Pharmacological Targeting of IL17/neutrophil axis to Treat Calciphylaxis

Calciphylaxis is a rare but life-threatening disorder characterized by ectopic calcification affecting the subcutaneous tissues and blood vessels of the skin. Calciphylaxis affects individuals with end stage renal disease but increasingly recognized to occur in individuals with normal kidney function. Once diagnosed, survival rates are less than a year and yet despite the severity of the condition, the pathobiology of calciphylaxis is ill understood. Here, we create animal models of calciphylaxis that recapitulate many characteristics of the human phenotype. We demonstrate that calcific deposits in the skin are preceded by recruitment of inflammatory cells. We show that increased local inflammation of the skin, regardless of the inciting cause, in the presence of hypercalcemia and hyperphosphatemia contributes to cutaneous ectopic calcification. Using multiple models of genetically modified rodents that have deficits in immune activation of T and B cells or NK cells, we demonstrate that such immunocompromised rodents are resistant to developing cutaneous calcification. Consistent with this observation, administration of the immunosuppressive cyclophosphamide rescued calcific deposits as did T cell suppression with cyclosporine. We demonstrate IL17 is upregulated in calcific skin and neutrophils are the predominant cell types expressing IL 17 and tissue alkaline phosphatase that is necessary for ectopic calcification. Targeting IL17 with a monoclonal antibody or use of a myeloperoxidase inhibitor to blunt neutrophil activation significantly attenuated calcific deposits in vivo. Taken together, these observations provide fresh insight into the role of the immune system and the IL17/neutrophil axis in mediating ectopic calcification in rodent models of calciphylaxis. Overall design: RNA-seq was performed on skin tissues collected from wildtype Sprague-Dawley rats and immunodeficient SRG rats subjected to different treatment conditions to investigate gene expression changes related to inflammation and skin calcification. Additional groups were treated with immunosuppressive agents or antibodies. Selected samples were also used for single-cell RNA sequencing.