Oxidative stress and bone marrow adipocytes: Molecular mechanisms and possible implications

Redox homeostasis is crucial for maintaining cellular processes and is closely linked to human skeletal health. Prior research has demonstrated that oxidative stress is important for regulating osteoblast and osteoclast differentiation in the bone microenvironment, leading to a reduction in bone mass and skeletal degradation. The bone marrow is a complex niche containing various cell types, including bone marrow adipocytes (BMAs), which engage in dynamic interplay with osteo-associated cells through processes governed by redox equilibrium within the marrow compartment. During aging, a decrease in osteoblasts coincides with an increase in BMAs counts. Evidence suggests that oxidative stress influences the differentiation of BMAs, leading to the accumulation of bone marrow adipose tissue (BMAT) and contributing to bone remodeling imbalances. The fate of BMAs is determined by a precise molecular network that involves transcription factors, epigenetic regulators, and ncRNAs. The expansion of BMAT affects the commitment and differentiation of bone marrow-derived mesenchymal stem cells (BMSCs), resulting in poor osteoblast differentiation, enhancing osteoclast differentiation and function, and accelerating bone loss. Consequently, elucidating oxidative stress dynamics in pathological marrow states and delineating their correlation with aberrant BMAs differentiation emerges as a research imperative. This comprehensive review delineates the mechanistic interplay whereby oxidative stress within the osseous niche orchestrates BMAs differentiation, while simultaneously exploring how expanded BMAs reciprocally amplify oxidative stress levels. Furthermore, we dissect how maladaptive BMAs differentiation cascades perturb osteoblast-osteoclast equilibrium through paracrine signaling and microenvironmental reprogramming. By synthesizing these molecular insights, we aim to unravel the pathogenic nexus between BMAs-driven redox imbalance and compromised bone remodeling, ultimately proposing innovative therapeutic strategies for osteopathic disorders. The translational potential of this article: The growing interest in BMAs originates from their significant yet underexplored functions in bone metabolism and systemic energy homeostasis, establishing them as a novel and promising component for managing osteoporosis and related metabolic bone disorders. Clinically, this focus addresses two critical gaps in current osteoporotic care, which predominantly relies on anti-resorptive agents and bone-forming medications. While these conventional treatments demonstrate efficacy, they face limitations such as potential long-term safety concerns, the presence of treatment-resistant patients, and an incomplete ability to restore bone quality and mechanical strength. Targeting BMAs presents a complementary or alternative therapeutic strategy by addressing a fundamental cellular element within the bone marrow microenvironment that actively participates in bone remodeling. Mastering the regulation of BMAs enables a shift toward a more comprehensive "whole-bone" therapeutic approach, aiming not merely to increase bone mineral density but also to enhance bone quality and fracture healing, thereby fundamentally addressing the pathogenesis of skeletal fragility in aging populations and pathological conditions characterized by aberrant marrow fat accumulation.