On Friday, May 2, 2025 Alexander Keeble successfully defended his dissertation and earned his doctoral degree in physiology. Congratulations, Dr. Keeble!
FOXO1-Driven Myonuclear Pathology in Chronic Kidney Disease Persists After Kidney Transplantation
Frailty in patients with Chronic Kidney Disease (CKD) greatly exacerbates disease comorbidities and increases probability of death. Past work from our laboratory and others suggests molecular alterations in skeletal muscle physiology underly frailty and poor intervention response in this patient population. These deficits in skeletal muscle contractile and metabolic function persist after dialysis treatment and predict poor outcomes following kidney transplantation. Even with successful transplant, frailty persistence is variable and hinders recovery. This study aims to identify molecular drivers of muscle pathology in patients with late-stage CKD before and after kidney transplantation.
Single-nucleus RNA-sequencing (sn-RNAseq) was conducted on skeletal muscle biopsies from age- and sex-matched cohorts including healthy participants(4), patients with late-stage CKD(6), and patients 6 months post-transplant(4). Muscle biopsies were dounce-homogenized and nuclei isolated via sequential filtration prior to loading onto a 10x chromium controller for barcode labelling and single nucleus RNA-sequencing (sn-RNAseq). Sequencing output files were filtered and analyzed using Seurat v5. Primary myogenic progenitor cells (MPCs) were isolated from a subset of participants, and myogenic capacity was assessed using myotube differentiation assays, immunohistochemistry, and western blotting. Muscle fiber size and type were analyzed immunohistochemically on biopsy sections.
sn-RNAseq revealed significant upregulation of the metabolic regulator FOXO1 in myonuclei from CKD patients, both pre- and post-transplant. This was coupled with increased PDK4 expression, and these transcriptomic changes correlated with a switch from oxidative to glycolytic myofibers in CKD patients, which was exacerbated post-transplant. Moreover, MPCs isolated from CKD patients exhibited attenuated myogenesis, driven by FOXO1.
Our findings implicate FOXO1 as a central driver of skeletal muscle pathology in CKD, which persists despite kidney transplantation. The observed metabolic inflexibility may be compounded by the use of calcineurin inhibitors as post-transplant immunosuppressants. Targeting FOXO1 and exploring alternative immunosuppressive agents could restore metabolic flexibility, promote muscle recovery, and improve patient outcomes.