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33 Developing a transgenic mouse model with inducible cardiac fibroblast-selective deletion of the interleukin-1 receptor, IL1R1
  1. KE Hemmings1,
  2. SA Bageghni1,
  3. E Pinteaux2,
  4. MJ Drinkhill1,
  5. NA Turner1
  1. 1Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Clarendon Way, LS2 9JT, UK
  2. 2Faculty of Life Sciences, AV Hill Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK

Abstract

Rationale Interleukin-1a (IL-1a) released from necrotic cardiomyocytes is hypothesised to stimulate inflammatory responses in cardiac fibroblasts (CF) and contribute to inflammation post-myocardial infarction. Here we describe a murine model with tamoxifen-inducible fibroblast-specific deletion of the IL-1 receptor (IL1R1) for assessing the importance of the IL-1/CF axis in vivo.

Methods IL1R1-/- mice and IL1R1flx/flx mice, co-expressing tamoxifen-inducible Cre-recombinase under the control of a fibroblast-specific promoter (Col1a2-CreER(T)), were crossed to produce hemizygous offspring (IL1R1flx/-). Cre-positive IL1R1flx/- (experimental) and Cre-negative IL1R1flx/- (control) mice aged 2–3 weeks were injected with tamoxifen (100mg/kg, 5 days) and hearts isolated 4–8 weeks later to establish primary CF cultures. The functional effect of IL1R1 deletion was determined by measuring cytokine and MMP expression (qRT-PCR, ELISA) in response to IL-1a or TNFa.

Results Without tamoxifen administration, IL-1a responses in IL1R1flx/flx and IL1R1flx/- CF were identical despite 50% reduction of IL1R1 mRNA in IL1R1flx/- cells. IL1R1-/- CF showed no response to IL-1a. Monoallelic deletion of IL1R1 therefore had no functional impact. With tamoxifen treatment, a further 75% reduction in basal IL1R1 mRNA levels was observed in Cre-positive IL1R1flx/- CF vs. Cre-negative cells. IL-1a-induced MMP-3, MMP-9 and IL-6 mRNA was reduced by 65–75% in CF from tamoxifen-injected Cre-positive IL1R1flx/- mice vs. control. Similar results were obtained for protein secretion. TNFa responses were unaffected by IL1R1 deletion.

Conclusions We have developed a fibroblast-selective IL1R1 knockout mouse in which functional deletion of IL1R1 can be induced in ~75% of CF. The impact of this will be studied in an experimental myocardial infarction model.

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