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Chronic kidney disease (CKD) is caused by dysfunctional kidneys, which result in complications like cardiovascular diseases. Chronic kidney disease‐induced pathophysiological conditions decrease efficacy of autologous mesenchymal stem/stromal cell (MSC)‐based therapy by reducing MSC functionality. To enhance therapeutic potential in patients with CKD, we isolated exosomes derived from melatonin‐treated healthy MSCs (MT exosomes) and assessed the biological functions of MT exosome–treated MSCs isolated from patients with CKD (CKD‐MSCs). Treatment with melatonin increased the expression of cellular prion protein (PrPC) in exosomes isolated from MSCs through the upregulation of miR‐4516. Treatment with MT exosomes protected mitochondrial function, cellular senescence, and proliferative potential of CKD‐MSCs. MT exosomes significantly increased the level of angiogenesis‐associated proteins in CKD‐MSCs. In a murine hindlimb ischemia model with CKD, MT exosome–treated CKD‐MSCs improved functional recovery and vessel repair. These findings elucidate the regenerative potential of MT exosome–treated CKD‐MSCs via the miR‐4516‐PrPC signaling axis. This study suggests that the treatment of CKD‐MSCs with MT exosomes might be a powerful strategy for developing autologous MSC‐based therapeutics for patients with CKD. Furthermore, miR‐4516 and PrPC could be key molecules for enhancing the regenerative potential of MSCs in ischemic diseases.

Mesenchymal stem cells (MSCs) are a popular cell source for stem cell‐based therapy. However, continuous ex vivo expansion to acquire large amounts of MSCs for clinical study induces replicative senescence, causing decreased therapeutic efficacy in MSCs. To address this issue, we investigated the effect of melatonin on replicative senescence in MSCs. In senescent MSCs (late passage), replicative senescence decreased mitophagy by inhibiting mitofission, resulting in the augmentation of mitochondrial dysfunction. Treatment with melatonin rescued replicative senescence by enhancing mitophagy and mitochondrial function through upregulation of heat shock 70 kDa protein 1L (HSPA1L). More specifically, we found that melatonin‐induced HSPA1L binds to cellular prion protein (PrPC), resulting in the recruitment of PrPC into the mitochondria. The HSPA1L‐PrPC complex then binds to COX4IA, which is a mitochondrial complex IV protein, leading to an increase in mitochondrial membrane potential and anti‐oxidant enzyme activity. These protective effects were blocked by knockdown of HSPA1L. In a murine hindlimb ischemia model, melatonin‐treated senescent MSCs enhanced functional recovery by increasing blood flow perfusion, limb salvage, and neovascularization. This study, for the first time, suggests that melatonin protects MSCs against replicative senescence during ex vivo expansion for clinical application via mitochondrial quality control.

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