van Houten, TrudyErmann, JoergFang, Eric2025-09-252025-09-252024https://hdl.handle.net/2144/513202024BACKGROUND: Spondyloarthritis is a family of inflammatory rheumatic conditions that primarily target the spine (“spondylitis”) and joints (“arthritis”) with genetic predisposition, environmental influences, and aberrant immune regulation at the center of disease pathogenesis. IL-17A is a cytokine produced by a variety of immune cells that plays a role in initiating and perpetuating the inflammatory response in spondyloarthritis. IL-17RC, a critical component of the receptor that responds to IL-17A is found on a diverse range of cell types including those responsible for bone remodeling, i.e., osteoblasts and osteoclasts, as well as antigen-presenting cells such as macrophages. The specific interplay that occurs between these cells remains incompletely understood. Previously in the Ermann lab, the Cre-loxP method of conditional Il17rc gene deletion was employed to determine which cells were the critical mediators of IL-17A effects on bone in a mouse spondyloarthritis model. However, no definitive evidence of Il17rc deletion in these specific cells was obtained.OBJECTIVE: This study aimed to interrogate the efficacy of Il17rc conditional deletion in osteoblasts, osteoclasts, and macrophages. In addition, Il17rc deletion in germline knockout mice as well as various target tissue was investigated. METHOD: Il17rcfl/fl.Ctsk-cre (Il17rc deletion in osteoclasts), Il17rcfl/fl.LyzM-cre (Il17rc deletion in myeloid cells, macrophages), Il17rcfl/fl.Prx1-cre (Il17rc deletion in early limb bud mesenchymal cells, osteoblasts), and Il17rc-/- (germline deletion of Il17rc) mice were generated. Cells from these mice were then cultured and subjected to DNA genotyping and IL17rc gene expression analysis. The functional impact of Il17rc gene deletion was analyzed by stimulation with IL-17A, TNF, or a combination of both cytokines (IL-17A + TNF). Gene expression changes of neutrophil-attracting chemokines (CXCL1 and CXCL2) were measured with real-time quantitative PCR. RESULTS: Genotyping results of IL17rc-/- mice demonstrated successful Il17rc deletion, but results obtained in gene expression and functional analyses were ambiguous. LyzM- cre facilitated Il17rc gene deletion in macrophages to a moderate extent, and we observed heightened chemokine gene expression in response to TNF. Cells cultured in osteoblast assays in vitro appeared to be mostly of the myeloid lineage. Finally, when examining target tissues, only the Il17rcfl/fl.Prx1-cre mouse displayed the expected pattern of Il17rc deletion, i.e., in muscle, tendon, and bone, while Il17rcfl/fl.Ctsk-cre and Il17rcfl/fl.LyzM- cre mice exhibited widespread Il17rc deletion. Overall, the results need to be considered preliminary. A high degree of variability observed within groups underscores the need for further assay optimization and larger sample sizes.en-USMedicineCre-loxPIL-17SpondyloarthritisThesis/Dissertation2025-09-24