Human urine-derived stem cells from different donor sources ameliorate diabetic nephropathy in mice by activating autophagy and restoring mitochondrial function of podocyte.

Background: Human urine-derived stem cells (hUSCs) are a novel type of mesenchymal stem cells (MSCs) originating from the kidney, with promising potential for personalized therapies. However, it remains unclear whether hUSCs can be successfully isolated from individuals of different ages and disease states-including healthy young individuals, healthy elderly individuals, and patients with diabetic nephropathy (DN), as well as their therapeutic potential and mechanism in DN.

Methods: hUSCs were isolated from healthy young men (hUSC-HY), healthy elderly men (hUSC-HE), and male DN patients (hUSC-DN), and their biological characteristics were systematically evaluated. The therapeutic effects of early-passage (P3-P5) hUSC-HY, hUSC-HE, and hUSC-DN were assessed in DN mouse models. In vitro, the effects of conditioned medium (CM) derived from each hUSC group on apoptosis in high glucose (HG)-injured mouse podocytes (MPC5) were assessed. To explore the underlying mechanisms, autophagy activation and mitochondrial function were further analyzed in HG-injured MPC5 cells treated with or without hUSC-CM.

Results: Early-passage (P0-P5) hUSC-HY, hUSC-HE, and hUSC-DN exhibited comparable biological characteristics. However, after passage 5, hUSC-HE and hUSC-DN progressively developed senescent phenotypes. Early-passage hUSC-HY, hUSC-HE, and hUSC-DN effectively improved renal function and ameliorated tissue damage in DN mice, primarily by inhibiting HG-induced podocyte apoptosis. In vitro, CM derived from all three hUSCs types (P3-P5) significantly attenuated HG-induced apoptosis in podocytes (MPC5 cells) by the activation of autophagy through suppression of the PI3K/AKT/mTOR and ERK/mTOR signaling pathways. Additionally, hUSCs were shown to deliver functional mitochondria to injured MPC5 cells, thereby restoring mitochondrial function and further contributing to the inhibition of podocyte apoptosis.