Objective:To investigate the effect of HuoguⅡFormula(活骨Ⅱ方) with medicinal guide Radix Achyranthis Bidentatae(Ach) on bone marrow stem cells(BMSCs) homing to necrosis area after osteonecrosis of the femoral head(ONFH) frozen by liquid nitrogen in rabbit as well as to explore the mechanism of prevention and treatment for ONFH.Methods:The animal model of ONFH was established by liquid nitrogen frozen on the rabbit left hind leg.Forty-eight Japanese White rabbits were randomly assigned to sham-operated group,model group, HuoguⅡgroup,and HuoguⅡplus Ach group,with 12 rabbits in each.During the course of ONFH animal model establishment,all rabbits were subcutaneously injected with recombinant human granulocyte colony-stimulating factor[rhG-CSF,30μg/(kg·day) for continuous 7 days].Meanwhile,normal saline and decoction of the two formulae were administrated by gavage,respectively.White blood cells(WBC) were counted in peripheral blood before and after injection of rhG-CSF.Materials were drawn on the 2nd and 4th weeks after model built;bone glutamine protein(BGP) and bone morphogenetic protein 2(BMP2) levels in serum were tested.Histopathologic changes were observed by hematoxylin and eosin(HE) staining.BMP2 mRNA levels were detected with in situ hybridization(ISH) staining.5-Bromo-2’-deoxyuridine(BrdU) and stromal cell derived factor 1(SDF-1) were measured by immunohistochemical assay in femoral head of the left hind leg.Results:Compared with the shamoperated group,the ratio of empty lacuna,serum BGP,and SDF-1 level in the model group increased significantly, and BMP2 in both serum and femoral head decreased significantly.However,in comparison with the model group, the empty lacuna ratio of HuoguⅡgroup and HuoguⅡplus Ach group decreased obviously in addition to the levels of serum BGP and BMP2,and the expressions of BMP2 mRNA,BrdU,and SDF-1 increased significantly. Above changes were particularly obvious in HuoguⅡplus Ach group.BGP and SDF-1 on the 2nd week and empty lacuna rate and serum BMP2 level on the 4th week in HuoguⅡgroup significantly exceeded their counterparts.On the 2nd week,only in Huogu U plus Ach group that the BrdU counting rose significantly.On the 4th week,empty lacuna rate and serum BMP2 level in HuoguⅡplus Ach group exceeded those in HuoguⅡgroup distinctively. Conclusions:To a certain extent,the medicinal guide Ach improves the preventive and therapeutic effects of HuoguⅡFormula on experimental ONFH model.The possible mechanism of this is related to its promoting effect on directional homing of BMSCs to the necrosis area. Objective: To investigate the effect of HuoguⅡFormula (medicinal guideline Radix Achyranthis Bidentatae (Ach) on bone marrow stem cells (BMSCs) homing to necrosis area after osteonecrosis of the femoral head (ONFH) frozen by liquid nitrogen in rabbit as well as to explore the mechanism of prevention and treatment for ONFH. Methods: The animal model of ONFH was established by liquid nitrogen frozen on the rabbit left hind leg. Forty-eight Japanese White rabbits were randomly assigned to sham-operated group, model group, HuoguⅡgroup, and HuoguⅡplus Ach group, with 12 rabbits in each. Each of the courses of ONFH animal model establishment, all rabbits were subcutaneously injected with recombinant human granulocyte colony-stimulating factor [rhG-CSF, 30 μg / (kg · day) for continuous 7 days]. Meanwhile, normal saline and decoction of the two formula were administered by gavage, respectively. White blood cells (WBC) were counted in peripheral blood before and after injection of rhG-CSF. Materi als were drawn on the 2nd and 4th weeks after model built; bone glutamine protein (BGP) and bone morphogenetic protein 2 (BMP2) levels in serum were tested. Histopathologic changes were observed by hematoxylin and eosin (HE) staining. BMP2 mRNA levels were detected with in situ hybridization (ISH) staining.5-Bromo-2’-deoxyuridine (BrdU) and stromal cell derived factor 1 (SDF-1) were measured by immunohistochemical assay in femoral head of the left hind leg. Results: Compared with the shamoperated group, the ratio of empty lacuna, serum BGP, and SDF-1 level in the model group increased significantly, and BMP2 in both serum and femoral head decreased significantly. HuoguⅡgroup and HuoguⅡplus Ach group decreased significantly in addition to the levels of serum BGP and BMP2, and the expressions of BMP2 mRNA, BrdU, and SDF-1 increased significantly. Above changes were particularly significant in HuoguⅡplus Ach group.BGP and SDF-1 on the 2nd week and empty lacunarate and serum BMP2 level on the 4th week in HuoguⅡgroup were significantly exceeded their counterparts.On the 2nd week, only in Huogu U plus Ach group that the BrdU counting rose significantly. On the 4th week, empty lacuna rate and serum BMP2 level in HuoguⅡplus Ach group exceeded those in HuoguⅡgroup distinctively. Conclusions: To certain extent, the medicinal guide Ach improves the preventive and therapeutic effects of HuoguⅡFormula on experimental ONFH model. The possible mechanism of this is related to its promoting effect on directional homing of BMSCs to the necrosis area.