Inhibition of FAK-Actin Pathway by Indoxyl Sulfate Suppresses Microvascular Remodeling in a Mouse Model of Chronic Kidney Disease

Objective: Chronic kidney disease (CKD) worsens outcomes of peripheral artery diseases (PADs), partly through impaired vascular regeneration and microvascular remodeling. CKD promotes the accumulation of uremic toxins, but their contributions to microvascular dysfunction remain poorly understood. This study investigated the effects of uremic toxin indoxyl sulfate (IS) on vascular smooth muscle cell (VSMC) function and microvascular remodeling in a mouse model of CKD. Methods: C57BL6/J mice were fed 0.25% adenine diet for 10 days to induce CKD. CKD mice underwent hindlimb ligation surgery. VSMC migration assays, microscopy, and Western blotting were utilized to elucidate the underlying mechanisms underlying the IS-induced impairment of vascular remodeling. Results: CKD mice exhibited significantly impaired blood flow restoration (44.7% relative blood flow) compared with controls (82.6% relative blood flow) accompanied by a reduced α-smooth muscle expression and decreased formation of smooth muscle-covered micro vessels in ischemic limbs. Wound healing and transwell migrations assays demonstrated IS significantly reduced VSMC motility. IS-exposure also disrupted actin cytoskeletal organization, impaired cell attachment, reduced cell size, and decreased focal adhesion formation. Mechanistically, IS reduced focal adhesion kinase (FAK) expression, impairing VSMC adhesion and migration. Reduced FAK signaling was associated with decreased N-WASP expression and suppression of the Arp2/3 complex, which regulates actin polymerization and cytoskeletal remodeling. These alterations suggest that IS disrupts the cellular processes required for VSMC recruitment and structural remodeling of the microvascular, potentially limiting vessel maturation and stabilization during ischemic recovery. Conclusions: IS impairs VSMC migration and cytoskeletal organization through the disruption of the FAK-N-WASP-Arp2/3 signaling axis, contributing to defective microvascular remodeling and impaired perfusion recovery in CKD-associated PAD. These findings identify uremic toxin-mediated cytoskeletal dysfunction as a potential therapeutic target for improving microvascular regeneration and vascular recovery in patients with CKD.