Plant-Derived Bioactive Ingredients for Osteoporosis and Bone Regeneration: Mechanisms, Pharmacology, and Delivery Strategies.

Icariin (ICA), a prenylated flavonoid glycoside from Epimedium (Yin Yang Huo), exhibits multi-organ pharmacological effects and has emerged as a promising candidate for osteoporosis therapy and bone tissue regeneration because of its capacity to modulate diverse osteogenic, anti-inflammatory, and angiogenic signaling pathways. Preclinical studies in osteoporotic models suggest that ICA improves trabecular microarchitecture and increases bone mineral density. Mechanistically, ICA modulates bone remodeling bidirectionally: it promotes osteoblast differentiation and extracellular matrix mineralization via activation of pro-osteogenic pathways, including Wnt/β-catenin and PI3K/Akt signaling, while simultaneously inhibiting osteoclastogenesis and bone resorption by suppressing RANKL-mediated NF-κB activation, thus reestablishing remodeling equilibrium. Despite these benefits, clinical advancement is hindered by the suboptimal oral bioavailability of ICA, stemming from poor intestinal absorption and extensive first-pass metabolism. To address this, innovative delivery systems have been engineered to enhance localized bioavailability and sustain therapeutic efficacy, such as hydrogel depots, nanoparticle formulations, and 3D-printed scaffolds enabling precise, controlled release. In bone tissue engineering applications, ICA-incorporated biomaterials-either standalone or in combination with osteogenic factors or exosomes-foster a regenerative niche by mitigating inflammation and oxidative stress, while synergistically promoting osteogenesis and angiogenesis, thereby expediting bone defect healing and osseointegration. Overall, these mechanistic elucidations and delivery advancements underscore ICA's potential as a translational candidate for osteoporosis treatment and bone regenerative therapies. This review aims to critically and systematically synthesize current evidence on ICA-mediated bone repair and regeneration, with a particular emphasis on the molecular regulation of osteogenic signaling, the restoration of bone-remodeling homeostasis, and delivery-system-enabled strategies that may facilitate translational application.