CHI3L1 and systemic sclerosis: To investigate the role of Chi3L1 in fibrosis in vivo, we generated Chi3L1 KO mice with a C57BL/6 background and compared the fibrotic changes in wild‐type (WT) and KO mice in phosphate‐buffered saline (PBS) control (CTR) and BLM‐SSc mice, a widely recognized experimental model of SSc (Figure4A).[32, 33]