[ ABSTRACT ] AIM: To investigate the effect of catalpol on the activity of osteoblasts ( OB ) and osteoclasts ( OC) , and OB estrogen receptor ( ER) α/βmRNA expression in the OB-OC co-culture system.METHODS: OB and OC were isolated from the SD rats of 1 and 5 days old.In the OB-OC co-culture system, different concentrations of catalpol including low dosage (0.05 , 0.1, 0.5 and 1 mg/L), middle dosage (2, 5 and 10 mg/L), and high dosage (20, 50 and 100 mg/L) were added into the culture medium to detect the changes of OB proliferation by MTT assay.The catalpol at maximal dosage was added to OB section to detect the alkaline phosphatase ( ALP) activity of OB by pNPP method.The mRNA expression of ERα/βin the OB treated with catalpol in the co-culture system was detected by RT-PCR.The catalpol at maximal dosage was added to OC group to detect the activity of OC by microscopy and tartrate-resistantacid phosphatase ( TRAP) activity detection.RESULTS:In 0.05~2 mg/L catalpol groups, the proliferation of OB was significantly in-creased as compared with control group in the co-culture system, and it reached the maximum value when catalpol was at 0.05 mg/L, while in 5~100 mg/L catalpol groups, the proliferation of OB was not increased.The ALP activity of OB in 0.05 mg/L catalpol group was higher than that in control group.The catalpal at 0.05 mg/L promoted the mRNA expression of ERβin OB in the co-culture system, but did not increase the mRNA expression of ERαas compared with control group. Catalpol at 0.05 mg/L obviously inhibited the bone resorption and the TRAP activity in OC.CONCLUSION: Catalpol stimulates the proliferation and activity of OB, inhibits the bone resorption and activity of OC, and increases the mRNA ex-pression of ERβin OB in the OB-OC co-culture system, suggesting that high mRNA expression of ERβmay be the regula-tory pathway of catalpol in response to bone metabolism.

OBJECTIVE:To study the effect of catalpol on the activity and apoptosis of osteoclasts (OC) in the osteoblasts (OB)-OC co-culture system and its mechanism. METHODS:OB and OC were isolated respectively from the SD rats of 1-3 days and 5-7 days old to establish OB-OC co-culture system. After treated with 0(blank control),0.05,0.5,5,50 and 100 mg/L catal-pol for 48,72 and 96 h,the number of bone absorption lacuna for OC was observed by inverted microscope to reflect OC activity. After treated with 0(blank control)and 0.05 mg/L catalpol for 48,72 and 96 h,the activity of tartrate resistant acid phosphatase (TRACP)in OC was detected,and the apoptosis rate of OC was calculated. After treated with 0(blank control)and 0.05 mg/L ca-talpol,mRNA expression of osteoprotegerin(OPG)in OB was detected. RESULTS:In OB-OC co-culture system,the number of bone absorption lacuna in 0.05-50 mg/L catalpol groups was significantly lower than blank control group(P<0.01),indicating ca-talpol could inhibit OC activity,especially 0.05 mg/L catapol. Compared with blank control,0.05 mg/L catapol lowered the activity of TRACP but increased the apoptosis rate of OC(P<0.05);mRNA expression of OPG was up-regulated in OB(P<0.01). CON-CLUSIONS:In OB-OC co-culture system,catalpol can inhibit the activity of OC and induce the apoptosis of OC,and its mecha-nism may be associated with the mRNA expression up-regulation of OPG in OB.