SMAD3 and osteoporosis: Psoralen accelerates the osteogenic differentiation of hBMSCs by activating the TGF-β/Smad3 pathway. Psoralen alleviates bone injury through AKT-mediated upregulation of GSK-3β and NRF2. Isopsoralen regulates PPAR-γ/Wnt to inhibit oxidative stress in osteoporosis