FMO1 disrupts mitochondrial functional homeostasis through ROS-mediated mechanisms to drive chondrocyte senescence and hypertrophy

  • Free Radic Biol Med. 2026 Aug 16:252:613-624. doi: 10.1016/j.freeradbiomed.2026.04.158.
Ruohui Tang  1 ,  Debin Guo  2 ,  Shidan Li  3 ,  Shaochuan Wang  3 ,  Jin Yin  4 ,  Jing Yang  2 ,  Jingze Yang  4 ,  Jun Fei  5 ,  Zhaowen Zhou  6
Affiliations
  • 1. Department of Orthopedics, The First Hospital of Kunming, Affiliated Calmette Hospital of Kunming Medical University, Kunming, 650000, PR China. Electronic address: [email protected].
  • 2. Department of Emergency, Army Medical Center, Daping Hospital, Army Medical University, Chongqing, 400042, PR China.
  • 3. Department of Traumatology, Army Medical Center, Daping Hospital, Army Medical University, Chongqing, 400042, PR China.
  • 4. Department of Orthopedics, The First Hospital of Kunming, Affiliated Calmette Hospital of Kunming Medical University, Kunming, 650000, PR China.
  • 5. Department of Traumatology, Army Medical Center, Daping Hospital, Army Medical University, Chongqing, 400042, PR China. Electronic address: [email protected].
  • 6. Department of Orthopedics, The First Hospital of Kunming, Affiliated Calmette Hospital of Kunming Medical University, Kunming, 650000, PR China. Electronic address: [email protected].
PMID: 42105790 DOI: 10.1016/j.freeradbiomed.2026.04.158
Abstract

Objective: The induced membrane technique is a clinical strategy for managing large bone defects, which relies on endochondral ossification. However, the metabolic mechanisms regulating this process remain largely uncharacterized. We utilized scRNA-seq to analyze chondro-osseous dynamics during membrane-induced osteogenesis, with a specific focus on the role of FMO1.

Methods: Following the scRNA-seq profiling of human induced membranes, FMO1 function was examined using in vivo and in vitro models of triiodothyronine (T3)-induced chondrocyte hypertrophy. Mechanistic investigations incorporated FMO1 genetic knockdown and overexpression, pharmacological inhibition (methimazole), targeted mitochondrial functional assays, and senolytic clearance (ABT-263).

Results: FMO1, an enzyme typically associated with xenobiotic metabolism, was upregulated during chondrocyte hypertrophy. Both T3 stimulation and direct FMO1 overexpression increased intracellular and mitochondrial Reactive Oxygen Species. This localized oxidative stress altered mitochondrial homeostasis by shifting organelle dynamics toward fission, characterized by Drp1 upregulation and Mfn1/2 downregulation. This structural imbalance induced cellular senescence via the p16/p21 axis, resulting in abnormal matrix mineralization and increased expression of catabolic markers (COL10A1, MMP13). Genetic knockdown or pharmacological inhibition of FMO1, as well as the clearance of senescent cells, reduced these hypertrophic and senescent phenotypes.

Conclusions: We describe an FMO1-ROS-mitochondria axis that links metabolic oxidative stress to chondrocyte senescence. While baseline FMO1 expression occurs during physiological bone repair, its sustained activation drives pathological calcification and cartilage degeneration. Targeting this axis presents a potential biological strategy for modulating the osteogenic microenvironment and managing cartilage disorders.

Keywords
Chondrocyte degeneration; Flavin-containing monooxygenase 1; Mitochondrial functional stability, reactive oxygen species(ROS); Single-cell RNA sequencing.
Products