| Objective To investigate the therapeutic effect and molecular mechanism of Rehmannia glutinosa extract on ovariectomized (OVX)-induced osteoporosis (OP) in a rat model. Methods The OVX-induced OP rat model was established. Thirty-two SD rats were randomly divided into 4 groups, Control group, Sham group, OVX group, and OVX+Rehmannia glutinosa extract group (OVX+RG extract group), with 8 rats in each group. In vitro bone marrow mesenchymal stem cells (BMSCs) were grouped into group-1: Control group, OB-induction+Vehicle group, and OB-induction+RG extract group, and group-2: Control group, OB-induction+Vehicle group, OB-induction+RG extract+Adv-DAPK1 OE group, and OB-induction+RG extract+Adv-vector group. Micro-CT was used to determine the trabecular microstructural parameters of the right hind limb femurs of rats. The absorption of trabecular bone by osteoclasts was observed with HE staining and histological analysis. qPCR was used to determine the Runx2 and ALP mRNA expressions in cell group-1 on the end of 21 days of induction of BMSCs differentiation into osteoblasts. Western blotting was used to determine the Runx2 and ALP protein expressions in cell group-1 and the DAPK1 and apoptosis-related protein factors Bax, Bcl-2, Fas, and Fas L protein expressions in cell group-1 and -2. Results Compared to those in Sham group, the values of BV/TV, Tb.Num (1/mm), and Conn.dens (1/mm) of the femurs in OVX group decreased, while the values of Tb.SP (mm), SMI, and DA increased (P<0.05). There was no significant difference in Tb.Th (mm) value among the groups (P>0.05). The femurs showed a large area of osteoclast absorption of bone, and the BMD (mg/cm2) value decreased (P<0.05). Compared to OVX group, OVX+RG extract group partially reversed the above indicators (P<0.05). Compared to those in Control group, the relative expression levels of Runx2 mRNA, ALP mRNA, Runx2, and ALP in OB-induction+Vehicle groups increased (P<0.05). Compared to those in OB-induction+Vehicle group, the relative expression levels of the above indicators in OB-induction+RG extract group increased (P<0.05). Compared to those in Control group, the relative expression levels of DAPK1 and apoptosis-related protein factors Bax, Fas, and Fas L in OB-induction+Vehicle groups increased (P<0.05), while Bcl-2 decreased (P<0.05). Compared to those in OB-induction+Vehicle group, the relative expression levels of DAPK1, Bax, Fas, and Fas L in OB-induction+RG extract group decreased (P<0.05), while Bcl-2 increased (P<0.05). The relative expression levels of DAPK1, Bax, Fas, and Fas L increased in OB-induction+RG extract+Adv-DAPK1 OE groups (P<0.05), while Bcl-2 decreased (P<0.05). Compared to those in OB-induction+RG extract+Adv-vector group, the relative expression levels of DAPK1, Bax, Fas, and Fas L in OB-induction+RG extract+Adv-DAPK1 OE group increased (P<0.05), while Bcl-2 decreased (P<0.05). Conclusion Rehmannia glutinosa extract inhibits the apoptosis of BMSCs by DAPK1 and promotes the differentiation of BMSCs into osteogenesis. |