Umbilical cord-derived mesenchymal stem cells restore renal homeostasis in Alport Syndrome: Mechanistic insights and clinical translation

• Identifies extracellular vesicles (EVs) as the primary mechanistic effectors of mesenchymal stem cell (MSC) benefits, providing a novel therapeutic paradigm for hereditary nephropathy like Alport syndrome (AS). • Reports promising preliminary results from the first-in-human clinical trial of MSC therapy in pediatric AS patients, showing a significant reduction in albuminuria with no treatment-related adverse events. • Integrates multi-omics analysis to reveal a multi-level network mechanism by which MSCs attenuate renal inflammation and fibrosis, supporting clinical translation. • First study to validate engineered exosomes enriched with miR-146a-5p as a key mechanism by which MSCs modulate macrophage polarization via extracellular vesicles, providing a mechanistic basis for developing novel therapeutic strategies for chronic nephritis, including AS. X-linked Alport syndrome (AS) is a progressive hereditary nephropathy caused by mutations in the COL4A5 gene, leading to end-stage renal disease in young adults. Current treatments are palliative with limited efficacy, highlighting a critical unmet medical need. This study aims to evaluate the therapeutic feasibility of mesenchymal stem cells (MSCs) for alleviating renal dysfunction in AS, and to investigate whether their therapeutic benefits are primarily mediated by extracellular vesicles (EVs). Our integrated translational research strategy encompassed preclinical and clinical investigations. In the Col4a5 -deficient AS mouse model, animals received intravenous MSCs or EVs. Engrafted cells and EVs were tracked in vivo. Renal function was detected by albuminuria level, and lifespan was assessed by survival time. Therapeutic outcomes were rigorously assessed by measuring albuminuria, survival time, and comprehensive histological analyses, including tissue staining for pathology, transmission electron microscopy for ultrastructure, and specific markers for inflammation and fibrosis. Building on compelling preclinical efficacy and safety data, we initiated a first-in-human, open-label clinical trial (ISRCTN62094626) in pediatric AS patients. Patients received four infusions and were follow-up for over 12 months. Safety was evaluated by recording adverse events (AEs). Efficacy was assessed by renal function parameters. To determine the molecular mechanisms, multi-omics analysis of serial bio-samples was conducted, followed by in vitro validation to confirm the role of miR-146a-5p in mediating the therapeutic benefits of MSC-based strategy. In the AS mice, MSC treatment exhibited significant reno-protective potentials, markedly reducing albuminuria ( p < 0.001), and extended lifespan (37.7 ± 2.8 weeks vs 28.8 ± 4.0 weeks, p < 0.001), along with alleviated renal inflammatory infiltration and fibrosis ( p < 0.01), which were closely associated with macrophage modulation. Crucially, EVs recapitulated these therapeutic benefits, indicating EVs as primary mechanistic effectors. The subsequent clinical trial yielded promising preliminary results. The first pediatric patient exhibited a significant downward trend in albuminuria (Log-rank test p < 0.0001) with no treatment-related AEs throughout the 12-month follow-up. Multi-omics profiling revealed that MSCs likely attenuate pathology through a multi-level network targeting inflammation and fibrosis. Furthermore, in vitro studies confirmed the critical role of EV-enriched miR-146a-5p in modulating macrophage polarization, showing significant inhibition of IL-1β, TNF-α, and NF-κB ( p < 0.05). This proof-of-concept study provides novel evidence bridging robust preclinical findings with initial human data, underscoring the therapeutic feasibility of MSC-based therapy for AS, with mechanistic studies revealing that MSC-EV-enriched miR-146a-5p plays a partial but critical role by modulating macrophage polarization toward an anti-inflammatory phenotype.