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Cytokine blockade reduces myeloid expansion in RA
slight but statistical increase in immature granulocytes in anakinra-treated mice, perhaps reflecting slowed differen- tiation of these cells into mature granulocytes (Figure 6D, E). While the numbers of common lymphoid progenitors were not restored, anakinra treatment modestly reduced GMP and MPP3 expansion in CIA mice to a point below statistical significance relative to controls, suggesting reduced activation of myeloid differentiation pathways (Figure 6F-H). On the other hand, HSCLT and MPP1 num- bers were unchanged in all conditions (Figure 6I). Altogether, these data indicate that pro-inflammatory cytokine blockade can at least partially alleviate myeloid expansion and neutrophilia associated with CIA.
Cytokine blockade reverses inflammation-driven gene programs in hematopoietic stem cells from mice with collagen-induced arthritis
Given the impact of anakinra treatment on hematopoiesis, we next assessed the effect of anakinra on cell cycle activity in HSC, MPP and MyPro in CIA mice. We found their cell cycle distribution remained unchanged (Figure 7A-C), indicating that anakinra treatment does not alter cell cycle distribution in these populations. Nonetheless, anakinra treatment partially normalized expression of Ccnd1 and almost completely normalized expression of the cell cycle inhibitors Cdkn1b, Cdkn2c and Rb1 (Figure 7D). Strikingly, anakinra also significantly
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Figure 6. Cytokine blockade reduces myeloid expansion in mice with collagen-induced arthritis. (A) Induction of collagen-induced arthritis (CIA) and anakinra (Ana) treatment strategy in B10.RIII mice. (B) Representative images showing swelling and anklyosis in the hind paws of mice 17 days after disease induction (top left, CIA mice not treated with Ana; bottom left, CIA mice treated with Ana) and impact of Ana treatment on arthritis score (right) (n=9 per group). (C) Peripheral blood neu- trophil count and (D-I) number of the indicated bone marrow populations expressed as number per million BM cells of control, CIA and CIA+Ana mice (n=9 per group). The data were compiled from two independent experiments. *P<0.05; **P<0.01 ***P<0.001, as determined by one-way analysis of variance or the Mann-Whitney U-test. CFA: complete Freund adjuvant; Col: collagen; Ctrl: control; PB: peripheral blood; Gr: mature granulocytes; Pre Gr: immature granulocytes; Mon: monocytes, GMP: granulocyte-macrophage progenitors, CLP; common lymphoid progenitors; MPP: multipotent progenitors.
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