MK (upper photos) and flushed BM cells (lower photos) are stained for CD41 (green) and IL-1α (red). DNA is visualized with Draq5 (Blue). IL-1α is detected in the nucleus of a subset of MK. Scale bars: 20 μm. n = 2 per experiment. (E) KC production by WT and Il1r1–/– FLS stimulated by MK microparticles (MPs) or supernatant from MK cultures. IL-1β and TNF-α (10 ng/ml) were used as positive controls. n = 3. (F) W/Wv mice were injected i.v. with PBS or 2 × 105 MKs. After 60 minutes, and again on day 2, mice were treated with 150 μl i.p. K/BxN serum. Left, clinical scoring on a 0–12 scale. W/Wv injected with PBS vs. MKs, P = 0.0282. Right, ankle and wrist thickness change. W/Wv injected PBS vs. MKs, P = 0.006. n = 9/group pooled from 2 experiments. *P < 0.05; **P < 0.01.