Background: While current therapies for osteoporosis focus on reducing bone resorption, the development of therapies to regenerate bone may also be beneficial. Promising anabolic therapy candidates include phytoestrogens, such as daidzein, which effectively induce osteogenesis of adipose-derived stromal cells (ASCs) and bone marrow stromal cells (BMSCs). Purpose: To investigate the effects of glyceollins, structural derivatives of daidzein, on osteogenesis of ASCs and BMSCs. Study Design: Herein, the osteoinductive effects of glyceollin I and glyceollin II were assessed and compared to estradiol in ASCs and BMSCs. The mechanism by which glyceollin II induces osteogenesis was further examined. Methods: The ability of glyceollins to promote osteogenesis of ASCs and BMSCs was evaluated in adherent and scaffold cultures. Relative deposition of calcium was analyzed using Alizarin Red staining, Bichinchoninic acid Protein Assay, and Alamar Blue Assay. To further explore the mechanism by which glyceollin II exerts its osteoinductive effects, docking studies of glyceollin II, RNA isolation, cDNA synthesis, and quantitative RT-PCR (qPCR) were performed. Results: In adherent cultures, ASCs and BMSCs treated with estradiol, glyceollin I, or glyceollin II demonstrated increased calcium deposition relative to vehicle-treated cells. During evaluation on PLGA scaffolds seeded with ASCs and BMSCs, glyceollin II was the most efficacious in inducing ASC and BMSC osteogenesis compared to estradiol and glyceollin I. Dose-response analysis in ASCs and BMSCs revealed that glyceollin II has the highest potency at 10 nM in adherent cultures and 1 mu M in tissue scaffold cultures. At all doses, osteoinductive effects were attenuated by fulvestrant, suggesting that glyceollin II acts at least in part through estrogen receptor-mediated pathways to induce osteogenesis. Analysis of gene expression demonstrated that, similar to estradiol, glyceollin II induces upregulation of genes involved in osteogenic differentiation. Conclusion: The ability of glyceollin II to induce osteogenic differentiation in ASCs and BMSCs indicates that glyceollins hold the potential for the development of pharmacological interventions to improve clinical outcomes of patients with osteoporosis. (C) 2017 Elsevier GmbH. All rights reserved.