Abstract
Kidney fibrosis is the common pathological pathway in progressive chronic kidney disease (CKD), and current treatments are largely ineffective. The C-X-C chemokine receptor 4 (CXCR4) is crucial to fibrosis development. By using neural cell adhesion molecules as scaffolds with binding loops that mimic the shape of shark antibodies, fully humanized single-domain i-bodies have been developed. The first-generation i-body, AD-114, demonstrated antifibrotic effects in a mouse model of folic acid (FA)-induced renal fibrosis. The second-generation i-body, AD-214, is an Fc-fusion protein with an extended half-life, enhanced activity, and a mutated Fc domain to prevent immune activation. To investigate the renoprotective mechanisms of AD-214, RPTEC/TERT1 cells (a human proximal tubular cell line) were incubated with TGF-b1 with/without AD-214 and the supernatant was collected to measure collagen levels by Western blot. Mice with unilateral ureteral obstruction (UUO) received AD-214 intraperitoneally (i.p.) every two days for 14 days. Kidney fibrosis markers and kidney function were then analyzed. AD-214 suppressed TGF-b1-induced collagen overexpression in RPTEC/TERT1 cells. In UUO mice, AD-214 reduced extracellular matrix (ECM) deposition, restored kidney function, and limited leukocyte infiltration. In a scratch assay, AD-214 also inhibited macrophage migration. To conclude, i-body AD-214 attenuates UUO-induced kidney fibrosis by inhibiting leukocyte infiltration and macrophage migration.