Matrix Stiffness Directs Early Injury and Ketogenesis Programs to Prime Kidney Repair

KEY POINTS: We mapped dynamic extracellular matrix remodeling in AKI and identified microfibrillar-associated protein 2 (Mfap2) as a key repair mediator. Mfap2 drove mechanometabolic signaling through a large tumor suppressor kinase 1-mediated noncanonical Hippo pathway. The Mfap2-estrogen receptor 2-3-hydroxy-3-methylglutaryl-CoA synthase 2 circuit may be a druggable node for mitigating AKI. BACKGROUND: Although traditionally considered a tubule-centric disorder, AKI is increasingly recognized as involving early and active participation of fibroblasts and pericytes, the primary producer of extracellular matrix (ECM). These cells are rapidly mobilized to injury sites to support repair. Therefore, successful recovery from AKI requires not only cellular regeneration but also a finely tuned ECM, which ensures structural support and transmits essential mechanical cues. Despite its importance, the mechanistic basis by which the ECM regulates AKI repair remains incompletely understood. METHODS: We combined genetic and pharmacologic AKI animal models with tissue engineering approaches, data-independent acquisition-based global and phosphoproteomics, and spatial transcriptomics to profile the ECM proteome landscape of decellularized kidney matrix scaffolds after injury, uncover mechanometabolic pathways driving repair, and evaluate potential therapeutic strategies. RESULTS: We generated a comprehensive proteomic map of the AKI kidney matrix scaffold and highlighted microfibrillar-associated protein 2 (Mfap2) as a key core matrisome component primarily derived from fibroblasts and pericytes. Mfap2 loss disrupted kidney architecture and metabolic homeostasis, aggravating AKI severity. Global proteomics revealed that Mfap2 deficiency downregulated tubular 3-hydroxy-3-methylglutaryl-CoA synthase 2 (Hmgcs2) through estrogen receptor 2 (Esr2)-mediated transcriptional repression and increased protein succinylation. Phosphoproteomic and spatial transcriptomic analysis showed that Mfap2 loss altered mechanotransduction, leading to mitogen-activated protein kinases hyperactivation and upregulation of large tumor suppressor kinase 1 in tubular cells, without affecting integrin receptor activity. Although large tumor suppressor kinase 1 is a key Hippo pathway kinase, its activation suppressed Esr2 transcription independently of the canonical yes-associated protein/transcriptional coactivator with PDZ-binding motif effectors and without affecting Esr2 degradation. Therapeutically, Esr2 agonist restored Hmgcs2 levels and improved kidney function in Mfap2 -deficient models. CONCLUSIONS: Mfap2, a fibroblast/pericyte-derived core matrisome component, preserved kidney architecture and supported tubular ketogenesis by regulating Hmgcs2 via Esr2 in the AKI microenvironment.