Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 63 4 2025 11 17 231 236 Farhad Nazarinasi Department of Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Siavash Gerayeshnejad Department of Biochemistry, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Nasrin Dashti Department of Laboratory Science, School of Allied Medical Sciences, Tehran University of Medical Sciences, Tehran, Iran. Khosrow Rahbar Department of Nephrology and Urology, Mehrad Hospital, Tehran, Iran. 2025 05 24 2025 08 27 Chronic kidney disease (CKD) is characterized by systemic inflammation and the accumulation of uremic toxins such as indoxyl sulfate (IS), which induces fibrogenic signaling via transforming growth factor-beta 1 (TGF-β1). Forty CKD patients and ten healthy controls were enrolled. IS was measured by HPLC, TGF-β1 protein by ELISA, and TGF-β1 mRNA by RT-qPCR in PBMCs. IS and TGF-β1 mRNA levels increased significantly with CKD stage, particularly in stages 3 and 4. TGF-β1 mRNA correlated with IS levels (R=0.4, P<0.01), while TGF-β1 protein levels were associated with platelet count (R=0.817, P<0.001). TGF-β1 mRNA in PBMCs may serve as an early biomarker of CKD-related fibrosis. IS is a key uremic toxin influencing fibrogenic gene expression. https://acta.tums.ac.ir/index.php/acta/article/view/11674 https://acta.tums.ac.ir/index.php/acta/article/download/11674/5975