Dose-dependent effects of nicotine on proliferation and differentiation of human bone marrow stromal cells and the antagonistic action of vitamin C.

A range of biological and molecular effects caused by nicotine are considered to effect bone metabolism. Vitamin C functions as a biological antioxidant. This study was to evaluate the in vitro effects of nicotine on human bone marrow stromal cells and whether Vitamin C supplementation show the antagonism action to high concentration nicotine. We used CCK-8, alkaline phosphatase (ALP) activity assay, Von Kossa staining, real-time polymerase chain reaction and Western Blot to evaluate the proliferation and osteogenic differentiation. The results indicated that the proliferation of BMSCs increased at the concentration of 50, 100 ng/ml, got inhibited at 1,000 ng/ml. When Vitamin C was added, the OD for proliferation increased. For ALP staining, we found that BMSCs treated with 50 and 100 ng/ml nicotine showed a higher activity compared with the control, and decreased at the 1,000 ng/ml. Bone morphogenetic protein-2 (BMP-2) expression and the calcium depositions decreased at 100 and 1,000 ng/ml nicotine, while the addition of Vitamin C reversed the down regulation. By real-time PCR, we detected that the mRNA expression of collagen type I (COL-I) and ALP were also increased in 50 and 100 ng/ml nicotine groups (P < 0.05), while reduced at 1,000 ng/ml (P < 0.05). When it came to osteocalcin (OCN), the changes were similar. Taken all together, it is found that nicotine has a two-phase effect on human BMSCs, showing that low level of nicotine could promote the proliferation and osteogenic differentiation while the high level display the opposite effect. Vitamin C could antagonize the inhibitory effect of higher concentration of nicotine partly.

Effect of calcium citrate on bone integration in a rabbit femur defect model.

OBJECTIVE: To explore effect of calcium citrate on bone integration in a rabbit femur defect model, and to compare the bone formation with different sizes by radiological and histological study. METHODS: Twenty-four male Japanese white rabbits were randomly divided into three groups (Group A, B, C) in this study. Under anesthesia, defects of four sizes (1.2, 1.5, 2.0 and 2.5 mm) were created in each of the rabbits. Commercially pure calcium citrate powder was placed inside the medullary compartment of the femur (Experimental), while in the contralateral femur (Control) nothing was implanted. The defects were analyzed using radiography and histological analysis by using Imagepro-Plus 6.0 software after animal was sacrificed at 4th(Group A), 6th(Group B) and 8th(Group C) weeks postoperatively. Four samples were analyzed for each size of defect and each healing period. RESULTS: The histological and the radiologic evaluation were performed after sacrification of all rabbits on postoperative 4th and 6th weeks, It showed significant difference between the experimental group and the control group when these defects were less than or equal to 2.0 mm. No statistical difference was observed when these defects were larger than 2.0 mm at all healing periods except at the 4th week. CONCLUSIONS: Calcium citrate affects the early periods of bone defects healing mechanism in Japanese white rabbits positively, especially when the defect is not too large. We suggest further studies on calcium citrate to determine the effects of various dosages, administration ways and the experimental time on the bone defects.