CHI3L1 and Atrophy: Similarly, there were higher proportions of distal tubular cells (thick ascending limb and collecting duct principal cells) expressing Lcn2, macrophages expressing Ccl2, and polymorphonuclear neutrophils expressing Lcn2 and Chi3l1 (gene encoding YKL-40), and there was a lower proportion of thick ascending limb cells expressing tubular health marker Umod in the atrophy model at these time points.